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Tilburg University ConceptBase.cc User Manual

1. 4 1 8 Activate and Deactivate ECA rules The attribute act ive allows the user to deactivate the rule without untelling it Possible values are TRUE and FALSE The default value is TRUE 1 e by default are ECArules active 61 4 1 9 Depth The attribute depth specifies the maximum nesting depth of ECArules ECArules may be fired by events which are produced by actions of the same or other ECArules Because this often results in an endless loop the execution of the ECArule is aborted if the current nesting depth is higher than the specified value The default of this attribute is 0 no limitation 4 1 10 User definable Error Messages If the ECArule rejects the transaction in some cases it is useful to specify an error message The value of the attribute re jectMsg is returned to the user 4 1 11 Constraints The constraints of the class ECArule ensure that the attributes mode active and depth have only single values and that the attribute ecarule has exactly one value 4 2 Examples The Telos source files of the following examples can also be found in your ConceptBase installation directory at SCB_HOME examples ECArules Further examples are in the CB Forum at http merkur informatik rwth aachen de pub bscw cgi 1747992 4 2 1 Materialization of views by active rules Materialization of views means that deduced information is stored in the object base We provide here an example
2. will enroll to the CBserver running on a host named alpha with port number 4001 and will extract just the answer to 01 x param If there are more answers to be extracted one has to employ separate scripts for each of them and execute them one after the other to save the results in separate files The server side method using the views option will determine all possible fillers x for the parameter param and automatically save the results of 01 x param in a separate file with filename x Further examples are available from the CB Forum at http merkur informatik rwth aachen de pub bscw cgi 3097259 76 Chapter 6 The ConceptBase cc Server The ConceptBase cc server offers TCP IP access to the functionality of the O Telos languages Specifically it allows to TELL or UNTELL O Telos objects and to ASK O Telos object bases The operations are called by clients for example the user interfaces described in section 8 An arbitrary number of clients can connect to a single ConceptBase server The ConceptBase cc server is started by a command line lt CB_HOME gt startCBserver sh lt params gt or on Microsoft Windows lt CB_HOME gt startCBserver bat lt params gt where lt CB_HOME gt is the installation directory of ConceptBase cc 6 1 CBserver parameters The following parameters are available for the startCBserver CBserver command d dbdir Set database dbdir to be loaded If the database does not exist it is cre
3. 140 E 1 3 Attributes IS_ATTRIBUTE_OF Returns TRUE if src has an attribute of the category att rCat which has the value dst IS_EXPLICIT_ATTRIBUTE_OF Same as before but only for explicit attributes find_all_explicit_attribute_values Lists all attribute values of ob jname that are explicitely defined find_iattributes Lists the attributes that go into class find_referring_objects Lists the objects that have an explicit attribute link to class find_referring_objects2 Lists the objects that have an explicit attribute link to ob jname and for which the attribute link is an instance of cat find_all_referring_objects2 Same as before but including implicit attributes find_attribute_categories Lists all the attribute categories that may be used for objname This is a lookup of all attributes of all classes of ob jname find incoming attribute categories In contrast to the previous query this query returns all attribute cate gories that go into ob jname i e attribute categories for which ob jname can be used as an attribute value find_attribute_values Lists all objects that are attribute values of ob jname in the attribute category cat find_explicit_attribute_values Same as before but only for explicit attributes E 1 4 Links between objects find_incoming_links Lists the links that go into ob jname and are instance of category Note that all types of links are returned including attributes instance of links
4. Class Project in EntityType with keyeAttr attribute pono Integer eAttr attribute budget Real end Integer in Domain end Real in Domain end String in Domain end Class WorksIn in RelationshipType with role attribute emp Employee prj Project end WorksIn emp with minmax mProjForEmp 1 end WorksIn prj with minmax mEmpForProj 1 x end 132 ConceptBase in Project with pno cb_pno 4711 end Martin in Employee with ssn martinSSN 4712 end M_CB in WorksIn with emp mIsEmp Martin prj cbIsPrj ConceptBase end Hans in Employee with ssn hans_ssn 4714 end The entity types Employee and Project participate in a binary relationship WorksIn The attributes Employee ssn and Project pno are key attributes of the respective objects D 2 2 The use of meta formulas The above model distinguishes attributes and key attributes One important constraint on key attributes is monovalence In the previous releases of ConceptBase it was possible to declare Telos attributes as instance of the attribute categories single or necessary but the constraint ensuring this property could not be formulated in a general manner because the use of variables as placeholders for Telos classes e g in an Jn Literal was prohibited To overcome this restriction meta formulas have been integrated into the system An assertion is a meta formula if it contains such a class variable The system tries to
5. Class View isA GenericQueryClass with attribute inherited_attribute Proposition partof SubView end Attributes of the category inherited_attribute are similar to retrieved attributes of query classes but they are not necessary for answer objects of the views i e an object is not required to have a filler for the inherited attribute for being in the answer set of the view The partof attribute allows the definition of complex nested views i e attribute values are not only simple object names they can also represent complex objects with attributes The following view retrieves all employees with their departments and attaches the head attribute to the departments View EmpDept isA Employee with retrieved_attribute partof dept Department with retrieved_attribute head Manager end end As the example shows the definition of a complex view is straightforward for the inner frame the same syntax is used as for the outer frames The answers of this view are represented in the same way e g John in EmpDept with dept JohnsDept Production with head ProdHead Phil end end Max in EmpDept with dept MaxsDept Research with head ResHead Mary end end To make the definition of views easier we allow some shortcuts in the view definition for the classes of attributes For example if you want all employees who work in the same departments as John you can use the term John dept instead of Dep
6. Employee salary see chapter 2 The attribute category can be selected from a listbox by clicking on the Select button next to the text field of the attribute category All attribute categories that apply to the current source of the attribute will be shown Note that the list will be empty if the source object does not yet exist in the database If you have specified the attribute category you can also select the attribute value from a listbox by clicking on the Select button next to the text field for the attribute value The listbox will show all instances of the destination of the attribute category e g all instances of Department for the category Employee dept If you select the radio button Show Attribute Instantiation then the Graph Editor will also show the instantiation link for the attribute For example if you create a new attribute for John with the 100 label JohnsDept in the attribute category Employee dept then the instantiation link between John JohnsDept and Employee dept will also be shown As the graph gets quite confusing with too many links this radio button is not selected by default Deletion of objects is also possible As this operation should not be mixed up with the removal of an object from the current view this operation is just available from the popup menu item Delete Object from Database As you might make mistakes while editing the model there is the possibility
7. end The functional expression used in the comparison can be nested See section 2 3 3 for details You can also re use the above query to form further functional expressions e g for counting the number of objects that have more than two attribute You find below all three representations for the expression COUNT ObjectWithMoreThanTwoAttributes class COUNT ObjectWithMoreThanTwoAttributes ObjectWithMoreThanTwoAttributes 2 5 4 Programmed functions If your application demands functional expressions beyond the set of predefined functions you can extend the capabilities of your ConceptBase installation by adding more functions There are two ways first you can extend the capabilities of a certain ConceptBase database or secondly you can add the new functionality to your ConceptBase system files We will discuss the first option in more details using the function sin as an example and then give some hints on how to achieve the second option A function like any builtin query class has two aspects First the ConceptBase server requires a regular Telos definition of the function declaring its name and parameters This can look like 41 Sin in Function isA Real with parameter x Real comment c computes the trigonometric function sin x end The super class Real is the range of the function i e any result is declared to be an instance of Real The parameters are listed like for any regular generic query class The com
8. in nil in lt classlist gt isa nil isa lt classlist gt with nil with lt attrdecllist gt class lt object gt lt classlist gt class lt object gt attrdecl lt attrcategorylist gt lt attrcategorylist gt gt nil lt propertylist gt gt lt propertylist2 gt gt lt propertyvalue gt gt lt selectExpB gt gt lt restriction gt gt lt labellist gt nil lt propertylist2 gt lt propertylist gt property lt label gt lt propertyvalue gt lt propertylist2 gt property lt lt object gt lt selectExpB gt enumeration lt classlist gt lt SMLfragment gt lt restriction gt lt restriction gt selectExpB selectExpB selectExpB selectExpB restriction lt label gt lt sele restriction lt label gt enume restriction lt label gt lt obje lt selectOperator gt gt dot bar lt labellist gt gt lt label gt lt label gt gt lt object gt gt lt substlist gt gt lt labellist gt lt label gt ALPHANUM LABEL NUMBER derive lt substlist gt lt selectexp gt lt singlesubst gt lt substlist gt lt singlesubst gt 121 label gt lt selectOperator gt lt select lt selectOperator gt lt object gt lt object gt lt selectOperator gt lt selectExpB gt lt object gt lt selectOperator gt lt object
9. 4001 The small window in the upper right corner is not connected to a server but a few objects have been created CB GTapriEditor File Edit Options View Current connection DSB amp PIKE cal lA E localhost4001 A_New_Object Individual QueryClass attribute a A_New_Instance retrieved_attribute Propositid computed_attribute Proposit constraint MSFOLquery i Fj localhost4001 RelationshipType Connected with localhost Figure 8 7 ConceptBase Graph Editor The windows which are connected with the server show the same model but in different representa tions This is caused by the fact that for the upper window the default grapical palette has been chosen and for the lower window a customized graphical palette specifically designed for the ER model has been selected see appendix D 2 and C Furthermore you can notice that the object QueryClass is represented by two different components In the upper view the detailed component view has been activated by a double click on the object It shows the Telos frame of the object By a double click on the title bar of this component one can switch back to the default view of this object Thus each object can be shown by a small component the default view and a large component which gives more detailed information Components are in this context specific Java objects na
10. end Parameters that don t occur as computed or retrieved attributes are interpreted as existential quantifica tions if they are not instantiated 2 3 1 Query definitions versus query calls Telling a frame that declares an instance of QueryClass as well as its sub classes GenericQuery Class and Function constitutes the definition of a query It shall be compiled internally into Datalog code not visible to the user Once defined a query can be called simply by referring to its name Hence if Q is a the name of a defined query class then Q is also an admissable query call It results in the set of all objects that fulfill the membership constraint of O ConceptBase regards these objects as derived instances of the query class Q If a query class has parameters then any of its specialized forms is also an admissable query call For example if O has two parameters p1 p2 in its defining frame then Q v1 p1 v2 p2 is the name of a class whose instances is the subset of instances of Q where the parameters p1 and p2 are substituted by the values v1 and v2 The substitution yields a simplified membership constraint that precisely defines the extension of OQ v1 p1 v2 p2 If a generic query class is called with all parameters substituted by fillers then one can omit the param eter labels Assume that the query Q has just the parameters p1 and p2 Then the expression Q v1 v2 is equivalent to Q v1 p1 v2 p2 ConceptBase uses the alphabetic or
11. how to materialize and maintain simple views Class Employee with attribute salary Integer end View EmployeeWithHighSalary isA Employee with constraint c exists i Integer this salary i and i gt 100000 end Class EmployeeWithHighSalary_Materialized end The view EmployeeWithHighSalary contains all employees who earn more than 100 000 The class EmployeeWithHighSalary_Materialized will contain the same employees This imple mented by the following ECArules ECArule EmployeeWithHighSalary_Materialized_Ins with ecarule er x Employee ON Tell In x Employee IF new In x EmployeeWithHighSalary DO Tell In x EmployeeWithHighSalary_Materialized end ECArule EmployeeWithHighSalary_Materialized_Del with ecarule er x Employee ON Untell In x Employee 62 IF In x EmployeeWithHighSalary DO Untell In x EmployeeWithHighSalary_Materialized end ecarule er x Employee y Integer ON Tell A x salary y IF new In x EmployeeWithHighSalary ECArule EmployeeWithHighSalary_Materialized_Ins_salary with DO Tell In x EmployeeWithHighSalary_Materialized end ecarule er x Employee y Integer ON Untell A x salary y IF In x EmployeeWithHighSalary ECArule EmployeeWithHighSalary_Materialized_Del_salary with DO Untell In x EmployeeWithHighSalary_Materialized end The first
12. is equivalent to this oid However the Oid pattern is also applicable to patterns not including this Examples are available from the CB Forum see http merkur informatik rwth aachen de pub bscw cgqi 2502545 The above set of patterns can be extended by user defined functions In principle any routine that can be called from the ConceptBase server can also be called in an answer format The programming interface is not documented here since this requires extensive knowledge of the ConceptBase server source code For the experienced user we provide an example in the subdirectory Examples AnswerFormat of the ConceptBase installation directory see files externalcal1l sml and externalcall swi lpi externalcall bim 1lpi for BIM Prolog variant Note that one has to create a persistent database load the model externalcall sml into it then terminate the ConceptBase server and then copy the file externalcall swi lpi or externalcall bim 1pi into the database directory see also appendix F Thereafter restart ConceptBase and call the query EmpDept 3 2 6 Calling queries in answer formats A query call within an answer format is an example of a so called external procedure The pattern as well as head and tail of an answer format may contain the call to a query possibly the same for which the answer format was defined for This allows to generate arbitrarily complex answers ASKquery Q subst1 subst2 FRAME The ar
13. results section 5 9 ConceptBase will use the specified file type when storing the query results in the file system The default value is txt The attribute is single valued though single valuedness is not enforced 56 Chapter 4 Active rules Active rules specify certain actions that have to be executed if an event occurs and a condition is fulfilled at this time Because active rules consists of an Event a Condition and an Action they are abbrivated with ECArule Events ON part of ECArules are insertions and deletions of objects Tell Untell and queries Ask The events are detected during the processing of the input frames for a Tell or Untell or Ask operation For example if you tell 2 frames at a time and the first frame contains an event for an ECArule then the ECArule is executed before the second frame is processed You can also control the sequencing of the firing of ECA rules by the so called ECAmode and by priority orderings in the set of defined ECArules The condition of the ECArule IF part is a logical expression over the database It will bind free variables occurring in the condition if any and these bindings together with the bindings of the event are passed to the action part of the ECArule The action DO part of an ECArule is evaluated for each evaluation of the IF part that has is true in the database The elements in a DO part can be Tell Untell Retell Ask and CALL actions CALL actions can call any P
14. without answers and the tracemode no virtually disables tracing The tracemode high and veryhigh are only useful for debugging the system In these two modes an unlikely fatal signal like division by zero will not directly abort the CBserver process but start a debug dialog Enter h for options to diagnose the problem in collaboration with the ConceptBase developers c cachemode turns on the query cache to allow recursive query evaluation The value cachemode is one of off transient and keep default In transient mode the cache is emptied before each transaction In keep mode the cache is emptied when the maximum number of entries in the cache is exceeded or an update has invalidated the cache Further details are explained in section 6 2 0 optmode controls the optimizer for rules constraints and queries The value opt mode is one of 0 no optimization 1 structural optimization by exploiting builtin O Telos axioms 2 optimizing join order or 3 combines 1 and 2 Default and recommended is 3 r secs automatically restarts the server after a crash The value secs specifies how many seconds to wait before restart Crashes are infrequent with the CBserver Use this option only when you want maximum accessibility of the server This option is not available on Microsoft Windows s securitylevel enables or disables the access control mechanism of ConceptBase The value 0 means that no access control is employed Any user can as
15. 1747992 It should be noted that one can also ask queries in the DO part and ELSE part of an ECArule Other than for the IF part such queries are only evaluated once 4 3 Limitations in the current implementation The current implementation of active rules in ConceptBase has several limitations 65 The dependency graph of ECA rules may contain cycles i e rule R1 executes an action which fires the rule R2 and R2 has an action which fires R1 The current algorithm for detecting cycles tests the dependency graph during compile time The cycle checker prints a warning message on the console if it has detected a possible cycle but the compilation of the rule is not aborted because it is still possible that the cycle does not occur during the execution of the rule The user must take care that endless loops are avoided The ON part of an ECArule consists of a single atomic event ConceptBase does not support complex events such as event 1 occurs after event 2 Instantiations and specializations of system classes Proposition Attribute InstanceOf are not detected in the event manager Adding those events would affect the performance Like QueryClasses ECArules can not be modified after they have been told e g change the event condition or actions The only updateable attribute of ECArule is act ive If you set this attribute to FALSE you can deactivate the rule for a certain time Deleting or setting the attribute to TRUE re
16. 26 Query evaluation strategies cocos eteri e ee ee eee 227 Datalog queres and Tul s cocos ea kk eS Be AG De a a 2 7 1 Extended query model 5 0664 50844 64 4S eee ee e Die es oos Ae eee ee doh Bes a We eh GOR ee Sw Be Hs a a N Zick O 1 cic ge 6S NAAA h OO0OVOo0o000wsou i 3 Answer Formats for Queries al BASICOS a A A A Se EPS ASS SS 3 2 Conseils in answer FONAS sii o E A ee EE eS 321 Simple expressions m Paes oir Oe ee hee Eee APS eS AZ Pr denned variables co 5G opea ap RS eR RE RS 32 3 Tterationsoverexpressions ce eee Pe eS ewe ee PA eS 324 pecial characters o o coa ke Ah ee ES BRE aa a 3 2 1 Function paterns so err essre a AA eae aw 3 2 0 Calling queries in answer formats o ss cone corpa ek GB eke ee 3 2 7 Expressions in head and tail lt os ea a ee um 3 2 8 Conditional expressions 26546 pk SEVER SERRA RE ROD 3 29 Views and path expressions coes cese ee eee ee ee ee eS 3 Parametenized answer tonne 4 lt lt 0 6 oo Madde Bae eee BS ees 34 Pile type Ot snswerformds cositas a ee eS Aa Ee RES Active rules 41 Detimtion of BCAMICS o s sc ee ea ea ee Ee ae BEE Ee ee eS ALI CABOS soc gk GR A a a Ba a al A es 41 2 BRO 2 6 e444 bebe bee eb de Gade be ea Be oe ed AAS COMOUMIONS oso ao eR Bed BR a SS SS Se BLA ACME ira A ee Ee EEG ee Ee DS POMS 5 bo AAA cet is 41 Modeotan ELA tule ss 54025 bee oe EE Yes bob ee eee b ALT ARCCURON SSMMAOS o acord AER SE ERASE ETE ES 4 1 8 Activate and Deactivate ECA
17. DIV DerivedFromMetabossQuery1 ask TelosEditor Cancel Query successful Version Now Module System 13 37 0 0s Figure 8 4 Display queries dialog If you ask a generic query class with parameter another dialog will ask you to specify the parameters For each parameter you can specify whether the value entered should be used as substitute for the parameter or as a specialization of the parameter class see section 2 3 You can select a value for the parameter from the drop down list if you have clicked on the Show Values button Note that this list might be very long Especially for the predefined queries it usually returns all objects in the database as any object can be used as a parameter for these queries 91 8 1 9 Query editor The Query Editor see figure 8 5 allows the interactive definition of queries The name of the query is entered in the upper left text field the super class in the upper right field After you have entered this information the list box Retrieved Attributes will be filled with all available attributes Now you can select the attributes you want to have in the result For selection of more than one attribute you must press the CTRL key and select the attribute with a mouse click at the same time All attributes can be deselected by the popup menu Query Editor Latest operation status Operation successful Query Name HighSalary Specialization of Ernployee Retriev
18. If a violation is detected then the whole transaction is rolled back including the updates done by ECArules 4 1 5 Priorities The attributes priority_after and priority before ensure that this ECArule is executed after or before some other ECArules if several rules can be fired at the same time There can be multiple values for each of these attributes As you may have noted one of the two attributes is redundant since r1 priority after r2 is equivalent to r2 priority before r1 Still ConceptBase provides both Furthermore ConceptBase does not automatically check the consistency of the priority declarations if r is before ra then r2 cannot be before r1 ConceptBase also does not provide for the transitivity of the priority You can however define this yourself via appropriate deductive rules 4 1 6 Mode of an ECA rule The mode of an ECArule determines the point in the transaction when the condition and the action of the ECArule are evaluated and executed Possible values are Immediate The condition is evaluated immediately after the event has been detected If it evaluates to a non empty answer the DO action is executed immediately too If the answer is empty then the ELSE actions are executed provided that the ECArule has an ELSE part ImmediateDeferred The condition is evaluated immediately after the event has been detected If it eval uates to a non empty answer the actions of the DO part are executed towards the end of
19. P a would be in the extension The matching call P x has the same arguments as P a except for certain variable positions In practice most rule sets are already statically stratified i e no violation can occur regardless of the data in the database Counter examples are in the CB Forum see http merkur informatik rwth aachen de pub bscw cgi 888832 in the models Russel sml and Win sml These examples are neither statically nor dynamically stratified Note also the example WinNim sml which uses the same query as Win sml but is dynamically stratified Even in the case of stratification violations ConceptBase will display an answer to a query The user can then decide which parts of the answer are usable In principle this decision can also be automated which is subject of future ConceptBase releases gt 15 Older releases of ConceptBase provided a prototype of a query evaluation strategy based on the magic set method We no longer support this strategy 44 2 7 Datalog queries and rules The definition of queries in ConceptBase is often complicated by the limitations of the expressiveness of the query language or by the limitations of the query optimizer to find the best solution The concept of datalog queries and rules was introduced to overcome these limitations Datalog queries and rules give the experienced user the possibility to define the executable code of query or rule directly including the use of standard PROLOG predica
20. Person in Proposition with transitive acyclic ancestor Person end The more categories like transitive and acyclic are defined with meta formulas the greater is the productivity gain for the modeler Not only does it save coding effort It also reduces coding errors since formula specification is a difficult task Meta formulas are a natural extension to classical meta modeling They allow to specify the meaning of modeling constructs at the meta class level The mapping to simple formulas allows an efficient evaluation It also allows to retrieve the specialized semantics definition of a model instance of a meta model since the generated simple formulas are attached to the constructs of the model in the example above they are attached to classes Person and City The meta formula compiler is fully incremental i e if the object base is updated then the set of generated simple formulas is also updated if necessary For example if one removes the category transitive from the connection attribute of City then the generated simple formula will also be removed Meta formulas that contain meta variables under existential quantification cannot be compiled directly but there is an elegant trick to circumvene this restriction Consider for example the formula forall x VAR SC CLASS spec ISA_complete spec super SC and x in SC gt exists SUBC CLASS spec sub SUBC and x in SUBC The meta variable SUBC is under an existential quantifier T
21. RETELL is containing instantiation facts any formula with an unrestricted predicate x in c has to be re evaluated for any update This inefficiency can be avoied by demanding that the class position is a constant A relaxation to this clause and clause 2 is discussed in sub section 2 2 9 When compiling the frames ConceptBase will make sure that the attribute Guest Employee dept is specializing the two dept attributes of Shop and Department As a consequence the attribution predicate x dept PR can be uniquely attached to its so called concerned class Guest Employee dept The predicate typing condition holds for all formulas regardless whether they occur as constraints or rules of classes or within query classes 2 2 8 Rule and constraint syntax A legal integrity constraint is a CBL formula that fulfills predicate typing condition A legal deductive rule is a CBL formula fulfilling the same condition and having the format forall x1 c1 forall xn cn R gt lit al am where e lit isa predicate of type 1 or 3 and e the variables in al amare contained in x1 xn In O Telos rules and constraints are defined as attributes of classes Use the category constraint for integrity constraints and the category rule for deductive rules The text of the formula has to be enclosed by the character The choice of the class for a rule or constraint is arbitrary except for query classes which use the special va
22. a different implementation class which extends i5 cb graph cbeditor CBUserObject or CBIndividual or CBLink Both possibilities will presented in the next two subsections C 3 1 Properties of CBIndividual and CBLink The easiest way to modify the representation of an object in the Graph Editor is to load an existing graphical type modify its properties and store it as a new graphical type The properties available and there meaning are given in the following Note that colors have to be given as RGB color value e g 0 0 0 is black 255 0 0 is red 255 255 255 is white etc Furthermore all attributes have to be strings even if they are just numbers e g use 1 instead of 1 as attribute value 127 bgcolor Background color of the shape default transparent textcolor Foreground color of the shape i e text color default black 0 0 0 linecolor Color of the border of the shape default transparent linewidth Width of the border of the shape default 1 edgecolor Color of the edge default black 0 0 0 edgewidth Width of the edge default 1 edgestyle possible values are continuous dashed dotted dashdotted default continuous shape The name of the class representing the shape and implementing the interface i5 cb graph shape IGraphShape default no shape The package 15 cb graph shape defines some useful default shapes see below for detai
23. access to the module Mjonny The local overrides the general version CB_ Permitted and its function is not inherited to sub modules 73 There are plenty of ways to combine general and local versions of CB_Permitted yielding different access policies When using access control at least the module System should be protected Otherwise users could change essential definitions affecting all other users Examples for access control policies are in the HOW TO section of the ConceptBase Forum http merkur informatik rwth aachen de pub bscw cgi 2281940 It is very well possible to make access to a ConceptBase database completely impossible by errors in the definition of CB_Permitted For example one could deny access to any operation by the following simple rule GenericQueryClass CB_Permitted isA CB_User with parameter user CB_User res Resource op CB_Operation constraint cperm FALS end E Ur In such cases one has to start the CBserver with disabled access control and repair the definition if the query CB_Permitted Access control is by default disabled see option s in section 6 Hence you need to explicitely enable it when you start the CBserver Caution The access control feature of ConceptBase avoids some unwanted interferences in a setting where multiple users work on the same server The system in not save against malicious attacks Neither does it prevent all unwanted interferences 5 7 Listing the module c
24. activates the ECArule If you don t want to use an ECArule anymore you can untell it as a whole The ECArule evaluator is not very efficient Response times may be long in case that an ECArule leads to many updates to the object base ECArules that update the database will temporarily disable the cache based predicate evaluator By this certain recursive deductive rules called in the IF part of ECArules may not terminate if you activate the CBserver parameter unsafe see section 6 The unsafe mode disables checks on the presence of recursion This leads to faster execution time since the safe mode would refresh the predicate cache after each update to the database 66 Chapter 5 The Module System The module concept provides the facility to divide a ConceptBase database into an arbitrary number of autonomous clusters We use the term module for such a cluster A module is autonomous in the sense that the visibility of objects and validity of deductive rules and integrity constraints is limited to the scope of a certain module This implies that for each server operation TELL UNTELL ASK the user has to define a module in whose context he wants the operation to be executed One useful application of modules in ConceptBase are modelling situations where different objects are labeled with identical names In earlier versions of ConceptBase this was prohibited by the Naming Axiom which demands that different objects have differ
25. and Graph Editor can be run as a stand alone Java application or as an applet inside a web browser The use of CBiva as applet requires a browser with Java Plugin 1 4 or 1 5 If you install a Java Runtime Environment on your machine the plugin is usually also installed and configured for your browsers Linux users might have to install the plugin manually into a dedicated directory of their web browser if they want to create web pages with CBiva or the Graph Editor 8 1 CBiva CBiva is similar to the old CBworkbench used in earlier releases of ConceptBase If you have installed a Java 1 4 1 5 virtual machine you can start the Java user interface by the command lt CB_HOME gt startCBiva sh on UNIX Linux platforms or lt CB_HOME gt startCBiva bat on Windows platforms where lt CB_HOME gt is the installation directory of ConceptBase After a few seconds the CBiva main window should pop up If an error occurs you might you have to edit the script batch file so that the correct Java Virtual Machine can be found Figure 8 1 shows the main window connected to a server and gives a short description of the buttons in the tool bar The user interface uses the MDI multiple document interface model i e all windows are displayed as subwindows in the main window The main window consists of a menu bar a tool bar with a button panel the area for subwindows and a status bar The first sub window a Telos editor can not be closed becau
26. and shortcuts ConceptBase has capabilities to form nested expressions from generic query classes The idea is to com bine them like nested functional expressions e g f g x h y The problem is however that queries stand for predicates and nested query calls are thus formally higher order logic predicates occur as arguments of other predicates and consequently outside Datalog Still the feature is so useful that we provide it A nested query call is like an ordinary parameterized query call except that the parameters can themselves be query calls For example COUNT What_SI_Manager 10000 salary class counts the in stances of the parameterized query call What_SI_Manager 10000 salary Syntactically query calls can be arbitrarily deep e g Union Intersec EmpMinSal 800 minsal X EmpMaxSal 1400 maxsal Y X Manager Y ConceptBase does perform the usual type check on the parameters by analyzing the instantiation of the core class of a query call For example the core class of EmpMinSal 800 minsal is EmpMinSal Thus ConceptBase will check whether EmpMinSal is an instance of the class expected for the parameter X Nested query calls are mostly used in combination with functional expressions i e nested query calls where queries are functions see section 2 5 A function in ConceptBase is a query class that has at most one answer object for any combination of input parameters Of particular interest for nested query call
27. any instance of the query class must be an instance of the superclass Example socially interested are those managers that are member of a union Union in Class end UnionMember in Class with attribute union Union end SI_Manager_0 in QueryClass isA Manager UnionMember end QueryClass SI_Manager in QueryClass isA Manager UnionMember with retrieved_attribute union Union salary Integer end Super classes themselves may be query classes which is the first kind of query recombination The second frame shows the feature of retrieved attributes which is similar to projection in relational algebra Example one wants to see the name of the union and the salary of socially interested managers The attributes must be present in one of the super classes of the query class In this example the union attribute is obviously inherited from the class UnionMember and salary is inherited from Manager CBQL demands that retrieved attributes are necessary each answer must instantiate them If an object does not have such an attribute then it will not be part of the solution As usual with attribute inheritance one may specialize the attribute value class e g QueryClass Well_off_SI_Manager isA SI_Manager with retrieved_attribute salary HighSalary end HighSalary in Class isA Integer with rule highsalaryrule forall m Integer m gt 60000 gt m in HighSalary end The new attribute value class HighSalary is a subclass of Int
28. attribute values of a certain category i e mary dept contains both PR and R amp D e As can be understood as the set variant of but employing the attribute category instead of the concrete attribute label the same holds for with respect to Thus mary dept is the set of all attributes as objects that belong to category dept and have source mary Note that and are only allowed to occur within assertions whereever classes may be interpreted as range restrictions e g in quantifications or at the right hand side of in predicates The full syntax which allows combinations of all basic constructors can be found in the appendix For illustration we just give two examples here The first is an alternative representation for the rule above the second could be a constraint stating that all bosses of Mary earn exactly 50 000 l forall e Employee m Manager m in e dept head gt e boss m 2 forall b Mary dept head b salary 50000 2 2 11 User definable error messages for integrity constraints ConceptBase provides a couple of errors messages in case of an integrity violation These errors messages refer to the logical definition of the constraint and are sometimes hard to read To provide more readable er ror messages one can attach so called hints to constraint definitions These hints are attached as comments with label hint to the attribute that defines the constraint Consider the salary bound constrai
29. attributes could be defined for the class Employee as follows Employee in Class with attribute single name String attribute aliasname String end Here the following predicate facts would be true Employee in Class Employee attribute name String Employee single name String Employee attribute aliasname String Employee attribute String Employee single String Pe O The mechanism for attribution is exactly the same as for instances like mary Note that the 3 argument attribution predicate expressing mary name Mary Smith represents a meaningful statement for some reality to be modeled On the other hand the predicate fact Employee attribute String is much less significant because the label attribute does not transport a specific domain meaning Here the 4 argument attribution predicate such as used for the fact Employee attribute name String is required Still from a formal point of view there is no different treatment of predicates at the class and instance level This uniformity is the basis for meta modeling i e the definition of modeling languages by means of meta classes The class labels attribute and single need to be defined at the classes of Employee Those are Class and the pre defined class Proposition to which any object including Employee and mary is instantiated In this case both attribute and single are defined for Proposition Proposition attribute at
30. class spSet computes the set of length of shortest path between the successors of a node x and a node y The length of the shortest path is then simply 0 if x y or the minimum of the spSet x y plus 1 if there is a path from x to y and undefined else The signature of spSet must be known for compiling sp and vice versa ConceptBase has a single pass compiler Hence it requires the forward declaration The query spSet is not a function because it returns in general several numbers The complete example for computing the length of the shortest path is in the CB Forum see http merkur informatik rwth aachen de pub bscw cgi 1694234 Recursive function definitions require much care Deductive rules shall always return a result after a fi nite computation This does not hold in general for recursive function definitions when they use arithmetic subexpressions These subexpressions can create new objects numbers on the fly and thus force Conceot Base into an infinite computation On the other hand they are very expressive and useful to analyze large models in a quantitative way 2 6 Query evaluation strategies ConceptBase employs an SLDNF style query evaluation method i e query predicates are evaluated top down much like in standard Prolog This is known to cause infinite loops for certain recursive rule sets 43 To overcome this the SLDNF evaluator is augmented by a caching sub system which detects recursive predicate calls and answers them
31. evaluation The partial evaluation procedure is limited to a conjunction of predicates preceeded by forall quantors 138 e no source to source transformation Formulas are not converted automatically into the form mentioned above supported by the meta formula mechanism even if they could be transformed If the class variables can t be bound using partial evaluation of the input formula the formula is rejected even if there exists an equivalent formula in which partial evaluation could be used to bind the class variables e not all classes are supported Generated formulas where variables are quantified over instances of the following classes or at tributes of them will be ignored Those classes are Boolean Integer Real String TransactionTime MSFOLassertion MSFOLrule MSFOLconstraint metaMSF OLconstraint metaMSFOLrule BDMConstraintCheck BDMRuleCheck LTrule Evaluator ExternalReference QueryClass BuiltinQueryClass AnswerRepresentation GraphicalType X11_Color ATK_TextAlign ATK_Fonts ATK_LineCap ATK_ShapeStyle The justification is twofold Some of these generated formulas e g a formula beginning with S forall x l are regarded as redundant because the object as instance of Integer should have no instances Another justification is that the use of meta formulas should be restricted to user defined modeling tasks Manipulation of the most system classes is disabled for reasons of efficiency and safety In the case
32. expanding the attributes Disabled by default Enabling it is not recommended Undo last layout operation Undo the last change of the graphical layout This option is only available when automatic layout is enabled Layout graph Call the layout algorithm 96 A CE GraphEdiOT Es File Edit Options View Current connection SA S MIE ce ma A g D Individual Class C super classes E sub classes 9 only explicit 5 QueryClass o Hall J instance of PS J instances individual QueryClass 3 outgoing attributes QueryClass in Class isA Class with 5 i attribute retrieved_attribute Proposition computed_attribute Proposition constraint MSFOLquery end il Di Connected with localhost Figure 8 8 Component view of Telos objects tree and frame Zoom Set the zoom factor of the graph e g 120 20 percent enlarged 200 100 75 50 25 Set the zoom factor accordingly Current connection menu These operations have effect on the current connection i e the connection of currently activated frame Query to server This operation will open a dialog which prompts you to enter the name of a query see figure 8 9 The query can also be parameterized If you click on the Submit Query button the query will be sent to the server and the result will be displayed in the listbox You can select the objects that should be added to the graph Select
33. exprl expr2 e OWER exprl expr2 e EQUAL exprl expr2 e AND exprl expr2 e OR exprl expr2 e ISFIRSTFRAME e ISLASTFRAME Example GREATER this salary 10000 Note that the arguments may also contain ex pressions The predicate ISF IRSTFRAME is true when ConceptBase starts with processing answer frames It is false when the first frame has been processed The predicate ISLASTFRAME is true 54 when ConceptBase starts with processing the last answer frame for a given query Otherwise it is false An example for conditional expressions is provided in the CB Forum see file csv sml in http merkur informatik rwth aachen de pub bscw cgi 861803 In most cases the IF THENELSE construct can be avoided by a more elegent query class formulation 3 2 9 Views and path expressions If the answer format is defined for a complex view then path expressions like this cat2 cat21 for the parts of the complex answer can be defined An example for use of answer formats for views is given in views sml The reader should note that complex path expressions can only refer to components that were de fined as retrieved computed or inherited attributes in the view definition For example one cannot refer to this dept budget in the example view EmpDept in views sml since it is not a retrieved attribute of the dept component of the view definition E
34. following frame Employee with attribute name String end The object Employee is now only visible in the module Master When you set the module context to Work or System and try to load the Employee object you should get an error message from the server stating that the object Employee is not visible in that module context 68 5 3 Using nested modules A nested module is a module defined in the context of a father module and therefore can only be seen in the context of the father After the definition of the Master and Work modules as nested modules to the oHome module let s define a nested module to the Work module We assume that the current module context is set to the Work module Now tell the following frame Module Test end As a result we have defined the nesting hierarchy depicted in Figure 5 2 System oHome Master Work Test Figure 5 2 A simple nesting hierarchy of modules A nested module can see the content of all its fathers Therefore when you set the module context to Test you can reference all objects contained in the modules Test Work oHome and System When you set the module context to Work you can reference all objects contained in Work oHome and System 5 4 Exporting and importing objects In order to use objects which are not visible in a module ConceptBase offers the export import facility The Module object has two further attributes namely to object
35. format The pattern of an answer format is applied to each answer object of a given query call effectively transforming it according to the pattern The following expressions are allowed Capital letters in the list below indicate that the term is a placeholder for some label occuring in the query definition or the answer objects this denotes the object name of an answer object e g A The syntax for object names is defined in section 2 1 In particular attribution objects have names like mary earns this ATTRIBUTE_CAT denotes the value s of the attribute ATTRIBUTE_CAT of the current answer object this The attribute must be defined in the query class retrieved_attribute computed _attribute or view inherited_attribute Note that some attributes are multi valued For the answer object A this cat1 evaluates to v11 v12 and this cat2 evaluates to v21 For the complex object B a path expression like this cat2 cat21 is allowed and yields v21 Note that all such expressions are set valued this ATTRIBUTE_LABEL denotes the value of the attribute ATTRIBUTE_LABEL of the current answer object this The attribute_label is at the level of the answer object i e not at the class level but at the instance level Therefore this expression is rarely used because the instance level attribute labels are usually unknown at query definition time Example A and B this label12 evaluates to v12 th
36. from the cached results of a query rather than entering an infinite loop This cache based evaluation computes the fixpoint answer of a query provided that the overall rule set is stratified Even more dynamically stratified rule sets are supported as well Other than with the static stratification test a violation is detected at run time of a query rather than at compile time For a precise definition of stratification we refer you to the literature on deductive databases For the purposes of this manual consider the following rule forall p Position exists pl Position p moveTo pl and not pl in Win gt p in Win ConceptBase internally compiles such rules into a representation where Position moveTo and Win are predicate symbols forall p exists pl Position p and Position pl and moveTo p pl and not Win pl gt Win p Static stratification requires that one can consistently assign stratification levels numbers to the set of predicate symbols such that 1 If there is a rule with conclusion predicate A and positive condiction predicate B not negated then the level of A must be greater or equal the level of B 2 If there is a rule with conclusion predicate A and negated condiction predicate B then the level of A must be strictly greater the level of B In the example above the conclusion predicate Win depends on the condition predicate not Win Since we only can assign one level to Win we cannot find a stat
37. in Module end mary in CB_User with homeModule ml Projectl end john in CB_User with homeModule ml Project2 end 70 As a consequence the start module of the two users will be set accordingly when they log into the CBserver The home module feature is especially useful in a teaching environment The teacher can put some Telos models into the shared System module Students home modules would be assigned to sub modules e g based on group membership Each student group can then work on an assignment by working on their sub module without interfering with other student groups There is a subclass Aut oHomeModule of Module which addresses teaching applications of Con ceptBase where by default any user should work in her own module context Rather than having to define separate modules for each user explicitely you can just define a certain module to be of type AutoHomeModule LectureModule in AutoHomeModule with exception el mary end mary in CB_User with homeModule ml LectureModule end john in CB_User with homeModule ml LectureModule end Here user john a student will be automatically be assigned to a new module Workspace_john that is created as sub module of LectureModule User mary presumably the teacher is defined to be an exception to this rule and she will get the home module Lect ureModule By this one can reduce the chances of unwanted interferences between users of the module LectureModule Still all st
38. integration approach with the main design goals of semantic simplicity sym metry of deductive and object views flexibility and extensibility This emphasis technically supported by a careful mapping of Telos to Datalog with negation has paid off both in user acceptance and ease of implementation In essence ConceptBase is based on deductive database technology woth object oriented abstraction principles like object identity class membership specialization and attribution being coded as pre defined deductive rules and integrity constraints Development of ConceptBase started in late 1987 in the context of ESPRIT project DAIDA Jark93 and was continued within ESPRIT Basic Research Actions Compulog 1 and 2 1989 1995 the ESPRIT LTR project DWQ Foundations of Data Warehouse Quality 1996 1999 and the ESPRIT project MEMO Mediating and Monitoring Electronic Commerce 1999 2001 Versions have been distributed for research experiments since early 1988 ConceptBase has been installed at more than eight hundred sites worldwide and is seriously used by about a dozen research projects in Europe Asia and the Americas The direct predecessor of O Telos is the knowledge representation language Telos specified by John Mylopoulos Alex Borgida Manolis Koubarakis and others Telos was designed to represent information about information systems esp requirements Telos was based on CML Conceptual Modeling Language developed in the mid late 1980 t
39. isA SI_Manager with retrieved_attribute union Union computed_attribute head_of Department constraint well_off_rule exists s HighSalary this salary s and head_of head this end The variable head_of in the constraint is prefixed with to indicate that it is a placeholder for the compted attribute with label head_of We recommend to use the prefix to avoid confusion of the place holder variable in query constraints and corresponding attribute label in the query definitions Analogously you can use the prefixed answer variable this instead of the plain version this ConceptBase will ac cept both the prefixed and the non prefixed version for the answer variable and the placeholder variable 31 of computed attributes Non prefixed placeholders in constraints are replaced internally by the prefixed counterparts The generated deduction rules for above query would be forall this vl v2 this in SI_Manager and this union vl and vl in Union and v2 in Department and exists s s in HighSalary and this salary s and v2 head this gt Well_off_SI_Manager2 this vl v2 forall this vl v2 Well_off_SI_Manager2 this vl v2 gt this in Well_off_SI_Manager2 Computed attributes are treated differently from retrieved attributes The retrieved attribute union causes the inclusion of the condition this union v1 and vl in Union The corresponding variable v1 does not occur in the sub formula generated for the quer
40. iterated query Q as well Do not mix the use of ASKquery with the view definitions in ConceptBase The nesting depth of a view is determined by the view definition The nesting depth of an answer generated by expansion of ASKquery is only limited by the complexity of the database For example one can set up an ancestor database and display all descendants of a person and recursivley their descendants in a single answer string for that person The nested ASKquery inside an answer format usually results in the unfolding also using an answer format possibly the same as used for the original query This feature allows the user to specify very complex structured answers that might even contain the complete database In particular complex XML representations can be constructed in this way 3 2 7 Expressions in head and tail The features head and tail are similar to pattern The difference is that any expression using this the running variable for answer objects is disallowed This only leaves function patterns such as ASKquery expressions and pre defined patterns such as user Of course the head and tail strings can contain multiple occurences of ASKquery or other function patterns 3 2 8 Conditional expressions Conditional expressions allow to expand a substring based on the evaluation of a condition The syntax is IFTHENELSE predicate thenstring elsestring The predicate can be one of e GREATER
41. like do y Here the inner term y is first evaluated e g to 20 and then the result do 20 is evaluated In general term substitution can result in infinite loops This looping can be prevented either by re stricting the structure of the substitution rule or by terminating the substitution process after a finite number of steps The end result of a substitution process of a string is called its derivation In ConceptBase the 48 substitution rules are guaranteeing termination except for the case of external procedures The problem with the exception is solved by prohibiting cyclic calls of the same external procedure during the substi tution of a call A cyclic call is a call that has the same function name e w query class and the same arguments expressed as parameter substitutions In ConceptBase an answer format is an instance of the new pre defined class AnswerFormat Individual AnswerFormat in Class with attribute forQuery QueryClass order Order orderBy String head String pattern String tail String fileType String end The first attribute assigns an answer format to a query class a query may have at most one answer format The second and third attribute specify the sorting order of the answer i e one can specify by which field an answer is sorted and whether the answer objects are sorted ascending or descending much like in SQL The head pattern a
42. links will be saved into a file which can be reloaded later If the option include graphical types for saving layouts is enabled see Options menu then the graphical types will also be saved into the file This option is useful for offline usage of the Graph Editor i e without a server as all information necessary to visualize the graph will be included in the file By default the file will get the extension gel Graph Editor Layout Load Load a layout that has been saved with the previous menu item Existing nodes and links in the current window will be erased Print Print the current graph If the graph is larger than the page size it will be automatically reduced to fit into the page Thus all printouts will be on one page Save image of graph Saves an image of the current graph as PNG or JPG file The PNG file format should be preferred as it delivers better results Close Closes the Graph Editor A CBiva window will be still available if it has not been closed before Exit Exit the Graph Editor and CBiva This operation will close both windows of the ConceptBase User Interface and exit the program 95 Edit menu The operations in this menu have an effect on the selected objects You can select an object by clicking on it with the left mouse button Multiple selection is possible dragging a rectangular area while holding down the left mouse button or by holding the Shift key and clicking on objects Erase Se
43. lt literal gt lt formula gt gt lt literal gt lt literal gt lt formula gt lt formula gt exists lt variableBindList gt lt formula gt forall lt variableBindList gt lt formula gt not lt formula gt lt formula gt lt gt lt formula gt lt formula gt lt formula gt and lt formula gt lt formula gt or lt formula gt lt formula gt lt literal gt lt literal2 gt gt lt formula gt lt variableBindList gt gt lt variableBind gt lt variableBindList gt lt variableBind gt 117 lt variableBind gt gt lt varList gt lt objectname gt lt varList gt lt objList gt ALPHANUM lt selectExpB gt lt varList gt gt ALPHANUM lt varList gt ALPHANU lt objectname gt gt lt label gt lt selectExpA gt lt deriveExp gt lt label gt gt ALPHANU LABEL NUMBER lt literal gt gt FUNCTOR lt literalArgList gt lt literalArg gt lt infixSymbol gt lt literalArg gt lt arExpr gt COMPSYMBOL lt arExpr gt lt literalArg gt lt label gt lt label gt lt literalArg gt BOOLEAN lt literal2 gt gt lt label gt in lt selectExpB gt lt selectExpA gt in lt selectExpB gt lt selectExpB gt isA lt selectExpB gt lt selectExpB gt lt selectExpB gt lt infixSymbol gt gt INFIXSYMBOL lt label gt lt literalArgList gt gt lt literalA
44. miles oe caese erae tua a 02809 Ae EPE eae ce ek BA ee A e ie a io 4 1 10 User definable Error Messages ek RR ee e DLL COSAS oo o esc ea we ee ee ee eA 2 EXAMS oe eos o te a oe Be ha te Gece BP Sh joel ee Sw Sk Ae we SE aS 4 2 1 Materialization of views by active rules 0 122 COUDE os ae ka a AR A Rae AGA Ba a ee es 42 5 Timestamps ssa bee ew bea ee eee a EES Eas 424 Simulation of Petri New ooo 03444 S468 been eb we eee 4 3 Limitations in the current implementation 6 ee 2 The Module System 31 Definitonof modales s isece bean CoA eee as bea eee be eA 5 2 Switching between module contexts o o 33 Using nested Moduls oc ae Ae a ee a ee eS 54 Exporting and importing Obes 2 kk eS AG a Re So Seine weer home Modules s o lt e cd ee bbe ea eee be eee ee eed 5 6 Limiting access to modules gt lt lt s so ea a ka eR ES RD e A a 2 Listing the module content ps cae ee ee HR OM RR ESE RES EH y ROS 258 Saving and loading module sources 2 es EEE RN eS Eee ES ESA SY 5 9 Server side materialization of query results o e e The ConceptBase cc Server 6 1 lt Bserver PATAS escocia A A G2 The Caco SUbS VSI ee A ar A ERR ES 6 3 Database persisieney icon eA eae aa ee Pe ee E GA The UNTBLLaperation 2 2 65 4 6045 488 E e bbe debe dba and 6 5 Memory consumption and performance 2 5 6 065 6 bee 2 ms 67 67 68 69 69 70 7
45. need to be instantiated at the instance level This is the case for the boss attribute of Employee On the other hand they may be instantiated more than once as e g dept In some cases for attribute categories occuring in a frame the corresponding objects which are instanti ated by the concrete attributes can not uniquely be determined This multiple generalization instantiation problem is solved by the following condition which must hold for O Telos object bases Multiple generalization instantiation axiom axiom 17 in appendix B If pl and p2 are attributes of two classes c1 and c2 which have the same label component 1 and iis a common instance of cl and c2 which has an attribute with category 1 then there must exist a common specialization c3 of cl and c2 with an labelled attribute p3 which specializes pl and p2 and i is instance of c3 Particularly if cl is specialization of c2 and p1 is specialization of p2 cl and p2 already fulfill the conditions for c3 and p3 O Telos treats all three kinds of relationships att ribute isa in as objects Thus each attribute instantiation or generalization link of Employee may have its own attributes and instances For example each of the four Employee attributes is an instance of an attribute class denoted by the label attribute but can also have instances of its own The attribute with label earns of mary is an instance of attribute salary of class Employee Syntactically attribute objec
46. new frame Hide selected without connection Show M Create objects Commit ma DSM L rial en Bi A le Load amp ladon layout Open Show links Show added connection between objects removed objects Figure 8 10 Tool Bar of the Graph Editor Save layout see File Menu Save Hide selected objects Hides the selected objects from the current view This operation has no effect on the current database i e the objects will be not deleted from the database Open connection Opens a new frame with a new connection to a server See File menu Connect to server Show object This operation adds a new object to the graph You will be prompted to enter the object name of the object you want to add to the graph Show links between marked objects This operation will search for relationships between the selected objects Do not select too many objects for this operation n queries have to be evaluated for n objects Creation of objects The following four buttons open the Create Object dialog to create new individual objects attributes instantiations and specializations See section 8 2 6 for more details Show added removed objects Shows the objects that have been added or removed since the last commit or since the window has been opened Here you can also select objects to undo the change 1 e remove added objects or re insert removed objects Commit Sends the changes to the server The list of objects to be added or
47. not the same All comparison predicates may use functional expressions as operands They are evaluated before the comparison predicates is evaluated See section 2 3 3 for examples The predicates x y UNIFIES x y and IDENTICAL x y defined in earlier releases of ConceptBase are deprecated It is recommended to use x y instead 2 2 6 Typed variables The exact syntax of CBL is given in appendix A The types of variables i e quantified identifiers are interpreted as instantiations e forall x C F gt forall x x in C gt F SFor the example of subsection 2 1 among others the ground predicates mary in Manager Manager isA Employee and mary earns 15000 are valid facts describing the contents of the object base We suggest to choose verbs e g earns in our example for attribute labels to get more natural and readable predicates 22 e exists x C F gt exists x x in C and E The class C attached to variable x is called the variable range The anonymous variable range VAR is treated as follows e forall x VAR F forall x F e exists x VAR F gt exists x F Anonymous variable ranges are only permitted in meta formulas see section 2 2 9 2 2 7 Semantic restrictions on formulas We demand that each variable is quantified exactly once inside a formula This is no real restriction in case of double quantification rename one of the variables More important is a restriction similar to static type che
48. of a class ConceptBase offers a set of predicates for the predicative language defined on top of an O Telos object base as visible for a given rollback time OBr t P oid x 1 y P oid x 1 y tt OB rbt during tt The value of the rollback time depends on the kind of formula to be processed integrity constraints are evaluated on the current object base OBnow Now the smallest time interval that contains the current time The rollback time of queries is usually provided together with the query when it is submitted from a user interface to a ConceptBase server By default it is Now as well 2 2 1 Basic predicates The following predicates provide the basic access to an O Telos object base Some have both an infix and a prefix notation As usual we employ the object identifer to refer to an object l x in c orIn x c The object x is an instance of class c 2 c isA d or Isa c d The object c is a specialization subclass of d 3 x m y orA x m y The object x has an attribution link to the object y and this link has the attribute category m Structural integrity demands that the label m belongs to an attribute of a class of x 6The original specification of Telos has two temporal components The valid time and the belief time The valid time is defined as the time interval when the statemment made by a Telos proposition is true in the world The belief time is the time when this statement is part of the knowledge base
49. of a class must be reals or integers AVG computes the average of the instances of a class must be reals or integers MAX gives the maximum of the instances of a class wrt the order of lt and gt see section 2 2 MIN gives the minimum of the instances of a class wrt the order of lt and gt see section 2 2 COUNT Attribute counts the attributes in the specified category of an object SUM_Attribute computes the sum of the attributes in the specified category of an object must be reals or integers AVG Attribute computes the average of the attributes in the specified category of an object must be reals or integers MAX Attribute gives the maximum of the attributes in the specified category of an object wrt the order of lt and gt see section 2 2 MIN Attribute gives the minimum of the attributes in the specified category of an object wrt the order of lt and gt see section 2 2 PLUS computes the sum of two reals or integers MINUS computes the difference of two reals or integers MULT computes the product of two reals or integers DIV computes the quotient of two reals or integers IPLUS computes the sum of two integers result is an integer number IMINUS computes the difference of two integers result is an integer number IMULT computes the product of two integers result is an integer number IDIV computes the quotient of two integers and then truncates the quotient to the largest integer number smal
50. of undoing changes The button Show added removed objects list all objects that have been added or removed since the last succesful commit or since the connection has been established A screenshot of the dialog is shown in figure 8 12 The left list shows the objects that have been added the right list shows the objects that have been removed By clicking on the button Re Insert Delete object the selected objects will be re inserted in or deleted from the graph Add Remove Objects urrentty added objects Currently erased obje New_Object JueryClass New_Objectllabel JueryClass gt Class Re Insert Delete obje Figure 8 12 List of objects which have been added or removed If you are satisfied with the changes you have done you can click on the Commit button Then the Graph Editor will transform the objects to be added or removed into a list of Telos frames and send them to the server using the TELL UNTELL or RETELL operation If the operation was successful all explicit objects will be checked if they are still valid and if their graphical type has changed as in the Validate and update operation from the Current Connection menu If there is an error the error messages of the server will be displayed in a message box The internal buffer with the objects to add or remove will be not changed in this case 8 2 7 Caching of query results within the graph editor To improve the performance
51. or a more specific class name CreateA ttribute AttrCat x y ID This predicate creates a new attribute for object x with value y in the given attribute category e g Employee salary The attribute will get a system generated label In contrast to the action Tel 1 A x ml y the attribute is also created if another attribute with the same attribute category already exists 2Retell is currently restricted to attribution predicates A x ml y It will replace the old value of attribute ml of x by y ConceptBase realizes the Rete11 A x ml y by acombination of Untel1 A x ml z removing the first stored attribution fact A x ml1 z and a subsequent Tell A x ml y If there are several facts such as A x m1 z1 andA x ml z2 then only the first one is removed by the Unte11 3Note that an object can have more than one attribute value in one attribute category but the attributes must have different labels 59 Other predicates to be invoked via CALL can be defined in a LPI file see Counter example below Events and actions may also be specified in a prefix syntax e g Tell x in Class instead of the longer form Tell x in Class Furthermore there are two simple builtin actions noop is not doing anything except that is succeeds and reject aborts the current transaction If the execution of an ECArule leads to an update to the database i e via Te11 or Unte11 then the updated database is subject to integrity checking
52. paraml1 smith param2 FRAME 14 The answer is 15 where we assume the following example substitution rules 53 rl xl gt name 12 this catl alpha 13 this name smith r4 x2 gt param2 r5 ASKquery MyQuery FRAME gt The answer is This guarantees that the query call is ground i e does not contains terms which are subject to substi tution The ASKquery construct allows to introduce recursive calls during the derivation of a query since there can and should be an answer format for Q which may contain expressions ASKquery itself In principle this allows infinite looping However the answer format evaluator prevents such loops by halting the expansion when a recursive call with same parameters has occured The answer then contains an character at the position where the loop was detected Additionally an error message is written on the console window of the ConceptBase server tracemode must be at least low A simple example for use of ASKquery is given in recursive answers sml The example uses a view instead of a query class in order to include also answers into the solution which not have a filler for the requested attribute i e hasChild is inherited_attribute not retrieved_attribute It is common practice to combine the ASKquery construct with Foreach in order to display an iteration of objects in the same way The user should define an answer format for the
53. processing of meta formulas The VAR construct is only allowed in meta formulas It enables the user to leave the concrete classes of x and m open without instantiating them to for example to Proposition The single constraint can be defined in analogy These constraints can be added to the system as if they were normal constraints Their effect becomes visible when declaring attributes as necessary or single This is done in the following model KK KK KKK KK KKK KKK KK KK KK File ERSingNec x KKK KKK KKK K KEK KKK KK KK KKK A x necessary constraint metaformula Class with constraint necConstraint forall c d Proposition p Proposition necessary x m VAR P p c m d and x in c gt exists y VAR y in d and xm y end x every Entity has a key x Class EntityType with necessary keyeAttr Domain end x single constraint metaformula Class with constraint singleConstraint forall c d Proposition p Proposition single x m VAR P p c m d and x in c gt forall al a2 VAR al in p and a2 in p and Ai x m al and Ai x m a2 gt al a2 end x every Entity key is monovalued necessary and single Class EntityType with rule keys_are_necessary Sforall a EntityType keyeAttr In a Proposition necessary keys_are_singl Sforall a EntityType keyeAttr In a Proposition single end The effects of this transaction can be shown by disp
54. property returns true if the property is defined for this graphical type JPopupMenu getPopupMenu returns the popup menu for this object By using this method you can extend the popup menu with own operations If you overwrite this method the operations in the default popup menu will not be available Example The following example defines a graphical type that uses a JButton to visualize the object Only the method getSmallComponent is overwritten The background color of the button will be changed if the property bgcolor has been defined The example shows that the implementation of graphical types is quite simple import i5 cb graph cbeditor import javax swing x import java awt Component xx x An example for a user defined CBUserObject public class MyOwnGraphType extends CBUserObject public Component getSmallComponent JButton jButton new JButton this getTelosObject toString if hasProperty bgcolor jButton setBackground CBUtil stringToColor getProperty bgcolor return jButton 129 C 3 3 Shapes The package i5 cb graph shape contains several shapes which might be useful for the ConceptBase Graph Editor To use these shapes you have to specify the full class name including the package name as value of the property shape of a graphical type class name style Arrow Head of an arrow pointing to the right Arrow2 Complete arrow pointing up Cro
55. rule checks 1f the employee belongs to the view when the employee was inserted Note that we don t use the constraint of the view in the ECArules we just reuse the view definition here The second rule does the same for deletion of employees The third rule checks 1f the employee is an instance of the view class when the attribute salary was inserted Again the fourth rule does the same for deletion of the attribute If the number of employees is large it is more efficient to ask for the instances of materialized than to evaluate the view However if updates occur quite often materialization is not good because materialized view must be maintained for every update transaction 4 2 2 Counter This example shows how to call prolog predicates with an ECArule It implements a counter for a class Employee The counter is stored as an instance of the object I EmployeeCounter Whenever an employee is inserted or deleted from the object base the counter is incremented or decremented Class Employee end EmployeeCounter end ECArule EmployeeCounterRule with ecarule er x Employee i il Integer ON Tell In x Employee IF i in EmployeeCounter DO Untell In i EmployeeCounter CALL increment i il Tell In il EmployeeCounter ELSE Tell In 1 EmployeeCounter end ECArule EmployeeCounterRule_del with ecarule er x Employee i il Integer O
56. server will be started and its output will be captured in a separate window The workbench will be automatically connected to that server Stop CBserver Stops the ConceptBase server only allowed for the person who started the server Close Close the CBiva Window a CBEditor window remains open if available Exit Exit CBiva and CBEditor Edit Clear Clears the text area of the currently activated Telos editor Cut Copy Paste Cut copy or paste text to from clipboard Tell Untell Un Tells the text in the currently activated Telos editor Retell A new window will popup and ask you to enter the frames that should be untold and told The contents of the current Telos Editor will be inserted as default into the two text areas 3This is not the standard way to start the ConceptBase server Normally the ConceptBase server is started in a separate shell command window as explained in section 6 The standard way offers more options and control over the ConceptBase server See also the installation guide for a discussion on the various ways to start ConceptBase 87 Ask Frame Temporarily tells the content of the Telos editor extracts the query names from the frames asks them as query calls without parameters and returns the result in the Telos editor window Ask Query Call The query calls see section 2 3 1 listed in the Telos editor are asked and the result is returned in the Telos editor window Load Object Load the Telos frame of
57. stances of these objects KOK KR ARA KA OK OK OK OK OK KKK KARA RARA RARA RARAS x KOK IK IK KK KK OK OK OK OK OK RK OK OK OK OK KK x File ERModelGTs x x Definition of the graphical palette for x ER Diagrams for use on color displays x x graphical type for inconsistent roles x Class InconsistentGtype in JavaGraphicalType with attribute property textcolor 0 0 0 edgecolor 255 0 0 edgewidth 2 implementedBy implBy i5 cb graph cbeditor CBLink priority p 14 end x graphical type for entities x Class EntityTypeGtype in JavaGraphicalType with property bgcolor 10 0 250 Caste lor TOD 0 linecolor 0 55 144 shape i5 cb graph shapes Rect implementedBy implBy i5 cb graph cbeditor CBIndividual priority pz We end x graphical type for relationships Class RelationshipGtype in JavaGraphicalType with 135 property bgcolor 255 0 0 textcolor 0 0 0 linecolor 3 0 0205 shape i5 cb graph shapes Diamond implementedBy implBy i5 cb graph cbeditor CBIndividual priority p 13 end x graphical palette Class ER_GraphBrowserPalette in JavaGraphicalPalette with contains defaultIndividual cl DefaultIndividualGT contains defaultLink c2 DefaultLinkGT contains implicitIsA c3 ImplicitIsAGT contains implicitInstanceOf c4 ImplicitInstanceOfGT contains implicitAttribute c5 ImplicitAttributeGT
58. that uses this directory and then delete the file OB lock Then the CBserver should start correctly 6 2 The cache subsystem Since version V5 2 4 ConceptBase cc features a new query evaluation method which uses a so called fact cache to store intermediate results of predicates that are called during the query evaluation Assume for example that an employee bill has two projects p1 and p2 Then the result of a predicate bill hasProject x with variable x would be the set bill hasProject p1 bill hasProject p2 consisting of facts We call this fact set also the extension of the predicate After a completed predicate evaluation the cache of the predicate holds its extension The cache speeds up query evaluation and prevents infinite loops when ConceptBase cc evaluates recursive queries and de ductive rules Essentially the cache based evaluation allows to compute dynamically stratified semantics of the Datalog database underlying ConceptBase cc Plenty of examples for recursive rules and queries are provided in the online ConceptBase Forum The CBserver provides three cache modes to control the behavior during query evaluation c off In this mode the cache is completely disabled Use this mode when your models do not include recursive rules The mode is only provided for backward compatibility and has no advantages c keep The cache is only emptied when necessary i e when the cache has been invalidated by an u
59. the related links are redisplayed Selection and movement of multiple nodes and links is also possible We can further experiment with the graph editor by showing the classes and attributes of Employee The classes of Employee are shown by selecting Instance of from the popup menu Attributes of an object can be shown by selecting Outgoing attributes from the menu The next submenu will show all attribute classes that apply for the current object In our example Employee is an instance of Class Therefore it has the attribute classes constraint rule and mrule see figure 8 18 The attribute class Attribute applies to all objects as in Telos any kind of object can have an attribute Furthermore all attributes of an object are member of the attribute class Attribute As we want to see all attributes 104 localhost4001 Figure 8 17 The resulting graph after expanding with the instances of Manager we select this attribute class and select Show all from the next submenu All attributes and their values will be shown in the Graph Editor The Graph Editor can also show implicit relationships between objects e g relationships deduced by 105 F localhost4001 7 super classes sub classes instance of instances outgoing attributes Attribute only explicit gt incoming attributes constraint gt all Add Instance rule Add Class graphtype gt Add SuperClass Add SubC
60. to varying database sizes Results indicate that ConceptBase apparently approximates in many cases the theoretic optimum The performance of the active rule evaluator section 4 is currently rather limited We measured around 100 rule firings per second This could be a bottleneck when your active rules can trigger each other 83 Chapter 7 The CBshell utility The ConceptBase cc Shell CBshell is a command line client for ConceptBase cc It allows to interact with a CBserver via a text based command shell Moreover it can process commands from a script file without further user interaction The utility can be employed to automate certain activities such as batch loading a large number of Telos models into a CBserver or to extract certain answers from a CBserver 7 1 Syntax lt CB_HOME gt bin CBshel i f scriptFile t i lt CB_HOME gt bin CBshell bat 1 f scriptFile t 1 Make sure that the variable CB_HOME in the CBshell command file is set to the installation directory of ConceptBase cc This is done automatically by the CBinstaller utility described in the Installation Guide 7 2 Options 1 This options instructs CBshell to write errors and some statistic information to the files error log and stat log f scriptFile Execute the commands specified in scriptFile rather that requesting commands from the com mand line interface If the f option is used and a scriptFile is specified the comma
61. 0 seconds If CBiva has no connection with a server the Graph Editor will be started without a connection and no internal window will be opened within the Graph Editor It is also possible to start the Graph Editor directly from the command line without starting CBiva The main class of the Graph Editor is i5 cb graph cbeditor CBEditor This class has to be given as argument on the command line when you invoke the Java Virtual Machine e g java classpath CB_HOME lib classes cb jar i5 cb graph cbeditor CBEditor 8 2 3 Menu bar The menu bar provides access to the most important functions of the Graph Editor File menu Connect to server Connect to a new server You can have multiple connections to one server or different servers at the same time Each connection will be represented in one internal window with the host name and port number in the title bar of the window The connection dialog consists of two tabbed panes In the first one Address you can enter the host address name or IP number and the port number In the second pane Initial Object you can specify the initial object to start the browsing process and the graphical palette Start Workbench Start a CB workbench aka CBiva If you started the Graph Editor directly or if you have already closed the workbench window you can re start the workbench by this menu item Save Save the current layout of the graph into a file The current nodes their location and the
62. 1 74 75 76 7 The CBshell utility E ho eR ie he oe ae ea ee a ok ee et BS Ae TL SPOONS lt lt foe eee ee EE Gee we eR Cee A To Commands eee dk ee Be PS Oe BR SE Ae Shwe GPa Oa 8 The ConceptBase Usage Environment Sl Ed pisa ee Bhd a eo ROWERS DG OE EASE ee ae BSS k 1il Themen Dat seer eer ee we a A ee lS eae Oe The Poel Bal ss oia a Ack WR bots Bowe a a A ee S13 The state bal lt e oq a we eA ee ee ee ee eS ld Telos dir sc oe ce eed Dee EMS ERDAS eS ee Ss edo History WRI se sorae ek y A ee EO He Se oly Display miare 0 cs oe ee Bh Ee ere eae Sheed ae dd Sli Pre bowi IN Sle Display QUESOS oc 222 6 b4 454 bh wee EES EAS CHAS S19 Quem edia anv es ee Slee Re eS ee OE eee EE Rew oS 1 10 Ties BONE lt lt Ge ee AG Oe oe Ew AGRA A wee eS ewe EY 3 2 ConceptBas praphediter lt sc ck RG Be a So gal OVERVIEW cb ke hw Ee RA ORO A ee ee eS 2 2 Starine the rap SOT cocos es oe Ra Sw SA ew S20 WEN Das 263 2G ee kG we RAS Re Ree A Ge ee he MS 2d Toolbar o sede Baw Sd aE we BARE GLE BAe GEG a eae S 8 23 Popapmemy 222 5544 n 5456 ae E a oe ok ee Se es A 205 Editngof Telas objec s gt e oce he che eee SERRE EA CAA 8 2 7 Caching of query results within the graph editor 8 3 An example session with ConcepiBlase o ore ecse sha dek a RES e eR A 3 31 Starting ConcepiBas oo e so ooo Rk ee AS G 8 3 2 Connecting CBiva to the ConceptBase server oo 8 3 3 Loading objects from external file
63. 1 y2 gt 01 02 V l in V l isa Axiom 4 The name of instantiation and specialization objects in isa is unique in conjunction with source and destination objects V 01 L Y 02 Plains l y A P 02 x l y A in V 1 isa gt 01 02 Axioms 5 6 7 8 Solutions for the predicates In Isa and A are derived from the object base Vo x c P o x in c gt In x c V o c d P o c isa d Isa c d Vo x n y p c m d P o x n y AP p c m d Aln o p gt AL x m n y V x m n y AL x m n y gt A z m y Axiom 9 An object x may not neglect an attribute definition in one of its classes Va y p c m d In x c A Alx m y A P p c m d gt Axioms 10 11 12 The isa relation is a partial order on the object identifiers V cIn c Obj gt Isa c c V e d e Isa c d A Isa d e Isa c e V c d Isa c d A Isa d c gt c d Axiom 13 Class membership of objects is inherited upwardly to the superclasses Y p x c d In x d A P p d isa c gt In x c Axiom 14 Attributes are typed by their attribute classes Vo l y p P o 1 y A In o p 3 c m d P p c m d A In x c A In y d 123 Axiom 15 Subclasses which define attributes with the same name as attributes of their superclasses must refine these attributes YV c d a1 a2 M f Isa d c A P a1 c m e A P a2 d m f Isa f e A Isa a2 a1 Axiom 16 If an attribute is a refinement subclass of another attribute then it must
64. B1SRC The load and save directories may also be the same Note that the save function will eventually over write the files that have been loaded at CBserver startup CBserver u nonpersistent load DB1SRC This command will start a non persistent CBserver and loads the module sources of directory DB1SRC Depending on your installation you need to replace the command name CBserver by either start CB server bat or startCBserver sh 75 Note that module sources do not contains the historic states of objects that are maintained with rollback times in the CBserver database Hence a persistent database is containing more information than the saved module tree and is also faster to start up compared to loading module sources Still the load save function offers a simple way to keep a textual representation synchronized with the evolving database state or to back up re load a database state The CBserver parameter db combines the function of d import export and views Hence all files will be accessed updated in the database directory 5 9 Server side materialization of query results Similar to the saving of module sources the CBserver parameter views enables the materialization of certain query results in the file system of the CBserver To do so one has to specify the queries to be materialized Only queries with a single parameter or with no parameter can be materialized The queries need to be listed with the module that contains t
65. Base cc user interface Details are in the installation guide distributed with ConceptBase cc 77 U untellmode controls the way how UNTELL is executed by the server The allowed values are verba tim and cleanup default In verbatim mode the UNTELL operation will only untell the facts directly described by the O Telos frame being submitted as argument In cleanup mode UNTELL will also try to remove the instantiation to the O Telos system classes Individual Attribute InstanceOf and IsA By doing so UNTELL behaves inverse to the TELL operation More details are explained in subsection 6 4 p portnr sets the TCP IP socket portnumber for client connections to the CBserver The value portnr must be between 2000 and 65535 If there is already a process using the portnumber the CBserver will abort The default value for the portnumber is 4001 port portnr is the same as p portnr Useful to avoid a harmless warning by the underlying SWI Prolog system which claims the parameter tag p for itself t tracemode sets the tracemode of the CBserver It is one of no minimal low high veryhigh The tracemode determines the amount of text displayed by the server during its execution The tracemode does not influence the function but is used for debugging The default tracemode is set to low display CBserver interface calls plus their answer The tracemode minimal will configure the CBserver to only trace the CBserver interface calls
66. IsA and e Attributes For each object type we provide a dialog to create this object type as shown in figure 8 11 This dialog is opened by clicking on one of the Create buttons in the tool bar or by selecting an Add item from the popup menu e g Add instance or Add subclass If there are some objects selected in the current 99 Create Object Create Object Source label Destination Name ObjectName GraphType DefaultindnidualGT Y Attr Class Show Attribute Instantiation ok Cancel Ok Create Object Create Object ObjectName in ObjectName is amp Class Class on cancel pea Figure 8 11 Create Object dialogs for Individuals Attributes Instantiations and Specializations frame then the object names of these objects will be inserted into the text fields of the dialog in the order they have been selected i e the first text field will contain the name of the object which has been selected first Furthermore if you move the cursor into a text field in the Create Object dialog and select an object in the graph then the name of this object will be inserted into the text field As changes might lead to a temporary inconsistent state of the database we do not execute the changes directly on the database They are stored in an internal buffer in the Graph Editor and executed when
67. N ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies either expressed or implied of the ConceptBase Team This license makes ConceptBase cc free software as promoted by the Free Software Foundation The license is compatible to the GNU Public License GPL and many other free license models You are wel come to contribute the ConceptBase cc project Join the ConceptBase Forum at http conceptbase sourceforge net CB Forum html to do so 10 Chapter 2 O Telos by ConceptBase cc ConceptBase cc is an implementation of the O Telos data model O Telos is derived from the knowledge representation language Telos as designed by Borgida Mylopoulos and others MBJK90 While Telos was geared more to its roots in artificial intelligence O Telos is more geared to database theory in par ticular to deductive databases Nevertheless O Telos is to a large degree compatible to the original Telos specification In some respects it generalizes Telos for example by removing the requirement to classify objects into the levels for tokens simple classes and meta classes In O Telos we have just five predefined objects see appendix on the ax
68. N Untell In x Employee IF i in EmployeeCounter DO Untell In i EmployeeCounter CALL decrement i il Tell In i1 EmployeeCounter end 63 The files CB_HOME examples ECArules counter 1pi gt contain the code for the Prolog predicates increment and decrement You must copy LPI files to the database directory before you start the ConceptBase server see also appendix F Note that all free variables of the PROLOG predicate must be bound in its call Furthermore the variables must be bound to object dentifiers if you want to use them in a Tell Untell or Ask action The effect of the increment and decrement procedures can also be achieved using the arithmetic expressions like 7 1 The simple solution with arithmetic expressions is available from http merkur informatik rwth aachen de pub bscw cgi d2773786 EmployeeCount sml txt The purpose of the example above is only to show that user defined PROLOG predicates can be called in the DO part of an ECArule You can define more interesting PROLOG predicates like sending an email to a user with content derived from the object base This requires however some knowledge of PROLOG and of the internal features of the ConceptBase server You should also note that the count of a class c can always and more correctly be computed by the function COUNT c That does even count inherited and deduced instances 4 2 3 Timestamps An often asked requirement in meta modeling a
69. O Telos skipped the valid time because it is virtually impossible to have a tractable imple mentation when in interplays with deductive rules Earlier versions of ConceptBase until version 3 1 did however implement both time components 7Only objects that have a right open belief time shall be visible OByow This is due to the fact that the end time of an object can only be changed once namely when the object is untold The UNTELL operation can only have happened in the past when OByow is built 17 4 Ai x m 0 The object x has an explicit attribute o This attribute is instance of an attribute category with label m 5 x m n y orAL x m n y The object x has an attribution link labelled n to the object y The attribution has the category m 6 From p x The object p has source x 7 To p y The object p has destination y 8 Label p 1 The object p has label 1 If 1 is used as a variable it must be quantified over the class Label 9 P p x 1 y There is an object P p x 1 y in the object base OB y 10 Known p t The object p is known in OB since t i e an object P p x 1 y tt is part of the object base OB and t is the start time of tt The argument t is a string of the format tt millisecond yr mo d h min sec millisec It is regarded as an instance of the class TransactionTime 11 Terminated p t The object p is unknown in OB after t i e an object P p x 1 y tt is part of the object base OB and t i
70. Objektbanken Dissertation Universitat Passau Germany 113 JGJ 95 JIM 09 JIN 98 JIQV99 JIR88 JJR90 JJS 99 JMSV90 JQC 00 JOJ98 MaPr99 MBJK90 NJJ 96 Quix96 QSJ02 RaDh92 Jarke M Gallersdorfer R Jeusfeld M A Staudt M Eherer S ConceptBase A deductive object base for meta data management Journal of Intelligent Information Systems Vol 4 No 2 pp 167 192 March 1995 Jeusfeld M A Jarke M Mylopoulos J eds Metamodeling for Method Engineering Cambridge MA 2009 The MIT Press ISBN 10 0 262 10108 4 Jeusfeld M A Jarke M Nissen H W Staudt M ConceptBase Managing Conceptual Models about Information Systems In Bernus P Mertins K Schmidt G eds Handbook on Architectures of Information Systems Springer Verlag pp 265 285 1998 Jarke M Jeusfeld M A Quix C Vassiliadis P Architecture and Quality for Data Ware houses An Extended Repository Approach Information Systems Vol 24 No 3 pp 229 253 1999 Jarke M Jeusfeld M Rose T A KBMS for database software evolution documentation of first ConceptBase prototype Report MIP 8819 Universitat Passau Germany 1988 Jarke M Jeusfeld M Rose T A software process data model for knowledge engineering in information systems Information Systems 15 1 85 116 1990 Jeusfeld M A Jarke M Staudt M Quix C List T Application Experie
71. Proposals for next generation databases BMS84 stem from three traditions e Databases This stream is best typified by extended relational and object oriented databases The main extension is the addition of complex domains shared sub objects and procedures to the data base Examples include Postgres Damokles Cactis Iris DASDBS and many others e Programming languages The main goal is to provide persistence and sharing to one or more pro gramming languages ideally orthogonal to the type systems of these languages Examples include the O system for imperative programming languages and typed versions of Prolog such as LOGIN or PROTOS L Knowledge representation Some of these systems aim at providing database service to AI appli cations others come from the tradition of deductive databases or semantic data models and aim at formal as well as practical support for general database systems and applications Examples in clude the deductive databases EKS LDL CORAL NAIL and the concept logic systems CLASSIC BACK and LOOM A sample of the former two groups of systems is described in TKDE90 whereas several prototypes of the latter are reported in SIGA91 Although a certain confluence can be observed these systems do not only differ in their background theories but also in their intended application domains The first group wants to support non standard applications such as the handling of complex engineering objects The second
72. T c class Since COUNT is also a function we support COUNT c as well to match the usual notation for function expressions The last query class is thus equivalent to 35 QueryClass EmployeeWithMoreRichCoworkersThanWilli isA Employee with constraint c2 COUNT RichCoworker this gt COUNT RichCoworker Willi end Since the COUNT function is frequently used ConceptBase provides the shortcut c for COUNT c Consequently the shortest form of the above query would be QueryClass EmployeeWithMoreRichCoworkersThanWilli isA Employee with constraint c2 RichCoworker this gt RichCoworker Willi end The shortcut is also applicable to the Union example above The expression below computes the numbers of instances of the set expression Union Intersec EmpMinSal 800 EmpMaxSal 1400 Manager The definitions for Union and Intersec can be found in the ConceptBase Forum at http merkur informatik rwth aachen de pub bscw cgi 896920 Besides COUNT ConceptBase supports aggregation function for finding the minimum maximum and average of a set Aggregation functions are not limitered to numerical domains For example one can define a function that returns an arbitrary instance of a class selectrnd in Function isA Proposition with parameter class Proposition end The membership constraint has to be provided as program code see chapter E A call selectrnd RichCoworker Willi work
73. Version selected the rollback time specified for queries default Now Current Module selected the data module to which TELL ASK operations are applied Current Time in time zone UTC GMT i e Coordinated Universal Time without summer time adjustment e Time in seconds used for the last transaction 8 1 4 Telos editor The Telos Editor is an editable text area where you can edit Telos frames The operations can be executed from the menu bar or the buttons in the tool bar Furthermore the text area has a popup menu on the right mouse button with the following items Display Instances Displays the instances of the currently marked object Load Object Loads the Telos frame of the currently marked object into the Telos editor 5The query can either be a query call referring to an existing query or a frame representing a new or existing query definition 89 View Object as Tree Opens the tree browser with the currently marked object as root Display in Graph Editor Shows the object in the current window of the graph editor The graph editor has to be started before menu Browse Clear Cut Copy Paste same as in the menu bar 8 1 5 History window The history window is part of the main Telos editor It stores all operations and their results so that they can later be used again The buttons scroll the history back or forward copy the text into the Telos editor or redo the operation in the history window see figure 8 2 If the
74. Y F can be referred to by the back slash operator Note that the vanilla versions of these characters are used to denote expressions in answer formats Hence we need to escape them by the backslash if they shall appear in the answer 3 2 5 Function patterns The substitution mechanism for answer formats recognizes patterns such as F exprl expr2 as function calls An example is the ASKquery construct from from section 3 2 6 The mechanism is however very general and can be used to realize almost arbitrary substititions The parentheses and the commas separating the arguments of F are parsed by ConceptBase and not placed on the output The following simple function patterns are pre defined 52 e From expr inserts the source object of expr The source object is computed by the predicate From x 0 of section 2 2 This pattern is useful for printing attributes ConceptBase will first apply pattern substitution to expr and then to the whole term From expr e To expr inserts the destination object of expr The destination object is computed by the predicate To x 0 of section 2 2 e Label expr inserts the label of the object referenced by expr The label is computed by the predicate Label x 1 of section 2 2 e Oid expr inserts the identifier of the object referenced by expr Note that the argument expr can be another pattern such as this Specifically the expression Oid this
75. ad operation of external models ConceptBase checks for syntactical and semantical correctness and reports all errors to the history window as it is done when updating the object base interactively using the editor This protocol field collects all operations and errors reported since the beginning of the session Historically we used the terms application or object base instead database We now believe that database is a much better term 10In nonpersistent update mode the database is actually copied to a temporary directory This copy will be removed when you shutdown the server 103 8 3 4 Displaying objects To display all instances of an object e g the class Employee we invoke the Display Instance facility by selecting the item Display Instances from the menu bar In the interaction window we specify Employee as object name The instances of the class Employee are then displayed see Figure 8 15 Display instances og Bd Telos Editor Cancel Figure 8 15 Display of Employee instances After selecting a displayed instance we can load the frame representation of an instance to the Telos Editor or display further instances 8 3 5 Browsing objects The Graph Editor is the preferred tool for browsing the objects managed by a ConceptBase server The Graph Editor is started by using the menu item Graph Editor from the Browse menu of CBiva Select Employe
76. ailable in the subdirectory bin of your ConceptBase installation directory 102 Start CBserver Parameters me CBserver output SAN A A gt Update mode nonpersistent 2 2 Port 4001 gt Multiuser mode disabled Database DOU conceptbase dh gt Loaded database tmp jeusfeld_s64927258_0_2051 gt Includes plugins Source Mode off z 3 ra gt This is ConceptBase cc CBserver V7 3 07 Tilburg 2011 02 24 T ieee oe minimal gt Copyright 1987 2011 by The ConceptBase Team All rights reserved Update Mode nonpersistent gt Distributed under a FreeBSD license See CB FreeBSD License txt for details Untell Mode cleanup Y gt MJeusfeld Tilburg University SOOOLE Tilburg Netherlands Multi user Mode disabled w gt MJarke C Quix RWTH Aachen Ahornstr 55 52056 Aachen Germany gt http conceptbase cc Predicate Typing strict v Cache Mode keep gt CBserver ready on host ig0246 serving port number 4001 ECA Mode safe w gt gt gt 2011 02 24 10 59 38 CALL ENROLL_ME ON JavaWorkbench jeusfeld ig0246 gt gt gt 2011 02 24 10 59 38 JavaWorkbench_s64927258_2 CALL GET_MODULE_CONTI Cancel 4 Ul E iD Stop Server Figure 8 13 Start CBserver dialog and CBserver output window L conecto CB server Host localhost ok cancel Figure 8 14 The connect to server dialog 8 3 3 Loading objects from external files The objects ma
77. aker M ed Special Issue on Database Prototype Systems IEEE Trans on Knowl edge and Data Engineering Vol 2 No 1 March 1990 Wing J M A Specifier s Introduction to Formal Methods IEEE Computer No 9 pp 8 24 Sept 1990 115 Appendix A Syntax Specifications A 1 Syntax specifications for Telos frames lt object gt gt lt objectname gt lt objectname gt lt inspec gt lt isaspec gt lt withspec gt lt endspec gt lt objectname gt lt inspec gt lt isaspec gt lt withspec gt lt endspec gt lt objectname gt gt lt objectname gt lt label gt lt bindings gt lt objectname gt SELECTOR1 lt label gt lt objectname gt SELECTOR2 lt objectname gt lt bindings gt gt lt empty gt lt bindinglist gt lt bindinglist gt gt lt singlebinding gt lt bindinglist gt lt singlebinding gt lt singlebinding gt gt lt objectname gt lt label gt lt label gt lt objectname gt lt inspec gt gt lt empty gt in lt classlist gt lt isaspec gt gt lt empty gt isA lt classlist gt lt classlist gt gt lt objectname gt lt objectname gt lt classlist gt lt withspec gt gt lt empty gt with lt decllist gt lt decllist gt gt lt empty gt lt declaration gt lt decllist gt lt declaration gt lt declaration gt gt lt attrcatlist gt lt proplist gt lt attrcatlist gt gt lt
78. al types For the standard objects there are a number of predefined graphical types There are contained in the graphical palette Default JavaPalette which is used by default by the Graph Editor type of object graphical type style Individuals DefaultIndividualGT gray box Links DefaultLinkGT thin black line with label InstanceOf DefaultInstanceOfGT green line without label IsA DefaultisAGT blue line without label Attribute DefaultAttributeGT black line with label Class ClassGT turquoise box SimpleClass SimpleClassGT pink oval MetaClass MetaClassGT light blue oval MetametaClass MetametaGT bright green oval QueryClass QueryClassGT red oval Implicit In ImplicitInstanceOfGT dashed green line Implicit IsA ImplicitlsAGT dashed blue line Implicit Attribute ImplicitAttributeGT dashed black line The object DefaultJavaPalette has also some rules which define the default relationship be tween objects and graphical types e g all instances of Class have the graphical type ClassGT C 3 Customizing the graphical types To support the user in defining his own graphical types we provide some examples and documentation of the properties There are two ways to customize the graphical types e Defining new graphical types with different properties using the provided implementations i5 cb graph cbeditor CBIndividual and i5 cb graph cbeditor CBLink e Defining new graphical types with
79. alid Telos Objects The Graph Editor can validate objects that are currently shown in the graph i e it checks whether the object is still valid in the database or it is has already been removed see Current Connection menu If you select Mark here then the objects will be marked with a red cross as invalid Remove from display instantly will remove the objects directly from the view Popup Menu These options control the behaviour of the Popup Menu see section 8 2 5 The delay is the time in milliseconds an item of the popup menu has to be selected before the submenu is shown Note that the construction of a submenu might require a query to the ConceptBase server If the option Popup Menu blocks while waiting for server is activated then the editor will block the UI while it waits for an answer of the ConceptBase server Otherwise the query to the server will be executed in a separate thread and interaction with the UI will be possible If you have the problem that some submenus are still shown after you have used the popup menu set the delay to 0 and activate the option Popup Menu blocks while waiting for server View menu The graph editor has an experimental layout algorithm that may be useful to reorganize the layout of a complex graph The heuristic of the layout algorithm is rather simple and does not minimize link crossings Enable automatic layout Call a layout algorithm everytime the graph is changed e g by
80. also refine the source and destination components V c d a1 a2 M1 M2 6 f Isa az a1 A P a1 c m1 e A Plaz d ma f gt Isa d c A Isa f e Axiom 17 For any object there is always a unique smallest attribute class with a given label m V T M Y C d Q1 Q2 f Un z c A In x d A P ax C M e A P az d m f 39 43 h In x g A Pas g m h A Isa g c A Isa g d Axioms 18 22 Membership to the builtin classes is determined by the object s format Yo 2 l y P o x 1 y In o Obj Vo l Plo o l 0 A l in A L isa In o Indiv Vo x c P o 2 in c 04 x A o 4c gt In o Inst Vo c d Plo c isa d A 0 4c A 0 4 d amp In o Spec VYo az l y Plo 2 l y 042 A oA y A LF in A l isa gt In o Attr Axiom 23 Any object falls into one of the four builtin classes V o In o Obj In o Indiv V In o Inst V In o Spec V In o Attr Axioms 24 28 There are five builtin classes P 0bj 0bj Proposition Ob7 P Indiv Indiv Individual Indiv P Attr Obj attribute 4 0b5 P Inst 0bj InstanceOf 0b P Spec 0bj ISA 0bj e DN No Axiom 29 Objects must be known before they are referenced The operator lt is a predefined total order on the set of identifiers Vo z l y P o x 1 y x lt 0 A y 30 Axioms 30 31 axiom schemas For any object P p c m d in the extensional object base we have two formulas for rewriting t
81. an object into the Telos editor View Object as Tree Opens a new window and shows the object in tree browser Browse New Telos Editor Opens a new Telos editor see section 8 1 4 Display Instances Opens the display instances dialog see section 8 1 6 Frame Browser Opens the frame browser window see section 8 1 7 Display Queries Shows all queries stored in the current database and provides a facility to call these queries see section 8 1 8 Query Editor Opens the query editor see section 8 1 9 Graph Editor Opens the CB Editor graphical browser see section 8 2 If the interface is con nected to a server the graph editor will also establish a connection to this server and ask for the graphical palette the initial object to be shown and the module context see section 5 Otherwise the graph editor will start with no connection Options Set Timeout Set the number of milliseconds the user interface waits for a response of the server Select Module Select the current module see section 5 Select Version Select or create a new version A version is a special object that represents the state of an object base at a specific time By default all queries are evaluated on the current state of the object base version Now By selecting another version queries are evaluated wrt to a previous state of the object base Pre Parse Telos Frames If enabled the user interface parses the contents of a Telos editor before it
82. ance Class SuperClass SubClass Attribute Individual These menu items will open the Create Object dialog where you can specify new objects that should be created in the database Note that these modifications are not performed directly on the database The editor will collect all modifications and send them to the ConceptBase server when you click on the Commit button See section 8 2 6 for more details Delete object from database This operation will delete the object from the database As for the insertion of objects before the modification will be send to the server when you click on the Commit button Note that this operation has an effect on the database in contrast to the next operation Hide object from view The object will be removed from the current view This operation has no effect on the database 1 e the object will not be deleted from the database Display in Workbench This operation will load the frame of the object into the Telos editor e Show in new Frame A new internal window within the Graph Editor will be shown and the selected object will be shown in the new window 8 2 6 Editing of Telos objects The Graph Editor supports also the creation and deletion of Telos objects A Telos object in the context of the Graph Editor is a proposition as described in chapter 2 As described there there are four types of Telos objects e Individuals e Instantiations InstanceOf e Specializations
83. and specialization links find_incoming links_simple Same as before but without the parameter category find_outgoing_links Lists the links that come out of ob jname and are instance of category Note that all types of links are returned including attributes instance of links and specialization links find_outgoing_links_simple Same as before but without the parameter category get links2 Return the links between src and dst get_links3 Return the links between src and dst that are instance of cat E 1 5 Other queries find_object This query just returns the object given as parameter ob jname if it exists Thus it can be used to check whether ob jname exists but there is a builtin query exists which does the same The query is mainly useful in combination with a user defined answer format e g the Graph Editor is using this query to retrieve the graphical representation of the object AvailableVersions Lists the instances of Version with the time since when they are know This query is used by the user interface to use a different rollback time Options gt Select Version listModule Lists the the content of a module as Telos frames see also section 5 7 E 2 Functions Functions may also be used within other queries You may define your own functions see section 2 5 141 E 2 1 Computation and counting COUNT counts the instances of a class this may be also a query class SUM computes the sum of the instances
84. arameter is represented by two arguments one for the input parameter itself and a second as a placeholder of the type of the input parameter The second clause tells the new function as Telos object so that it can be used like any other Telos function For technical reasons the tell clause may not span over more than 5 lines Use long lines if the object to be defined is large If you just want to invoke the procedure defined in an LPI plugin via the CALL clause of an active tule you do not need to include a tell clause Consider for example the SENDMAIL plugin from http merkur informatik rwth aachen de pub bscw cgi 2269675 In all cases you need to be very careful with testing your code Only use this feature for functions that cannot be realized by a regular query class or by active rules LPI code has the full expressiveness of a programming language Program errors may lead to crashes of the CBserver or to infinite loops or to harmful behavior such as deletion of files Query classes deductive rules and integrity constraints can never loop infinitely and can to the best of our knowledge only produce answer not changes to your file system or interact with the operating system Active rules could loop infinitely but also shall not change your file system and shall not interact with the operating system unless you call such code explicitely in the active rule You can disable the loading of LPI plugins with the otherwisely undocumente
85. arantee that all variables are bound at call time Tabled evaluation is for example implemented in the XSB System http xsb sourceforge net 6 3 Database persistency The default update mode is persistent In persistent mode all changes to the database are written to the file system at the directory specified in the parameter d Persistent mode is suitable when a CBserver runs for a longer period of time and is directly updated by application programs Typically the class and meta class level are then left unchanged though ConceptBase cc has in principal no restriction on this If ConceptBase cc is used for testing and modeling purposes the update mode nonpersistent is an interesting alternative We describe two scenarios Scenario 1 Single user Modeling When a user needs to model a certain application domain with classes and meta classes she usually works with external Telos files aka source models file extension sml These files can include comments like usual with program source code The recommended mode here is u nonpersistent without specifying a database The user can load the source models into such a non persistent server and make corrections to the source files in case of errors or design changes Here ConceptBase is mostly used to check and analyze the models Scenario 2 Assignments Assume that a teacher wants students to exercise a certain modelling task using ConceptBase cc Then she would prep
86. are some Telos files with necessary definitions e g some meta classes and load them into a persistent ConceptBase server After that she can restart the Concept Base server in non persistent mode on the same database created before Student can then work on their extensions while the state of the database can easily be set back to the original state defined by the teacher The module system of ConceptBase cc can be used to support multiple students to work on the same server without interfering with each other The second scenario might also be useful in modeling If there are some parts that are regarded as stable the modeller can decide to make them persistent and only add modify those Telos models that are still subject to change In particular for large Telos models this strategy saves time If ConceptBase cc is used in a multi user setting then one can combine the update mode with the module feature see section 5 In this scenario multiple users access the same CBserver A common super module e g the root module System carries the common objects of the users Each user can be assigned to her own hown module a sub module of the common super module and create and update objects in this workspace without interfering with other users If several groups of users shall share their definitions then they would be assigned to the same home module The home module may have sub modules for testing and releasing definitions By employing access righ
87. artment In general the term object attrcat refers to the set of attribute values of object in the attribute category attrcat This path expressions may be extended to any length e g John dept head refers to all managers of departments in which John is working A second shortcut is the explicit enumeration of allowed attribute values The following view retrieves all employees who work in the same department as John and earn 10000 15000 or 20000 Euro View EmpDept2 isA Employee with retrieved_attribute 37 dept John dept salary 10000 15000 20000 end As mentioned before inner frames use the same syntax as normal frames You can also specify constraints in inner frames which refer to the object of an outer frame View EmpDept_likes_head isA Employee with retrieved_attribute partof dept Department with retrieved_attribute partof head Manager with constraint c A this likes this dept head end end end The rule for using the variable this in nested views is that it always refers the object of the main view in this case an employee Objects of the nested views can be referred by this label where label is the corresponding attribute name of the nested view In the example we want to express that the employees must like their bosses Because the inner view for managers is already part of the nested view for departments we must use the double colon twice this dept refers to t
88. arule the other attributes are optional The language for ECAassertions is a extension of the assertion language it is specified as text between signs in the same way as rules and constraints 4 1 1 ECAassertion An ECAassertion has the following structure the syntax is described in section A 3 x1 x2 C1 y1 C2 ON event IF condition DO actionl action2 ELSE action3 The ELSE part is optional The first line contains the declaration of all variables used in the ECAasser tion The specified classes of the variables here C1 and C2 are only used for compilation of the rule during the evaluation of the rule it is not tested if the variables are instances of the specified classes If necessary the include predicates like In z Class in the IF part of the ECArule The variables can occur in the ON IF DO and ELSE part of the ECArule 4 1 2 Events Possible events are the insertion Tell or deletion Untell of attributes A instantiation links In or specialization links Isa For example 1f the rule should be executed if an object is inserted as instance of Class then the event statement is Tell In x Class Furthermore an event may be a query e g if you specify the event Ask find_instances Class class the ECA rule is executed before the evaluation of the query find_instances with the parameter Class Potential updates to the database vaused by the ECa rules will be persistent i e in such cases an A
89. ary are 14 P mary mary mary mary P E1 mary instanceof M P E3 mary hername Mary Smith P E4 E3 instanceof 3 P E5 mary earns 15000 P REG E5 xinstanceof 4 P E7 mary advises PR P E8 E7 xinstanceof 5 P E10 mary currentdept RD P E11 E10 instanceof 5 The attribute categories name salary and dept must be defined in one of the classes of mary In this case mary is also instance of Employee due to the following axiom which defines the inheritance of class membership in O Telos and hence can instantiate these attributes Specialization axiom axiom 13 in appendix B The destination superclass of a specialization inherits all instances of its source sub class An example is the specialization 8 all instances of Manager including mary are also instances of Employee O Telos enforces typing of the attribute values by the following general axiom Instantiation axiom axiom 14 in appendix B If p is a proposition that is instance of a proposition P then the source of p must be an instance of the source of P and the destination of p must be an instance of the destination of P For example Mary Smith must be an instance of String The individual mary also shows another feature attribute classes specified at the class level do not
90. as been implemented by the LPI plugin The LPI code would then look similar to the code in SYSTEM SWL builtin and you must have defined an instance of Built inQueryClass that matches the signature of the LPI code The call to the builtin query class may be enacted from the user interface or it may be included as an ASKquer y call in an instance of AnswerFormat Refer for more information to section 3 2 5 and to the directory Examples BuiltinQueries in your ConceptBase installation directory 2 By calling the implemented function as a CALL action of an active rule See section 4 2 2 for an example In that case there does not need to be a definition of a builtin query class or function to declare the signature of the procedure If the code of an LPI plugin realizes a function e g selecting the first instance of a class then you can use that function whereever functions are allowed As an example consider the definition of the LPI plugin selectfirst swi lpi from http merkur informatik rwth aachen de pub bscw cgi d2984654 selectfirst swi lpi txt compute_selectfirst _res _class _cl nonvar _class cbserver ask In _res _class tell selectfirst in Function isA Proposition with parameter class Proposition end The first clause is the Prolog code The predicate must start with the prefix compute followed by the name of the function The first argument is for the result of the function Subsequently each input p
91. ass The syntax new x in Class is supported as well and equivalent to the use of the backward apostrophe Note that only conditions of ECA rules can see intermediate database states 1 An example for a quantified sub expressions is not exists y D x m y 58 4 1 4 Actions Actions are specified in a comma separated list The syntax is similar to that one of events except that you can also ask queries Ask and call Prolog predicates CALL The standards actions are as follows Tell predicate The predicate fact is told to the system The predicate must be either an attribution instantiation or specialization predicate All arguments of the predicate must be bound at execution time of the action Untell predicate The predicate fact is untold from the system Retell predicate Old facts are first untold and then the new predicate fact is told See below for restric tions Ask predicate The predicate is evaluated possibly binding free variables Note that this action can fail if the predicate is not true in the database CALL proc The Prolog predicate matching procedure is called This can bind free variables You can define your own Prolog code as CBserver plugin Raise query The query call query is raised as event The query is not evaluated This action can be used to trigger other ECArules that have a matching Ask event All parameters should be bound The query may not be a builtin query class or function no
92. at has been told before should remove the frame completely This is however not the case for the following reasons e An O Telos frame being argument of a TELL or UNTELL operation is not necessarily all the infor mation about an object but just some e Other objects might refer to an object told previously An UNTELL operation would then be rejected to preserve referential integrity e ConceptBase cc adds instantiation to the builtin classes Individual Attribute Instance Of and IsA depending on the type of the object The last reason is most significant in preventing symmetry As an example consider the O Telos frame referred to as frame 1 bill in Employee with name bname William end ConceptBase cc will recognize that bi11 is an individual and that bil1 bname is an attribute This information is attached internally to the P facts more precisely it is derivable from the structure of the corresponding P facts When you ASK the system for the frame of bi11 after the TELL operation on frame 1 you will get frame 2 Individual bill in Employee with attribute name bname William end Hence the instatiation to the four builtin classes is added to the frame If we submit the original frame 1 to an UNTELL operation ConceptBase cc assumes by default that only two facts should be untold 1 The instantiation of bill to Employee 2 The instantiation of the attribute bi11 bname to its attribute cat
93. ated and initialized with the O Telos pre defined objects A database is maintained as a directory The parameter is mandatory except when the update mode is set to nonpersistent see below You cannot start two concurrent servers which use the same database directory To avoid this case a file OB lock is created in the database directory when the first server is started If the server crashes during its execution the file OB Lock will still exist in the directory Before you restart the server you might have to remove this file manually db dbir Like d but also sets the load save views directories to dbdir i e the CBserver will automat ically maintain the module sources in dbdir and also materialize the selected queries in the same directory See section 5 9 for details u updatemode controls update persistency The allowed values are persistent and nonpersi stent If no database is provided by parameter d then the default update mode is set to non persistent Otherwise the default is persistent In nonpersistent mode all updates are lost after the ConceptBase server is stopped In persistent mode updates are stored in the files of the database and will be available for future sessions l There are two other ways to start the ConceptBase cc server CBserver One is for starting the CBserver from a mobile medium without prior installation on the host computer and the second one is to start the CBserver from within the Concept
94. ation of an external graphical presentation for Concept Base objects The graphical type is declared using a special pre defined attribute category An application program then uses this information to determine the graphical presentation of an object The next subsection introduces the basic concepts behind graphical types while section C 2 presents the standard graphical type definitions for the ConceptBase Graph Editor Section C 3 describes the definition of application specific types C 1 The graphical type model A specific graphical type is defined as an instance of the object GraphicalType For the new Graph Editor implemented in Java this class has been specialized in a class JavaGraphicalType Instances of this class specify a graphical represenation of an object by defining graphical attributes such as shape color line thickness font etc Since the actual attributes and their admissible value depend on the used visualization tool the definition of GraphicalType looks very simple GraphicalType in Class end The declaration of a graphical type for a concrete object is done by using the attribute grapht ype which is defined for Proposition and therefore available for all objects Proposition with attribute graphtype GraphicalType end The attribute can be defined explicitely for an object or can be specified by using a deductive rule see section C 2 for an example For the Graph Editor application included in the usage enviro
95. bel gt lt restriction gt SELECTORB lt selectExpB2 gt lt restriction gt SELECTORB lt restriction gt n n gt lt label gt lt label gt lt label gt lt selectExpA gt lt label gt lt selectExpB gt lt label gt lt objList gt gt lt objectname gt lt objList gt lt objectname gt A 3 Syntax of active rules The event condition and actions of an ECArule are specified as a special assertion Therefore the syntax is an extension of the normal assertion language shown in the section before lt ecarule gt lt ecaevent gt lt eventop gt lt ecacondition gt lt condformula gt lt actionlist gt gt lt variableBindList gt ON lt ecaevent gt IF lt ecacondition gt DO lt actionlist gt lt optelseaction gt lt eventop gt lt literal gt lt eventop gt lt literal gt Ask lt literalArg gt Ask lt literalArg gt Tell Untell lt condformula gt true false lt literal gt not lt condformula gt lt condformula gt and lt condformula gt lt condformula gt or lt condformula gt lt condformula gt lt action gt lt actionlist gt lt action gt 119 lt action gt gt lt actionop gt lt literal gt lt actionop gt lt literal gt noop reject lt actionop gt gt Tell Untell Retell Ask CALL lt optelseaction gt gt ELSE lt actionlist gt lt
96. bject in O Telos can be uniquely referenced in the frame syntax mary learns gt Employee salary with comment coml This is a comment to an instantiation between attributes end mary learns gt Employee salary coml with comment com2 This is a comment to the the previous comment attribute end Figure 2 1 shows as the second view on propositions the graphical semantic network representation of mary and her relationships to the other example objects gt attribute Class mu Proposition div 4 ES SimpleClass salary p Integer 4 Employee _ name 4 dept E 7 Sie String A boss ES ar ti he j Manager epartmen 4 b CEA Y PR Token advises l R amp D mary currentdept earns 15000 hername Mary Smith Figure 2 1 Graph representing the example proposition network Individual objects are denoted as nodes of the graph instantiation specialization and attribute rela tionships are represented as dotted shaded and labelled directed arcs between their source and destination components 16 O Telos propositions have a temporal component the belief time The belief time of a proposition is not assigned by the user but by the system at the transaction time of an update TELL or UNTELL Con ceptBase uses right open and closed predef
97. bound to a class with a large extension the re writing will also yield a large set of generated formulas Meta formulas allow to specify assertions involving objects from different levels and hence significantly improve flexibility of O Telos models An example for the usage of meta formulas can be found in the appendix D 2 where the enforcement of constraints in ER diagrams is solved in an elegant way As instructional example assume we want to define that a certain attribute category M is transitive ie if x M y and y M z then x M z shall hold Many attribute categories are supposed to be transitive for example the ancestor relation of persons or the connection relation between cities in a railway network The following meta formula defines transitivity once and forever Proposition in Class with attribute transitive Proposition rule trans_R forall x y z M VAR AC Proposition transitive C Proposition P AC C M C and x in C and y in C and z in C and x M y and y M z gt x Mz end The rule is a meta formula because C and M are meta variables In this case one can re write the formula by replacing all possible fillers for AC i e by the instances of Proposition transitive A filler for AC will determine fillers for C and M since the first argument of a proposition P AC C M C 1s identifying the proposition As a consequence one can define the ancestor relation to be transitive by simply telling Person i
98. button from the ConceptBase Workbench window see Figure 8 20 Now we add an additional attribute e g education to the class Employee for the description of the Telos syntax see Appendix A We have added the line education String as shown in figure 8 21 To demonstrate error reports from the ConceptBaseWorkbench and how to correct them we have made mistakes in the syntax notation of the added attribute By clicking the left mouse button on the Tell icon the content of the editor is told to the ConceptBase server Syntactical and semantical correctness is checked and the detected errors are reported to the Protocol field The report resulting from our mistakes by specifying the new attribute is also shown in figure 8 21 Note that this syntax error would have been already detected at the client side without interaction with the server if we would have enabled the option Pre parse Telos Frames in the options menu 106 fF localhost4001 Figure 8 19 The graph showing implicit instantiation and attribute links We correct the error by adding a semicolon to the previous line and choose the Tell symbol again This time since there are no further mistakes the additional attribute is added to the class Employee Now we can choose again the item Outgoing Attributes from the popup of the Graph Editor window for the node Employee If we select Show all attributes of the attribute class Attribute the new at
99. can be the same computer for single user scenarios Note that a firewall installed on the path between the client and the server machine might block remote access to a CBserver The default port number used for the communication between server and client is 4001 It can be set to another port number by a command line parameter The CBserver is by default multi user capable i e multiple clients can connect to the same CBserver This feature is by default disabled when you start the CBserver from within the user interface See section 6 for more details The standard ConceptBase cc client is CBiva see section 8 The distribution also contains a client CBshell that can be used to interaction with a ConceptBase server using a command shell window The CBshell client can also be used to run non interactive scripts e g for loading a sequence of files with concept definitions into the CBserver Access to a CBserver via a web interface is also supported Required software is made available via the ConceptBase Forum 1 4 Overview of this manual This manual provides detailed information about using ConceptBase cc Information about the installation procedure can be found in the Installation Guide in directory doc TechInfo New users are advised to follow the installation guide for getting the system started and then to work through the ConceptBase cc Tutorial More information about the knowledge representation mechanisms the applications and the 2C
100. cking in programming languages that demands a strong relationship between formulas and the knowledge base Predicate typing condition 1 Each constant arguments that are not variables in a formula F must be the name of an existing object in the O Telos object base or it is a constant of the builtin classes Integer Real or String 2 For each attribution predicate x m y or Ai x m o resp occuring in a formula there must be a unique attribute labelled m of some class c of x in the knowledge base the so called concerned class 3 For each instantiation predicate x in c the argument c must be a constant All instantiation and attribution predicates need to be typed according to the predicate typing condi tion Formally we don t assign types to such predicates but concerned classes Any instantiation predicate and any attribution predicate in a formula must have a unique concerned class It is determined as follows e The concerned class of an instantiation predicate x in c is the class c The argument c may not be a variable e The concerned class of attribution predicates x m y and Ai x m 0 is principally the most special attribute with label m of all classes of x The O Telos axioms listed in appendix B in par ticular axiom 17 make sure that there may not be more than one candidate attribute if x is the name of an existing object If x is a variable we demand that there is at most one candidate in the var
101. contains c6 DefaultIsAGT c7 DefaultInstanceOfGT c8 DefaultAttributeGT c14 EntityTypeGtype c15 RelationshipGtype cl6 InconsistentGtype end EntityType with rule EntityGTRule forall e EntityType A e graphtype EntityTypeGtype EntityGTMetaRule forall x VAR exists e EntityType In x e gt A x graphtype EntityTypeGtype end RelationshipType with rule RelationshipGTRule forall r RelationshipType A r graphtype RelationshipGtype RelationshipGTMetaRule forall x VAR exists r RelationshipType In x r gt A x graphtype RelationshipGtype end To activate the ER_GraphBrowserPalette select this graphical palette when you start the Graph Editor or make a new connection in the Graph Editor see section 8 2 Handling inconsistencies The necessary and single conditions on attributes from the previous section could also be expressed as deductive rule The difference is that 1f they are formulated as constraints every transaction violating the constraint would be rejected The definition of rules handling necessary and single enables the user to handle inconsistencies in his model The following example demonstrates this 136 concept in the context of our ER model The example defines rules handling the restriction of roles by the min max constraint This restriction is not implemented using constraints Instead a new Class Inconsi
102. ct are unique The frame syntax of O Telos groups the labels of propositions with common source o around the label of o The exact syntax is given in appendix A In this section we introduce it by modeling the employee example Employee in Class with attribute name String salary Integer dept Department boss Manager end Manager in Class isA Employee end 13 Department in Class with attribute head Manager end The label of the common source in the first frame is Employee It is declared as instance of the class Class and has four attributes The class Manager is a subclass of Employee Oid s preceded by in our examples are generated by the system This leads to the following set of propositions corresponding to the frames above The belief time inserted by the system is denoted by omission marks P E HE Employee E P 1 E xinstanceof Class P 3 E name String P 4 E salary tinteger P 5 E dept D P 6 E boss Past P M FM Manager M P 7 M instanceof Class P 8 M xisa E P D D Department D P 9 D xinstanceof Class P 10 D head M Instantiation to the pre defined class Individual is implicitly given by the structure of t
103. cts themselves provided that they have no other instantiations to classes except instantiation to the four builtin classes Individual Attribute InstanceOf and IsA Furthermore no other object may be linked to the object subject to be untold 6 5 Memory consumption and performance ConceptBase cc stores objects in a dedicated object store maintained in main memory A P fact P o x n y consumes about 800 bytes of main memory That means that one can store roughly 1 million P facts in 1 GB of main memory A typical Telos frame is stored with roughly 10 P facts Hence 1 GB of main memory allows you to store around 100 000 Telos frames On 32 bit CPUs this results in a maximum of roughly 400 000 frames that can fit into 4 GB of addressible main memory This restriction virtually vanishes with 64 bit CPUs A single TELL UNTELL operation submitted to the CBserver should not contain more than about 2000 frames at about 5 attributes per frame Otherwise the compiler can run out of stack memory The raw performance of the object store i e the time needed to reconstruct a frame for a given object identifier is virtually independent from the number of P facts that it stores However if you have defined many rules or integrity constraints the performance may well degrade significantly with the number of stored P facts The same holds for queries We tested the response times for standard queries such as computing the transitive closure in relation
104. current operation is an ASK then a single click on the copy button will copy the query to the Telos Editor and a double click will copy the result of the query The size of the history window can be reduced by using the slider bar between the Telos editor and the history window Number and type of operation 1 AA Go to previous Copy Text to Redo Go to next operation Telos Editor operation operation Figure 8 2 Buttons of the History Window 8 1 6 Display instances This dialog displays the instances of a class The class is entered in the text field When you hit return or press the OK button the instances of this class will displayed in the listbox If you double click on an item in the listbox the instances of this item will be displayed The frame of a selected item can be loaded into the Telos editor by clicking the Telos Editor button A history of already displayed classes is stored in the upper right selection list box The Cancel button closes the dialog 8 1 7 Frame browser The Frame Browser see figure 8 3 shows all information relevant to one object in one window The window contains several subwindows with list boxes that show super and subclasses the classes the instances attributes and objects refering this object In the center of the window a small window with the object itself is shown To view the attributes of the object you must first select the attribute category in the subwind
105. d CBserver option g nolpi The CBserver will then not load LPI plugins upon startup This option might be useful for debugging or for disabling loading LPI plugins that are configured in the Lib system sub directory of your ConceptBase installation F 3 Programming interface for the plug ins The CBserver plug ins need to interface to the functionalities of the CBserver the Prolog runtime and possibly the operating system To simplify the programming of the CBserver plug ins we document here the interface of the module coserver We assume that the code for the plug ins is written in SWI Prolog and the user is familiar with the SWI Prolog system cbserver ask Q Params A asks the query O with parameters Params to the CBserver The answer is returned as a Prolog atom in A Example coserver ask find classes bill objname A 145 cbserver ask Preds evaluates the predicates in list Preds The predicate can backtrack and will bind in case of success the free variables in Lits We currently support only the following predicates In A AL and Isa Example cbserver ask In X Employee A X salary 1000 cbserver askAll X Lits Set finds all objects X that satisfy the condition in Lit s and puts the result into the list Set A AL and Isa Example cbserver askAl11 X In X Employee A X salary 1000 S cbserver tellFrames F tells all frames contained in the atom F The call will fail if there is any error in F Example cbse
106. d against substitution rules defined by the answers to a query A substitution rule has the form L gt R with the intended meaning that a substring L in a string is replaced by the substring R The object of a term substitution is a string in which terms may occur for example this is a string called a with aterm b Assume the substitution rules e a gt string no x e b gt that was subject to substitution e x 123 The derivation of a string with terms proceeds from left to right First the term occurence a is dealt with The next term in the string is then x which is evaluated to 123 Finally b is substituted and the result string is this is a string called string no 123 with a term that was subject to substitution We denote a single derivation step of a string S to a string S2 by S gt So It is defined when there occurs a substring L in Sy i e S1 V L W and a substitution rule L Rand S2 V R 4 W The substrings V and W may be empty A string S is called ground when no substition rule can be applied A sequence S S1 ue Sn is called a derivation of S A complete derivation of S ends with a ground string In our example the complete derivation is this is a string called a with a term b this is a string called string no x with a term b this is a string called string no 123 with a term that was subject to substitution An exception to the left to right rule are complex terms
107. defined both for integer and real values ConceptBase shall determine the type of a sub expression to deduce whether the to use the real valued or integer valued variant of the operation Examples of admissable arithmetic expressions are a 2x b 15 n m 3 Provided that a and b are integers the first expresssion is equivalent to the function shortcut IPLUS a IMULT 2 IMINUS b 15 and to the query call IPLUS a i1l IMULT 2 i1 IMINUS b i1 15 121 121 i2 The second arithmetic expression includes a division which in general results in a real number Hence the function shortcut for this expression is PLUS n DIV f m 3 The whole expression returns a real number 2 5 3 Example function calls and definitions 1 The following three variants all count the number of instances of Class COUNT Class class COUNT Class Class The result is an integer number e g 1159 The operator is a special shortcut for COUNT 2 The subsequent query sums up the salaries of an Employee SUM_Attribute bi11 ob3jname Employee salary attrcat SUM_Attribute Employee salary bi11 Note that the parameter label attrcat is sorted before objname for the function shortcut The result is returned as a real number even if the input numbers were integers 2 5001000000000e 04 You can also use functions also in query class to assign a value to a computed_attribute QueryClass EmployeesWithSumSalaries isA Em
108. der of paremeter labels to convert the shortcut form to the full form 33 2 3 2 Query classes and deductive integrity checking ConceptBase regards query classes as ordinary classes with the only exception that class membership cannot be postulated via a TELL but is derived via the class membership constraint formulated for the query class A consequence of this equal treatment is that a constraint formulated for an ordinary class can refer directly or indirectly to a query class e g Unit in Class with attribute sub Unit end BaseUnit in QueryClass isA Unit with constraint cl not exists s Unit sub From s this end SimpleUnit in Class isA Unit with constraint c forall s SimpleUnit s in BaseUnit end Here the constraint in the class SimpleUnit refers to the query class BaseUnit ConceptBase supports references to query classes without parameters in ordinary class constraints and rules A prerequisite is that the the query class is an instance of the builtin class MSFOLrule Mem bership to this builtin class is necessary to store the generated code for an integrity constraint or a rule that an integrity constraint might depend upon and to enable the creation of a dependency network between the query class and the integrity constraints There are two simple methods to achieve membership to MSFOLrule Method 1 Make sure that any query class is an instance of MSFOLrule This can simply be achieved be telling the fol
109. dule entry in the listbox sets the current module context to the selected module and lists all modules that are visible in this module i e its submodules and supermodules Change Module Current Module is oHome Change Figure 5 1 The module context selection window In our example you should get a window displaying the modules Master System Work and oHome in alphabetic order see Figure 5 1 Now double click the entry Work As a result the module context of the CBserver is set to the module Work As the Work module has got no nested modules there are no additional modules displayed in the listbox i e all modules that are visible in the oHome module are also visible in the Work module Alternatively you can specify the module context using the load model operation and placing a Sset module MODNAME inline command placed before the first Telos frame of a source model file MODNAME stands for the name of the module in which you wish to define the content of the source model file Module paths like System oHome Work are allowed as well Please note that only one inline command is allowed within one source model file Specifying module contexts using inline commands is a facility for automatically loading Telos frames of large applications which are spread over different modules without requiring the user to employ the select module function from CBiva Let s set the module context to Master and then TELL the
110. e section 2 2 for a list An argument of a predicate may be one the following e an object name If the object name starts with an upper case letter or includes special characters such as or it must be written in single quotes This also holds for string object e g a string must be written as a string e a predefined variable defined by the context of the query or rule If the query has a super class the variable this refers to the instances of this class If the query has parameters or computed attributes variables with the names of the parameters or computed attributes will be predefined 45 In a DatalogInRule the variable this refers to the instances of the concerned class In a DatalogAttrRule the variables src and dst refer to the source and destination object of the attribute Note that all predefined variables have to be prefixed with and must be encoded in single quotes e g this srce param e existential variables These variables must be declared in a special predicate vars list which has to be the first predicate of the code For example the predicate vars x y defines the variables x and y A query expression of the form query q may be also used as predicate or as second argument of an In predicate q may be any valid query expression e g just the name of a query class or a derive expression including the specification of parameters for example find_instances C
111. e 131 D2 A Telos modeling example ER diagrams 2 lt lt lt eS 131 Dal Tie esi co se ew ad eS Oe OE ete Bee aides ADH SS 131 D227 The use of meta formulas posos entes arre 133 D 2 3 Lim t tions and final remarks io 138 E Predefined Query Classes 140 E l Query classes and generic query classes co Re AG 140 E11 Tnstancesand classes oe eR bee eA ee he ee 140 E 1 2 Specializations and generalizations o e 140 ES AMS AA A AA ee a O as 141 ELA Links betweemebyects 6 is A dt 141 EF ARDEN QUERES so ob oe eka a Ge a rd e 141 ee TURCOS lec Se Bi A ii e de de 141 E21 Computation and counne lt lt gt e a peg e e oY Pe ok ee ERR 142 B22 Sinne mampulation cocoa a ee ewe 142 Ed B l mguery classes oo conside RR oS a BAG GE OR SO A a 143 F CBserver Plug Ins 144 El Denne eps sacs a oe so ee PERRO RR a es ER 144 E2 Ee pul gs o e Se ee AA A ee aR oS 144 F 3 Programming interface forthe plug ins ok ee ee RR 145 Chapter 1 Introduction ConceptBase is a deductive object base management system for meta databases Its data model is a con ceptual modeling language making it particularily well suited for design and modeling applications Its underlying data model allows to uniformly represent data classes meta classes meta meta classes etc yielding a powerful meta CASE environment The system has been used in projects ranging from de velopment support for data
112. e HTML file See http java sun com j2se 1 4 docs guide misc applet html for more information on the applet tag 111 8 5 Configuration file The configuration options are stored in a file CBjavaInterface in the home directory of the user on UNIX or Documents and Settings on Windows The settings are stored automatically on exit You can edit the file manually with a normal text editor It contains name value pairs in the format name value All options can also be modified by the user interface so it is not necessary to edit this file Options related to CBiva PathForLoadModel Path used by the load model dialog contains the most recent directory se lected in a dialog RecentConnections Comma separated list of recent connections in the format host port applies also to the graph editor PreParseTelosFrames Frames are be parsed on client side before sent to the server true false UseQueryResultWindow Use the query result window to display results of a query true false ConnectionTimeout Number of milliseconds the interface waits for a response of the server LPICall Enable LPI Call internal use only Options related to CB Graph Editor PathForLayout Path used by the dialog to store and load layouts contains the most recent direc tory selected in a dialog ComponentView Default view for the detailed representation in the graph editor might be frame or tree SaveLayoutWithGraphType Lay
113. e as the initial object to be shown in the Graph Editor After starting the Graph Editor it will open an internal frame connect it with the current server and load the Employee object The ConceptBase Graph Editor described in detail in section 8 2 allows you to display arbitrary objects from the current onceptBase server Then we select the Employee object and choose the Sub classes option from the context menu available via the right mouse button We choose to only display ex plicit subclasses from the submenu and select the Manager object The displayed graph is now expanded figure 8 16 Now we expand the node Manager a subclass of Employee by choosing the menu item Instances from the popup menu for Manager We select the menu item Show all to display all instances of Manager The resulting graph is shown in figure 8 17 Note that different object types are represented by different graphical objects The instances of Manager are shown only as grey rectangles because they are normal individual objects The nodes Manager Salesman Employee etc are shown as ovals since these nodes are instances of the system class SimpleClass see for a full description of graphical object semantics Appendix C One can move nodes and links by selecting a node or a link and then holding down the left mouse button while moving the cursor to a different position When the button is released the selected object will be located at the current position and
114. e name of the attribute link starting from x The object y is also called the value of the attribute e Proposition contains all propositions as instances i e the union of the instances of Indivi dual InstanceOf IsA and Attribute The term proposition is used as a synonym to object in O Telos Hence all explicit information in O Telos is represented as proposition ConceptBase allows to derive instantiation of an object to a class and attributes relations between objects This derived information has no object property i e it is not identified and it is not represented as a proposition Additional to the above predefined classes there are the builtin classes Class Integer Real and String Class contains all so called classes including itself as instances the only special property of Class is the definition of two attribute categories rule and constraint Hence instances of IWe will see in section 2 2 that the predicative language operates on a snapshot of the object base i e on those propositions that are believed at a specified reference time called rollback time This time is an interval The of the interval is the time when the object has been told created The end of the interval is either the time when the object was untold deleted or it is a special symbol Now indicating that the object is currently believed i e it is not deleted Strictly speaking we should better use the term predefined object or predefined propositi
115. e the answer representation There are three predefined answer representations FRAME returns the answers as Telos frames including retrieved and computed attributes LABEL returns only the names of the answer objects as a comma separated list Thirdly default lets the CBserver choose between LABEL for function calls and FRAME otherwise Besides these pre defined answer representations one can specify user defined answer formats In our case it is a parameterized answer format AFParameter somevalue somevar This means that the result of the query will be for matted according to the answer format AFParameter and the variable somevar will be replaced with somevalue The variable can be used like any other expression i e it must be enclosed in The following definition of AFParameter is an example how the parameter can be used in the pattern If the parameter is not specified the string somevar will not be replaced 55 Individual AFParameter in AnswerFormat with attribute head hd lt result gt attribute tail tl lt result gt attribute pattern poi lt object gt lt type gt somevar lt type gt lt name gt this lt name gt lt object gt end Note that you can use any answer format with or without parameters as answer representation in the ASK method 3 4 File type of answer formats The optional fileType attribute of answer formats is used by the server side materialization of query
116. easily install the complete system for all supported platforms on a 32 MB memory stick 1 6 License terms ConceptBase cc is distributed under a FreeBSD style copyright license since June 2009 Both binary and source code are available via http sourceforge net projects conceptbase files The FreeBSD style copyright license of ConceptBase cc reads like follows The ConceptBase cc Copyright Copyright 1987 2011 The ConceptBase Team All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution THIS SOFTWARE IS PROVIDED BY THE CONCEPTBASE TEAM AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE CONCEPTBASE TEAM OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND O
117. ed Attributes Computed Attributes dept Department csal Integer salary Integer Constraint Add Computed Attribute this salary csal and csal gt 50000 Telos Definition QueryClass HighSalary isA Employee with computed_attribute csal Integer constraint c this salary csal and csal gt 50000 end Figure 8 5 Query Editor In the right listbox you can add computed attributes The right mouse button brings up a popup menu which lets you add or delete an attribute In the text area below the two list boxes you can add a constraint in the usual CBQL syntax The constraint must be enclosed in signs The text area below shows the Telos definition of the query and is updated after every change you have made If your query is finished you can press the Ask query to test the query i e it is told temporarely and the results are shown in separate window If you are satisfied with the result you can press the Tell button to store the query in the object base 8 1 10 Tree browser The Tree browser see figure 8 6 displays the super classes classes and attributes of an object in a tree To start the tree browser you must mark an object in the Telos editor and select the item View Object as Tree from the popup menu or the Edit menu 92 Class N Individual gt jn O NISA gt Proposition gt Class SA N attribute Q N rule MSFOLrule gt in gt
118. ed as specialization of the salary attribute Any instance of the bonus attribute will then be an instance of the salary attribute via the usual class membership inheritance of O Telos For example mary in Manager with bonus bon1 10000 end shall make the following attribution facts true mary bonus bonl 10000 mary bonus 10000 A_e mary bonus 10000 mary salary bonl 10000 mary salary 10000 A_e mary salary 10000 mary attribute bonl 10000 mary attribute 10000 A_e mary attribute 10000 The third method to instantiate an explicit attribute to an attribute category is via a user defined rule We use the employee example again Employee in Class with attribute salary Integer premium Integer country String rule premrule forall e Employee prem Employee premium e country NL and Ai e premium prem gt prem in Employee salary end Now consider the following instances marijke in Employee with salary sal 50000 premium pr 3000 country ctr NL end 21 This would make the following attribution facts true marijke salary sal 50000 marijke salary 50000 A_e marijke salary 50000 arijke premium pr 3000 arijke premium 3000 A_e marijke premium 3000 arijke salary pr 3000 arijke salary 3000 A_e marijke salary 3000 marijke country ctr NL marijke country NL A_e marijke country NL 33 3 SEO Se ee ee ee es 3 Hence any expl
119. ed with a couple of shared libraries Under Linux 2 6 you should make sure that the following libraries are installed Most of them will be already present on a standard Linux installation linux gate so 1 libstdc so 6 libgmp so 3 librt so 1 libreadline so 5 libncursesw so 5 libm so 6 libdl so 2 ibgcc_s so 1 libpthread so 0 libc so 6 lib l1d linux so 2 libncurses so 5 The requirements for other Unix style platforms are similar Following is the list of shared libraries expected under Solaris 9 libnsl so 1 libsocket so 1 libstdct so 5 librt so 1 libdl so 1 libcurses so 1 libm so 1 libc so 1 libmp so 2 libgcc_s so 1 libaio so 1 libmd5 so 1 usr platform SUNW Ultra 5_10 lib libc_psr so 1 usr platform SUNW Ultra 5_10 lib libmd5_psr so 1 The installation of ConceptBase cc requires about 50 MB of free hard disk space The main memory requirements depend on the size of the object base loaded to the ConceptBase cc server The initial main memory footprint is just about 8 MB We recommend about 20 MB of free main memory for small appli cations and 200 MB and higher for large applications of ConceptBase cc The server can handle relatively large databases consisting of a few million objects Response times depend on the size of the database and even more on the structure of the query Since clients connect to a CBserver via Internet the server requires the TCP IP protocol to be available on both the client and the server machine
120. eger so that each solution of the restricted query class is also a solution of the more general one It should also be noted that HighSalary also could have been another query class This is the second way of query recombination Retrieved attributes and super classes already offer a simple way of querying a knowledge base pro jection and set intersection For more expressive queries there is an predicative extension the so called query constraint We use the same many sorted predicative language as in section 2 2 for deductive rules and integrity constraints and introduce a useful abbreviation 30 Let Q be a query class with a constraint F that contains the predefined variable this Then the query class is essentially an abbreviation for the two deduction rules forall this F gt Q this forall this Q this gt this in Q The deduction rules are generated by the query compiler and only listed here for discussing the meaning of a query class The variable this stands for any answer object of Q We call this also the answer variable The sub formula F is combined from the query constraint F and the structural properties of the query in particular the super classes and the retrieved attributes Each super class C of Q contributes a condition this in C to the sub formula F Each retrieved attribute like a D contributes a condition this a v and v in D toF Moreover each retrieved attribute add the new argument v to the p
121. egory Employee name As a consequence the object bi11 and its attribute continue to exist after the UNTELL on frame 1 It would look like frame 3 Individual bill with attribute bname William end 4ConceptBase takes the system time using timezone Coordinated Universal Time UTC of the computer on which it is running and rounds it to milliseconds The time is captured when the transaction is initiated i e all P facts told or untold in the transaction will use that transaction time 5 Deleted objects can however be recovered by setting the so called roll back time before an ASK transaction is issued Only ASK transaction are allowed on historical database state It makes little sense to update a historical state That would be falsifying the history of stored P facts 82 Only by untelling this frame 3 as a second operation or by untelling the completed frame 2 the object bill and its attribute bi11 bname shall be made historical This assymmetry of TELL and UNTELL is regarded by some ConceptBase cc users as unnatural be havior They expect that an UNTELL is also supposed to affect the objects themselves not just their instantiation to classes To support those users we provide a so called untell mode see parameter U in the list of CBserver command line parameters The untell mode is verbatim will cause ConceptBase cc to behave as explained above The mode cleanup default will take care to remove the obje
122. empty gt A 4 Terminal symbols ALPHANUM gt a zA z0 9 LABEL gt everything except S gt 1 newlines tabs everything enclosed in except and which must be escaped with everything enclosed in except and Y which must be escaped with NUMBER gt REAL INTEGER REAL gt 0 9 0 9 0 9 0 9 Ee 0 9 INTEGER Soe FA LOS Os BOOLEAN gt TRUE FALSE FUNCTOR gt From To A Ai AL In Isa Label P LT GT LE GE EQ NE IDENTICAL UNIFIES Known COMPSYMBOL gt lt gt lt gt lt gt INFIXSYMBOL gt COMPSYMBOL in isA SELECTOR1 et E A SELECTOR2 gt gt gt SELECTORB Es A 5 Syntax specifications for SML fragments This format is only internally used to represent Telos frames as Prolog terms It is included only for historical reasons lt SMLfragment gt gt SMLfragment lt what gt lt in_omega gt lt in gt lt isa gt lt with gt lt what gt gt what lt object gt 120 lt in_omega gt gt lt in gt gt lt isa gt gt lt with gt gt lt classlist gt gt lt attrdecllist gt gt lt attrdecllist gt attrdecl lt attrcategorylist gt in_omega nil in_omega lt classlist gt
123. en TILBURG SE UNIVERSITY ny ConceptBase cc User Manual Version 7 3 Jeusfeld Manfred Quix C Jarke M Publication date 2011 Link to publication Citation for published version APA Jeusfeld M A Quix C 8 Jarke M 2011 ConceptBase cc User Manual Version 7 3 Aachen RWTH Aachen Informatik 5 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and or other copyright owners and itis a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights Users may download and print one copy of any publication from the public portal for the purpose of private study or research You may not further distribute the material or use it for any profit making activity or commercial gain e You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details and we will remove access to the work immediately and investigate your claim Download date 17 dec 2015 ConceptBase cc ConceptBase cc User Manual Version 7 3 Manfred A Jeusfeld Christoph Quix Matthias Jarke Tilburg University Warandelaan 2 5037AB Tilburg Netherlands RWTH Aachen Ahornstr 55 52056 Aachen Germany 2011 02 25 Copyright C 1987 2011 by The ConceptBase Team All righ
124. en Query is a string of Telos frames including a query definition The answer representations are discussed in section 3 hypoAsk frames Query QueryFormat AnswerRep RollbackTime tells frames temporarily and asks a query Ipicall picall executes the LPI call only for debugging purposes prolog prologstatement executes the Prolog statement only for debugging purposes getErrorMessages gets error messages for the last transaction and prints them on stdout result completion result compares the given result with the last result which has been received this com mand hence can be used to check whether the CBserver produces the expected completion ok error and result use this command in combination with the option 1 setModule module changes the module context of this shell showAnswer print the last result on standard output this can be useful if you employ the CBserver as a generator in a shell pipe see Graphviz case below exit exits the shell also stops a server which has been started in this shell 9999 Command arguments with white space characters have to be enclosed in double quotes arguments may span multiple lines If an argument contains a string of the form PropName it will be replaced with the value of the corresponding Java property which may be defined using the D option of the Java Virtual Machine if the property is defined The CBshell utility can be used in Unix pipes to extract textual out
125. ent names Now objects with identical names can be stored in different modules without interferences As another application users can manage alternative conceptual models of the same domain in different modules The set of visible objects in a module context is not limited to the set of objects defined for the module The ConceptBase module concept permits to reuse existing objects from different modules via import and export interfaces Furthermore modules can be nested a nested module is only visible within the context of its father module Objects that are visible in a father module are visible and can be reused to all its child modules ConceptBase users can be assigned to so called home modules i e the module they start working with when registering with the ConceptBase server So called auto home modules force every user in her own module to further reduce potential unwanted interferences A flexible access control mechanism allows to define access rights of users simply by query classes defined either globally or locally to a module 5 1 Definition of modules A Module is a standard O Telos object which defines the content of a module Class Module with attribute contains Proposition end In ConceptBase a module is a container of objects Modules create a name space object names must be unique within one module but different modules can contain different objects with identical names Tell Untell and Ask operations w
126. ent typically leads to a binding of variables in the rule s IF and DO parts This binding is stored in the rule s representation within the work set The rules in the working set are sorted to reflect the priority settings of ECArules If two rules have no priority defined between them then the definition order is used to sort them older rules before newer rules Each rule r in the working set will then be processed as follows one after the other The rule processing depends on the mode of the ECArule in the working set If the mode is Immediate then the IF part is evaluated yielding all possible combinations of variables that make the IF part true If the answer set is empty then ConceptBase will call the ELSE actions of the ECArule Otherwise Con ceptBase will call the DO part for each variable combination determined in the previous step If the mode is ImmediateDeferred then ConceptBase will evaluate the IF part of the current rule like before Instead of calling the DO or ELSE part it will however put a term do r actions on a waiting queue Q The parameter r identifies the rule The parameter actions contains all instantiations of the DO part of r by the variable substitutions computed by the evaluation of the IF part of r If there are no such substitutions then actions is set to the ELSE part of r if existent Otherwise no actions would be appended to the wating queue If the mode is Deferred then ConceptBase will not immediate
127. eptBase cc 2 1 Frame and network representation cs orcos RE SR 22 Rules and COMMA oidor Oh ESE Sa de E A 221 Basie predicas A EY ee eS ER ee Ee Ree 22 2 Noms On atmbulOn ociosas bee eee ne Bods bee YE baw 2 2 3 Assigning attribute categories to explicit attributes 224 Reserved WOMS 04 4564 44504 A wee He ede ea dee eee 22 09 Comparison predicates 2 ope sapa BEARS ee Re ee 228 Typed MaS 2 05064 5 See als ea ee be ee ee eee 22 Semantic restrictions on formulas sas ced ie eG ed 22 8 Role and COSUDE go 5 Sek eS se k HE RR LLS Wem Onmass 6 66 oe Cet ets eh eee bes RA ees eA ES 2210 F rther object referentes gon e ek we RE Re 2 2 11 User definable error messages for integrity constraints Za Query casses po a a REE RE eRe RGSS Bae a RS 2 3 1 Query definitions versus query calls o o 2 3 2 Query classes and deductive integrity checking 2 33 Nested query calls and shortcuts gt os secre cee ee ee s Zon R fedguery calls ooo we RR A De aS 24 View COLI o e oe a oe a be eee eee ed 2 MUNDOS 2 2 24 56 44s g Lee es BR Eee A 25 1 F nchonsas special guernes osos sh ce wee AI 2 5 2 Shortcuts for function calls and functional expressions 2 5 3 Example function calls and definitions gt p lt lt 45 lt beh eR eS Zo Programmed Tumcnons fb ew eee eG ewe ES ewe 2 5 5 Recursive function definitions e e
128. er would then return an arbitrary instance of RichCoworker Willi worker Random functions can be useful in the context of active rules section 4 e g to initiate the firing of a rule with an arbitrary candidate out of the set of candidates The code for select rnd is accessible via the ConceptBase Forum at http merkur informatik rwth aachen de pub bscw cgi 1694234 2 3 4 Reified query calls You might want to memorize certain query calls that you want to call over and over again ConceptBase provides a built in class QueryCal1 which you can instantiate by such query calls as ordinary objects i e reified query calls The following example defines the class count as a query call object COUNT Class class in QueryCall end Of course you can ask the query call COUNT Class class without having told it as an object Reifying COUNT Class class additionally allows you to use it as an attribute of another object or to browse it with the graph editor Examples for query calls in particular for using integer intervals as class attributes are available in the CB Forum at http merkur informatik rwth aachen de pub bsew egi 2571997 36 2 4 View definitions The view language of ConceptBase is an extension of the ConceptBase Query Language CBQL Besides some extensions that allow an easier definition of queries views can also be nested to express n ary rela tionships between objects The system class View is defined as follows
129. ere can be meta classes meta meta classes meta meta meta classes etc 2 A class can have object from different meta class levels as instances This is in particular important for extending the capabilities of the O Telos language An example of a class that has objects from different levels as instances is Proposition it has all objects as instances 3 A user does not need to decide to which meta class level an object belongs Strict conformance to the membership to meta class levels can still be enforced by user definable integrity constraints As a user you don t work directly with propositions but with textual frame and graphical semantic networks views on them Both are not based on the oid s of objects but on their label components To guarantee a unique mapping we need the following naming axiom Naming axiom see also axioms 2 3 4 in appendix B 1 The label name of an individual object must be unique i e if two objects have the same label than they are the same 2 The label of an attribute must be unique within all attributes with a common source object 1 e no two explicit attributes of the same object can have the same label However two different objects can well have attributes sharing the same label 3 The source and destination of an instantiation object are unique i e between two objects x and y may be at most one explicit instantiation link 4 The source and destination of a specialization obje
130. et is also possible wrt to the usual security restrictions of applets The Graph Editor is integrated with CBiva i e Telos frames of objects shown in the Graph Editor can be loaded directly into a Telos editor and vice versa The Graph Editor implements a Multiple Document Interface MDI i e inside the main window several internal frames can be opened Each frame has a separate connection to a ConceptBase server Thus within a Graph Editor you can establish multiple connections to the same server or to different servers The communication with the ConceptBase server is done using standard ConceptBase queries and a special answer format For the presentation of objects the Graph Editor needs to know also the graphical type of an object which is included in the XML document This document is sent by the server as answer to a query Together with the caching techniques the use of XML reduces the communication between client and server The new Graph Editor supports also the concept of graphical types as the graphical browser in the previous releases of ConceptBase However the idea of different graphical types has been extended and 93 makes use of some dynamic features of the Java programming language e g dynamic loading and bind ing Figure 8 7 gives an overview of the ConceptBase Graph Editor Three internal windows have been opened the two windows on the left have been connected with the same server running on localhost port
131. express the recursive definition in the membership constraint of the function fib in Function isA Integer with parameter n Integer constraint 42 cfib n 0 and this 0 or n 1 and this 1 or n gt 1 and this fib n 1 fib n 2 end ConceptBase shall internally compile the disjunction into three formulas forall n this Integer n 0 and this 0 gt fib this forall n this Integer n 1 and this 1 gt fib this forall n this Integer n gt 1 and this fib n 1 fib n 2 gt fib this ConceptBase employs the magic cache query evaluator to evaluate the recursive function Thus the result of a function call fib n shall only be computed once and then re used in subsequent calls If the recursion is not inside a single function definition but rather a property of a set of function query definitions then you must use so called forward declarations They declare the signature of a func tion query before it is actually defined A good example is the computation of the length of the shortest path between two nodes spSet in GenericQueryClass isA Integer with parameter x Node y Node end sp in Function isA Integer with parameter x Node y Node constraint csp x y and this 0 or x nexttrans y and this MIN spSet x y 1 end spSet in GenericQueryClass isA Integer with parameter x Node y Node constraint csps exists xl Node x next x1 and this sp x1 y end Here the query
132. ext to Mjonny Mjonny in Module end Then he would set the module context to Mjonny define his rights management policy for example CB_Group with attribute groupMember CB_User permitted_read Resource permitted_write Resource owner_resource Resourc end CB_User isA CB_Group end CB_Group in Class with rule rrl forall p Resource u CB_User u owner_resource p gt u permitted_write p rr2 forall p Resource u CB_User u permitted_write p gt u permitted_read p rr3 forall u CB_User u groupMember u rr4 forall u CB_User p Resourc exists g CB_Group g groupMember u and g owner_resource p gt u owner_resource p rr5 forall u CB_User p Resourc 72 exists g CB_Group g groupMember u and g permitted_write p gt u permitted_write p rr6 forall u CB_User p Resourc exists g CB_Group g groupMember u and g permitted_read p gt u permitted_read p end GenericQueryClass CB_Permitted isA CB_User with parameter user CB_User res Resource op CB_Operation constraint cperm not exists u CB_User u owner_resource res and not u user or op in CB_ReadOperation and user permitted_read res or op in CB_WriteOperation and user permitted_write res and UNIFIES user this end In the above example access rights are granted to grou
133. ge in the style of deductive databases A complete formal definition can be found in JGJ 95 Jeus92 O Telos is viewed as a hybrid knowledge representation language integrat ing ideas from frame like concept description languages and deductive databases This hybrid character suggests a hypertext style combination of graphical semantic network views and textual frame repre sentations at the user interface Both O Telos views are based on the common logical representation so that they can be treated in a completely symmetrical way both for purposes of querying browsing and of editing manipulation This manual is integrated with the ConceptBase Forum The ConceptBase Forum is an Internet based workspace where ConceptBase developers and users share knowledge It contains numerous examples on how to solve certain modeling problems It is highly recommended to join the workspace More details are available at http conceptbase sourceforge net CB Forum html ConceptBase is mainly used for metamodeling and for engineering customized modeling languages The textbook JIM 09 Jeusfeld M A M Jarke and J Mylopoulos Metamodeling for Method Engineering Cambridge MA 2009 The MIT Press ISBN 10 0 262 10108 4 introduces into the topic and provides six in depth case studies ranging from requirements engineering to chemical device modeling The book and this user manual are complementary to each other 1 1 Background and history
134. ger dept Department boss Manager education String rule bossrule forall CIENIE Bilis col History Window Figure 8 21 Trying to add an attribute to the class Employee with the resulting error report We can tell this query so that it is stored in ConceptBase and we can reuse it later or we can just ask the query i e the query will told temporarily and evaluated If we ask the query the answer is displayed in the Telos Editor field as well as in the history window Figure 8 25 shows the ConceptBaseWorkbench containing the query class and the answer We can also execute this query from the Graph Editor From the menu Current connection we select Query to server A dialog we ask for the name of query class If we have told the example query we can type AngusEmployees in the text field and hit on the Submit Query The query will be evaluated and the objects in the result will be shown in the list box We can select the objects which should be added to the graph multiple selection with the Shift key is possible and click on the Show objects button The selected objects will be added to the graph however with no connection to existing objects 8 4 Usage as applet Both applications CBiva and CB Graph Editor can be used as an applet within a web browser with a plugin for JDK 1 4 To start the applications as applet you have to specify inside the applet class of the program For CBiva the applet clas
135. group aims at an easier programming environment for standard applications addition ally they emphasize the goal of making applications written in different languages interoperable The third group pursues as one of its goals the support for AI applications such as natural language understanding or expert systems However this may remain a fairly limited portion of the software market The reason why we became interested in this group of languages is therefore a slightly different one the important role we expect them to play in meta data management Meta data applications range from the uniform access to heterogeneous data sources to the coordination of design processes to the integration of heterogeneous information services in networked production chains whole enterprises or even trans national networks In these applications which are crucial for the huge integration tasks to be tackled in the 1990s the possibility not only to execute systems but also to reason formally about their structure and capabilities can be considered a competitive advantage over the other approaches ConceptBase has provided some validity to this claim by extensive usage experiments in several of the above areas 1 1 1 Telos and O Telos The language underlying ConceptBase Telos has been one of the earliest attempts to integrate deductive and object oriented data models Stan86 MBJK90 The O Telos Jeus92 dialect supported in Concept Base takes a conservative
136. gt CctExpB gt ration ct gt r lt propertylist gt lt propertyvalue gt lt classlist gt EXpB gt lt singlesubst gt lt selectexp gt gt gt l l substitute lt object gt specializ lt label gt lt label gt select lt selectexp gt select lt selectexp gt 122 lt label S SE lt label gt gt OR1 OR2 lt label gt lt selectexp gt Appendix B O Telos Axioms O Telos is the variant of Telos originally defined by John Mylopoulos Alex Borgida Manolis Koubarakis and others that is used by the ConceptBase system This list is the complete set of pre defined axioms of O Telos and thus defines the semantics of a O Telos database without user defined rules and constraints The subsequent axioms are written in a first order logic syntax but all can be converted to Datalog with negation though there is some choice in the conversion wrt mapping to rules or constraints Axiom 1 Object identifiers are unique Vo 11 l1 y1 12 l2 Y2 Plo 1 l1 Y1 A Plo 2 l2 yo gt 21 22 A l l2 A y1 y2 Axiom 2 The name of individual objects is unique V 01 02 1 P 01 01 1 01 A P 02 02 1 02 01 02 Axiom 3 Names of attributes are unique in conjunction with the source object Y 01 l y1 02 y2 P o1 2 1 y1 A P o2 2
137. gument O is the name of a query The arguments subst 1 subst 2 are parameter substitutions see section 2 3 The argument FRAME is the default answer format specified for the query Q It shall be overridden in case that query Q has itself an answer format Instead of FRAME the user can also specify any answer format in the ASKquery call even parameterized answer formats see below are allowed The effect of ASKquery in an answer format is that the above query call is evaluated and the AS Kquery expression is replaced by the complete answer to the query In terms of the substitution the following rule is applied ASKquery Q subst1 subst2 FRAME X where X is the result of the query call O subst1 subst2 after derivation of the arguments subst1 subst2 etc This sequencing is important since an ASKquery call can contain terms that are subject to substitution e g ASKquery MyQuery this catl paraml this xl x2 FRAME ConceptBase will always start to evaluate left to right and the innermost terms before evaluating the terms that contain inner terms Hence the derivation sequence is ASKquery MyQuery this cat1 paraml this x1 x2 FRAME gt ASKquery MyQuery alpha paraml this xl x2 FRAME 12 gt ASKquery MyQuery alpha paraml this name x2 FRAME rl gt ASKquery MyQuery alpha paraml smith x2 FRAME 13 gt ASKquery MyQuery alpha
138. h the suffix bim Ipi is intended to be used by a CBserver based on MasterProlog formerly BIM Prolog If the CBserver is based on SWI Prolog the server reads files with the suffix swi lpi Both Prolog Environments used a slightly different syntax which requires different implementations ConceptBase 7 0 only supports SWI Prolog hence providing the swi variant is sufficient 64 end This ECArule is executed when a new salary is assigned to an employee The condition checks if there exists already a value for the LastModified attribute If this is the case the attribute is deleted Except for deletion of this attribute the DO and the ELSE part of the rule are identical First we have to retrieve the transaction time of the new object es when it was inserted into the knowledge base t2 We have to use new in the ask operations because the object was not visible before the transaction started After that we can tell the new attribute Note that the transaction time is represented as string of the form tt year month day hour minute sec millisec We included this example rule to show that the Ask action can be used in both the DO and ELSE clauses of an ECArule A more elegant solution is however to do all querying inside the IF clause See the CB Forum at http merkur informatik rwth aachen de pub bscw cgi d2995330 ECA lastmodified2 cbs txt for an example 4 2 4 Simulation of Petri Nets ECArules are a powerful t
139. he In and A predicates The In is mapped to a unary predicate where the class name is forming part of the predicate name and the A predicates is mapped to a binary predicate that carries the identifier of the class of the attribute in its predicate name Internally user defined deductive rules that derive Jn and A predicates will also be rewritten accordingly This extends the choices for static stratification V o In o p gt In p o Vo 1 l y P o x l y Aln o p gt A plz y ConceptBase allows to add user defined rules and constraints The semantics of an O Telos database including such rules and constraints is the perfect model of the deductive database with the P o x l y as the only extensional predicate and all axioms and user defined rules constraints as deductive rules Note that integrity constraints can be rewritten to deductive rules deriving the predicate inconsistent This list of axioms is excerpted from M A Jeusfeld Anderungskontrolle in deduktiven Objektbanken Dissertation Universit t Passau Germany 1992 Available as Volume DISKI 19 from INFIX Verlag St Augustin Germany or viahttp merkur informatik rwth aachen de pub bscw cgi d340216 diski19 paf in German Axioms 19 21 have been corrected after Christoph Radig found an example that led to the undesired instantiation of an individual object to Inst or Spec respectively 124 Appendix C Graphical Types The concept of a graphical type enables the specific
140. he departments and this dept head refers to the managers If you reload the definition of a view into the Telos Editor the complex structure of it is lost During compilation of the view the view is translated into several classes and some additional contraints are generated so the resulting objects might look quite strange if you reload them 2 5 Functions Functions are special queries which have some input parameters and return at most one object as result for one set of input parameters Functions can either be user defined by a membership constraint like for regular query classes or they may be implemented by a PROLOG code which is defined either in the OB builtin file this file is part of every ConceptBase database or in a LPI file see also section 4 2 2 A couple of aggregation functions are predefined for counting summing up and computing the min imum maximum average Furthermore there are functions for arithmetic and string manipulation See section E 2 for the complete list Since functions are defined as regular Telos objects you can load their definition on the Telos editor of the ConceptBase User Interface Unlike as for user defined generic query classes you have to provide fillers for all parameters of a function We will refer to any query expression whose outer most query is a function as a functional expression The intrinsic property of a function is that it returns at most one return object This property all
141. he objects that match the query Example MyModule with saveView vi Ol v2 02 end You can also use deductive rules deriving the values for the saveView attribute The queries Q1 and Q2 need to be visible in the module MyModule The queries need to have an answer format section 3 defined for them attribute forQuery Assume that the query Q1 has the single parameter param C1 ConceptBase will then call the query 01 x param for each instance x of class C1 The result is stored in a file with name x in the directory specified with the views parameter The file type of the file is taken from the optional fileType attribute of the answer format of Q1 The default file type is txt The result of queries with no parameter is stored in files carrying the name of the query The materialization of query results is executed at the same events when the saving of module sources takes place i e at CBserver shutdown or when a client tool logs off the CBserver To enable the material ization you need to specify the target directory with the views option CBserver d MYDB views home meee MyViews You can also use the CBshell utility section 7 to extract the query results and materialize them on the client side This method is more flexible but you need to program the CBshell scripts for to extract all required views For example the CBshell script enrollMe alpha 4001 ask Ql x param OBJNAMES FRAME Now showAnswer exit
142. he three individual propositions named Employee Manager and Department Analogously the attributes 3 4 5 6 and 10 are automatically regarded as instances of the class Attribute The instances of Attribute are also called attribution objects or explicit attributes Propositions 1 2 7 and 9 are instances of the class Inst anceOf holding explicit instantiation objects and 8 is an instance of the class IsA explicit specialization objects Note that all relationships are declared by using the identifiers not the names of objects Thus Class denotes the identifier of the object Class etc The identifiers are maintained internally by ConceptBase s object store Externally the user refers to objects by their name A standard way to describe objects together with their classes subclasses and attributes is the frame syntax Frames are uniformly based on object names The next frames establish two departments labelled PR and RD and state that the individual object mary is an instance of the class Manager Mary has four attributes labelled hername earns advises and currentdept which are instances of the respective attribute classes of Employee with labels name salary and dept mary in Manager with name hername Mary Smith salary earns 15000 dept advises PR currentdept RD end PR in Department end RD in Department end The corresponding propositions for the frame describing m
143. he user of the registering client will automatically be defined as an instance of class CB_User The definition will be made in the context of the root module System 71 GenericQueryClass CB Permitted isA CB_User with parameter user CB_User res Resource op CB_Operation end A user is allowed to perform the operation op on the resource res iff the constraint of the query is satisfied Then user is returned as answer of the query If not the answer is nil equals empty set Some fundamental definitions are pre defined objects of ConceptBase Resource with end Module isA Resource end CB_Operation end CB_ReadOperation isA CB_Operation end CB_WriteOperation isA CB_Operation end TELL in CB_WriteOperation end ASK in CB_ReadOperation end Hence at least two operations TELL and ASK are pre defined symbolizing write and read accesses to a resource Modules are the prime examples of resources to be access protected Currently only access to them is monitored by the CBserver When a user wants to switch to anew module then she must at least have the permission to execute the operation ASK on it Otherwise the context switch is rejected This is the main protection scheme offered to module owners It is recommended to define the query class CB_ Permitted in the module that needs protection Assume that there is a user jonny who wants to protect his module Mjonny To do so he would first define the module and set the module cont
144. hether the formula applies to managers or to all employees The second clause of the predicate typing condition is closely related to multiple generalization instan tiation Suppose we add new classes Shop Guest and Guest Employee to the given class Employee Shop in Class end Guest in Class with attribute dept Shop end GuestEmployee in Class isA Guest Employee end The following formula refers to objects of class GuestEmployee and their dept attribute The prob lem is that two different attributes Employee dept and Guest dept apply as candidates for the predicate x dept PR forall x GuestEmployee x dept PR gt not x in Manager In order to solve this ambiguity we demand that in such cases a common subclass exists that defines an attribute dept which conforms to both definitions e g Shop in Class end GuestEmployee with attribute dept ShopDepartment end ShopDepartment in Class isA Shop Department end The third clause of the predicate typing condition is forbidding instantiation predicates with a variable in the class postion The restriction is a pre condition for an efficient implementation of the incremental 24 formula evaluator of ConceptBase Without a constant in the class position of x in c any update of the instances of any class matches the predicate Hence ConceptBase would need to re evaluate the for mula that contains the predicate Since any update TELL UNTELL
145. iable range of x and its superclasses If no class of x i e also no superclass of any class of x defines such an attribute and the CBserver has been started with the predicate typing mode extended then the concerned class is determined from the subclasses of the classes of x Theoretically one can choose the common superclass of all such attributes of subclasses of the classes of x if existent However ConceptBase currently demands that there must be a single such attribute in the subclass hierarchy Example The concerned class of e boss b in the SalaryBound constraint in subsection 2 2 8 is the Employee boss The class of variable e is Employee This is the most special superclass of itself and indeed defines the attribute Employee boss The purpose of the predicate typing condition is to allow ConceptBase to compile attribution predicates x m y to an internal form Adot cc x y that replaces the attribute label m by the object identifier cc of the concerned class This enourmously speeds up the computation of predicate extensions A similar effect is applicable to instantiation predicates Here the concerned class of x in c is c Another effect of the predicate typing condition is that certain semantically meaningless predicate occurrences are Since any object is an instance of Proposition ConceptBase will include this class when searching the concerned class of an attribution predicate 23 detected at compi
146. ibute labels occuring in an answer object Example for answer object A this attribute evaluates to Label11 label12 label21 this attribute lists all attribute values occuring in an answer object Example for answer object A this attribute evaluates to v11 v12 v21 this oid displays the internal object identifier of the answer object this For the answer object A these expressions induce the following additional substitution rules this attrCategory catl cat2 this attribute gt labelll labell2 label21 this attribute vl1 v12 v21 3 2 2 Pre defined variables The following variables can be used in the head tail and pattern of an answer format They do not refer to the variable this user outputs the user name of the current transaction typically has the structure name address transactiontime the time when the current transaction was started has format Y Y Y Y MM DD hh mm ss and is based on Coordinated Universal Time UTC formerly known as Greenwhich Mean Time cb_version the version number of ConceptBase cb_date_of_release the version number of ConceptBase currentmodule is expanded to the name of the current module currentpath is expanded to the complete module path starting with root module System that was active when starting the transaction database is expanded to relative or absolute path of the database that was specified with the d option of the CBserver sect
147. ic stratification for the above rule The same argument also works in case of multiple inter dependent rules Static stratification can be tested at compile time of a rule Dynamic stratification is an extension of static stratification i e any statically stratified rule set is also dynamically stratified It is not only considering predicate symbols but also the arguments with which a predicate is called at run time Obviously this depends on the database state at a certain point of time The global rule of dynamic stratification is that the answer to a predicate call A x may not depend on its negation not A x Such a clash can be detected by maintaining a stack of active predicate calls ConceptBase reports a violation of dynamic stratification in the log window of the CB client with a message STRATIFICATION VIOLATION indicating the predicate that participated in the violation Two flavors of error messages can occur e STRATIFICATION_VIOLATIONI The evaluation of a predicate P leads to a cyclic call to itself where in between a negated predicate Q occurs Hence P depends on and Q depends on P Consequently P indirectly depends on its negation e STRATIFICATION VIOLATION While evaluating a predicate P a the system derives that P a would be true i e the fact P a is in the extension of the variable free predicate call P a This evaluation occurs in the context of a matching positive call P x where the system cannot prove that
148. icit premium attribute of an employee of the Netherlands is regarded as an explicit salary as well Note that the three cases discussed here are for explicit attribution objects You may also define rules that derive x m y or x m n y directly In such cases there is no need for an explicit attribute between x and y The attribution is complelety derived 2 2 4 Reserved words In order to avoid ambiguity neither in and isa nor the logical connectives and and or are allowed as attribute labels Likewise names of predicates such as A Ai In should not be used as object names or variable names The same holds for the keywords with and end which are used in the frame syntax 2 2 5 Comparison predicates The next predicates are second class citizens in formulas In contrast to the above predicates they cannot be assigned to classes of the O Telos object base base Consequently they may only be used for testing i e in a legal formula their parameters must be bound by one of the predicates 1 8 1 x lt y x gt y x lt y x gt y x and y may be instances of any class If they are instance of Integer or Real they are or dered numerically If they are instance of TransactionTime they are ordered according to the time they are representing newer times are greater than older times Otherwise they are ordered alphabetically 2 x y The objects x and y are equal 3 x lt gt y or x y The objects x and y are
149. ies A variant of CML was created under the label SML System Modeling Language and implemented by John Gallagher and Levi Solomon at SCS Hamburg CML itself was based on RML Requirements Modeling Language developed at the University of Toronto by Sol Greenspan and others Neither RML nor CML were implemented in 1987 They were regarded as theoretic knowledge representation languages with possible world semantics SML was implemented as a subset of CML using Prolog s SLDNF semantics In 1987 we decided to start an implementation of Telos and quickly realized that the original semantics was too complex for an efficient implementation The temporal component of Telos included both valid time when an information is true in the domain and transaction time when the information is regarded to part of the knowledge base The temporal reasoner for the valid time was based on Allen s interval calculus and was co NP hard We implemented both temporal dimensions in ConceptBase V3 0 only to see that there were undesired effects with the query evaluator and the uniform representation of information into objects Specifically the specialization of a class into a subclass could have a valid time which could be incomparable to the valid time of an instance of the subclass Any change in the network of valid time intervals could change the set of instances of a class Because of that we dropped the valid time as a built in feature of objects but we kept the t
150. ined time intervals Right open time intervals are represented like in the subsequent example P mary mary mary mary tt millisecond 1992 1 11 17 5 42 102 infinity The object mary is believed since 17 05 42 on January 11 1992 The label infinity denotes that the end time of the object lies in the future and is not yet known In any case the current time Now is regarded to be smaller than infinity Right open belief times indicate objects that are part of the current knowledge base Closed intervals denoted by binary tt terms indicate historical objects i e objects that have been untold Example P E1 mary instanceof M tt millisecond 1992 1 11 17 5 42 0 millisecond 1995 12 31 23 59 59 999 The object E1 i e the instantiation of mary to the class Manager is believed from 17 05 42 on January 11 1992 until the end of the last millisecond of the year 1995 We call the first component of the belief time also the start time object and the second component the end time Start and end time of an object can be retrieved by the predicates Known and Terminated see section 2 2 2 2 Rules and constraints The ConceptBase predicative language CBL JK90 is used to express integrity constraints deductive rules and queries The variables inside the formulas have to be quantified and assigned to a type that limits the range of possible instantiations to the set of instances
151. intensive applications JMSV90 JIQV99 JOC 00 requirements engineer ing RaDh92 Eber97 NJJ 96 electronic commerce QSJ02 and version amp configuration management RJG 91 to co authoring of technical documents HJEK90 The key features distinguishing ConceptBase from other extended DBMS and meta modeling systems are Unlimited meta class hierarchy allowing to represent information at any abstraction level data class meta class meta meta class Uniform data structure called P fact for concepts their attributes their class memberships and their super and sub concepts all four types of information are full fledged objects e Clean formal integration of deductive and object oriented abstraction by Datalog logical theories e Complex computations can be user defined by recursive function definitions e g the length of the shortest path between two nodes Queries are defined as classes with user defined membership constraints queries can range over any type of object at any abstraction level Active rules can be used to define the system s reaction to events active rules can change the state of the database and can trigger each other e Client server architecture with wide area Internet access ConceptBase implements the version O Telos Object Telos of the knowledge representation lan guage Telos MBJK90 O Telos integrates a thoroughly axiomatized structurally object oriented kernel with a predicative assertion langua
152. ioms of O Telos Telos and O Telos as well also have strong links to the semantic web in particular to the triple predicates used for defining RDF S statements The main difference is that O Telos is based on quadruples where the additional components identifies the statement While RDF S has to use special link types to reify triple statements i e to make statements about statements O Telos statements are simply referred to by their identifier Telos structurally object oriented framework generalizes earlier data models and knowledge represen tation formalisms such as entity relationship diagrams or semantic networks and integrates them with predicative assertions temporal information and in particular meta modeling This combination of fea tures seems to be particularly useful in software information applications such as requirements modeling and software process control A formal description of O Telos can be found in MBJK90 Jeus92 The following example is used throughout this section to illustrate the language A company has employees some of them being managers Employees have a name and a salary which may change from time to time They are assigned to departments which are headed by managers The boss of an employee can be derived from his department and the manager of that department No employee is allowed to earn more money than his boss This section is organized as follows first the frame and network representation of
153. ion 6 if no database was specified the variable is expanded to lt none gt ConceptBase also adds those command line parameters that deviate from their defaults to the set of pre defined variables The most common ones are see also section 5 9 loadDir directory from which the CBserver loads Telos source files at start up command line param eter load saveDir directory into which the CBserver saves Telos sources of modules at shut down or client logout command line parameter save viewDir directory into which the CBserver materializes results of certain queries command line pa rameter views Moreover if the current transaction was a call of a query like MyQuery v1 paraml then param1 will be evaluated to v1 This makes all parameter substitutions of a query call available to answer formatting 51 3 2 3 Iterations over expressions In case of expressions with multiple values the user may want to generate a complex text that uses one value after the other as a parameter This is in particular useful to transform multiple attribute values like this cat1 The Foreach construct has the format Foreach exprl expr2 x1 x2 expr The expression expr1 is evaluated yielding each a list of solutions s11 s12 The same is applied to expr2 yielding a list s21 s22 Then the variables x1 x2 are matched against the first entries of all lists ie x1 s11 x2 s21 This binding is then applied t
154. ion of multiple objects is possible Validate and update shown objects This operation will check for every object if it is still valid i e if it still exists in the database update the graphical type of the object and the internal cache of the object is deleted see below section 8 2 7 Depending on the option Invalid Telos Objects see above the objects will be either marked or removed from the current view Validate and update selected objects Similar to the previous option but is only applied to objects in the graphical view that have been selected Change graphical palette The current graphical palette assignment of graphical types to nodes and links is replaced by another one 8 2 4 Tool bar The tool bar see figure 8 10 consists of a set of buttons that are mainly short cuts for some menu items The right half of the tool bar provides buttons for the creation of Telos objects Open a new frame without connection Opens a new frame without a connection to a server Within this frame you can create new Telos objects load existing layouts and save new layouts Information about the graphical types is loaded from an XML file included in the JAR file CB_HOME lib classes cb jar Load layout see File Menu gt Load 97 Submit Query Querystring Well_off_Manager v Angus S Lloyd Phil New query Show Objects Cancel Figure 8 9 Query dialog Open
155. is ATTRIBUTE_CAT denotes all attribute labels of the answer object this that are grouped under the category ATTRIBUTE_CAT defined in the query class Example this cat1 evaluates to labe111 label112 The derivation of pattern is performed for each answer object that is in the result set of a query The answer object A induces the following substition rules this A this cat1 gt vl11 v12 this cat2 gt v21 this labell1l vill this label12 v12 this label21 v21 this catl labell label2 this cat2 gt label21 Extended examples for these simple expressions are given in simple answerformats1 sml and simple_answerformats2 sml in the directory CB_HOME examples AnswerFormat Note that only objects that match the query constraint are in the answer Particularly the categories computed attribute and retrieved_attribute require that at least one filler for the respective attribute is present in an answer object Use ConceptBase views View and inherited_attribute in case that zero fillers are also allowed for answers There are few other simple expressions that may be useful They just list attributes without having to refer to specific attributes 50 this attrCategory denotes all attribute categories that are present in an answer object Example For answer object A this attrCategory evaluates to cat1 cat2 this attribute lists all attr
156. is send to the server Thus syntax errors might be already detected at the client side Use Query Result Window If enabled the result of a query is shown in a separate window in a table view Look and Feel You can switch the look and feel to an other style Windows Like Microsoft Windows Motif Like Motif Metal Default Look and Feel Swing Help ConceptBase Manual Opens a window with the online version of this ConceptBase manual About Shows a dialog with information about this program License Displays the license of ConceptBase in a new window History Load History Load previously saved contents of the history window Save History Save contents of the history window to a file Redo History Redos certain operations which are currently in the history The operations can be selected from a list Set History Options Select the type of operations that should be displayed in the history window 4Usually one only asks a single query call like Q v1 p1 However ConceptBase also supports comma separated lists of query calls like 01 v1 p1 02 c1 p2 Such lists of query calls are evaluated one after the other The results is merged into a single answer For technical reasons calls to builtin query classes like get_object Class objname may only occur as a singleton 88 8 1 2 The tool bar The tool bar is the button panel below the menu bar All buttons have tool tips i e small messages that show the meaning of these butt
157. isA gt attribute gt mrule MRule gt constraint MSFOLconstraint Ok TelosEditor View Object as Tree Figure 8 6 Tree Browser To expand an item just double click on the icon If you mark an object name in the tree you can load into the Telos editor with the Telos Editor button or open a new tree browser with the button View Object as Tree 8 2 ConceptBase graph editor The ConceptBase Graph Editor is an advanced graphical modelling tool that supports the browsing and editing of Telos models As the graphical browser of the previous releases it supports different graphical types i e different object types may be represented by different graphical objects In addition to some predefined graphical types the user can add his her own graphical types by modifying and adding certain objects in the knowledge base Furthermore the standard components can be replaced by own classes implementing specific application dependent behaviour In the following we first give an overview of the Graph Editor application and then present the main components and functions of the Graph Editor Details about the use of graphical types can be found in Appendix C An example for the definition of graphical types of the Entity Relationship model is given in Appendix D 2 8 2 1 Overview The ConceptBase Graph Editor is entirely written in Java It can therefore be used on any platform with Java 1 4 The use as appl
158. isted here are used by the ConceptBase user interface CBiva to interaction with the CBserver A normal user typically formulates queries herself In fact most queries listed below are very simple and directly representation as query class An exception are the functions for computation and counting They cannot be expressed by simple query classes but extend the expressiveness of the system E 1 Query classes and generic query classes These queries can also be used in the constraints of other queries E 1 1 Instances and classes ISINSTANCE Checks whether obj is instance of class The result is either TRUE or FALSE IS_EXPLICIT INSTANCE Same as before but returns TRUE only if obj is an explicit instance of class find_classes Lists all objects of which ob jname is an instance find_instances Lists all instances implicit and explicit of class find_explicit_instances Same as before but only explicit instances are returned E 1 2 Specializations and generalizations ISSUBCLASS Checks whether sub is subclass of super The result is either TRUE or FALSE IS_EXPLICIT_SUBCLASS Same as before but returns TRUE only if sub is an explicit subclass of super find_specializations Lists the subclasses of class If ded is TRUE then the result will also include implicit subclasses if ded is FALSE only explicit information will be included find_specializations Same as before but for super classes
159. k tell untell retell any object in any module The value 1 enables access control First untelling of objects must happen in the module where the object has been defined Second any transaction submitted by a user to the CBserver is checked against the permission rules as defined in section 5 By default access control is disabled Enable it when you use ConceptBase in a multi user setting and you want to avoid errorneous interferences between different users e maxerrors sets the maximum number of errors to be displayed to a ConceptBase cc client within one transaction The value 1 means that no restriction is applied Set to 0 to surpress any errors message and to a positive number to limit the displayed errors messages to that number A low positive number can speed up the communication between ConceptBase client and server if a lot of error messages are generated The default is 20 cc ccmode predicate typing controls inhowfar the CBserver applies strict typing of attribution predicates x m y occurring in the membership constraints of query classes If the mode is set to strict 20n Microsoft Windows the server will not abort if the port is already used by another server possibly another CBserver process The new server will take over the port and control it until it is stopped Then the old server which has used the port before has again control over this port 78 default attribution predicates without a unique concerned c
160. la If set to of f Con ceptBase cc will just take a system generated label that contains a unique identifier This is slightly less readable if you want to inspect the generated formulas but safe against certain possibilities of assigning the same label twice The trace of the CBserver can be saved by redirecting its output e g lt CB_HOME gt startCBserver sh r 10 p 4444 t high d MYDB gt gt mylogfile log The CBserver can also be started directly from the ConceptBase cc User Interface see section 8 and most parameters can be specified interactively The command line version is recommended when one CBserver serves multiple users or when user interface and server shall run on different machines Note that some features like persistency can be disabled depending on your licence A corresponding message is displayed in the window where you start the ConceptBase server A frequent error message during the startup of the CBserver is the following FATAL ERROR Application is locked by hostname PID 1234 CBserver aborted This messsage is printed if there is still a file with the name OB lock in the database directory option d The OB lock file should avoid that two servers are using the same database directory The file may be left over of a previous CBserver if the server was not stopped correctly e g aborted by Ctrl C or it crashed If you get this error message make sure that there is no other server running
161. label gt lt attrcatlist gt lt label gt lt proplist gt gt lt property gt 116 lt property gt gt l l l lt complexref gt gt lt enumeration gt gt lt pathexpression gt gt lt pathargument gt gt lt restriction gt gt lt endspec gt gt lt label gt gt lt proplist gt lt property gt lt label gt lt objectname gt lt label gt lt complexref gt lt label gt lt enumeration gt lt label gt lt pathexpression gt lt objectname gt lt withspec gt lt endspec gt lt classlist gt lt objectname gt SELECTORB lt pathargument gt lt label gt lt label gt SELECTORB lt pathargument gt lt restriction gt lt restriction gt SELECTORB lt pathargument gt lt label gt lt enumeration gt lt label gt lt pathexpression gt lt label gt lt objectname gt end ALPHANUM LABEL NUMBER Note ConceptBase represents internally object identifiers as id NUMBER where NUMBER is a se quence of digits For this reason labels matching this pattern are forbidden in the Telos frame syntax A 2 Syntax of the rule and constraint language In the definitions below the term literal is a synonym for predicate lt assertion gt gt l lt rule gt gt lt constraint gt gt lt formula gt gt lt rule gt lt constraint gt forall lt variableBindList gt gt
162. lass Add Attribute Add Individual Delete Object from Database Figure 8 18 The graph after expanding it with the classes and the attributes of the class Employee rules or the Telos axioms For example if we select the object John and select Instance of from the popup menu we can display the implicit classes of John by selecting All from the next submenu As John is an instance of Manager and Manager is a subclass of Employee John is also an instance of Employee As there is no explicit object John gt Employee the instantiation link between John and Employee will be represented as an implicit link i e a dashed line see figure 8 19 The same applies also to attribute links For example the employee Herbert has an implicit boss attribute to Phil This can be shown by selecting Outgoing attributes boss Al Phil from the popup menu Note that the submenu All for the attribute class Attribute will be always empty as only explicit attributes can be displayed in this category 8 3 6 Editing Telos objects Editing Telos objects with the Telos editor Before we are able to edit a Telos object we have to load its frame representation in to the Telos Ed itor field first For loading a Telos object to the Editor field we choose the Telos Editor Button from either the Display Queries oder Display Instances Browsing facilities or the Load Frame
163. lass shall not be accepted If the mode is set to extended the search for concerned classes shall include subclasses see section 2 2 7 If the mode is set to of f ConceptBase cc also accepts queries with unstrictly typed attribution predicates The strict mode is preferable since it avoids certain semantic errors Deduction rules and integrity constraints may never violate the predicate typing condition even if the mode is set to off An example for a query using non strict predicate typing is available from the CB Forum see http merkur informatik rwth aachen de pub bscw cgi 1270138 mu mumode multi user mode specifies whether the CBerver should run in multi user mode value enabled or in single user model value disabled By default the multi user mode is en abled allowing multiple users with different user names to connect to the CBserver In single user mode only clients started by the same user identified by her name can connect to the CBserver The single user mode is recommended if you want to block other users from logging into your CBserver Since the test is done only on the user name a malicious attacker could use your user name for an account on another computer and then successfully log into your CBserver Use Internet firewalls to protect against such attacks y vmode controls whether view maintenance rules are generated vmode on or not vmode of f View maintenance rules are used to keep a ConceptBase cc view up to da
164. lass class In addition PROLOG predicates can be used as predicates You can define your own PROLOG predi cates in a LPI file see section 4 2 2 for an example 2 7 3 Examples This section defines a few datalog queries and rules for the standard example model of Employees Depart ments and Managers see SCB_HOME examples QUERIES The first example defines a more efficient version of the recursive MetabossQuery DatalogQueryClass MetabossDatalogQuery isA Manager with attribute parameter e Employee attribute code ri In e Employee A e boss this r2 vars m In e Employee In m query MetabossDatalogQuery e e A m boss this end Note that the disjunction of the original query is represented by two code attributes The example shows also the use of query expressions and existential variables The second example is the datalog version of the rule for the HighSalary class The infix predicate gt is represented by the predicate GE Class HighSalary2 isA Integer end DatalogInRule HighSalaryRule2 with concernedClass cc HighSalary2 code c In this Integer GE this 60000 end The last example shows the definition of a rule for an attribute It also shows how the performance of a rule can be improved by specifying different variants for different binding patterns The example defines t
165. laying the instances of instances of the class metaMSFOLconstraint The single and necessary constraints are inserted into this class after adding them to the system These constraints themselves can have pecializations constraints which are added automatically to the system when inserting objects into the attribute category single resp necessary For the ER example one of the created formulas reads as forall x EntityType exists y Domain x keyeAttr y 134 bserve the relationship to the necessary formula The formula has been generated by computing one extension of In p Proposition necessary and P p c m d and replacing the predicates In p Proposition necessary and P p c m d by this extension which results in the follow ing substitution for the remaining formula c EntityType Domain m keyeAttr o Metaformulas defining sets of rules Another use of Metaformulas is the formulation of deductive rules Metaformulas defining deductive rules extend the possibilities of defining derived knowledge Assignment of graphical types This example first demonstrates the use of meta formulas to assign graphical types to object categories The minimal graphical convention for ER diagrams is to use rect angular boxes for entities and diamond shaped boxes for relationships In our modelling example these graphical types are assigned to objects which are instances of EntityType or RelationshipType and to in
166. le time For example x m y can only have a non empty extension if some class of x defines an attribute with label m If the argument x in a predicate x m y is a variable then the initial class of x is determined by the the variable range in the formula The variable this of query class constraints can have multiple initial classes being the set of superclasses of the corresponding query class All superclasses of c are also regarded as classes of x If x is a constant then the classes of x are determined by a query to the object base A formula violating the first clause of the predicate typing condition would make a statement about something that is not part of the object base As an example consider the following formula forall x Emplye not x boss Mary With the example object base of section 2 1 we find two errors There are no objects with names Emplye and Mary There are two possible cases to violate the second part of the restriction The first case is illustrated by an example forall x Proposition y Integer x salary y gt y lt 10000 In this case the classes of x Proposition and any of its superclasses have no attribute labelled salary Therefore the predicate x salary y cannot be assigned to an attribute of the object base Instead one has to specify forall x Employee y Integer x salary y gt y lt 10000 or forall x Manager y Integer x salary y gt y lt 10000 depending on w
167. lected This option will remove the currently selected nodes and edges from the view This operation has no effect on the database Selection With this submenu you can either select all objects all nodes or all edges in the current frame Furthermore you can clear your current selection Options menu The options will be stored in a configuration file see section 8 5 when you exit the Graph Editor Language The text for menu items and buttons is available in two languages German and English With this option you can switch between the languages Because of unknown reasons this option does not work under Microsoft Windows Saving of Layouts This option determines whether the definition of the graphical types should be stored also in the layout file when a layout is saved This option is useful for offline usage of the Graph Editor i e without a server as all information necessary to visualize the graph will be included in the file Background Color Here you can change the background color of the graph to your favorite color Component View With this option you can configure the view of an object if the component view is activated by a double click or by the popup menu By default a tree like representation of the object with its classes instances super classes subclasses outgoing and incoming attributes is used If you select Frame then the Telos frame of the object will be shown in a text area see figure 8 8 Inv
168. ler than or equal to the quotient ConceptBase realizes the arithmetic functions via its host Prolog system SWI Prolog Integer num bers on the platforms Solaris Intel Solaris Sparc and Linux are represented as 64 bit numbers yielding a maximum range from 2 1 to 2 1 SWI Prolog supports by default under Windows and Linux64 arbitrarily long integers Real numbers are implemented by SWI Prolog as 64 bit double precision floating point numbers ConceptBase uses 12 decimal digits E 2 2 String manipulation ConcatenateStrings 3 4 concatenates two or more string objects StringToLabel removes the quotes of a string and returns it as a label not an object useful if labels should be passed as a parameter of a query 142 E 3 Builtin query classes These queries must not be used within other queries as they do not return a list of objects They may only be used directly from client programs exists Checks whether ob jname exists and returns yes or no get_object Returns the frame representation of objname This query may be either called with just one parameter ob jname or with four parameters ob jname dedIn dedIsa dedWith The dedx parameters are boolean flags that indicate whether implicit deduced information should also be included in the frame representation Note that the order of the parameters hast to be the same as listed above get_object_star Returns the frame representation for all objects with a label
169. lier ConceptBase releases used the keyword commit instead of noop The semantics was the same We continue to support the use of commit in legacy ECArules 60 4 1 7 Execution Semantics The mode of an ECArule influences its execution semantics There are three basic steps First a Tell Untell Ask transaction is translated in a sequence of atomic events In case of a Tell Untell each frame inside the Tell induces a delimiter in the event list that is used later for the event processing A typical event list might look like e1 2 3 4 5 Here the events e ez were generated for the first frame of a Tell Untell the events ex es were generated for the second frame The event list is right open since the execution of actions from ECArules can lead to further events Each event has one of the forms Tell lit Untell lit or Ask q where lit is an attribution instantiation or specialization predicate and q is a query call ConceptBase will scan the event list and process events as soon as it detects a delimiter For example when ConceptBase sees the delimiter between ez and e4 it will start to process es to ez one after the other Processed events are removed from the event list The first step is to determine the matching ECArules for a given event e This yields a working set of rules for each processed event ej ws e Set of all ECArules whose ON part matches e The matching of the ON part of the ECArule and the ev
170. loaddir is specified The directory loaddir should contain files with file names being formed just like with the save function It load the files in alphabetic order which makes sure that the sources of super modules are loaded before the sources of their sub modules The import is executed once at CBserver startup with the rights of the user who started the CBserver If a file contains an error the loading of this module source fails Error messages shall be displayed in the trace log of the CBserver Note that the CBserver can be started with a non empty database The import of source files will be added to the already existing content of the database Examples CBserver d DB1 save home m DB1SRC This command starts up a CBserver that will eventually save the module sources in the specified direc tory Note that the saving takes place either at CBserver shutdown or when a client tool disconnects partial save CBserver u nonpersistent save home m SRC This variant will start a CBserver with a persistent database but the contents will nevertheless stored as Telos sources files CBserver u nonpersistent load SRC1 save SRC2 This command starts a fresh CBserver i e only system objects are defined and then loads module sources from the directory SRC1 Then client tools may modify the contents of the database Finally the module contents are saved in directory SRC2 CBserver d DB1 load home meee DB1SRC save home m D
171. lowing frame prior to your model QueryClass isA MSFOLrule end Method 2 Decide for each query class individually You tag only those query classes that are used in rules or constraints This individual treatment saves some code generation at the expense of being less uniform Such an individual tagging would look like BaseUnit in QueryClass MSFOLrule isA Unit with constraint cl not exists s Unit sub From s this end ConceptBase will reject an integrity constraint or rule if it refers to a query class that is not an instance of MSFOLrule If a query class is defined as instance of MSFOLrule then it should not have a meta formula as constraint This is a technical restriction that can easily be circumvened by using normal deductive rule For example instead of the query class UnitInstance in QueryClass MSFOLrule isA Proposition with constraint cls this in Unit end you should define 13Tf the CBserver option cc is set to off we also allow calls to generic query classes in rules and constraints In such cases incremental integrity checking will be incomplete and thus potentially wrong Only experienced users should employ them 34 UnitInstance in Class with rule rl forall x VAR x in Unit gt x in UnitInstance end The example uses the macro predicate x in Unit explained earlier in this section It is equiv alent to the sub formula exists c x in c and c in Unit 2 3 3 Nested query calls
172. ls The shape will be drawn in the background of the small component In the default implementation the small component is a transparent JLabel thus the shape is completely visible Note that this might not be the case if you are going to change the implementation of a graphical type see below label The label to be used for this object instead of the object name align Alignment of the label possible values are center left and right default is center size Size of the node in pixels e g 20x20 default done automatically by Java LayoutManager font Name of the font to be used for the shape e g Arial default Default font of Java fontsize Size of the font in pixels default default font size of Java fontstyle The style of the font e g bold italic underlined bold italic Do not forget to include the new graphical type into the graphical palette It is not necessary to define a new graphical palette you can extend the default palette Furthermore you have to define the grapht ype attribute of some object in such a way that it refers to the new graphical type Make sure that the new graphical type has a higher priority than other graphical type which might apply 10 is the highest priority of the default graphical types An example of user defined graphical types can be found in D 2 C 3 2 Providing a new implementation for a graphical type The implementedB
173. luated once when the corresponding popup menu should be shown or when the part of the tree should be shown The result will be stored in a cache for each object This cache is emptied when you invoke the Validate and Update operation from the Current Connection menu 8 3 An example session with ConceptBase In this section we demonstrate the usage of the ConceptBase User Interface by involving an exam ple model It consists of a few classes including Employee Department Manager The class Employee has the attributes name salary dept and boss In order to create an instance of Employee one may specify the attributes salary name and dept The attribute boss will be computed by the system using the bossrule There is also a constraint which must be satisfied by all instances of the class Employee which specifies that no employee may earn more money than its boss The Telos notation for this model is given in Appendix D 1 8 3 1 Starting ConceptBase To start a ConceptBase session we use two terminal windows one for the ConceptBase server and one for the usage environment We start the ConceptBase server by typing the command CBserver p 4200 d test in a terminal window of let us say machine alpha The parameter p sets the port number under which the CBserver communicates to clients and the parameter d specifies the name of the directory into which the CBserver internally stores objects persistently The
174. ly evaluate the IF part but will just append a term def e r to the waiting queue Q When all events in the event list are processed i e when all frames in a Tell Untell transactions are transformed and stored or when the Ask call has been processed then ConceptBase will start to process the waiting queue Q It is processed in a first in first out FIFO manner Each do and def entry is processed according to its type If the entry has the form do r actions then ConceptBase will execute the actions in the second parameter If the entry has the form def e r then ConceptBase will first determine all combinations of vari ables in the IF part of r Then it will call the actions of the DO or ELSE part for the computed answers Note that the event e typically binds some variables in the rule r Actions of an ECArule can update the database They will then lead to new entries in the event list that are processed just like described above The events are generated per action Tell Untell Retell and then followed by a delimiter i e ConceptBase will start processing the events after each Tell Untell Retell action Examples highlighting the differences of the three execution modes are presented in the CB Forum athttp merkur informatik rwth aachen de pub bscw cqi 2924361 You can use the tracemode high see chapter 6 to debug ECArules The ConceptBase server will then write trace messages about the execution of ECArules on the console terminal
175. m provides those solutions to the AL predicate that are directly based on P facts Further solution can be derived via user defined deductive rules The other predicates are based on P facts as well The Ai predicate is for historical reasons not included in the list of axioms It is defined as Vo x n y p c m d P o x n y AP p c m d A In o p gt Ai x m o There are a few variants for the predicates for instantiation specialization and attribution to check whether a fact is actually stored or deduced 18 1 In_s x c The object x is an explicit instance of class c 2 In_e x c or x in c The object x is an explicit instance of class c or of one of the sub classes of c or of the system class of x The system class of individual objects is Individual attribution objects have the system class Attribute instantiation objects the system class Inst anceOf and specialization objects have the system class IsA 3 A e x m y or x m y The objects x and y are linked by an explict attribute with attribute category m The attribute category is either explicitly assigned to the attribute or derived by a rule see subsection 2 2 3 4 Isa_e c d or c isA d The class c is a direct subclass of class d The above predicates can be used for example to define defaults values see http merkur informatik rwth aachen de pub bscw cgi 2396075 Since deduction should be transparent to the user one should avoid using the above predicate
176. mber of clients may be connected to the same server process ConceptBase cc does not yet support concurrency control beyond a forced serialization of messages 1 3 Hardware and software requirements ConceptBase cc operates on e SUN SPARC CPUs under Solaris 8 or higher e 1386 CPUs under Solaris 8 or higher e 1386 CPUs under Linux Kernel 2 4 or higher 164 AMD64 CPUs under Linux Kernel 2 4 or higher e 1386 CPUs under Microsoft Windows 2000 XP Vista 7 The platform Mac OS X on PowerPC CPUs is no longer supported by ConceptBase cc The last available built for this platform is ConceptBase 7 1 compiled January 18 2008 This built is available from the ConceptBase Forum 1 All trademarks are property of their respective owners Implementation languages are Prolog in particular for logic based transformation and compilation tasks and C C in particular for persistent object storage and retrieval The ConceptBase cc usage en vironment CBiva executes on any platform with a compatible Java Virtual Machine Java 1 4 Java 5 Java 6 Update 11 or earlier OpenJDK Java 6 Runtime We suggest to use the Java 5 Runtime Environ ment which is available at Sun s Java Archive http java sun com products archive If you downloaded the Windows variant of ConceptBase cc you do not need to install a compatible Java Runtime Environment since it is already included in the binaries The ConceptBase cc server CBserver is dynamically link
177. mely instances of javax swing JComponent Thus different components can be provided to represent an object e g tables buttons text fields You can implement your own component and integrate into the Graph Editor by extending a specific Java class Details about the customization of the Graph Editor using graphical types and other components can be found in appendix C Finally the Graph Editor removes some drawbacks from the previous graph browser On the one hand it can be used to edit Telos models see section 8 2 6 On the other hand it is able to show also implicit relationships between objects which have been derived by rules or Telos axioms For each type of relation 94 ship instanstation specializations and attributes one can choose to see only the explicit relationships or to see all relationships 8 2 2 Starting the graph editor The Graph Editor is usually invoked by CBiva the CB workbench by using the menu item Browse gt Graph Editor If CBiva is connected with a CB server the Graph Editor will be connected to this server and you will be prompted to enter the object name you want to start with and a name of a graphical palette The graphical palette is a Telos object which represents a set of graphical types which will be used to visualize Telos objects see Appendix C On startup the Graph Editor retrieves all information about the graphical types from the server Depending on your system this might take about 1
178. ment one can attach a priority value to each graphical type If there multiple graphtype attributes defined for one object the graphical type with the highest priority value will be used Many applications employ multiple notations to provide different perspectives on the same set of ob jects Each perspective emphasizes on a specific aspect of the world such as the data oriented the process oriented and the behavior oriented viewpoint and uses an aspect specific notation A graphical notation as e g the Entity Relationship diagram typically consists of a set of different graphical symbols as e g diamonds rectangles and lines A graphical palette is used to combine the set of graphical types that together form a notation Individual GraphicalPalette in Class with attribute contains GraphicalType default GraphicalType end 125 In such a setting the same object may participate in different perspectives ConceptBase offers the possibility to specify multiple graphical types for the same object A tool can then provide different graph ical views on the same object To get the desired graphical type of an object under a specific palette an application program specifies the name of the actual graphical palette as answer format when querying the ConceptBase server Although this mechanism is available for arbitrary application programs we restrict our description to the ConceptBase Graph Editor The default specification serves as a ca
179. ment is optional We recommend to use short names to simplify the constructions of functional expressions The above Telos frame must be permanently stored in any ConceptBase database that is supposed to use the new function The second aspect of a function is its implementation The implementation can be in principal in any programming language but we only support PROLOG because it can be incrementally addded to a Con ceptBase database An implementation in another programming language would require a re compilation of the ConceptBase server source code The syntax of the PROLOG code must be conformant to the Prolog compiler with which ConceptBase was compiled This is in all cases SWI Prolog www swi prolog org For our sin example the PROLOG code would look like compute_sin _res _x _C cbserver arg2val _x _v number _v _vres is sin _v cbserver val2arg _vres _res tell sin in Function isA Real with parameter x Real end The first argument _res is reserved for the result then for each parameter of the function there are two arguments The first is for the input parameter _x the second holds the identifier of the class of the parameter here _C It has to be included for technical reasons The clause tell instructs ConceptBase to tell the Telos definition when the LPI file is loaded Instead of this clause you may also tell the frame manually via the ConceptBase user interface There are a few ConceptBase pr
180. modeling example ER diagrams D 2 1 The basic model This example gives a first introduction into some features introduced in ConceptBase version 4 0 It demonstrates the use of meta formulas and graphical types while building a Telos model describing Entity Relationship Diagrams The following model forms the basis KKK KKK KKK KKK KKK KK KK KKK KK x x File ERModelClasses x x x ERR REE RERA ERR EER EAE ER ERS Class Domain end Class EntityType with attribute eAttr Domain keyeAttr Domain end Class RelationshipType with attribute role EntityType end 131 Class MinMax end 1 in MinMax with end 1 1 in MinMax with end Attribute RelationshipType role with attribute minmax MinMax end The model defines the concepts of EntityTypes and RelationshipTypes Each entity that participates in a relationship plays a particular role This role is modelled as a Telos attribute link of the object Rela tionshipType The attributes describing the entities are modelled as Telos attribute links to a class Domain containing the value sets Roles can be restricted by the min max constraints 1 or 1 1 The next model contains a concrete ER model HEX ERE ERR RAKE RRA EE AA A Le x File Emp_ERModel x gt J HERAEAEEEEREDERAKH ARA Class Employee in EntityType with keyeAttr attribute ssn Integer eAttr attribute name String end
181. mpDept The second expression of the answer format EmpDeptFormat uses the builtin external procedure UQ It removes the quotes from a string Analo gously a procedure OT can be used to put quotes around a term 3 3 Parameterized answer formats The general way to use an answer format for a query is to define the attribute forQuery Another possibility is to specify the answer format for a query is to use the answer representation field of the ASK method in the IPC interface The following code is an example for specifying a user defined answer in the ASK method This example is written in Java and uses the standard Java API of ConceptBase see the Programmer s Manual for details import i5 cb api x public class CBAnswerFormat public static void main String argv throws Exception CBclient cbh new CBclient localhost 4001 null null CBanswer ans cb ask find_specializations Class class TRUE ded OBJNAMES AFParameter bla somevar Now System out println ans getResult cb cancelMe In the example a connection is made to a ConceptBase server on localhost listening on port 4001 The ask method of the CBclient class sends a query to the server The first argument is the query the second argument is the format of the query in this example it is just one object name the third argument is the answer representation and the last argument is the rollback time The third argument is th
182. n we start the usage environment with the command CBjavalnterface in the other window It is also possible to start the ConceptBase server from the user interface To do so choose Start CBserver from the File Menu of CBiva see section 8 1 1 and specify the parameters in the dialog which will be shown see figure 8 13 The option Source Mode controls whether the CBserver accessing the database via the d parameter database maintained in binary files or via the db parameter database maintained both in binary files and in source files See section 6 for more details Once the information has been entered via the OK button the server process will be started and its output will be captured in a window This output window provides also a button stop the server If you started the server this way then you can skip the next section as the user interface will be connected to the server automatically 8 3 2 Connecting CBiva to the ConceptBase server Next we establish a connection between the ConceptBase server and the usage environment This is done by choosing the option Connect from the File menu of the ConceptBase Workbench An interaction window appears see Figure 8 14 querying for the host name and the port number of the server i e the number we have specified within the command CBserver p 4200 d test 8A full list of all parameters is described in section 6 Note that the script CBserver must be in the search path It is av
183. n Proposition with transitive ancestor Person end ConceptBase will match the attribute Person ancestor with the variable AC in the above meta formula This yields P Person ancestor Person ancestor Person which binds the meta variable C to Person and Mto ancestor The resulting generated formula is forall x y z VAR x in Person and y in Person and z in Person and x ancestor y and y ancestor zZ gt x ancestor zZ which can be shortened to forall x y z Person x ancestor y and y ancestor z gt x ancestor zZ 26 This formula is fulfilling the predicate typing condition Likewise the connection relation of cities gets transitive via City in Proposition with transitive connection City end The advantage of meta formulas is that they save coding effort by re using them in different modelling contexts If a meta formula is linked to an attribute category like transit ive in the example above then the semantic of several such attribute category can be combined by just specifying that a certain attribute has multiple categories Assume for example that we have defined acyclicy with a similar meta formula Proposition in Class with attribute acyclic Proposition constraint acyclic_IC forall x y M VAR AC Proposition acyclic C Proposition P AC C M C and x in C and y in C and x M y gt not y Mx end Then the ancestor attribute can be specified to be both transitive and acyclic by
184. nce with a Repository System for Information Systems Development In R Kasckek ed Proceed ings Entwicklungsmethoden fr Informationssysteme und deren Anwendung EMISA 99 Reihe Wirtschaftsinformatik Teubner Verlag Stuttgart Germany pp 147 174 1999 Jarke M Mylopoulos J Schmidt J W Vassiliou Y Information systems development as knowledge engineering a review of the DAIDA project Programirovanie Vol 17 No 1 Academy of Sciences Russia also appeared as technical report MIP 9010 Universitat Passau Germany 1990 Jarke M Quix C Calvanese D Lenzerini M Franconi E Ligoudistianos S Vassil iadis P Vassiliou Y Concept Based Design of Data Warehouses The DWQ Demonstra tors ACM SIGMOD International Conference on Management of Data SIGMOD 2000 Dallas TX May 2000 http www i5 informatik rwth aachen de lehrstuhl projects dwq dwqdemo Jeusfeld M A Quix C Jarke M Design and Analysis of Quality Information for Data Warehouses 17th International Conference on the Entity Relationship Approach ER 98 Sin gapore 1998 MasterProLog 4 1 Reference Manual IT Masters 1999 Mylopoulos J Borgida A Jarke M Koubarakis M Telos a language for representing knowledge about information systems ACM Trans Information Systems Vol 8 No 4 1990 Nissen H W Jeusfeld M A Jarke M Zemanek G V Huber H Managing Multiple Re quirements Perspectives with Metamodels IEEE Sof
185. nd tail arguments are strings that define the substring substitution when the answer is formatted They contain substrings of type expr that are replaced The head and tail strings are evaluated once independent form the answer to the query Usually they do not contain expressions but only text The response to a query is a set of answer objects A1 A2 The pattern string is evaluated against each answer object For each answer object the derivation of the pattern is put into the answer text Hence the complete answer consists of derivation of head string derivation of pattern string for answer object Al derivation of pattern string for answer object A2 derivation of tail string The fileType attribute is explained in section 3 4 In the next sections we will explain more details about answer formats using the following example An answer object A to a query class QC has by default a frame structure A in QC with catl label11 v11 label12 v12 cat2 label21 v21 Pesa end In case of a complex view definition VC the values vij can be answer objects themselves e g B in VC with cati label11 v11 label12 v12 cat2 label21 v21 with 49 cat21 label211 v211 ls a end AE end 3 2 Constructs in answer formats 3 2 1 Simple expressions in patterns We first concentrate on the pattern attribute i e they are not applicable in the head or tail attribute of an answer
186. nds of the file will be executed without user interaction and CBShell will exit at the end t This option can only be used in combination with the f option It shall instruct CBshell to confirm each comman in the script file before it is executed i This options starts is for invoking a CBserver compiled directly from its sources For developers only 7 3 Commands startServer serveroptions starts a CBserver with the specified options and connects to it enrollMe host port connects to an already running CBserver i e not using the startServer command cancelMe disconnects from a CBserver stopServer stops the CBserver which is currently connected tell frames tells frames to the CBserver untell frames untells frames from the CBserver 84 retell untellFrames tellFrames untells and tells frames to a CBserver in one transaction tellModel file file2 tells files to the CBserver the files can have file types sml and txt if no file type is specified ConceptBase cc will append the default file type sml to the file name Pi n ask Query QueryFormat AnswerRep RollbackTime asks a query possible query formats are OB JNAMI and FRAMES the answer representation can be LABEL FRAME default or a user defined answer format the rollback tome should be Now If the query format is OBJNAMES then Query is a string containing a query call or a comma separated list if query calls It the query format is FRAMES th
187. ng Springer Verlag 1984 Chen P P C The Entity Relationship Model Towards a Unified View of Data ACM Trans act on Database Systems Vol 1 No 1 March 1976 pp 9 36 1976 Chen W Warren D S Tabled Evaluation with Delaying for General Logic Programs Vol 43 No 1 January 1996 pp 20 74 1996 Eberlein A Requirements Acquisition and Specification for Telecommunication Services PhD Thesis University of Wales Swansea UK 1997 Gallersd rfer R Realization of a Deductive Object Base by Abstract Data Types in German Diploma thesis Universit t Passau Germany 1990 Hahn U Jarke M Eherer S Kreplin K COAUTHOR a hypermedia group authoring en vironment In Benford J M Bowers S D eds Studies in Computer Supported Cooperative Work North Holland 79 100 1990 Jarke M ed Database Application Engineering with DAIDA Springer Verlag 1993 Jeusfeld M A Jarke M From Relational to Object Oriented Integrity Simplification Proc 2nd Intl Conf Deductive and Object Oriented Databases Munich Dec 1991 also as Aach ener Informatik Berichte 91 19 RWTH Aachen Germany 1991 Jeusfeld M Staudt M Query optimization in deductive object bases To appear in Frey tag Vossen Maier eds Query Processing for Advanced Database Applications Morgan Kaufmann 1992 also as Aachener Informatik Berichte 91 26 RWTH Aachen Germany Jeusfeld M A Anderungskontrolle in deduktiven
188. nipulated by ConceptBase are persistently stored in a collection of external files which reside in a directory called application or database The actual directory name of the database is supplied as the d parameter of the command CBserver The u parameter of the CBserver specifies whether updates are made persistent or are just kept in system memory temporarily Use u persistent for a update persistence or u nonpersistent for a non persistent update mode The database can be modified interactively using the editor commands TELL UNTELL Another way of extending ConceptBase databases is to load Telos objects expressed in frame syntax stored in plain text files with the extension sml Call the menu item Load Model from the File Menu to add these objects to the database In our example the database directory Employee was built interactively and can be found together with files containing the frames constituting the example in the directory CB_HOME examples QUERIES where you have to replace CB_HOME with the ConceptBase installation directory The following files contain the objects of the Employee example expressed in frame syntax Employee_Classes sml Employee_Instances sml Employee Queries sml An alternative to interactively building a database is to start the server with an empty database d newfile and then add the objects in these files by using Load Model Note that the sml extension may be omitted During the lo
189. ns 15000 dept advises PR currentdept RD end The object mary has four attributes with object labels hername earns advises and current dept The attribute categories are name aliasname salary and dept The last category is instan tiated twice ConceptBase uses the following predicates to express the content of the frame mary in Manager mary name hername Mary Smith mary aliasname hername Mary Smith mary salary earns 15000 mary dept advises PR mary dept currentdept RD 19 So there are four attributes using four attribute categories Like an object can have multiple classes an attribute can have multiple categories In fact explicit attributes in O Telos are just objects and their attribute categories are their classes At the lowest abstraction level tokens the object labels of the at tributions frequently do not carry a specific meaning and can then be neglected when formulating logical expressions The attribution predicate x m y performs just this projection In the example the follow ing attributions would be true mary name Mary Smith mary aliasname Mary Smith mary salary 15000 mary dept PR mary dept RD The class labels name aliasname etc are defined at an abstraction level where the meaning of some application domain is captured The class label attribute category of an attribute is defined as an object label of an attribute at the class level For example the name and aliasname
190. nt The relation marriedTo of Person must be symmetric i e x marriedTo y implies y marriedTo x will be presented to the user An example violation is bill in Person with marriedTo ml eve end ve in Person end One can also define a hint for the meta level constraint that refers only to a non empty subset of the meta variables If a hint for a meta formula cannot be substituted as shown avove ConceptBase will not issue the hint but rather the text of the generated formula Examples of user defined error messages can be found in the ConceptBase Forum at http merkur informatik rwth aachen de pub bscw cgi 1543277 2 3 Query classes ConceptBase realizes queries as so called query classes whose instances fulfill the membership constraint of the query Stau90 This section first defines the structural properties of the query language CBQL and then introduces the predicative component Queries are instances of a system class QueryClass which is defined as follows 12Meta variables are those variables that occur in the class position of x in c or in the label position of x m y or Label x m In the running example C and M are meta variables 29 QueryClass in Class isA Class with attribute retrieved_attribute Proposition computed_attribute Proposition attribute single constraint MSFOLquery end A super classes of query class imposes a range condition of the set of possible instances of the query class
191. nt above A hint could look like Employee SalaryBound with comment hint An employee may not earn more than her his manager end It is also possible to attach hints to meta level constraints In this case the hint text can refer to the meta level variables occuring in the meta level constraint These variables will be replaced by the correct fillers when the meta level constraint is utilized in some modeling context Assume for example we want to have a symmetry category and attach a readable hint to it 28 Proposition with attribute symmetric Proposition end RelationSemantics in Class with constraint symm_IC forall AC Proposition symmetric C Proposition x y VAR M VAR P AC C M C and x in C and y in C and x My gt y Mx end RelationSemantics symm_IC with comment hint The relation M of C must be symmetric i e x M y implies y M x end Note that the references to the meta variables M and C are surrounded by curly braces and that these meta variables are also occurring in the meta level constraint Now use the symmet ric concept in some modeling context e g to define that the marriedTo attribute of Person should be symmetric Person with attribute symmetric marriedTo Person end At this point of time ConceptBase will find the hint text for the symmetric constraint and will adapt it to the context of C Person and M marriedTo When an integrity violation occurs the substituted hi
192. nt is not transparent The default implementation in CBIndividual and CBLink provide a transparent JLabel as small component so that the shape is visible The Graph Editor contains several predefined shapes see below boolean doCommit This method is called when the user has clicked on the Commit button Changes that have been made within this component e g within a form can then be added to the list of objects to be removed added from the database If the method returns false then the commit operation will be aborted Furthermore the CBUserObject class provides several methods which might be useful for implement ing new graphical types String toString returns the full object name of the Telos object which is represented by this user object TelosObject getTelosObject returns the Telos object which is represented by this user object see docu mentation of package 15 cb telos object for more details on TelosObject CBFrame getCBFrame returns the frame in which this object is presented a CBFrame is an extension of a JInternalFrame ObjectBaseInterface getObi returns the ObjectBaselnterface i e a connection to the server of the cur rent frame This is useful if you want to execute your own queries to retrieve additional information from the server see documentation of package i5 cb telos object and i5 cb api for more details String getProperty String property returns the value of a property boolean hasProperty String
193. nteract via inter process communication IPC channels Fig 1 1 Although this communication channel was initially meant for use in local area networks it has been used successfully for nationwide and even transatlantic collaboration of clients on a common server The ConceptBase cc server CBserver offers programming interfaces that allow to build clients and to exchange messages in particular for updating and querying object bases using the Telos syntax We provide support for C Java TCL and Prolog Detailed descriptions of the interfaces and the corresponding libraries that are delivered with ConceptBase cc can be found in the ConceptBase Programmers Manual Graph Telos Mail Browser 2 Editor 5 Tool 8 GBROWSE EDIT SEND RECEIVE Communication channel intemet TELL ASK l ee i SQL SQL CB rel rel SS E Server 23 DBMS 1 DBMS 2 Er E 55 Y Representation of ervirorment within CB s object base Figure 1 1 The client server architecture of ConceptBase cc ConceptBase cc comes with a standard graphical usage environment CBjavalnterface implemented in Java which supports editing ad hoc querying and browsing of O Telos object bases The user interfaces of ConceptBase can serve for the user as an example client for programming own application specific client tools Although ConceptBase cc provides multi user support and an arbitrary nu
194. o circumvene the problem we write an intermediary rule replacing the predicate x in SUBC forall x Proposition spec ISA SUBC CLASS spec sub SUBC and x in SUBC gt x inSubRel SUBC 27 and then re write the original constraint to forall x VAR SC CLASS spec ISA_complete spec super SC and x in SC gt exists SUBC CLASS spec sub SUBC and x inSubRel SUBC So essentially we pass the meta variable to the condition of the intermediary rule The attribute inSubkRel is just used to be able to specify a dedicated conclusion predicate for the intermediary de ductive rule It is defined as attribute of Proposition The complete example is at http merkur informatik rwth aachen de pub bscw cgi d3070600 mp ISA complete sml txt Many more re usable examples for meta formulas are in the ConceptBase Forum at http merkur informatik rwth aachen de pub bscw cgi 1042523 2 2 10 Further object references In addition to the so called select expressions gt gt already introduced above for directly refering to attributes specializations and instantiations as objects three other basic constructors may be used within frames and assertions e is the counterpart of and denotes the target of an attribute instead of the attribute object itself e g mary advises is the same as PR e The set valued operator has the commonly used meaning as in paths in object oriented models and relates an object with the set of all
195. o the expression expr which should contain occurences of x1 x2 This replacement is continued with the second entries in all lists yielding bindings x1 s12 x2 s22 This is continued until all elements of all lists are iterated If some lists are smaller than others the missing entries are replaced by NULL During each iteration the new bindings induce substitution rules for the binding Iteration 1 x1 gt sill x2 3521 Iteration 2 x1 gt s12 1x2 522 Note that the third argument expr may contain other subexpressions even a nested Foreach An example for iterations is given in CB_HOME examples AnswerFormat iterations sml The Foreach construct contains three arguments separated by commas These two commas are used by ConceptBase to parse the arguments of the Foreach construct and similar answer formatting expressions They are not printed to the answer stream 3 2 4 Special characters If one wants a comma inside an expresssion that shall be visible in the answer then one has to escape it The same holds for the other special characters like etc Here is a short list of supported special characters Some require a double backslash Yin new line ASCII character 10 t tab character Mb backspace character 0 empty string no character left parenthesis right parenthesis Ne comma In principal any non alphanumerical character like C
196. ocedures in the body of the compute_sin that are of importance here The procedure coserver arg2val converts the input parameter to a Prolog value ConceptBase internally always uses object identifiers They have to be converted to the Prolog representation in order to enter them into some computation The reverse procedure is coserver val2arg It converts a Prolog value e g a number into an object identifier that represents the value If necessary a new object is created for holding the new value The above code should be stored in a file like sin swi lpi This file has to be copied into the ConceptBase database which holds the Telos definition of sin You will have to restart the ConceptBase server after you have copied the LPI file into the directory of the ConceptBase database If you want the new function to be available for all databases you construct then you have to copy the file sin swi 1lpi to the subdirectory 1ib system of your ConceptBase installation Note that your code might be incompatible with future ConceptBase releases If you think that your code is of general interest you can share it with other ConceptBase users in the Software section of the CB Forum http merkur informatik rwth aachen de pub bscw cgi 2768063 2 5 5 Recursive function definitions Some functions like the Fibonacci numbers are defined recursively ConceptBase supports such recursive definitions If the function is defined in terms of itself then you just
197. of deductive rules additional problems arise similar to the straticfication problem At the moment only monotonous transactions are allowed This means that generated formulas can only be inserted or deleted during one transaction both operations at the same time are not permitted The meta formula mechanism also influences the efficiency of the system every transaction has to be supervised wether it affects the meta formulas or one of the generated formulas If the preconditions of the generated formulas don t hold anymore e g if the instances of EntityType eAtt r are no longer instances of Proposition necessary in the previous model the corresponding generated formula has to be deleted If additional attributes are instantiated to Proposition necessary additional formulas have to be created The process of supervising the transactions is quite expensive and if it slows down the overall performance too much some of the meta formuals can be disabled temporarily Untelling a meta formula removes all the code generated Many more examples for meta formulas e g for defining transitivity of attributes are available from the CB Forum http merkur informatik rwth aachen de pub bscw cgi 1042523 139 Appendix E Predefined Query Classes This chapter gives an overview of the query classes which are predefined in a standard ConceptBase in stallation The names of parameters of the queries are set in typewriter font Most of the queries l
198. of the Graph Editor several caches are used On the other hand the use of a cache causes several problems which will be addressed in this section In particular the caches of the Graph Editor are not updated automatically if the corresponding data in the server is updated Graphical Palette and Graphical Types When a connection to a server is established the Graph Editor loads the graphical palette and all its graphical types including their properties and other information If an object has to be shown the server sends only the name of the graphical type the information about the properties are taken from the cache Thus if you change the graphical palette or a graphical type after the Graph Editor has established the connection this change will not be visible in the Graph Editor There is currently no method implemented to update the cache manually 7You can unselect an object by holding down the Control key and clicking on the object 101 Graphical Types of Objects When an object is loaded from the server also the graphical type for this object is retrieved The graphical type of the object is updated when you invoke the Validate and Update operation from the Current Connection menu Lists of super sub classes classes instances attributes The lists in the popup menu or in the tree like view of an object are produced by evaluating queries To reduce the communication between client and server each query will only be eva
199. on 12 classes can have deductive rules and integrity constraints Integer and real numbers are written in the usual way strings are character sequences e g this is a string These three classes are supported by comparison predicates like x lt y discussed in section 2 2 and by functions like PLUS MINUS discussed in section 2 5 As legacy support ConceptBase provides the pre defined classes Token SimpleClass Meta Class and MetametaClass to structure the object base into objects that have no instances tokens objects that have only tokens as instances simple classes objects that have only simple classes as instances meta classes and finally objects that have only meta classes as instances meta meta classes These classes are provided only for compatibility with older Telos specifications In fact an absolute hierarchy from tokens to simple classes to meta classes etc is not an essential ingredient of O Telos and in many situations too restrictive Instead meta class levels are implicitely expressed via instantiation If an object x is an instance of object c and object c is an instance of object mc then mc is also called a meta class of x and c a class of x Being a class or a meta class is relative to the object x that we consider For example mc is the class of c This implicit definition of the meta class concept is far more flexible than a fixed structure 1 There is virtually no limit in the meta class hierarchy th
200. onceptBase cc now relies on SWI Prolog ht tp www swi prolog org Formerly ProLog by BIM had been used implementation concepts can be found in the references Chapter 2 describes the ConceptBase cc version of the Telos language and gives some examples for its usage Chapter 6 discusses the parameters that can be set when starting the CBserver Finally section 8 describes the ConceptBase cc Usage Enviroment Appendices contain a formal definition of the Telos syntax and internal data structures A Appendix C summarizes the mechanism for assigning graphical types to objects and adapting the graphical browsing tool for specific application needs Appendix D contains the full Telos notation of an example model D 1 and a case study on the modeling of entity relationship diagrams with Telos D 2 Plenty of further examples for particular application domains and add ons for meta modeling can be retrieved from the ConceptBase Forum 1 5 Differences to earlier versions ConceptBase cc 7 3 should be largely compatible to its direct predecessor We mainly improved the stabil ity and removed some restrictions of the metaformula compiler The release notes to ConceptBase cc 7 3 lists all major changes and issues You find the release notes in the subdirectory doc TechInfo of your ConceptBase cc installation directory or via the web site http conceptbase cc The system still has about the same memory footprint as it used to be 10 years ago You can
201. ons The tool tips appear if you move your mouse pointer over the button and do not move your mouse for about one second The buttons are shortcuts for some operations that are frequently used and are also available in the menu The operations apply to the Telos Editor which has currently the focus e Connect to previously connected server or disconnect e Clear e Cut Copy Paste e Tell Untell The objects specified in the active Telos Editor will be added or removed from the object base e Retell A new window will popup and ask you to enter the frames that should be untold and told The contents of the current Telos Editor will be inserted as default into the two text areas e Ask Evaluate the query specified in the Telos Editor gt If you specify the name of an ordinary class i e not a query class then ConceptBase will interpret this as a query call to find all instances of that class You can also enter an arithmetic expression like 100 COUNT QueryClass COUNT Class e Load Object Load the Telos frame of an object e Exit You can move the tool bar outside the main window or display it in vertical form if you click inside the tool bar and drag it to another place 8 1 3 The status bar The status bar contains some fields that display general information about the status of the application e Connection status either connected or disconnected from server e Short message usually the result of the last action e Current
202. ontent The contains attribute allows to check which objects belong to a module It can be used by a simple query that lists the module content of all modules that are currently visible ShowModule in QueryClass isA Module with computed_attribute cont Proposition constraint ccont this contains cont end A more sophisticated method is to use the builtin query listModule A call of 1istModule without parameters will list the current module as Telos frames You can also provide the module to be listed as a parameter e g listModule System module will list the content of the module System ConceptBase will check read permission before a module content is listed You can also use a module path as parameter e g listModule System oHome Work module A module path is formed much like a directory path in a file system The root module is System and modules names are separated by the character The implementation of the 1istModule query preserves the order in whoch objects have been created Note that the System module is defining the essential objects that ConceptBase requires to run correctly You can list the System module but you should not change it 74 5 8 Saving and loading module sources The ConceptBase server see section 6 has two command line options save and load to synchronize with the content of database modules as Telos sources files in the file system of the CBserver The purpose of this fea
203. ool to express semantics of concepts that are not expressible by deductive rules For example the semantics of petri nets in particular the firing of an enabled transition can be expressed by a single ECArule ECArule UpdateConnectedPlaces with mode m Deferred rejectMsg rm The last firing of a transition failed Check whether the transition was enabled ecarule er fire FireTransition tr Transition pl Place n nl Integer ON Tell fire transition tr IF tr in EnabledTransition and pl in ConnectedPlace tr and pl tokenFill n and nl nt NetEffectOfTransition pl tr DO Untell pl tokenFill n Tell pl tokenFill n1 ELSE reject end The example shows that the condition can also be a complex logical expression Note that the event ON part binds the two variables fire and tr The condition IF part additionally binds the free vari ables p1 n and n1 Each binding of the free variables is passed to the DO part leading to some update of the tokenFil1 attribute In case that the IF part cannot be evaluated to true the ELSE part is executed That will lead to an abortion of the current transaction rolling back all updates and issuing the error message listed under rejectMsg The complete example of modeling petri nets is in the CB Forum http merkur informatik rwth aachen de pub bscw cgi 1419080 Further examples of ECA rules can be found at http merkur informatik rwth aachen de pub bscw cgi
204. op This action stands for no operation i e nothing is done It can be useful for certain constructions with empty DO parts reject The current transaction is aborted and rolled back All variables in Tell Untell and Retell actions must be bound The insertion of an attribute A x ml y is only done if there is no attribute of category m1 with value y for object x Then a new attribute with a system generated label is created If an attribute A x m1 y should be deleted then all attributes of cat egory m1 with value y for object x are deleted It is well possible that an attribute is updated untell tell several times by action parts of ECArules during a single ConceptBase transaction Only the state of the attribute after all ECArule firings will be visible after a successful commit There are a few special procedures which may be called within the DO or ELSE part of an ECArule CreateIndividual Prefix ID A new individual object with the given prefix and a system generated suffix is created The object identifier of the created object is returned in the second argument which must be therefore a free variable The prefix must be an existing object name e g the class name otherwise the ECArule compiler will report an error newLabel Prefix L A new label that is not yet used as object name is created The prefix must be an existing object name The 2nd argument should be a variable The type of the variable can be Label
205. or integrity constraints e Deductive rules ranging over more than one classification level instances classes meta classes etc are partially evaluated to a collection of rules or constraints ranging over exactly one classification level O Telos should be regarded as the data modeling language of a meta database Itis capable to represent semantic features of other data modeling languages like entity relationship diagrams and data flow dia grams Once modeled as meta classes in O Telos one simply has to tell the meta classes to ConceptBase to get an evironment where one can manipulate models in these modeling languages Since all abstrac tion levels are supported the models themselves can be represented in O Telos and thus be managed by ConceptBase ConceptBase s implementation of O Telos provides a couple of features beyond the core O Telos First of all there is a dedicated query language CBL which provides a class based interpretation for queries Secondly modules have been introduced to structure the search space Essentially the module identifier is added to the object identifier Thirdly ConceptBase supports a limited version of active rules to react to internal and external events Finally ConceptBase supports recursively defined functions and arithmetic expressions 1 2 The architecture of ConceptBase cc ConceptBase cc 7 3 follows a client server architecture Clients and servers run as independent processes which i
206. ork relatively to a specified module The normal way of specifying the context in which a transaction takes place is using the Set Module function from the CBworkbench See subsection 5 2 to learn how to change the module context of a transaction The basic set of predefined objects of ConceptBase such as Class Proposition QueryClass etc belongs to the predefined module System The default module of clients logging into a CBserver is oHome a direct submodule of System You can set the module context to your other modules in order to manipulate them 67 The contains attribute of the Module object is a derived attribute and is a link to all objects defined inside the context of a certain module This attribute is not stored explicitly but can be used anywhere in the O Telos assertion language Now we show how to create modules We introduce a small running example in order to demonstrate all module related facilities of ConceptBase Let s assume you ve started ConceptBase with a fresh database file After telling the following two frames the server contains two new modules which are nested inside the pre defined oHome module Module Master end Module Work end 5 2 Switching between module contexts The standard way for changing the module context is to choose the select module menu entry from the Options menu in the user interface A dialog with a listbox containing all known modules in the current context are shown Double clicking a mo
207. outs of the graph editor are stored with all information about graphical types true false InvalidObjectsMethod Specifies whether objects that have been identified as invalid should be marked or deleted mark delete DiagramDesktopBackgroundColor Background color of the desktop of the graph editor comma separated representation of an RGB value DebugLevel Level for debug messages Possible values are SEVERE WARNING INFO CON FIG FINE FINER FINEST according to the java util logging package Default is WARN ING 112 Bibliography NOTE BBD 90 BBMR89 BCG 87 BMS84 Chen76 CW96 Eber97 Gall90 HJEK90 Jark93 JeJa91 JeSt92 Jeus92 A complete list of papers related to ConceptBase can be found at http www 15 informatik rwth aachen de CBdoc cblit html Bellosta M J Bessede A Darrieumerlou C Gruber O Pucheral P Thevenin J M Stef fen H GEODE Concepts and Facilities Manual INRIA Roquencourt France 1990 Borgida A Brachman R J McGuiness D L Resnick L A CLASSIC a structural data model for objects Proc ACM SIGMOD Intl Conf Management of Data Portland Or 58 67 1989 Banerjee J Chou H T Garza J F Kim W Woelk D Ballou N Kim H J Data model issues for object oriened applications ACM Trans Office Information Systems 5 1 3 26 1987 Brodie M L Mylopoulos J Schmidt J W ed On Conceptual Modeli
208. ow Attribute Classes The Frame Browser can be used with and without a connection to a ConceptBase server If it is not connected it retrieves the information out of a local cache which can be loaded from a file by using the Load button The file has to be plain text file with Telos frames All objects in the cache can be saved into a text file as Telos frames with the Save button The contents of the cache can be viewed with the Cache button The result of a query can be added to the cache by using the Add query result button The button Telos Editor inserts the Telos frame of the current object into the Telos Editor 8 1 8 Display queries This dialog displays all visible queries stored in the current object base see figure 8 4 From the list box you can select a query and ask it or load its definition into the Telos editor 6Visible queries are those queries that are not instantiated to the class HiddenOb ject Certain system queries are thus excluded from the display because their purpose in an internal one 90 Class Individual get_object_star class Class Figure 8 3 Frame Browser Ka CBIva ConceptBase User Interface in Java File Edit Browse Options Help History E 02 8 2722 E Specify Parameters for query COUNT AVG_Attribute AngusEmployees AvailableVersions BillsMetaBoss COUNT COUNT _Attribute ConcatenateStrings ConcatenateStrings3 ConcatenateStrings4
209. ows to form complex functional expressions including arithmetic expressions Functions are also regarded as special query classes Subsequently we introduce first how to define and use functions like queries Then we define the syntax of functional expressions and the definition of recursive functions such as the computation of the length of the shortest path between two nodes 14 2 5 1 Functions as special queries Assume that an attribute either explicit or derived has at most one filler For example a class Project may have attributes budget and managedBy that both are single valued A third attribute pro jMember 1s multi valued 14 A function returns the empty set nil if it is undefined for the provided input values 38 Project with attribute single budget Integer managedBy Employee attribute projMember Employee end The two functions Project Budget and ProjectManager return the corresponding objects ProjectBudget in Function isA Integer with parameter proj Project constraint cl proj budget this end ProjectManager in Function isA Employee with parameter proj Project constraint cl proj managedBy this end The two functions share all capabilities of query classes except that the parameters are required one cannot call a function without providing fillers for all parameters and that there is at most one return object per input value Function can be called just like queries for e
210. pdate to the database or when the maximum number of facts in the cache is exceeded The maximum number is currently set to 50000 If necessary the cache emptying takes place before a transaction The keep mode is on average consuming more main memory than the transient mode but speeds up response time enormously in case of re use of query results c transient The cache is emptied before each transaction ask tell untell retell A subsequent query is always evaluated starting with an empty cache This mode is somewhat safer than the keep mode since it starts each query with an empty cache state While the answer to a query is in principal independent from the cache mode the cache mode has a certain influence on the persistence of 80 objects created within a transaction Specifically results of arithmetic expressions computed during one transaction shall be removed after the transaction when the cache mode is transient In cache mode keep these objects continue to exist and are visible to future transactions By default the cache mode is set to keep Some statistics on cache usage are written to the terminal window of the ConceptBase server when the tracemode has been set to high or veryhigh Acknowledgements Some techniques for the cache based query evaluator are inspired by the tabled evaluation CW96 Wo do however not delay the evaluation of negated predicates but rather re order them at compile time to gu
211. perty is that each solution of a substituted or spezialized form is also a solution of the generic query This is a similar to the inheritance paradigm The example shows that parameters can be retrieved or computed attributes at the same time note that variable for the parameter in the constraint is prefixed here with you may also omit the prefix in the constraint as explained above What_SI_Manager in GenericQueryClass isA Manager UnionMember with retrieved_attribute parameter salary HighSalary 32 u Union computed_attribute parameter head_of Department constraint well_off_rule this union u and head_of head this end There are two kinds of specializing generic query classes 1 Specialization of a parameter a C Example What_SI_Manager salary TopSalary In this case TopSalary must be a subclass of HighSalary The solutions are those managers in What_SI_Manager that not only have a high but a top salary 2 Instantiation of a parameter v a Example What __SI_Manager Research head_of The variable head_of is the replaced by the constant Research which must be an instance of Department One may also combine several specializations e g What_SI_Manager salary TopSalary Research head_of The specialized queries can occur in other queries in any place where ordinary classes can occur e g QueryClass FavoriteDepartment isA Department with retrieved_attribute head What_SI_Manager 10000 salary
212. ployee with computed_attribute sumsalary Real constraint c sumsalary SUM_Attribute Employee salary this end 40 3 Complex computations can be made by using multiple functions in a row This query returns the percentage of query classes wrt the total number of classes Function PercentageOfQueryClasses isA Real with constraint c exists i1 i2 Integer r Real il COUNT QueryClass class and i2 COUNT Class class and x DIV il r1 i2 r2 and this MULT 100 r1 r r2 end The query can be simplified with the use of function shortcuts to Function PercentageOfQueryClasses isA Real with constraint c this MULT 100 DIV COUNT QueryClass COUNT Class end and with arithmetic expressions to Function PercentageOfQueryClasses isA Real with constraint c this 100 QueryClass Class end The function PercentageOfQueryClasses has zero parameters You can use it as follows in logical expressions S PercentageOfQueryClasses gt 25 5 So a function call F calls a query F that has no parameter Functions that yield a single numerical value can directly be incorporated in comparison predicates For example the following query will return all individual objects that have more than two attributes ObjectWithMoreThanTwoAttributes in QueryClass isA Individual with attribute constraint cl COUNT_Attribute Proposition attribute this gt 2
213. pplications is the recording of creation and modification dates ConceptBase stores the creation time of an object in its object base primary for the use of Rollback queries With the predicate Known x t the time of the creation of x can be made visible in rules or queries The following frames shows how to use it Class Employee with attribute salary Integer createdOn TransactionTime lastModified String rule createdOnRule forall t TransactionTime Known this t gt this createdOn t end The limitation of this approach is that it just records the creation date of an object and not the time when it was modified i e the value of an attribute was changed To overcome this restriction one can use an ECArule to update the attribute LastModified of the above example whenever an attribute of the category salary is inserted ECArule LastModified_Employee_salary with ecarule er t1 t2 TransactionTime y Employee i Integer es Employee salary lab Proposition ON Tell A y salary i IF A y lastModified tl DO Untell A y lastModified t1 Ask new In es Employee salary Ask new P es y lab 1 Ask new Known es t2 Tell A y lastModified t2 ELSE Ask new In es Employee salary Ask new P es y lab 1 Ask new Known es t2 Tell A y lastModified t2 5Since ConceptBase 6 2 LPI plug ins can be defined in two different formats A file wit
214. ps of ConceptBase users The owner of a resource will always have full access via rules rr1 and rr2 Then the user would claim ownership to the module via CB_User jonny with owner_resource rl Mjonny end Then only jonny can switch to the module Mjonny If a second user like mary was to be granted read permission jonny would define within module Mjonny CB_User mary with permitted_read rl Mjonny end In the above example rights can also be granted to groups of users and then inherited to its members via rules rr 4 to rr6 It should be noted that the definitions of owner_resource permitted_read and permitted_write are just for illustrating what is possible ConceptBase only requires the query class CB_Permitted in the module where the access rights need to be enforced If such a query class or a local version as explained below is not defined then any access is permitted for any user When a user attempts to switch to new module context ConceptBase checks whether the user has at least read permission 1 e permission for executing the operation ASK on the module If permission is not granted the user cannot switch the module context and an error message is presented The definition of the query CB_ Permitted is visible in the module where it is defined and in all sub modules of this module One can also define a local version of the query by appending the module name to its name e g CB_PermittedMjonny This version is only tested for
215. put The CBserver and pass it to subsequent programs as input To do so you should start the CBserver with tracemode no and using the showAnswer command of CBshell to specify the elements to be written to standard output The CBshell script below realizes the extraction of Graphviz http graphviz org specifications from ConceptBase cc Command startServer u nonpersistent t no tellModel ERD graphviz2 tellModel UniversityModel ask ShowERD UniversityModel erd OBJNAMES FRAME Now showAnswer exit The complete example is available from the CB Forum at http merkur informatik rwth aachen de pub bscw cgi 2519759 Another resource for CBshell scripts is the list of test scripts at http merkur informatik rwth aachen de pub bscw cgi 2596438 85 Chapter 8 The ConceptBase Usage Environment The ConceptBase User Interface consists of two main applications CBiva or CBworkbench is the ConceptBase Interface in Java that supports the editing of Telos frames displays instances of Telos objects etc CB Graph Editor or CBEditor is a graphical browser for Telos objects Telos objects can be represented by differented graphical types Insertion and deletion of Telos objects is also supported The interface is based entirely on Java so it should be usable on all platforms with a Java 1 4 or 1 5 virtual machine The Java interface includes a graphical browser and editor Both applications CBiva
216. r Rainer Gallersd rfer Michael Gebhardt Matthias Jarke Manfred Jeusfeld Thomas List Hans Nissen Christoph Quix Ren Soiron and Martin Staudt Major contributions to the source code of ConceptBase were made by Lutz Bauer module system Rainer Gallersd rfer object store Manfred Jeusfeld CB server logic foundation function component Eva Kriiger integrity component Thomas List object store Hans Nissen module system Christoph Quix CB server view component Christoph Radig object store Ren Soiron optimizer Martin Staudt CB server query component Kai von Thadden query component and Hua Wang anwer formatting Additional contributions came from Masoud Asady Markus Baumeister Ulrich Bonn Stefan Eherer Michael Gebhardt Dagmar Genenger Michael Gocek Rainer Hermanns David Kensche Andr Kle mann Rainer Langohr Tobias Latzke Xiang Li Yong Li Farshad Lashgari Andreas Miethsam Martin P schmann Achim Schlosser Tobias Sch neberg Claudia Welter Thomas Wenig and others Contents 1 Introduction L1 Background sad History soso crrsriss rss OL EEE eS LIA Telos nds EOS e io o id EES da 12 The srchitecture at ConceptBasg C cirrosis a ER Ree 1 3 Hardware and software requirements 000000002 eee la Overview CU bis mantal c saso kh A a a AS 15 Diff rences to earlier versions sc c c vac eardere te p a a ee ea LG Liecnse emis ok a Se a ea E Se OS a E EA a Eke o 2 O Telos by Conc
217. ransaction time A few other features like the declarative TELL UNTELL and RETELL operations as proposed by Manolis Koubarakis in his master thesis on Telos were only implemented in a rather limited way essentially forbidding direct updates to derived facts On the other hand O Telos extends the universal object representation to any piece of explicit information and reduces the number of essential builtin objects to just five So some of the roots of Telos in artificial intelligence were abandoned in favor of a clear semantics and of better capabilities for meta modelling Since we wanted to be able to manage large knowledge bases millions of concepts rather than a few hundred we decided to select a semantics that allowed efficient query evaluation Telos included already features for deductive rules and integrity constraints Thus the natural choice was DATALOG with perfect model semantics The deductive rule evaluator and the integrity checker were ready in 1990 A query language query classes followed shortly later O Telos exhibits an extreme usage of DATALOG e There is only one base relation P o x l y called P facts used for all objects classes meta classes attributes class membership relationships and specialization relationships as well as for deductive rules integrity constraints and queries e The semantics of class membership specialization and attribution is encoded by around 30 axioms which are either deductive rules
218. redicate Q The following example shows the translation QueryClass Well_off_SI_Managerl isA SI_Manager with retrieved_attribute union Union constraint well_off_rule exists s HighSalary this salary s end The generated deduction rules for this query class are forall this v this in SI_Manager and this union v and v in Union and exists s s in HighSalary and this salary s gt Well_off_SI_Managerl this v forall this v Well_off_SI_Managerl1 this v gt this in Well_off_SI_Manager1 Classes occuring in a query constraint may be query classes themselves e g HighSalary This is the third way of query recombination The next feature introduces so called computed attributes i e attributes that are defined for the query class itself but not for its super classes The assignment of values for the solution is defined within the query constraint Like retrieved attributes computed attributes are included in the answer predicate so that the proper answer can be generated from it The following example defines a computed attribute head_of that stands for the department a man ager is leading The attribute head_of is supposed to be computed by the query It is not an attribute of SI_Manager or its super classes We expect that and answer to the query includes the computed attribute Note that a reference head_of to the computed attribute occurs inside the query constraint QueryClass Well_off_SI_Manager2
219. removed is transformed into a set of Telos frames and transferred to the server 8 2 5 Popup menu The popup menu is activated by a click on the right mouse while the cursor is located over an object 98 Toggle component view switches the view of this object In the detailed component view you can either see the frame of this object or tree like representation of super and subclasses instances classes and attributes of this object see figure 8 8 e Super classes sub classes classes instances for each menu item you can select whether you want to see only the explicitly defined super classes or sub classes etc or all super classes including all implicit relationships The query to the Con ceptBase server to retrieve this information will be done when you select the menu item So the construction of the corresponding submenu might take a few seconds e Incoming and outgoing attributes The Graph Editor will ask the ConceptBase server for the attribute classes that apply to this object For each attribute class it is possible to display only explicit attributes or all attributes as above The attribute class Attribute applies for every object and all attributes are in this class Therefore all explicit attributes of an object will be visible in this category However there will be no attributes shown in the All submenu as it would take too much time to compute the extension of all implicit attributes e Add Inst
220. replace this meta formula by a set of semantic equivalent formulas which contain no class variables In previous releases properties as single or necessary had to be ensured manually by adding a constraint for each such attribute This job is now performed automatically by the system Example necessary and single The following meta formula ensures the necessary property of attributes which are instances of the cat egory Proposition necessary The semantics of this property is that for every instance of the source class of this attribute there must exist an instantiation of this attribute Class with constraint attribute necConstraint forall c d Proposition p Proposition necessary x m VAR P p c m d and x in c gt exists y VAR y in d and x my end It reads as follows For each attribute with label m between the classes c and d which instantiates the attribute Proposition necessary and for each instance x of c there should exist an instance y of d which is destination of an attribute of x with category m One should notice that the predicates In x c and In y d cause this formula to be a meta formula The instantiation of x and m to the class VAR is just a syntactical construct Every variable in a constraint 133 has to be bound to a class This restriction is somehow contrary to the concept of meta formulas and the VAR construct is a kind of compromise The resulting In predicates are discarded during the
221. rg gt lt literalArgList gt lt literalArg gt lt literalArg gt gt lt objectname gt lt arExpr gt gt lt arExpr gt lt arTerm gt lt arExpr gt lt arTerm gt lt arTerm gt lt arTerm gt gt lt arTerm gt x lt arFactor gt lt arTerm gt lt arFactor gt lt arFactor gt lt arFactor gt gt lt arExpr gt lt objectname gt lt funExpr gt lt selectExpA gt gt lt selectExpA gt lt selector gt lt selectExpA gt lt selectExpA gt lt label gt un T ECTOR1 SELECTOR2 lt selector gt gt lt deriveExp gt gt lt label gt lt deriveExpList gt lt label lt plainArgList gt lt funExpr gt 118 lt funExpr gt gt lt label gt lt label gt lt plainArgList gt lt deriveExpList gt gt lt singleExp gt lt deriveExpList gt lt singleExp gt gt lt singleExp gt lt literalArg gt lt label gt lt label gt lt label gt lt plainArgList gt gt lt literalArg gt lt plainArgList gt lt selectExpB gt lt selectExpB2 gt lt restriction gt lt objList gt gt lt literalArg gt A label gt SELECTORB lt label gt lt label gt SELECTORB lt selectExpB2 gt label gt SELECTORB lt restriction gt O A lt selectExpB gt lt restriction gt SELECTORB lt la
222. riable this Continuing our running example the following formula is a deductive rule that defines the boss of an Employee Note that the variables e m are fora11 quantified Employee with rule BossRule forall e Employee m Manager exists d Department e dept d and d head m gt e boss m constraint SalaryBound forall e Employee b Manager x y Integer e boss b and e salary x and b salary y gt x lt y end The second formula is an integrity constraint that uses the boss attribute defined by the above rule The constraint demands a salary of an Employee does not exceed the salary of his boss Note that you can define multiple salaries for a given instance of Employee The constraint is on each individual salary not on the sum Also note that the arguments of the lt predicate are bound by the two predicates with attribute label salary 10The enforcement of the restriction has been extended to query classes as of ConceptBase release 6 1 To support applications that were written for earlier releases a CBserver option cc predicate typing has been introduced to disable the check for query classes Details are in section 6 With ConceptBase 7 2 March 2010 the predicate typing has been further extended and now will scan subclasses of of the classes of x in attribution predicates x m y in case that superclasses do not provide a matching attribute class You need to se
223. rolog predicate for example a Prolog predicate defined as a CBserver plug in see appendix F Retell actions are combining an Untell and a Tell in particular for assigning a new attribute value e g Retell e salary newsalary Optionally one can specify an ELSE part which consists of actions that are executed when the IF part is not satisfiable for any binding of the free variables The Ask action is only useful for ECArules that have an ELSE part In this case the Ask will retrieve information from the database that cannot be retrieved within the IF part The special action reject will abort the complete transaction that directly or indirectly triggered the ECArule The effect of ECArules is subject to the regular integrity checking of ConceptBase If an integrity violation is detected then the whole transaction including all updates by ECArules is rolled back The integrity test is started after all enabled ECArules have fired 4 1 Definition of ECArules In ConceptBase active rules are defined similar to query classes The user has to create an instance of the builtin class ECArule The following frame shows the Telos definition of the class ECArule Class ECArule with attribute ecarule ECAassertion priority_after ECArule priority_before ECArule mode ECAmode active Boolean depth Integer rejectMsg String constraint 57 end A correct ECArule must specify at least the attribute ec
224. rver tellFrames bill in Employee end cbserver makeName Id A converts an object identifier to a readable object name cbserver makeld A Id converts an object name Prolog atom into an object identifier cbserver arg2val E V transforms an argument either an object identifier or a functional expression to a value a number or a string The value can then be used in Prolog style computations such as arithmetic expressions cbserver valarg V I transforms a Prolog value number string to an object identifier possibly by cre ating a new object for the value cbserver concat X Y concats the strings Prolog atoms contained in the list X The result is returned in Ls Note that ConceptBase internally manages concepts by their object identifier The programming in terface instead addresses concepts and objects by their name i e the label of the object or the Prolog value corresponding to the label You may have to use the procedure makeName and makelId to switch between the two representations The two procedures arg2val and val2arg are useful for defining new builtin functions on the basis of Prolog s arithmetic functions Assume for example that the object iden tifier id123 has been created to correspond to the real number 1 5 Then the following relations hold makeName 1d123 1 5 arg2val id123 1 5 Hence makeName returns the label 1 5 whereas arg2val returns the number 1 5 The interface shall be extended in the f
225. s o o eneas S34 DisplayiE objects lt lt ssc ereed batoe ra A ew ae a eS gaS Browsing pbj ee co nee e a aa e oS 8 3 6 Editing Telosobpects o e esec a A ee ee So Usinedhe query Tac gt lt ocio be a haa ed e bee 4 eb BA WEBS AS Applets cee YAK Slee BE RR See oY Ee A Se EE Bee So Sonn gone sc 3 ae eae PE eee ORES Se Cae Gees BBE OS A Syntax Specifications A l Syntax specifications for Telos frames o e e A 2 Syntax of the rule and constraint language AA Syma OL ACUC NSS aa a AA a A AA Terminal symbols occ hw eee he A ee ee A 5 Syntax specifications for SML fragmentS e B O Telos Axioms C Graphical Types Cl Thepraphical ype model s oc cis ar e a ae ka e a o 2 The standard praphical types o cenres ee a e we S C21 The extended graphical type model occ cre aa RAE 2 2 Detault dremiieel pes s pe dope RP we ee Re RE a C2 Customizing the graphical types ceci sados 889 bead es C3 1 Properties of CBladividual and CBLink gt e seco sees Ree ee Ee Re C 3 2 Providing a new implementation for a graphical type E BAPE bh Reh RE eA A ee Re eae Boe aS 84 84 84 84 86 86 87 89 89 89 90 90 90 90 92 92 93 95 95 98 99 101 102 102 102 103 104 104 106 108 109 112 116 116 117 119 120 120 123 D Examples 131 Di Example model The Employee model 5 55 8 5 242 e Yb eee w
226. s are functions that do not operate on values suchs as integers but rather on classes such as the class of all employees with more than two co workers ConceptBase provides a collection of aggregate functions that operate on classes For example the COUNT function returns the number of instances of a class The input of such a function can be any nested query call QueryClass EmployeeWith2RichCoworkers isA Employee with constraint c2 COUNT RichCoworker this worker class 2 end The outer predicate here COUNT is an instance of Function i e delivers at most one value for the given argument It is also possible that both operands of a comparison predicate are nested expressions QueryClass EmployeeWithMoreRichCoworkersThanWilli isA Employee with constraint c2 COUNT RichCoworker this worker class gt COUNT RichCoworker Wi11i worker class end ConceptBase supports shortcuts for query calls and function calls see section 2 5 in case that all pa rameters of a query or function have fillers in the query call In such cases one can write Q x1 x2 instead of 0 x1 p2 x2 p2 ConceptBase shall replace the actual parameters x1 x2 etc for the parameter labels p1 p2 in the alphabetic order of the parameter labels For example the expression RichCoworker this is equivalentto RichCoworker this worker since worker is the only parameter label of the query Likewise COUNT c is a shortcut for COUN
227. s exported from a module and to modules imported by a module Module with attribute contains Proposition exports Proposition imports Module end In order to allow other modules to import objects from a module we need to define an export attribute from the module object to those objects We call the set of objects exported by a module the export interface of a module In order to include the export interface of another module to a module we need to define an import s attribute from the module object to the module to be imported In our running example we would like to define a specialization of the Class Employee within the Work module It is desirable to reuse Employee from the Master module instead of redefining it in the Work module In order to import the class Employee to the Work module we have to define all objects belonging to the Employee class as exported objects First change the module context to Master Now TELL the following Frame 69 Master with exports el Employee e2 Employee name end Now you have defined the objects Employee and Employee name as exported objects of the Master module Any module in your database which defines an import s attribute to the Master module can now reference these objects Now change the module context to Work and TELL the follow ing Frame Work with imports il Master end Now the objects mentioned above are visible in the context of
228. s if the proper predicates In x c and A x n y can do the job 2 2 2 Notes on attribution The attribution of objects in O Telos is more generic than in object oriented approaches in particular UML In O Telos an attribution relates two arbitrary objects In languages such as UML attributes are defined at classes to declare which states an object instance of the class may have This is well possible in O Telos as well e g by declaring the integer valued salary attribute of a class Employee and using it for instances of the class However O Telos does not restrict attributes to just values The target of an attribute can be any object Hence the concept of an attribute in O Telos is the generalization of an UML association and an UML attribute A second difference is that an O Telos attribute has essentially several labels tagged to it its own label object label and the labels of its attribute categories class labels The latter are the labels of the attributes declared at the classes of an object the first is the label of the attribution at the level of the object that has the attribute We illustrate this subsequently Attributes at the instance level are instances of attributes at the class level attribute categories An attribute category at the class level can be instantiated several times at the instance level For example consider the frame for Mary mary in Manager with name aliasname hername Mary Smith salary ear
229. s is i5 cb workbench CBIvaApplet class and for the CB Graph Editor the main applet class is i5 cb graph cbeditor CBEditorApplet class 109 E localhost4001 Cancel E localhost 4001 Deparment Und rall e Employee m Mana A bossar Address in Class Ok Cancel Figure 8 23 Adding an instantiation link between Address and Class For example to include the CB Graph Editor as applet inside your web page use the following applet tag lt applet archive cb jar jg13 1 0 jar code i5 cb graph cbeditor CBEditorApplet class width 10 height 10 gt lt applet gt 110 E localhost4001 Individual Employee Employee in Class SimpleClass with attribute name String salary Integer dept Department boss Manager education String address Address Robert in AngusEmployees fend E Telos Editor AngusEmployees in QueryClass isA Employee with Edward in AngusEmployees Ae i i fend c this boss Angus end Bill in AngusEmployees fend History Window Figure 8 25 Query class and its answer The archive parameter specifies the names of the archives to be loaded the code parameter is the name of the applet class to be startet As we have not specified a codebase parameter the JAR files have to be located in the same directory as th
230. s shown by the appearing message box Changes committed If an error occurs an error message will displayed instead The graphical editing is an alternative to the textual editing via the Telos Editor It is appropriate for incremental changes to a model Larger changes should better be made via the Telos Editor or even to an external text file that is loaded via the File Load Model facility of CBiva If the changes were successfully told to the ConceptBase server the Graph Editor reloads the information of every visible object In particular the graphical types of the objects will be updated As the object Address is declared as instance of Class it will get the graphical type of a class i e a turquoise box The result is shown in figure 8 24 The object Employee is shown in the detailed component view in this case the frame representation of the object is shown As you can see the attribute address is now also visible in the frame representation 8 3 7 Using the query facility Lets assume that we need to ask the server for all Employees working for Angus We open a new Telos Editor see menu item Browse Then we define a new query class AngusEmployees as follows AngusEmployees in QueryClass isA Employee with constraint c this boss Angus end 108 LE GBiVa Gonceptbase User Interface in Java Se eo File Edit Browse TT History Windows Help ELE attribute name String salary Inte
231. s the end time of tt The argument t is represented like with Known An object that has not yet been untold has the end time tt infinity 12 x in mc or In2 x mc The object x is an instance of class c and c is an instance of class mc In other words x in mc is equivalent to exists c VAR x in c and c in mc 13 x m y orA2 x m y The object x and y are linked by an attribute al The attribute a1 is an instance of an attribute a2 which itself is an instance of an attribute a3 with label m The predicate is equivalent to the formula exists c d n VAR x in c and y in d and c m n d and x n y The predicates In2 and A2 are also called macro predicates since they are standing for sub formulas They are fully supported in constraints of query classes The predicate A2 is not yet supported for deductive rules and integrity constraints due to limitations of the formula compiler You can use the AL predicate instead Examples on using macro predicates are available from the CB Forum http merkur informatik rwth aachen de pub bscw cgi 877047 The relation of the above predicates and the P facts of the object base is defined by the O Telos axioms appendix B For example axiom 7 states Vo x n y p c m d P o x n y AP p c m d A In o p gt AL x m n y So if an attribute object o of an object x is an instance of an attribute object p of the object c then AL x m l1 y also written as x m n y can be derived This axio
232. se it also contains the history window which records all operations for later reuse In the following each component of the user interface is explained CBiva is compatible to Java 1 4 and Java 5 It is also compatible with Java 6 Update 12 or earlier 2Note that you might have to edit these files so that the correct Java Virtual Machine is used and the environment variable CB_HOME is set correctly See Installation Guide for details 86 Clear Cut Copy Paste Tell Untell Retell Ask Load Object Exit AR Concept Base User Interface in Java Connect Individual Class in Class with attribute constraint MSFOLconstraint rule MSFOLrule Main Telos mrule MRule Editor History Window See a Version Now Module System 1613 B ooo o Figure 8 1 Main Window of CBiva 8 1 1 The menu bar File Connect Connect to a ConceptBase server started in another shell command window see section 6 Disconnect Disconnect from a ConceptBase server Load amp Save Telos Editor Load or Save the contents of the current Telos Editor Load Model Load a source model file sml into the server As client and server are not supposed to share the same file system this method is now implemented as a normal Tell method The client reads the contents of the file into a string and sends the string to the server Start CBserver Opens a dialog and asks for the parameters to start a ConceptBase server If the information has been entered the
233. sk van well update the database It is possible to use variables as a placeholders for parameters in the Ask event clause The event detection algorithm takes only extensional events into account Events that can be deduced by arule or a query are not detected However the algorithm is aware of the predefined Telos axioms e g if an object is declared as an instance of a class the object is also an instance of the super classes of this class 4 1 3 Conditions The condition IF part of an ECArule consists of predicates combined by the logical operators and or and not Quantified sub expressions forall exists are not allowed You can however use query classes to encode such sub expressions The arguments of the predicates are either bound by the ON part of the ECA rule or they are free variables When an event occurs that fires an ECArule then the condition is evaluated against the database yielding bindings for the free variables Each such binding will be passed to the action part of the ECArule Note that ECArules without any free variable are also possible By default predicates are evaluated against the old state of the object base i e before the transaction started If a predicate has to be evaluated on the new database state i e the intermediate state representing the updates processed so far during the transaction then it has to be quoted by the backward apostrophe for example x in Class instead of x in Cl
234. ss a cross like the red cross Diamond a diamond rhombus DoubleArrow a horizontal arrow pointing in both directions Ellipse Ellipse Hexagon Octagon Pentagon as the name says Rect a rectangle RoundRectangle a rectangle with round corners Star a star Triangle a triangle XCross a cross in the form of an X The class GraphShapePolygon is the base class for most of the shapes defined here and might be used to define your own shapes Its constructor is identical with the constructor of java awt Polygon public GraphShapePolygon int xs int ys int num xs and ys describe the coordinates of the corners of the polygon and num is the length of the array xs or ys Start and end point should be identical For example to define a triangle you need the following code import i5 cb graph shape GraphShapePolygon public class Triangle extends GraphShapePolygon private static int xpoints 0 2 4 0 private static int ypoints 2 0 2 2 public Triangle super xpoints ypoints 4 130 Appendix D Examples D 1 Example model The Employee model The Employee model can be found in the directory CB_HOME examples QUERIES It consists out of the following files Employee_Classes sml The class definition Employee_Instances sml Some instances for this model Employee_Queries sml Queries for this model Note that the files must be loaded in this order into the server D 2 A Telos
235. start up time The module sources must have file names starting with System and file type sm1 Typically they are generated via the save flag in the preceding session of the CBserver The default is none i e no module sources are loaded at CBserver start up save dir specifies the directory into which to save certain textual excerpts of the database in particular module listings The parameter has the default value none which disables the saving function Currently the CBserver only saves module listings Each module is stored in one file with file type sml The directory dir must exist The module listing is performed when the CBserver is shut down complete module tree is listed or when a client tool logs out home directory tree of the client tool is listed The module listings uses the set module directive to enable the import of the file to the right module location views dir specifies the directory into which the results of certain queries are materialized See section 5 9 for details 3The concerned class is a consequence of the predicate typing condition of section 2 2 You can roughly compare it to typing of variables in programming languages 79 rl rlmode controls the way how labels for generated formulas are shaped The default value is on in structing ConceptBase cc to find a readable label for the generated formula It typicall consists of the labels of the participating metaclass attributes occuring in the metaformu
236. stent is defined containing all role links which violate the constraint These inconsistent links get a different graphical type e g a red coloured attribute link than consistent role links to visualize the inconsistency graphically KOK KK KKK KK KK OK KR KK KK KK KK KK RK RK KK KKK S File ERIncons x Definition of a Class Inconsistent x x containing roles violating the 1 x gt x constraint x KK A RK KK OK OK IK RK OK OK OK OK OK kK kk K amp S new attribute category revNec for attributes which are reverse necessary Class with attribute revNec Proposition end x roles with 1 must fullfill revNec property RelationshipType with rule attribute revNecRule forall ro RelationshipType role A ro minmax 1 gt In ro Class revNec end definition of Class Inconsistent x x forall instances p of Class revNec If there exists a destination class d there must be a source class c with an attribute instantiating p otherwise p is inconsistent Class Inconsistent with rule attribute revNecInc forall p Class revNec exists c m d VAR y VAR P p c m d and In y d and not exists x VAR In x c and A x m y gt In p Inconsistent end To activate the different graphical representation of inconsistent roles the definition of the graphical type for attributes has to be modified Tell the following frame Inconsistent with rule attribu
237. t the CBserver option cc to extended to activate this behavior The extended mode creates more cases that the predicate type concerned class is found It should be noted that objects like x that are not instance of a class that defines and attribute with label m will lead to a failure of the predicate x m y i e its negation is then true Use multi sets as discussed in http merkur informatik rwth aachen de pub bscw cgi 2330042 if you want to constrain the sum of salaries 25 2 2 9 Meta formulas Some formulas violating the predicate typing condition can be re written to a set of formulas that do not violate the condition The so called meta formulas are a prominent category of such formulas They have occurrences of x in c and or x m y where c or mare variables also called meta variables In such cases the concerned class cannot be determined directly even though the formula as such is mean ingful ConceptBase relies on predicate typing for the sake of efficiency and static stratification The concerned class is internally used as predicate name This increases the selectivity and reduces the chance on non stratified deduction rules Fortunately all meta formulas can be re written to formulas fulfilling the predicate typing condition The re writing replaces the meta variables by all possible value Since all vari ables are bound to finite classes the re writing yields a finite set of formulas However if a meta variable is
238. tance of Class Therefore we select Address hold down the Shift key and select Class Both objects should be selected now We click on the Create Instantiation button and a dialog as shown in figure 8 23 should appear As we have selected the objects in the correct way the dialog already specifies the object we want to create Address in Class and we can click directly on Ok The new instantiation link will be added to the graph 107 m CBlva ConceptBase User Interface in Java lada 083 1045 ANA a E Telos Editor ARO nae Employee in Class SimpleClass with attribute name String salary Integer dept Department boss Manager rule bossrule forall e Emplowl History Window Function GenericQueryClass GetjavaGraphicalPalette GetjavaGraphicalType GraphicalPalette Telos Editor COMTE Query sucessta Version Now Module System 10 32 0 04 Figure 8 20 The TelosEditor Field with the object Employee Now we are satisfied with our changes and want to commit them in the server So far the changes have been stored in an internal buffer of the Graph Editor and have not been sent to the server We click on the Commit button in the upper right corner The Graph Editor generates now Telos frames for the added objects and sends them to the server If we did not make an error all changes should be consistent and accepted by the server This i
239. tch all an answer object for which none of the graphical types of the current palette is specified is presented using the default graphical type of that palette C 2 The standard graphical types The Graph Editor is implemented using the Java Programming Language It is entirely based on the Swing toolkit package javax swing The graphical objects shown in the Graph Editor are all instances of the class JComponent in the javax swing package User defined representations of objects can be provided by overwriting a specific class of the Graph Editor details are given below C 2 1 The extended graphical type model Based on our experience with the old graph browser for X11 we have extended the graphical type model for the Graph Editor First the class GraphicalType has been specialized by a class JavaGraphical Type Class JavaGraphicalType isA GraphicalType with attribute implementedBy String property String priority Integer attribute rule rPriority forall jgt JavaGraphicalType not exists i Integer A_e jgt priority i gt A jgt priority 0 end Individual DefaultIndividualGT in JavaGraphicalType with attribute property bgcolor 210 210 210 textcolor 0 0 0 linecolor 0 0 0 shape i5 cb graph shapes Rect attribute implementedBy implBy i5 cb graph cbeditor CBIndividual end The object Default IndividualGT is an example for the instantiation of a graphical type The attribute implemen
240. te incRule forall e Attribute In e Inconsistent gt e graphtype InconsistentGtype end The effect of these transactions can be shown when starting the Graph Editor and displaying the at tributes of the RelationshipType instance Works In Be sure to switch the graph editor to the palette ER_GraphBrowserPalette before doing so see section 8 2 The attribute WorksIn emp is dis played as red link like in figure D 1 If you had already started the graph editor before telling the last frame you should synchronize it with the CBserver via the menu Current connection By telling H_CB in WorksIn with 137 emp hIsEmp Hans prj cbIsPrj ConceptBase end the inconsistency is removed from the model To see the update of the graphical type in the Graph Editor you have to select the inconsistent link and select Validate and update selected objects from the Current connection menu EN ConceptBase Graphical Editor File Edit ae Current connection mProjkorEmp onnected with localhost Figure D 1 Graph Editor showing the example model with inconsistent link D 2 3 Limitations and final remarks Metaformulas extend the expressive power of defining rules and constraints for ConceptBase Objectbases The implementation of this mechanism is not complete at the moment but should enable the use of the most frequently requested concepts like single and necessary Some limitations are listed below e limited partial
241. te upon changes to the object base Default value for vmode is of f mc maxcost this parameter defines the maximum cost level for a predicate in a binding path that is used to compile a meta formula see section 2 2 9 The evaulation of a binding path yields fillers for the meta variables Set maxcost to 10 if such a predicate should have about one free variable Set it to 100 if if may have two free variables Default is 100 The higher the number the more candidate paths are generated increasing the likelihood that a binding path is found On the downside a high value increases the compile time of meta formulas pl pathlen set a maximum length for binding path candidates In principle the number of candidates can explode with the path length Like the previous parameter the path length influences the ability of ConceptBase cc to compile meta formulas The default value is 5 If you set the value to 0 then no meta formula can be compiled eca emode controls the ECA sub system Possible values are unsafe ECArules are evaluated without safeguarding recursive deductive rules of f ECArules are not evaluated even if some are defined and safe ECA rules are evaluated with safeguarding recursive rules this is the default Use the mode unsafe if none of your ECArules calls recursive predicates on the newest database state This may lead to some speed up load dir specifies the directory from which the CBserver will load module sources at
242. tedBy specifies the full name of the Java class that provides the implementation for this graphical type This class has to be a sub class of i5 cb graph cbeditor CBUserObject The propert y attribute specifies name value pairs which will be used by the Java implementation to set certain properties e g color shape font The priority value is used to resolve ambiguity if multiple graphical types apply to one object The graphical type with the highest priority will be used The rule specifies a default value of O for the priority The graphical palette has also been extended There are now defaults for different types of objects and graphical types for implicit links can be defined Thus the default attribute defined in Graphical Palette will not be used anymore The contains attribute has still to be used i e a graphical type will only be used if it is also contained in the current graphical palette Although the attributes are not declared IColors are given as RGB color value e g 210 210 210 is light grey and 0 0 0 is black 126 as single and necessary each graphical palette should have at least one and at most one attribute in these categories Class JavaGraphicalPalette isA GraphicalPalette with attribute defaultIndividual JavaGraphicalType defaultLink JavaGraphicalType implicitIsA JavaGraphicalType implicitInstanceOf implicitAttribute JavaGraphicalType JavaGraphicalType end C 2 2 Default graphic
243. tes such as ground 1 to improve the performance of a query or rule Although datalog queries and rules can be used as any other query or rule they can cause an inconsis tent database This is due to the fact that the datalog queries and rules will usually not be evaluated while the semantic integrity of the database is checked 2 7 1 Extended query model Datalog queries are defined in a similar way as standard query classes They must be declared as instance of the class DatalogQueryClass Class DatalogQueryClass isA GenericQueryClass with attribute code String end The attribute code defines the executable code of the query as string Datalog rules have to be defined as an instance of DatalogInRule or DatalogAttrRule de pending on whether their conclusion should be an In predicate or an A predicate Class DatalogRule with attribute concernedClass Proposition code String end Class DatalogInRule isA DatalogRule end Class DatalogAttrRule isA DatalogRule end The attribute concernedClass specifies the class for the In predicate or the attribute class for the A predicate 2 7 2 Datalog code The datalog code is a list of predicates separated by commas As in Datalog or Prolog this will be interpreted as a conjunction of the predicates To use disjunction the code attribute has to be specified multiple times All predicates that may be used in standard rules and queries may also be used in datalog queries se
244. that match the given wildcard expression Only simple wildcards with a star at the end are allowed rename Renames an object from oldname to newname This is a low level operation directly on the symbol table that works directly on the symbol table It only checks whether newname is not already used as label for a different object no other consistency checks are performed The parameters have to be given in the order newname oldname 143 Appendix F CBserver Plug Ins Users with Prolog experience may find it interesting to use the LPI logic plug in feature of ConceptBase server An LPI plug in is essentially a small Prolog program that is inserted into the ConceptBase server code at run time It extends the functionality of the CBserver for example for user defined builtin queries The implementation of pre defined builtin queries see appendix E is part of the CBserver You can create a file like MyPlugin swi 1lpi to provide the implementation for your self defined builtin queries or for action calls in active rules see section 4 You can use the full range of func tions provided by the underlying Prolog system here SWI Prolog http www swi prolog org and the functions of the CBserver to realize your implementation You may consult the the CB Forum for some examples at http merkur informatik rwth aachen de pub bscw cgi 2768063 You find there examples for sending emails from active rules and for extending the set of buil
245. the O Telos language is explained Then the predicative sublanguage for deductive rules and integrity constraints are presented Subsection 2 3 presents a declarative query language which introduces queries as classes with optional predicative membership specification 2 1 Frame and network representation As a hybrid language O Telos supports three different representation formats a logical a graphical se mantic network and a frame representation The two latter formats are based on the logical one As explained in the next subsections the logical representation also forms the base for integrating a predicative assertion language for deductive rules queries and integrity constraints into the frame representation We start with the so called P fact representation of a O Telos object base An O Telos object base is a finite set of interrelated propositions P facts objects OB P oid x 1 y tt loid x y tt ID 1 LABEL 11 where oid has key property within the knowledge base ID is a non empty set of identifiers with a non empty subset LABEL of names The components cid x 1 y tt are called identifier source label or name destination and belief time of the proposition We read them as follows The object x has a relationship called 1 to the object y This relationship is believed by the system for the time tt As shown below there is a natural interpretation of a set of propositions as a directed graph semantic ne
246. the Work module Check this by loading the Employee object with the Load frame function from the CBworkbench You can now define the specialization Manager of Employee in the context of the Work module Manager isA Employee end When untelling export s attributes from a module ConceptBase checks for integrity violation in all concerned modules Try untelling the export s attributes from the Master module and you should get an error message saying that referential integrity is violated in the Work module The reason for this violation is natural as the class Employee is no longer exported from Master it is no longer visible inside the Work module and therefore referential integrity is violated for the Manager specialization of Employee 5 5 Setting user home modules When ConceptBase is used in a multi user setting it makes sense to automatically assign clients of Con ceptBase users to a dedicated module context their so called home module To use this feature the database of the ConceptBase server has to contain instances of the pre defined class CB_User This class is defined as follows CB_User with attribute homeModule Module end Assume that we have two users mary and john who need to be assigned to different modules when they log into the CBserver by their favorite user interface The system adminstrator should then include the following definitions to the database of the CBserver Projectl in Module end Project2
247. the current transaction Deferred The condition is evaluated towards the end of the current transaction If it evaluates to a non empty answer the actions of the DO part of the ECArule are executed immediately after the evalu ation of the condition Otherwise the ELSE actions are executed provided that the ECArule has an ELSE part The answer to the evaluation of the condition of an ECArule is the set of all combinations of variable fillers that make the condition true The modes Immediate and ImmediateDeferred differ considerably from the mode Deferred the condition of the ECArule is evaluated while not all frames of the current transaction are told resp untold So a quoted predicate like x in Class will be evaluated against a database state in which only those frames of the current transaction are visible resp invisible that were told resp untold before the ECArule was triggered The default is Immediate ConceptBase shall enforce a first in first out sequencing of ECArules with modes ImmediateDeferred and Deferred This sequence will enforce the complete execution of a triggered ECArule before the next rule triggering is handled The strict sequencing avoids intertwining of action executions of multiple ECArule threads So if the answer to a condition of an ECArule has multiple entries then the actions belonging to the respective answers are executed in a sequence in which no action of another ECArule is called Ear
248. tin queries and functions F 1 Defining the plug in Once you have coded your file MyPlugin swi lpi there are two ways to plug it into the CBserver The first way is to copy the file into an existing database directory created by the CBserver CBserver d MYDB load Telos definitions then stop the CBserver cp MyPlugin swi lpi MYDB This option makes the definitions only visible to a CBserver that loads the database MYDB The second option is to instruct ConceptBase to load your LPI code to any database created by the CBserver To do so you just have to copy the LPI file into the directory with the system definitions cp MyPlugin swi lpi lt CB_HOME gt lib system where CB_HOME is the directory into which you installed ConceptBase The number of LPI files is not limited You may code zero one or any number of plug in files A couple of useful LPI plug ins are published via the CB Forum see http merkur informatik rwth aachen de pub bscw cgi 2768063 Note that these plugins are copyrighted typically come with their own license conditions that may be different to the license conditions of ConceptBase If you plan to use the plugins for commercial purposes you may have to acquire appropriate licenses from the plugin s authors F 2 Calling the plug in There are two ways to trigger the call of a procedure implemented by an LPI plugin 144 1 By explicitely calling a builtin query class or function whose code h
249. tribute will NOT be shown The Graph Editor uses an internal cache which will only be updated on request Therefore we select the object Employee and select Validate and update selected objects from the menu Current connection The cache for the object Employee will be emptied Now showing all attributes should add the new attribute education to the graph Editing Telos objects using the graph editor Telos objects can also be edited graphically in the Graph Editor In our example we want to add another attribute named address to the class Employee The attribute destination of this attribute should be a new class called Address First we select the object Employee and click on the Create Attribute button in the tool bar or select Add Attribute operation from the tool bar As we have selected the Employee object it should be already inserted as source of the attribute We have to type the label address and the destination of the attribute in the text fields see figure 8 22 As this attribute does not belong to a specific attribute category it is just an attribute we do not have to specify an attribute class By clicking on the Ok button the Graph Editor will create a new object for Address represented by the default graphical type a gray box Then it will create the attribute link from Employee to Address with the label address The result is shown in figure 8 23 Now we want to declare Address as an ins
250. tribute Proposition Proposition attribute single Proposition Note that att ribute has itself as category This is the most generic attribute category and applies to any explicit attribution Both the attribution predicate x m y and its long form x m n y can be derived i e occur as conclusion of a deductive rule In such cases there are no explicit attribute objects between x and y ConceptBase demands that in such cases one of the classes of x has an attribute with label m Deduc tive rules for x m n y are introduced with ConceptBase V7 1 They allow to simulate multi sets i e derived attributes where the same value can occur multiple times The feature is still experimental Ex amples are available in the CB Forum http merkur informatik rwth aachen de pub bscw cgi 2330042 20 2 2 3 Assigning attribute categories to explicit attributes The instantiation of an explicit attribute to an attribute category can be explicit see above or via inheri tance or via a user defined rule Explicit instantiation is typically established when telling a frame like the Employee example to the database Instantiation by inheritance is more rarely used but is in fact just the application of the specialization principle to attribution objects Employee with attribute salary Integer end Manager isA Employee with attribute bonus Integer end Manager bonus isA Employee salary end Here the bonus attribute is declar
251. ts are denoted by appending the attribute label with an exclamation mark to the name of some individual The relationship between salary and earns could be expressed as 3Subsection 2 2 contains an example for this problem in the context of linking logical formulas to O Telos objects 4For specialization relationships between two objects we need an axiom similar to the instantiation axiom which requires special ization relationships between their sources and destination components Jeus92 contains the complete axiomatization 5These instantiations were left out in the set of propositions for the employee example above 15 mary earns in Employee salary end Instantiation links are denoted by the operator gt and specialization links by gt They should always be enclosed in parentheses mary gt Manager end Manager gt Employee end The operators can be combined to form complex expressions The next example shows how to reference the instantiantion link between the attribute mary earns and its attribute class Employee salary The second frame shows that arbitrarily complex expressions are possible The parentheses have to be used to make the operator expressions unique The attribution operator has a stronger binding than the instantiation and specialization operators According to our own experience complex expressions for denoting objects are rare in modeling It is good to know that any o
252. ts reserved See http conceptbase cc for details Abstract ConceptBase cc in short ConceptBase is a multi user deductive object manager intended for conceptual modeling meta modeling and coordination in design environments The system implements O Telos a dialect of Telos integrating properties of deductive and object oriented languages It uniformly represents all information regardless of its abstraction level data class meta class meta meta class etc in a single data structure called P facts The powerful deductive query language is seamlessly integrated into the meta class hierarchy Modeling is supported by meta classing deduction and integry checking active rule specification functional definition of computation a module concept and a historical database allowing to query past states of the database These principles are combined orthogonally e g deductive rules can be contained to modules formulated for meta classes employed in active rules using functional definitions to compute properties and be revised without overwriting the earlier definitions The Java based usage environment offers an extensible palette of graphical tabular and textual user interfaces The communication between the user clients and the object base is organized in a client server architecture using TCP IP Further clients can be connected by an API documented in the ConceptBase programmers manual Contributions to this manual were made by Lutz Baue
253. ts to modules one can also design which user has which read write permissions The builtin query 1istModule allows to save the contents of a module to a Telos source file see section 5 7 6 4 The UNTELL operation ConceptBase cc realizes the concept of a historical database The TELL operation submits O Telos frames to the CBserver The CBserver extracts the novelty of the submitted frames and translates it into a set of P facts to be stored in the object store Any P fact has a so called belief time associated to it see section 2 1 The belief time is an interval t1 t2 whose left boundary t is the time point when the P fact was inserted to the object store i e the time when the transaction was executed that led to the insertion of the P fact The right boundary t2 specifies the time point after which the CBserver assumes the P fact to be 81 not true anymore It is initialized with Now when the P fact is created This symbolic value is interpreted as the current time You may also interpret such a time interval to be right open The UNTELL operation terminates the belief time of P facts specified in an O Telos frame The value Now is replaced by the timet when the UNTELL operation is executed From the user s perspective a TELL operation is about creating some objects and the UNTELL op eration is about deleting them gt Many users expect the UNTELL operation to be symmetric to the TELL operation i e untelling a frame th
254. ture is to allow an easy way to save reload the complete content of a database using a readable source format These sources can be modified with a regular text editor The source files generated by the save function include a set module directive that instructs the CBserver to load the file to the original module path when the load function is invoked or when the file is loaded manually viathe load model function of CBiva see section The file names of the saved loaded module sources consist of a module path starting with the root module name System followed by the file type sml For example a filename System oHome AB sm1 will hold the contents of the module AB that is a submodule to oHome that is a submodule of System The save function is activated when the option save savedir is specified The parameter savedir must be the path to an existing directory If activated the save function is invoked if the CBserver is shut down The CBserver will save the complete module tree starting from the root module System The save function is also invoked when a client tool for example CBiva disconnects from the CBserver In this case only the module tree starting from the home module of the user of that client tool is saved In both cases the save function is executed with the rights of the user who started the CBserver The save function requires at least read permission for the module to be saved The load function gets activated when the option load
255. tware pages 37 48 March 1996 Quix C Sichtenwartung und Anderungsnotifikation fiir Anwendungsprogramme in deduk tiven Objektbanken Diploma Thesis RWTH Aachen 1996 Quix C Schoop M Jeusfeld M A Business Data Management for Business to Business Electronic Commerce SIGMOD Record Vol 31 No 1 pp 49 54 March 2002 Ramesh B Dhar V Process knowledge based group support for requirements engineering Journal Intelligent Information Systems Vol 1 No 1 1992 114 RJG 91 SIGA91 StJa96 Soir96 Stan86 Stau90 TKDE90 Wing90 Rose T Jarke M Gocek M Maltzahn C Nissen H A decision based configuration process environment Software Engineering Journal Special Issue on Software Environments and Factories July 1991 Rich C ed Special Issue on Implemented Knowledge Representation and Reasoning Systems SIGART Bulletin Vol 2 No 3 June 1991 Staudt M Jarke M Incremental Maintenance of Externally Materialized Views In Proc of the 22th VLDB Conference Bombay India 1996 Soiron R Kostenbasierte Anfrageoptimierung in deduktiven Objektbanken Diploma Thesis RWTH Aachen 1996 Stanley M T CML a knowledge representation language with application to requirements modeling M S thesis University of Toronto Ontario 1986 Staudt M Anfragereprdsentation und auswertung in deduktiven Objektbanken Diploma thesis Universitdt Passau 1990 Stonebr
256. twork We distinguish four patterns of propositions and give them the following names Individuals P oid oid 1 oid tt oid is an object with name 1 believed tt InstanceOf relationships instantiations P oid x instanceof y tt x is an instance of class y believed tt IsA relationships specializations P oid x isa y tt and x is a specialization of y believed tt Attributes all other propositions P oid x m y tt and x has an attribute with label m with value y believed tt O Telos imposes some structural axioms on knowledge bases e g referential integrity correct instan tiation and inheritance Jeus92 The complete list of axioms is contained in appendix B The axioms are linked to predefined objects that are part of each O Telos object base e Individual contains all individuals as instances Intuitively individuals are objects that are dis played as nodes in a graph e InstanceOf contains all explicit instantiation objects as instances In the graphical representation an instantiation object is a link between some object x and its class c e IsA contains all explicit specialization objects as instances A specialization object is graphically displayed as a link between a subclass c and its superclass d e Attribute contains all explicit attribute objects as instances An attribute object can be displayed by a link between an object x and the object y The label of the attribute object is th
257. udent members can read the definitions in the module LectureModule An even simpler way to separate the workspaces of any user is to define oHome in AutoHomeModule with exception el mary end mary in CB_User end Then no user needs to be defined explicitely as instance of CB_User and still will get assigned her own sub module to work in One user like mary should be kept as exception because she would work by default on the System module to define objects that are visible to all students The home module definitions need to be made within module oHome because they will be evaluated upon client registration server method ENROLL_ME in this module context Please note that the module context is only dependent on the user name not on the client and not on the network location of the user It could well be that a user mary is defined on multiple computers on the network and that different natural persons are identified by mary 5 6 Limiting access to modules When multiple users work on the same server their workspaces not only need to be separated in a controlled way by means of the module feature Users are also interested in controlling who has which rights on their workspace module ConceptBase includes basic support for rights definition and enforcement via a user definable query class CB_Permitted The signature of this query class has to conform the following format 1A side effect of the server method ENROLL_ME is that t
258. uture to provide more functionality Be sure that you only use this feature if user defined query classes cannot realize your requirements 146
259. wo rules depending on the binding of the variable src The rule defines the transitive closure of the boss attribute Rule r1 is applied if both arguments src and dst are unbound The second rule is used if at least src is bound and the last rule will be applied if we have a binding for dst but not for src DatalogAttrRule MetabossRule with concernedClass 46 cc Employee boss code ri vars m var srce var dst In m Manager A m boss dst A src boss m r2 vars m ground src A src boss m A m boss dst r3 vars m ground dst var src A m boss dst A src boss m end Note that the predicates var and ground are builtin predicates of PROLOG Thus this is also an example for calling PROLOG predicates in a query or rule 47 Chapter 3 Answer Formats for Queries 3 1 Basic definitions By default ConceptBase displays answers to queries in the FRAME format see A and B below For many applications other answer representations are more useful For example relational data is more readable in a table structure Another important example are XML data If ConceptBase is integrated into a Web based information system then answers in HTML format are quite useful For this reason answer format definitions are provided Answer formats in ConceptBase are based on term substitutions where terms are evaluate
260. xample ProjectBudget P1 pro3 shall return the project budget of project P1 if existent You can also use the shortcut Project Budget P1 like for any other query 2 5 2 Shortcuts for function calls and functional expressions Since functions require fillers for all parameters ConceptBase offers also the standard syntax f x to refer to function calls The expression f x is a shortcut for f x param1 where paraml is the only parameter of function f If a function has more than one parameter then they are replaced according their alphabetic order g in Function isA T with parameter x T1 VITEZ constraint end A call like g bill 1000 is a shortcut for g bi11 x 1000 y because x is occurs before y in the ASCII alphabet The shortcut can be used to form complex functional expressions such as f g bill ProjectBudget P1 There is no limitation in nesting function calls Function calls are only allowed as left or right side of a comparison operator They are always evaluated before the comparison operator is evaluated For example the equality operator f g bill ProjectBudget P1 f g mary 1000 39 will be evaluated by evaluating first the inner functions and then the outer functions Note that the parameters must be compliant with the parameter definitions As a special case of functional expressions ConceptBase supports arithmetic expressions in infix syn tax The operator symbols x and are
261. y attribute of a graphical type specifies the class name of a Java class implementing this graphical type This class has to be a subclass of 15 cb graph cbeditor CBUserObject If you are going to implement your own class it is most useful to extend CBIndividual or CBLink in the package 15 cb graph cbeditor The class CBUserObject provides several methods which can be overwritten to implement your own graphical types Component getSmallComponent returns the small component i e the component which is shown first The return value should be an instance of javax swing JComponent although only Java awt Component is required as return value AWT Component will probably not work correctly in the Swing based Graph Editor If the method returns null then the result of getCompo nent will be used to visualize the object Component getComponent returns the main component for this user object This component is used when the small component is not shown To be compatible with the graph editor which is imple mented in JFC Swing the component should be a subclass of JComponent This method may return null but then getSmallComponent must return a value 128 Shape getShape returns the shape for this component Shape is defined in the package java awt and represents any type of shape e g polygon rectangle ellipse etc As said above the shape is shown in the background of the small component so it may not be visible if the small compone
262. y class constraint The computed attribute causes the inclusion of the condition v2 in Department but typically also occurs in the query constraint Like retrieved attributes computed attributes are necessary i e any solution of a query with a computed attribute must assign a value for this attribute There is no limit in the number of retrieved and computed attributes The more of them are defined for a query class the more arguments shall the answer predicate have Recursion can be introduced to queries by using recursive deductive rules or by refering recursively to query classes The example asks for all direct or indirect bosses of bi11 QueryClass BillsMetaBoss isA Manager with constraint billsBosses S bill boss this or exists m Manager m in BillsMetaBoss and m boss this end Further examples can be found in the directory SCB_HOME examples QUERIES Queries are represented as O Telos classes and consequently they can be stored in the knowledge base for future use It is a common case that one knows at design time generic queries that are executed at run time with certain parameters CBQL supports such parameterizable queries GenericQueryClass isA QueryClass with attribute parameter Proposition end Generic queries are queries of their own right they can be evaluated Their speciality is that one can easily derive specialized forms of them by substituting or specializing the parameters An important pro
263. you hit the Commit button in the tool bar Creating Individuals If you want to create a new individual object you just have to specify the object name You have to enter a valid Telos object name for example it must not contain spaces In addition you can select a graphical type for the object Note that the selection of the graphical type has no effect in the database e g by selecting the graphical type of a class ClassGT the object will not declared as an instance of Class If you have performed the commit operation the object will get the correct graphical type from the server Creating Instantiations In the dialog for instantiations you have to enter the name of the instance and the name of the class in the two text fields If the object entered does not yet exist it will be created and represented in the default graphical type Creating Specializations This dialog is similar to the one before except that you specify here the name of the subclass and the name of the superclass Objects that do not exist yet will be created and represented in the default graphical type Creating Attributes This is the most complex dialog as you have to specify the source the label the value and the category of the attribute The source and the value or destination of the attribute are normal object names The label may be any valid Telos label The attribute category has to be a select expression specifying an attribute category e g

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