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1. Types for activities activity Types for activities activity Figure 2 1 Selecting a Type in ELIOOS of type by partner The selection of types by the user and their combination at run time is most effective if the type hierarchy is designed accordingly It should offer maximal flexibility to the user To do this two principles should be respected in the design of the type hierarchy First every type should only contain one single concept or aspect This is the principle of fine grain inheritance described in 3 Second for all types which are not semantically incompatible it should be possible to combine them yielding a type which combines the concepts in a reasonable way These principles motivate the following informal classification of types e A user concept is a type containing a single concept It may be selected by the user to create or specialize an instance A user concept may have other user concepts as supertypes if these concepts are necessary requirements for the new concept Thus in general the user concepts form a hierarchy which is a part of the hierarchy of all types e A user packet is a type which is equivalent to the combination of certain It may be selected by the user and is offered for conve niency reasons User packets are useful for frequently needed user concept user concepts combinations e A designer concept is a type containing a single concept However it is only accessible t
2. Partly the first condition is already guaranteed by the type struct doc which deletes all parts whenever the state of the document becomes undefined Addi tionally the methods create sub and delete sub defined by type collection are enhanced by performing the corresponding state transitions for the document if necessary Specializing a part does a start edit doc transition Creating or putting a part does the same if the state was existent Otherwise the state must be undefined and the transition init doc is performed Deleting performs the transition erase doc if it was the last existing part When a document part is moved this is handled like deleting the part in the source document This is implemented by enhancing the method moved of type homstruct part Note that upward propagation of transitions must be done in a special way Since it is done in reaction to an action in the document the operation associated to the transition is already executed and must not be performed by the transition Thus upward propagation is done by calling the methods begin transit and complete transit directly The method transit step is not used and that is why the method action transit is not called see Section 3 4 2 The second condition is guaranteed by simply propagating the transition fix doc from the document to all parts The third condition is guaranteed by prop agating the transition start edit doc from a part up to the document if nec essary
3. The TACTS core implements objects which represent agents by the type agent In its simplest form an agent is only described by its shortname like any TACTS object The shortname can be used like an alias It is used for interactively specifying an agent and for displaying agent references in other objects Additional informations about agents are implemented by specializations of the type agent Examples for additional information are a name an address a telephone number or an electronic mail address The applicable information depends on the kind of the agent Thus every information item should be defined by a separate type Then for any kind of agent an individual type combination may be specified However for accessing this information in a uniform way the type agent defines the method agent info It is called with a keyword and returns corresponding information if defined No keywords are predefined by 29 with ref with agent by single with partner init by init partner by self inherit by by partner inherit partner Figure 4 3 Activities with Agents type agent all keywords must be defined and implemented by specializations See Section 7 1 1 for an example 4 2 2 Agent Sets Agents are represented by objects and thus belong to a base The type agent set describes collection objects with an associated set named agents Any object may be an agent set If the object represents an activity the agent
4. send doc with agent with headers Areceive doc with agent from headers receive doc with headers send doc with headers two agent trans aeee receive doc with partner with subject header reply trans with newsgroup header reply with sub ject reply with newsgroup Figure 7 3 The Types for Transmission Activities with Header Management with local doc Before a document can be sent out it must be written in contrast to docu ments which are received If the document is local the writing of the document should be a part of the transmission activity Thus the combination supple ment type send local doc used for the combination of the types trans doc send info and with local doc uses the additional type long act to introduce the additional state active see Figure 3 5 During the transition activate it performs the transition init doc at the document Thus instances of type send local doc can be used as follows After their creation they are in state planned the associated document exists and is in state undefined When the user executes the transition activate the document content is initialized Optionally the user may now edit the document one or more times Then the user executes the transition complete and the document content is fixed and sent out 7 2 2 Header Management for Transmission Activities Next types for head
5. 64 7 2 Communication Activities 2 CC En nn 64 7 2 1 Activities for Document Transmission 64 7 2 2 Header Management for Transmission Activities 66 7 2 3 Sending and Receiving Mailand News 67 8 Conclusion 70 il Chapter 1 Introduction In the context of CSCW systems several systems have been developed which try to support collaborative work Among others there are systems for the support of e communication and coordination of the activities of a group of people like the Coordinator 11 or the Strudel toolkit 10 e office procedures like the Domino System 2 or the Prominand System 4 e collaborative editing of documents like Prep 8 or Quilt 1 e other aspects of collaborative work like meeting scheduling and project management However all these systems only attack one aspect or a few aspects of collabora tive work Typically they use only one paradigm such as procedure orientation conversation orientation or form orientation The TACTS system instead tries to integrate many aspects and paradigms in one system Of course it can do so only incrementally by being a frame system that allows the integration of differ ent aspects and paradigms The main requirements to a system of this kind are flexibility and extendibility Consequently TACTS is designed as an environment for the experimental design of a toolkit for supporting collaborative work The importance of fl
6. AT the method start edit doc is implemented by invoking the method show doc parts The second abstract document operation fully implemented by struct doc is the method erase doc It works by simply deleting all document parts This behavior corresponds to the fact that the structure is part of the document content and erase doc does eliminate the current content If method erase doc would only invoke method erase doc for the parts it would only erase the real content but not the structure The user can do this by explicitly calling the method erase doc for single parts Exporting the document to system document is not implemented in the current TACTS version To do this correctly the parts must be copied and their attribute values must be copied in a sensible way as well However the current version of ELIOOS does not support copying of objects It is planned to add this feature to ELIOOS When this is done copying of structured documents by exporting them to document will be implemented as well For documents which have a fixed structure the method init doc can be used to create the necessary document part objects However in the general case no concrete document structure is known Thus the type struct doc inherits this method from type doc without changing it The type struct doc is incompatible with type simple doc however it may be combined with all other document features like history or versioning The type
7. 15 go up M 15 Headers A 64 66 history doc T 41 43 63 64 homstruct doc T 46 48 50 56 immediate T 24 38 import doc M 42 44 47 55 62 67 import doc R 43 49 52 65 in edit S 42 44 49 inherit by T 5 30 32 34 37 inherit partner T 30 32 34 37 init by T 5 30 32 init doc M 41 42 44 47 48 55 init doc R 43 49 52 66 init partner T 30 32 69 intern doc T 51 52 Last change A 42 load doc M 46 51 52 local filed doc T 51 53 long act T 27 29 36 37 44 65 66 mail request T 69 Medium A 33 64 65 68 moved M 7 49 named version doc T 41 45 old 5 50 Partner A 32 33 64 planned S 20 22 24 27 29 37 38 66 procl doc T 54 56 process doc M 55 56 receive info T 33 34 38 65 69 receive mail M 61 receive mail T 69 receive news M 61 receive news T 69 receive via mail T 61 64 68 receive via news T 61 64 68 refined transitions T 19 24 25 reply mail T 69 reply news T 69 Reply of A 33 34 67 reply trans T 33 34 37 66 67 69 request T 35 38 69 request addressee T 36 38 request initiator T 36 38 reset R 28 29 reset act T 28 reset transit M 21 22 restart R 28 29 37 38 restart act T 28 36 37 75 save contentbuffer M 47 search member M 15 31 67 send info T 33 34 38 60 63 65 66 69 send mail
8. If the addressee wants to transmit an additional answer he she uses the transitions restart and complete Note that there is no connection between the initiator role instance and the addressee role instance of the request They are in different user spaces and the system can not check or guarantee the consistency of the instances This will be improved when shared objects enable the maintenance of a common object for the request as a whole On the other hand by separating the roles it is possible that only one of the team members uses the TACTS system to maintain his her role while the other 38 member handles the request without system support informally This greatly im proves the flexibility of use of the system for single users and its wide acceptance 39 Chapter 6 Documents This chapter describes the support of activities involving documents This part of TACTS is carefully designed to support a wide range of document and activity kinds It supports documents stored in electronic form as well as documents held outside of the system The properties of documents in TACTS are discussed in separation in the following sections The first section introduces abstract documents which have a minimum of properties The other sections each describe types for one aspect like the document structure the way it is stored or the version management For every aspect one or more types are defined all of which are specializations of the type f
9. It is planned to support transmission of other documents as well Homo geneously structured documents can easily be supported by either transmitting every component as a separate part or by generating a structured text containing all parts and transmitting this text in one piece The latter can be implemented using an archive mechanism like UNIX shar 7 1 5 Communication and Document History Using the mechanisms described in the previous sections a document can be sent or received several times Since all transmissions are implemented using the document operations export and import every transmission can be protocoled as a subactivity This is done using the history mechanism introduced in Section 6 2 During every export or import transition a subactivity of type basic activity is created and completed Thus it stores the time point of performing the transition However additional history support is added for the special cases of sending and receiving the document content Using combination supplement types the combination of send via mail and history doc adds the types send info two agent trans with headers see Section 7 2 2 and by self to the transition 63 activities created for exports to system email and sets the attributes Medium Partner and Headers Analogously the combination of type history doc with the types receive via mail send via news and receive via news is handled by storing all rel evant information of
10. The operation methods are not designed to be called directly by the user Instead the user interface to the document operations is the general user interface to state transitions 1 e the methods transit step and transit run of type with state The operations are executed during the corresponding transitions Another attribute of doc instances is the time of the last content change called Last change The methods init doc erase doc stop edit doc and import doc set this attribute to the current time It is used for restricting ex 42 export doc export doc import doc C init doc undefined existent fixed erase doc start edit doc gt stop edit doc in edit Figure 6 2 The Automaton of Type edit doc ports to changes There is an additional attribute Export times which records the time of the last export for every possible export target specifically By com paring these time stamps the export method can determine whether the content has to be exported or not 6 2 Document History The history of a document is recorded by protocoling all operations applied to the document 6 2 1 Modeling Document Operations by Subactivities To protocol all operations applied to the document the mechanisms from the basis and core of TACTS are used With the help of refined transition every operation is modeled by an explicit subactivity instance Thus when document history is used the object represents not only the document b
11. agent with email T 60 attach M 9 basic activity T 28 29 31 37 44 63 begin transit M 21 22 49 binary doc T 51 53 54 57 60 63 64 By A 31 by partner T 5 6 30 32 34 by self T 5 30 31 33 63 69 by single T 5 30 31 33 36 60 68 cancel R 28 29 cancel act T 28 canceled S 28 29 charseq hb prepare M 6 charseq hb process M sL 62 charseq prepare M 61 63 charseq process M 61 63 complete R 20 22 27 29 37 38 44 65 68 complete transit M 21 22 49 completed S 20 22 27 29 37 Contentsfile A 52 create sub M 49 created M 7 8 24 25 65 cuttime M 18 19 define version name M 45 delete M 7 delete sub M 13 49 50 delete version name M 45 deref M 12 74 Descr A 12 33 display M 11 13 display subs M 13 display versions M 45 doc T 40 44 46 48 50 53 55 60 62 65 doc set T 46 47 65 Document A 65 Documentroot A 48 edit descr M 12 edit doc T 40 47 54 55 erase doc M 41 42 44 47 48 erase doc R 43 49 existent S 42 44 49 export M 50 export doc M 41 42 44 45 47 62 67 68 export doc R 43 65 Export times A 43 filed doc T 51 52 54 57 finish M 22 23 fix doc M 41 47 fix doc R 43 49 fixed S 42 44 49 follow ref M 12 get contentbuffer M 47 get contentsfile M 52 53 go down M
12. and by propagating the transition stop edit doc from the document to all parts Finally all state changes of a part which reflect a content change for that part invoke the transition start edit doc at the document if necessary This is the case for the transitions init doc import doc and erase doc at parts Exporting of homogeneous documents to systems other than document is also handled in a special way In general exporting is done by exporting all parts in some sequential order to the same system and the same address The Changes system and Changes address is propagated as well If all parts are simple documents this results in exporting exactly those parts which have changed 6 4 4 Combination with Version Management The types struct doc and homstruct doc may be combined with version doc If the parts are of type version doc themselves a certain coupling between document versions and versions of the parts emerges For a struct doc this is a very loose coupling for a homstruct doc however the state consistency conditions imply a tighter coupling every version interval of the document is fully 49 contained in a version interval of every part with an overlapping version interval This is guaranteed because every state change that starts or ends a version of a part either implies a similar state change of the document or requires that the document is in a state where no version exists However to do a correct version mana
13. described 5 1 1 Team Activities All types defined in the TACTS core specify activities which are performed by a single agent In collaborative environments however there is a need to specify activities performed by a team as a whole Typically these are structured activ ities and the parts are performed by separate single team members In this way every team member plays a certain role in the team activity The team activity like other activities may be represented by an object in the user space of each team member Currently shared objects are not supported in TACTS ELIOOS thus no single object can represent the team action inde pendently from a member It is planned to add this feature in future versions of TACTS On the other hand the member specific object representing the team activity should also be specific to the role the member plays in the activity Thus every member should have an own view of the activity by maintaining an own variant of the team activity Different views should allow different operations on the activity This can be achieved by defining a separate type for every role of the executing agent 39 active transitions long act restart act by single with partner request request initiator request addressee Figure 5 1 The Types for Requests 5 1 2 Virtual User Concept Types The features of a team activity which are common t
14. or resizing or deleting windows When GNU Emacs runs under the X Window System it supports mouse clicks and popup menus These are used in TACTS in several ways to provide an alternative interface One example is method activation by the mouse A menu is popped up displaying the list of methods applicable to the object depending on its type The method to be activated can then be selected with a simple mouse click 10 Chapter 3 Basic Mechanisms This chapter describes the basic mechanisms of TACTS They are implemented as ELIOOS types and can be used separately or in combination 3 1 Attributes In ELIOOS attributes are the single means to specify information for instances In this section we introduce several specific application kinds for attributes used in TACTS The corresponding types either define specific attributes or they define methods which can be used to manipulate attributes of a certain kind In the first case the type is is a user concept in the second case it is a designer concept which needs additional specialization see Section 2 1 2 3 1 1 User editable String Attributes It is often useful to associate one or more short text strings with an object Examples are a name for an agent object or a medium specification for an infor mation transmission object In ELIOOS all attribute values are strings Thus attributes may directly be used to hold strings associated with an object How ever mechanisms must be a
15. 2 2 The Subactivities for the Document Methods 6 3 Document Versions 1 0 ee 6 3 1 Definition of Document Versions 6 3 2 Operations for Document Versions 6 3 3 Named Versions 2 0 0 0 000 2 eee ee 6 4 Document Structure aoaaa aa ee 6 4 1 Simple Documents 202 0004 6 4 2 Structured Documents 0 0084 il 25 27 27 27 28 29 29 30 30 31 31 31 32 32 32 32 32 33 35 39 39 36 36 37 38 38 6 4 3 Homogeneously Structured Documents 48 6 4 4 Combination with Version Management 2 2 2 49 6 5 Document Content 0 0 020000 eee 50 6 5 1 Internal Documents oaoa aa 51 6 5 2 Filed Documents a aoaaa 0 20004 52 6 5 3 Filed Documents and Structure 52 6 5 4 Document Content Kinds aoaaa aa 53 6 6 Processable Documents aooaa aaa pee 53 6 6 1 One Step Processable Documents 55 6 6 2 History and Versions for Processable Documents 56 6 6 3 TeX Documents 2 2 nommen 56 7 Communication 59 7 1 Supporting Communication 2 222mm nn 59 7 1 1 Communication Environments and Addressing 59 7 1 2 The Transmission of Text Pieces with Headers 60 7 1 3 The Interface to the Transmission Medium 61 7 1 4 The Interface to the Transmitted Object 62 7 1 5 Communication and Document History 63 7 1 6 Communication and TEX Documents
16. Infinite sets are a useful means of describing periodic activities such as weekly two hour meetings The mechanism includes naming of time specifications and functions to gen erate time specifications Both are accessible to and can be configured by the user For example it is possible to define the name monday as the periodic set containing all intervals from 0 00 to 24 00 on mondays and to define a function named december which returns the interval of the month december for the given year note that the set of all december intervals is not periodic and thus can not be described by a single time specification The user interface for time specifications consists of a parser for user input and a converter for user output The converter displays time specifications in a read able standard format This is a list of single intervals or periodic sequences from one prototype A single interval is given by its start and end minute displayed as date day month year and time hour minute For a periodic sequence the prototype and the period are given There are several enhancements possible such as name display if a name is defined or displaying the date only once if it is common to both the starting and ending point This will be done in com ing versions Currently only the abbreviation of time points as single minute specifications has been implemented The parser allows a rich variety of input forms Aside from specifying an interval se
17. activity by adding a new time interval An activity which was restarted several times thus has as time specification the set of exactly those time intervals in which it was not in an unstarted or finished state For every unstarting transition the time specification is cut with the interval from the current minute to infinity This models undoing the activity by for getting about the existing time specification and initializing it anew i e to the interval it may take place from now on The type timed state is implemented as a specialization of start fin state and with time The time setting steps are added to the respective methods start finish unfinish and unstart Of course the types timed state state collection and timed collection may be combined resulting in a type which couples all three basic mechanisms 23 3 4 6 Executing a Transition upon Instance Creation The automaton of Figure 3 5 may be used to model the execution of activities Upon creation all these activities are in state planned and must explicitly be activated In many cases it is convenient to enter unplanned activities which should be activated or completed immediately after creation This is possible with the help of type immediate It specializes the generator method created by executing the method transit step after initializing the state This works for all objects using the state mechanism If there is only one transition leaving the initial state such
18. consistency conditions are based on the mechanism for starting and finishing objects as described in Section 3 4 3 They may be formulated as the single condition Whenever a collection is in an unstarted or finished state all mem bers which are of type start fin state must be in a state of the same sort For an object of type activity set this means that if it is in an unstarted state all subactivities must be in an unstarted state as well If it is in a finished state all subactivities must be in a finished state as well This condition clearly makes sense for the usual semantics of activities and subactivities The conditions are implemented by the type state collection which is a spe cialization of collection and start fin state and the type state member 22 which is a specialization of collection member and start fin state The type state collection enhances the methods unstart and finish by testing all mem bers for being in a state of the necessary sort If this is not the case the user is informed and the transition is not completed it remains begun The type state member enhances the methods start and unfinish by testing the col lection for being in a state where this kind of transition is allowed If it is not allowed again the user is informed and the transition is not begun This behavior implies that the user has to start an activity as a whole before he she may start any subactivity of the activity and the user has t
19. have only one description of this kind The type with descr is a user concept The user decides which objects have a description by adding the type with descr to the objects types either upon creation of the object or later during a specialization of the object 3 1 3 References An attribute may be used to hold a reference to another object This is im plemented by storing the object name see Section 2 1 1 in the attribute The type with ref defines three methods which support attributes with object ref erences The method set ref can be used to set or change an object reference The method deref tries to dereference a given reference attribute The method follow ref displays information about the object referenced by a given attribute using the mechanism introduced in Section 3 2 2 The type with ref is a designer concept It does not make sense to instan tiate it directly since it does not define an attribute 3 2 Collections The mechanism introduced in this section is used throughout TACTS to provide objects with a hierarchical structure The idea is to define a type for objects which represent collections of other objects Figure 3 1 depicts the part of the TACTS type hierarchy introduced in this section The boxed type free has already been introduced 3 2 1 Object Collections The type collection describes objects which represent a family of named sets of other objects which may be collections themselves The sets are
20. implemented 12 free collection collection member activity set collection and member Figure 3 1 The Types for Collections by using ELIOOS groups The members of a set are exactly the objects in the corresponding group This implies that an object may be a member of at most one set of at most one collection object The main attribute of a collection object is the list of set names defined for it together with the corresponding group numbers This approach allows a thematical grouping of subobjects by using different sets As an example an object representing a structured document with history protocol is implemented by a collection with two object sets the set of document parts and the set of activities performed on the whole document 3 2 2 Displaying and Member Lists for User Interaction The type collection also implements the central part of the TACTS user inter face It displays lists of set members in the object buffer Objects can be selected from this list by moving the cursor point to it They can then be used in a subsequent operation The method display subs is defined to display a list of members of one set associated with a collection object The method uses the method display for every single set member to display its information Thus the information listed for a member may depend on the member s type Figure 3 2 depicts the user interface It shows a situation with two windows each
21. management The 44 necessary additions are defined by the combination supplement type version edit doc which is automatically added to any combination of the types version doc and edit doc 6 3 2 Operations for Document Versions The type version doc defines the new method display versions The method simply shows the version list in a separate buffer The single main interface to access document versions is constructed using the export operation The method export doc is enhanced to take a reference to a version interval a time point as additional argument If a version interval is defined at that time point the corresponding content is exported instead of the current content In this case the arguments Changes system and Changes address of method export doc are ignored However it would be possible to define a specialization of type version doc which exports the changes between two versions in an appropriate way e g by using the UNIX diff command The version interface via the export operation is very flexible It makes con tent versions usable for any export system defined for the document In particu lar if the corresponding export systems are provided any version of the document may be previewed printed or processed in some other way For any document the version mechanism can be used in combination with the export system document see Section 6 1 1 It allows to copy any version of a document to another document
22. receive simple doc T 63 Ycharseq send binary doc T 60 63 Ycharseq send simple doc T 60 63 collection and member T 13 15 doc receive via mail T 62 63 doc receive via news T 62 doc send via mail T 60 62 63 doc send via news T 62 73 edit procl doc T 54 55 history edit doc T 41 43 44 homversion doc T 46 50 receive doc T 65 68 receive doc by mail T 65 68 receive doc by news T 68 Yoreceive doc with headers T 66 67 Yoreceive local doc T 65 Yoreply with newsgroup T 66 67 reply with subject T 66 67 send doc T 65 68 send doc by mail T 65 68 send doc by news T 68 Ysend doc with headers T 66 67 send local doc T 65 66 68 simple edit doc T 46 47 Ysimple filed doc T 51 52 54 simple filed tex source T 54 57 simple intern doc T 51 52 54 simple intern tex source T 54 57 Ysimple text doc T 51 53 struct filed doc T 51 53 57 struct intern doc T 51 struct rooted tex source T 54 57 trans local doc T 65 two agent reply T 33 34 version edit doc T 41 45 abort R 28 29 abort act T 28 aborted S 28 29 action transit M 21 24 42 44 49 activate R 20 22 28 29 37 38 66 active S 20 21 28 29 37 38 66 activity set T 13 15 19 22 24 28 29 47 add trans act M 25 addtime M 18 19 agent T 29 30 60 agent info M 29 60 agent set T 30
23. select one of them thus copying the agent reference from the superordinate object to the subordinate object If no agent is selected the method asks the user for the shortname of the agent The method then looks up the agent in all agent sets on the path from the current activity to the root object of the current base with the help of method search member see Section 3 2 3 The first agent found with the given shortname is used and a reference to it is stored using the inherited method set ref When an object with associated agents is displayed the agent is displayed by its shortname If no reference is stored in the attribute the string lt not given gt is displayed instead If the reference can not be resolved it is assumed that the agent object was deleted and the string lt deleted gt is displayed 4 3 The Executing Agent of an Activity The simplest form of activities supported by the system are activities executed by a single agent This may be the user of the system or any other person In the latter case the TACTS user only protocols the activity 4 3 1 Activities Executed by a Single Agent The type by single defines a new attribute By that stores an agent reference Semantically it should be the agent that executes the activity As usual the type by single may be combined with other types like basic activity and struct activity and specializations thereof The type init by is a specialization of type by single It
24. set should contain all agents which are involved in this activity only The root object of the object tree in a TACTS base always is of type agent set and the associated set contains all agents which are not local to a specific activity The method show agents of type agent set pops up a buffer with a list of the agent set members Using this buffer the user can create any number of agents for later use in activities Like other objects agents can be moved and deleted 4 2 3 Activities with Agents Agents may be associated with activities for several purposes Examples are the executing agent the initiating agent or agents that are involved in the activity in other ways Every kind of agent is associated with the activity by storing a reference to the agent object in a corresponding attribute Figure 4 3 depicts the types for activities with two kinds of agents defined in Sections 4 3 and 4 4 The type with agent is a specialization of type with ref It defines or enhances methods to manipulate agent references It does not define concrete 30 agents Thus it is not a user concept All methods take as argument the name of the attribute containing the reference The method set agent is used to set the reference for a given kind of agent If no reference is given there are two possibilities for setting the agent interactively First the method displays a menu of all agents defined at the collection the object is amember of The user may
25. sets the executing agent upon creation of the object using the method set agent The type inherit by further specializes type init by It does not ask inter actively but tries to use the executing agent of the containing collection 4 3 2 Activities Executed by the User A special form of activities with a single executing agent are those activities executed by the TACTS user himself The type by self describes activities of this kind It is a specialization of init by which automatically tries to set the By attribute to a reference to an agent with shortname self To use this type the corresponding agent object must exist TACTS auto matically creates an agent with shortname self in the agent set of the root 31 object in each base 4 4 The Partner Agent of an Activity Additionally to the executing agent TACTS supports the specification of a part ner agent No further assumption is made in the TACTS core about the way the partner is involved in the activity 4 4 1 Specifying an Activity Partner The partner specification is implemented by the type with partner which adds the agent reference attribute Partner The type init partner is a specialization of type with partner It sets the partner agent upon creation of the object using the method set agent The type inherit partner further specializes type init partner It does not ask interactively but tries to use the partner agent of the containing collection 4
26. specified target The export target is specified in two parts by giving a system and an address As an example the system may be printer and the address specifies the particular printer to use The cor responding method is export doc It has the parameters System Address Changes system and Changes address The last two parameters may be used to specify that only changes relative to the last export to that target shall be exported 41 Dually to exporting a document a document of type doc may be imported This covers all cases when the content of the document is taken from a source like receiving it via electronic mail or from a generating system The source is specified by system and address like the target of exporting The correspond ing method is import doc For abstract documents one export system and one import system is prede fined The export system document exports the contents to another object of type doc The target object is given as address of the export doc operation It works by using the import system export at the target object with the source object as address This import system may not be used directly it must rather be called by the export operation of another object Together both systems provide a content structure copying feature between objects of type doc Besides these two systems any string may be given as system and address for export doc and impor
27. state specific selection of transitions 3 4 3 Starting and Finishing Objects In many cases it is useful to have a notion of starting and finishing an ob ject This could be implemented by using an automaton with corresponding transitions However in TACTS a more general approach is taken Any state in an automaton may be marked unstarted or finished by setting its state sort As an example in Figure 3 5 state sorts are given in parentheses The state active does not have any specific sort This mechanism of state sorts allows more than one state to have these proper ties and more than one transition to be a starting or finishing transition An example are two states for successful and unsuccessful completion of an activity In both states the activity is finished 21 Based on the two state sorts unstarted and finished four kinds of transitions are defined A transition which leads from an unstarted state to a state of any other sort is a starting transition A transition which leads from any state that is not of sort finished to a finished state is a finishing transition In Figure 3 5 the transition activate is a starting transition and the transition complete is a finishing transition Any transition leading from state planned to state completed would be both starting and finishing Analogously an unfinishing transition leads from a finished state to a state of some other sort and an unstar
28. struct rooted doc is a specialization of struct doc that defines an additional attribute Documentroot It stores the object number of a document part This part is interpreted as document root The type only defines the method set documentroot to set the attribute The usage of the value must be defined by specializations of struct rooted doc For an example refer to Section 6 6 3 6 4 3 Homogeneously Structured Documents For structured documents it is often the case that an operation on the whole document can be implemented by applying the same or a similar operation to all document parts Structured documents of this kind are called homogeneously structured A typical example is a book which has chapters as parts An example for a non homogeneously structured document will be considered in Section 6 6 Homogeneously structured documents are defined by the type homstruct doc which is a specialization of struct doc All parts of a homstruct doc are automatically specialized to the type homstruct part Together both types implement the coupling between the whole document and its parts It is based on the principle that the content of the document consists of all part objects as well as of their contents The following consistency conditions for the state of the document are sup ported 48 1 the document is undefined iff no part exists 2 if the document is fixed all parts are fixed 3 if a part is in edit the document is in edit
29. to be relative to the document s directory if it is no absolute path name When a local filed doc is exported to system command the command is executed in the directory of the document and the relative pathname is inserted 6 5 4 Document Content Kinds The type text doc is used to specify a document for which the content is in plain text format i e coded as a sequence of characters in the host computer s code used for characters such as ASCII or EBCDIC The type is a specialization of type doc Two additional export systems are defined by type text doc screen and printer The combination supplement type simple text doc implements these systems for combinations of the types simple doc and text doc For the screen system the address argument is ignored and the content buffer is simply displayed in read only mode For the printer system the address must be the name of a printer The buffer content is printed as plain text with the help of the emacs line printer interface The type binary doc is used to specify a document for which the content is in some binary format This may be a text as well however it can not be read or printed directly It must be processed in some way to use it See Section 6 6 3 for an example 6 6 Processable Documents Often electronic documents stored in the computer are also processed in some way by the computer Processing a document produces another form of the content Usu
30. used must be specified Both systems use the same mechanism for this kind of information A set of headers is prepended to the content Each header starts with a keyword and has a string as value TACTS supports this kind of information by types for managing a header set There is one important difference between the two systems in respect of ad dressing Electronic mail typically is transmitted between two agents Both agents are identified by an email address of the form user host In the news system articles are not transmitted to a single agent Instead they are posted in 59 free simple doc charseq send binary doc doc 7 charseq send simple doc charseq hb send charseq send binary doc send via mail doc export with headers doc send via mail Figure 7 1 The Types for Sending Documents via Electronic Mail the form of a broadcast with no specific recipient given Upon receiving a news article however the posting agent may be determined by its email address which is included in the article Thus receiving electronic mail and news articles as well as sending electronic mail can be modeled by using the type two agent trans introduced in Section 4 5 2 Posting a news article only uses the types send info and by single TACTS supports electronic mail addressing in a special way The user does not specify the address directly Instead the user specifies an agent
31. ways However more support for automatic reception of mail and news articles will be provided in future TACTS versions For documents sending and receiving the content is integrated in a special way into the existing document operations Sending is done by exporting the content receiving is done by importing the content Thus it is possible to use all other features of these operations such as exporting changes or exporting older versions in combination with electronic transmission To enable the specification of a header set for export and the retrieving of the header set upon import the types doc export with headers and doc import with headers are used The former defines the additional argument Headers for the method export doc the latter allows the returning of the header set by the method import doc The combination supplement type doc send via mail is used for the com bination of the types doc and send via mail It is a specialization of type doc export with headers and defines the additional supported export sys tem email The destination agent is specified in the parameter Address of the method export doc The method maps the given agent to its email address see Section 7 1 1 prepares the corresponding header To and adds it to the header set The resulting header set is passed to the method send mail which is called to send out the document content Note the difference between headers and body in the case of docume
32. 3 Time Specifications The next mechanism is used to add a time specification to objects representing an activity It is used to describe the time when the activity is planned to take place if it is in the future or actually has taken place if it is in the past Since activities can be large and may have an internal structure of subactivities these time specifications must be flexible enough to allow arbitrary sets of time intervals Figure 3 3 depicts the part of the TACTS type hierarchy introduced in this section The boxed types have already been introduced 3 3 1 Interval Sets and Operations Time specifications are implemented as finite or infinite sets of time intervals This mechanism was developed in 9 Time intervals are specified on a per minute basis Every interval has a start minute and an end minute Special cases are open time intervals and time points Open time intervals either have a start infinitely in the past or an end infinitely in the future The interval with the start infinitely in the past and the end infinitely in the future is provided too Time points are intervals for which start and end coincide 16 Time intervals are collected in sets of non adjacent and non overlapping inter vals A set may contain an infinite number of intervals if they can be specified by a periodic repetition of a prototype interval A set may contain several infinite sequences generated from various prototypes of different periods
33. 4 2 Using the Partner Specification The partner specification may be used by optionally inheriting it to subactivities In general this is done by defining a specialization for all applicable types those which specify an agent which may be the partner using the partner specification of the containing collection as default for the agent An example is to use the partner of the containing collection as executing agent for an activity This is implemented by the type by partner It is a specialization of type init by that works analogous to the type inherit by Other specializations of activities may use the partner agent in other ways Currently it is used by information transmission activities to specify the source or destination agent respectively see Section 4 5 and Chapter 7 4 5 Basic Communication The last part of the TACTS core describes special activities which incorporate communication Only rather general types of communication activities are de fined in the core Figure 4 4 depicts the corresponding part of the TACTS type hierarchy For more specific communication mechanisms see Chapter 7 4 5 1 Information Transmission The basic communication activity is the transmission of information via a certain communication medium The type trans info defines the user editable string 32 free by single trans info with partner with ref receive info send info two agent trans reply trans two agent r
34. M 61 62 send mail T 68 69 send news M 61 send news T 69 send via mail T 60 63 68 send via news T 61 64 68 set agent M 31 32 set agent from headers M 67 set attribute M 11 12 set documentroot M 48 set header M 66 set ref M 12 31 67 setold M 50 setold R 50 show agents M 30 show doc parts M 47 show doc parts T 48 simple act T 27 28 37 65 simple doc T 46 48 51 54 57 60 63 64 start M 22 23 start edit doc M 42 47 48 55 start edit doc R 43 44 49 start edit doc T 49 start fin state T 19 22 25 27 28 41 42 State A 20 state collection T 19 22 23 28 29 stop edit doc M 42 47 55 stop edit doc R 43 44 49 store doc M 46 51 52 struct activity T 28 29 31 struct doc T 46 49 51 52 54 55 struct rooted doc T 46 48 54 57 subtracttime M 18 19 tex doc T 54 56 58 tex dvi T 54 56 57 64 tex source T 54 56 57 64 text doc T 51 53 54 57 63 Time A 18 timed collection T 16 18 19 22 23 28 29 timed state T 19 23 28 69 trans by mail T 65 67 69 trans by news T 68 69 trans doc T 65 66 69 trans info T 32 33 65 68 transit run M 21 24 25 42 transit step M 21 24 25 42 49 two agent trans T 33 34 37 60 63 66 69 typeB T 8 typeC T 8 typeD T 8 undefined S 42 44 49 52 55 66 undo
35. R 28 29 undo act T 28 unfinish M 22 23 unstart M 22 23 version doc T 41 44 46 49 51 Versionhistory A 44 Versionnames A 45 with descr T 12 28 33 44 with doc T 64 65 with headers T 63 66 68 with local doc T 65 66 with newsgroup header T 66 69 with own doc T 69 with partner T 30 32 33 36 with state T 19 22 24 42 with subject header T 66 67 69 with time T 16 18 19 23 76
36. Several groups together form a base Every base may be loaded separately into the system All bases of one user form together a user space Each user has only access to the objects of his her own user space Thus the objects are local to the user Every object has a unique name which is fixed during the object s lifetime and is not reused after the object s deletion The object name may be used to access the attribute list associated with the object as long as the object exists Thus the name can be used for referencing an object from other objects Every object is created in a certain group and base of a user space The user can delete it or move it into other groups or bases in the same user space 2 1 2 The Type Hierarchy The common properties of a class of objects are defined and implemented by a type A type is simply a collection of items which describe object properties in some way One example for these items are methods There are two ways of specifying a type by explicitly defining type con stituents or by combining other types Normally these mechanisms are mixed when a type is defined One or more existing types are combined and extended by explicit definitions of constituents When types with common constituents are combined these constituents are combined in a special way resulting in true multiple inheritance Types combined in one step have no special order which effects the combina tion of constituents The resulting typ
37. WM The activity support system TACTS Gunnar Teege TUM I9306 April 1993 Contents 1 Introduction 2 The ELIOOS Object Oriented System 3 2 1 2 2 Overview aaa a 2 1 1 The Object Base aoaaa 2 02 2 2020048 2 1 2 The Type Hierarchy 2 2222 Como nen 2 1 3 Methods 22 22 2 on nn The Implementation 22 2 2 Coon nen 2 2 1 The Implementation Environment 2 2 2 The User Interface aoaaa 202 0048 Basic Mechanisms 3 1 3 2 3 3 3 4 Attributes 2 ee 3 1 1 User editable String Attributes 0 00 3 1 2 Descriptions oo Co onen 3 1 3 References oaoa aaa Collections 22 2 oo non 3 2 1 Object Collections 2 2 2 2 nn 3 2 2 Displaying and Member Lists for User Interaction 3 2 3 Other Operations on Collections 2 222 22 3 2 4 Activity sets oo oo Time Specifications 2 ee 3 3 1 Interval Sets and Operations 3 3 2 Operations on Timed Objects 2 222222 3 3 3 Combining Time Specification and Collections State Management 2 2 0 ee ee 3 4 1 Automata as Type Constituents 3 4 2 Operations on Objects with State 2 2 222 22 3 4 3 Starting and Finishing Objects 00 3 4 4 Combining State and Collections 2 2 2 2 0 3 4 5 Combining State and Time Specification 3 4 6 Executing a Transition upon Instance Creation 3 4 7 Refined Transitions 2 2 2 2 nn
38. a collection It defines an operation which queries the collection and the set name the object is a member of To ensure that all collection mem bers are of this type every object is automatically specialized to this type if necessary upon addition to a collection s set The collection objects are used to impose a tree structure upon the objects in a base There are two simple operations for navigation in this tree The method go down of type collection switches to a buffer containing the list of a set defined for the selected object provided the selected object is itself a collection The method go up of type collection member switches to a buffer containing a list of a set defined for the collection object the current object is a member of provided the current object is a member of some collection s set Finally the type collection defines the method search member It takes as arguments a set name and a predicate in the form of a lisp function It tests all members of the named set and returns the first one which matches the predicate The combination supplement type collection and member is a specialization of the types collection and collection member It describes collection objects which are themselves a member of another collection The type enhances the method search member by optionally invoking the method at the superordinate collection if no member has been found locally This implements a search which proceeds upwards unt
39. a set of operations applicable to abstract documents in stances of type doc and thus to any specialized form of documents The type edit doc is a specialization of type doc and defines additional operations The operations are described together with their intended meaning in this section Each of them is defined by a method in the corresponding type A document of type doc may be initialized Initializing a document is different from creating it because initialization applies to the content and possibly the structure of the document Thus an existing document may be initialized more than once The corresponding method is init doc Analogously a document of type doc may be erased This only applies to the content or structure and thus differs from deleting the document instance However every document is automatically erased immediately before it is deleted The corresponding method is erase doc A document of type doc may be fixed For a fixed document the content may not be changed any more Thus initializing erasing or editing a fixed document is no longer allowed The corresponding method is fix doc A document of type doc may be exported to some target This is a very general operation which covers all kinds of document usage like previewing print ing processing or sending out It is possible to export the whole document or to export only the changes made to its contents structure since the last export to the same target or some
40. a special ization of the type refined transitions The user writes his her types as spe cializations of active transitions Optionally the type start fin state may be added and the types introduced in section 4 1 1 may be added to specify a part of the automaton The user may also define specializations of his her own types In a specializa tion it is possible to extend the automaton by adding states and or transitions to specify additional transition activities for transitions or to add types or pa rameter bindings to inherited transition activities In the last case the transition activity s name is used to identify the transition activity which has to be changed 25 On the other hand the type of a transition activity may be a specialization of type active transition too It may even be identical to the main type This results in hierarchical automata of depth greater than two The type active transitions provides a powerful mechanism to specify hi erarchical execution plans with a static scheme However the user may always leave the scheme and create additional subactivities manually thus unexpected cases may be handled easily For specifying the execution plan the user has to write type definitions in a lisp like syntax This will be improved in future versions of TACTS by providing a specific language for defining execution plans 26 Chapter 4 The Core of TACTS This chapter describes the core of the TACTS system It d
41. ally the processed form differs from the source in the operations which can be applied to it An example for document processing is the processing by text processing systems like TFX or troff Another example is the processing of program sources by a compiler Figure 6 5 depicts the types defined in this section 53 struct doc procl doc edit doc tex doc Redit procl doc text doc struct rooted doc simple intern dot tex source simple filed doc E struct rooted tex source simple intern tex source simple filed tex source simple doc binary doc filed doc tex dvi Figure 6 5 The Types for Processable Documents 54 6 6 1 One Step Processable Documents In the current version TACTS supports processing of documents in a single step This is defined by the type procl doc The combination supplement type edit proci doc is used for the combination of type procl doc with type edit doc Note that document processing can also be achieved by exporting it e g by exporting a simple document to the system pipe or by exporting a filed document to the system command However in this case the result of the processing is not automatically accessible to TACTS and can not directly be processed further using TACTS The type procl doc instead represents the result of the processing step by a TACTS document as w
42. and addresses to be used must be specified by the respective specializations of procl doc If the processed part was not in state undefined it is erased before importing the process result Exporting a procl doc is implemented as follows If the last change of the source happened after the last change of the processed part the method process doc is called Then the export operation is simply propagated to the processed part The user is not restricted to the operations defined in this way Like for any struct doc he she can also work directly on the source or the processed part In particular it is still possible to export the unprocessed source by directly 59 export tex doc export a N tex source er 5 S tex dvi u X aw i export z pe export import process Figure 6 6 Instances Comprising a TEX Document exporting the source part of the document 6 6 2 History and Versions for Processable Documents When a procl doc is processed or exported the processed part usually changes However this does not mean a real change of the document and thus no state transitions for the document should be performed like it is done for a homoge neously structured document when a part changes On the other hand changes in the source should be registered as changes of the document as a whole To achieve this the type homstruct part is automatically added to the source part object Additionally
43. as in Figure 3 5 then it is executed If there are several transitions the user is asked to select a transition as usual in the method transit step 3 4 7 Refined Transitions The approach of Section 3 4 2 is further extended by allowing hierarchically struc tured dynamic automata The key idea to do this is the explicit modeling of transitions by one or more activity objects which may have their own automa ton These activities are subactivities of the main activity thus we chose as starting point a combination of types activity set and with state The behav ior of the overall activity is specified by the automaton of the main activity object together with all automata of the subactivity objects We call transitions with associated subactivities refined transitions and the subactivities transition activities Every refined transition may have one or more transition activities A transition is completed when all its transition activities are finished Refined transitions remain begun until the last transition activity is finished Then it is automatically completed If all transition activities are reset to an unstarted state the transition is automatically reset to its source state The activities associated with a transition may be executed in any order including parallel At any time it is possible to switch from one to another Furthermore activities may be created and added to a transition even when the transition is begun This allows t
44. ative activ ities in a uniform way Both may be supported by structuring protocoling and execution This does not mean that higher level aspects of collaborative work can not be represented in TACTS Medina Mora distinguishes in 7 the level of information processes and the level of business processes where the former describes the way information is passed and the latter describes the reason expectations and dependencies of information passing In TACTS both levels may be represented in a common framework the business level being implemented on top of the information level TACTS is an evolving system Some aspects are already included in the current version Among them are office procedures group interaction document development time planning and electronic communication All of them still can be strongly improved and extended and additional aspects can be added One important point is the extension of the system by the end user Kuutti argues in 6 that a system for activity support should not only support performing the activity instances Instead it should support the design of tools rules and schemes which help in performing activity instances As an example the system should support the definition and manipulation of procedure execution plans not only the execution of a number of fixed plans To achieve the required flexibility and extendibility TACTS uses an object oriented approach Multiple inheritance is used massively
45. be executed once and thus only one question transmission instance can be created Every answer is associated to the transition complete in the state active Since the request is of type restart act this transition can be executed more than once Upon every execution a new answer subactivity instance is created and completed The type request could be specialized in many ways It is possible to spe cialize or change the types of the subactivities It is possible to associate more than one subactivity with every transition It is also possible to enhance the automaton for the request and allow for more than one question 5 2 Fixing a Role in Team Actions To use the virtual type request it is necessary to fix the role of the executing agent in the request There are two possible roles the initiator and the addressee 37 5 2 1 Role Specific Types Every role of a virtual type is specified by a specialization of the type Usually the specialization presets certain attributes specializes the type of some subactivities and defines additional operations which may be executed by the agent playing this role In the following this is demonstrated for the two roles of the type request 5 2 2 The Role Specific Types for Requests In a request the difference between the two roles only lies in the direction of the information transmission subactivities When the executing agent is the initiator the question is sent and the answers are received W
46. by reentering the source state The type with state defines the three methods begin transit complete transit and reset transit for the single parts of transition execution Addi tionally the methods transit step and transit run implement the execution of transitions as a whole The transit step tries to execute one transition by beginning and completing it If there is already a begun transition it is com pleted If no transition is specified and there is more than one possible transition in the current state the user is asked to select one of the possibilities The method transit run performs transitions until the user stops it or it reaches a state where no transition leads away The user is asked to select a transition or stop the execution of transit run before each transition beginning Both methods transit step and transit run invoke another method action transit immediately after beginning a transition This method is defined by type with state however it does nothing It may be used in specializations of type with state to add actions to be performed by TACTS during the transition execution The type with state only implements the state change during tran sitions Thus by simply enriching the automaton of type with state and using the methods transit step and transit run as they are it is possible to construct a wide variety of concrete execution plans together with an interface which keeps track of the current state and allows the
47. case is defined by the type struct filed doc which is a combination supplement type used for the combination of the types filed doc and struct doc The second case is defined by the type simple filed doc which is a combination supplement used for the types filed doc and simple doc The type simple filed doc interprets the file name as the name of a plain file which stores the content of the document Like for simple intern doc the methods store doc and load doc are implemented thus offering the full content manipulation features defined for abstract documents The methods are implemented by directly using the emacs operations for loading and storing a file The type struct filed doc instead interprets the file name as the name of a directory This directory is used in a number of ways as default place to work with the document Additionally the type filed doc is added to all parts The specialization local filed doc of filed doc can be used for parts of a 92 struct filed doc for which the file resides in the directory of the structured document The type local filed doc only stores the path name relative to the directory of the containing document It defines the additional parameter Ab solute for the method get contentsfile If this is set to TRUE the absolute pathname of the file is returned otherwise get contentsfile returns the relative pathname Additionally local filed doc treats the address of an import from system file
48. casts or posting to information boards the specialization type two agent trans de scribes the activity of one agent of transmitting information between him herself and a second agent The type is a combination of the types trans info by single and with partner Here the attribute Partner is used to store the second agent involved in the transmission The type two agent trans may be combined with the types by self inherit 33 by or by partner to specify the executing agent it may be combined with the type inherit partner to specify the partner agent and it may be combined with the types send info or receive info to specify the direction of the transmission If the type two agent trans is combined with the type reply trans the combination supplement type two agent reply is added It automatically sets the agents of the reply from the agents of the other transmission whenever the attribute Reply of is set to a reference to another transmission 34 Chapter 5 Requests This chapter describes the types for requests They should be useful on their own however mainly they are an example of complex activities which are executed by a team of more than one agents Figure 5 1 depicts the corresponding part of the TACTS type hierarchy 5 1 Classes for Team Activities This section describes the mechanism for defining virtual user concept types which specify activities for a whole team As a special case the virtual type request is
49. ciple of applying fine grain inheritance for the construction of a flexible and extendible toolkit for activity support Third it should give examples for the realization and integration of several different mechanisms in the object oriented framework Finally it should be the starting point for the evolution and extension of the TACTS system We would like to thank Johann Schlichter and Uwe M Borghoff for valuable contributions to the report Many thanks are also due to Franz Vojik Friedl Bunke Armin Liebl and Christof A Neumann for many stimulating discussions regarding the TACTS design Chapter 2 The ELIOOS Object Oriented System TACTS is implemented on top of ELIOOS the Emacs Lisp Object Oriented System ELIOOS was specially developed for TACTS however it can support other systems as well 2 1 Overview In this section we give an overview of those features of ELIOOS which are crucial for the functionality of TACTS This is not meant to be a full documentation of ELIOOS it should only give a feeling 2 1 1 The Object Base ELIOOS maintains a set of objects called the object base The structure of a single object is that of an attribute value list Every list element consists of an attribute name and an arbitrary string as attribute value The object set is structured on three levels On the lowest level objects form groups A group may contain an arbitrary number of objects Each object must belong to exactly one group
50. containing a list of members The upper window displays the subactivities of the root object in the base The lower window displays the subactivities of the activity example4 which is a member of the list in the upper window Every object is displayed in a block of consecutive lines An object may be selected from the list by moving point to it or by clicking the mouse on it There are several operations implemented by methods of type collection which use the selected object in some way One example is the method delete sub which deletes the selected object 13 59 examplei lt completed gt with descr basic activity by self init partner Partner uwe Uwe M Borghoff By self Gunnar Teege gt 11 3 1993 14 01 This is a basic activity done by the user together with a partner 60 exanple2 lt active gt with descr long act basic activity send info Partner franz Franz Vo jik gt By self Gunnar Teege gt Medium telephone 11 3 1993 15 23 This activity describes the transmission of some information via telephone 61 example3 lt planned gt struct activity by self gt By self Gunnar Teege gt 12 3 1993 10 00 62 example4 lt completed gt with descr request initiator init partner by self Partner uwe Uwe M Borghoff gt By self Gunnar Teege gt Ansuers 2 11 3 1993 14 34 11 3 1993 14 56 This is a request initiated by the user 63 example5 lt existent gt intern doc text doc simple doc Last chan
51. ctivities in this way 6 The main parts of the context are the object which is manipu lated the active subject which performs the activity and a community which is involved Accordingly TACTS supports the representation of other units aside from activities Examples are documents which are objects manipulated during activities or agents which represent active or passive subjects However TACTS is not restricted to a fixed set of units Any kind of unit with any semantics can be introduced and used in the system The approach of TACTS has some interesting consequences Since the basic units model activities of a single user and are local to that user it is possible for some members of a group to use TACTS while others don t Systems using a centralized approach to group work where the basic unit is a group activity do not allow this flexibility With TACTS every user may decide whether to use TACTS and when used for which projects With centralized systems all group members must use the system if the group work is supported by the system Of course in TACTS additional support can be provided if all members of a group use the system Another consequence is that TACTS supports activities which do not involve collaborative work as well Many collaborative activities have subordinate non collaborative activities such as writing a short report as part of a larger project involving other people TACTS treats collaborative and non collabor
52. dded to display the string and to allow interactive editing These mechanisms are defined in type free It is the root type of the TACTS type hierarchy Since it is a supertype of every other TACTS type every TACTS type may define user editable attributes The type free introduces two new methods display and set attribute The method display is used to display information about the object Whenever a new string attribute is defined in a type the method display must be enhanced a new method part must be defined to display the new attribute s value if this is required The method set attribute may be activated by the user to change the value of a given string attribute interactively 11 The type free introduces one string attribute the shortname It can be used to provide a short characterization about the object In some cases it is used for user input of object references However in general it need not be unique and it is not required to be set for all objects 3 1 2 Descriptions A special case of a string associated with an object is a description of the object The type with descr defines a multi line description using the attribute Descr The difference between this attribute and normal string attributes as described in Section 3 1 1 is the fact that the special method edit descr may be used to change a description This methods supplies better support for editing a multi line string than set attribute However an object may
53. ds the method B again Additionally C may not have parts in common with A Method combination is the main mechanism for implementing multiple inher itance in ELIOOS The combination of n methods contains all parts belonging to the single methods However parts which are inherited along several different paths in the type hierarchy are only contained once Attributes are introduced by parts of the method created and are thus inherited in the same way The following example should illustrate multiple inheritance by method combination in ELIOOS We use an informal syntax for defining types methods and method parts The meaning should be apparent typeA created partAl create attribute X typeB specialization of typeA created partBl create attribute Y partB2 after partAl set attribute X to VALI typeC specialization of typeA created partCl before partAl create attribute Y partC2 create attribute Z typeD combination of typeB and typeC One possible form of the method created of type typeD is the following partCl partAl partBl partC2 partB2 Note that partAl appears only once although it is inherited via typeB and typeC The execution of this method creates the attributes Y X and Z and sets X to VALI The creation of Y is done twice because the corresponding steps are inherited from different types In this case the second creation is ignored Thus ELIOOS implements attributes with the same name inherited from diff
54. e however is more special than any of the types used in the combination This defines a partial ordering on all types and results in the usual class hierarchy Additionally there are mechanisms for explicitly specifying automatic special ization and incompatibility Automatic specialization automatically adds some specified types whenever a certain set of types is combined For every set of types additional types may be specified for automatic specialization The typical application is to add certain properties to handle the combination of properties of two types Any set of types may be declared incompatible Incompatible types may not be combined The incompatibility applies only to the set as a whole True subsets may be combined as long as there is no explicit incompatibility declaration for the subset itself Note that types are never incompatible due to their definition Any two types may be combined if they are not explicitly declared incompatible Every object in the object base belongs to a type Upon creation of an object the user may select types from a menu of type names The selected types are dynamically combined and the result is used as type for the object The type of an existing object can be specialized at any time by combining it with additional types However it is not possible to generalize it by removing types In the menus dependencies between types are made visible to the user in the following ways After every selec
55. e user may select among all unfinished transition activities In the method transit run the user may additionally stop the execution Additionally the type refined transitions defines the new method add trans act It may be used to explicitly associate an existing subactivity with a transition 3 4 8 Programming of Execution Plans with Refined Tran sitions TACTS provides a simple mechanism for the user to specify automata with refined transitions The user may write type definitions which specify the automaton and the transition activities The automaton is given by introducing the states and the transitions with their source and target states For each transition a fixed number of transition activities may be specified Each transition activity is specified by a name a type list and a list of parameter bindings for the method created The name is used as a default for the shortname of the instance and to identify the transition activity in type specializations The instances of a type defined in this way behave as follows During the begin of a transition an instance of every transition activity is created After completing the transition the transition activities are no longer associated with the transition Thus if a transition may be executed more than once because it lies on a cycle in the automaton every execution uses its own set of transition activity instances This behavior is defined by the type active transitions which is
56. efines several basic types of activities Only history recording is provided for these activities in the core other support for the execution of the activities is added in extensions Currently the core part is rather simple it only supports activities which involve one or two users The extension of the core will be an important task in future versions of TACTS 4 1 Activities The most important kind of objects used in the TACTS system are activities The TACTS core defines types for basic activities and activities with subactivities The Figure 4 1 depicts the corresponding part of the type hierarchy As usual boxed types were introduced in earlier sections 4 1 1 The Basic Automata The activities defined in the TACTS core are characterized by their state automa ton The current version of TACTS provides some simple automata that apply to a broad range of activities All of them are extensions of a basic two state au tomaton defined by the type simple act and all of them use the starting finishing mechanism introduced in Section 3 4 3 Just the automaton itself is extended the methods are left unchanged For every feature a separate user concept type is defined They may all be combined in arbitrary ways The type simple act is a specialization of type start fin state The automa ton consists of one unstarted state planned one finished state completed and one transition complete from state planned to state completed The simple act a
57. ell In general a procl doc has exactly two parts the source which is a document and the result of the processing step which is a document as well but may have types different from those of the source This implies that a procl doc is a non homogeneously structured document and the type procl doc is defined as a specialization of type struct doc In a similar way it would be possible to support documents which are processed in several different steps The one step case was chosen for simplicity and multi step extensions will be provided in future TACTS versions Upon initialization of a procl doc the number of parts is already known and the parts are immediately created For both parts the type doc is used Specializations of type proc1 doc which know more about the kind of the source or the processed part can add any types which are required in their case Remember that erasing a struct doc deletes all its parts This behavior is inherited by procl1 doc as well We define the processing step to be the only way of producing the processed part Thus the methods init doc import doc start edit doc and stop edit doc are implemented for the document by propagating them to the source part Additionally the type proc1 doc defines the new method process doc which performs the processing step itself It is implemented by first exporting the source to some export system and afterwards importing the processed part from some import system The systems
58. eply Figure 4 4 Communication Activities attribute Medium and describes activities of this kind The transmitted infor mation itself is not supported by the type For simple cases it may be described using the Descr attribute of with descr The medium is only used for documentation purpose thus it may be any string like telephone personal talk or letter However in specializations described later some values of the attribute Medium will be interpreted by the system There are two specialization types send info and receive info of the com bination of the types trans info and by single They describe the transmission activity from the view of the executing agent Thus the combination of send info with by self describes the activity of the user of sending some information out whereas the combination of receive info and by self describes the activity of the user of receiving some information Another simple specialization of type trans info is the type reply trans which describes transmissions in reply to other transmissions To specify the other transmission type reply trans additionally inherits from type with ref and introduces the attribute Reply of to store a reference to the other transmission 4 5 2 Communication with an Activity Partner Frequently information is transmitted between two agents While the type trans info may also be used to describe information transmissions like broad
59. er management as part of transmission activities are intro duced They are depicted in Figure 7 3 The type with headers defines the attribute Headers which stores a header set Additionally it defines the method set header for interactive entering or changing a header 66 There are two combination supplement types for the combination of with headers with the types send doc and receive doc respectively The type send doc with headers passes the headers to the method export doc at the document during the transition complete The type receive doc with headers sets the headers to the header set returned by the method import doc during transition complete The type with headers can be used as basis for several kinds of automatic header manipulation To demonstrate this the current version of TACTS defines three such kinds managing a subject header managing a newsgroup header and determining the partner agent from the headers The type with subject header automatically creates the header Subject which is commonly used for electronic mail and news articles When this type is combined with type reply trans the combination supplement type M reply with subject enhances the method set ref in the following way Whenever the reference Reply of is set the subject of the referenced activity is retrieved and the subject of the reply activity is set to the concatenation of Re and this subject This is the standard way of setting the sub
60. erent types by a single common attribute of this name 2 2 The Implementation Now we present some aspects of the ELIOOS implementation These may be of interest to the user since they involve the basic layers of the user interface 2 2 1 The Implementation Environment For several reasons we chose GNU Emacs as the implementation environment First an Emacs lisp program is highly portable Even the compiled form can be transferred directly to any machine operating GNU Emacs Second Emacs lisp allows direct access to the multi buffer multi window user interface of Emacs to text editing facilities to file handling facilities and to subsystems for sending and receiving electronic mail or for using the USENET news system Furthermore there is an interface to the operating system which allows the use of all system commands Thus it is possible to access printers compilers or text processing systems Third emacs provides a comfortable programming and documenting environment which includes a symbolic debugger The ELIOOS system is simply a set of emacs lisp functions and variables It mainly implements the object base management the type hierarchy management and a basic user interface Currently every base in a user space is stored in a separate text file using a special format There are functions for loading and parsing these files The user does not work directly with base files The type hierarchy is defined in lisp program files using a s
61. erval set which contains all time points not described by the original set Examples are the inversions of monday all days except monday of this day not today or of workdays holidays Subtracting an interval set B from an interval set A can be done by cutting A with the inversion of B In this way specifications like next week except wednesday or holidays except easter can be constructed All of these operations are fully implemented and may be arbitrarily com bined The operations include a canonization of the results The canonization e g eliminates unnecessary intervals and unites overlapping or adjacent inter vals This simplification is necessary for easy readability of the output produced by the converter 3 3 2 Operations on Timed Objects The type with time describes objects with an attribute Time which may have a time specification as value The type defines three methods namely cuttime addtime and subtracttime which apply the three binary operations to the attribute value The second argument of the operation is read in interactively by the parser when the method is activated by the user or may be given as method argument when the method is called from inside another method The type only handles the storing and manipulating of the time attribute It does not restrict its semantics to the intended use of time when the activity happens The type may be used for objec
62. ess to process the body parts It returns the header set as result 7 1 3 The Interface to the Transmission Medium A type that implements a specific transmission medium defines methods for send ing or receiving respectively The method for sending first invokes the method charseq prepare or charseq hb prepare to prepare the content for sending Then it sends out the content of the returned buffers in a system specific way The method for receiving first receives one or more parts in a system specific way and puts them into buffers Then it invokes the method charseq process or charseq hb process with the list of these buffers Accordingly the types send via mail receive via mail send via news and receive via news are defined for sending and receiving electronic mail and news They define the methods send mail receive mail send news and receive news respectively and implement them in the way described above The methods for sending take as single argument a header list which is passed to method charseq hb prepare The methods for receiving take no argument 61 They return the header list extracted by method charseq hb process Note that before a mail or news can be received by TACTS the user has to select it using the corresponding GNU emacs subsystem that provides an interface to the communication system In this way the user can still decide which mails or articles should be processed by TACTS and which should be processed in other
63. eviously in this case there must be a single version interval of the part which contains the whole document version interval Now for every part which has a corresponding defined version this version is exported to the same system and address 6 5 Document Content All features for documents described in the previous sections can only be used for structuring and protocoling To offer real support the document content itself must be stored by the system The current version of TACTS supports two variants of content storing for documents inside the TACTS system itself or in the file system Additionally there are two types describing the kind of the content The two kinds are text and binary content The kind determines what may be done with the content Figure 6 3 depicts the types defined in this section 50 doc struct doc intern doc filed doc simple doc struct intern doc struct filed doc simple intern doc simple filed doc text doc binary doc local filed doc simple text doc Figure 6 4 The Types for the Content of Documents 6 5 1 Internal Documents An internal document is a document for which TACTS itself stores the content Internal documents are defined by the type intern doc which is a specialization of doc Depending on the structure of the document there are two variants of internally stored documents For simple documen
64. ews Activities of information transmission by electronic mail are described by the type trans by mail It is a specialization of the types two agent trans and 67 with headers Upon creation of an instance it sets the attribute Medium to email There are the two combination supplement types send doc by mail and receive doc by mail for combining the type trans by mail with the types send doc and receive doc respectively If necessary both types automat ically add the type send via mail or receive via mail to the referenced docu ment during the transition complete to make the mail transmission mechanism available for the document Additionally the type send doc by mail passes the partner agent in the parameter Address to the method export doc at the document The type receive doc by mail is a specialization of type receive doc with partner It uses a special header parsing function that tries to extract the email address and the name from the header From Thus every instance of the type automatically searches or creates the partner agent after receiving a mail Analogously activities of information transmission using the news system are described by the type trans by news It is a specialization of the types with newsgroup header trans info and by single The combination supplement types send doc by news and receive doc by news automatically add the type send via news or receive via news to the referenced document dur
65. exibility extendibility and integration is also emphasized by Kreifelts in his report about the experiences with the Domino system 5 Among other deficiencies it was found that the exception handling facilities were not flexible enough mechanisms for the communication of informal information were missing and there was a lack of integration of other tools like electronic mail or spreadsheets As a general design principle TACTS uses activities of a single system user as central basic units This approach is of a finer grain than that of most other systems which use group activities 7 or tasks with contexts 2 as basic building blocks The TACTS approach enables the modeling of all these complex units by constructing them starting with the basic units The TACTS model includes three basic types of activity support Structuring Managing a structure of all activities of the user and of relations between them Protocol Protocoling the activities of the user and storing e g the time and outcome of their execution Execution Executing the activities If possible the system executes parts or all of the activity itself or it activates corresponding tools The reasons for calling TACTS an activity support system are the activity being a basic unit together with the three basic support types To fully define and understand an activity at least a minimal context is re quired The philosophical framework of Activity Theory describes a
66. ge 11 3 1993 15 14 ZA TACTS root subacts 5 51pm EL IOOS Ob j 1 question lt completed gt basic activity send info two agent trans inher it by Partner uwe Uwe M Borghoff By self Gunnar Teege gt Medium fax 11 3 1993 14 36 2 answer1 lt completed gt basic activity receive info two agent trans inher it Partner uwe Uwe M Borghoff By self Gunnar Teege gt Medium telephone 11 3 1993 14 45 3 answer lt completed gt basic activity receive info two agent trans inher it Partner uwe Uwe M Borghoff gt By self Gunnar Teege gt Medium fax 11 3 1993 14 56 le4 subacts Figure 3 2 The TACTS User Interface 14 3 2 3 Other Operations on Collections There are some primitive operations for accessing collection members It is pos sible to add a new named empty set to a collection by specifying the set s name It is possible to query the list of set names defined for a collection and given the name of a defined set to query the list of objects in that set It is possible to create a new object and immediately add it to a defined set It is possible to delete the selected object the object ceases to exist or to specialize its type It is also possible to move an object from one set to another set within the same or another collection Finally it is possible to invoke a method for the selected object On the other hand the type collection member describes all objects that are a member of
67. gement for type homstruct doc parts may no longer be deleted since they belong to the document content as well and thus information about an older content version would be lost Correct version management for this kind of documents is implemented by the combination sup plement type homversion doc It specializes all document parts by adding the type homversion part This is a specialization of homstruct part which adds a new state old to the automaton of doc together with transitions se told from any of the other three states into the old state and the corresponding method setold which is executed during these transitions Whenever the part of a document of type homversion doc should be deleted its state is set to old instead This allows it to be still accessed when an old version is required This behavior is implemented by changing the method delete sub of type homversion doc In the case that the part is itself a version doc the current version must be ended upon a transition setold because the part can not have a defined version after being deleted This is done by enhancing the method setold of type homversion part accordingly Finally the exporting of old versions of the document to systems other than document is partly implemented by type homversion doc If a document version is specified for the method export first all parts are checked if they have a defined version overlapping with the document version As mentioned pr
68. he use of transitions with a previously unknown number of concurrent subactivities To facilitate such refined transitions it is necessary to determine when an associated activity is finished Here the mechanism described in Section 3 4 3 is used again Thus every transition activity must be of type start fin state The type transition activity defines the behavior of transition activities It is added automatically to every object used as a transition activity The type which implements refined transitions is called refined transitions As described above it is a specialization of with state and activity set The methods transit step and transit run are enhanced as follows Immediately af ter calling the method action transit they try to execute one or more transitions 24 for a transition activity The method transit step calls itself recursively thus only one transition is executed at a transition activity The method transit run also calls itself recursively thus transitions for transition activities are performed until the user stops it or there are no more transitions applicable Then the method offers other transition activities or if all transition activities are fin ished it completes the main transition and offers to begin the next one In both cases first a transition activity must be selected If there is only one unfinished transition activity the method transit step selects it without asking the user In all other cases th
69. hen the executing agent is the addressee the question is received and the answers are sent The initiator role of type request is specified by the type request initiator It adds the type send info to the question transition activity and the type receive info to the answer transition activity Typically the instance of a request will first be generated locally by the initia tor It is in state planned When the initiator executes the transition activate the transmission of the question is registered by the system by creating and com pleting the transition activity instance and the request changes to state active When the first answer arrives the initiator executes the transition complete and the request is completed If an additional answer arrives the initiator first exe cutes restart and then complete thus creating an additional transition activity instance of type receive info The addressee role of type request is specified by type request addressee It adds the type receive info to the question transition activity and the type send info to the answer transition activity Typically a request only becomes known to the addressee when the question arrives Then the addressee locally creates the request addressee instance The type immediate may be added to execute the transition activate during creation thus recording the reception of the question When the addressee wants to send the first answer he she executes the transition complete
70. ies by structuring and protocoling Chapter 6 introduced types for activities involving documents additionally supporting the execution of certain subactivities such as printing Chapter 7 introduced types for activities involving communication They add support of execution for communication via electronic media such as electronic mail The object oriented mechanism used as a basis has proven very useful in the design and implementation of this flexible and easily extendible type hierarchy The fine grained multiple inheritance mechanism facilitated the definition of every aspect in a single type The type combination at runtime offers the necessary flexibility to the user In its current state TACTS is only the starting point for a real application However it can already be used successfully to support some specific kinds of work The further evolution of the system should be driven by two directions adding more basic features such as better support for time planning and adding support for specific domains such as collaborative editing of documents The version of TACTS described in this report is fully implemented and is freely available To obtain the system contact the author 70 Bibliography 1 Fish R S Kraut R E Leland M D P Quilt A Collaborative Tool for Cooperative Writing In Allen R B ed Proc ACM SIGOIS IEEE TC OA Conf on Office Information Systems Palo Alto CA Mar 1988 ACM SIGOIS Bulletin 9 2 a
71. il the base s root object is reached or a member has been found 3 2 4 Activity sets The main application of collections in the TACTS system is for activities which are divided into subactivities Allthese activities are collections with a set named subacts containing the direct subactivities Activities with subactivities are described by the type activity set which is a specialization of collection Remember that the type of an object normally is the combination of many other types We use the term is of type X to denote that X is one of the types in the combination or a supertype of one or more of the combined types 15 free collection with time collection member timed collection timed member Figure 3 3 The Types for Time Specifications Every TACTS base is structured in the form of an activity tree The root of the tree is the activity subsuming all other activities in the base Whenever an activity set is attached to an object buffer it displays the list of its members in the object buffer thus giving the user interactive access to these activities With the help of the navigation commands described in Section 3 2 3 the user can move up and down in this tree of activities When a TACTS base is loaded into the system an object buffer is created and the root of the activity tree becomes attached to it thus displaying the list of its immediate subactivities 3
72. in the following way the document is in state undefined iff no file name is specified The file name can only be set or changed during a transition init doc or import doc Erasing the document does not erase the file name thus the same name may be used upon the next initialization or import The additional method get contentsfile simply returns the file name The type defines an additional export system command For this system the address must be an operating system command containing one or more stars All stars are replaced by the content file name and the command is executed The type defines an additional import system file For this system the address must be a file name The name is associated as the new content file name with the document The type filed doc is incompatible to the type intern doc In the current version of TACTS the type filed doc like intern doc does not support ver sions Filed documents are useful if they will be processed by other tools which require the content to be in a file like e g a compiler However filed documents have the disadvantage that they may be changed or erased outside of TACTS In this case TACTS has no information about the change and thus it can not be guaranteed that the state maintained by TACTS actually represents the current state of the document contents 6 5 3 Filed Documents and Structure A filed document may be a structured document or a simple document The first
73. ing the transition complete to make the news transmission mechanism available for the document Additionally the type send doc by news passes the value of the header Newsgroup in the parameter Address to the method export doc at the docu ment The type receive doc by news is a specialization of type two agent trans and receive doc with partner It uses the same parsing function as type receive doc by mail since news articles contain a header From with the same syntax as for mails Note the difference between mail and news For the news system only the activity of receiving is of type two agent trans Instead of the partner agent the activity of sending uses the Newsgroup header to specify the address for export Finally some user packet types are introduced three for each transmission system They are listed in the Table 7 1 The first line gives the user packet types Under every packet type the user concept types are listed which are combined to form the packet type The packets form an easy to use mechanism for handling single mails and single news articles in a way similar to typical user interfaces to both systems As an example an instance of type send mail behaves as described for type send local doc in Section 7 2 1 it uses the agent mechanism to specify the communication partner it records the time of activation and that of sending it stores the content of the mail or news article internally in TACTS and i
74. ion supple ment type charseq send simple doc used for the combination of the types charseq send and simple doc Analogously the type charseq receive simple doc implements the method charseq process by copying the content of the first buffer in the given list into the standard content buffer and saving it Next we handle the content kind Documents of type text doc have as con tent plain text which can be directly handled by the charseq types The content of documents of type binary doc however must first be converted to text be fore it may be transmitted using the charseq types This is done using the UNIX uuencode uudecode mechanism for coding binary data as text The combina tion supplement type charseg send binary doc used for the combination of the types charseq send and binary doc enhances the method charseq prepare by applying uuencode to every buffer in the list The combination supplement type charseg receive binary doc used for the combination of the types charseq receive and binary doc enhances the method charseq process by applying uudecode to the content of every buffer in the given list Note that the user interface for sending and receiving documents is defined by the types doc send via mail doc receive via mail and the correspond ing types for the news system Thus it does not depend on the document content form Text documents and binary documents both are sent by exporting them to system email or news
75. irectly is the name of an emacs buffer This system allows to import the content of an arbitrary buffer manually For the system pipe the address must be an operating system command The command is executed with the standard content buffer as output medium This system allows to import the output of any command as document content 6 4 2 Structured Documents The content of a structured document is a set of documents Structured doc uments are implemented using collections see Section 3 2 The type doc set is a specialization of type collection It introduces the set named subdocs which may be used to hold subordinate document objects The type struct doc is a specialization of edit doc and doc set It uses the set subdocs to store its document parts the set subdocs which contains all direct document part objects The new method show doc parts displays a buffer with a list of all document parts This list can be used in the same way as the list of subactivities of a activity set as an interactive interface to execute operations on the parts For instances of type struct doc the TACTS operations can be used for creating and deleting parts Semantically these operations change the content of the structured document This is the reason for the type struct doc being a specialization of type edit doc Even if no part itself is of type edit doc the document as a whole may be edited by creating and deleting parts Accordingly
76. ivity state member Figure 3 4 The Types for State Management specialize these objects to type timed member if necessary This guarantees that all members of a timed collection which have a time specification are of this type The extended versions of cuttime and subtracttime simply propagate the operation to all members with time specification in all defined sets The extended version of addtime propagates the operation to the collection object if existent and if it has a time specification Note that the type timed collection is not a combination enhancement which is added automatically but a user concept Thus the user may decide whether a collection instance manages time constraints for its members or not 3 4 State Management The last basic mechanism is used to specify a state for activities or other objects The possible states and the transitions between them form a finite state automa ton It enables the specification and use of execution patterns with sequential and parallel subactivities This includes conversation patterns as in Coordinator as well as office procedures as in the DOMINO system The state mechanism was partly developed in 9 Figure 3 4 depicts the part of the TACTS type hierarchy introduced in this section The boxed types have already been introduced in the previous sections 19 activate complete canned active completed unstarted finished Figure 3 5 A Simple Automaton 3 4 1 Automata as T
77. ject of a reply to electronic mail and news articles The type with newsgroup header analogously creates the header News group which is used for news articles For the combination of type with newsgroup header with type reply trans the combination supplement type reply with newsgroup copies the newsgroup header whenever the reference Reply of is set The type with agent from headers is a designer concept type that intro duces the method set agent from headers It takes as arguments the agent attribute to be set and a parsing function The parsing function has to look at the headers and return a predicate for searching and information for creating an agent The method set agent from headers first calls the parsing function Then it invokes the method search member see Section 3 2 3 to search all agent sets on the path to the base s root using the predicate returned by the parsing function If an agent is found it is used to set the agent attribute Oth erwise a new agent is created in the nearest agent set using the information returned by the parsing function and the agent attribute is set to a reference to the new agent As a specialization of the types with agent from headers two agent trans and receive doc with headers the type receive doc with partner is defined Upon transition complete it sets the partner agent from the headers after receiving the document and setting the headers 7 2 3 Sending and Receiving Mail and N
78. ll be modeled by an additional processing step and the resulting postscript document will become a third part of the tex doc which can itself be previewed printed or used in some other way 58 Chapter 7 Communication This chapter describes the support of communication activities The general principle is a mechanism to transmit TACTS documents over electronic media such as electronic mail or USENET news 7 1 Supporting Communication First we introduce the mechanisms for transmitting TACTS documents over elec tronic media This is implemented by types that specialize the types for docu ments defined in Chapter 6 Figure 7 1 depicts the corresponding part of the TACTS type hierarchy For simplicity only the types for sending via electronic mail are included Analogous types exist for receiving and for USENET news 7 1 1 Communication Environments and Addressing The basic concept of supporting communication by supporting the transmission of TACTS documents is a very general approach In the current version of TACTS specific support for two systems is implemented These are the electronic mail system and the USENET news system They were chosen since they are readily available under UNIX and since interfaces for their access exist in GNU emacs In both systems additional information is necessary to specify the details of a transmission For an electronic mail at least the recipient must be given For a news article the newsgroup to be
79. local doc combines the types with doc and doc set and enhances its method created in order to create an object of type doc as subobject and set the attribute Document to a reference to this document Both types can be used for any activity which involves a single subordinate document The type trans doc is the specialization for activities that transmit the document It is a specialization of the types trans info with doc and simple act It couples the transition complete of the activity with a transition either import or export of the referenced document using the value of the attribute Medium as system There are combination supplement types for the combination of trans doc with the types send info and receive info The type send doc sets the transition used at the document to export doc the type receive doc sets it to import doc Next types for the transmission of local documents are introduced Since the document is local to the activity it makes sense to tie the transitions of the docu ment s state even more to transitions of the activity s state than it is done by type trans doc In detail since the document is only involved in the single activity of sending or receiving it it should be fixed after import or export respectively to the communication system This is implemented by the combination supplement type trans local doc used for the combination of the types trans doc and 65 free
80. mp 3 pp 30 37 Hennessy P Kreifelts T Ehrlich U Distributed Work Management Activity Coordination within the EuroCoOp Project Computer Communi cations Butterworth Heinemann Ltd 15 8 477 488 Oct 1992 Johnson Paul Rees Ceri Reusability Through Fine grain Inheritance Soft ware Practice and Experience 22 12 1049 1068 Dec 1992 Karbe Bernhard Wirklichkeitsgerechte Koordinierung kooperativer B rovorg nge In Friedrich J R diger K H eds Computergest tzte Gruppenarbeit CSCW 1 Fachtagung 1991 Bremen Stuttgart 1991 Teubner pp 207 219 Kreifelts T Hinrichs E Klein K H Seuffert P Woetzel G Experi ences with the DOMINO office procedure system In Bannon L Robinson M Schmidt K eds Proc 2nd Europ Conf on Computer Supported Cooperative Work Amsterdam The Netherlands Sep 1991 Dordrecht Boston London Kluwer Academic Publ pp 117 130 Kuutti Kari The concept of activity as a basic unit of analysis for CSCW research ECSCW 91 Proc of the 2nd European Conf on Computer Sup ported Cooperative Work Sep 25 27 1991 Medina Mora Raul et al The action workflow approach to workflow man agement technology CSCW 92 Sharing Perspectives Nov 1992 Neuwirth C M Kaufer D S Chandhok R Morris J Issues in the design of computer support for co authoring and commenting Proceedings of the Conference on Computer Supported Cooperative Work CSCW 90 Lo
81. n an elegant and extremely flexible way It enables the building of complex execution plans by combining and enhancing simple basic plans resulting in a toolkit for execution plans The type with state describes all objects with a state that may change ac cording to an automaton It defines the methods necessary for the mechanism however it only contains the empty automaton no states or transitions defined In this way it is a generic type and allows the incremental definition of any au tomaton by specialization 3 4 2 Operations on Objects with State Whereas an automaton is part of a type description the actual state of an activity is object specific and stored in an attribute State defined by type with state for any of its objects Because we are interested in modeling activities states 20 are of no great interest apart from their identity and possibly a name for output The really important parts are the transitions They describe those situations in which something happens Thus they are candidates for being structured and detailed Every transition consists of at least two steps The first step leaves the source state and begins the transition The second step enters the target state and completes the transition The transition execution may be stopped in between these steps Then the object is in a special state and there are only two possibil ities for going on either completing the transition or resetting the transition
82. nts The headers are not part of the document content Instead they are specified as arguments to every export operation to email Thus the same document may be transmitted several times using different header sets In a similar way the types doc receive via mail doc send via news and doc receive via news define and implement the import system email and the export and import systems news respectively However in both cases of import systems the parameter Address of method import doc is ignored and for the export to news the parameter Address of method export doc is used to specify the newsgroup instead of the recipient 7 1 4 The Interface to the Transmitted Object The types described in Section 7 1 2 implement the interface to the transmission medium Now we will describe the types which implement the interface to the transmitted object in particular to the document content These types are specializations of the types charseq send and charseq receive respectively which implement the methods charseq prepare and charseq process 62 First we define the interface to simple documents This is easy since the content of a simple document can be loaded into a single emacs buffer and can be sent in one part Thus the method charseq prepare simply creates a buffer list containing one buffer and copies the content from the standard content buffer into the single buffer in the list This is implemented by the combinat
83. o all roles should be collected in a single type Then the roles may be specified by specializing this type in various ways One characteristics of the type common to all views is that it must be special ized before it can be used to create an instance of a team activity with a view Every instance is in the user space of a team member and thus should know about the role of that member This is the reason why we call types of this kind virtual types However it may be convenient to create an activity object which is not yet role specific and later determine the role to be used This can be done by creating an instance of a virtual type No role specific operations can be used on this object but at a later time a role may be specified by specializing it to a non virtual type If the team activity is executed following a certain scheme this scheme is a good candidate to be defined in the virtual type The scheme may be defined using the state mechanism introduced in Section 3 4 In this way it is possible e g to define activity patterns in the kind of those used in the Coordinator 11 We will demonstrate this for the simple example of a request between two agents 5 1 3 The Virtual Type for Requests Now we describe the virtual user concept type request It specifies a question of one agent the initiator to another agent the addressee together with one or more answers The initiator and the addressee implicitly form the team which is in
84. o finish all subactivities before finishing the activity as a whole An alternative approach would automatically start or unfinish the collection when it is necessary and it would automatically finish or unstart all members when it is necessary However in general there may be more than one corre sponding transition Without knowing the automata used by the objects it is not possible to decide which transition should be activated in this case For certain activities with a fixed automaton which contains transitions of all four kinds in every state this behavior could be defined as specialization replacing the approach described in this section 3 4 5 Combining State and Time Specification The type timed state couples time specifications and automata The main idea is to automatically set the time during certain transitions This is again based on the mechanism of starting and finishing objects as described in Section 3 4 3 Whenever a starting transition is begun the start time is set to the current time by cutting the activity s time specification with the interval from the current minute to infinity In the same way the end time is set whenever a finishing transition is completed If a transition is both starting and finishing both times are set and the result is a time point specification For every unfinishing transition the time specification is united with the interval from the current minute to infinity This models restarting of an
85. o the type hierarchy designer not to the user Designer concepts are useful for basic mechanisms which need additional specialization before they can be used in an instance e A combination supplement is a type which contains additional features that are needed to make a combination of other types behave in the expected way Combination supplements are not visible to the user They are added to type combinations by automatic specialization In TACTS a simple syntactic convention is used for distinguishing user con cepts and user packets from other types The type names for designer concepts start with a star those for combination supplements start with a percentage sign on 2 1 3 Methods The most important sort of type constituent and the only one predefined in ELIOOS is the method Methods as usual define operations on objects Meth ods associated with type 7 are activated in the context of individual objects of type T A method may have arbitrary many parameters and it may have a result To allow for method combination during multiple inheritance all method parameters are position independent and must be supplied by name value pairs The method body is a sequence of named parts which are executed one after the other The parts may have position constraints before or after relative to parts of the same method of other types Upon combination the part sequences are merged in a way to meet these constrain
86. object Note that the version history for a single object is linear However by copying versions to other objects it is possible to construct version trees for a document In this case every branch of the tree is represented by a separate document object with an own linear version history 6 3 3 Named Versions The type version doc uses time points to reference versions In other systems like RCS SCCS etc versions are usually referenced by arbitrary numbers like 1 4 or 5 23 2 TACTS provides this version naming scheme in a more general way any version interval may be named by an arbitrary string This feature is implemented by the type named version doc It is a spe cialization of type version doc It uses an additional attribute Versionnames to store a mapping from names to version intervals and defines two new meth ods define version name and delete version name to alter this mapping The method export doc is enhanced to accept version references by name as default The method display versions is enhanced to additionally display all defined version names in the list of version intervals UNIX is a registered trademark of AT amp T 45 collection doc set edit doc doc struct doc simple doc version doc homstruct doc struct rooted doc simple edit doc homversion doc Figure 6 3 The Types for Specifying the Structure of Documents 6 4 Document Struc
87. oo on oF He A 3 4 8 Programming of Execution Plans with Refined Transitions 4 The Core of TACTS 4 1 Activities oaoa 4 1 1 The Basic Automata oaoa 20 00 0048 4 1 2 Basic Activities and Structured Activities 4 2 Agents oo 4 2 1 Agent Objects 2 2 oo onen 4 2 2 Agent Sets 2 2 oo 4 2 3 Activities with Agents 2 2 Como nn 4 3 The Executing Agent of an Activity 2 2 2 222 onen 4 3 1 Activities Executed by a Single Agent 4 3 2 Activities Executed by the User 2 22 22 22 4 4 The Partner Agent of an Activity 2 2 2 onen 4 4 1 Specifying an Activity Partner 2 22 22 22 4 4 2 Using the Partner Specification 2 2 2 22 2 20 4 5 Basic Communication 2 2 2 on nn 4 5 1 Information Transmission 2 2 2 2 2 22 4 5 2 Communication with an Activity Partner 5 Requests 5 1 Classes for Team Activities 2 2 Co on nn 5 1 1 Team Activities 22 oo a 5 1 2 Virtual User Concept Types 2 2 2222 5 1 3 The Virtual Type for Requests 2 2 22 22 2 0 5 2 Fixing a Role in Team Actions 2 2 22 5 2 1 Role Specific Types 2 0 ee 5 2 2 The Role Specific Types for Requests 6 Documents 6 1 Abstract Documents aoaaa aaa 6 1 1 Operations on Abstract Documents 6 1 2 The States of Abstract Documents 6 2 Document History 0 0 000200 0202 2 6 2 1 Modeling Document Operations by Subactivities 6
88. or abstract documents The result again is a toolkit which supports a wide variety of document kinds by combining the types for the different aspects in several ways Figure 6 1 depicts the types introduced in the first three sections of this chapter 6 1 Abstract Documents The basis of all documents is formed by the types doc and edit doc They define a minimum of attributes and operations common to all documents Most of the operations are only virtual in that they do not cause any action other than optionally changing the state of the document Thus if the types doc and edit doc are used on their own they can only support recording the state of some document outside the TACTS system The types specify a fairly abstract view of documents It is independent from features like the structure the contents the storing and the use of the document allowing for different variants for every feature and their combination by forming specializations The main property of an abstract document is the fact that it may have some sort of content which may be altered and used At this level any kind of document structure is part of that content 40 start fin state active transitiong doc history doc edit doc version doc history edit doc version edit doc named version doc Figure 6 1 The Types for Documents with History Versions and Structure 6 1 1 Operations on Abstract Documents The type doc defines
89. pecial syntax implemented by lisp macros The hierarchy is loaded when the user starts to work with ELIOOS At any time it is possible to load the definitions of additional types 2 2 2 The User Interface The main user interface is a group of object buffers These are emacs buffers with an attached object from a loaded base Normally an object attaches itself to an object buffer when the method attach is called for it Additionally during the execution of this method the object may display some information about itself in the buffer The system includes additional buffers e g buffers for displaying or editing text One use of these buffers is the direct access to attribute lists of objects for debugging purposes Associated with an object buffer are a number of key combinations for issuing special commands Some of these commands apply to the attached object e g the object can be deleted specialized or a method can be activated for it If the method has parameters their values may be entered interactively using the emacs minibuffer Depending on the type of the attached object there may be additional keys defined which activate methods defined for the attached object Other commands apply to the base of the attached object or to the ELIOOS system as a whole It is possible to create load or save a base and to switch between several loaded bases Finally the user can enter the normal emacs commands for switching between buffers
90. ple internal tex sources a fixed directory is used to run the TEX program and store the resulting DVI files Upon each export to system tex a unique file name is created and the document content is written to that file in the directory Then the TFX program is run on that file This behavior is defined by the combination supplement type simple intern tex source For simple filed tex sources the TFX program runs directly on the content file in the directory where the content file resides This behavior is defined by the combination supplement type simple filed tex source For rooted structured documents the TFX program is executed on the root part see type struct rooted doc Section 6 4 2 by exporting the root part to tex The root part must be a tex source Depending on its kind the TEX program either runs in the directory associated with the type struct filed doc or somewhere else This behavior is defined by the combination supplement type struct rooted tex source The type tex dvi is a specialization of the types binary doc simple doc and filed doc This reflects the fact that TREX always produces its result in a binary format in one part stored in a file As additional supported import system the type tex dvi defines the system tex Importing from system tex is implemented by importing the DVI file produced by the last export of a tex source to system tex Accordingly pro cessing the TEX document a
91. reset act restart act abort act exec by single Cinit by gt by self gt inherit by Partner agent any partner agent Partner agent set upon creation same as parent activity Options has associated document has local document has local internal document partner lt with partner init partner Cinherit partner gt opt with doc with local doc with local intern doc Types for activities lt STOP gt Specific activity kind Information transmission Abbreviations X simple with time specification X with time and subactivities State options may be canceled when planned may be undone when completed X has separate active state may be reset when active may be restarted when completed may be aborted when active activity kind trans info abbrev gt basic action basic project statopt cancel act undo act long act reset act restart act gt abort act Executing agent exec X any single agent by single X single agent set upon creation init by kx partner of parent activity by partner Partner agent partner any partner agent partner agent set upon creation same as parent activity Options has associated document has local document has local internal document with partner init partner inherit partner opt with doc gt with local doc gt with local intern doc
92. s Angeles California 1990 ACM Press 71 9 10 11 Schmid H Mechanismen zur Verwaltung typischer Arbeitsablaufe am In stitut fur Informatik Inst fur Informatik Techn Univ Munchen Munich Germany Master s thesis Nov 1992 Shepherd A Mayer N Kuchinsky A Strudel An Extensible Electronic Conversation Toolkit Proc 3rd Int Conf on Computer Supported Coop erative Work Los Angeles CA Oct 1990 New York SIGCHI SIGOIS ACM pp 93 104 Winograd T A Language Action Perspective on the Design of Cooperative Work Human Computer Interaction 3 1 3 30 1988 72 Index The letters in brackets denote the identifier sort A attribute M method R transition S state T type active transition T 26 active transitions T 19 25 26 36 41 43 charseq hb receive T 61 charseq hb send T 60 61 charseq receive T 60 63 charseq send T 60 63 collection T 12 13 15 16 18 19 22 46 47 49 collection member T 13 15 16 19 23 doc export with headers T 60 62 doc import with headers T 62 free T 11 13 16 19 33 60 66 homstruct part T 48 50 56 homversion part T 50 receive doc with partner T 65 68 state member T 19 22 23 timed member T 16 18 19 22 transition activity T 19 24 with agent T 30 66 with agent from headers T 66 67 with ref T 12 30 33 64 65 Ycharseq receive binary doc T 63 Ycharseq
93. s a whole is implemented by exporting the source to system tex and afterwards importing the DVI part from system tex This is depicted in figure 6 6 Two additional export systems are defined by type tex dvi and can thus be used for objects of type tex doc screen and printer The screen system can be used for previewing the printer system prints the DVI file on the printer specified as address Note that both the source and the DVI file can be printed or viewed by exporting them to printer or screen Because of their different types these operations are executed in a totally different way As mentioned previously exporting the whole TEX document is implemented by processing it if necessary and then exporting the DVI part see Section 6 6 1 Figure 6 6 depicts the three possibilities for exporting to an export system X The implementation of the export of the whole document by operations on the subordinate instances is shown by the dashed lines In the current TACTS version it is assumes that TACTS is running under the X window system and that a postscript printer is available Exporting a 97 DVI file document to screen is directly implemented using the xdvi command exporting to printer is implemented using the dvips driver In future versions it is planned to be more flexible and define specializations for different ways of exporting DVI files In particular exporting to postscript wi
94. s typical for large documents which are changed and re transmitted several times If however a short information is transmitted e g via electronic mail the focus of interest typically is the single transmission activity The document is secondary and should be local to the activity In the current section we define types supporting this kind of communication activities Figure 7 2 depicts the corresponding part of the type hierarchy For simplicity only the types for electronic mail are included Analogous types for the news system exist 7 2 1 Activities for Document Transmission The first step is to introduce activities with an associated document This is done by type with doc which is a specialization of type with ref It defines a new 64 with ref with doc doc set simple act trans info with local doc long act send info trans doc receive info ESS EEE li send doc trans local doc Areceive doc receive doc with partner trans by mail send local doc receive local doc send doc by mail receive doc by mail Figure 7 2 The Types for Activities which Transmit a Document attribute Document which is used to store a reference to a document object This type is further specialized by making the document a subobject of the main activity The corresponding type with
95. see Sec tion 4 2 and the address is stored at the agent and retrieved by the system This has two advantages The addresses are associated with other information about the agent such as the name and this information can be retrieved by the system as well On the other hand the user need not remember the address of an agent for sending a mail The email address for agents is implemented by the specialization agent with email of type agent It defines the key emailadr for the method agent info When given this key the method returns the email address of the agent 7 1 2 The Transmission of Text Pieces with Headers Both in electronic mail and in the news system the content of the transmitted information must be a contiguous piece of plain text We use this property as a characteristics for the most general types defined in this section the designer concept types charseq send and charseq receive These types describe ev ery object that can be converted to or from a contiguous plain text a character sequence which may be transmitted over any medium that supports this kind of 60 content Currently specializations of these types for two kinds of documents and the two communication systems mail and news are implemented The mechanism can easily be extended by defining additional specializations The type charseq send simply defines the method charseq prepare It returns a list of emacs buffers Every buffer contains plain tex
96. t and will be transmitted in one part Analogously the type charseq receive defines the method charseq process It takes a list of emacs buffers as argument Every buffer contains one part which was received Both methods have an empty body They are used as a common interface between specializations for specific transmission media and specializations for specific kinds of transmitted objects Thus it is possible to combine any type for a specific kind of transmitted object with any type for a transmission medium to form a type which implements the transmission of objects of the specific kind over the specific medium The management of a header set is implemented by the types charseq hb send and charseq hb receive They are specializations of the types charseq send and charseq receive respectively They define the additional methods charseq hb prepare and charseq hb process respectively Thus the header management is independent from both the transmission system used and the implementation of preparing and processing the content The method charseq hb prepare takes a header set as argument It invokes the method charseq prepare to prepare the content buffers Then it prepends the given headers to every buffer and returns the list of buffers modified in this way The method charseq hb process takes a buffer list as argument It parses every buffer and extracts the headers from it leaving only the body Then it invokes the method charseq proc
97. t doc Normally they will not be interpreted by TACTS However there are several specializations of doc which define and implement additional systems for export and import respectively The type edit doc supports all these operations as well Additionally a doc ument of type edit doc may be edited which means that the content structure is changed Editing is done in an edit session which may last some time Accord ingly there are two separate operations for starting and ending an edit session The corresponding methods are start edit doc and stop edit doc 6 1 2 The States of Abstract Documents The most important attribute of an abstract document is its content state It is modeled with the help of type start fin state see Section 3 4 3 Here a three state automaton is used with the states undefined existent and fixed The state undefined has the sort unstarted the state fixed has the sort fin ished and the third state has no sort The automaton of type edit doc has the additional sortless state in edit The transitions correspond exactly to the methods for operations described in Section 6 1 1 However not all operations may be done in every state Some of them change the state and some leave it unchanged Figure 6 2 depicts the automaton of type edit doc with all its transitions The transitions are not refined However the method action transit see Section 3 4 2 is enhanced to invoke the method for the corresponding operation
98. t editing are implemented by 46 the combination supplement type simple edit doc The methods for the document operations all use a common standard content buffer which is document specific The type simple doc defines the two methods get contentbuffer which creates the buffer if necessary and loads the current content in it and save contentbuffer which writes the standard buffer s content back into the document The method start edit doc gets the standard content buffer and offers it to the user for editing The method stop edit doc saves the standard content buffer The method erase doc erases the standard content buffer and saves it The methods init doc and fix doc are unchanged with respect to type doc The method export doc is implemented as follows First it gets the standard content buffer The further processing depends on the export system used One additional export system pipe is defined For the pipe system the address must be an operating system command The command is executed and the buffer content is piped into it The method import doc is implemented by first filling the standard content buffer in a system dependent way and then saving it For the predefined import system export the content is simply copied from the standard content buffer of the source document if that was a simple doc Two additional import systems are defined emacs and pipe For the emacs import system the address d
99. t explicitly or by name specification relative to the current time is possible Every defined name for an interval set or a generation function may be preceded by the modifiers next this or last and optionally by a number In these cases the appropriate single interval is selected Thus if suitable definitions for the names are provided specifications such as this month next friday last easter next holiday may be entered The form next 2 hour means the second next full hour interval relative to the current time point Even more flexibility is added by operations defined on interval sets It is possible to unite cut invert or subtract time specifications e Uniting two interval sets produces a new interval set which contains all time points described by at least one of the original sets An example is the uniting of monday with friday to produce monday and or friday Another example is to unite afternoon with weekend e Cutting two interval sets produces a set containing those time points de scribed by both original sets An example is the cutting of monday with afternoon to produce monday afternoon Another typical example is to cut a periodic interval like monday with a single larger interval such as summer semester 1992 which results in all mondays in the summer semester 1992 17 e Inverting an interval set produces a new int
100. t supports printing viewing and other kinds of export for the content at any time As a more complex application these types are used in requests see Chap 68 send mail reply mail receive mail trans by mail trans doc with own doc timed state by self send info init partner with subject header trans by mail trans doc with own doc timed state by self send info with subject header reply trans trans by mail trans doc with own doc timed state by self receive info send news reply news receive news trans by news trans doc with own doc timed state by self send info with newsgroup header with subject header trans by news trans doc with own doc timed state by self send info with newsgroup header with subject header reply trans trans by news trans doc with own doc timed state by self receive info with newsgroup header two agent trans Table 7 1 User Packet Types for Electronic Mail and USENET News ter 5 The type mail request is a specialization of the type request It adds the types common to send mail and receive mail to the transition activities that model the transmissions of the question and the answers 69 Chapter 8 Conclusion The report presented the TACTS activity support system in form of a detailed description of it type hierarchy The Chapters 3 5 introduced types for the sup port of arbitrary activit
101. t until the whole document object is deleted For abstract documents versions are defined al though no content is associated with the versions Version management may be combined with history management without problems 6 3 1 Definition of Document Versions In TACTS versions are defined implicitly as follows A version interval is defined by every maximal time interval for which the object was in one of the states existent or fixed and no state change occurred This definition has several implications First the content can not change during a version interval thus one version of the content is associated with every version interval Second all document operations apart from export doc end or start a version interval Third usually there are time intervals in which no version exists i e the time intervals for which the document is in state undefined or in edit Finally with any given time point at most one version interval is associated Thus version intervals can be referenced by time points Version management for abstract documents is defined by the type version doc which is a specialization of doc The type uses an additional attribute Versionhistory to store the existing versions that is the corresponding time intervals as a list All transitions which start or end a version are extended to change this attribute accordingly The type version doc may be combined with type edit doc to yield editable documents with version
102. the transmission at the transition activity instance 7 1 6 Communication and TEX Documents As an example for the transmission of documents consider the TEX documents described in Section 6 6 3 Both the source part and the processed part of a document may be sent by exporting it to system email or news If the source part is of types simple doc and tex source it is transmitted in one part as plain text The processed part is of type tex dvi which contains the types simple doc and binary doc Thus it is automatically converted to text using uuencode and transmitted in one part As mentioned previously exporting the TEX document as a whole is imple mented by first processing it if necessary and then exporting the processed part This also works for sending the document It is automatically processed by TREX the resulting DVI file is converted by uuencode and then sent out to the com munication medium The situation is that of figure 6 6 if the export system X is replaced by the concrete export system email or news respectively This is a good example of the advantages of an integrated system like TACTS If it is carefully designed several single concepts may be combined to yield additional functionality 7 2 Communication Activities In Section 7 1 we only handled one aspect of transmitting documents The doc ument was the main object the transmission activities played the role of sub activities This situation i
103. the type proc1 doc propagates all those events to the source part which are propagated by homstruct doc to all parts This implies that the history and the versions of the whole document mainly reflect the history and versions of the source Note that the export of old versions auto matically works for the whole document when it is implemented for the source In this case the method process doc processes the old version by exporting the corresponding version of the source to the processing system 6 6 3 TEX Documents As an example for processable documents TACTS defines types for working with TEX The processing of the source text by the TEX program resulting in a file in DVI format is modeled by the specialization tex doc of type procl doc The source part always has the type tex source the processed part has the type tex dvi Figure 6 6 depicts an instance of type tex doc with the subordinate instances of types tex source and tex dvi 56 The type tex source is a specialization of the type text doc It defines the additional export system tex The address is used to specify the TEXvariant to be used such as ATX or AMSTeX The implementation of the export system tex depends on the kind of struc ture and content storing of the TEX source document The current TACTS version defines variants for simple documents internal or filed and for rooted structured documents by defining corresponding combination supplement types For sim
104. ting transition leads from a state of some other sort to an unstarted state The latter two cases are useful for activities which may be reset restarted or undone The type start fin state describes objects which may be started and finished It is a specialization of with state Its automaton is still empty however the four methods start finish unstart and unfinish are defined The methods begin transit reset transit and complete transit are enhanced to detect the kind of the transition based on the sorts of source and target states and if appropriate to invoke the corresponding new method The new methods do not contain any specific operations However they may be enhanced in specializations to execute certain steps during transitions of the corresponding kind Note that a transition is both starting and finishing if it leads from an un started state directly to a finished state In this case first the method start is called by the method begin transit and the method finish is called by the method complete transit Analogously a transition from a finished state to an unstarted state is both unfinishing and unstarting 3 4 4 Combining State and Collections When collections are combined with the state mechanism it is possible to support consistency conditions for the state of all objects in a collection tree like it was shown for the time specification in the types timed collection and timed member in Section 3 3 3 For states the
105. tion abort from state active to aborted The combination of all these types results in the five state automaton de picted in Figure 4 2 Future versions of TACTS will further extend this toolkit of execution plan features 4 1 2 Basic Activities and Structured Activities The type basic activity is a user packet type combining the types timed state and simple act It may be used to represent unstructured activities which are performed in a single step For each instance of type basic activity the user may add a description by adding the type with descr see Section 3 1 2 or 28 undo activate complete planned active completed reset restart cancel abort canceled aborted Figure 4 2 Combining All Predefined Execution Plan Features he she may add other execution plan features by adding the corresponding types described in Section 4 1 1 The type struct activity is a user packet for structured activities It com bines the types basic activity long act timed collection state collection and activity set Thus all structured activities automatically use the three state automaton depicted in Figure 3 5 They maintain consistency conditions between their own state and time specification and those of their subactivities 4 2 Agents Besides activities TACTS also uses agents An agent may represent a person a group of persons an institution or any other instance that may be involved in an activity 4 2 1 Agent Objects
106. tion of a type by the user all types which are incompatible with the set of types selected so far are removed from the menu Additionally all supertypes of selected types are automatically marked as se lected as well Figure 2 1 depicts the menu for the activity types in TACTS see Chapter 4 before and after selecting the type by partner On the right hand side it can be seen that the entries for the types inherit by and by self are removed since they are incompatible with by partner and that the entries for the types by single and init by are marked as well since they are supertypes In other systems the type order is often used to resolve conflicts created by multiple inher itance In ELIOOS another approach is used that handles multiple inheritance in a much more flexible way Types for activities activity lt STOP gt Specific activity kind Information transmission Abbreviations X simple with time specification X with time and subactivities State options may be canceled when planned may be undone when completed X has separate active state may be reset when active may be restarted when completed may be aborted when active Executing agent any single agent single agent set upon creation executed by oneself same as parent activity partner of parent activity by partner kind trans info abbrev basic action basic project gt statopt cancel act undo act tlong act
107. to allow the combina tion of properties and aspects of objects in an easy way There are two levels of configuring the system to the user s needs Upon creation of an object in stance in the system the user may determine the properties of the instance by selecting one or more types from the set of predefined types Additional types may even be added later during the instance s lifetime Aside from this the user may define his her own types by combining and specializing existing types Thus the user may design own tools for supporting activity instances The sup port for user defined types in TACTS is still rudimentary and will be improved However currently it is possible to specify procedure execution plans by defining corresponding types The approach benefits from several specific mechanisms in the object oriented system and from a specific methodology for designing the type hierarchy TACTS is implemented on top of the object oriented system ELIOOS which was specifi cally developed to meet the requirements The type hierarchy is designed using and extending the principle of fine grain inheritance described in 3 This report contains a detailed description of the current type hierarchy im plemented in TACTS It is not meant to be a user manual for TACTS Instead it should serve the following goals First it should be a detailed description of the internal structure of the current TACTS version Second it should demonstrate the prin
108. ts Thus methods may not only be specialized by adding actions to be executed before or after the whole method Instead additional actions may be inserted before or after any method part For documentation purposes every method has a documentation string It should describe the actions invoked by the method parts Upon combination all documentation strings are concatenated to be compatible to the partial order of the types Thus even methods constructed by dynamic combination have a documentation There are some standard methods which are called but not defined by the ELIOOS system itself The most important of them is the method created It is called immediately after the creation of an object and should initialize the object e g create and initialize attributes of the object The method delete is called immediately before an object is deleted the method moved is called immediately after an object has been moved Whenever the type of an object is specialized by adding types the new parts of the method created are executed i e all parts not belonging to the old types method created Thus e g additional attributes may be created and initialized ELIOOS implements this kind of method subtraction for arbitrary methods not only for the method created However normally it does not make sense to apply it to other methods Subtracting a method A from a method B is defined to result in a method C If C and A are combined this yiel
109. ts the combination supplement type simple intern doc implements the methods load doc and store doc thus all operations defined for abstract documents are fully implemented with respect to the content For structured documents the combination supplement type struct intern doc simply passes the property of being internally stored to the parts by specializing them to type intern doc The content storing for simple internal documents is implemented in a way similar to the storing of electronic mails by emacs A single file is used to store all texts and the texts are separated by special headers TACTS uses one such file for every object base Whenever an object of type simple intern doc is moved from one base into another the corresponding text is moved as well its existence provided In the current version of TACTS internal documents do not support version management The type intern doc may be combined with version doc how ever the export of older versions will not work because no content is stored for older versions This will be improved by defining a corresponding combination supplement type 51 6 5 2 Filed Documents An alternative to internal documents are filed documents whose content is stored in the file system Filed documents are defined by the type filed doc which is a specialization of doc It defines the additional attribute Contentsfile which stores a file path name The file name is synchronized with the document state
110. ts representing other things apart from activities as well providing them with a time interval set 3 3 3 Combining Time Specification and Collections When the types collection and with time are combined the resulting type de scribes collections with time specifications For this type it is interesting to define a specialization which couples these features in certain ways This specialization is called timed collection The basic idea of the coupling is to inherit time specifications to and from collection members in a way that the union of all time specifications for members is contained in the time specification for the collection This is consistent with the semantics of activity objects Since subactivities are parts of the main activity they take place during the time in which the main activity takes place The coupling is implemented by extending the methods cuttime and sub tracttime for the collection and by extending the method addtime for every member with a time specification For the latter a type timed member is defined as specialization of with time The methods for creating objects in a timed collection and for moving objects into a timed collection are extended to 18 free collection with state collection member activity set start fin state with time refined transitions state collection timed state active transitions transition act
111. ture The current TACTS version defines two kinds of document structures A sim ple document has as content one unstructured contiguous part For a structured document the content consists of several subdocuments which are themselves rep resented as structured or simple TACTS documents Other document structures could be implemented e g to support multimedia documents or documents with a structure not represented by a set of TACTS documents Figure 6 3 depicts the types defined in this section 6 4 1 Simple Documents A simple document is characterized by the fact that the whole content can be loaded in a single emacs buffer This implies that it has no additional structure which is known by the TACTS system However specializations can be defined which interpret the content in particular ways Simple documents are defined by the type simple doc It is a specialization of type doc and defines the two additional methods load doc which loads the content into an emacs buffer and store doc which replaces the content by the content of an emacs buffer Both methods take a buffer name as argument The method bodies are not implemented in type simple doc because their implemen tation depend on the actual storage mechanism used for the document content However the methods are used as a common interface to implement all other methods that use the content in some way These are in particular all operations on abstract documents The methods for documen
112. ut also all activities on it It becomes an activity set with subactivities History for abstract documents is defined by the type history doc It is a specialization of the types doc and active transitions see Section 3 4 8 If the type history doc is combined with type edit doc the combination supple ment type history edit doc is added which manages protocoling of editing sessions 43 6 2 2 The Subactivities for the Document Methods In detail the methods init doc erase doc export doc and import doc are modeled by transition activities of type basic activity As usual the transition activities are created upon beginning the transition in the automaton of type doc Their transition complete is performed after the document method was success fully called by method action transit In particular their time specification is set automatically to the time point when the operation was executed A descrip tion may be added manually using the type with descr see Section 3 1 2 For documents of type M history edit doc every editing session is modeled by a single subactivity which has the types basic activity and long act It is no transition activity Instead it is created and activated during the transition start edit doc and is completed during the next execution of transition stop edit doc Thus it records the beginning and end time of the session 6 3 Document Versions Version management holds all versions of the document conten
113. utomaton describes short activities which are executed at a single time point Activities of this kind may not be undone or canceled Activities which last some time are described by the specialization long act 27 activity set timed collection start fin state state collection timed state simple act basic activity long act cancel act updo act struct activity reset act restart act abort act Figure 4 1 The Basic Types for Activities of type simple act It adds a new unsorted state active and two transitions activate from state planned to active and complete from state active to completed Additionally it removes the transition complete leading from state planned to state completed The resulting automaton is depicted in Figure 3 5 Activities which may be canceled are described by the specialization type cancel act of type simple act It adds the state canceled of sort finished and the transition cancel from state planned to canceled Activities which may be undone are described by type undo act which adds the transition undo from state completed to planned Specializations of type long act are the type reset act with an additional transition reset from state active to planned the type restart act with an additional transition restart from state completed to active and the type abort act with an additional state aborted of sort finished and a transi
114. volved in the request as a whole The type request is a specialization of the types by single and with partner 36 restart activate complete planned active completed unstarted finished Figure 5 2 The Automaton Used for Requests to record the two agents involved The subactivities of every request are the trans mission of the question from the initiator to the addressee and all transmissions of answers from the addressee to the initiator The execution scheme of type request is defined with the mechanism intro duced in section 3 4 8 The automaton is defined by the combination of the types long act and restart act which results in the automaton depicted in figure 5 2 Both the transitions activate and complete each have one transition activity associated which is of the types basic activity two agent trans inherit by and inherit partner The transition activity of transition complete addition ally contains the type reply trans The transition restart has no associated transition activity The two transition activities each use the automaton of type simple act like all activities of type basic activity Since the single transition of this automaton both starts and finishes the transition activity the transitions of the request all can be done in a single step The transition activity of transition activate models the transmission of the question Since the request can not be undone or reset the transition activate may only
115. ype Constituents In TACTS an automaton is specified by a number of states and a number of labeled directed transitions leading from one state to another The transition labels are locally unique in the sense that in every state for every label at most one transition starts with this label However there may be different transitions with the same label if their starting states are different Every state may have a sort For the use of sorts see Section 3 4 3 below Figure 3 5 depicts an example automaton with three states and two transitions Automata of this kind describe all activities which are executed according to the same pattern Thus an automaton is not a property of a single object Instead like methods automata are part of object type descriptions The specifi cation of an automaton consists of a sequence of commands which add or change its constituents Among these are commands for adding a new state or adding a new transition Types which include an automaton may be combined like other types During this step the automata of the original types are combined into one automaton of the resulting type The combination is done by concatenating all automaton building commands If only commands are used which add elements then the resulting automaton consists of the union of the states and transitions of the original automata This design combines the specification of execution plans with object oriented programming and multiple inheritance i

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