Lazy User s Manual and Reference 1 Introduction 2 Installation
Contents
1. simple_expr simple_expr simplexpr free field select include link simple_expr simple_expr A free input field indicates that the given field completely specifies the input method with html or xml tags The input method must provide a value for a parameter named av on_action on string_expression do display insert table_identifier delete update table_identifier keyvalue keyvalue Generate a clickable button with the given label and defines the associated database action Possible actions are e insertt inserts a new tuple in table t the attribute values are given by the set attr fields that appear in the active link anchor delete t a1 v1 deletes all the tuples x from table such that x a vq If v is not specified the value of the a attribute of the current tuple is taken Thus to delete the tuple corre sponding to the displayed content it is sufficient to specify delete T K1 K2 where K K2 form a key of T and T is the base table of this node update t a1 v1 updates all the specified tuples from table t set their values for the non key attributes according to what is specified in the set attr fields keyvalue keyattrident first_level_simple_expression content element_type field field simple_expression fn field field s A2. 5 1 4 Inclusion links The third kind of links is inclusion links An inclusion link immediately include the content of the re ferred link at the indicated place An inclusion link does not have any anchor text Replace href mw_Works_by_artist ano name by include mw_Works_by_artist ano in the node schema recompile it and look at the instance mw_Artist_after 1880 Inclusion and expand in place links offer a very powerful mechanism to build complex nodes with heterogeneous contents Indeed inclusion and expand in place form the basic construct to jump out of the relational box i e to build data presentation that don t look like tables or list of record 5 2 Examples The following node schema presents information about a work of art It uses a one row and two column table The first column td presents textual information and the second one displays a picture of the work The picture s URL is stored in the database attribute picture note how this attribute is used to give its value to the src attribute of the img element This node is based on two tables work and artist because we want to display the author s name which is not in work So we have to join the two tables with the condition work author artist ano In order to show the name of the work s owner we employ another technique which consists in in cluding the mw_Owned node described below node mw_Work id lt table gt lt tr gt lt td gt lt h2 g
3. keyval Z CONNECTION false String r if q1 valid r q1 msg if q2 valid r q2 msg return r The DBServices and QueryResult classes are located in webapps lazy WEB INF classes To compile methods that refers to them it is necessary to add their location to the CLASSPATH For in stance javac MW java classpath TOMCAT_HOME webapps lazy WEB INF classes d TOMCAT_HOME webapps lazy WEB INF classes 9 Commented Lazy 4 Syntax startrule define project project_identifier nodetype xml html purexml purehtm node_def end node_def node node_identifier parameters cachesize number content from_part A node schema has a name and a possibly emtpy list of parameters The from select and order parts determine the list of database tuples to represent in an instance of this node The fields define the repre sentation of each tuple and the links to other nodes parameters parameter parameter parameter identifier identifier letter letter_or_digit _ conent field field field href expand link field field include link active href active_link field_list set_attribute on_action content A field is either the source anchor of a possibly active reference link or the result of including some other node instance at that place or a cont
4. A malicious user 1 get information about the database schema of the appli cation and 2 forge pages containing updates in forms and send them to the server in order to slip wrong data into the database What is encrypted When encryption is turned on the following items are encrypted e All user passwords e All database connection password except the initial lazydict connection e All the table names attribute names key attribute values appearing in forms in HTML pages send to the user How to migrate to the encrypted form The first step consists in choosing a permanent encryption key this key will encrypt user passwords and database connection passwords it must never change This key made of 16 hexadecimal digits is stored in Lazy properties as the encrypt key attribute value encrypt key lt 16 hex digits key gt encrypt off on in Lazy properties Now there is a bootstrap problem if you turn encryption on by setting the encryt off parameter to on in Lazy properties you won t be able to log in any more because the system will try do decypher the stored passwords before comparing them to the typed passwords So you ll need to manually encrypt the ADMIN password in the secure_user database table before proceeding to the next steps This can be done by as follows LAZY_HOME bin gpwd your admin password 33833A88E8F10377 lt your password encrypted with the Lazy key In the database update secure_users set
5. New Node link to create a new node this opens a node input page In the text field type the following node schema text node myNode lt h2 gt My Artist Index lt p gt name birthdate deathdate from artist Click the Compile button to save and compile the node and return to the list of node schemas Now there is a myNode line with either a red or green ball The red ball indicates a compilation error In this case click the pencil icon to edit the node Once the ball is green click the Jnstantiate link to generate a Web page from this new schema In batch mode Create a new text file say myNode lzy with the following content define project MW node myNode lt h2 gt My Artist Index lt p gt name birthdate deathdate from artist end A source file must begin with define and end with end it may contain one or more node schemas The project MW statement indicates that this node belongs to the MW project e Open a new terminal command window e Make sure the environment variables are correctly set and that the lazyenv script has been executed as indicated in the installation instructions under Start the node server e Start the database server and the node server the node compiler stores the compilation result an executable form of the node schema into the database e Compile and install your node schema by typing Unix or Windows Ic myNod
6. The elements placed before and after are generated only once They may contain elements based on aggregate functions like sum max min count The database is queried once for computing these functions If the selection is empty the elements outside are not generated i e the whole node will be empty Example The following node schema is intended to display a list of artists born after a gien date node mw_Artist_after d lt h2 gt Artists born after d lt p gt name born birthdate from artist selected by birthdate gt d order by name An instance of this node say mw_Artist_after 1880 will be constructed as follows 1 Generate the element lt h2 gt Artists born aftera 1880 lt h2 gt d is replaced by its actual value 2 For each tuple t in artist such that t birthdate gt 1880 generate an element of the form lt p gt t name born t birthdate lt p gt To see instances of this node schema go to the IDE page then navigate to Projects gt MW Nodes Then click the nstantiate link on the mw_Artists_afterline Type a date in the parameter field an click the Open button Alternatively you can open the URL http 127 0 0 1 8080 lazy ns a MW mw_Artist_after amp a date where date is the parameter value for d 5 1 2 Links To make an element the origin of a link to another node use the following notation href node name parameter value anchor element Suppose that we want
7. and LazyCompiler properties Edit the file TOMCAT_HOME webapps lazy WEB INF classes Lazy properties and modify the fol lowing lines database url your database JDBC URL database user your database user name sa for hsqldb database password your dataase password empty for hsqldb database driver your JDBC driver Do the same in TOMCAT_HOME webapps lazy WEB INF classes LazyCompiler properties Although these files are not accessible form the Web they should be carefuly protected on your file sys tem since they contain database passwords 3 Modify the scripts to indicate the location of the JDBC drivers The JDBC_DRIVER environment variable indicates where the JDBC drivers are Update its definition in LAZY_HOME bin lazyenv xxx by adding the location of the the new driver s 4 Create the Lazy dictionary Create the tables that will handle the Lazy dictionary node definitions users roles grants etc The LAZY_HOME adm in directory contains the SQL scripts to create these tables Izydict schema sql the tables that stores node definitions or Izydict hsql schema sqlI the same for Hsqldb or Izydict ora schema sqlI the same for Oracle admin schema 41 sql table schemas for all the security related tables or admin hsql schema sql the same for Hsqldb admin init 41 sql initial values for the security tables Note Although SQL is supposed to be the standard data definittion query and manipulation language every DBMS has it
8. to add a link to the works of art of each artist in our mw_Artist_after node Our example already contains a node schema mw_Works_by_artist id that displays all the works by the art ist with number id So we can simply create a link to it as follows node mw_Artist_after_2 d lt h2 gt Artists born after d lt p gt href mw_Works_by_artist ano name born birthdate from artist selected by birthdate gt d order by name About node URLs Normally URLs are automatically generated by the Lazy system when you write an href statement However if you want to refer to a Lazy node from a standard HTML page or directly by entering a URL in the address field of the browser you must use the following scheme http hostname port lazy ns a node_name amp u parameter amp u parameter amp u the standard port used by the tomcat server is 8080 For example to open the node mw_Artist_after_2 1880 on the local machine you must write http 127 0 0 1 8080 lazy ns a mw_Artist_after_2 amp u 1880 5 1 3 Expand in place Links In addition to standard hyperlinks as found in HTML it is possible to define expand in place links These links have a different behaviour when the anchor is clicked it is replaced within the current page by the referred node Example Replace the href keyword by expand href in the mw_Artist_after_2 node schema recom pile it an try clicking on links in the instance mw_Artist_after 1880
9. Lazy User s Manual and Reference G Falquet 2003 1 Introduction Lazy is a language and system to publish databases on the Web and to create Web application interfaces Indeed Lazy creates a hypertext view of a database A hypertext view is a set of nodes the Web pages and hyperlinks that represent the contents of the database In the declarative approach the hypertext components nodes and links are derived from the database content relation tuples according to a hy pertext view specification as shown below are pee lel rtext view ameni Esil Database Hypertext view relations nodes links Hypertext view Specification A hypertext view specification consists of a set of node schemas Every node Web page is an instance of a node schema A node schema is made of a content specification a selection specification and link specifications Node schemas are written in the Lazy specification language The Lazy system is made of a node compiler and a node server The node compiler translates node schmeas into an executable form essentially made of SQL statements The node server dynamiccaly generates node instances ht ml or xml documents from node schemas in compiled form and database elements 2 Installation 2 1 Requirements Since Lazy is entirely written in Java you need a Java 1 4 run time environment installed on your ma chine you can get it from Java soft http java sun com Lazy does not work with Java 1 3 o
10. alue As a consequence the string should never appear in this form in a string 6 3 Datagroups Datagroups are intended to horizontally partition data between different groups of users For in stance the same database could be used to manage data belonging to different departments Datagroups are useful when different groups share the same data structures but not the same data The global vari able GRP represent the datagroup of the current session The dictionary schema given in appendix shows the relationships between all the security and project management related concepts It is a UML view of the Lazy dictionary tables 7 Encryption in Lazy Security in Lazy Because the property files Lazy properties and Compiler properties contain the database password of the db where the Lazy dictionary if not the data is stored it is of the highest importance to protect them against unauthorized access Normally read access to these files should be granted only to the Lazy owner Why encrypt Lazy can connect to several databases the connection password of these databases should be protected In addition the user passwords are stored in the dictlazy database These password should also be pro tected Finally an probably most importantly when Lazy is used to update a database important infor mation such as table names attribute names key attribute values etc may appear as hidden fields in the pages sent to the user
11. ation about the current session These variables are USER the current username GRP the datagroup the user is working in LANG the user s preferred language They can appera anywhere in the definition of a node in the content or in the selection part Example Input variables An input variable is a variable whose value is either entered by the user in an input field set var tex tarea textfield etc or obtained as the value of an expression set var expr Variables can only be set in the definition of an active link It is important to note that the value of an input variable is not available until the active link has been followed by clicking the link s button Hence it cannot be used elsewhere in the node that sets its value However input variable values can be passed as parameter to the target node of the active link with the variable syntax Within the target node or other nodes expressions of the form variable yield the value of the cor responding input variable Examples node Selector active href Works_with_name word lt p gt Word of the work s title set word textfield 20 lt p gt Level of detail 1 9 set detail textfield 1 on Go do display Works_with_name node Works_with_name w title include W_Description detail from works selected by title like concat concat w Internationalized strings To be written 6 Managing projects 6 1 Proj
12. azy home dir gt e g lazy 4 1 TOMCAT_HOME LAZY_HOME tomcat or the location of your Tomcat server JAVA_HOME lt your java installation directory gt e g C jsdk1 4 1 Step 2 Start the database server Open a new shell terminal command window and make sure the environment variables are correctly set Then type runServer sh Unix Linux MacOSX C gt cd LAZY_HOME bin Windows C gt lazyenv C gt runServer Step3 Start the node server with the provided tomcat servlet container Open a new shell terminal command window and make sure the environment variables are correctly set Then type startns sh Unix Linux MacOSX C gt cd LAZY_HOME bin Windows C gt lazyenv C gt startns This starts the tomcat servlet container which is a HTTP server that manages servlets The node server is a Servlet named lazy ns Step 4 Start browsing the virtual museum With your preferred Web browser open the example home page at http 127 0 0 1 8080 lazy and fol low the links to the generated nodes if your Windows machine is not connected to a network it may take some time before it realizes that it can connect to itself sometimes more than 1 min you can also try to stop and restart loading You can also choose to explore the Lazy system by following the Lazy administration link In this case you ll need to log in as a Lazy administrator user admin password x NOTE If you already use ports 8080 and 8007 f
13. base schema It is comprised of a database URL e g jdbc hsqldb hsql localhost a JDBC driver class e g org hsqldb jdbcDriver a username and a password The URL and driver are dbms specific refer to your dbms documentation User a name under which somebody can connect to a Lazy server By default the username PUBLIC is used when opening a Lazy session A user can be defined as administrator In this case she will have full access to every node and data Datagroup a symbolic name for a set of data in a database A tuple in a table may belong to zero or one datagroup thus the same table can hold data belonging to different applications For instance a sin gle database can be used to manage different museums The datagroup of a tuple is indicated by the val ue of an attribute reserved for this purpose When loging in a user can select a datagroup otherwise she will work in her default datagroup Role a role represents a set of access rights to nodes and database tables For instance role VISITOR can accees the node MUSEUM artist_index while role CURATOR can access MUSE UM update_catalog etc An access right is thus a pair role project node or role table The wildcard form project means all the nodes of this project The main advantage of roles is to avoid defining the access rights of each user in each datagroup see grant Grant when connecting a user is granted a set of roles These roles depend on the datagr
14. content element is either a typed element made of one or more subfields or a simple expression A content element surrounded by and is evaluated for each selected tuple Only one such element may appear in a node definition element_type lt element_type_identifier element_attribute_identifier simple_expression gt elem_type_identifier identifier identifier element_attribute_identifier identifier identifier from_part from table_identifier alias_identifier table_identifier alias_identifier distinct select_part group_part order_part group_part group by identifier identifier select_part selected by condition order_part order by simple_expression simple_expression condition not logical_term or logical_term logical_term logical_factor and logical_factor logical_factor simple_expression comparision_op simple_expression is not null comparison_op like lt lt Wat lt gt simple_expression term term term factor factor factor stringconstant numberconstant function_identifier simple_exression simple_exression table_identifier attribute_identifier parameter_ident expression Remarks Aggregate functions min max count avg may not appear in content expressions that are repeat
15. dd5_Artist w lt p gt Click on the Plus 5 button to add 5 years to the birth date of name active href mw_Artist w set birthdate birthdate 5 on Plus 5 do update artist ano from artist selected by ano w Parameter values or any expression can be used as input values as in the following node node mw_add_work_exh e w lt h3 gt Add work title to exhibition title active href mw_Exhibition e set work w set exhibition e lt p gt Comment set org_comment textarea 10 30 on Ada do insert ex_content from exhibition work selected by exno e and wno w The set elements must not be confused with assignment statements The effect of a set takes place only after the corresponding active link has been followed by clicking the button Thus elements like set name Zorro The name is name Will display the value of the name attribute of the currently selected tuple not Zorro More on this in section 5 5 5 4 Designing active nodes There are basically two ways to design active nodes 1 Design form nodes like the mw_new_Artist node above that let the user type data in the input fields 2 Design navigation strategies to collect the requested information through navigation using param eter passing to transmit data from node to node The following nodes show an example of the second design alternative node mw_exhibition_content e display
16. e Izy Once you get an error free compilation instantiate a node by sending the following URL to the node server http 127 0 0 1 8080 lazy ns a myNode It should display a list of artists together with their birthdate and deathdate The LAZY system is a dynamic system once a node definition has been modified and recompiled the new version is immediately available to the clients there is no site generation phase Try modifying myNode recompiling it and reloading the corresponding page into your browser Important note To speed up complex node generation the Lazy node server maintains a server side node cache When a node schema is recompiled all its instances must be erased from the cache How ever in the current version the batch compiler does not clear the cache This must be done manually from the Lazy administration page by clicking the Clear node cache link 4 Creating Hypertext Views on Existing Databases Lazy is aimed at creating hypertext views for existing databases There are two ways to do this depend ing on where you want to keep the Lazy dictionary The Lazy dictionary is a set of database tables that store compiled node definitions project definitions access rights etc You can either continue having HSQLDB manage the Lazy dictionary in a the Hsqldb database that comes with Lazy or create a fresh Lazy dictionary in the existing database 4 1 Keeping the Lazy dictionary in the HSQL database 1 Install a JDBC driver
17. ects A project is mechanism to group a set of node schema that have a common purpose It is similar to a module in a programming language The IDE has an environment to manage project create new projects delete them add update and delete nodes in a project Every project has a set of properties that are inherited by all its nodes e a database connection e formatting files CSS XSL background image e a default node type HTML or XML The full name of a node n belonging to project p is p n When refered from a node of the same project the p prefix can be omitted A database connection is a JOBC connection it is comprised of a database URL a JDBC driver a class name a username and a password Since different projects may use different connections it is possible to build a single Lazy interface on top of several databases 6 2 Users A Lazy user is characterized by his or her username and password Access rights to Lazy nodes and database tables can be assigned to users When a new session is established the user is automatically logged in with ther username PUBLIC If he or she requests a node that has access restriction he or she will be asked to enter a username an password In node schema the session variable USER returns the username Note In the current version session variables are implemented by a string substitution mechanism If the substring variable appears in a string it is replaced by the variable s v
18. ed for each selected tuple contents within and Content expression may not yield a boolean value because the boolean type does not exist in SQL This is not forbidden by the grammar neither checked by the compiler Boolean contents will generate ill formed SQL statements expression condition 10 Glossary of terms Node schema A text written in the Lazy language that defines how to construct a node instance usu ally an HTML or XML page It is comprised of a selection part a content part with links and parameters Node instance A hypertext node usually a HTML or XML page that is part of a hypertext view It is an instance of a node schema Its content depends on the schema definition the actual parameter val ues and the current database contents tables A node is instantiated each time the user clicks on a link to the node or when the node is include in another one see inclusion link Node type The type of content produced when instantiating a node Currently defined types are html xml pure html no heading tag is generated pure xml svg The node type is specified at project level i e all the nodes of a project have the same type Node server The role of the node server is to answer to node requests by instantiating the required node schema with the given parameters It also performs database actions corresponding to active links Node compiler The program that checks the syntax of a node and transf
19. ent element and XML or HTML element with embedded el ements The fields that appear in the source anchor of an active link can set attribute values and define action to undertake when the link is activated field_list field field link include expand href href in target_identifier project_identifier node_identifier simple_expression inclusion_link simple_expression inclusion_link A link is either an inclusion include a reference href or an expand in place expand href It refers to a target node through its identifier and a list of actual parameter values expressions The pa rameter values can also be obtained as the result of an inclusion active_link href project_identifier node_identifier I simple_expression simple_expression set_attribute set attribute_identifier parameter parameter_encoding function_identifier identifier input_field simple_expression Defines the value that will be affected to a tuple attribute by the next insert or update action The set parameter form is used to pass a value an expression or an input value as parameter to the target node In this case the active href node part must not contain parameterter values Parameters are posi tional they must be given in the order defined in the target node schema input_field textfield simple_expr simplexpr textarea
20. for your database management system If your dbms has an ODBC interface e g MS Access you can use the sun jdbc odbc JdbcOdbcDriver driver that comes with the Java installation All you have to do is to create an ODBC source connected to your database Otherwise you ll find the driver either in your dbms distribution or on specific web sites e JDBC drivers for Oracle can be downloaded from Oracle s site they are called oracle jdbc driv er OracleDriver and come in zip files e g classes 12 zip e the hsqldb driver is called org hsqldb jdbcDriver it comes with the Lazy distribution in file lazy cat webapps LAZY database hsqldb lib hsqldb jar One important point is to find the correct URL schema to access your database through JDBC Here are some examples e Oracle thin client jdbc oracle thin hostname 1521 instancename e ODBC source jdbc odbc sourcename e hsqldb jdbc hsqldb hsql hostname 2 Define a new database connection and a new project e Go to http 127 0 0 1 8080 lazy ns a ADMIN all and click on Connections e Create a new database connection e Define a new project and associate it to the new database connection all the nodes of a project access the same database given by the project s database connection e Start creating node schemas in the new project That s all 4 2 Install a new Lazy dictionary in an existing database 1 Install the appropriate JDBC driver see above 2 Update Lazy properties
21. hibition etc and a set of hypertext nodes dynamically generated Web pages to navigate and update the museum Step 1 Set environment variables Before running the Lazy system on the example database you must define the following environment variables LAZY_HOME the installation directory of your Lazy system the full path of your lazy 4 1 directory JAVA_HOME your java installation home TOMCAT_HOME the home directory of your Tomcat server set it to LAZY_HOME tomcat to use the server that comes with Lazy Then you must run a lazyenv script that sets additional variables that depend on these ones On Unix Linux systems with bourne shell or bash Add the following lines to your login or bash_profile export LAZY_HOME lt your lazy home dir gt e g lazy 4 1 export TOMCAT_HOME LAZY_HOME tomcat or the location of your Tomcat server export JAVA_HOME lt your java installation directory gt e g usr on MacOSX source LAZY_HOME bin lazyenv sh On Unix with CShell Add the following lines to your login or cshrce setenv LAZY_HOME lt your lazy home dir gt e g lazy 4 1 setenv TOMCAT_HOME LAZY_HOME tomcat or the location of your Tomcat server setenv JAVA_HOME lt your java installation directory gt e g usr on MacOSX source LAZY_HOME bin lazyenv csh On Windows NT 2000 XP Define the following variables Start gt Settings gt Control Panels gt System gt Advanced gt Environment Variables LAZY_HOME lt your l
22. his table Experimenting The best way to learn the language is by doing your own experiments on the example application Naviation to the MW project an try modifying existing nodes You will also find all the node definitions of the museum example in the example directory of the lazy distribution Designing node schemas that form a good hyperspace is like designing software or buildings there is no general method to do this However you can find design ideas and a design and analysis method ology in the papers published by the ISI research group http cui unige ch isi reports 5 3 Active Nodes and Links An active node is a node that contains active links An active link is a reference link href that triggers a database action when traversed In addition to usual elements the source anchor of an active link can have one or more input elements and must have one action element The general syntax of an active link is Active href node name parameters standard or input or action elements An action element takes one of the following forms e on button label do insert table name e on button label do delete table name key attributes e on button label do update table name key attributes An input element takes the form e set attribute name expression textfield width textfield width initial value textarea nb lines width textarea nb lines width initial value Attribute name must refer to an attribute of the
23. o name location URL ownership work owner acquisition art_cnty artist country activity ex_content work exhibition comment There is a more extensive tutorial on the isi Web site http cui unige ch isi lazy tutorial 5 1 Node syntax A node scheme must be defined in a Lazy source file which is a plain text file It is recommended to use a suffix like Izy or lazy A file that contains node definitions must begin with define and end with end Nodes can also be defined directly with the interactive development environment http 127 0 0 1 8080 lazy ns a ADMIN all A node definition takes the following form node node name parameter name element from table name selected by expression order by expression 5 1 1 Node content The content of a node is specified by a list of elements An element is either a quoted string using double quotes a number literal an attribute name a parameter name or an artithmetic expression An element or a sequence of elements can be given a markup type an HTML or XML tag with the following syn tax lt tag name attribute expression gt element This notation is equivalent to the standard HTML XML notion lt tag name attribute value gt ele ment lt tag name gt Tuple elements All the elements enclosed in and are repeated for each selected tuple of the specified table s These elements represent the selected database tuples
24. or another purpose you can select other ports in the tomcat configuration file TOMCAT_HOME conf server xml Step 5 Stop the node server Open a new shell terminal command window and make sure the environment variables are correctly set Then type stopns sh Unix Linux MacOSX C gt cd LAZY_HOME bin Windows C gt lazyenv C gt stopns 1 If you already have a tomcat server make sure the lazy webapplication is corretly installed 3 Using the Node Compiler The node compiler checks the syntax of a node schema and translates it into a form that is directly exe cutable by the node server It can be used either from the Lazy interactive development environment or in batch mode The following paragraphs show how to define and compile a new node for the virtual museum exam ple interactively and in batch 3 1 With the interactive development environment The interactive development enviroment can be reached from the Lazy start page http 127 0 0 01 8080 lazy by following the Lazy Administration link The Lazy administration page has links to projects users database connections etc 3 2 Navigate to the Projects page to see all the currently defined projects At this point the Lazy server may ask for a username and password by default user ADMIN has password x To define a new node in the virtual museum follow the Nodes link of the MW project It leads to the list of node schemas of the MW project Click the
25. orms is different parts into SQL statements which may still contain placeholders for parameters Link A way to interconnect nodes The source of a link is a content element of a node its destination is anode Lazy links can have four different behaviours reference jump inclusion expand in place and active Reference link A link from a content element to a node When the node is instantiated such a link appears as an undelined text an HTML anchor When it is clicked the referred node is instantiated an replaces the current node the user jumps to the referred node Expand in place link A link from a content element to a node When the node is instantiated such a link appears as an undelined text an HTML anchor When it is clicked the content of the referred node is instantiated in place it replaces the anchor text Inclusion link A link intended to include the content of the target node withing the source node at the link location Inclusion links are useful to create complex node contents Active link A link that triggers a dabase action when it is followed Project A set of nodes that make up a hyperspace intended for a specific purpose All the nodes of a project have the same type html xml purexml purehtml and refer to the same database connection Every node belongs to exactly one project Thus the full name of a node has the form projectname node name Database connection an access to a particular data
26. oup she chose to work in So for instance user JOE could have role VISITOR in the MUSEUM_OF_MODERN_ART datagroup and roles VISITOR and CURATOR in CITY_MUSEUM A grant is thus a triple user dat agroup role If datagroup is it means that this user has this role in all datagroups Servlet Servlet container 11 Bibliography See http cui unige ch isi reports Appendix A The Lazy dictionary conciectid Secure_projects driver projectid url dbconnection useerdb etc pwddb a Secure_RoleNode Secure_roles userid pwd admin defaultgrpid Secure crants lang userid style grpld roleld catld codeld abr listDef D _______sj
27. pwd 33833A88E8F10377 where userid ADMIN Now you can log in as ADMIN an set the other user s passwords they will be encrypted 8 Java Nodes When complex computations are needed or simply functions that do not exist in SQL it is better to express them in an algorithmic language rather than hack computation oriented Lazy nodes For this purpose one can define external nodes the content of which are computed by calling a Java method The name of an external node starts with two underscore characters followed by a class name and a method name The instantiation of such a node will call the corresponding method to generate a node content For instance a content element of the form include _MW artistAbbreviatedName a will call the static method artistAbbreviatedName of class MW and include the resulting string in the node con tent A node method must have one of the following signatures static String methodname String parameterl String parameterN static String methodname String parameter class MW static String artistAbbreviatedName String n String af n int x n indexOf if x gt 1 af n charAt 0 n substring x 1 return af other methods The second form is intended to implement nodes with a varying number of parameters For instance static String concatlf String params String r for int i 0 i lt params length 1 i 2 if params i equal
28. r earlier versions because it uses the new Java encryption scheme The Lazy node server is a servlet application So you need a servlet container server You can either use the tomcat servlet container that comes with the Lazy distribution or download a more recent ver sion from http jakarta apache org 2 2 Downloading and installing Download the zip file from http cui unige ch isi lazy4 download 1 Unzip or gunzip the file into some directory This should create a new directory named lazy 4 x that contains the following subdirectories admin Lazy source code of the interactive development and administration hyperspace bin scripts to start and manage the Lazy system doc documentation examples example hyperspaces hsqldb the hsql database engine http hsqldb sourceforge net with a demo directory that contains the data of the example Web site src the Lazy source code tomcat part of the tomcat servlet container from the Apache Jakartaproject http jakarta apache org webapps lazy contains the lazy web application including the lazy node server servlet NOTE If you already have a tomcat server on your machine copy tomcat webapps lazy to the we bapps directory of your tomcat server and restart tomcat 2 3 Starting the Lazy system with the example application Lazy comes with an example web application for a virtual museum It is comprised of a small database that stores information about works artists ex
29. s yes r r params i 1 return r This class must be compiled and the class file stored in the webapps lazy WEB INF classes directo ry Use for instance the following compilation parameters javac MW java d TOMCAT_HOME webapps lazy WEB INF classes Accesing the database from an external method The following Lazy server methods can be invoked from an external method to execute SQL statements on a database corresponding to a database connection class DBServices ia sql the statement db name of the database connection select must be true for a SELECT statement and false for an INSERT DELETE UPDATE public static QueryResult execSQLonDB String sql String db boolean select r executes the sql statement on the LAZYDICT connection the connection to the Lazy dictionary database public static QueryResult execSQL String sql boolean select r Query results are stored in a QueryResult object defined as follows class QueryResult Statement stmt public ResultSet result public boolean valid true false gt error in query processing public String msg error message if valid false public String sql public int noUpdated 0 Examples static String updel String keyval String val QueryResult q1 execSQLonDB delete from T1 where TK keyval Z_ CONNECTION false QueryResult q2 execSQLonDB update T2 set A val where T2K
30. s own interpretation of that standard Moreover many important functions are left undefined in the standard data conversion string manipulation etc Hence the specific definition scripts and node definitions 5 Recompile the Lazy administration and development nodes Compile the node schemas that are in LAZY_HOME adm These nodes define the administration and development environment to create and compile nodes manage projects users aceess rights connec tions etc This is a good test to see if your LazyCompiler properties file is correct If you forgot to modify this file the compiled nodes will be stored in the cd LAZY_HOME admin lc icon 41 Izy Lazy node compiler 4 0b gt lt lt the url of your database gt gt project ICON connectionld DICTLAZY node maj node del node new Ie node 41 Izy or node 41 for hsqldb Izy for Hsqldb Ie admin 41 1zy 6 Start the node server and test the installation Unix startns sh Windows C gt startns From your Web browser open the URL http localhost 8080 lazy ns a ADMIN all and start browsing the administration and development environment 5 Developing with Lazy Lazy Tutorial This tutorial is based on a simple virtual museum database that is made of the following tables key attributes are in bold work wno author title c_date height width picture artist ano name birthdate deathdate exhibition exno title desc organizer museum mn
31. t title lt p gt c_date lt p gt href mw_Artist ano name lt p gt support height x width lt p gt include mw_Owned wno acquired lt p gt href mw_Works_by_artist ano Works by name lt td gt lt p gt lt img width 200 src picture gt Bs lt hr gt href mw_upd_Work id Update this description from work artist selected by work author artist ano and wno id The following node is simply here to display the name of a museum whose number is given as pa rameter Its purpose is to replace a numeric value here the museum no by a more explicit one This node is used by mw_Work node mw_Owned w href mw_Museum museum name from ownership museum selected by work w and museum mno The inclusion mechanism is interesting to re use nodes and thus to avoid writing many times the same statements For instance the following node defines a node footer also called navigation bar that can be included in many nodes node mw_To_index lt hr gt href mw_Work_index Work index href mw_Artist_index Artist index href mw_Exhibition_index Exhibition index This example also shows a particular use of the selection mechanism The content of this node does not depend on any database table it a kind of constant node However every node must be based on a table So we chose to base it on the naturals table and to select only one tuple from t
32. table mentioned in the action element Example A node to create a new artist node mw_new_Artist lt h2 gt Adding a new artist active href mw_Artist_index lt p gt Unique identifier set ano textfield 10 a number lt p gt Name set name textfield 60 lt p gt Birthdate set birthdate textfield 10 lt p gt Deathdate set deathdate textfield 10 on Ada do insert artist Although this node will act on the artist table by inserting a new tuple its content does not depend on any particular table When generated this node displays the heading text four input fields for ano name birthdate and deathdate and an Add button When the user clicks on on Add the system takes the input values to form a new tuple inserts this tuple into the artist table and then jumps to the node mw_Artist_index It is not mandatory to define all the table s attributes to insert a new tuple only those that are either part of the primary key or not nullable are required The following node enables the user to change the name of a given artist node mw_upd_name_Artist w lt h2 gt Changing the name of artist no w active href mw_Artist w lt p gt Name set name textfield 60 name on Update do update artist ano gt href mw_Artist w Don t change from artist selected by ano w This one adds 5 to the birth date of an artist very useful indeed node mw_a
33. the content of exhibition e title href mw_select_work e Add a Work to this exhibition from ex_content work selected by exhibition e and work wno node mw_select_work e lt h3 gt Select a work to include in the exhibition lt dl gt lt dd gt expand href mw_Work wnol title href mw_add_work_exh e wno Adqd from work The input values can be used as parameters to the destination node For instance the following node reads attribute values for a new artist creates a tuple when the button is clicked and then jump to a node that displays the newly created artist node mw_new_Artist_2 lt h2 gt Adding a new artist active href mw_Artist ano lt p gt Unique identifier set ano textfield 10 a number lt p gt Name set name textfield 60 lt p gt Birthdate set birthdate textfield 10 lt p gt Deathdate set deathdate textfield 10 on Ada do insert artist When the Add button is clicked it inserts a new tuple into artist and then jump to the node mw_Artist ano The ano notation indicates that the value given to the ano attribute in the set ano textfield 10 element must serve as parameter to instantiate mw_Artist In this case it will jump to the node that displays the artist with the number we just entered 5 5 Global variables System variables The Lazy node server maintains a number of system variables taht store inform
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