ATL: Atlas Transformation Language User Manual - working draft -
Contents
1. Example Code In this manual the Book to Publication transformation example see Figure 7 for the Book metamodel and Figure 8 for the Publication metamodel serves to illustrate the use of ATL ttitle String Publication title String nbPages Integer authors String Chapter Figure 8 The Publication metamodel nbPages Integer ttitle String author String Figure 7 The Book metamodel The Book to Publication code transforms Books with mode than two pages to Publications The titles of Books and Publications have to correspond The authors attribute of Publication contains all authors of all Chapters The number of pages of a Publication is the sum of all pages ofthe Chapters of a Book module Book2Publication create OUT Publication from IN Book helper context Book Book def getAuthors String self chapters gt collect e e author gt asSet gt iterate authorName acc String acc if acc then authorName else and authorName endif helper context Book Book def getNbPages Integer self chapters gt collect f f nbPages gt iterate pages acc Integer 0 acc pages r rule Book2Publication from b Book Book b getNbPages gt 2 to out Publication Publication title lt b title authors lt b getAuthors nbPages lt b getNbPages Page I Il Figures ATL User Manual Figure 1 The Book metamodel un nee an nl 1 Figure 22. Set new_key further value attributions new key Relational Column name lt objectla further value attributions 2 6 2 Queries and the Generation of Text The ATL programs shown so far are all modules However there are also ATL query programs Queries allow to analyse models and to calculate an output that is not necessarily a model This makes them very handy to generate text or code from a model ALT query programs must start with a query instantiation which consist of the keyword query a query variable an equal sign and an OCL expression initializing the query variable In the following example you see an extract of the XQuery2Code program which transforms XQuery models to code With the allInstances function it runs through all elements of XQuery models The collect function calls the toString helper functions and concatenates the String values that they return The writeTo function writes the concatenation into a dedicated file Please note that there are several toString helper functions During the execution the helper function with the context type that fits best here to the type of the e variable will be chosen for execution In general one can say that this approach simplifies the generation of text or code because the programmer is supported in treating the coding of each metamodel types separately query XQuery2Code XQuery XQueryProgram alliInstances gt collect e e toString write
3. String containing the authorName if acc is empty Otherwise it concatenates and with the authorName The getAuthors function returns the result of the last iteration containing the concatenation of all Authors names Please note Each function must have a name and a return type definition There may be functions with the same name but a different context Ifthe context is not otherwise specified implicitly the module itself is taken as context If the helper has no context defined the helper has to be called with thisModule Page 3 ATL User Manual 2 5 Rules Rules describe the transformation from a source model to a target model by relating metamodels Each rule contains a unique name It is introduced by the keyword rule that is followed by the rule s name Its implementation is surrounded by curly brackets In the source pattern from part rules declare which element type of the source model has to be transformed The source pattern consists of the keyword from an in variable declaration and optionally of a filter A filter is an OCL expression restricting the rule to elements of the source model that satisfy certain constraints The filter is written behind the in variable declaration and surrounded by brackets In the target pattern the to part rules declare to which element s of the target model the source pattern has to be transformed to The implementation of the target pattern declares the details
4. opens the context menu Inthe context menu choose Run in the submenu of Run or choose Debug in the submenu of Debug Having reached the launch configuration view see Figure 5 an ATL transformation is created by selecting the ATL Transformation instance in the configuration tree at the left hand side of the view and pushing the New button below Give to the configuration the same name as to its project choose the corresponding at file and specify the metametamodel EMF or MOF Run Create manage and run configurations Configurations Name XSLT2XQuery E ATL Transformation UMLZJAVA RECE am Configuration 2 model choice E Common XQuery2Code Project XSLT2XQuery KSLTZRQUE anes Project name 5 Java Applet 7 XSLT2XQuery 5 Java Application Ju Junit ATL file name XSLT2XQuery atl Ju JUnit Plug in Test Run time Workbench Others parameters 9 New_configuration Model handler Figure 5 ATL Configuration The next step to take is to specify the metamodels and the models To do so pick the Model Choice panel in the configuration view see Figure 6 and follow these steps Define the IN metamodel s and model variables by writing their names in the designated fields of the IN box add press the Add button For the model and the metamodel names use the same variable name as specified in your ATL file The added variables will be displayed in the path editor table Define t
5. project uses strings Er E2T MatchedRule contents html te E2V MatchedRule oF contents xml Rule for create a XsltRoot Er E2A MatchedRule 3 tre xsl te E2I MatchedRule N tr xsi XML xmi te E2FE MatchedRule a tr xsl XSLT ecore T rule Stylesheet te E25 MatchedRule LA XML xmi from Er E2CO MatchedRule XMLZXSLT asm iroot XML Root te E2C MatchedRule mzxstr atl E ivectcnane aetvecyresheset ER E2W MatchedRule L XSLT xmi E er E2C MatchedRule 88 XQuery2Code y e R EIZEI MatchedRule es Xquery25QL D Akak ends des 68 XSLT2XQuery Problems Properties Console Debug El y 0D Writable Insert Figure 3 ATL IDE for Eclipse 3 2 1 Perspectives In Eclipse the notion of perspective refers to a workbench configuration that is arranged in order to optimise the handling of a certain task For ATL development there are two perspectives of importance namely the ATL perspective and the debug perspective Depending on your Eclipse workbench these perspectives may already be available via buttons in the thumb index on the top right hand side of your workbench Otherwise a left Page 6 ATL User Manual mouse click on the perspective icon displaying a window with subwindows and a yellow cross accessible on the top right hand side of your workbench leads you to a context menu from which Other and then ATL for the ATL development or Debug for the ATL execution in debug mode can be chosen to o
6. ATL Atlas Transformation Language User Manual version 0 2 January 2005 by ATLAS group LINA amp INRIA Nantes working draft Content IS ro A O A A E cease 1 1 1 Te AT EMail a er II A En Ra 1 2 Programming an ATL Module a 1 2 1 o O lee nee 1 2 20 RE 2 2 3 IMPOR 2 A ee ee en IE nenn 3 A O 4 2 0 ATLAdvanced Features ean ea EE R ces e iia 5 2 6 1 Rules with Multiple Instantiations 20 0 0 ceceecceesceesseceseceeeeeeeeeeseeceaeeneeeeeeeensees 5 2 6 2 Queries and the Generation of Teta a 5 Be ee el IDE Tor A a a aea a a a iah 6 3 1 Installing the ATL IDE for Eclipse aia di 6 3 2 Basie Features anne sale ee 6 3 2 1 Perspective Sienen Eee 6 3 2 2 NAO OS 7 3 2 3 O E E AE 7 3 2 4 Outline een 7 3 2 5 A Er aie Rete cna aa Sata sae Gs 8 3 3 Creating o OCU ae a nee ane ae ess 8 A OE 9 3 5 Setting up a Launch Configuration un anne aha 9 3 6 Running an ATL Launch Confisirationz auneran aa 10 3 7 Debugging an ATL Mod llocs Uca 10 A A se S 10 L Example Code cnt tn lia I II NT I ll References a ase Il ATL User Manual 1 Introduction 1 1 The ATL Language ATL the Atlas Transformation Language is the ATLAS INRIA amp LINA research group answer to the OMG MOF 5 QVT RFP 6 It is a model transformation language specified both as a metamodel and as a textual concrete syntax It is a hybrid of declarative and imperative The preferred style of transformation writing is declarative which
7. The Publication metano kei 2 NS 6 Figure 4 Synchronized Cursors of Outline and ATL Editor ocoonnccoccocccononoccnononcnonncnnccnnannonnnonos 8 Figure 5 ATL Ont uri an ebsheapli nee 9 Figure 6 4 Db Model Conheuration ya seine 10 Figure 7 The Pookmeamod La er ae I Figure 8 The Publication metamodel nee Re en HER I Page II ATL User Manual Ill References 1 2 3 4 5 6 7 8 Allilaire F Idrissi T ADT Eclipse Development Tools for ATL EWMDA 2 Kent September 2004 ATLAS group INRIA amp LINA KM3 Kernel MetaMetaModel Manual 2004 ATLAS group Installation of ADT from source 2004 http www sciences univ nantes fr lina atl www papers ATL ATL_Documentation ADTInstallation pdf IBM Eclipse project EMF Documentation http www eclipse org emf OMG MOF Meta Object Facility MOF Version 1 4 formal 2002 04 03 2002 Object Management Group OMG RFP QVT MOF 2 0 Query Views Transformations RFP October 2002 OMG XMI XML Model Interchange XMI OMG Document AD 98 10 05 October 1998 http www omg org SUN netBeans project MDR Metadata Repository http mdr netbeans org Page Ill
8. To C test xquery Page 5 ATL User Manual helper context XQuery XQueryProgram def toString String self expressions gt iterate e acc String acc e toString n helper context XQuery ReturnXPath def toString String self value helper context XQuery BooleanExp def toString String self value 3 The ATL IDE for Eclipse Eclipse is an open universal tool platform for software development and in particular for the construction of IDEs integrated development environments It has been chosen to build the ATL IDE 1 with 3 1 Installing the ATL IDE for Eclipse For the installation of the ATL IDE for Eclipse please consult the ATL installation instructions in 3 3 2 Basic Features The Eclipse environment contains a set of tools and features which have been adapted and extended to best suit the needs of ATL development The principal work environment is called workbench see Figure 3 that contains several subwindows views and toolkits amp ATL XML2XSLT atl Eclipse Platform DER Eile Edit Source Navigate Search Project Run Window Help ES O Q e weo Ef Plugin Devel Debug Can Resource Navigator EN 1 O xQuery2code at Oumznva a 1 XMLZXSLT atl x O B outline ra e amp module XML2XSLT f M amp F create OUT XSLT from IN XML Stylesheet MatchedRule F we uml2Java2 EL XML2XSLT i R T2T MatchedRule B
9. ZA MatchedRule XQuery For var lt var expression lt forExpression Ir forExpression XQuery XPath value lt document xmlFile xml Ir return XQuery Return lt El Problems 32 gt Properties Console Debug Derrors O warnings 0 infos Description Resource In Folder Location Figure 4 Synchronized Cursors of Outline and ATL Editor 3 2 5 Console The Eclipse console shows the output of programs that have been triggered form subordinate runtime workbenches This is a helpful feature for debugging ATL programs that make use of the output lt feature For the creation a subordinate runtime workbench use the right mouse button to pop up the context menu and choose Run in the submenu Run In the run configuration view select Run Time Workbench and click the New button Then select the newly created instance and trigger the subordinate runtime workbench with the button Run As a consequence the standard output of programs running in the subordinate runtime workbench will be displayed in the console of the original workbench 3 3 Creating an ATL Project An ATL project is created with the following actions Inthe Eclipse File menu choose the item New Inthe appearing view choose ATL Project within the ATL folder and click on Next Give the project a sensible name by concatenating the source model name the character 2 and the target model name e g XSLT2XQuery and push the Finish butto
10. amodel The Book metamodel contains the class Book which contains a set of Chapters Books and Chapters have titles Additionally Chapters have a number of pages nbPages and author Page 1 ATL User Manual Publication title String nbPages Integer authors String Figure 2 The Publication metamodel The metamodel Publication consists of the class Publication which has a title a number of pages nbPages and authors The attribute authors is a String that contains the names of authors separated with the word and In the following it will be shown step by step how to program an ATL module that transforms Book models into Publication models An ATL module begins with the header section and ends with the rules section 2 2 Header Section The header section defines the names of the transformation module and the variables of the source and target metamodels The following ATL source code represents the header of the Book2Publication atl file thus the ATL header for the transformation from Book to Publication module Book2Publication create OUT Publication from IN Book The keyword module defines the module name The keyword create introduces the target models declaration The keywords from introduces the source models declaration Please note The ATL file name here Book2Publication atl has to correspond to the module name here Book2Publication and must end with the extension at The same applies to the proje
11. btain the corresponding perspective If ATL is not within the selectable perspectives the ATL plugin has not been successfully installed please reinstall see paragraph 3 1 Please note Only the perspectives ATL or debug should be used for developing projects with ATL or KM3 3 2 2 Navigator The Eclipse navigator shows you the files of your workbench With a right mouse click on a file you obtain a context menu showing you possible actions e g the possibility to open a file in a text editor to display an ATL file with the ATL editor to debug or run an ATL file or to import the Ecore model from a KM3 file 3 2 3 Editors Eclipse facilitates the development of powerful source editors Concerning the ATL development an ATL editor has been implemented that performs syntax highlighting runtime parsing compilation and error detection Modifications of the ATL file that lead to a syntactically correct ATL program will immediately trigger the compilation and thus the generation of a new assembler file at latest when the file is saved An assembler file has the extension asm and contains the compiled code of the corresponding ATL file Please note For the display of ATL files the ATL editor is recommended 3 2 4 Outline The Eclipse outline view gives an overview over the structural elements of the active file in the Eclipse editor with which it is to be synchronized In this sense the ATL editor is in permanent communication wit
12. ct configuration When using the ATL IDE for Eclipse the module here Book2Publication atl the metamodel variable names here N and OUT and metamodel variable names here Publication and Book have to correspond to the launch configuration see paragraph 3 4 2 3 Import Section The import section declares what libraries have to be imported For instance to import the strings library one would write uses strings The keyword uses declares the libraries that have to be imported There can be several import declarations Please note Do not declare imports that are not necessary The string atl library contains many useful functions for Strings but is not necessary for the Book to Publication example The launch configuration see paragraph 3 4 must indicate where the imports are to be found Otherwise imports cannot be uploaded Page 2 ATL User Manual 2 4 Helpers Helpers can be used to define global variables and functions Helper functions are OCL expressions They can call each other recursion is possible or they can be called from within rules see section 2 5 In general they serve to define repetitive pieces of code in one place A helper function has the following structure It starts with the keyword helper and ends with a semicolon In between is an OCL expression The notion of the term context is similar to OCL and it may be compared to an input parameter of a method A context variable is specifie
13. d with the help of the ATL path expression metamodel element and is accessible via the self variable If no context is specified the module itself it taken as context The function name is introduced with def and is followed by brackets The return type is between a colon and an equals sign that serves as starting point for the function implementation The function finishes with a semicolon For the Book to Publication example a getAuthor function has to be implemented Its task is to iterate over the different Chapters of Book in order to build a String containing all Authors names The word and separates the Authors names helper context Book Book def getAuthors String self chapters gt collect e e author gt asset gt iterate authorName acc String acc if ace then authorName else and authorName endif f The context variable self is instance of the class Book Book The collect method gets all author attributes of all Chapters The asSet method eliminates all doublets by converting the sequence to a set The iterate operation is well known from OCL and iterates over a Collection while accumulating data In this case it iterates over the author attributes of all Chapters of a Book and collects the Authors names The variable author Name references the Author s name of the current iteration The variable acc severs to accumulate all authorNames The if expression returns an instance of
14. h a comma The attribution of values is performed with the left arrow operator lt Page 4 ATL User Manual 2 6 ATL Advanced Features The advanced features will be explained using new examples that are will be described in ATL by Examples because the Book2Publication example is too simple for this purpose 2 6 1 Rules with Multiple Instantiations If for one source pattern the from part of a rule several target pattern elements the to part of a rule have to be instantiated we speak of multiple instantiations Multiple instantiations are defined using several target pattern elements in one and the same rule In the Class to Relational transformation there is a rule that for each Class a Table has to be created Additionally each Table has to have a key set containing at least one key In this example the key is a Column with the name objectID However Classes of the source metamodel do not have persistent identifiers surrogates such as keys In this sense for each Class not just a Table but also a key Column has to be instantiated Consequently for the Class2Table rule two target pattern elements are needed namely out for the creation of the Table instance and new_key for the creation of the key Please note that the key attribute of Table which is a set of Columns can be initialized with new key which is a Column rule Class2Table from c Class Class to out Relational Table name lt c name key lt
15. h the outline view Adding the code for a new structural element such as a rule or a helper context function in the ATL editor will automatically lead to a corresponding addition in the outline view at latest when the file is saved Furthermore the cursors in the ATL editor and the outline view will always point to the same structural element see Figure 4 If the cursor is moved in one meaning the ADT editor or the outline the other will replace its cursor correspondingly In the outline view it is possible to set breakpoints for debugging that are marked in the ATL editor with green points Page 7 ATL User Manual E ATL XSLT2XQuery atl Eclipse Platform File Edit Source Navigate Search Project Run Window Help X 19 X Q E G Ei Plug in Devel s Navigator 3 A Oxsurzx0 X E ouT ecore E tr XQue B tr xst CO umzun E help txt S ass xslt X3LT XSLTRootNode PNR EES uml2Java this rule will be called for each XSLTRootNode E XSLT2XQuery Module ce ES XML2XSLT en Gj OUT OclModel ES xQuery2code out XQuery XQueryProgram Gs IN OclModel E 2 Xquery25QL this rule will tanciat rogram variable named out strings LibraryRef 8 XSLT2XQuery which will represent a XQ element in the OUT xmi file Er P2P MatchedRule 8 lt default gt InPattern InPattern Gj T2T MatchedRule ER 12F MatchedRule Eg A2A MatchedRule Ep V2V MatchedRule 1 Eg E2E MatchedRule Eg AL
16. he OUT metamodel and model variables by writing their names in the designated fields of the OUT box add press the Add button For the model and the metamodel names use the same variable name as specified in your ATL file For The added variables will be displayed in the path editor table Page 9 ATL User Manual Inthe path editor select the different variables and attribute the corresponding files Push the Set path button and specify their name If the path is not within the workspace use Set external path Define the libraries used in the Libs panel Please use the corresponding asm files and make sure that the naming import section of your ATL program Create manage and run configurations Configurations Name XSLT2XQuery ATL Transformation UML2IAVA am MOST am Configuration Model choice E common XQuery2Code XSLT2XQuery IN OUT IXSLT2XQuel Model Meta Model Meta Model E Java Applet E Java Application Model l Meta model Add Meta model Ju unit IN XSLT Remove XQuery Ju JUnit Plug in Test Run time Workbench 9 New_configuration Path Editor Model Path XSLT EXSLT2XQuery XSLT xmi OUT OUT Set path Set path XQuery IX5LT2XQuery XQuery xmi Set external path Set external path IN XSLT2XQueryjtr xsi XSLT xmi Remove lib Figure 6 ATL Model Configuration 3 6 Running an ATL Launch Configuration ATL programs can be launc
17. hed from the navigator Right mouse click in the navigator view Inthe context menu choose Run in the submenu of Run Choose the configuration needed and run it by pressing the Run button on the right bottom of the view Another possibility to trigger the execution of an ATL program is to use the run icon depicting a white play forward sign on a green background displayed in the bar underneath the main menu 3 7 Debugging an ATL Module For debug actions it is recommended to switch to the debug perspective Additional to the editor and the outline it contains the debug window that displays the processes terminated or not and the control window that lists all chosen breakpoints and debug variables of ATL programs An essential instrument for debugging is the partial execution step by step or with breakpoints The latter are set with a right mouse button click on a structural element e g a rule in the outline view and then selecting the add breakpoint item To trigger the partial execution use the debug feature by clicking the debug icon You may additionally use the standard output display described in the previous paragraph as a means for debugging 3 8 Log File ADT log files are contained in your workspace log file your_workspace metadata log You can access the error log file via the Help menu Choose About Eclipse Platform then Configuration Details and finally View Error Log Page 10 ATL User Manual
18. means simple mappings can be expressed simply However imperative constructs are provided so that some mappings too complex to be declaratively handled can still be specified An ATL transformation program is composed of rules that define how source model elements are matched and navigated to create and initialize the elements of the target models 2 Programming an ATL Module An ATL module file has the header section the imports section as well as helpers and rules For an ATL module only the header section is mandatory The ATL module is stored in a file with the extension atl Please note To navigate from an element to its attribute write the name of the element then and the name of the attribute If an identifier variable name metamodel name model element name etc is in conflict with a keyword it has to be marked with apostrophes The ATL parser is case sensitive This concerns the file names as much as the source code itself Comments are marked with double dashes 29 29 2 1 Preparation Before an ATL program can be written you must have the target and the source metamodels For the scope of this manual the Book to Publication transformation example see Figure 1 for the Book metamodel and Figure 2 for the Publication metamodel is used to illustrate ATL Ecore models can be defined with KM3 2 Book title String Chapter nbPages Integer title String author String Figure 1 The Book met
19. n Eclipse creates for each project a new folder with the project name This folder can be opened with a double click At the beginning it contains but a project file that the ATL programmer may ignore However for the basic transformation scenario you need an ATL program in the form of an atl file that should bear the same name as the project itself the source and the target metamodels in EMF 4 or MDR 8 formatted in XMI 5 For testing the transformation at least one source model should be available For the development of ATL programs the ATL editor is recommended see paragraph 3 2 3 The creation of an empty file is performed with the following steps Choose the item New in the Eclipse File menu or in the Navigator context menu Select the item File Page 8 ATL User Manual In the appearing view enter the file name and the intended extension e g xmi atl or km3 Make sure that the correct project folder is marked Push the Finish button 3 4 Compilation In the Eclipse environment the compilation of an ATL program to an ASM bytecode file is automatically done in the background e g when saving the ATL program 3 5 Setting up a Launch Configuration The ATL debug and run environment can be set up once you have created the ATL file and the corresponding metamodel and model files To obtain the launch configuration view you can use the context menu in the navigator A right mouse click in the navigator view
20. of the transformation It may contain one or several target pattern elements see paragraph 2 6 1 An target pattern element consists of a variable declaration and a sequence of bindings assignments These bindings consist mainly of left arrow constructs Usually an attribute of the target model out on the left side of the arrow receives a return value of an OCL expression on the right side of the arrow that is based on the in variable In this sense the right side of the arrow may consist of an attribute of the in variable or a call to a helper function which is an OCL expression For the Book to Publication example a rule is required that transforms a Book to a Publication Only Books with more than two pages are considered as Publications The titles of Books and Publications have to correspond The authors attribute of Publication contains all authors of all Chapters For the latter the function getAuthors see section 2 4 and the getNbPages see annex I can be reused The number of pages of a Publication is the sum of all pages of the Chapters of a Book rule Book2Publication from b Book Book b getNbPages gt 2 to out Publication Publication title lt b title authors lt b getAuthors nbPages lt b getNbPages Please note Each rule must have a name that is unique within the module Assignments are separated with comma The last assignment in a block of statements does not end wit
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