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{{Backlink|ATL}}
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This page contains a list of common questions related to the use of [[ATL]].
 
+
It gives hints towards solutions as well as links to some concrete examples.
This page contains a list of problems related to [[ATL]] usage.
+
It gives hints towards solutions and links to examples.
+
  
 
__TOC__
 
__TOC__
 +
 +
==How do I launch transformations programmatically?==
 +
 +
=== ATL-specific launch configurations and ANT tasks ===
 +
 +
The ATL development environment provides several base ways of launching transformations:
 +
* by specifying a [[ATL/User_Guide - The ATL Tools#Setting up an ATL run launch configuration|launch configuration]],
 +
* by writing an ant script using the [[ATL/User Guide - The ATL Tools#ATL ant tasks|ATL-specific ANT tasks]].
 +
 +
=== ATL API & Services ===
 +
 +
However, notably for integration purposes in Eclipse solutions, it is necessary to launch transformations by mean of Java code.
 +
 +
This is why ATL directly provides in addition a [[ATL/Developer Guide#Core API|dedicated API and core services]] enabling to run ATL transformations programmatically, including the loading (injection) and saving (extraction) of corresponding required metamodels and models.
  
 
==How do I generate text from models?==
 
==How do I generate text from models?==
Line 14: Line 26:
  
 
You can specify a query over your model in ATL.
 
You can specify a query over your model in ATL.
An example of this is available in the [http://www.eclipse.org/gmt/atl/atlTransformations/#UML2Java UML2Java] transformation.
+
An example of this is available in the [http://www.eclipse.org/atl/atlTransformations/#UML2Java UML-to-JavaCode] transformation.
  
The [http://www.eclipse.org/gmt/am3/zoos/atlanticRasterZoo/ atlanticRaster zoo] is also using this technique.
+
The [http://www.emn.fr/z-info/atlanmod/index.php/Raster atlanticRaster zoo] is also using this technique.
It first transforms KM3 metamodels into DOT models with the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/KM32DOT.atl?rev=HEAD&content-type=text/vnd.viewcvs-markup KM32DOT.atl] transformation.
+
It first transforms KM3 metamodels into DOT models with a KM32DOT.atl transformation. It then uses DOT2Text.atl to query a string, corresponding to the generated DOT code, from the DOT model.
It then uses [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/DOT2Text.atl?rev=HEAD&content-type=text/vnd.viewcvs-markup DOT2Text.atl] to query a String from the DOT model.
+
These two ATL transformation/query can be found from [http://www.eclipse.org/atl/atlTransformations/#KM32DOT here].
This string corresponds to the generated DOT code.
+
Then, the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/build.xml?rev=HEAD&content-type=text/vnd.viewcvs-markup build.xml] ant scripts makes use of the [[AM3_Ant_Tasks#am3.saveModel|am3.saveModel]] task with an ATL extractor pointing to the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/DOT2Text.atl?rev=HEAD&content-type=text/vnd.viewcvs-markup DOT2Text.atl] transformation.
+
  
===Using TCS===
+
Then, an ANT script makes use of the [[ATL/User Guide - The ATL Tools#Task atl.saveModel|atl.saveModel]] task with an ATL extractor pointing to the DOT2Text.atl transformation.
  
[[TCS]] (Textual Concrete Syntax) is a tool enabling the specification of textual syntaxes for metamodels.
+
===Using other tools===
Once such a syntax has been specified, models can be serialized to text files.
+
  
One advantage of TCS is that text can also be parsed into models.
+
The [http://www.eclipse.org/Xtext/ Xtext] framework in Eclipse Modeling is dedicated to this kind of tasks.
It is therefore possible to use the same specification to enable the definition of models with any text editor.
+
  
==How do I launch transformations programmatically?==
+
[[TCS]] (Textual Concrete Syntax) is also a tool enabling the specification of textual syntaxes for metamodels.
 
+
The ATL development environment (ATL Development Tools, or ADT) provides several means to launch transformations:
+
* by specifying a launch configuration,
+
* by writing an ant script using the [[AM3 Ant Tasks]].
+
 
+
However, in some cases, it is necessary to launch an ATL transformation from Java code.
+
The [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.eclipse.engine/src/org/atl/eclipse/engine/AtlLauncher.java?rev=HEAD&content-type=text/vnd.viewcvs-markup AtlLauncher] class can be used for this purpose.
+
The [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.eclipse.km3/src/org/atl/eclipse/km3/KM3Projector.java?rev=HEAD&content-type=text/vnd.viewcvs-markup KM3Projector] class of the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.eclipse.km3/src/org/atl/eclipse/km3/ KM3 plugin] contains example usages of the AtlLauncher class (e.g. the getEcoreFromKM3 method).
+
  
Remark 1: the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.eclipse.engine/src/org/atl/eclipse/engine/AtlCompiler.java?rev=HEAD&content-type=text/vnd.viewcvs-markup AtlCompiler] class may be used to compile ATL transformations into .asm files executable on the ATL Virtual Machine.
+
==How do I declare/use external parameters in ATL transformations?==
  
Remark 2: There may be problem when using MDR as model handler, as it shown in [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.eclipse.km3/src/org/atl/eclipse/km3/KM3Projector.java?rev=HEAD&content-type=text/vnd.viewcvs-markup KM3Projector] class. Call to initMDR() method should be done only once when your class is constructed. This is because if you load your model in this way: getMDRModelHandler().loadModel("model.xmi", getSomeMetamodel(), mod.openStream()); method getSomeMetamodel() will return reference to metamodel which is initialized in initMDR(). If some of your methods later call initMDR() your initial metamodel reference will be lost and someMetamodel variable will get reference to new metamodel. Result of your transformation will be output model file, because input model has lost his metamodel reference.
+
===Using an XML file===
 +
A solution is to save transformation parameters in a extern XML model. In the transformation, you will use an ''helper'' to get parameters from your model.
  
==How do I use extern parameters in ATL transformations?==
+
To inject and/or extract XML models (and to get the simple XML metamodel in Ecore), you can check out and install the [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/ org.eclipse.m2m.atl.projectors.xml] plugin with your ATL Eclipse install.
 
+
===Using an XML file===
+
A solution is to save transformation parameters in a extern XML model. In the transformation, you will use an ''helper'' to get parameters from your model. The wanted parameters model will be chosen in the transformation launch configuration or in the [[AM3 Ant Tasks]].
+
  
 
The following code is a simple parameters XML file:
 
The following code is a simple parameters XML file:
 
<pre>
 
<pre>
 
<parameters>
 
<parameters>
<param name="source" value="KM3"/>
+
<param name="param1" value="valueX"/>
<param name="target" value="ATL"/>
+
<param name="param2" value="valueY"/>
 
</parameters>
 
</parameters>
 
</pre>
 
</pre>
  
In the transformation header, you add the ''parameters'' model and its metamodel
+
In the transformation header, you add the ''parameters'' model and its [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/model/ XML metamodel]:
[http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlantic/XML.km3?rev=1.1&only_with_tag=HEAD&content-type=text/vnd.viewcvs-markup XML.km3] :
+
 
<pre>
 
<pre>
 
module AMW2ATL;
 
module AMW2ATL;
create OUT : ATL from source : MOF, target : MOF, parameters : XML;
+
create OUT : XXX from IN : YYY, parameters : XML;
 
</pre>
 
</pre>
  
Line 74: Line 71:
 
</pre>
 
</pre>
  
To used the previous helper (due to the ''getAttrVal'' call), you need to used [http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/XMLHelpers.asm?rev=1.1&content-type=text/vnd.viewcvs-markup XMLHelpers.asm] ATL Library and add in the transformation:
+
To use the previous helper (due to the ''getAttrVal'' call), you need to use [https://gforge.inria.fr/scm/viewvc.php/*checkout*/AtlanticRaster/build/XMLHelpers.asm?revision=6&root=atlantic-zoos XMLHelpers.asm] ATL Library and add in the transformation:
 
<pre>
 
<pre>
 
uses XMLHelpers;
 
uses XMLHelpers;
 
</pre>
 
</pre>
  
The following code, it is a simple example to show how to used ''getParameter'' helper:
+
The following code is a simple example to show how to use the ''getParameter'' helper:
 
<pre>
 
<pre>
 
helper def : sourceValue  : String = thisModule.getParameter('source');
 
helper def : sourceValue  : String = thisModule.getParameter('source');
 
</pre>
 
</pre>
  
In [[AM3 Ant Tasks]], you need to add the ''parameters'' model, the [http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlantic/XML.km3?rev=1.1&only_with_tag=HEAD&content-type=text/vnd.viewcvs-markup XML.km3] metamodel and the [http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/XMLHelpers.asm?rev=1.1&content-type=text/vnd.viewcvs-markup XMLHelpers.asm] library. For this you need parameters.xml model in ecore.
+
==How can I handle arbitrary XML documents?==
See the following example:
+
<pre>
+
<am3.loadModel modelHandler="EMF" name="KM3" metamodel="MOF" path="uri:http://www.eclipse.org/gmt/2005/KM3"/>
+
  
<am3.loadModel modelHandler="EMF" name="XML" metamodel="KM3" path="XML.km3">
+
Arbitrary XML documents can be used as source or target of ATL transformations.
<injector name="ebnf">
+
However, this cannot be done directly (see [[ATL_Howtos#How can I tune the XML output of ATL?|next section]]) but rather through specific injectors and extractors.
<param name="name" value="KM3" />
+
</injector>
+
</am3.loadModel>
+
  
<am3.loadModel modelHandler="EMF" name="Parameters" metamodel="XML" path="Parameters.xml">
+
Injecting XML files as XML models or extracting XML models as XML files can be performed thanks to the the [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/ org.eclipse.m2m.atl.projectors.xml] plugin and [[ATL/User Guide - The ATL Tools#ATL ant tasks|ATL-specific ANT tasks]].
<injector name="xml"/>
+
</am3.loadModel>
+
  
<am3.atl path="myTransformation.atl">
+
A version of this plugin built for the Juno ATL version can be downloaded from [http://docatlanmod.emn.fr/ATL/Plugins/org.eclipse.m2m.atl.projectors.xml_0.4.0.jar here] and has to be copied to the ''dropins'' folder of your Eclipse install before starting.
<inModel name="source" model="left"/>
+
For other ATL versions, the plugin sources first have to be checked out into your workspace in order to re-export the plugin as a compatible deployable one (to be then copied to the ''dropins'' folder similarly as mentioned before).
<inModel name="target" model="right"/>
+
<inModel name="MOF" model="%EMF"/>
+
  
<inModel name="parameters" model="Parameters"/>
+
==How can I tune the XML output of ATL?==
<inModel name="XML" model="XML"/>
+
<library name="XMLHelpers" path="XMLHelpers.asm"/>
+
  
<inModel name="ATL" model="ATL"/>
+
The ATL Virtual Machine can write target models to XML files in two different ways:
<outModel name="OUT" model="ATLmodel" metamodel="ATL"/>
+
* XMI writing is delegated to EMF.
</am3.atl>
+
* Target models can be extracted into XML files using custom XML Schemas.
  
<am3.saveModel model="ATLmodel" path="ATLmodel.ecore"/>
+
To do this, the target model is first transformed into a model conforming to a [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/model/ specific XML metamodel].
</pre>
+
The resulting XML model can then be extracted into an XML document.
 +
An example can be found in the [http://www.eclipse.org/atl/atlTransformations/#Table2SVGPieChart Table2SVGPieChart] transformation scenario: the target SVG model is transformed into an XML model that can then be extracted (see documentation of scenario for more details and README.txt in zip file for directions).
 +
The process of transforming a model to XML then extracting it can be automated using [[ATL/User Guide - The ATL Tools#ATL ant tasks|ATL-specific ANT tasks]] and the ''org.eclipse.m2m.atl.projectors.xml'' plugin (see [[ATL/Howtos#How can I handle arbitrary XML documents?|previous section]]).
  
Instead of [[AM3 Ant Tasks]], if you use ATL launch configuration then you need to inject
+
==How can I implement my own injector or extractor?==
[http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlantic/XML.km3?rev=1.1&only_with_tag=HEAD&content-type=text/vnd.viewcvs-markup XML.km3] metamodel and parameters.xml into ecore model. Moreover, you need to add
+
[http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/org.eclipse.gmt/AM3/org.eclipse.am3.zoos.atlanticRaster/build/XMLHelpers.asm?rev=1.1&content-type=text/vnd.viewcvs-markup XMLHelpers.asm] ATL library.
+
  
==How can I specify a Virtual Machine operation in Java?==
+
An injection/extraction is a transformation from/to another Technical Space (e.g., XML, Grammarware) to/from the Model Engineering Technical Space.
 +
An injector/extractor is a component implementing an injection/extraction.
  
It is possible to add new Java operations to the ATL Virtual Machine (VM).
+
Injectors and extractors may be then used programmatically or via ATL-specific ANT tasks [[ATL/User Guide - The ATL Tools#Task atl.loadModel|atl.loadModel]] and [[ATL/User Guide - The ATL Tools#Task atl.saveModel|atl.saveModel]].
These operations can then be called like helpers.
+
  
The [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.eclipse.gmt.atl.oclquery.core/ org.eclipse.gmt.atl.oclquery.core] plugin offers the [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.eclipse.gmt.atl.oclquery.core/src/org/eclipse/gmt/atl/oclquery/core/ATLVMTools.java?rev=HEAD&only_with_tag=HEAD&content-type=text/vnd.viewcvs-markup org.eclipse.gmt.atl.oclquery.core.ATLVMTools] class to create instances of [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.engine.vm/src/org/atl/engine/vm/Operation.java?rev=HEAD&content-type=text/vnd.viewcvs-markup org.atl.engine.vm.Operation] and to register them in the ATL VM.
+
To be usable in practice, an injector/extractor must implement the IInjector/IExtractor interface (cf. [[ATL/Developer Guide#Core API|ATL Core API documentation]]), as shown by the [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/src/org/eclipse/m2m/atl/projectors/xml/ XML injector/extractor example] for instance.
 +
It must also declare explicitly the use of the specific org.eclipse.m2m.atl.core.injector/extractor extension points, as shown by the [https://dev.eclipse.org/svnroot/modeling/org.eclipse.mdt.modisco/incubation/trunk/am3/plugins/trunk/org.eclipse.m2m.atl.projectors.xml/plugin.xml same example than before].
  
This is used in [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.eclipse.gmt.atl.oclquery.core/src/org/eclipse/gmt/atl/oclquery/core/OclEvaluator.java?rev=HEAD&content-type=text/vnd.viewcvs-markup org.eclipse.gmt.atl.oclquery.core.OclEvaluator] to redefine the dumpASM method of ASMEmitter.
+
==How can I transform UML models?==
The process to register operations on OCL primitive types (e.g. Boolean, Integer, String) is similar.
+
  
==How can I tune the XML output of ATL?==
+
There are several implementations of UML.
 +
The one we consider here is the de-facto standard implementation from Eclipse: [[MDT-UML2|the UML2 project]].
  
The ATL Virtual Machine can write target models to XML files in two different ways:
+
ATL allows to transform such UML models as any other EMF models.
* XMI writing is delegated to the [[ATL_Model_Handlers|model handler]] used to handle the model (e.g., EMF, MDR).
+
It is usually not possible to change the target format in this case because XMI support in each model handler implements a precise mapping from a metamodel to an XML Schema.
+
However, different model handlers may produce different XMI files (e.g., XMI 2.0 with EMF, XMI 1.2 with MDR).
+
* Target models can be extracted into XML files using custom XML Schemas.
+
To do this, the target model is first transformed into a model conforming to a [http://www.eclipse.org/gmt/am3/zoos/atlanticZoo/#XML specific XML metamodel].
+
The resulting XML model can then be extracted into an XML document.
+
An example can be found in the [http://www.eclipse.org/gmt/atl/atlTransformations/#Table2SVGPieChart Table2SVGPieChart] transformation scenario: the target SVG model is transformed into an XML model that can then be extracted (see documentation of scenario for more details and README.txt in zip file for directions).
+
The process of transforming a model to XML then extracting it can be automated using [[AM3_Ant_Tasks|ant tasks]].
+
This is also illustrated by the Table2SVGPieChart scenario (see build.xml in the zip file).
+
  
Remarks:
+
The UML2 metamodel must be loaded from the EMF registry (i.e., by namespace URI).
* You always obtain XMI files (and thus non-customizable XML output) after running a launch configuration.
+
This can be done using the "EMF Registry..." button of the ATL launch configuration, or using the nsURI attribute of the [[ATL/User Guide - The ATL Tools#Task atl.loadModel|atl.loadModel]] task.
To obtain a custom XML file, you need to use the XML extractor (see build.xml in the zip file of Table2SVGPieChart for directions).
+
  
==How can I handle arbitrary XML documents?==
+
Usage of [[ATL/User Guide - The ATL Tools#Content assist|content assist]] (i.e., code completion) is especially useful with big metamodels like UML2.
  
Arbitrary XML documents can be used as source or target of ATL transformations.
+
==How can I retrieve tagged values from stereotyped UML model elements?==
However, this cannot be done directly (see [[ATL_Howtos#How_can_I_tune_the_XML_output_of_ATL.3F|previous section]]) but rather through injectors and extractors.
+
  
The XML injector can be executed from the contextual menu on files with the .xml extension, or from the [[AM3_Ant_Tasks#am3.loadModel|am3.loadModel]] ant task. An example of using the XML injector is given in the [[ATL_Howtos#How_do_I_use_extern_parameters_in_ATL_transformations.3F|how to use external parameter]] section.
+
In ATL, a profiled UML model used as source model is viewed like any other UML model.
 +
You generally (i.e., when the profile is referenced with a valid relative path) do not have to specify the profile used with the model.
 +
So, in the header of the ATL module you just have:
  
The XML extractor can be executed from the contextual menu on files with the .ecore extension, or from the [[AM3_Ant_Tasks#am3.saveModel|am3.saveModel]] ant task.
+
module uml2something;
 +
create OUT : targetMetamodel from IN : UML;
  
The XML injector is implemented in [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.engine.vm/src/org/atl/engine/injectors/xml/XMLInjector.java?view=markup XMLInjector], which extends [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.engine.vm/src/org/atl/engine/injectors/Injector.java?view=markup Injector].
+
If atl seems to ignore your stereotypes, you can add your profile as source model. You obtain the following header:
  
The XML extractor is implemented in
+
module uml2something;
[http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.engine.vm/src/org/atl/engine/extractors/xml/XMLExtractor.java?view=markup XMLExtractor], which extends [http://dev.eclipse.org/viewcvs/indextech.cgi/org.eclipse.gmt/ATL/org.atl.engine.vm/src/org/atl/engine/extractors/Extractor.java?view=markup Extractor].
+
create OUT : targetMetamodel from IN : UML, INPROFILE : profile;
 +
 
 +
After that you can use operations like:
 +
* getAppliedStereotype(sterotypeName : String) on a UML element to get the stereotype with the name "stereotypeName" applied on this element. This operation needs the fully qualifed name of the stereotype so it looks like: profileName::sterotypeName.
 +
* getValue(stereotype : Stereotype, propertyName : String) to get the Value of the tagged value with name "propertyName" on the stereotype "stereotype" (the sterotype can be retrieved by getAppliedStereotype).
 +
 
 +
A helper like:
 +
 
 +
helper context UML!Element def: hasStereotype(name : String) : Boolean =
 +
not self.getAppliedStereotype(name).oclIsUndefined();
 +
 
 +
can also be useful to check if a stereotype is applied on the UML element before trying to retrieve it or to get a tagged value from it.
 +
As it uses getAppliedStereotype, it needs the fully qualified name of the stereotype (e.g., profileName::sterotypeName).
 +
 
 +
==How can I specify a Virtual Machine operation in Java? (Deprecated)==
 +
 
 +
It is possible to add new Java operations to the ATL Virtual Machine (VM).
 +
These operations can then be called like helpers.
 +
 
 +
The {{ATLRepositoryLink|deprecated/org.eclipse.gmt.atl.oclquery.core/|org.eclipse.gmt.atl.oclquery.core}} plugin offers the {{ATLRepositoryLink|deprecated/org.eclipse.gmt.atl.oclquery.core/src/org/eclipse/gmt/atl/oclquery/core/ATLVMTools.java|org.eclipse.gmt.atl.oclquery.core.ATLVMTools}} class to create instances of {{ATLRepositoryLink|deprecated/org.atl.engine.vm/src/org/atl/engine/vm/Operation.java|org.atl.engine.vm.Operation}} and to register them in the ATL VM.
 +
 
 +
This is used in {{ATLRepositoryLink|deprecated/org.eclipse.gmt.atl.oclquery.core/src/org/eclipse/gmt/atl/oclquery/core/OclEvaluator.java|org.eclipse.gmt.atl.oclquery.core.OclEvaluator}} to redefine the dumpASM method of ASMEmitter.
 +
The process to register operations on OCL primitive types (e.g. Boolean, Integer, String) is similar.
  
 
[[Category:ATL]]
 
[[Category:ATL]]

Latest revision as of 06:38, 4 June 2013

This page contains a list of common questions related to the use of ATL. It gives hints towards solutions as well as links to some concrete examples.

How do I launch transformations programmatically?

ATL-specific launch configurations and ANT tasks

The ATL development environment provides several base ways of launching transformations:

ATL API & Services

However, notably for integration purposes in Eclipse solutions, it is necessary to launch transformations by mean of Java code.

This is why ATL directly provides in addition a dedicated API and core services enabling to run ATL transformations programmatically, including the loading (injection) and saving (extraction) of corresponding required metamodels and models.

How do I generate text from models?

There are several possibilies. We only detail some of them here.

Using ATL

You can specify a query over your model in ATL. An example of this is available in the UML-to-JavaCode transformation.

The atlanticRaster zoo is also using this technique. It first transforms KM3 metamodels into DOT models with a KM32DOT.atl transformation. It then uses DOT2Text.atl to query a string, corresponding to the generated DOT code, from the DOT model. These two ATL transformation/query can be found from here.

Then, an ANT script makes use of the atl.saveModel task with an ATL extractor pointing to the DOT2Text.atl transformation.

Using other tools

The Xtext framework in Eclipse Modeling is dedicated to this kind of tasks.

TCS (Textual Concrete Syntax) is also a tool enabling the specification of textual syntaxes for metamodels.

How do I declare/use external parameters in ATL transformations?

Using an XML file

A solution is to save transformation parameters in a extern XML model. In the transformation, you will use an helper to get parameters from your model.

To inject and/or extract XML models (and to get the simple XML metamodel in Ecore), you can check out and install the org.eclipse.m2m.atl.projectors.xml plugin with your ATL Eclipse install.

The following code is a simple parameters XML file:

<parameters>
	<param name="param1" value="valueX"/>
	<param name="param2" value="valueY"/>
</parameters>

In the transformation header, you add the parameters model and its XML metamodel:

module AMW2ATL;
create OUT : XXX from IN : YYY, parameters : XML;

From parameters model, the following helper is used to get value attribute select in the param entities according to the given name:

helper def : getParameter(name : String) : String =
	XML!Element.allInstancesFrom('parameters')->select(e |
		e.name = 'param'
	)->select(e |
		e.getAttrVal('name') = name
	)->first().getAttrVal('value');

To use the previous helper (due to the getAttrVal call), you need to use XMLHelpers.asm ATL Library and add in the transformation:

uses XMLHelpers;

The following code is a simple example to show how to use the getParameter helper:

helper def : sourceValue  : String = thisModule.getParameter('source');

How can I handle arbitrary XML documents?

Arbitrary XML documents can be used as source or target of ATL transformations. However, this cannot be done directly (see next section) but rather through specific injectors and extractors.

Injecting XML files as XML models or extracting XML models as XML files can be performed thanks to the the org.eclipse.m2m.atl.projectors.xml plugin and ATL-specific ANT tasks.

A version of this plugin built for the Juno ATL version can be downloaded from here and has to be copied to the dropins folder of your Eclipse install before starting. For other ATL versions, the plugin sources first have to be checked out into your workspace in order to re-export the plugin as a compatible deployable one (to be then copied to the dropins folder similarly as mentioned before).

How can I tune the XML output of ATL?

The ATL Virtual Machine can write target models to XML files in two different ways:

  • XMI writing is delegated to EMF.
  • Target models can be extracted into XML files using custom XML Schemas.

To do this, the target model is first transformed into a model conforming to a specific XML metamodel. The resulting XML model can then be extracted into an XML document. An example can be found in the Table2SVGPieChart transformation scenario: the target SVG model is transformed into an XML model that can then be extracted (see documentation of scenario for more details and README.txt in zip file for directions). The process of transforming a model to XML then extracting it can be automated using ATL-specific ANT tasks and the org.eclipse.m2m.atl.projectors.xml plugin (see previous section).

How can I implement my own injector or extractor?

An injection/extraction is a transformation from/to another Technical Space (e.g., XML, Grammarware) to/from the Model Engineering Technical Space. An injector/extractor is a component implementing an injection/extraction.

Injectors and extractors may be then used programmatically or via ATL-specific ANT tasks atl.loadModel and atl.saveModel.

To be usable in practice, an injector/extractor must implement the IInjector/IExtractor interface (cf. ATL Core API documentation), as shown by the XML injector/extractor example for instance. It must also declare explicitly the use of the specific org.eclipse.m2m.atl.core.injector/extractor extension points, as shown by the same example than before.

How can I transform UML models?

There are several implementations of UML. The one we consider here is the de-facto standard implementation from Eclipse: the UML2 project.

ATL allows to transform such UML models as any other EMF models.

The UML2 metamodel must be loaded from the EMF registry (i.e., by namespace URI). This can be done using the "EMF Registry..." button of the ATL launch configuration, or using the nsURI attribute of the atl.loadModel task.

Usage of content assist (i.e., code completion) is especially useful with big metamodels like UML2.

How can I retrieve tagged values from stereotyped UML model elements?

In ATL, a profiled UML model used as source model is viewed like any other UML model. You generally (i.e., when the profile is referenced with a valid relative path) do not have to specify the profile used with the model. So, in the header of the ATL module you just have:

module uml2something;
create OUT : targetMetamodel from IN : UML;

If atl seems to ignore your stereotypes, you can add your profile as source model. You obtain the following header:

module uml2something;
create OUT : targetMetamodel from IN : UML, INPROFILE : profile;

After that you can use operations like:

  • getAppliedStereotype(sterotypeName : String) on a UML element to get the stereotype with the name "stereotypeName" applied on this element. This operation needs the fully qualifed name of the stereotype so it looks like: profileName::sterotypeName.
  • getValue(stereotype : Stereotype, propertyName : String) to get the Value of the tagged value with name "propertyName" on the stereotype "stereotype" (the sterotype can be retrieved by getAppliedStereotype).

A helper like:

helper context UML!Element def: hasStereotype(name : String) : Boolean =
	not self.getAppliedStereotype(name).oclIsUndefined();

can also be useful to check if a stereotype is applied on the UML element before trying to retrieve it or to get a tagged value from it. As it uses getAppliedStereotype, it needs the fully qualified name of the stereotype (e.g., profileName::sterotypeName).

How can I specify a Virtual Machine operation in Java? (Deprecated)

It is possible to add new Java operations to the ATL Virtual Machine (VM). These operations can then be called like helpers.

The org.eclipse.gmt.atl.oclquery.core plugin offers the org.eclipse.gmt.atl.oclquery.core.ATLVMTools class to create instances of org.atl.engine.vm.Operation and to register them in the ATL VM.

This is used in org.eclipse.gmt.atl.oclquery.core.OclEvaluator to redefine the dumpASM method of ASMEmitter. The process to register operations on OCL primitive types (e.g. Boolean, Integer, String) is similar.

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