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Difference between revisions of "ATL/Developer Guide"

< ATL
(ATL Core API)
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[[Category:ATL]]
 
[[Category:ATL]]
= Introduction =
+
This documentation aims at contributing to improve the comprehension of the ATL source code.
This documentation aims at contributing to the comprehension of the ATL source code.
+
  
= ATL Plugins =
+
= ATL Source Code =
 +
 
 +
== Plug-ins organization ==
  
== Overview ==
 
 
Below is the list of the [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/?root=Modeling_Project ATL plugins]:
 
Below is the list of the [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/?root=Modeling_Project ATL plugins]:
 
*'''ATL Core''': provides APIs to launch and extend ATL
 
*'''ATL Core''': provides APIs to launch and extend ATL
Line 32: Line 32:
  
 
== External dependencies ==
 
== External dependencies ==
 
=== ATL ===
 
  
 
Historically, ATL imports two libraries : ANTLR version 2 and MDR. Those libraries are not authorized in Eclipse because of their non-compliance with the Eclipse IP policy. Consequently, ATL imposes users to download those libraries by themselves and install them into Eclipse plugin folder.
 
Historically, ATL imports two libraries : ANTLR version 2 and MDR. Those libraries are not authorized in Eclipse because of their non-compliance with the Eclipse IP policy. Consequently, ATL imposes users to download those libraries by themselves and install them into Eclipse plugin folder.
  
 
Today, ATL dependencies have been strongly reduced : ATL only needs ANTLR-runtime (version 3) library, which is compliant with the Eclipse IP policy and included into ATL source code. The MDR library is only necessary for the MDR Model Handler. According to the fact that most of people uses EMF Model Handler (which seems to be more powerful), MDR Model Handler has been separated into a single feature, which is not natively required for ATL.
 
Today, ATL dependencies have been strongly reduced : ATL only needs ANTLR-runtime (version 3) library, which is compliant with the Eclipse IP policy and included into ATL source code. The MDR library is only necessary for the MDR Model Handler. According to the fact that most of people uses EMF Model Handler (which seems to be more powerful), MDR Model Handler has been separated into a single feature, which is not natively required for ATL.
 
=== Other tools ===
 
  
 
[http://wiki.eclipse.org/TCS TCS (Textual Concrete Syntax)], a tool for parsing and extraction, is used to generate some ATL components (e.g. ATL-Parser). Unlike ATL, TCS uses both ANTLR library, in version 2 and newly in version 3. TCS is available on [http://www.eclipse.org/gmt/ GMT]. ATL doesn't have any dependency with TCS. Specific injectors depend on ANTLR too.
 
[http://wiki.eclipse.org/TCS TCS (Textual Concrete Syntax)], a tool for parsing and extraction, is used to generate some ATL components (e.g. ATL-Parser). Unlike ATL, TCS uses both ANTLR library, in version 2 and newly in version 3. TCS is available on [http://www.eclipse.org/gmt/ GMT]. ATL doesn't have any dependency with TCS. Specific injectors depend on ANTLR too.
  
= ATL Language =
+
== Install ATL from CVS ==
  
== Overview ==
+
=== Import team project set ===
 +
ATL provides team project sets in order to simplify access to the source code. You have to download an atl.psf file on your local disk, and then you can import projects in Eclipse using : ''File->Import->Team->Team Project Set''
  
ATL language which can be split into two parts :
+
==== Anonymous access ====
* declarative : matched rules, and called rules body. The main use of ATL is declarative. Imperative part should only be used in specific cases.
+
Anonymous access use pserver to connect on CVS. [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl.releng/psf/anonymous/?root=Modeling_Project Here] are the two psf files.
* imperative : called rules (imperatively called), and action blocks ("do", usable in any rules)
+
Specifics uses of those parts are described in the [http://wiki.eclipse.org/ATL_Language_Troubleshooter ATL Language Troubleshooter] section.
+
  
ATL architecture is composed of four main components :
+
==== Commiter access ====
* ATL Editor
+
Commiter access use extssh to connect on CVS. [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl.releng/psf/commiter/?root=Modeling_Project Here] are the two psf files.
* [[#Parsing and Compilation | ATL Compiler]]
+
* [[#ATL VM | ATL VM]]
+
* [[#Model Handlers | Model handlers]]
+
  
ATL VM is intercalated between the ATL compiler and the used frameworks (EMF, MDR), allowing modularity. Consequently, changes on ATL Language only involve ATL compiler.
+
==== ANTLR installation ====
The following schema describes ATL components and their role during the execution of a transformation.
+
Note that the download of this plugin is embedded into atl.psf files. So, if you followed the previous instructions, you don't need to read the next steps.
 +
In Eclipse, antlr is managed by the [http://www.eclipse.org/orbit/ Orbit] project. To checkout this plugin, follow those steps :
 +
* Open an anonymous/commiter CVS connection to <code>dev.eclipse.org</code>, repository <code>/cvsroot/tools</code>
 +
* Right-click on the repository location, then choose ''Refresh branches''
 +
* In the wizard, check the <code>org.eclipse.orbit</code> project
 +
* In the branches, select the one named <code>v3_0_0</code>
 +
* Checkout <code>org.antlr.runtime</code>
  
[[Image:ATL_compilation_process.JPG]]
+
==== MDR installation (Regular VM only) ====
 +
In each psf/ subdirectory there are two .psf files :
 +
* atl.psf
 +
* mdr4atl.psf
 +
The last one provides a project set which only contains the mdr4atl driver, you can use it as for atl.psf.
  
== Parsing and Compilation ==
+
Now, you need to go to the Plug-in perspective. Some external libraries are required for the plug-in org.eclipse.m2m.atl.drivers.mdr4atl but not available on the CVS repository. You need to download the jar files into the lib/ directory of this project.
  
ATL parsing is done using a parser defined in TCS, which outputs an ATL model conforming to the ATL metamodel. Then, an ATL-WFR transformation (interpreted by the engine) generates a problem model. This model produces errors interpreted by the editor and translated into markers, visible on the ATL file on each compilation.
+
Download mdr-standalone.zip from http://mdr.netbeans.org/download/ and put the included jar files into lib/ of plugin org.eclipse.m2m.atl.drivers.mdr4atl.
  
Two versions of the ATL compiler are available : 2004 and [http://wiki.eclipse.org/ATL_2006 2006].
+
Note that mdr-standalone.zip is updated more often on the MDR website than in our development source. As a consequence, bugs may appear when using the last-in-date mdr-standalone version of MDR.
The 2006 version of ATL compiler uses [[#ACG_.28ATL_VM_Code_Generator.29|ACG]]. The 2004 version uses ATP, the historical ACG predecessor.
+
  
== Debugger ==
+
When you have finished this operation, there is normally no error left.
  
The ATL Debugger provides tools to support profiling, debugging, etc... of ATL applications. It can be compared to the [http://java.sun.com/javase/6/docs/technotes/guides/jvmti/ JVM TI].
+
WARNING: The MDR model handler is no more maintained, so it may need to be fixed.
  
In ATL, three debuggers are implemented :
+
==== Testing ====
*DummyDebugger : a dummy class implementing the debugger interface without doing anything.
+
ATL is ready to be tested. There are two ways to use it:
*SimpleDebugger
+
* In the "Plug-in Development perspective", you can launch a Run-time workbench (Click on Run -> Run as -> Run-time workbench).
*NetworkDebugger
+
* You can install ATL in your copy of Eclipse. Go in the Plug-in perspective and select all the plug-in projects. In the context menu choose Export -> Deployable Plug-ins and Fragments.
  
In the ATL VM code, debugger entry points are located into exec methods of operations, materialized by "step" method calls.
+
In the screen Export Plug-ins and Fragments, check if all the projects are selected and choose the output folder.
  
=== SimpleDebugger ===
+
Now you need to close Eclipse. Enter the "eclipse" directory (which contains plug-ins and features directories) then copy the created Jar files into the "plugins" directory. After that you can restart Eclipse.
  
The simple debugger is the default ATL debugger : it displays in Eclipse's console the informations traced by the ATL VM during the execution.
+
ATL Architecture =
A "very verbose" option allows to display all possible informations traced by the ATL VM frames, intending to debug the ATL VM. Many options are available, for example :
+
* step : stop point  at every [[#ASM_format bytecode]] instruction
+
* stepops : list of operations for which we want to display bytecode
+
* deepstepops : same than stepops, also including sub-called operations
+
  
=== NetworkDebugger ===
+
The ATL architecture consists on:
 +
* a [[#Core | Core]], which describes ATL concepts in an abstract way
 +
* a [[#Parser | Parser]] and a [[#Compiler | Compiler]]
 +
* [[#ATL_Virtual_Machines | Virtual Machines]], allowing to execute transformations
 +
* an IDE: editor, debugger, perspective, all based on previous components
  
The network debugger is the main debugger of ATL, integrated to Eclipse's debug perspective. It uses ADWP, a TCP debugger inspired on JDWP (the java debugger). All debug informations are sent on a TCP port by the executed program (Local). Those informations are received and computed by the debugger (Remote), implemented in the org.eclipse.m2m.atl.adt.debug plugin.
+
The following schema describes ATL components and their role during the execution of a transformation.
 +
 
 +
[[Image:ATL_compilation_process.JPG]]
 +
 
 +
ATL VM is intercalated between the ATL compiler and the used frameworks (EMF, MDR), allowing modularity. Consequently, changes on ATL Language only involve ATL compiler.
 +
 
 +
== Core ==
 +
 
 +
This schema describes the ATL Core and how it interacts with tools like LaunchConfigurations, Ant tasks.  
 +
 
 +
[[Image:ATL_Core_Architecture.png]]
 +
 
 +
* An [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/IModel.java?root=Modeling_Project&view=markup IModel] is an adapted representation of a model, suitable for ATL transformations. It provides methods to lookup elements, create new ones, etc...
 +
* The [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/IReferenceModel.java?root=Modeling_Project&view=markup IReferenceModel] interface extends the IModel one, and is a specific version of an IModel which symbolizes metamodels. It defines metamodel-specific operations which are useful for ATL transformations
 +
* The [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/ModelFactory.java?root=Modeling_Project&view=markup ModelFactory] is dedicated for model and reference model creation
 +
* The [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/IInjector.java?root=Modeling_Project&view=markup IInjector], [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/IExtractor.java?root=Modeling_Project&view=markup IExtractor] interfaces provide a way to load and save models previously created by the modelFactory
 +
* The [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/launch/ILauncher.java?root=Modeling_Project&view=markup ILauncher] interface is dedicated to be implemented by ATL virtual machines: it defines methods to parametrize and launch a transformation
 +
 
 +
=== Services ===
 +
 
 +
To simplify the use of ATL Core and reduce code duplication, two services are provided: [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/service/CoreService.java?root=Modeling_Project&view=markup CoreService] and [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core/src/org/eclipse/m2m/atl/core/service/LauncherService.java?root=Modeling_Project&view=log LauncherService].
 +
 
 +
==== CoreService ====
  
The disassembly mode allows to debug the bytecode, without ATL source code, and make easier to debug the ATL VM.
+
This utility class provide a way to lookup into eclipse extensions, or an internal storage, for Core implementations. Those implementations can be registered into the CoreService for a standalone use. For instance, here we register the extensions needed to launch a transformation using EMF-specific VM, in standalone:
 +
CoreService.registerLauncher(new EMFVMLauncher());
 +
CoreService.registerFactory("EMF", EMFModelFactory.class);
 +
CoreService.registerExtractor("EMF", new EMFExtractor());
 +
CoreService.registerInjector("EMF", new EMFInjector());
  
= ATL Core API =
+
==== LauncherService ====
  
''TODO: improve ATL 3.0 core API documentation''
+
The launcher service allow to launch a transformation from a set of parameters like maps of path and maps of model names: this is strongly related to launch configurations and ant tasks as it allows to launch the transformation on any virtual machine.  
  
== EMFInjector / EMFExtractor usage ==
+
=== EMF interactions ===
  
This section shows how to use ATL EMF-specific injector/extractor. For both, we use the EMF notation to select Resources:
+
The main implementation of the ATL Core is the EMF one, which is used by ATL itself for parsing and compilation. It is defined under the [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.core.emf/?root=Modeling_Project org.eclipse.m2m.atl.core.emf] plugin.
  
 +
Here is an explanation about the use ATL EMF-specific injector/extractor. For both, we use the EMF notation to select Resources:
 
{| border="1"
 
{| border="1"
 
! Resource Type !! ATL EMF API Syntax !! Example
 
! Resource Type !! ATL EMF API Syntax !! Example
Line 130: Line 158:
 
  injector.inject(sampleMetamodel, "file:/D:/eclipse/workspace/mmproject/sample_metamodel.ecore");
 
  injector.inject(sampleMetamodel, "file:/D:/eclipse/workspace/mmproject/sample_metamodel.ecore");
  
= ACG (ATL VM Code Generator) =
+
== ATL Virtual Machines ==
  
== Description ==
+
The ATL VM is a [[#ASM format | byte code interpreter]] which manages OCL and ATL types hierarchy. A complete ATL VM specification is available : [http://www.eclipse.org/m2m/atl/doc/ATL_VMSpecification%5Bv00.01%5D.pdf ATL_VMSpecification]. This specification consists on a precise description of the ATL VM functionalities, but doesn't describe the implementation. The intent is to allow any developer to create an ATL VM in any language.
 +
The [http://wiki.eclipse.org/ATL_Standard_Library Native Library] (org.eclipse.m2m.atl.engine.vm.nativelib package) gathers all basic type definitions used by the ATL VM : OCL types and ATL specific types. Both are defined at the same level, and use reflexion.
 +
OCL appears at several levels in the ATL architecture :
 +
* nativelib implementation
 +
* OCL package in the ATL, ACG and TCS metamodels
  
ACG is a compiler-oriented DSL, which intends to make easier to create a compiler targeting the [[#ATL_VM|ATL VM]]. A compiler described with ACG generates ASM files and contains a description of ASM instructions to generate for each type of input elements, coming from a compiled file. Therefore the input of this kind of compiler is a model describing the content of a compiled file (for instance, an ATL file).
+
The following schema shows the ATL VM working:
 
+
An ACG file, when compiled, looks through the input model using a visitor design pattern.
+
ACG is bootstrapped : an ACG.acg file exists and describes the ACG compiler. Since an ACG file describes precisely ASM instructions, the ACG.acg file is rather trivial.
+
 
+
A complete ACG documentation is available [http://wiki.eclipse.org/ACG here].
+
 
+
== ACG in AMMA platform ==
+
 
+
The following schema places ACG in the AMMA platform.
+
 
+
[[Image:AMMA_bootstrap.JPG]]
+
 
+
= ATL VM =
+
 
+
The ATL VM is a byte code interpreter which manages OCL and ATL types hierarchy and the model handler abstract layer. A complete ATL VM specification is available : [http://www.eclipse.org/m2m/atl/doc/ATL_VMSpecification%5Bv00.01%5D.pdf ATL_VMSpecification].
+
 
+
This specification consists on a precise description of the ATL VM functionalities, but doesn't describe the implementation. The intent is to allow any developer to create an ATL VM in any language.
+
This section attends to describe the ATL Regular VM implementation.
+
 
+
== Launching ==
+
 
+
Several classes can launch the ATL VM, with different goals :
+
* The ASMInterpreter class launches the ATL VM. The realMain method is used to launch ATL VM in command line.
+
* The ASMProjector class is only defined to launch injections, extractions, or both without launching any transformation.
+
* The ASMEngine class is the real ATL VM command-line launcher that dispatches to ASMInterpreter, ASMProjector, or ACTInterpreter, depending on the arguments.
+
* The ACTInterpreter class is now unused and was historically used to launch ATL VM with ant-like scripts. It depends on XMLInjector. Thus, for coding facilities, this class is located into the ATL VM. For a coherence purpose, XMLExtractor is also located into the ATL VM. However the associated extension points are defined in the engine plugin.
+
 
+
During ATL VM initialization, every operations are registered into a Map. The following schema explains ASMInterpreter functionment :
+
  
 
[[Image:ATL_ASMInterpreter.JPG]]
 
[[Image:ATL_ASMInterpreter.JPG]]
  
== Execution ==
+
During ATL VM initialization, every operations are registered into a Map. The ExecEnv Class contains the virtual execution environment. It deals with the operation map which registers all operations used by the transformation. It contains every information used by a given execution, like models,  and is recreated for each execution. Operations are executed sequentially, into frames, according to their type. For instance, in ATL, a call of the append() method is directly mapped to a call to the corresponding method in the ASMSequence class.
  
The ExecEnv Class contains the virtual execution environment. It deals with the operation map which registers all operations used by the transformation. It contains every information used by a given execution, like models,  and is recreated for each execution.
 
Operations are executed sequentially, into frames, according to their type. For instance, in ATL, a call of the append() method is directly mapped to a call to the corresponding method in the ASMSequence class.
 
 
The Frame stores and throws all error messages. The ASMStackFrame is dedicated to ASM methods, when the StackFrame is dedicated to native methods.
 
The Frame stores and throws all error messages. The ASMStackFrame is dedicated to ASM methods, when the StackFrame is dedicated to native methods.
 
Execution errors come from ATL VM when the method Frame.printstacktrace is called.
 
Execution errors come from ATL VM when the method Frame.printstacktrace is called.
  
== Native Library ==
+
At this time there are two implementations of the ATL VM.
  
The [http://wiki.eclipse.org/ATL_Standard_Library Native Library] (org.eclipse.m2m.atl.engine.vm.nativelib package) gathers all basic type definitions used by the ATL VM : OCL types and ATL specific types. Both are defined at the same level, and use reflexion.
+
=== Regular VM ===
OCL appears at several levels in the ATL architecture :
+
* nativelib implementation
+
* OCL package in the ATL, ACG and TCS metamodels
+
  
== Model Handlers ==
+
The Regular VM is the first version of the ATL Virtual Machine. The implementation is abstracted from the used model management framework, using model handlers. Model Handlers consists on an abstraction layer dedicated to model access. This access is implemented by two classes : ASMModel et ASMModelElement.
  
Model Handlers consists on an abstraction layer dedicated to model access. This access is implemented by two classes : ASMModel et ASMModelElement.
+
ATL contains three plugins drivers corresponding to different Model Handlers : EMF, MDR, UML2. Each plugin implements those abstract classes :
 
+
Input and output models are loaded using the same API and are differenciated with an "isTarget" property. That API implements the "getMetaElementsByName" method which correspond to the "findme" ASM instruction.
+
 
+
ATL contains three plugins drivers corresponding to different Model Handlers : EMF, MDR, UML2.
+
Each plugin implements those abstract classes :
+
 
* AtlModelHandler : implementation of the basic tasks "newModel", "saveModel", "loadModel"
 
* AtlModelHandler : implementation of the basic tasks "newModel", "saveModel", "loadModel"
 
* ASMModel : getElementsByType implementation, framework oriented "newModelElement" method, etc...
 
* ASMModel : getElementsByType implementation, framework oriented "newModelElement" method, etc...
 
* ASMModelElement : "allInstances" implementation, etc...
 
* ASMModelElement : "allInstances" implementation, etc...
  
The EMF4ATL is a particular case which doesn't contain the ModelHandler, which is placed in the org.eclipse.m2m.atl.engine plugin to facilitate implementation.
+
Input and output models are loaded using the same API and are differenciated with an "isTarget" property. That API implements the "getMetaElementsByName" method which correspond to the "findme" ASM instruction.
  
= ASM format =
+
This VM implementation is still used in ATL, because it is strongly linked to several parts (now only the ATL Debugger). But the Regular VM has a lot of performance issues, especially because of the model handler architecture.
  
== Description ==
+
=== EMF-specific VM ===
  
ASM language is a kind of assembly language, adapted to model handling. The low level of ASM allows modularity facilities, with the intent to provide easier model management possibilities.
+
The EMF-specific VM is a redefinition of the Regular one, which resolves a lot of performance issues by avoiding EObjects wrapping. Its API allow to consider EMF Resources directly as models, without complex loading as done previously in the Regular VM.
 +
 
 +
=== ASM format ===
 +
 
 +
ASM language is a kind of assembly language, adapted to model handling. The low level of ASM allows modularity facilities, with the intent to provide easier model management possibilities.
 
The current file format for ASM is XML. Thus it allows not to care about any syntax and to only focus on bytecode.
 
The current file format for ASM is XML. Thus it allows not to care about any syntax and to only focus on bytecode.
 
An ASM file only contains names and string constants. No Ecore reference is present. Those are resolved by launch configurations and AMMA Megamodel, with a name binding.
 
An ASM file only contains names and string constants. No Ecore reference is present. Those are resolved by launch configurations and AMMA Megamodel, with a name binding.
  
== Serialization ==
+
==== Serialization ====
  
 
ASM transformations are serialized in a way to increase performance and preempt further serializations like binary files.
 
ASM transformations are serialized in a way to increase performance and preempt further serializations like binary files.
Line 208: Line 206:
 
ASMWriter is the parent abstract class which allows a binary implementation of ASM injection and extraction.
 
ASMWriter is the parent abstract class which allows a binary implementation of ASM injection and extraction.
  
== Instructions ==
+
==== Instructions ====
  
 
All instructions are explained into ATL VM specification. Here are details about some of them:
 
All instructions are explained into ATL VM specification. Here are details about some of them:
Line 220: Line 218:
 
** A delete instruction could be implemented in the ATL VM
 
** A delete instruction could be implemented in the ATL VM
 
** ATL provides the newInstance method which is directly mapped to the Model Handler method. This method doesn't generates a new because the call is dynamic. The main advantage is that the newInstance is directly applied to the class and do not use the ATL VM stack for that (otherwise it should store the class element).
 
** ATL provides the newInstance method which is directly mapped to the Model Handler method. This method doesn't generates a new because the call is dynamic. The main advantage is that the newInstance is directly applied to the class and do not use the ATL VM stack for that (otherwise it should store the class element).
 +
 +
== Parser ==
 +
 +
ATL parsing is done using a parser defined in TCS, which outputs an ATL model conforming to the ATL metamodel. Then, an ATL-WFR transformation (interpreted by the engine) generates a problem model. This model produces errors interpreted by the editor and translated into markers, visible on the ATL file on each compilation.
 +
 +
To manually parse (or extract) ATL files, see the [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.engine/src/org/eclipse/m2m/atl/engine/parser/AtlParser.java?root=Modeling_Project&view=markup ATLParser] class.
 +
 +
Note that as ATL parser implements IInjector and IExtractor interfaces, it can be use in ant tasks to parse or extract atl files (just specify "ATL" as injector/extractor name).
 +
 +
== Compiler ==
 +
 +
Two versions of the ATL compiler are available : 2004 and [http://wiki.eclipse.org/ATL_2006 2006].
 +
The 2006 version of ATL compiler uses [[#ACG_.28ATL_VM_Code_Generator.29|ACG]]. The 2004 version uses ATP, the historical ACG predecessor.
 +
 +
To manually compile ATL files, see the [http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.m2m/org.eclipse.m2m.atl/plugins/org.eclipse.m2m.atl.engine/src/org/eclipse/m2m/atl/engine/compiler/AtlDefaultCompiler.java?root=Modeling_Project&view=markup AtlDefaultCompiler] class.
 +
 +
=== ACG (ATL VM Code Generator) ===
 +
 +
ACG is a compiler-oriented DSL, which intends to make easier to create a compiler targeting the [[#ATL_VM|ATL VM]]. A compiler described with ACG generates ASM files and contains a description of ASM instructions to generate for each type of input elements, coming from a compiled file. Therefore the input of this kind of compiler is a model describing the content of a compiled file (for instance, an ATL file).
 +
 +
An ACG file, when compiled, looks through the input model using a visitor design pattern.
 +
ACG is bootstrapped : an ACG.acg file exists and describes the ACG compiler. Since an ACG file describes precisely ASM instructions, the ACG.acg file is rather trivial.
 +
 +
A complete ACG documentation is available [http://wiki.eclipse.org/ACG here].
 +
 +
The following schema places ACG in the AMMA platform.
 +
 +
[[Image:AMMA_bootstrap.JPG]]

Revision as of 11:08, 2 June 2009

This documentation aims at contributing to improve the comprehension of the ATL source code.

ATL Source Code

Plug-ins organization

Below is the list of the ATL plugins:

External dependencies

Historically, ATL imports two libraries : ANTLR version 2 and MDR. Those libraries are not authorized in Eclipse because of their non-compliance with the Eclipse IP policy. Consequently, ATL imposes users to download those libraries by themselves and install them into Eclipse plugin folder.

Today, ATL dependencies have been strongly reduced : ATL only needs ANTLR-runtime (version 3) library, which is compliant with the Eclipse IP policy and included into ATL source code. The MDR library is only necessary for the MDR Model Handler. According to the fact that most of people uses EMF Model Handler (which seems to be more powerful), MDR Model Handler has been separated into a single feature, which is not natively required for ATL.

TCS (Textual Concrete Syntax), a tool for parsing and extraction, is used to generate some ATL components (e.g. ATL-Parser). Unlike ATL, TCS uses both ANTLR library, in version 2 and newly in version 3. TCS is available on GMT. ATL doesn't have any dependency with TCS. Specific injectors depend on ANTLR too.

Install ATL from CVS

Import team project set

ATL provides team project sets in order to simplify access to the source code. You have to download an atl.psf file on your local disk, and then you can import projects in Eclipse using : File->Import->Team->Team Project Set

Anonymous access

Anonymous access use pserver to connect on CVS. Here are the two psf files.

Commiter access

Commiter access use extssh to connect on CVS. Here are the two psf files.

ANTLR installation

Note that the download of this plugin is embedded into atl.psf files. So, if you followed the previous instructions, you don't need to read the next steps. In Eclipse, antlr is managed by the Orbit project. To checkout this plugin, follow those steps :

  • Open an anonymous/commiter CVS connection to dev.eclipse.org, repository /cvsroot/tools
  • Right-click on the repository location, then choose Refresh branches
  • In the wizard, check the org.eclipse.orbit project
  • In the branches, select the one named v3_0_0
  • Checkout org.antlr.runtime

MDR installation (Regular VM only)

In each psf/ subdirectory there are two .psf files :

  • atl.psf
  • mdr4atl.psf

The last one provides a project set which only contains the mdr4atl driver, you can use it as for atl.psf.

Now, you need to go to the Plug-in perspective. Some external libraries are required for the plug-in org.eclipse.m2m.atl.drivers.mdr4atl but not available on the CVS repository. You need to download the jar files into the lib/ directory of this project.

Download mdr-standalone.zip from http://mdr.netbeans.org/download/ and put the included jar files into lib/ of plugin org.eclipse.m2m.atl.drivers.mdr4atl.

Note that mdr-standalone.zip is updated more often on the MDR website than in our development source. As a consequence, bugs may appear when using the last-in-date mdr-standalone version of MDR.

When you have finished this operation, there is normally no error left.

WARNING: The MDR model handler is no more maintained, so it may need to be fixed.

Testing

ATL is ready to be tested. There are two ways to use it:

  • In the "Plug-in Development perspective", you can launch a Run-time workbench (Click on Run -> Run as -> Run-time workbench).
  • You can install ATL in your copy of Eclipse. Go in the Plug-in perspective and select all the plug-in projects. In the context menu choose Export -> Deployable Plug-ins and Fragments.

In the screen Export Plug-ins and Fragments, check if all the projects are selected and choose the output folder.

Now you need to close Eclipse. Enter the "eclipse" directory (which contains plug-ins and features directories) then copy the created Jar files into the "plugins" directory. After that you can restart Eclipse.

ATL Architecture

The ATL architecture consists on:

  • a Core, which describes ATL concepts in an abstract way
  • a Parser and a Compiler
  • Virtual Machines, allowing to execute transformations
  • an IDE: editor, debugger, perspective, all based on previous components

The following schema describes ATL components and their role during the execution of a transformation.

ATL compilation process.JPG

ATL VM is intercalated between the ATL compiler and the used frameworks (EMF, MDR), allowing modularity. Consequently, changes on ATL Language only involve ATL compiler.

Core

This schema describes the ATL Core and how it interacts with tools like LaunchConfigurations, Ant tasks.

ATL Core Architecture.png

  • An IModel is an adapted representation of a model, suitable for ATL transformations. It provides methods to lookup elements, create new ones, etc...
  • The IReferenceModel interface extends the IModel one, and is a specific version of an IModel which symbolizes metamodels. It defines metamodel-specific operations which are useful for ATL transformations
  • The ModelFactory is dedicated for model and reference model creation
  • The IInjector, IExtractor interfaces provide a way to load and save models previously created by the modelFactory
  • The ILauncher interface is dedicated to be implemented by ATL virtual machines: it defines methods to parametrize and launch a transformation

Services

To simplify the use of ATL Core and reduce code duplication, two services are provided: CoreService and LauncherService.

CoreService

This utility class provide a way to lookup into eclipse extensions, or an internal storage, for Core implementations. Those implementations can be registered into the CoreService for a standalone use. For instance, here we register the extensions needed to launch a transformation using EMF-specific VM, in standalone:

CoreService.registerLauncher(new EMFVMLauncher());
CoreService.registerFactory("EMF", EMFModelFactory.class); 
CoreService.registerExtractor("EMF", new EMFExtractor());
CoreService.registerInjector("EMF", new EMFInjector()); 

LauncherService

The launcher service allow to launch a transformation from a set of parameters like maps of path and maps of model names: this is strongly related to launch configurations and ant tasks as it allows to launch the transformation on any virtual machine.

EMF interactions

The main implementation of the ATL Core is the EMF one, which is used by ATL itself for parsing and compilation. It is defined under the org.eclipse.m2m.atl.core.emf plugin.

Here is an explanation about the use ATL EMF-specific injector/extractor. For both, we use the EMF notation to select Resources:

Resource Type ATL EMF API Syntax Example
File system Resource file:/<path> file:/D:/eclipse/workspace/mmproject/sample_metamodel.ecore
EMF uri <uri> http://www.eclipse.org/uml2/2.1.0/UML
pathmap pathmap:<path> pathmap://PROFILE/sample_profile.uml#_0
Workspace Resource platform:/resource/<path> platform:/resource/mmproject/sample_metamodel.ecore
Plug-in Resource platform:/plugin/<path> platform:/plugin/mmproject/sample_metamodel.ecore

Here is an example of usage:

ModelFactory factory = CoreService.createModelFactory("EMF");
IReferenceModel umlMetamodel = factory.newReferenceModel();
injector.inject(umlMetamodel, "http://www.eclipse.org/uml2/2.1.0/UML");

According to the previous table, you can use another notation to load the model:

injector.inject(sampleMetamodel, "file:/D:/eclipse/workspace/mmproject/sample_metamodel.ecore");

ATL Virtual Machines

The ATL VM is a byte code interpreter which manages OCL and ATL types hierarchy. A complete ATL VM specification is available : ATL_VMSpecification. This specification consists on a precise description of the ATL VM functionalities, but doesn't describe the implementation. The intent is to allow any developer to create an ATL VM in any language. The Native Library (org.eclipse.m2m.atl.engine.vm.nativelib package) gathers all basic type definitions used by the ATL VM : OCL types and ATL specific types. Both are defined at the same level, and use reflexion. OCL appears at several levels in the ATL architecture :

  • nativelib implementation
  • OCL package in the ATL, ACG and TCS metamodels

The following schema shows the ATL VM working:

ATL ASMInterpreter.JPG

During ATL VM initialization, every operations are registered into a Map. The ExecEnv Class contains the virtual execution environment. It deals with the operation map which registers all operations used by the transformation. It contains every information used by a given execution, like models, and is recreated for each execution. Operations are executed sequentially, into frames, according to their type. For instance, in ATL, a call of the append() method is directly mapped to a call to the corresponding method in the ASMSequence class.

The Frame stores and throws all error messages. The ASMStackFrame is dedicated to ASM methods, when the StackFrame is dedicated to native methods. Execution errors come from ATL VM when the method Frame.printstacktrace is called.

At this time there are two implementations of the ATL VM.

Regular VM

The Regular VM is the first version of the ATL Virtual Machine. The implementation is abstracted from the used model management framework, using model handlers. Model Handlers consists on an abstraction layer dedicated to model access. This access is implemented by two classes : ASMModel et ASMModelElement.

ATL contains three plugins drivers corresponding to different Model Handlers : EMF, MDR, UML2. Each plugin implements those abstract classes :

  • AtlModelHandler : implementation of the basic tasks "newModel", "saveModel", "loadModel"
  • ASMModel : getElementsByType implementation, framework oriented "newModelElement" method, etc...
  • ASMModelElement : "allInstances" implementation, etc...

Input and output models are loaded using the same API and are differenciated with an "isTarget" property. That API implements the "getMetaElementsByName" method which correspond to the "findme" ASM instruction.

This VM implementation is still used in ATL, because it is strongly linked to several parts (now only the ATL Debugger). But the Regular VM has a lot of performance issues, especially because of the model handler architecture.

EMF-specific VM

The EMF-specific VM is a redefinition of the Regular one, which resolves a lot of performance issues by avoiding EObjects wrapping. Its API allow to consider EMF Resources directly as models, without complex loading as done previously in the Regular VM.

ASM format

ASM language is a kind of assembly language, adapted to model handling. The low level of ASM allows modularity facilities, with the intent to provide easier model management possibilities. The current file format for ASM is XML. Thus it allows not to care about any syntax and to only focus on bytecode. An ASM file only contains names and string constants. No Ecore reference is present. Those are resolved by launch configurations and AMMA Megamodel, with a name binding.

Serialization

ASM transformations are serialized in a way to increase performance and preempt further serializations like binary files. The ASMXMLWriter class is an ASM extractor used to save ASM into a file. Serialization computes the constant pool, which factorizes constants, values and method calls by generating an ordered constants list at the top of the ASM file. ASMWriter is the parent abstract class which allows a binary implementation of ASM injection and extraction.

Instructions

All instructions are explained into ATL VM specification. Here are details about some of them:

  • The getasm instruction retrieves the ATL Context Module, i.e. The "thisModule" equivalent for ATL.
  • N symbolizes a native type, ATL specific
  • TransientLink are traceability links
  • all functions like "getLinkBySourceElement" are implemented in the nativelib
  • Object creation :
    • The "new" instruction takes two parameters : the metamodel name and the classifier type. Then it creates an element of this type in the output model (only one is allowed). The parameters are not available in the bytecode because they are pushed on the stack before calling instruction.
    • We can notice that ATL allows only one output model, but the ATL VM could be extended two allow many others.
    • A delete instruction could be implemented in the ATL VM
    • ATL provides the newInstance method which is directly mapped to the Model Handler method. This method doesn't generates a new because the call is dynamic. The main advantage is that the newInstance is directly applied to the class and do not use the ATL VM stack for that (otherwise it should store the class element).

Parser

ATL parsing is done using a parser defined in TCS, which outputs an ATL model conforming to the ATL metamodel. Then, an ATL-WFR transformation (interpreted by the engine) generates a problem model. This model produces errors interpreted by the editor and translated into markers, visible on the ATL file on each compilation.

To manually parse (or extract) ATL files, see the ATLParser class.

Note that as ATL parser implements IInjector and IExtractor interfaces, it can be use in ant tasks to parse or extract atl files (just specify "ATL" as injector/extractor name).

Compiler

Two versions of the ATL compiler are available : 2004 and 2006. The 2006 version of ATL compiler uses ACG. The 2004 version uses ATP, the historical ACG predecessor.

To manually compile ATL files, see the AtlDefaultCompiler class.

ACG (ATL VM Code Generator)

ACG is a compiler-oriented DSL, which intends to make easier to create a compiler targeting the ATL VM. A compiler described with ACG generates ASM files and contains a description of ASM instructions to generate for each type of input elements, coming from a compiled file. Therefore the input of this kind of compiler is a model describing the content of a compiled file (for instance, an ATL file).

An ACG file, when compiled, looks through the input model using a visitor design pattern. ACG is bootstrapped : an ACG.acg file exists and describes the ACG compiler. Since an ACG file describes precisely ASM instructions, the ACG.acg file is rather trivial.

A complete ACG documentation is available here.

The following schema places ACG in the AMMA platform.

AMMA bootstrap.JPG

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