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Home » Modeling » TMF (Xtext) » Naming and Containment Hierarchy Issue
Naming and Containment Hierarchy Issue [message #730141] Tue, 27 September 2011 17:27 Go to next message
steven reinisch is currently offline steven reinischFriend
Messages: 33
Registered: July 2009
hi folks,

I have an external ecore meta model for which I created two grammars.
The meta model looks like this:

System <>---*- Module <>---1- InterfaceModel <>---*- Interface

A System consists of modules. Each module has one InterfaceModel which in turn has multiple Interfaces. (A diamond (<>) denotes a containment reference.)

The creation of models is splitted up into two DSLs - a system DSL and an interface DSL. With the system DSL only the availbale modules should be listed. Its grammar looks like this:

System returns modulob::System:
   'system' name=ID 'consistsOf' modules += Module (',' modules += Module)* 

Module returns modulob::Module:
   'module' name=ID 

With the interface DSL the interfaces for a module should be listed in a different file. Its grammar (extract):

InterfaceModel returns modulob::InterfaceModel: 
   'interfaces for module' 
   module = [system::Module | QualifiedName]
   (interfaces += Interface)*

Interface returns modulob::Interface:
   'interface' name = ID 
      'requires' requiredInterfaces += [modulob::Interface | QualifiedName]
                 (',' requiredInterfaces += [modulob::Interface | QualifiedName])*

Here are some sample models. A system model:

system TradingOffice consistsOf
   module Journal, 
   module CurrencyConversion

Two interface models - one for each module:

interfaces for module TradingOffice.CurrencyConversion version "1.2"	
   interface Bar
interfaces for module TradingOffice.Journal version "1.2"
   interface Foo requires CurrencyConversion.Bar //not possible, only 'Bar' is possible

The first challenge is that interfaces cannot be referenced by their qualified name. Only their simple name is offered in the content assist for
specifying cross references. I thought the reason is that the meta class InterfaceModel does not contain an EAttribute 'name' and thus the computation of the qualified name of DefaultDeclarativeQualifiedNameProvider does not succeed.
I implemented my own IQualifiedNameProvider:

public QualifiedName getFullyQualifiedName(final EObject obj) {
   if (obj instanceof Interface) {
      Interface i = (Interface) obj;
      Module    m = ((InterfaceModel)i.eContainer()).getModule();//throws exception
      return QualifiedName.create(m.getName(), i.getName());
   return super.getFullyQualifiedName(obj);

If I test it, I get this exception:

java.lang.AssertionError: Cyclic resolution of lazy links : InterfaceModel.module->InterfaceModel.module
	at org.eclipse.xtext.linking.lazy.LazyLinkingResource.handleCyclicResolution(
	at org.eclipse.xtext.linking.lazy.LazyLinkingResource.getEObject(
	at org.eclipse.emf.ecore.resource.impl.ResourceSetImpl.getEObject(
	at org.eclipse.emf.ecore.util.EcoreUtil.resolve(
	at org.eclipse.emf.ecore.util.EcoreUtil.resolve(
	at org.eclipse.emf.ecore.impl.BasicEObjectImpl.eResolveProxy(
	at de.dubmas.modulob.system.impl.InterfaceModelImpl.getModule(
	at de.dubmas.modulob.NameProvider.getFullyQualifiedName(

So, I have two questions:

How can I retrieve a module's name without running in a cyclic link resolution?

I realized that the general challenge in my language design is that the containment reference from Modul to InterfaceModel
cannot be set by the language infrastructure because Module instances and InterfaceModel instances are created in different
resources. I tried to resolve this issue by introducing a second reference from InterfaceModel to Module and making it the eOpposite of Module-InterfaceModel-reference but then I ran into some more issues. In a code generation step I resolve this issue by appyling a model transformation that stiches together the complete
model graph. But I do not know how such a semantic can be achieved in the UI (language infrastructure).

Is there a best practice for dealing with such situations?


Re: Naming and Containment Hierarchy Issue [message #730148 is a reply to message #730141] Tue, 27 September 2011 17:41 Go to previous messageGo to next message
Christian Dietrich is currently offline Christian DietrichFriend
Messages: 13628
Registered: July 2009
Senior Member

(1) you can use the nodemodel to get the text that is written as module name. see . but see org.eclipse.xtext.nodemodel.util.NodeModelUtils.findNodesForFeature(EObject, EStructuralFeature) (2) too
(2) why don't you switch the place of containment / cross referencing?


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Re: Naming and Containment Hierarchy Issue [message #884690 is a reply to message #730148] Mon, 11 June 2012 15:51 Go to previous message
Michael Vorburger is currently offline Michael VorburgerFriend
Messages: 103
Registered: July 2009
Senior Member
Thank you for pointing to NodeModelUtils.findNodesForFeature here, very useful info. FTR: I've created a new bug report issue 382266 (I can't post links here yet) suggesting this may be added to documentation.
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