Description Nicolas Rouquette 2010-05-31 20:27:44 EDT

I have been using QVTo quite extensively to automate some of the most error-prone steps involved in producing the normative artifacts for OMG's UML 2.4.
In that context, I've been using QVT's dictionary types to track various correspondences. 
However, I have had to work around a limitation due to OCL / QVT in that OCL doesn't have support for QVT's dictionary type. 
For example, the following is syntactically correct but cannot be launched:

transformation Ecore2UML(in eModel : ECORE, out umlModel : UML);

// syntax is OK; at launch this produces an error: "OCL collection kind (Collection) is not implemented in the java collection factory."
property table : Dictionary(ecore::EClassifier, UML::Classifier) = Dict{}; 

main() {
	...
}

To work around this limitation, I've passed dictionary values as parameters to queries, helpers & mapping rules.
Here's an example of this in a modified version of the qvto.ecore2uml example:

mapping EClass::toClass(inout table : Dict(ecore::EClassifier, UML::Classifier)) : Class inherits ENamedElement::toNamedElement when { not self.interface } {
	superClass := self.eSuperTypes->map toClass(table);
	interfaceRealization := self.eSuperTypes[interface]->xcollect( i |
		object InterfaceRealization {
			contract := i.map toInterface(table);
		}
	);

	isAbstract := self._abstract;
	ownedAttribute += self.eStructuralFeatures->map toProperty(table);
	
	table->put(self, result);
}

After the transformation finishes, the family.uml.qvtotrace contains only the values of the dictionary, not the key/value pairs; e.g:

  <traceRecords>
    <mappingOperation name="toClass" package="Ecore2UML" module="Ecore2UML">
      <runtimeMappingOperation href="platform:/resource/qvto.ecore2uml/transforms/Ecore2UML.qvtox#//toClass"/>
    </mappingOperation>
    <context>
      <context name="self" type="EClass">
        <value>
          <modelElement href="platform:/resource/qvto.ecore2uml/in/family.ecore#//Family"/>
        </value>
      </context>
    </context>
    <parameters>
      <parameters kind="INOUT" name="table" type="Dictionary(EClassifier, Classifier)">
        <value collectionType="OclCollection">
          <collection>
            <modelElement href="platform:/resource/qvto.ecore2uml/out/family.uml#_QV12T20REd-a2rPGu1hnsg"/>
          </collection>
          <collection>
            <modelElement href="platform:/resource/qvto.ecore2uml/out/family.uml#_QV12aG0REd-a2rPGu1hnsg"/>
          </collection>
          <collection>
            <modelElement href="platform:/resource/qvto.ecore2uml/out/family.uml#_QV12VG0REd-a2rPGu1hnsg"/>
          </collection>
          <collection>
            <modelElement href="platform:/resource/qvto.ecore2uml/out/family.uml#_QV12QW0REd-a2rPGu1hnsg"/>
          </collection>
        </value>
      </parameters>
    </parameters>
    <result>
      <result kind="OUT" name="result" type="Class">
        <value>
          <modelElement href="platform:/resource/qvto.ecore2uml/out/family.uml#_QV12WW0REd-a2rPGu1hnsg"/>
        </value>
      </result>
    </result>
  </traceRecords>