Issue 6455:  instantiations of Classifiers (uml2-rtf)
Source:  (, )
Nature: Uncategorized Issue
Severity: 
Summary: 7 and 14:  "An instance specification is a model element that represents an instance in a modeled system." [7.7.1]  There are no objects in a UML 2 model, but only models of objects, that is, instance specifications.  The instantiation of a UML class is not in the model, but in the modeled system.  At the same time, "an ExecutionOccurrence is an instantiation of a unit of behavior ..." [14.3.4] Suggested resolution:  Abandon the idea that there are no objects in a model.  Specify that an instanceSpecification with a class is an object in the model, the instiantiation of a class is an object in the model.  Likewise for an association and its links, and so on.


This brings the theory of classifiers and their instances and instantiations into alignment with the theory of behaviors and their occurrences.


It is consistent with the existence of power types in the language.


It is consistent with the MOF specification of meta-layers.


It removes the conflation of the type conformance and instatiation relationships with the representation relationship.  It reduces the meanings conflated into 'instance of' by one.



Thus, the UML places instantiations of Classifiers in the modeled system (not in the UML model) and, at the same time, places instantiations of Behaviors in the UML model (not in the modeled system).

Resolution: Discussion
The change proposed in the issue is fundamentally different than the basic interpretation of models in UML.
Further, the assertion that UML “places instantiations of Behaviors in the UML model (not in the modeled
system)” is not correct. An instance of a Behavior is an execution (in the modeled system), while an
ExecutionOccurrence is a model of such an instance. This is quite similar to the difference between an
instance and an InstanceSpecification. The UML 2.5 specification is now clearer on this.
Disposition: Closed - No Change
Revised Text: 
Actions taken:
November 7, 2003: received issue
February 20, 2015: closed issue
Discussion: 
Due to lack of time, the RTF/FTF agrees that the following are problems that need fixing, but decided to defer their resolution to a future RTF working on this specification.
End of Annotations:=====
nd 14:  "An instance specification is a model element that represents an instance in a modeled system." [7.7.1]  There are no objects in a UML 2 model, but only models of objects, that is, instance specifications.  The instantiation of a UML class is not in the model, but in the modeled system.  At the same time, "an ExecutionOccurrence is an instantiation of a unit of behavior ..." [14.3.4]


Thus, the UML places instantiations of Classifiers in the modeled system (not in the UML model) and, at the same time, places instantiations of Behaviors in the UML model (not in the modeled system).
...


Suggested resolution:  Abandon the idea that there are no objects in a model.  Specify that an instanceSpecification with a class is an object in the model, the instiantiation of a class is an object in the model.  Likewise for an association and its links, and so on.


This brings the theory of classifiers and their instances and instantiations into alignment with the theory of behaviors and their occurrences.


It is consistent with the existence of power types in the language.


It is consistent with the MOF specification of meta-layers.


It removes the conflation of the type conformance and instatiation relationships with the representation relationship.  It reduces the meanings conflated into 'instance of' by one.