Issues for Mailing list of the MOF Support for Semantic Structures Finalization Task Force

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Issue 16233: SMOF does not implement dynamic classification of associations
Issue 17450: Multiple ownership not in UML semantic subset

Issue 16233: SMOF does not implement dynamic classification of associations (smof-ftf)

SMOF restricts itself to dynamically classifying elements, and requires links to have a single static Association.  The problem with that will show up as soon as we want to use SMOF for profiles.  We might, for example, have metaclasses C1 and C2 connected by an association A.  Apply the profile and it automatically infers that C1 needs also to be classified by P1 and C2 by P2 – and A by B.  But SMOF doesn’t allow the “A by B” part.  

Discussion:
Implementing dynamic classification of associations in SMOF would be a large piece of work; particularly it requires major upheaval in the Semantics section.  Every link would need to have multiple slots at either end, and a load of constraints to ensure that all of the slots at each end have the same value.  The notion of “opposite” slot would need to be substantially modified.
Several questions remain unanswered in my mind.  Is it possible to multiply classify a composition with a non-composition?  Is it possible to multiply classify a composition with a composition in the other direction?  If one or more of the classifying associations has properties which are derived and/or navigable and/or class-owned, what are the restrictions on multiple classification?  What about association end subsetting and redefinition?  Can the notions of compatibility or incompatibility be wholly or partially derived? What is the impact on XMI serialization?
Given the problems we had coming up with a satisfactory interpretation of MOF semantics to resolve the recent urgent issue on how to serialize StructuredActivityNode, I am very nervous about being able to answer these questions in a satisfactory way.  This is technically very tricky and I feel that a correct solution is out of my reach without investing a disproportionate amount of time and energy: I would have to build a working prototype, and I don’t have time or resources to do that.
My inclination, therefore, is to defer this issue.  If at some future date this turns out to be a real practical requirement, I would suggest it is resolved in an SMOF 2.0 which might by that stage be able to build on more clearly formulated MOF semantics.
 
Resolution:
As already stated by the issue provider, multiple and/or dynamic classification and reclassification of associations is not trivial. The FTF membership agreed that the work required to address this issue would exceed the time limit of this FTF and shall be picked-up by a future group or submission. 
Revised Text:
None.
Disposition:	Deferred

Section 10.1.1 (InstanceSpecification) has an operation getContainers with a postcondition returning potentially multiple instances linked at the owning end of composite associations.  This is disallowed under UML semantics, making SMOF not a subset of UML semantically.  Since SMOF is mainly concerned with multiple and dynamic classification, which does not affect issues of conflicting ownership (any more than multiple composite properties on a classifier do under the current MOF), it is not necessary for SMOF to address issues of ownership.