MOF24 — Multiple classifiers for an instance in MOF and RDF as defined in ODM

This is a question involving ODM as well as MOF XMI and Life-cycle.

In ODM we have RDF and OWL defined as MOF meta models, the assumption being, of course, that you can have MOF instances of RDF graphs. But can you? In RDF & OWL an instance (at any M level) can have (and frequently does have) multiple types – it is classified by more than one class. While this is perfectly legal in UML and even in the MOF meta model, I don’t think the concept is supported in XMI or the current life-cycle. So, can you actually represent RDF in MOF? If not, the ODM models are not valid – I hope I am wrong about this.

The ability for an instance to be classified by more than one class is a major advantage of RDF and of ontology languages, the C++ heritage in MOF of an instance statically being a member of a single class puts MOF at a disadvantage in relation to these other technologies. It makes it very difficult to represent different aspects of an instance, as can be seen from the package merge complexities - which would not have been required is we had multiple classification in MOF.

If this is actually a semantic mis-match between MOF and ODM, is may make more sense to add the capability to MOF since the MOF meta model does not preclude this capability – it is only a restriction of the MOF-PSM (XMI).

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