MOF2I2 — MOF 2.0 Core 03-04-07, Chapter 5. Identifiers

On page 36:

“Identity extends Basic::Property with the ability to designate a property as an identifier for the containing object. Properties: isID: Boolean [0..1] True indicates this property can be used to uniquely identify an instance of the containing Class. Only one Property in a class may have isID==true.”

The restriction that only one Property in a class may have isID==true is debilitating. It is common for objects to be identified in the modeled application domain by a unique combination of a set of properties. For example, an object that represents an instance of an n-ary association in the modeled domain will, in general, be identified by a unique combination of n properties, each one of which is an identifier of a participating object in the association. Not being able to carry this natural condition into the MOF requires practitioners to devise a work-around, such as introducing a superfluous surrogate identifier, to be able to externally identify such objects.

It is requested that the MOF 2.0 Core specification be revised by the FTF to allow any number of sets of properties to be identifiers. Any client of an object needs to be able to select the identifier set most convenient for them, and different clients need to be able to accurately identify the object, regardless of how other clients may find it.

This issue is important to the Business Semantics of Business Rules submissions, which require domain identifiers for objects. Other MOF users will also benefit.

Introduction of the Identity package is a potentially powerful and badly needed improvement over MOF 1.x to enable the use of external identifiers for MOF objects, which will greatly facilitate accurate model interchange, reuse, aggregation, and transformation. The present limitation stunts this potential. Please take this modest extra step to assure the full potential of the Identity package can be realized.

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