UML14 — Optimize Instance data values

Although the DataValue class claims to 'have no identity' it nonetheless inherits from ModelElement and is represented as a 'normal' object in the interchange as well as the logical metamodel (so will also inherit annotation and name - though presumably it's 'name' that is used to hold the actual value of the DataValue since no attribute seems to be actually defined for that purpose). And will it end up becming a first class object by default in most automatically-generated repositories or tool implementations.

There are applictions of UML, and CWM which reuses it, which require a large number (several thousand) of data instances to be modeled - for which requiring a separate physical/interchange object for each data value is extremely inefficient. Not only does it double the number of objects, the DataValues have to be contained somewhere - which results in a parent package not only owning the Instance objects but a large number of DataValues also which must be filtered out if wanting to navigate from an Instance Model (for example) to its instances.

Since a DataValue in practice has a 1-1 relationship with an AttributeLink, it is proposed that in the Interchange Model at least that DataValues be represented as a String attribute on AttributeLink. For forward compatibility it might be necessary to introduce a subclass of AttributeLink for this - which could even be called 'DataSlot' for compatibility with CWM (an equivalent proposal has been made to CWM RTF which uses 'Slot' instead of 'AttributeLink') And one could retain DataValue in deprecated mode.

NB There is no practical benefit in having the current Link from dataValue to Classifier (DataType), since this is already linked from the Attribute (and the ability to record that a DataValue has a subtype of its Attribute's type seems too obscure in comparison to the cost).

see above