UML22 — Default values for ValueSpecification are not specified properly

There are a few cases when the default is documented as a ValueExpression, as follows:

• JoinNode.joinSpec = {default value is" and"}
• ActivityEdge.guard= {default value is "true"}

These defaults are currently just plain text in the Rose Model displayed under the ValueSpecification as shown in figure 185 in the superstructure specification.

They should be included formally in the model. However it is not clear that the UML2 notation text allows defaults for association ends, and that those defaults can include expressions that construct instances of classes such as ValueSpecification. For example, the notation for ActivityEdge::guard in figure 185 could be:

+guard = LiteralBoolean(true)

The default value for guard is set to a newly constructed LiteralBoolean (a ValueSpecification) with value true.

Recommendation:

Ensure the text notation for default values includes the ability to construct InstanceSpecifications, and that the notation supports defaults for properties on association ends.

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