| Usage of DerivedUnion or simple derived? [message #627233] |
Tue, 25 November 2008 09:04 |
 Timothy Marc
Messages: 547
Registered: July 2009 |
Senior Member |
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Hey UMLer,
currently, i'm defining an UML-approximated metamodel, in which i make
heavily usage of subset/union. I understand the principles, that stand
behind these concepts, but is there a simple rule of thumb, when to use
Derived Union or simple derived attribute?
Let's have a look in the UML superstructure (Fig 7.10 (Features) and 7.14
(Packages)) the association end /feature between Classifier and Feature
(7.10) is declared as a DerivedUnion, because its content are derived from
the concrete participants. So far so good.
But the association end /ownedType between Package and Type is just an
ordinary subset. Should this be rather a DerivedUnion too, because its
contents are derived from the concrete types, which participate in that
association???
So, is there a rule of thumb when to use the one and when the other concept,
particulary with regard to derived and DerivedUnion?
Thanks for any comments on this topic.
Timothy
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