Re: links between objects



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Jos Warmer (J.Warmer@klasse.nl)
Wed, 19 Jul 2000 14:37:29 +0200


Leonor, John, John is right. This is not a question of OCL semantics, but of the semantics of UML associations. If there is a link between two objects, you can navigate it in both directions. If navigation in one directions is possible, this implies by definition that the way back is also possible. In general when we have a class model : +---+ a * +---+ | A |---------| B | +---+ * b +---+ the following invariants is always true: context A inv: b->notEmpty() implies b.a->includes(self) Regards, Jos At 01:08 PM 7/19/00 +0100, John Daniels wrote: >> When in a postcondition I want to express that there is a link between >> objects a and b is it enough to say it in one direction or do I have to >> say it in both directions? I am specifying operations at a high level >> of abstraction and at a point where associations are all bidirectional. > >My understanding is that you need only assert the relationship in one >direction. > >--John > >========================================================================= >John Daniels > > > >To remove yourself from this list please mail puml-list-request@cs.york.ac.uk >with a message containing the word "unsubscribe". > > > > _____________________________________________________ Klasse Objecten tel : +31 (0)35 6037646 Chalonhof 153 fax : +31 (0)35 6037647 3762 CT Soest email : J.Warmer@klasse.nl The Netherlands internet: http://www.klasse.nl


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