[Modeling] Modeling an Agent Class- register your opinion
Thu, 19 Jun 2003 18:57:36 +0200
> The relationship between the department and it members is different from
> composite in UML, because the agent is still alive after the owner is
> destroyed. It is also different from aggregation because the destroy of
> the owner (the department) affects the behaviour of the member agents (they
> lost the membership of department members and the associated capability and
> accessible resources). If an object is a part of another object as an
> aggregate, the destroy of the owner will not affect the part object's
> membership to any class, so does not affect its behaviour.
again, the difference between aggregaion and composition is simply
the property of shareable parts. The property of lifetime dependency
you refer to is orthogonal to this.
Obviously, in your example, there is an aggregation relationship between
the members of a department and the department (because a member
can be also a member of another department, i.e. members can be
shared). An aggregation relationship does not imply anything wrt
lifetime dependency and it does neither imply that it would not affect
its parts. These are additional, othogonal issues.
So, your conclusion that we need a "third" part-whole relationship is
> ----- Original Message -----
> From: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
> To: "Dr. Hong Zhu " <firstname.lastname@example.org>; "James Odell "
> <email@example.com>; "ModelingTC " <firstname.lastname@example.org>
> Sent: Tuesday, June 17, 2003 9:03 PM
> Subject: RE: [Modeling] Modeling an Agent Class- register your opinion
> > > The part-whole relationship between agents are also different:
> > > The aggregation relationships between the whole and part is
> different in
> > > agent classes from that in object class. In object orientation,
> are two
> > > types of whole-part relations:
> > > (1) composition, in which the lifespan of the whole and the part
> > > same, and (2) aggregation, in which the lifespan of the whole and
> > > is independent. Having two whole-part relations is inadequate for
> > > agent-orientation due to agent's autonomous behaviour. For
> > > have a agent which represents a department in a university, and a
> > > agents as members of the department. When the department is
> > > the members as individuals still exist, but their class membership
> > > member of the department are lost.
> > This is a misunderstanding of the UML aggregation concept.
> > is defined as a "non-shareable" aggregation, and not via lifetime
> > There are some misleading remarks about lifetime dependency in UML
> > Lifetime dependency is implied in aggregations with inseparable
> > It's not related to shareability. Please see my ODBASE'2002 paperr
> > ontological foundations of UML (on my homepage) for further
> > Of course, all general ontological isssues of the part-whole
> > apply to all things, no matter if they are agents or objects.
> > -Gerd
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