[Modeling] Modeling an Agent Class- register your opinion

[Dr. Hong Zhu]

Hi, Gerd,

> > I am now more confused about UML's aggregation. The definition of
> > aggregation kinds in UML 2.0 is far from clear.
>
> I agree. It's confused.
>
> > It states that the compoite object has responsibility for the existence
> > and storage of the composed objects (parts)'.
>
> This is just a  confusing remark. Better don't take it serious. In one
> sentence they say, that the components must be destroyed whenever
> the composite is destroyed (this is inseparability), but in the next
> sentence they say that it would be also OK to attach the component to
> another composite (this would be the property of a mandatory whole)
> The real defining property of  composition is that it is a kind of
aggregation
> with *non-shareable* parts. Those other properties (inseparable part and
> mandatory whole etc.) are orthogonal to it.

Are we referring to the same version of UML definition? In UML 2.0 document
(Mar 3, 2003 edition), I cannot find the statements that you are quoting
here.

The problem is, if we don't take the definition in the specification of the
language seriously, on what basis should we define AUML and what should we
refer to?

>
> > Could you please let me know your web address so that I can download
> > your paper?
>
> Please use google and search for "Gerd Wagner" (I'm currently on holidays
> and  don't know my web page by heart :-)
>

I found your web address by google, now. Thanks.

> > However, I feel that you have missed my point, which is, the aggregation
> > kinds in UML seems not suitable for agents.
>
> Why should this be so? I didn't get the point.
>
> > There are only two disjoint aggregation types in UML no matter how they
are
> > defined, but we need a third type for agents.
>
> Why?
>

Please refer to my draft paper on CAMLE, which is included in AUML's website
in the Supplement Document page. The following is a simple example, that
have used to answer Frits' question.

We have a agent that represents a department in a university, and a number
of agents as members of the department. When the department is destroyed,
the members as individuals still exist, but their membership to the
department is lost.

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.

Therefore, we need a new kind of part-whole relationship between department
and its members, which is called 'congregation' in my language CAMLE.

Best regards,
Hong


> -Gerd
>
>
> ----- Original Message ----- 
> From: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
> To: "Dr. Hong Zhu " <hzhu@brookes.ac.uk>; "James Odell "
> <email@jamesodell.com>; "ModelingTC " <modeling@fipa.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,
> there
> are two
> > > types of whole-part relations:
> > > (1) composition, in which the lifespan of the whole and the part is
> the
> > > same, and (2) aggregation, in which the lifespan of the whole and
> part
> > > is independent. Having two whole-part relations is inadequate for
> > > agent-orientation due to agent's autonomous behaviour. For example,
> we
> > > have a agent which represents a department in a university, and a
> number
> of
> > > agents as members of the department. When the department is
> destroyed,
> > > the members as individuals still exist, but their class membership
> as
> the
> > > member of the department are lost.
> >
> > This is a misunderstanding of the UML aggregation concept. Composition
> > is defined as a "non-shareable" aggregation, and not via lifetime
> dependency.
> > There are some misleading remarks about lifetime dependency in UML
> 1.4.
> > Lifetime dependency is implied in aggregations with inseparable parts.
> > It's not related to shareability. Please see my ODBASE'2002 paperr on
> > ontological foundations of UML (on my homepage) for further
> explanattions.
> >
> > Of course, all general ontological isssues of the part-whole
> relationship
> > apply to all things, no matter if they are agents or objects.
> >
> > -Gerd
> >
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>
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