[Modeling] Modeling an Agent Class- composition

Dr. Hong Zhu hzhu@brookes.ac.uk
Thu, 26 Jun 2003 11:20:14 +0100

Hi, Gerd, and Stephen, and All,

Please think again and take into consideration of dynamic classification.

Maybe a better example is that: when a person is an employee of a company,
where both the employee and the company are agents, and the person is a part
of the company. When the compnay goes bust, (i.e. the agent company is
destroyed), the person lost his job and become an umployed. Which part-whole
relation of UML is applicable to this situation?


----- Original Message ----- 
From: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
To: "Stephen Cranefield" <scranefield@infoscience.otago.ac.nz>; "ModelingTC"
Sent: Thursday, June 26, 2003 9:19 AM
Subject: RE: [Modeling] Modeling an Agent Class- composition

> > Hong Zhu wrote (on 19 June):
> >> 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, ...
> > Composition seems to work perfectly well to me.
> Yes, I don't see any problem either.
> And contrary to Hong's appeal, we cannot rely on the UML2 spec for
> the semantics of aggregation/composition (especially wrt lifetime
> dependency), because it is unclear/confused and not well-defined.
> They say themselves:
> -----------------
> Semantic Variation Points (p.40 of the current UML2 document)
> The precise lifecycle semantics of aggregation is a semantic
> variation point.
> Semantic Variation Points (p.75 of the current UML2 document)
> Precise semantics of shared aggregation varies by application
> area and modeler.
> ------------------
> So we better rely on well-justified theories of the part-whole
> relationsip, such as sketched in my paper
> Towards Ontological Foundations for UML Conceptual Models
> http://tmitwww.tm.tue.nl/staff/gwagner/ODBASE-2002.pdf
> which is also a recommended reading in OMG's RFP for an Ontology
> Definition Metamodel.
> -Gerd
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