[Modeling] Modeling an Agent Class- register your opinion

[Joaquin Peña]

Hello:

I think that the main problem is that object orientation does not
fit well with system where behaviour is crucial.

This issue can be easily solved using Role Modelling:

A employee is not a class, it is a role that an object of the
class person can perform. Thus, if a department is destroyed, all
its employees lose this role becoming only persons (performing the
other roles they have, i.e. father, engineer, ...).

There are a lot of papers on how to implement roles in the OO
paradigm, but we think most appropriate approach is such that use
Aspect-Oriented Programming where functionality and behaviour are
orthogonal in the implementation.

Joaquin.


> -----Mensaje original-----
> De: modeling-admin@fipa.org [mailto:modeling-admin@fipa.org] 
> En nombre de Wagner, G.R.
> Enviado el: jueves, 19 de junio de 2003 18:58
> Para: Dr. Hong Zhu ; Wagner, G.R.; James Odell ; ModelingTC 
> Asunto: RE: [Modeling] Modeling an Agent Class- register your opinion
> 
> 
> > 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.
> 
> Hong,
> 
> 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 
> unfounded.
> 
> -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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