[Modeling] Modeling an Agent Class- register your opinion

[Dr. Hong Zhu]

Hello, Joaquin,

----- Original Message ----- 
From: "Joaquin Peņa" <joaquinp@us.es>
To: "'Wagner, G.R.'" <G.R.Wagner@tm.tue.nl>; "'Dr. Hong Zhu '"
<hzhu@brookes.ac.uk>; "'James Odell '" <email@jamesodell.com>; "'ModelingTC
'" <modeling@fipa.org>
Sent: Thursday, June 19, 2003 6:56 PM
Subject: RE: [Modeling] Modeling an Agent Class- register your opinion


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

Yes, I agree.

> 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, ...).
>

What is a role in object orientation? According to the OO philosophy that
'everything is object', the answer can only be that roles are objects. Of
course, they are defined through class, i.e. instances of class. This hights
why OO does not modelling the world in a straightforward way, but one needs
to twist their minds and arms to view the world.

> 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.
>

I believe that agent-orientation can provide a nature way solve this
problem.

-Hong

> 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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