This is a good issue, but I think it has a resolution without the problem
you envision, because in 3D the types of an entity can change with time. (01)
(1) employee is a role, which means that it must be time indexed.
(2) every instance of employee (in some time interval) is an instance of
person (in that time interval)
(3) a person can be an instance of multiple roles in any given time
(4) in some time interval Matthew can be an instance of "Employee of
Shell" and "Employee of Leeds U" (02)
In 4D, I believe that the 4D worms will intersect, and that is another way
of viewing the same thing, but it is only inconsistent if one assigns the
same type "Person" to a 4d object in one ontology and a 3D object in the
other, and then tries to use the same term to represent the two different
I need to be more specific. Another day or two for my more detailed
reply to PatH. (04)
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
> bounces@xxxxxxxxxxxxxxxx] On Behalf Of matthew.west@xxxxxxxxx
> Sent: Tuesday, March 18, 2008 5:18 AM
> To: ontolog-forum@xxxxxxxxxxxxxxxx
> Subject: Re: [ontolog-forum] Ontology similarity and accurate
> Dear John,
> > MW> So for example, there are ontologies where you will find employee
> > > as a subtype of person, and others that understand it is not.
> > I don't know which way you are advocating, but I'll summarize my
> > position:
> > 1. There is a fundamental distinction between natural types, such
> > as Cat or HumanBeing, and role types, such as Pet or Employee.
> > 2. Every instance of a role type is a subytpe of some natural type,
> > but it may also be a subtype of other role types.
> > HeartSpecialist
> > is a subtype of Physician, which is a subtype of HumanBeing.
> MW: I do mean that employee is not a subtype of person (or human
> MW: If we remind ourselves of what being a subtype means, it means that
> each instance of a subtype is an instance of the supertype. Now ler us
> look at an example. I am an employee of both Shell and Leeds
> I have different employee numbers, very different salaries, and
> different start dates. Now if employee is a subtype of person then
> each of these is a person, i.e. there are two of me.
> MW: This kind of situation is true of roles generally, you can play
> multiple roles at the same time and the same role multiple times
> (and at the same time). These do not all generate new people.
> MW: So the question is: what is the relationship between a role
> and the person who plays is. Fortunately, as a 4-dimensionalist, there
> is a simple answer. The role is a temporal part of the person that
> plays the role, or if you prefer, the person for a period of time,
> rather than for the whole of their life.
> MW: This is not so different from the question of the vase and the
> piece of clay. Are pots subtypes of clay? Or is the pot a different
> object than the piece of clay it is made from?
> Matthew West
> Reference Data Architecture and Standards Manager
> Shell International Petroleum Company Limited
> Registered in England and Wales
> Registered number: 621148
> Registered office: Shell Centre, London SE1 7NA, United Kingdom
> Tel: +44 20 7934 4490 Mobile: +44 7796 336538
> Email: matthew.west@xxxxxxxxx
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