Cecil Lynch replied:
<CL> The problem here is that "Employee" isA "Role" and a "Role" is NOT a
type of person. It isA "Social Relation" or such and modeling it as a person
will lead to problems as you suggest, but this is a problem because of the
modeler, not the model. This makes the rest of the argument difficult to
follow.</CL> (01)
No, in this ontology Employee is a subtype of both Role and Person. The
model permits multiple inheritance and is logically consistent. There is no
logical problem in the model as described. If it doesn't fit one's
preferences for use of particular word, then just substitute a Gensym for
the offending term. The logic stays the same.
Of course the type "Role" is not a Person, neither is the type "Person" a
Role. There are multiple subtypes of Role, and multiple subtypes of Person.
Employee is one of the subtypes of the Role type, and one of the subtypes of
the Person type. (02)
The "problems", as I explicitly said, would only arise if one were to use
the types thus defined in an inappropriate manner. There is no problem in
the way they are used in the illustration. One will have problems if one
uses *any* ontology element in a manner inconsistent with its logical
specification. (03)
Once again, I would suggest that if one wants to assert some kind of problem
or inconsistency, please do it with an explicit set of logical assertions.
We can often resolve questions purely with language, but discussions of
logical consistency are especially susceptible to misleading interpretation
when we use words whose non-technical meanings get mixed up with the
intended technical meaning. (04)
Pat (05)
Patrick Cassidy
MICRA, Inc.
908-561-3416
cell: 908-565-4053
cassidy@xxxxxxxxx (06)
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
> bounces@xxxxxxxxxxxxxxxx] On Behalf Of Cecil O. Lynch, MD, MS
> Sent: Wednesday, March 19, 2008 7:52 AM
> To: '[ontolog-forum] '
> Subject: Re: [ontolog-forum] Ontology similarity and accurate
> communication
>
>
>
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Patrick
> Cassidy
> Sent: Wednesday, March 19, 2008 2:36 AM
> To: '[ontolog-forum] '
> Subject: Re: [ontolog-forum] Ontology similarity and accurate
> communication
>
> Matthew,
> If one were to attempt to create instances of a 3D Person that were
> also
> instances of a role, the multiplicity you refer to would be a problem.
> In
> the illustration below, Matthew is an instance of 3D Person, not an
> instance
> of Employee - if Matthew were an instance of Employee, the problem you
> describe would then present itself. But we can create instances of
> Role
> such as an Employee that have a Person as a filler. Nevertheless the
> *Role*
> "Employee" is also a subtype of Person, therefore an instance of an
> Employee
> is always an instance of a Person, implicitly though not explicitly.
>
> <CL> The problem here is that "Employee" isA "Role" and a "Role" is NOT
> a
> type of person. It isA "Social Relation" or such and modeling it as a
> person
> will lead to problems as you suggest, but this is a problem because of
> the
> modeler, not the model. This makes the rest of the argument difficult
> to
> follow.</CL>
>
> But
> the instances of a Role such as Employee are more like time slices and
> are
> not identical to the instance of Person that fills the role. The
> multiplicity is in the multiplicity of TimeSlices, as there are in a 4D
> representation; every different TimeSlice is a different entity. The
> way
> that can work is illustrated below using OWL.
> One comment I made was not phrased properly:
> [PC] > > (3) a person can be an instance of multiple roles in any
> given
> time
> > > interval
> It would more accurately have been phrased that:
> (3a) an instance of Person can fill multiple roles in any given time
> frame
> (3b) a timeslice of Person can be an instance of multiple roles
> (3c) an instance of Role in any given time interval can be an
> instance of
> Person - because Person and Role are not disjoint.
> The illustration below should clarify what that means.
>
> Perhaps the non-intuitive element is that an instance of a Role (a
> TimeSLice) can also be an instance of a Person(a dimension-neutral
> Type) -
> because the type Person is not disjoint with the type TimeSlice. In
> the
> illustration below, Matthew is a Person, but the instance
> MatthewAsEmployeeOfShellAndLeeds is a Role - and also an instance of
> Person
> - but is not identical to Matthew. It is more like a TimeSlice of
> Matthew.
> Even So, Matthew is not necessarily 3D or 4D, Matthew is a dimension-
> neutral
> entity.
> If one were to use a formalism that permitted relation arities higher
> than
> two, it would be possible to specify roles and their time limits
> without
> using time slices. TimeSlices (among which are Roles) are
> syntactically
> convenient when using OWL, they aren't logically necessary. They have
> the
> same logical effect as an explicit time-indexed assertion on a
> dimension-neutral entity. In that case, there would be no TimeSlices,
> only
> time-indexed assertions (which are logically equivalent, after
> translation,
> to assertions on TimeSlices). The axioms to translate the two
> formalisms
> are not here because this is a pure OWL representation.
>
> All instance of Role should have start and end times specified - they
> are
> time slices.
> Person is in this case neither exclusively 3D nor 4D - time slices
> can be
> generated by making a person an instance of 'TimeSlice', or an instance
> of
> Role, which is a subtype of TimeSlice. Every TimeSlice has a start
> time and
> end time.
> But an instance of Person can also have attributes and relations
> specified
> by explicit time-indexed relations, without using TimeSlices.
>
> In the following note that an Employee is a Role, and something can
> be an
> instance of an Object as well as a Role.
> (definitions - some parts are from Cyc - are abbreviated).
>
> HumanRole is a subtype of Person and Role
> Every HumanRole is a Role whose RoleFiller is a Person
> (restriction)
> PersonWithOccupation is a subtype of HumanRole
>
> <owl:Class rdf:ID="Employee">
> <rdfs:comment>A Person who was employed by another Agent in
> some
> hiring event.</rdfs:comment>
> <rdf:type rdf:resource="#PersonType"/>
> <rdf:type rdf:resource="#RoleType"/>
> <rdfs:subClassOf rdf:resource="#TemporaryRoleCreatedByEvent"/>
> <rdfs:subClassOf rdf:resource="#PersonWithOccupation"/>
> <rdfs:subClassOf>
> <owl:Restriction>
> <owl:onProperty>
> <owl:ObjectProperty rdf:about="#isEmployedBy"/>
> </owl:onProperty>
> <owl:someValuesFrom rdf:resource="#IntelligentAgent"/>
> </owl:Restriction>
> </rdfs:subClassOf>
> </owl:Class>
>
> **** NOTE that 'employee' is a subtype of 'Person' ****
>
> <owl:Class rdf:ID="EmployeeOfShell">
> <rdfs:subClassOf rdf:resource="#Employee "/>
> <rdfs:comment>A person who is an employee of Shell.</rdfs:comment>
> </owl:Class>
>
> <owl:Class rdf:ID="EmployeeOfLeeds">
> <rdfs:subClassOf rdf:resource="#Employee "/>
> <rdfs:comment>A person who is an employee of Leeds.</rdfs:comment>
> </owl:Class>
>
> <!-- Matthew is employee of Shell from 1990 to 2008
> Matthew is employee of Leeds from 1980 to 2004
> -->
>
> <Person rdf:ID="Matthew"/>
>
> <EmployeeOfShell rdf:ID="MatthewAsEmployeeOfLeedsAndShell">
> <rdf:type rdf:resource="#EmployeeOfLeeds"/>
> <hasRoleFiller rdf:resource="#Matthew"/>
> <rdfs:comment>Matthew is an Employee of Both Shell and Leeds
> from
> the beginning of
> 1990 to the end of 2004.</rdfs:comment>
> <hasStartingTimePoint rdf:ID="DTEG19900101T0000"/>
> <hasEndingTimePoint rdf:ID="DTEG20041212T2400"/>
> </EmployeeOfShell >
>
> Pat
>
> Patrick Cassidy
> MICRA, Inc.
> 908-561-3416
> cell: 908-565-4053
> cassidy@xxxxxxxxx
>
>
> > -----Original Message-----
> > From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
> > bounces@xxxxxxxxxxxxxxxx] On Behalf Of matthew.west@xxxxxxxxx
> > Sent: Tuesday, March 18, 2008 2:42 PM
> > To: ontolog-forum@xxxxxxxxxxxxxxxx
> > Subject: Re: [ontolog-forum] Ontology similarity and accurate
> > communication
> >
> > Dear Pat,
> >
> > > 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.
> > >
> > > (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
> > > interval
> > > (4) in some time interval Matthew can be an instance of "Employee
> > of
> > > Shell" and "Employee of Leeds U"
> >
> > MW: What you are missing is that EACH instance of employee MUST be a
> > separate person if employee is a subtype of person. To put that the
> > other way round, if I am just one person and there is an employee
> > subtype of person, then I either am or am not an instance of
> employee,
> > but I can only be an instance of employee once.
> >
> > MW: If you think that a Person can be more than one employee, then
> the
> > relationship between person and employee is something other than
> > subtype/supertype.
> >
> > MW: If I were a 3D-ist then I would suggest somthing like a consists
> of
> > relation.
> >
> > >
> > > 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
> > > types.
> >
> > MW: In 4D it is quite clear, and employee is a state of a person,
> > and the relationship between person and employee is temporal part of.
> > Both employee and person are subtypes of state_of_person.
> >
> > MW: The interesting thing about temporal part of is that most
> > properties are inherited by substates (except for example being
> > a person for the whole of their life).
> >
> >
> > Regards
> >
> > 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
> > http://www.shell.com
> > http://www.matthew-west.org.uk/
> >
> > >
> > > I need to be more specific. Another day or two for my
> > > more detailed
> > > reply to PatH.
> > >
> > > Pat
> > >
> > > Patrick Cassidy
> > > MICRA, Inc.
> > > 908-561-3416
> > > cell: 908-565-4053
> > > cassidy@xxxxxxxxx
> > >
> > >
> > > > -----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
> > > > communication
> > > >
> > > > 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
> > > > being).
> > > >
> > > > 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
> > > > University.
> > > > 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?
> > > >
> > > > Regards
> > > >
> > > > 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
> > > > http://www.shell.com
> > > > http://www.matthew-west.org.uk/
> > > >
> > > >
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