Dear John and Bill, (01)
> See below.
>
> > PH> We are quantifying over 4-d entities, ie 'slices' of
> > > a 'history-worm' ... which I will write by pairing a name
> > > with a time-interval, eg [PatH, 1997-2007]. Person, to wit
> > > [PatH, (lifetimeOf PatH)]. It is not a Person. So
> > >
> > > forall x Employee(x) implies Person(x)
> > >
> > > is false: in fact, this is a counterexample.
> > > So Employee is not < Person.
> >
> > OK. I accept the point that the definition of
> > "Employee < Person" is equivalent to
> >
> > forall x Employee(x) implies Person(x)
> >
> > in a 3D ontology, but it creates problems in 4D.
>
> I don't see that this creates a problem for 4D - it's simply
> *wrong* to
> say in 4D (as Pat points out) if one takes 'Person' to be the class of
> sums of Person_Slice-s. Under 4D, one could truly say:
>
> Employee < Person_Slice (02)
MW: Yes, Bill is quite right, one could add:
Person < Person_Slice
Since a Person is a maximal Person_Slice (though I would prefer state_of_person
to person_slice). (03)
Regards (04)
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 (05)
Tel: +44 20 7934 4490 Mobile: +44 7796 336538
Email: matthew.west@xxxxxxxxx
http://www.shell.com
http://www.matthew-west.org.uk/ (06)
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