Dear All, (01)
There is another community which has interest in 4D models - the
engineering analysis and testing community. (02)
I have been creating data structures (though not ontologies) for this
community since the 1970s, and the progress has been as follows:
1) we created static models which deal only with variation with
respect to space;
2) we kludged in time as best we could - sometimes as a sequence of
snapshots of 3D distributions, sometimes by replacing a single
parameter by a function with respect to time;
3) finally the models were rewritten so that space and time were
dealt with identically. (03)
Within a body (engine piston or Atlantic ocean say) it is customary
to consider parts defined by space and by time, and to consider
property variation (temperature say) with respect to space and time.
Our customers in this community do not expect space and time to be
handled differently. (04)
Best regards,
David (05)
At 11:10 23/01/2011, you wrote:
>Dear Pat,
>
>This could be misinterpreted.
>
> > > A 4D object, in this context, is an object that can have different
> > > state at different times.
> >
> > No, that is a continuant. In a very strict 4D model, there is no single
> > 'thing' that has the various states. (Although I hasten to add, it is very
> > convenient to be somewhat less strict than this. I mean only to make the
> > conceptual distinction.)
>
>MW: As you know, there are two versions of 4D, one of which, stage theory,
>only admits timeslices with infinitesimal temporal thickness called stages
>which can be strung together, the other, perdurantism, allows objects to be
>extended in time as well as space, and that one spatio-temporal extent can
>be a part of another.
>
>MW: The ambiguity comes from "there is no single 'thing' that has the
>various states".
>
>MW: This is true if one is talking about stage theory - there are only the
>various stages. However, it is not true for perdurantism, provided one
>interprets "has" as meaning "has temporal parts".
>
>Regards
>
>Matthew West
>Information Junction
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>
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