Dear Dog, (01)
> > A 3D ontology can take time into account quite easily by stating the
> > at which some statement is true.
> > 3D vs 4D is about the fundamental nature of individuals and whether
> > are extended in time as well as space.
> 3D vs. 4D has to do with whether temporal-spatial individuals are
> as being extended in time as well as in space. Use of a model does not
> requires a change in the "fundamental nature of individuals." (02)
MW: You can play it either way. I agree it is a theory, but such theories
are supposed to be of reality. So at least one possibility is that the
theory represents how things really are. I would accept that there is not a
definitive proof at present one way or the other.
> > Under 3D they are extended in space only
> > and pass through time, in 4D they are extended in time as well as
> But both of those models are only useful in enabling statements to be
> about that time-constrained individual. Both models allow such
> to be made. (03)
MW: My experience is that 3D loses some definition and opens up some
ambiguity, which you would expect if you think about what you lose when you
project a 3D model onto 2D, but I'm not at a stage where I could prove that.
> > A
> > consequence is that "me today" is just an object in 4D, a state of me
> > a beginning at the start of the day and an ending at the end of the
> > where
> > as in 3D I have to say something like "me at all points in time
> > today".
> Close. In 4D, "me today" is a temporal slice of me, cut by the
> and ending times of the day. (04)
MW: I call such things states as a more natural use of language. (05)
> If my starting or ending time intersects
> today, the object does not both begin at the start of the day and end
> at the end of the day. (06)
MW: Not sure what you mean by this, today is a spatio-temporal extent,
somewhat larger than me. The intersection of this with me is me today.
> One must be very careful in what such a temporal slice "object" is
> considered to be. If the temporal slice is considered to be a member
> of the same classes which the 4D worm, then instances of such classes
> can not be counted. An object predicate that is functional in an
> position, may be functional with respect to complete 4D worms, or with
> co-extensive temporal slices. (07)
MW: Quite, therefore I distinguish between me - meaning whole life me, and
state of me, meaning me for some period of time, including the whole life of
me. Being a whole life me is not temporally dissective, though most
properties of a state are, i.e. they are inherited by their temporal parts.
> Using a 4D model does not solve all the temporal problems of a 3D
> model. (08)
MW: Can you be specific about which problems remain? (09)
> One can map descriptions from one model to the other. (010)
MW: You can certainly map 3D to 4D.
> I know i am stepping onto religious ground, but imho, a 3D model is
> to work with. (011)
MW: I know many people find it more natural, largely because it is closer to
how everyday language works, but my experience is that 4D is more rigorous
and leaves fewer choices for how to model things, which means consistency is
easier to achieve. You only need to look at the different 3D upper
ontologies to see how much 3D leaves open. (012)
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