[MW] Ah. But it doesn’t. That is what the 3D
relation needs to have (when did it apply). In 4D the relation would simply
between the states of the objects for which it was true, and the time element
is derived from the start and end time of the state. You would also need to
know which objects the states were temporal parts of of course.[/MW]
Ah thanks for the clarification; it looks like, as with any
perspective, there is 4D + lots of variants. I was just thinking of how to
enforce minimal "4Dness" in an ontology via axioms, but it appears
what I proposed was too specific.
[MW] There are two versions of 4D, stage theory – where there
are lots of slices strung together like a string of pearls, and perdurance
theory, where there are parts extended in time, and not just at points in time.
The variation on both of these is whether identity is based on spatio-temporal
extent. However, neither of these has dates on relations – only spatio-temporal
extents have dates in 4D. Anything else is a version of 3D. 4D is not about
dealing with time at all, but a particular way of doing so.
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