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Re: [ontolog-forum] Thing and Class

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Tue, 09 Sep 2008 16:57:59 -0400
Message-id: <48C6E357.6060601@xxxxxxxxxxx>
Pat,    (01)

For many applications, I prefer a 4D ontology, but I also recognize
the need to map the categories of such ontologies to the language
that people use in everyday life.    (02)

PH> But the key point is that to assert existence in the 4d framework
 > an assertion itself is not temporal. Assertions stand outside time
 > and speak about it, rather than being embedded in it and having
 > to speak about other times indirectly, for example by using tenses.
 > Moreover, it frees one from the confusion that relates intensionality
 > to existence over time.    (03)

I agree, but Matthew claimed that the distinction between intension
and extension was not applicable to a 4-d framework.  To avoid the
temporal issues, I mentioned hypothetical statements, which might
not refer to anything in actual space-time in any coordinate system.    (04)

PH> There is no 'now' in a 4-d universe.    (05)

I used the word 'now' because Matthew used it.  But strictly speaking,
there is no here or now in a 3-d universe.  The word 'here' and 'now'
are indexical terms that are always tied to a particular observer or
speaker.  In discussions of relativity in 4-d spaces, it is common
to talk about a different 'here' and 'now' for each observer.    (06)

PH> All of which is a lot easier in a 4-d framework.    (07)

I agree that many formulations are easier in a 4-d framework.    (08)

I like to compare the issues to the difference between Eulerian and
Lagrangian coordinates in fluid mechanics:    (09)

  1. In a Lagrangian representation, you can think of a sensor in
     a little boat that is flowing with with a packet of fluid and
     recording all the locations it passes.    (010)

  2. In an Eulerian representation, the observer watches from a fixed
     location as the fluid flows past.    (011)

Both representations are useful, and there are ways of transforming
one to the other.  But certain kinds of problems are easier to state
and solve in one or the other.  It's important to understand both
methods and the relationships between them.    (012)

PH> Of course not, but it does enable one to distinguish between
 > a description of change, and a changing description.  JFS seems
 > to be embedded in a framework which conflates these so badly that
 > the difference is invisible, which is MW's point.    (013)

First of all, Matthew extracted my comment from an earlier note
in which I explicitly said that every update to a set creates
a different set.  This issue is often obscured in programming
languages, in which a particular variable S represents a fluent,
whose values may be different sets at different points of time
during program execution.    (014)

Second, Matthew explicitly claimed that the distinction between
intension and extension did not apply to a 4-d description.  I
was trying to make the point that the distinction is independent
of coordinate system.    (015)

PH> JFS thinks that sets change, which is wrong.    (016)

You know that I wouldn't even dream such a thing.  I admit that
I should have introduced the terminology of fluents in order to
clarify the common ways of talking.  My comment about the assembly
line should have been elaborated with more commentary, but I was
trying to be brief.    (017)

John    (018)

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