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Re: [ontolog-forum] Thing and Class

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Sat, 13 Sep 2008 09:53:28 -0400
Message-id: <48CBC5D8.4080605@xxxxxxxxxxx>
Dear Matthew,    (01)

Just a few clarifications:    (02)

[MW] I prefer not to use modal logic.    (03)

Since I am working on computational linguistics, I need some
way of translating the words "can" and "must" into some
logical representation.  But to do the reasoning, I prefer
to work with the explicit laws (constraints) and facts (data)
using some version of first-order logic.    (04)

JFS>> Most AI work with "possible worlds" is actually based on
 >> metalevel reasoning about sets of propositions that describe
 >> those worlds, not with the worlds themselves.    (05)

[MW] Actually, I am more interested in populating those worlds with
actual plans, than I am with reasoning, and then tracking how well
they match to reality.    (06)

Most of the plans we develop or use aren't in those worlds.  They're
in the world we live in (or in our computers, which are also in our
world), but they refer to hypothetical things in those worlds.    (07)

JFS>>  Nobody actually implements "possible worlds".    (08)

[MW] What do you mean by this?  For example, I expect to have an
object that represents a particular possible world (well more properly
a universe) for all the time that it exists, and then to have objects
in the world as spatio-temporal parts of it. How does this fit with
what you mean?    (09)

What I meant is that we don't build physical replicas.  We might
have physical signs, such as a marks on paper or in a computer,
that refer to those worlds and hypothetical things in them.
Our reasoning and computation manipulate those marks in order
to draw conclusions about what could, would, or should happen
in those hypothetical worlds.    (010)

John    (011)

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