# Re: T&A Boxes (was: RE: rdf as a base for other languages)

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 14 Jun 2001 15:14:48 -0500
Message-Id: <v04210103b74ec6fe8508@[205.160.76.189]>
To: Dave Reynolds <der@hplb.hpl.hp.com>

```>This is not my area so apologies if this is just noise ...
>
>When I recently attempted to explain description logics and T-box/A-box
>distinctions, a colleague likened them to the "=df" notation
>("definitionally equal") in mathematical logic.

and mathematics more generally. Right, it is widely used and seems
obviously clear in its meaning, but its very hard to actually come up
with any precise account of what the intuitive meaning amounts to,
that isnt the same as some kind of assertion.

>He suggested that, at
>least as logic used to be taught over here, you distinguished notationally
>between three forms of equality, viz. "equal in one particular model",
>"provably equal in all models, bi-equivalence" and "definitionally equal".
>The distinction between the latter two affects how you construct your
>proof theory

Really? If you could find me a pointer to a discussion of that I
would be interested to see it.

>even though for a given set of models

Well, for *any* set of models, I believe.

>you can't distinguish
>between a tautology and a definition. The "not allowed to be false" nature
>of T-boxes seems at least analogous.

Indeed, it seems very analogous.

Pat

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Received on Thursday, 14 June 2001 16:14:41 UTC

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