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Re: SEM: "natural" entailments

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 6 Sep 2002 00:25:09 -0700
Message-Id: <p05111b0db99e03bda60e@[65.212.118.251]>
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Cc: www-webont-wg@w3.org

>
>I don't see any a priori reason why set theoretic truths have any 
>greater need to be included in Owl than arithmetic truths.
>  Both set thery and arithmetic are really somebody else's concern.
>
>
>Jeremy

One of the things that is so misleading about the entire 
description-logic way of thinking is that it treats some *logical* 
truths as set-theoretical truths. Look, to infer

John is a student and John is an employee .

from

John is a student.
John is an employee .

is a *logical* matter. It has to do with the meaning of 'and'. It has 
nothing to do with sets or classes or any of this paraphanalia. But 
in the warped world of description logics, to assert a simple 
conjunction requires us to invent a conjunctive class (an 
intersection) and say that John is in it.  The reason for this 
intellectual warping goes back to an influential, but I think 
perverse, publication by Ron Brachman about 20 years ago, which 
invented the distinction between two 'kinds' of reasoning: that to do 
with meanings, which is supposed to be done in one place (the 
'A-box') and the other to do with facts, supposed to be done 
elsewhere (the 'T-box'). The same kind of distinction is sometimes 
expressed by the distinction between 'data' (mere facts, assertions 
which are true) and 'meta-data' (schemas; things that 'define the 
meanings' of the terms used in the facts.)  None of these 
distinctions make any logical sense or have even the slightest basis 
in semantics: they are pragmatic distinctions invented to facilitate 
effective use of database technology with simple reasoners. By using 
them as the basis for the *semantic* framework of the semantic web we 
are making the entire future of the Web hostage to the intellectual 
apparatus of a technology designed for the efficient use of 
regularized, commercial databases, not to the emergent world of a 
social semantic web.  We should be focussing on the issues that will 
matter, not on how to transfer old technology into a world where it 
is probably going to be largely irrelevant.

Pat
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Received on Friday, 6 September 2002 04:58:19 GMT

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