W3C home > Mailing lists > Public > www-rdf-logic@w3.org > November 2000

Re: Equality and subclass axioms

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 29 Nov 2000 16:23:48 -0600
Message-Id: <v0421010eb64b31a277d3@[205.160.76.86]>
To: Graham Klyne <gk-lists@dial.pipex.com>
Cc: www-rdf-logic@w3.org
>At 01:34 PM 11/26/00 -0600, pat hayes wrote:
>>Oh yes it does. It arises if we allow disjunctions (which are 
>>logically equivalent to implications, as Im sure you know) and 
>>negations; it arises, in fact, whenever it is possible to express 
>>any kind of contradiction. The only way to avoid it is to make it 
>>impossible for anyone to ever disagree with anyone else, by for 
>>example only allowing positive logic (no negations.) The problem 
>>with logics this weak is that it is very difficult to draw useful 
>>conclusions in them.
>
>I've been cogitating a little about a related issue.  Would you 
>accept a rewording of the final sentence above:
>
>  The problem with logics this weak is that they are very limited in the
>  range of useful conclusions that can be drawn.
>
>?
>
>I think there are _some_ useful conclusions to be drawn from logics 
>without negation, etc.

Yes, I would accept that rewording. You are right, there are some.

Pat Hayes

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Received on Wednesday, 29 November 2000 17:22:25 UTC

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