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Re: yet another non-entailment (was Re: another revision of semantics document)

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 22 Aug 2002 14:46:28 +0100 (BST)
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: phayes@ai.uwf.edu, <www-webont-wg@w3.org>
Message-ID: <Pine.LNX.4.44.0208221429330.732-100000@galahad.cs.man.ac.uk>

I see some other (and to my mind even more fundamental) problems with this
proposal, and indeed with the whole "strong layering" idea. In particular,
the domain of discourse now necessarily contains various syntactic
artifacts that place some lower bound on its cardinality (possibly
infinite if we need comprehension).

This has a number of strange (and undesirable) effects. E.g., an ontology
containing the single axiom "Thing subclassOf (oneOf x)" (i.e., "x is the
only object in the world"  - a seemingly harmless statement) no longer has
any model.

Moreover, negation behaves strangely, because the negation of a "normal"
class contains all the syntactic "junk". This can again lead to strange 
inferences regarding the cardinality of classes.

Regards, Ian

On Wed, 21 Aug 2002, Peter F. Patel-Schneider wrote:

> John rdf:type owl:Thing .
> does not entail
> John rdf:type _:x .
> _:x owl:oneOf _:l .
> _:l owl:first John .
> _:l owl:rest owl:nil .

Ian Horrocks, Department of Computer Science,
University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Tel: +44 161 275 6133  Fax: +44 161 275 6211  Email: horrocks@cs.man.ac.uk
WWW: http://www.cs.man.ac.uk/~horrocks
Received on Thursday, 22 August 2002 09:42:33 UTC

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