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Re: layering (5.3, 5.10): Sardinia compromise?

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 17 Jun 2002 06:07:13 -0400
To: jjc@hpl.hp.com
Cc: www-webont-wg@w3.org
Message-Id: <20020617060713W.pfps@research.bell-labs.com>

From: "Jeremy Carroll" <jjc@hpl.hp.com>
Subject: layering (5.3, 5.10): Sardinia compromise?
Date: Fri, 14 Jun 2002 15:23:09 +0200

[...]

> In essence [my proposal] would be to make OWL a weak semantic extension of
> a subset of RDF.
> 
> I will unpack that a little and then give an example:
> 
> RDF defines a large set of RDF graphs; for OWL we syntactically define a
> subset W (or alternatively its complement). OWL then only applies to graphs
> in W. We choose fairly arbitrarily what goes in W and what doesn't. The main
> idea is the things that we can agree on go in W, and those things we
> disagree about don't.

OK, this sounds good.  

I hereby propose that any triple that contains any of the reserved
vocabulary in the RDF MT document not be in W.

By your rules, my proposal ensures that these triples will not be in W.

[...]

> The "weak semantic extension" is intended to mean, that as long as we
> restrict ourselves to W then whenever g [RDFS]-entails h, then g [OWL]-entails
> h. However we are not requirng any other relationship between the semantics.
> In particular if properties in the domain of discourse or type as a property
> cause problems for OWL semantics then we do not require OWL semantics to do
> that just because the RDF model theory is constructed like that. We only
> require the externally visible behaviour (i.e. entailment) to conform with
> RDF.

Already W is restricted so that RDFS-entailment on the powerset of W is the
identity relationship.  As any entailment had better be reflexive, there
are no longer any restrictions on OWL entailment.  In essence there is no
relationship whatsoever between OWL entailment and RDFS entailment.

[...]

> This [proposal] would involve indicating to the coordination group that we
> had postponed the issue, and they would need to ensure the relevant people
> do continue to move the layering problem forward; but after OWL 1.0 is
> cooked.

OK, go for it.

> Jeremy

peter

PS:  This *is* a serious response to Jeremy's proposal.

PPS: It *might* be possible to expand W to allow some RDF-related
vocabulary, and thus place some restrictions on OWL entailment, but each
expansion would require an analysis to ensure that no problems are
introduced.
Received on Monday, 17 June 2002 06:07:24 GMT

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