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

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Sun, 16 Jun 2002 15:04:39 +0100 (BST)
To: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
cc: www-webont-wg@w3.org
Message-ID: <Pine.HPP.3.96.1020616145402.1188B-100000@steptoe.hpl.hp.com>



On Fri, 14 Jun 2002, Jos De_Roo wrote:

> >
> > g4:
> > eg:p rdf:type rdf:Property .
> >
> > g5:
> > rdf:type rdf:type rdf:Property .
> >
> > Now, g1, g2 and g3 are also unproblematic and so in W, hence g0 is
> required
> > to owl-entail g1, g2 and g3.
> > However, g4 and g5 may be problematic, since the first assumes that
> > properties are in the domain of discourse and the second assumes that
> > class-membership is in the domain of discourse.
> 
> For g4, how could eg:p (used in g0) NOT be in the domain of discourse?
> (I want to say anything about anything)
> It's (almost) cast in stone in http://www.w3.org/TR/rdf-mt/
> as
> [[[
>        if E contains   then add
> rdf1   xxx aaa yyy .   aaa [rdf:type] [rdf:Property] .
> ]]]
>     -- http://www.w3.org/TR/rdf-mt/#rdf_entail
> 


Sorry for slowness in replying.

Of course, for RDF MT, you are right. Properties are in the
domain of discourse. The idea behind this suggestion is that
the relationship (for OWL 1.0) between OWL semantics and
RDF semantics is merely to do with inference; and not to do
with the domain of discourse.

This corresponds to the usual disclaimer in a spec that 
while the spec provides algorithms any other algorithms that
exhibit the same behaviour are conformant implementations.

Hence OWL semantics can monotonically conform with RDF semantics
on a restricted subset of RDF graphs as long as all RDF(S)
entailments are also OWL entailments on that subset.

If, as it appears to be, it is easier to not have properties in
the domain of discourse for OWL then let's not. But since they are
in RDF's domain of discourse we find OWL and RDF semantics diverge
(unpleasantly) and so this impacts  the choice of the
subset over which OWL semantics is an extension of RDF semantics.

This is intended as a fudge to allow OWL to procede without
a layering solution and to permit a longer discussion of
layering issues in a more appropriate forum.

Jeremy
Received on Sunday, 16 June 2002 10:05:12 GMT

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