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Re: OWL Lite semantics

From: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
Date: Tue, 10 Dec 2002 00:58:49 +0100
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: Jim Hendler <hendler@cs.umd.edu>, Jeremy Carroll <jjc@hplb.hpl.hp.com>, www-webont-wg@w3.org
Message-ID: <OF5C919B38.89BB1AC0-ONC1256C8A.008286B7-C1256C8A.0083BC5D@agfa.be>


> > > Jeremy's proposal is that OWL Lite be both a syntactic and *semantic*
> > > "subset" (I use the expression loosely in this case) of OWL DL.
> >
> >
> > Nothing loose there ...
> > my proposal views a language as a pair:
> >
> > < A set of documents,
> >    an entailment relationship over the set >
> >
> >
> > Then
> >
> > OWL DL is a sublanguage of OWL full
> >    in that the set of OWL DL documents is a subset of the set of OWL
Full
> > documents
> >    the OWL DL entailment relationship is a subset of the OWL Full
> > entailment relationship (specifically the restriction of OWL Full
> > entailment to the set of OWL DL documents).
>
> Yes, so an OWL DL reasoner, when asked about entailment between two
> documents will either give the *SAME ANSWER* as an OWL full reasoner,
> or will refuse to answer on the grounds that the document is outside
> the subset it can handle.
>
> >
> > My OWL Lite is a sublanguage of OWL Full
> >    the set of OWL Lite documents is a subset of the set of OWL Full
documents
> >    the OWL Lite entailment relationship is also a subset of the OWL DL
> > entailment relationship.
>
> You have omitted the crucial fact that, in the case of your OWL Lite
> proposal, the entailment relationship is NOT the OWL full entailment
> relationship restricted to the set of OWL Lite documents, but is
> (probably) a subset of this set (intuitively tempting to believe that
> this is the case, but it remains to be proved). Thus, OWL Lite
> reasoners and OWL DL/full reasoners would give *DIFFERENT ANSWERS* to
> questions about entailment w.r.t. OWL Lite documents.
>
> This is *NOT* simply incompleteness w.r.t. OWL DL/full semantics,
> because a Lite reasoner would be entitled to answer NO to a question
> about entailment when the correct DL/full answer is YES.

Fine, then it should not say NO, but
  refuse to answer on the grounds
  that the *entailment relationship*
  is outside the subset it can handle.
(to slightly twist your words)
and that's just incompleteness

-- ,
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Monday, 9 December 2002 18:59:28 GMT

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