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RE: Some basic questions about OWL-Full

From: Giorgos Stoilos <gstoil@image.ece.ntua.gr>
Date: Thu, 25 Oct 2007 10:15:54 +0300
Message-Id: <200710250715.l9P7FsR3015262@manolito.image.ece.ntua.gr>
To: "'Pat Hayes'" <phayes@ihmc.us>, "'Michael Schneider'" <schneid@fzi.de>
Cc: <public-owl-dev@w3.org>, "'Peter F. Patel-Schneider'" <pfps@research.bell-labs.com>, <jjc@hpl.hp.com>

Hi all,

Does this question/discussion apply also to RDF or only to OWL Full. If so
why is there a difference?

Best,
Giorgos

> -----Original Message-----
> From: public-owl-dev-request@w3.org [mailto:public-owl-dev-request@w3.org]
> On Behalf Of Pat Hayes
> Sent: Wednesday, October 24, 2007 1:26 AM
> To: Michael Schneider
> Cc: public-owl-dev@w3.org; Peter F. Patel-Schneider; jjc@hpl.hp.com
> Subject: RE: Some basic questions about OWL-Full
> 
> 
> >Pat Hayes wrote:
> >
> >>>From: Pat Hayes <phayes@ihmc.us>
> >>>Subject: Re: Some basic questions about OWL-Full
> >>>Date: Tue, 23 Oct 2007 08:58:28 -0500
> >>>
> >>>>
> >>>>   >Peter F. Patel-Schneider wrote:
> >>>>   >>
> >>>>   >>For homework:  Is EquivalentProperties(owl:sameAs
> >>owl:differentFrom)
> >>>>   >> 	 	       itself inconsisten?
> >>>>   >>
> >>>>   >
> >>>>   >I'm afraid I'm several years' late on my (easier) homework of:
> >>>>   >    Is (*empty*) itself inconsistent?
> >>>>
> >>>>   Yes, in RDF (and conventional FOL). This is the
> >>>>   only assumption of Tarskian semantic theory, that
> >>>>   there is something in the universe. One can build
> >>>>   a 'free' logic which allows an empty universe,
> >>>>   but then its proof theory can't have the usual
> >>>>   rules of instantiation and generalization, which
> >>>>   allow the inferences
> >>>>
> >>>>   (forall (x) (foo x))  |==   (foo A) for some
> >>>>   'new' name A |==  (exists (x)(foo x))
> >>>>
> >>>>   Pat
> >>>
> >>>I think Jeremy meant an empty KB, i.e., whether OWL Full is trivial or
> >>>not.
> >>
> >>Ah, I see. Sorry. Yes, that question amounts to
> >>whether the OWL semantic conditions are
> >>internally consistent when transcribed into
> >>common logic (or FOL using the holds/app style).
> >>Good question!
> >
> >Hm, seems to me that I did not understand neither Jeremy, nor Peter, nor
> >you. :) What is meant by "whether OWL Full is trivial or not"?
> 
> "Trivial" in this context means that there would
> be no OWL-Full interpretations which satisfy
> anything, so everything would be OWL-Full
> unsatisfiable. Put another way, the OWL-Full
> semantic conditions would be internally
> contradictory.
> 
> >  Is this the
> >question about whether empty OWL-Full ontologies are inconsistent or not?
> 
> That is another way to put it, yes.
> 
> >I.e. whether an empty OWL-Full ontology entails contradictory statements?
> 
> And that is another, yes.
> 
> >But if I have some arbitrary non-empty ontology O := {A1,...,An}, then O
> >contains the empty ontology as a sub-ontology. So I would assume that
> every
> >statement which is entailed by the empty OWL-Full ontology will also be
> >entailed by O itself. And if the empty OWL-Full ontology would entail
> >contradictory statements, then /every/ OWL-Full ontology would entail
> >contradictory statements, and then OWL-Full semantics would be totaly
> >broken!
> 
> Quite. Which is what Peter meant by "trivial". I
> am confident that this is not the case, but even
> if it were I would say they would indeed be
> broken, but because in that case the OWL semantic
> conditions were themselves broken. And not
> necessarily totally, since the next task would be
> to see how to weaken them so that they weren't
> broken. IMO they are too strong in some ways in
> any case, e.g. the intensional view of classes
> seems better than the extensional one, c.f.
> terHorst's version of OWL.
> 
> >Is it this what you (Pat) mean by "whether the OWL semantic
> >conditions are internally consistent..."?
> 
> Yes.
> 
> Pat
> 
> >
> >Cheers,
> >Michael
> >
> >--
> >Dipl.-Inform. Michael Schneider
> >FZI Forschungszentrum Informatik Karlsruhe
> >Abtl. Information Process Engineering (IPE)
> >Tel  : +49-721-9654-726
> >Fax  : +49-721-9654-727
> >Email: Michael.Schneider@fzi.de
> >Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555
> >
> >FZI Forschungszentrum Informatik an der Universität Karlsruhe
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> 
> 
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Received on Thursday, 25 October 2007 07:19:02 GMT

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