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RE: Some basic questions about OWL-Full

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 25 Oct 2007 17:32:16 -0500
Message-Id: <p06230911c346c9204e32@[10.100.0.19]>
To: "Giorgos Stoilos" <gstoil@image.ece.ntua.gr>
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?

The question applies to any formalism, but it has 
been definitively answered for most formal logics 
in common use. The RDF semantics document answers 
it for RDF and RDFS, though as Peter notes one 
has to be careful when interpreting external 
specifications such as XMLSchema.

The reason OWL-Full is different from RDF is that 
OWL-Full (in fact, OWL) imposes a much larger and 
more complicated collection of semantic 
conditions than simple RDF does, so it is more 
work to demonstrate their internal consistency.

Pat

>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
>>  >Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
>>  >Tel.: +49-721-9654-0, Fax: +49-721-9654-959
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>>
>>
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Received on Thursday, 25 October 2007 22:32:34 GMT

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