- From: Michael Schneider <schneid@fzi.de>
- Date: Wed, 21 Nov 2007 18:16:17 +0100
- To: "Jeremy Carroll" <jjc@hpl.hp.com>
- Cc: "Owl Dev" <public-owl-dev@w3.org>, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Thanks, Jeremy! Related to the "non-empty universe" question, I have just read your new Issue 73 in the OWL-WG list: ISSUE-73 (infinite universe): REPORTED: Should owl:Thing be necessarily infinite? http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0396.html In OWL 1.0 Full, the universe is necessarily infinite. In OWL 1.0 DL, the universe is required to be non-empty. The compatibility between OWL Full and OWL DL could be enhanced by requiring the universe to be infinite in both cases. As a public comment again :): I remember that I have read somewhere (don't know where at the moment) that people sometimes restrict owl:Thing to be a finite enumeration of certain instances: EquivalentClasses(owl:Thing oneOf(x1 ... xN)) The idea, AFAIR, was that by this people can approximate closed world scenarios in connection with OWL (owl:Thing would then for instance stand for a concretely given database, i.e. a finite(!) set of data entries). If this should really be a reasonable pattern (I never used it, so I cannot tell for sure), wouldn't it be a problem to demand that the OWL-DL-1.1 universe should be infinite? Cheers, Michael >-----Original Message----- >From: Jeremy Carroll [mailto:jjc@hpl.hp.com] >Sent: Wednesday, November 21, 2007 3:07 PM >To: Michael Schneider >Cc: Owl Dev; Peter F. Patel-Schneider >Subject: Re: Defining cross products in OWL-1.1 > >OWL does not permit an empty universe. > >Michael Schneider wrote: > >> >> Task: For given classes A and B give an OWL-1.1 axiom set, by which a >> property pAXB is specified to be equivalent to the cross >product A X B. >> >> Solution: >> >> (A0) ClassAssertion(w owl:Thing) >> (A1) SubClassOf(A ObjectHasValue(pA w)) >> (A2) SubClassOf(B ObjectHasValue(pB w)) >> (A3) SubObjectPropertyOf( >> SubObjectPropertyChain(pA InverseObjectProperty(pB)) >> pAXB ) >> (A4) ObjectPropertyDomain(pAXB A) >> (A5) ObjectPropertyRange(pAXB B) >> > >> >> There are a several points which need some further discussion here: >> > >> Second: About the "glue instance" w. The only real >requirement was that >> there is /some/ instance in the universe (denoted by >owl:Thing), because >> this alone suffices to use such an instance for glueing pA and pB^-1 >> together in the above sub role chain. Even the two >'ObjectHasValue' axioms >> do not seem to put a dangerous restriction on 'w'. So it seems to be >> possible for instance that I can reuse w for specifing the >"glue instance" >> of a second role rCXD for other classes C and D without any >problem. Also, >> if w occurs in other axioms of the ontology, this shouldn't be a big >> problem, because it does not affect the fact that such a w >/exists/. Of >> course, it must not happen that in the ontology's remaining >axioms one of >> the "helper roles" 'pA' and 'pB' appears, but this can >always be avoided in >> practice AFAICS. So the only thing which might be considered >to be at least >> a /theoretical/ problem is that it will not be possible >anymore to interpret >> such an OWL ontology over the /empty/ universe. But in >practice, no one will >> really care about this lacking, and I am not even certain if >doing so is >> allowed at all in OWL. >> > >In OWL 1.0, the universe is restricted to have at least one member. > >http://www.w3.org/TR/owl-semantics/direct.html#3.1 >[[ >EC(owl:Thing) = O ⊆ R, where O is nonempty and disjoint from LV >]] > >I would expect this restriction to carry through to the next >version of OWL. > >Jeremy > > > > > > -- 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 Stiftung des bürgerlichen Rechts Az: 14-0563.1 Regierungspräsidium Karlsruhe Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi Studer Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
Received on Wednesday, 21 November 2007 17:16:30 UTC