- From: Michael Schneider <schneid@fzi.de>
- Date: Sat, 10 Nov 2007 11:50:48 +0100
- To: "Owl Dev" <public-owl-dev@w3.org>
- Cc: <alanruttenberg@gmail.com>
[Comment to OWL-WG discussion; CC'ed to involved WG members] Hi OWL-DEV list! I just found the following mail by Alan Ruttenberg on the OWL-WG list Re: ISSUE-3: REPORTED: Lack of anonymous individuals http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0214.html where he notices that bNodes are used in both the RDF mapping for OWL-1.0 and for OWL-1.1, and Alan asks what consequences it would have to drop bNodes from OWL-DL. Alan's question brought a related question up to my mind, which I present below. BTW: No one has to read the complete thread there about "anonymous individuals", my question doesn't depend on this discussion and is self-contained. Now my question: OWL-DL-1.0 allows me to state that a class :C is the intersection of classes :D1 and :D2. When I have to write such an axiom in RDF syntax, I generally do it by means of Turtle in the following way: (1) :C a owl:Class . (2) :D1 a owl:Class . (3) :D2 a owl:Class . (4) :C owl:equivalentClass [ a owl:Class ; owl:intersectionOf ( :D1 :D2 ) ]. where (4) is just a convenient Turtle shortcut for writing (4a) _:X a owl:Class . (4b) :C owl:equivalentClass _:X . (4c) _:X owl:intersectionOf ( :D1 :D2 ) . So we actually have a bNode "_:X" in our OWL-DL-1.0 ontology above. Now OWL-DL-1.0 has both a "direct semantics" and an "RDF compatible semantics", and for the DL sublanguage of OWL-1.0 they are intended to be equivalent. This allows me to interprete the above OWL-DL-1.0 ontology by using RDF compatible OWL-DL semantics. And because bNodes are interpreted in RDF as /existential variables/, the meaning of axiom (4) is (in natural language): "There exists some class ?X, to which class :C is equivalent, and which is the intersection of the classes :D1 and :D2." So this statement is actually a quantification about a /class/ variable. But I thought that OWL-DL was a First Order Logic dialect, where all universal and existential quantifications must be asserted about /individual/ variables only? And in an RDF-mapped OWL-DL-1.0 ontology, I am not allowed to regard such a class variable as an individual variable, because in OWL-DL the OWL universe is strictly separated. So this looks to me like a problem for the intended equivalence between Direct Semantics and RDF Compatible Semantics for OWL-DL. There is certainly some misunderstanding on my side, but maybe someone can clarify? 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 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 Saturday, 10 November 2007 10:51:10 UTC