- From: Michael Schneider <schneid@fzi.de>
- Date: Thu, 13 Dec 2007 09:51:44 +0100
- To: <pfps@research.bell-labs.com>, "Owl Dev" <public-owl-dev@w3.org>
- Cc: "Alan Ruttenberg" <alanruttenberg@gmail.com>, <ian.horrocks@comlab.ox.ac.uk>
[This is a comment to a discussion in the OWL-WG list; also posted to WG members involved] Hi Peter! Peter F. Patel-Schneider wrote on Fri, 07 Dec 2007 in <http://lists.w3.org/Archives/Public/public-owl-wg/2007Dec/0095.html> > Qualified Cardinalities in OWL 1.1 Full > > > Suppose that we want to keep the general flavour of the OWL Full > semantics *and* use the current OWL 1.1 mapping to RDF. What would > happen? > > > Here is an example of how the RDF mapping works (roughly). > > ObjectMaxCardinality(2 child) expands to: > > _:x rdf:type owl:Restriction > _:x owl:maxCardinality "2"^^xsd:nonNegativeInteger > _:x owl:onProperty child > > ObjectMaxCardinality(2 child Person) expands to: > > _:y rdf:type owl:Restriction > _:y owl:maxCardinality "2"^^xsd:nonNegativeInteger > _:y owl:onProperty child > _:y owl11:onClass Person > > Note especially that the first set of triples is a "subset" of the > second set. I think that this also introduces a problem when performing an inverse RDF mapping. Imagine you stream in an RDF serialization of an OWL ontology in order to map it into Functional Syntax. Assume further that at a certain point in the input stream you have found the following three triples: _:y rdf:type owl:Restriction _:y owl:maxCardinality "2"^^xsd:nonNegativeInteger _:y owl:onProperty child The problem is that you cannot tell for sure whether _:y denotes a "normal" cardinality restriction, or a QCR. You will only know for sure after you have scanned the /complete/ input stream, because only then you will know whether there is an additional triple _:y owl11:onClass Person or not. So you cannot start processing cardinality restrictions (and other parts of the ontology depending on them) until the whole ontology has been read in. I'm not sure, but hasn't it been one of the design goals for the new RDF mapping to have such kinds of problems eliminated? Esp., haven't there been people (implementors) asking for better streaming possibilities compared to what the OWL-1.0 RDF mapping provides? AFAICS, the problem demonstrated above only occurs with the RDF syntax of cardinality restrictions (both object and data). So if the WG regards this to be a real problem, then (as Alan already proposed) having a set of new properties like owl11:maxQualifiedCardinality should suffice to solve this problem. Cheers, Michael > > > The OWL 1.0 Full semantics says that the class extension of _:x is the > set of objects that are related to at most two objects via the property > extension of child. A similar-style OWL 1.1 Full semantics would say > that the class extension of _:y is the set of objects that are related > to at most two objects that belong to the class extension of Person via > the property extension of child. > > However, the OWL 1.1 Full semantics would then also include the OWL 1.0 > Full semantics. So, part of the meaning of the last four triples > (actually the first three of these four, but that doesn't matter) in OWL > 1.1 Full would be that the class extension of _:y would *as well* be the > set of objects that are related to at most 2 objects via the property > extension of child. > > So, if o is in the class extension of _:y then it is related to at most > two objects that belong to the class extension of Person via the > property extension of child *and* it is related to at most two objects > via the property extension of child. It is impossible to have a max-QCR > without this double meaning. > > > > peter -- 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 Thursday, 13 December 2007 08:52:01 UTC