- From: Pavel Klinov <pklinov@cs.man.ac.uk>
- Date: Wed, 17 Nov 2010 16:21:31 +0000
- To: Michael Schneider <schneid@fzi.de>
- Cc: Rinke Hoekstra <hoekstra@few.vu.nl>, public-owl-dev@w3.org, Pat Hayes <phayes@ihmc.us>, Marco Colombetti <colombet@elet.polimi.it>
On Wed, Nov 17, 2010 at 3:56 PM, Michael Schneider <schneid@fzi.de> wrote: > Hi Rinke, Pavel! > > I have to admit that I did not exactly understand what Pavel meant here. > > Or was it meant that it would be confusing if for a class having a class > property its /instances/ would not inherit that property? That's in fact > also not in OWL Full! But I would never expect such inheritance from the > class level to the instance level, at least not in general. The property > belongs to the class, not to its instances. (However, if someone really > wanted this behavior for a specific property :p, he could write in OWL 2 > Full: ":p owl:propertyChainAxiom ( rdf:type :p ) .") Yeah, this is what I meant while I now 100% agree that this wasn't a good example. I was merely trying to say that use of punning requires understanding of the difference between properties of the class and the properties of its instances. I have heard people talking about "properties of the class" when those were just existential restrictions (A subclassof p some B). Your example at the bottom is a much better one. Thanks, Pavel >> >>Hm, but for all practical purposes they *are* the same thing, they are >>just interpreted differently dependent on context. > > For individual/class punning, OWL 2 DL interprets the same name in one case > as an individual of the domain of discourse, and in the other case as a > subset of the domain of discourse. This is a big difference from a semantics > point of view. Now, OWL 2 Full interprets both occurrences as individuals, > in fact as the same individual. The only difference is that in the case of > class usage, an additional feature of that individual is taken into account, > namely its associated class extension, which is a subset of the domain of > discourse. But one definitely talks about one and the same individual in > both cases. And, as you can see in the example at the end of my post, this > may indeed lead to practically sensible differences. > >>OWL 2 DL reasoners >>may separate these contexts for efficiency purposes, but an RDFS/OWL 2 >>Full reasoner or RDF query engine won't. > > It's not only a matter of efficiency in the case of OWL 2 DL reasoners. They > must not provide those inferences that you would expect from treating the > two occurrences as the same thing, otherwise they would become unsound. See > below for an example. > >>This is fine if you ask me... I have yet to come across a situation >>where this potential confusion had any practical consequences. > > You can see the difference in the LOD cloud. For example, OpenCyc includes > the concepts "country" and "England", where "England" is an instance of > "country", and where "country" is asserted to be equal to DBPedia's > "Country" concept (the equality link is being created in both knowledge > bases): > > opencyc:country owl:sameAs dbpedia:Country . > opencyc:England rdf:type opencyc:country . > > where > > opencyc:country := > <http://sw.opencyc.org/concept/Mx4rvViIeZwpEbGdrcN5Y29ycA> > opencyc:England := > <http://sw.opencyc.org/concept/Mx4rvViWaZwpEbGdrcN5Y29ycA> > dbpedia:Country := <http://dbpedia.org/resource/Country> > > An OWL Full reasoner and many existing RDF rule reasoners (including all > reasoners implementing the OWL 2 RL/RDF rules) will infer from the equality > link that > > opencyc:England rdf:type dbpedia:Country . > > holds. OWL 2 DL reasoners, on the other hand, must not infer this in order > to avoid to become unsound. And, in fact, Pellet and Hermit correctly (from > their perspective) classify this as a non-entailment. > > With owl:sameAs links being a big topic in the LOD world, I'd say this is a > practically relevant difference! > >>Cheers, >> >>Rinke > > Cheers, > Michael > > -- > Dipl.-Inform. Michael Schneider > Research Scientist, Information Process Engineering (IPE) > Tel : +49-721-9654-726 > Fax : +49-721-9654-727 > Email: michael.schneider@fzi.de > WWW : http://www.fzi.de/michael.schneider > ======================================================================= > 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, RP Karlsruhe > Vorstand: Prof. Dr.-Ing. Rüdiger Dillmann, Dipl. Wi.-Ing. Michael Flor, > Prof. Dr. Dr. h.c. Wolffried Stucky, Prof. Dr. Rudi Studer > Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus > ======================================================================= > > -- cheers, --pavel http://www.cs.man.ac.uk/~klinovp
Received on Wednesday, 17 November 2010 16:22:04 UTC