- From: Michael Schneider <schneid@fzi.de>
- Date: Thu, 18 Nov 2010 00:27:51 +0100
- To: "Rinke Hoekstra" <hoekstra@few.vu.nl>, "Pavel Klinov" <pklinov@cs.man.ac.uk>
- Cc: <public-owl-dev@w3.org>, "Pat Hayes" <phayes@ihmc.us>, "Marco Colombetti" <colombet@elet.polimi.it>
Hi again! I wrote earlier this day: >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! To make sure that this example is not just an "outlier", I did some more checking by using the SPARQL endpoint to DBPedia at <http://dbpedia.org/sparql> with the following queries: Query 1: """ SELECT DISTINCT ?c WHERE { ?c owl:sameAs ?d . ?x rdf:type ?c . } """ Query 2: """ SELECT DISTINCT ?d WHERE { ?c owl:sameAs ?d . ?x rdf:type ?d . } """ Query 3: """ SELECT DISTINCT ?c, ?x WHERE { ?c owl:sameAs ?d . ?x rdf:type ?c . } """ Query 1 asks for all DBPedia concepts having rdf:type-based instances in the DBPedia knowledge base and for which there is an owl:sameAs-link to some other concept (not necessarily from DBPedia). Query 2 differs from Query 1 in that the concepts having rdf:type-instances are being owl:sameAs'ed from DBPedia concepts, but might not be DBPedia concepts themselves. So these two queries ask for concepts (internal or external to DBPedia) that are used dually as classes (via rdf:type) and individuals (via owl:sameAs) within DBPedia. Query 3 is like Query 1, but also asks for the instances of the identified dual-use concepts. Results: Query 1 returned 133 concepts, all of them being classes from the dbpedia-owl ontology. Query 2 returned 1061 hits, all of them happened to be concepts from OpenCyc. Query 3 returned exactly 2000 hits, which is probably due to an internal result set restriction of the query endpoint. A closer look revealed that all returned instances belonged to the same dual-use concept, namely the first concept being returned by Query 1 ("dbpedia-owl:Actor"). So the true size of the result set for Query 3 is probably much larger. To summarize, DBPedia "puns" at least ca. 1200 concepts, and these dual-use concepts have at least 2000 instances, probably much more. I think this strengthens my earlier claim that the existing semantic difference between OWL 2 DL punning and RDF(S)/OWL-Full "true" metamodeling is practically sensible, since for each instance of a dual-use concept OWL Full will allow to infer a second instance relationship, which is not provided by OWL 2 DL reasoning. It would be interesting to extend this investigation in a more sophisticated way (e.g. not only using owl:sameAs-links) to a much larger fraction of the whole LOD cloud. Best, 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 =======================================================================
Received on Wednesday, 17 November 2010 23:28:26 UTC