- From: Michael Schneider <schneid@fzi.de>
- Date: Thu, 18 Nov 2010 09:04:16 +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! Some more observations below! >-----Original Message----- >From: public-owl-dev-request@w3.org [mailto:public-owl-dev- >request@w3.org] On Behalf Of Michael Schneider >Sent: Thursday, November 18, 2010 12:28 AM >To: Rinke Hoekstra; Pavel Klinov >Cc: public-owl-dev@w3.org; Pat Hayes; Marco Colombetti >Subject: RE: class and inviduals > >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. Having had a closer look at dbpedia-owl:Actor (http://dbpedia.org/ontology/Actor), which, as said above, has a large number of instances and for which there is a owl:sameAs-link to opencyc:actor, I could see that this concept is used in DBPedia as: (i) a sub-class of dbpedia-owl:Artist; (ii) a super-class of concepts, s.a. dbpedia-owl:VoiceActor; (iii) the domain of properties, s.a. dbpedia-owl:geminiAward. Again, the difference between OWL 2 DL punning and RDF(S)/OWL-Full metamodeling will be sensible, since in OWL 2 Full one will be able to infer corresponding (i) sub-class-, (ii) super-class-, and (iii) domain relationships also for opencyc:actor, which are not entailed in OWL 2 DL. I also found that OpenCyc maintains a rich multi-level metaclass hierarchy. For example, opencyc:actor (http://sw.opencyc.org/concept/Mx4rvVjaHZwpEbGdrcN5Y29ycA) is defined as an instance of opencyc:type_of_entertainer (http://sw.opencyc.org/concept/Mx4rvxw_ApwpEbGdrcN5Y29ycA). The latter contains many other instances, such as opencyc:magician, opencyc:DJ and opencyc:clown, all of them having instances themselves, e.g. David Copperfield, D.J. Yella, and Herschel Krustofsky, respectively. Further, the metaclass opencyc:type_of_entertainer is itself an instance of opencyc:faceting_collection_type (http://sw.opencyc.org/concept/Mx4rvprlOZwpEbGdrcN5Y29ycA), which again is an instance of opencyc:type_of_collection_type (http://sw.opencyc.org/concept/Mx4rviPYH5wpEbGdrcN5Y29ycA). Interestingly, the latter concept is defined as an instance of itself, resembling the rdfs:Class/owl:Class loops in RDFS and OWL Full. 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 =======================================================================
Received on Thursday, 18 November 2010 08:04:53 UTC