Cassio, The short answer to your question (as I understood it) is that you could not issue such a query to the dbpedia sparql endpoint by itself. Somehow you would need to get access to an endpoint that contains both the freebase data as RDF and the mappings that Paul discusses here in order to run your query.
Please correct me if I am wrong! -Ben -----Original Message----- From: Paul Houle [mailto:[email protected]] Sent: Monday, June 21, 2010 10:56 AM To: cassio steel Cc: [email protected] Subject: Re: [Dbpedia-discussion] interrogating freebase and dbpedia from the same query cassio steel wrote: > Hello everyone. > I wonder whether I can run a sparql query which involves freebase, > from dbpedia sparql endpoint, using linked data. > For instance, may I retrieve some information about something from > dbpedia and other informations about the same thing from freebase, on > the same query from the dbpedia sparql end-point? > Well, there's one question here: "do you want the right answers?" I suppose that somebody could extract RDF statements out of freebase, load them into the same graph as dbpedia, and then use the published dbpedia <-> freebase owl:sameAs statements to map them together. If you did that, AND IF YOU CHECKED THE VALIDITY OF YOUR ANSWERS (which is NOT standard practice in semweb research, so far as I can tell) you'd note that the mappings are horribly wrong. The dbpedia <-> freebase mappings are so bad that they'll substantially change the semantics of dbpedia, even if you never load anything from Freebase; for instance, you can easily infer bizzare and incorrect statements such as dbpedia:Area_11 owl:sameAs dbpedia:Japan. it just isn't so, and results in the inference of millions of extra bogus triples, for instance, dbpedia:Japan rdfs:Label "Area 11"@en . I found this out when I was trying to establish a 1-1 relationship between some set of entities and iso codes for countries and second-level administrative division (... needed that because 90% of the "Countries" in the dbpedia ontology are fictional or not going concerns, i.e. "Austria-Hungary", "The Republic Of Atlantis", etc.) The ISO codes are in freebase, but the dbpedia <-> freebase mappings were so bad that I decided to give up on Dbpedia as a "primary reference", use Freebase and just cherry pick selected information items out of it. To be fair, I do have freebase <-> dbpedia mappings that are much better quality than the ones on the dbpedia site and the time might be right to publish them. The issue here is that there are two ways you can construct said mapping: (i) when fb items are created from wikipedia extraction, the wikipedia page id is recorded in freebase; these can be looked up against the "page Id" file from dbpedia. (ii) freebase contains a set of "keys" that name items in freebase; some of these keys are in the wikipedia namespace, and those can be mapped to dbpedia pretty easily. The published mappings look a lot like (ii); the keys are really promiscuous and link up things that are at most circumstantially related -- I'd hate to say that they're useless, because they're not, but the the mapping is too indiscriminate for owl:sameAs to be appropriate. When I used methodology (i) I found about half as many mappings. ------------------------------------------------------------------------------ ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo _______________________________________________ Dbpedia-discussion mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/dbpedia-discussion ------------------------------------------------------------------------------ ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo _______________________________________________ Dbpedia-discussion mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/dbpedia-discussion
