CODEWITHSUNDEEP
sparqldbpedia
gaurav jain
gaurav jain

Reputation: 1355

Dbpedia does not return full results

Beginner in DBPedia/SPARQL/Semantic data. I ran following queries to "find out the sport for each athlete"

select ?athlete ?sport where 
{
   ?athlete rdf:type <http://dbpedia.org/ontology/Athlete>.   #query1
   ?athlete dbpedia2:sport ?sport                             #query2
}

It does give results but not the full set that I am looking for. "query1" by itself returns more athletes but combined with "query2", I get a lot less resultset.

Please explain the discrepancy. Am I missing something? Whats the alternative?

Regards

Upvotes: 2

Views: 342

Answers (1)

Lev Khomich
Lev Khomich

Reputation: 2247

Your query selects all athlete nodes which have both rdf:type and dbpedia2:sport properties. You can use optional clause to retrieve nodes even if some property isn't bound. For example:

select ?athlete ?sport where {
    ?athlete rdf:type <http://dbpedia.org/ontology/Athlete>. #query1
    optional {?athlete dbpedia2:sport ?sport} #query2
}

Better way to get sport:

select ?athlete ?type where {
    ?athlete rdf:type <http://dbpedia.org/ontology/Athlete>.
    optional {
        ?athlete rdf:type ?type.
        ?type rdfs:subClassOf <http://dbpedia.org/ontology/Athlete>
    }
}

Upvotes: 3

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