java - Cannot run particular SPARQL query using Apache Jena -


i'm trying run following query using apache jena

prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> prefix vrank:<http://purl.org/voc/vrank#> prefix dbp-ont:<http://dbpedia.org/ontology/> prefix dbp-prop:<http://dbpedia.org/property/> select distinct (sample(?slabel) ?sublabel) (sample (?plabel) ?predlabel) (sample(?olabel) ?oblabel) ?v  <http://dbpedia.org/>  <http://people.aifb.kit.edu/ath/#dbpedia_pagerank>  {     {   <http://dbpedia.org/resource/yao_ming> ?p ?o.         filter regex(str(?o),"http://dbpedia.org/resource","i").         filter (?p != dbp-ont:wikipagewikilink && ?p != <http://purl.org/dc/terms/subject>                  && ?p != dbp-prop:wikipageusestemplate && ?p != rdfs:seealso                  && ?p != <http://www.w3.org/2002/07/owl#differentfrom>                  && ?p != <http://dbpedia.org/ontology/wikipagedisambiguates> && ?p != <http://dbpedia.org/ontology/wikipageredirects> ).         optional {?o rdfs:label ?olabel. filter langmatches( lang(?olabel), "en" ). }.         optional {?p rdfs:label ?plabel. filter langmatches( lang(?plabel), "en" ).}.         optional {<http://dbpedia.org/resource/yao_ming> rdfs:label ?slabel. filter langmatches( lang(?slabel), "en" ).}.         optional {?o vrank:hasrank ?r. ?r vrank:rankvalue ?v}.     }  union     {   ?s ?p <http://dbpedia.org/resource/yao_ming>.         filter regex(str(?s),"http://dbpedia.org/resource","i").         filter (?p != dbp-ont:wikipagewikilink && ?p != <http://purl.org/dc/terms/subject>                  && ?p != dbp-prop:wikipageusestemplate && ?p != rdfs:seealso                  && ?p != <http://www.w3.org/2002/07/owl#differentfrom>                  && ?p != <http://dbpedia.org/ontology/wikipagedisambiguates> && ?p != <http://dbpedia.org/ontology/wikipageredirects> ).         optional {?s rdfs:label ?slabel.   filter langmatches( lang(?slabel), "en" ). }.         optional {?p rdfs:label ?plabel.  filter langmatches( lang(?plabel), "en" ).}.         optional {<http://dbpedia.org/resource/yao_ming> rdfs:label ?olabel. filter langmatches( lang(?olabel), "en" ).}.         optional {?s vrank:hasrank ?r. ?r vrank:rankvalue ?v}.     } } group ?v order desc (?v)

this query taken linksum project. runs fine(results) on dbpedia sparql endpoint no rows returned jena.

this code 

import org.apache.jena.query.queryexecutionfactory; import org.apache.jena.query.querysolution; import org.apache.jena.query.resultset; import org.apache.jena.query.resultsetfactory; import org.apache.jena.sparql.engine.http.queryenginehttp;          string query = "..."; // mentioned query         string dbpedia_sparql_service = "http://dbpedia.org/sparql/";         queryenginehttp qexec = (queryenginehttp) queryexecutionfactory.sparqlservice(dbpedia_sparql_service , query);         resultset resultset = null;         try {             resultset = qexec.execselect();             resultset = resultsetfactory.copyresults(resultset);         } catch (exception e) {             // report exception         } {             qexec.close();         }          string sublabel = "sublabel";         string predlabel = "predlabel";         string oblabel = "oblabel";         string vrank = "v";          if (resultset != null) {             while (resultset.hasnext()) {                 querysolution result = resultset.next();                 if (result != null) {                     system.out.println(sublabel);                     system.out.println(predlabel);                     system.out.println(oblabel);                     system.out.println(vrank);                 }             }         }

i have run several queries using same code 1 fails return results.

dbpedia requires ?default-graph-uri=http%3a%2f%2fdbpedia.org in servce url or alternatively qexec.adddefaultgraph("http://dbpedia.org"); sometimes. seems case here when using from in query.


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