我正在使用SUMO本体,想要用SPARQL进行查询。SUMO中一个典型的条目,比如城市,看起来像这样:
<owl:Thing rdf:ID="MadridSpain">
<rdfs:isDefinedBy rdf:resource="http://www.ontologyportal.org/SUMO.owl"/>
<rdf:type rdf:resource="#City"/>
<owl:comment xml:lang="en">The City of Madrid in Spain.</owl:comment>
<geographicSubregion rdf:resource="#Spain" />
<externalImage rdf:datatype="xsd:anyURI">[...]</externalImage>
<rdfs:label xml:lang="en">madrid spain</rdfs:label>
</owl:Thing>
如果我想从本体中获取所有城市,我可以使用以下示例查询(这个查询运行良好):
String prefix = "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> "
+ "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>";
String rdq = prefix + "SELECT ?N ?O WHERE {?N rdf:type <http://www.ontologyportal.or/SUMO.owl#City>}";
当我想筛选结果时,问题就开始了。假设我只想要所有位于西班牙地理子区域的城市。首先,我尝试通过Java和Jena分析所有结果来解决这个问题,但这需要大量时间(每个结果需要5-10秒,总共约10000个结果)。
Query myQuery = QueryFactory.create(rdq);
QueryExecution qexec = QueryExecutionFactory.create(myQuery, owlModel);
try {
ResultSet results = qexec.execSelect();
for (; results.hasNext();) {
QuerySolution sol = results.nextSolution();
Resource res = sol.getResource("N");
StmtIterator it = res.listProperties();
while(it.hasNext()){
Statement state = it.next();
//Doing some filtering
System.out.println("predicate: " + state.getPredicate().toString());
System.out.println("subject: " + state.getSubject().toString());
System.out.println("object: " + state.getObject().toString());
}
}
}catch (Exception e) {
e.printStackTrace();
System.err.println("Query Error " + e.getMessage());
}
当然,这并不是一个特别有效的方法,必须要使用正确的查询才能更加简单易懂。但目前我正在尝试定义这样一个查询,但我尝试了以下查询,但没有一个能够正常工作。
SELECT ?N ?O WHERE { ?N rdf:type <http://www.ontologyportal.org/SUMO.owl#City> .
{ SELECT ?N WHERE { (rdf:type ?b rdf:statement) .
(rdf:Predicate ?b <http://www.ontologyportal.org/SUMO.owl#geographicSubregion>) .
(rdf:Object ?b <http://www.ontologyportal.org/SUMO.owl#Spain>) } } }
SELECT ?N ?O WHERE { (rdf:statement ?b) .
(rdf:Predicate ?b <http://www.ontologyportal.org/SUMO.owl#geographicSubregion>) .
(rdf:Object ?b <http://www.ontologyportal.org/SUMO.owl#Spain>) . }";
有没有人有创造一个查询,获取一个国家内所有城市的想法?