DBpedia查询返回结果与Virtuoso但不与Jena

Question

我尝试使用Jena创建SPARQL查询来查询DBpedia。当我使用Virtuoso时查询正在运行，但当我将其插入以下Java代码时，它返回一个空集。

String sr="Christopher_Nolan";
String sparqlQueryString1 = "PREFIX dbont: <http://dbpedia.org/ontology/> "+            
        "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>"+ 
        "PREFIX foaf: <http://xmlns.com/foaf/0.1/> "+
        "   SELECT distinct   ?s"+        
        "   WHERE {  "+       
        "?s foaf:name ?label  ."  +
        "filter(?label=\"Christpher_Nolan\"@en)." +             
        "        }";
          Query query = QueryFactory.create(sparqlQueryString1);
          QueryExecution qexec = QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql", query);

          ResultSet results = qexec.execSelect();
          ResultSetFormatter.out(System.out,results, query);       

         qexec.close() ;    

Answer 1

我认为这不是Jena的问题，而是您的特定查询。您的查询在DBpedia SPARQL端点上运行时不会产生任何结果

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s      
WHERE {
  ?s foaf:name ?label .
  filter(?label="Christpher_Nolan"@en)
}

SPARQL results (no results)

但是，如果您向名称Christopher添加o，并将下划线更改为空格，则会得到三个结果：

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s      
WHERE {
  ?s foaf:name ?label .
  filter(?label="Christopher Nolan"@en)
}

SPARQL results (3 results)

  

<强>取值
  http://dbpedia.org/resource/Christopher_Nolan_(author)
  http://dbpedia.org/resource/Christopher_Nolan
  http://dbpedia.org/resource/Chris_Nolan_(musician)

我还要指出，这是对filter的一种相当不寻常的用法。如果要选择使用特定值的三元组，只需将该值放入三元模式中：

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT distinct ?s      
WHERE {
  ?s foaf:name "Christopher Nolan"@en 
}

SPARQL results (same 3 results)