使用<file：/ test＃>前缀时，Jena中的SPARQL查询缺少结果？

2 回答

• 3

  您的自定义方案缺少权限，并且不是有效的IRI .

  您可以使用jena中存在的 IRIFactory 类型之一来测试您使用的IRI . 例如，如果我通过以下方式运行您的一个IRI：

  @Test
  public void correctUri() {
     final IRIFactory factory = IRIFactory.iriImplementation();
     final IRI iri = factory.construct("file:/test#johnsFoot");
  }
  

  我得到以下异常，表明缺少IRI的权限部分，因此它不是IRI：

  org.apache.jena.iri.impl.IRIImplException: <file:/test#johnsFoot> Code: 57/REQUIRED_COMPONENT_MISSING in AUTHORITY: A component that is required by the scheme is missing.
      at org.apache.jena.iri.impl.AbsIRIFactoryImpl.throwAnyErrors(AbsIRIFactoryImpl.java:65)
      at org.apache.jena.iri.impl.AbsIRIFactoryImpl.construct(AbsIRIFactoryImpl.java:48)
      at SO_Test.correctUri(SO_Test.java:87)
  

  更新本体以使用 file://test# 而不是 file:/test# 并运行以下查询：

  @Test
  public void getAllProperties2() {
      final Query query = QueryFactory.create(
          "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>"+
          "PREFIX owl: <http://www.w3.org/2002/07/owl#>" +
          "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>" +
          "PREFIX test: <file://test#>"+
          "select * "+
          "where { "+
          "?uri ?prop ?subj"+
          "} \n "
      );
  
      final QueryExecution exec = QueryExecutionFactory.create(query, model1);
      final ResultSetRewindable results = ResultSetFactory.copyResults(exec.execSelect());
      exec.close();
  
      ResultSetFormatter.out(System.out, results, query);
      results.reset();
  }
  

  结果是您期望的输出 . 最值得注意的是，您要查看的前缀与您的元素相关联 . 输出如下：

  ---------------------------------------------------------
  | uri             | prop         | subj                 |
  =========================================================
  | test:Hand       | rdf:type     | owl:Class            |
  | test:Foot3      | rdf:type     | owl:NamedIndividual  |
  | test:Foot3      | rdf:type     | test:Foot            |
  | test:Human      | rdf:type     | owl:Class            |
  | <file://test>   | rdf:type     | owl:Ontology         |
  | test:Hand2      | rdf:type     | owl:NamedIndividual  |
  | test:Hand2      | rdf:type     | test:Hand            |
  | test:Individuum | rdf:type     | owl:Class            |
  | test:hasName    | rdf:type     | owl:DatatypeProperty |
  | test:Foot2      | rdf:type     | owl:NamedIndividual  |
  | test:Foot2      | rdf:type     | test:Foot            |
  | test:Hand1      | rdf:type     | owl:NamedIndividual  |
  | test:Hand1      | rdf:type     | test:Hand            |
  | test:Foot1      | rdf:type     | owl:NamedIndividual  |
  | test:Foot1      | rdf:type     | test:Foot            |
  | test:hasAge     | rdf:type     | owl:DatatypeProperty |
  | test:hasFoot    | rdf:type     | owl:ObjectProperty   |
  | test:hasHand    | rdf:type     | owl:ObjectProperty   |
  | test:Peter      | rdf:type     | owl:NamedIndividual  |
  | test:Peter      | rdf:type     | test:Individuum      |
  | test:Peter      | test:hasAge  | "98"                 |
  | test:Peter      | test:hasName | "Peter"              |
  | test:Peter      | test:hasFoot | test:Foot5           |
  | test:Peter      | test:hasFoot | test:Foot6           |
  | test:Peter      | test:hasHand | test:Hand1           |
  | test:Peter      | test:hasHand | test:Hand2           |
  | test:Foot6      | rdf:type     | owl:NamedIndividual  |
  | test:Foot6      | rdf:type     | test:Foot            |
  | test:Foot5      | rdf:type     | owl:NamedIndividual  |
  | test:Foot5      | rdf:type     | test:Foot            |
  | test:Doggy      | rdf:type     | owl:NamedIndividual  |
  | test:Doggy      | rdf:type     | test:Individuum      |
  | test:Doggy      | test:hasName | "Doggy"              |
  | test:Doggy      | test:hasAge  | "7"                  |
  | test:Doggy      | test:hasFoot | test:Foot1           |
  | test:Doggy      | test:hasFoot | test:Foot2           |
  | test:Doggy      | test:hasFoot | test:Foot3           |
  | test:Doggy      | test:hasFoot | test:Foot4           |
  | test:Foot4      | rdf:type     | owl:NamedIndividual  |
  | test:Foot4      | rdf:type     | test:Foot            |
  | test:Foot       | rdf:type     | owl:Class            |
  ---------------------------------------------------------
  

  使用以前的数据，以下查询会产生不同的结果：

  @Test
  public void getAllProperties() {
      final Query query = QueryFactory.create(
          "PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>"+
          "PREFIX owl: <http://www.w3.org/2002/07/owl#>" +
          "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>" +
          "PREFIX test: <file:/test#>"+
          "select * "+
          "where { "+
          "?uri ?prop ?subj"+
          "} \n "
      );
  
      final QueryExecution exec = QueryExecutionFactory.create(query, model0);
      final ResultSetRewindable results = ResultSetFactory.copyResults(exec.execSelect());
      exec.close();
  
      ResultSetFormatter.out(System.out, results, query);
      results.reset();
  }
  

  结果是：

  ----------------------------------------------------------------------------
  | uri                     | prop                 | subj                    |
  ============================================================================
  | <file:/test#Hand>       | rdf:type             | owl:Class               |
  | <file:/test#Foot1>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot1>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#hasFoot>    | rdf:type             | owl:ObjectProperty      |
  | <file:/test#Doggy>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Doggy>      | rdf:type             | <file:/test#Individuum> |
  | <file:/test#Doggy>      | <file:/test#hasName> | "Doggy"                 |
  | <file:/test#Doggy>      | <file:/test#hasAge>  | "7"                     |
  | <file:/test#Doggy>      | <file:/test#hasFoot> | <file:/test#Foot1>      |
  | <file:/test#Doggy>      | <file:/test#hasFoot> | <file:/test#Foot2>      |
  | <file:/test#Doggy>      | <file:/test#hasFoot> | <file:/test#Foot3>      |
  | <file:/test#Doggy>      | <file:/test#hasFoot> | <file:/test#Foot4>      |
  | <file:/test#Foot6>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot6>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#hasHand>    | rdf:type             | owl:ObjectProperty      |
  | <file:/test#hasName>    | rdf:type             | owl:DatatypeProperty    |
  | <file:/test>            | rdf:type             | owl:Ontology            |
  | <file:/test#Foot5>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot5>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#Human>      | rdf:type             | owl:Class               |
  | <file:/test#Hand2>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Hand2>      | rdf:type             | <file:/test#Hand>       |
  | <file:/test#Foot4>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot4>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#hasAge>     | rdf:type             | owl:DatatypeProperty    |
  | <file:/test#Hand1>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Hand1>      | rdf:type             | <file:/test#Hand>       |
  | <file:/test#Foot3>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot3>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#Peter>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Peter>      | rdf:type             | <file:/test#Individuum> |
  | <file:/test#Peter>      | <file:/test#hasAge>  | "98"                    |
  | <file:/test#Peter>      | <file:/test#hasName> | "Peter"                 |
  | <file:/test#Peter>      | <file:/test#hasFoot> | <file:/test#Foot5>      |
  | <file:/test#Peter>      | <file:/test#hasFoot> | <file:/test#Foot6>      |
  | <file:/test#Peter>      | <file:/test#hasHand> | <file:/test#Hand1>      |
  | <file:/test#Peter>      | <file:/test#hasHand> | <file:/test#Hand2>      |
  | <file:/test#Foot2>      | rdf:type             | owl:NamedIndividual     |
  | <file:/test#Foot2>      | rdf:type             | <file:/test#Foot>       |
  | <file:/test#Foot>       | rdf:type             | owl:Class               |
  | <file:/test#Individuum> | rdf:type             | owl:Class               |
  ----------------------------------------------------------------------------
  

  似乎jena没有做出最好的猜测努力来强制执行无效IRI的qname / prefix标准 .

  回复于 2024-05-05T15:39:30+08:00
• 1

  发生这种情况的原因并不明显，但是关于您对命名空间的选择不当： file:/test# .

  file: URI非常难以理解，通常执行得很差 . 特别是它们应该为本地文件启动 file://hostname/ 或（更常见地） file:/// .

  Jena的查询引擎试图纠正这个问题，但显然数据尚未得到纠正 . 我们可以使用arq命令行工具看到这个：

  $ arq --data data.rdf --query query.rq --explain
  ...
  15:12:43 INFO  exec                 :: ALGEBRA
    (project (?uri)
      (bgp (triple ?uri <file:///test#hasFoot> ?foot)))
  

  （注意 <file:///test#hasFoot> ）

  更改数据和查询中的命名空间可以解决问题 .

  我建议避免使用 file: URI . 如果您只是尝试尝试 http://example.com/ns# 或类似的 .

  回复于 2024-05-05T15:39:30+08:00