0

I'm using Jena to query my ontology, and I'm following Step 8: Querying a Model of this tutorial. The RDF file vc-db-1.rdf being queried here is generated from Step 3: Writing RDF and is shown below:

<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#" > 
  <rdf:Description rdf:nodeID="A0">
    <vcard:Family>Smith</vcard:Family>
    <vcard:Given>John</vcard:Given>
  </rdf:Description>
  <rdf:Description rdf:about="http://somewhere/JohnSmith">
    <vcard:N rdf:nodeID="A0"/>
    <vcard:FN>John Smith</vcard:FN>
  </rdf:Description>
</rdf:RDF>

The sample code is tutorial 7 and can be downloaded here.

I noticed that in the line

ResIterator iter = model.listResourcesWithProperty(VCARD.FN);

VCARD.FN is only a property name from the RDF, but not a defined variable in my code. However, it can be successfully recognized here and the code runs without any problem.

But this is not the case with my own RDF file. I created an ontology pottery.owl with Protege and saved it in RDF/XML language. The file content is as followed:

<?xml version="1.0"?>
<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:protege="http://protege.stanford.edu/plugins/owl/protege#"
    xmlns:xsp="http://www.owl-ontologies.com/2005/08/07/xsp.owl#"
    xmlns:owl="http://www.w3.org/2002/07/owl#"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
    xmlns:swrl="http://www.w3.org/2003/11/swrl#"
    xmlns="http://www.owl-ontologies.com/Ontology1369190090.owl#"
    xmlns:swrlb="http://www.w3.org/2003/11/swrlb#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xml:base="http://www.owl-ontologies.com/Ontology1369190090.owl" > 
  <rdf:Description rdf:about="">
    <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#Ontology"/>
  </rdf:Description>
  <rdf:Description rdf:about="#pottery">
    <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#Class"/>
  </rdf:Description>
  <rdf:Description rdf:about="#pottery_instance_1">
    <rdf:type rdf:resource="#pottery"/>
    <pottery.colors rdf:datatype="http://www.w3.org/2001/XMLSchema#string">blue</pottery.colors>
  </rdf:Description>
  <rdf:Description rdf:about="#pottery.colors">
    <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#DatatypeProperty"/>
    <rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
    <rdfs:domain rdf:resource="#pottery"/>
  </rdf:Description>
</rdf:RDF>

<!-- Created with Protege (with OWL Plugin 3.4.8, Build 629)  http://protege.stanford.edu -->

The ontology contains a class pottery, an instance pottery_instance_1, and a datatype property pottery.colors.

And I modified these lines in the original code:

static final String inputFileName = "pottery.owl";
// ...
ResIterator iter = model.listResourcesWithProperty(pottery.colors);
// ...
System.out.println("  " + iter.nextResource()
                              .getProperty(pottery.colors)
                              .getString());

This time I got the error "pottery cannot be resolved to a variable."

What's the trick here? Does it have anything to do with the difference between the formats of the two RDFs? Or something else? Thank you.

4

1 回答 1

1

VCARD是 package 中定义的 java 类com.hp.hpl.jena.vocabulary。它包含（现在，旧的）VCard 词汇表中所有项目的 Java 常量。

如果您想从本体生成自己的类，请查看schemagenJena 附带的应用程序。

于 2013-05-22T08:08:41.847 回答