Hi.
Assume the attached RDF file. This is a simple
Manufacturer -> Europe (subclass) -> Germany (subclass) -> Audi (subclass)
-> Instance,
which has been created using inference for subclass and type from jena.
The problem that I have is that if I get the root class (in this example
Manufacturer)
and call the listInstances(true) method, I get an empty set (I assume that
I should
get Manufacturer, since it has a direct instance).
Furthermore, if I use the transitive reduction of the above code and use no
inference
in the model, the listInstances(false) method this time, again I get an
empty result
(I assume that again I should get the Manufacturer class).
Finally, I am really interested in very fast access from classes or
subclasses to instances and from instances to classes and
subclasses. Can you provide me any hints?
Thank you!
public class JenaTest {
private OntModel model;
private String inputFileName;
public JenaTest() {
// Create a simple RDFS++ Reasoner.
//StringBuilder sb = new StringBuilder();
//sb.append("[rdfs9: (?x rdfs:subClassOf ?y), (?a rdf:type ?x) ->
(?a rdf:type ?y)] ");
//sb.append("[rdfs11: (?x rdfs:subClassOf ?y), (?y rdfs:subClassOf
?z) -> (?x rdfs:subClassOf ?z)] ");
//Reasoner reasoner = new
GenericRuleReasoner(Rule.parseRules(sb.toString()));
// an OWL/RDF model that performs no reasoning at all:
model = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM);
//Model base = ModelFactory.createDefaultModel();
//model = ModelFactory.createOntologyModel(OntModelSpec.RDFS_MEM,
ModelFactory.createInfModel(reasoner, base));
// using the FileManager to find the input file:
InputStream in =
FileManager.get().open("/home/mythos/Virtuoso/WISE_Demo_Data/data/TestInference.rdf");
if (in == null) {
System.out.println("File: \"" + inputFileName + "\" not found");
}
// read the RDF/XML file
try {
model.read(in, "");
} catch (Exception e) {
System.err.println("Could not read file \"" + inputFileName +
"\". It's either malformed or corrupted\n");
}
}
public Set<String> getAllTopClassesWithInstances() {
Set <String> top = new HashSet<String>();
ExtendedIterator<OntClass> it = model.listHierarchyRootClasses();
for (; it.hasNext();) {
OntClass cl = it.next();
if (cl.listInstances(false).hasNext()) {
String c = cl.getLocalName();
top.add(c);
}
}
return top;
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
JenaTest test = new JenaTest();
Set <String> top = test.getAllTopClassesWithInstances();
System.out.println(top);
}
}
--
Panagiotis Papadakos,
PhD Student
Computer Science Department
University of Crete
http://www.csd.uoc.gr/~papadako
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#";
xmlns:owl="http://www.w3.org/2002/07/owl#";
xmlns="http://www.semanticweb.org/ontologies/2012/Preferences#";
xmlns:ontologies="http://www.semanticweb.org/ontologies/2012/";
xmlns:xsd="http://www.w3.org/2001/XMLSchema#";
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"; >
<rdf:Description rdf:about="http://www.semanticweb.org/ontologies/2012/Preferences#Europe";>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Manufacturer"/>
<rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
</rdf:Description>
<rdf:Description rdf:about="http://www.semanticweb.org/ontologies/2012/Preferences#ID21_Car_Audi_A3_2012_Automatic_Front_1.984lt_200hp_0Cyl_0.0022THC_0.71CO_428CO2_0.011NOx_0PM_0CH4_0N20";>
<rdf:type rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Manufacturer"/>
<rdf:type rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Europe"/>
<rdf:type rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Germany"/>
<rdf:type rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Audi"/>
</rdf:Description>
<rdf:Description rdf:about="http://www.semanticweb.org/ontologies/2012/Preferences#Manufacturer";>
<rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
</rdf:Description>
<rdf:Description rdf:about="http://www.semanticweb.org/ontologies/2012/Preferences#Germany";>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Manufacturer"/>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Europe"/>
<rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
</rdf:Description>
<rdf:Description rdf:about="http://www.semanticweb.org/ontologies/2012/Preferences#Audi";>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Manufacturer"/>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Europe"/>
<rdfs:subClassOf rdf:resource="http://www.semanticweb.org/ontologies/2012/Preferences#Germany"/>
<rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
</rdf:Description>
</rdf:RDF>
