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[ontolog-forum] ontology programming (jena+java)

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From: fatemeh hosseini <fa.hosseinim@xxxxxxxxx>
Date: Sun, 26 Sep 2010 09:28:01 +0430
Message-id: <AANLkTi=yextdPM6V9u-rvA_9fO0ScaOkuQ78O73e04K3@xxxxxxxxxxxxxx>
dear all

i use jena and java for ontology programming.I'm new to Java, and jena. I use Eclipse IDE.
I have some problem (please help me)?‎

1-- how can i calculate distance between two classes in an ontology(number of links between two classes)??

2-- how can i get mincardinality of a property for a given Class?
i tried to do it.
i add these :
import com.hp.hpl.jena.ontology.MinCardinalityQRestriction;
import  com.hp.hpl.jena.ontology.*;
import com.hp.hpl.jena.ontology.Restriction;

i  write this code  but it doesn't work correctly.(it gives all properties !!)

  for (Iterator i = c.listDeclaredProperties(true); i.hasNext(); )
                     {         //begin 

                  OntProperty op = (OntProperty) i.next();
                  System.out.println("op: " + op+" **class** "+c.getLocalName());

              // restriction with a given URI
                       Restriction r = m.getRestriction( c.getURI() );

               // anonymous restriction on property op
                       Restriction anonr = m.createRestriction( op );

              //to convert the anonymous restriction

               MinCardinalityRestriction avf =

   System.out.println("cardin***  " +avf.getOnProperty().getLocalName());

                  }    //end 

output is this(+error):

op: http://www.atl.lmco.com/projects/ontology/ontologies/animals/animalsA.owl#hasFemaleParent
**class** Animal
cardin+**+  hasFemaleParent
op: http://www.atl.lmco.com/projects/ontology/ontologies/animals/animalsA.owl#hasFather
**class** Animal
cardin+**+  hasFather

Exception in thread "main" java.lang.NullPointerException
       at pak2.ontology1.main(ontology1.java:445)

3- how can i get level of a resource in an ontology?

thanks advance.
fatemeh hosseini 

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