[Pellet-users] SWRL and Pellet code: Some Questions

[Paolo Bussotti]

Hi everybody,
Please, might someone tell me why this code gives a 
"java.lang.NullPointerException" when executed, at the moment that I try 
to retrieve the
two SpecialCourse which should be deduced by the firing of the rule (I 
refer to "http://www.mindswap.org/~kolovski/rules.owl") ?
I have tried to reproduce the functionality of the code reported on this 
list, see"Code examples using SWRL and Pellet",  using as much Jena as 
possible as it is Pellet.java in the pellet-1.4-RC1 release.  Therefore 
I have used Jena OntModel instead of the OWL-API OWLOntology (as in the 
mention example) . I also have tried to programmatically querying the 
model calling the OWLReasoner method  "getInstances" (instead of the 
Reasoner method "AllInstanceOf") to retrieve the instances which should 
be deduced, but it fails. Another thing: Do the rules start  to work 
after the setRule instruction or after a query ?
Thanks in advance.
Paolo Bussotti             

     public class swrl_14rc1
      {OntModel model;
        OWLReasoner reasoner;
        public static void main(String args[])
        {// ontology and rules files
        //String ontFile = "http://www.mindswap.org/~kolovski/rules.owl";
        String ontFile="file:rules.owl";
        String rulesFile = ontFile;
        
         // load the ontology
         
         InputStream inStream = FileManager.get().open(ontFile);
         model = ModelFactory.createOntologyModel( 
PelletReasonerFactory.THE_SPEC);
         model.read(inStream,"");
         reasoner = ((PelletInfGraph) model.getGraph()).getOWLReasoner();
         ((PelletInfGraph) model.getGraph()).setLazyConsistency( true );
         model.prepare();

         // load the rules
        
         try{Set rules = RuleUtils.parseRules(rulesFile);
             reasoner.getKB().setRules(rules);
             RuleUtils.pruneSWRLIntroducedInds( reasoner.getKB() );
            }
         catch(Exception e1_1){System.out.println(e1_1.toString());}

          // query
         String ns = 
"http://www.mindswap.org/~edna/swoopRules/examples/lubm_owllog.owl#";
         Set specialCourses=null;
         OntClass specialCourse=null;
         specialCourse = model.getOntClass(ns + "SpecialCourse");    
         try{specialCourses = reasoner.getInstances(specialCourse);
            }
         catch(Exception 
e2_2){System.out.println("e2_2:"+e2_2.toString());}                       
         System.out.println(specialCourses);
       }
    };