I am not able to update ontology model

Question

I have made an Ontologu in Protege and imported in Eclipse.My ontology already 10 instances and i want to add more instances.The following piece of code adds instances to existing class (Noun) of ontology. After excecution it do not update ontology model and shows same number of instances.

  public static void main(String[] args) throws OWLException, IOException{
  OWLOntologyManager manager = OWLManager.createOWLOntologyManager();

  File file = new File("D:\\word.owl");{  
      OntModel model=ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF);
       System.out.println("Model is called successfully");
    OWLOntology ont = manager.loadOntologyFromOntologyDocument(file);
    System.out.println("Loaded ontology: " + ont);

   String SOURCE = ("D:\\word.owl");
   String NS = SOURCE;
   OntModel base = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF);
   base.read( SOURCE, "" );

OntModel inf =ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF, base );

 OntClass Noun = base.getOntClass( NS + "Noun" );
 Individual jack = base.createIndividual( NS + "Jack", Noun );
 Individual Helley = base.createIndividual( NS + "Helley", Noun );  
  manager.saveOntology(ont);

 System.out.println("Number of individuals: " + ont.getIndividualsInSignature().size());

    }
  }
 }

Output

  Model is called successfully
  Loaded ontology: 
 Number of individuals: 10

Answer 1

This works:

import java.io.FileWriter;
import java.io.InputStream;

import org.apache.jena.ontology.Individual;
import org.apache.jena.ontology.OntClass;
import org.apache.jena.ontology.OntModel;
import org.apache.jena.ontology.OntModelSpec;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.util.FileManager;
import org.apache.jena.vocabulary.RDF;

public class Mgt {

    public static void main(String[] args) throws Exception {
        String namespace = "http://www.semanticweb.org/Word#";
        String file = "word.owl";
        OntModel jenaModel = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF);

        InputStream in = FileManager.get().open(file);
        jenaModel.read(in, null);
        OntClass Noun = jenaModel.getOntClass(namespace + "Noun");
        Individual Organization = Noun.createIndividual(namespace + "Organization");
        jenaModel.add(Organization, RDF.type, Noun);
        FileWriter out = new FileWriter("word.out.owl");
        jenaModel.getWriter("RDF/XML-ABBREV").write(jenaModel, out, namespace);
        out.close();
    }
}

Note that namespace is not related to the file name.

Answer 2

I dont use that API but I can see your issue.

At the start of your code you create an OWLOntology object:

OWLOntology ont = manager.loadOntologyFromOntologyDocument(file);

And here is the issue, you do not alter ont anywhere in your code, so when you call the line below, it will only show/save the same 10 individuals that you loaded from file at the beginning of your code:

manager.saveOntology(ont);

System.out.println("Number of individuals: " + ont.getIndividualsInSignature().size());

So to fix this you need to somehow modify ont to include the new Individual before using the above lines.

Answer 3

Updated Code It gives Exception in thread "main" java.lang.NullPointerException at Mgt.main(Mgt.java:29)

import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import org.apache.jena.ontology.Individual;
import org.apache.jena.ontology.OntClass;
import org.apache.jena.ontology.OntModel;
import org.apache.jena.ontology.OntModelSpec;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.util.FileManager;
public class Mgt {
static OntModel jenaModel = null;
public static void main(String[] args) throws Exception{
    String file =("D:\\word.owl");
     jenaModel = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF);

            InputStream in = FileManager.get().open(file);
            try 
            {
                jenaModel.read(in, null);
            } 
            catch (Exception e) 
            {
                e.printStackTrace();
            }
            System.out.println("Ontology " + file + " loaded.");
            OntClass Noun = jenaModel.getOntClass( "http://www.semanticweb.org/Word#Noun" );
            Individual Organization = Noun.createIndividual(file + "Organization");
            FileWriter out = null;
            try {
              // XML format - long and verbose
              out = new FileWriter( file);
              jenaModel.write( out, "RDF/XML" );

            }
            finally {
              if (out != null) {
                try {out.close();
                } catch (IOException ignore) {}
              }
            }
          }
         }