Ajouter une donnée à une ontologie

je suis bloqué à cette étape d'insertion des instances à une ontologie.

Code:

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public  class Ajour {
	public static void main(String[]  args) throws Exception {
    Model model = ModelFactory.createDefaultModel() ;
 
    String updateString = "PREFIX reuses: <http://www.owl-ontologies.com/reuses.owl> \n"
            + "INSERT DATA {\n"
            + "    <http://www.owl-ontologies.com/reuses.owl#Besoin>   a   reuses:Besoin;\n"
            + "}";
 
    UpdateAction.parseExecute(updateString, model) ;        
 
    String queryString = "SELECT ?s ?p ?o WHERE { ?s ?p ?o}" ;
    Query query = QueryFactory.create(queryString) ;
    QueryExecution qexec = QueryExecutionFactory.create(query, model) ;
    try {
        ResultSet results = qexec.execSelect() ;
        while(results.hasNext()) {
            QuerySolution soln = results.nextSolution() ;
            RDFNode s = soln.get("s") ;
            System.out.println(s.toString());
            RDFNode p = soln.get("p") ;
            System.out.println(p.toString());
            RDFNode o = soln.get("o") ;
            System.out.println(o.toString());
        }
    } finally { qexec.close() ; }       
 
    model.close();
}}

voici les erreurs

Citation:

Exception in thread "main" java.lang.NullPointerException
at com.hp.hpl.jena.sparql.engine.binding.BindingUtils.addToBinding(BindingUtils.java:74)
at com.hp.hpl.jena.sparql.engine.binding.BindingUtils.asBinding(BindingUtils.java:68)
at com.hp.hpl.jena.update.UpdateAction.parseExecute(UpdateAction.java:142)
at com.hp.hpl.jena.update.UpdateAction.parseExecute(UpdateAction.java:105)
at conn.Ajour.main(Ajour.java:40)

SVP aidez moi