SPARQL DELETE: not possible in jena/pellet?

Question

I am working on ontology reconciliation between two ontologies. I apply the jena/pellet platform, locally, and apply sparql rules as much as possible. For inserts this is successful, for deletes it is not, no matter what I try. This raises the question whether sparql deletes are supported at all with jena/pellet. Please advise!

Please find the related code snippets below. First the code, then the sparql DELETE query.

public void executeDelete(String mySparqlFile, OntModel o ) {
  UpdateRequest updateObj = null;
  UpdateProcessor up = null;
  GraphStore graphStore = GraphStoreFactory.create();

  graphStore.setDefaultGraph( o.getGraph() );

  updateObj = UpdateFactory.read( mySparqlFile );
  up = UpdateExecutionFactory.create(updateObj, graphStore);
  up.execute();
}


public static void main() {
  static OntModel ontModel = ModelFactory.createOntologyModel(PelletReasonerFactory.THE_SPEC, rawModel);
  static OntModel stanfordModel = ModelFactory.createOntologyModel(PelletReasonerFactory.THE_SPEC);

  stanfordModel.read("path/to/modelA.owl");
  ontModel.addSubModel(stanfordModel);

  executeDelete("path/to/delQuery.sparql", ontModel);
}

the file "delQuery.sparql"

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX stfd: <http://www.semanticweb.org/brandtp/ontologies/2014/6/Goose-stanford-metamodel.owl#>

DELETE { ?c a stfd:Token . }
WHERE { 
    ?c stfd:hasFeature stfd:Determiner . 
}