Can I add annotations to object property assertion from jena?

Question

I want to add an annotation (comment) to an object property assertion like the one below.

Mobile → hasCamera → 8MP

I am able to get this specific assertion as a Statement object. Now I want to add annotations to this statement object, but there aren't any direct methods to do this with Jena. On the other hand I am able to easily achieve this in Protege tool. So is this just a feature of Protégé, or is there any possible way to do this with Jena?

Basically, I'm interested in this, to add a weight score to the property (link) between the two resources viz. Mobile and 8MP.

Answer 1

Jena, though it has some support for OWL via OntModels, is really an RDF-based API. Statements in Jena are just a class representing the triple, and don't themselves represent a resource. If you want to create annotated object property assertions, you'll need to have a look at Section 2.3 Translation of Axioms with Annotations from the OWL 2 Web Ontology Language Mapping to RDF Graphs. Specifically, it looks like 2.3.1 Axioms that Generate a Main Triple is what you'll want:

If the row of Table 1 corresponding to the type of ax' contains a single main triple s p xlt ., then the axiom ax is translated into the following triples:

s p xlt .
_:x rdf:type owl:Axiom .
_:x owl:annotatedSource s .
_:x owl:annotatedProperty p .
_:x owl:annotatedTarget xlt .
TANN(annotation1, _:x)
...
TANN(annotationm, _:x)

This is the case if ax' is of type … ObjectPropertyAssertion ….

The referenced Table 1 appears earlier in section 2.1 Translation of Axioms without Annotations.

So, to add the triple

Mobile hasCamera 8MP

with the annotation

hasWeightScore 6.7

you can use the following code:

import com.hp.hpl.jena.ontology.AnnotationProperty;
import com.hp.hpl.jena.ontology.Individual;
import com.hp.hpl.jena.ontology.ObjectProperty;
import com.hp.hpl.jena.ontology.OntModel;
import com.hp.hpl.jena.ontology.OntModelSpec;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.vocabulary.OWL;
import com.hp.hpl.jena.vocabulary.OWL2;

public class AnnotatedAxioms {
    public static void main(String[] args) {
        final String ns = "http://example.org/";
        final OntModel model = ModelFactory.createOntologyModel( OntModelSpec.OWL_DL_MEM );
        model.setNsPrefix( "ex", ns );

        final Individual mobile = model.createIndividual( ns+"Mobile", OWL.Thing );
        final ObjectProperty hasCamera  = model.createObjectProperty( ns+"hasCamera" );
        final Individual eightMP = model.createIndividual( ns+"8MP", OWL.Thing );

        final AnnotationProperty hasWeightScore = model.createAnnotationProperty( ns+"hasWeightScore" );

        final Resource axiom = model.createResource( OWL2.Axiom );
        axiom.addProperty( OWL2.annotatedSource, mobile );
        axiom.addProperty( OWL2.annotatedProperty, hasCamera );
        axiom.addProperty( OWL2.annotatedTarget, eightMP );
        axiom.addLiteral( hasWeightScore, 6.7 );

        model.write( System.out, "RDF/XML-ABBREV" );
    }
}

which produces the following ontology:

<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:owl="http://www.w3.org/2002/07/owl#"
    xmlns:ex="http://example.org/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
  <owl:ObjectProperty rdf:about="http://example.org/hasCamera"/>
  <owl:AnnotationProperty rdf:about="http://example.org/hasWeightScore"/>
  <owl:Axiom>
    <ex:hasWeightScore rdf:datatype="http://www.w3.org/2001/XMLSchema#double"
    >6.7</ex:hasWeightScore>
    <owl:annotatedTarget>
      <owl:Thing rdf:about="http://example.org/8MP"/>
    </owl:annotatedTarget>
    <owl:annotatedProperty rdf:resource="http://example.org/hasCamera"/>
    <owl:annotatedSource>
      <owl:Thing rdf:about="http://example.org/Mobile"/>
    </owl:annotatedSource>
  </owl:Axiom>
</rdf:RDF>