public void visit(OWLDisjointObjectPropertiesAxiom axiom) {
   for (OWLObjectPropertyExpression propA : axiom.getProperties()) {
     for (OWLObjectPropertyExpression propB : axiom.getProperties()) {
       if (!propA.equals(propB)) {
         addChildParent(propA, propB, axiom);
       }
     }
   }
 }