def add_op(self, id_, label=None, subPropertyOf=None, inverse=None, transitive=False, addPrefix=True):
        """ Add id_ as an owl:ObjectProperty"""
        self.add_trip(id_, rdf.type, owl.ObjectProperty)
        if inverse:
            self.add_trip(id_, owl.inverseOf, inverse)
        if subPropertyOf:
            self.add_trip(id_, rdfs.subPropertyOf, subPropertyOf)
        if label:
            self.add_trip(id_, rdfs.label, label)
            if addPrefix:
                prefix = ''.join([s.capitalize() for s in label.split()])
                namespace = self.expand(id_)
                self.add_namespace(prefix, namespace)
        if transitive:
            self.add_trip(id_, rdf.type, owl.TransitiveProperty)