private Node<OWLObjectPropertyExpression> toObjectPropertyNode(Set<ATermAppl> terms) {
   return NodeFactory.getOWLObjectPropertyNode(OP_MAPPER.map(terms));
 }
 private Node<OWLDataProperty> toDataPropertyNode(Set<ATermAppl> terms) {
   return NodeFactory.getOWLDataPropertyNode(DP_MAPPER.map(terms));
 }
 private Node<OWLNamedIndividual> toIndividualNode(Set<ATermAppl> terms) {
   return NodeFactory.getOWLNamedIndividualNode(IND_MAPPER.map(terms));
 }
 private Node<OWLClass> toClassNode(Set<ATermAppl> terms) {
   return NodeFactory.getOWLClassNode(CLASS_MAPPER.map(terms));
 }