/**
* remove restriction
*/
public void removeNecessaryRestriction(IRestriction res) {
if(cls instanceof OWLNamedClass){
RDFSClass r = getResource(res);
// if this restriction is attached to more then one class
// then try just to remove its parent status
// else simply remove it
if(r.getSubclassCount() > 1){
RDFSClass clone = r.createClone();
// re-add clone to subclasses
for(Object c : r.getSubclasses(false)){
if(c instanceof OWLNamedClass && !c.equals(cls)){
((OWLNamedClass)c).addSuperclass(clone);
}