/**
  * Creates a DavPropertyName from the given parameters and add it to this set.
  *
  * @param localName
  * @param namespace
  * @return <tt>true</tt> if the set did not already contain the specified property name.
  */
 public boolean add(String localName, Namespace namespace) {
   return set.add(DavPropertyName.create(localName, namespace));
 }