code: @SuppressWarnings("unchecked")
      public static Set<String> deserializeSet(String set) {
          if (set == null || set.equals("")) {
              return new HashSet<String>();
          }
          XStream xstream = new XStream(new DomDriver());
          return (Set<String>) xstream.fromXML(set);
      }
docs: DeSerializes XML into a Set of Strings. If the XML is either
  empty or null an empty List is returned.
  
  @param set serialized as a String
  @return deserialized Set