public Relation do3NFSynthesis(Relation rel) {
                  Relation temp;
                  if (rel != null) {
                          temp = rel.minimalCover();
                          if (temp != null) {
                                  temp = temp .standardForm();
                                  if (temp != null) {
                                          return temp.addKeyRelations();
                                  }       
                          }
                  }
                  return null;
          }