MAYBE
MAYBE
TRS:
 {
    mark(f(X1, X2)) -> active(f(mark(X1), X2)),
          mark(a()) -> active(a()),
          mark(b()) -> active(b()),
    f(X1, mark(X2)) -> f(X1, X2),
  f(X1, active(X2)) -> f(X1, X2),
    f(mark(X1), X2) -> f(X1, X2),
  f(active(X1), X2) -> f(X1, X2),
    active(f(X, X)) -> mark(f(a(), b())),
        active(b()) -> mark(a())
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
      mark(f(X1, X2)) -> active(f(mark(X1), X2)),
            mark(a()) -> active(a()),
            mark(b()) -> active(b()),
      f(X1, mark(X2)) -> f(X1, X2),
    f(X1, active(X2)) -> f(X1, X2),
      f(mark(X1), X2) -> f(X1, X2),
    f(active(X1), X2) -> f(X1, X2),
      active(f(X, X)) -> mark(f(a(), b())),
          active(b()) -> mark(a())
   }
  Fail