MAYBE MAYBE TRS: { f(x, f(y, z)) -> f(f(x, y), z), f(f(a(), b()), x) -> f(b(), f(a(), f(c(), f(b(), f(a(), x))))) } DUP: We consider a non-duplicating system. Trs: { f(x, f(y, z)) -> f(f(x, y), z), f(f(a(), b()), x) -> f(b(), f(a(), f(c(), f(b(), f(a(), x))))) } Fail