YES TRS: active(f(g(X),Y)) -> mark(f(X,f(g(X),Y))) mark(f(X1,X2)) -> active(f(mark(X1),X2)) mark(g(X)) -> active(g(mark(X))) f(mark(X1),X2) -> f(X1,X2) f(X1,mark(X2)) -> f(X1,X2) f(active(X1),X2) -> f(X1,X2) f(X1,active(X2)) -> f(X1,X2) g(mark(X)) -> g(X) g(active(X)) -> g(X) linear polynomial interpretations on N: active_A(x1) = x1 active#_A(x1) = x1 + 2 f_A(x1,x2) = x1 + 1 f#_A(x1,x2) = 0 g_A(x1) = x1 + 2 g#_A(x1) = x1 + 1 mark_A(x1) = x1 mark#_A(x1) = x1 + 3 precedence: mark > active > f > g