YES O(n^4) TRS: { f(x, x, y) -> x, f(x, y, y) -> y, f(x, y, g(y)) -> x, f(f(x, y, z), u, f(x, y, v)) -> f(x, y, f(z, u, v)), f(g(x), x, y) -> y } DUP: We consider a non-duplicating system. Trs: { f(x, x, y) -> x, f(x, y, y) -> y, f(x, y, g(y)) -> x, f(f(x, y, z), u, f(x, y, v)) -> f(x, y, f(z, u, v)), f(g(x), x, y) -> y } Matrix Interpretation: Interpretation class: triangular [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [g]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X11] [X7] [X3] [1 0 0 0][X11] [1 0 0 0][X7] [1 0 0 0][X3] [1] [X10] [X6] [X2] [0 1 0 0][X10] [0 0 0 0][X6] [0 1 0 0][X2] [0] [f]([ X9], [X5], [X1]) = [0 0 1 0][X9] + [0 0 0 0][X5] + [0 0 1 0][X1] + [0] [ X8] [X4] [X0] [0 0 0 1][X8] [0 0 0 0][X4] [0 0 0 1][X0] [0] Qed