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