YES O(n^3) TRS: {f(g(f(a()), h(a(), f(a())))) -> f(h(g(f(a()), a()), g(f(a()), f(a()))))} DUP: We consider a non-duplicating system. Trs: {f(g(f(a()), h(a(), f(a())))) -> f(h(g(f(a()), a()), g(f(a()), f(a()))))} Matrix Interpretation: Interpretation class: triangular [0] [a] = [0] [0] [X5] [X2] [1 0 0][X5] [1 0 0][X2] [0] [g]([X4], [X1]) = [0 0 0][X4] + [0 0 0][X1] + [0] [X3] [X0] [0 0 1][X3] [0 0 0][X0] [0] [X5] [X2] [1 0 0][X5] [1 0 0][X2] [0] [h]([X4], [X1]) = [0 0 0][X4] + [0 0 0][X1] + [0] [X3] [X0] [0 0 0][X3] [0 0 0][X0] [0] [X2] [1 0 1][X2] [0] [f]([X1]) = [0 0 0][X1] + [0] [X0] [0 0 0][X0] [1] Qed