YES O(n^4) TRS: { f(g(i(a(), b(), b'()), c()), d()) -> if(e(), f(.(b(), c()), d'()), f(.(b'(), c()), d'())), f(g(h(a(), b()), c()), d()) -> if(e(), f(.(b(), g(h(a(), b()), c())), d()), f(c(), d'())) } DUP: We consider a non-duplicating system. Trs: { f(g(i(a(), b(), b'()), c()), d()) -> if(e(), f(.(b(), c()), d'()), f(.(b'(), c()), d'())), f(g(h(a(), b()), c()), d()) -> if(e(), f(.(b(), g(h(a(), b()), c())), d()), f(c(), d'())) } 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 0 0][X5] + [0 0 0 0][X1] + [0] [X4] [X0] [0 0 0 0][X4] [0 0 0 0][X0] [0] [0] [0] [d] = [0] [0] [0] [0] [a] = [0] [0] [X11] [X7] [X3] [1 0 0 0][X11] [1 0 0 0][X7] [1 0 0 0][X3] [0] [X10] [X6] [X2] [0 0 0 0][X10] [0 0 0 0][X6] [0 0 0 0][X2] [0] [i]([ X9], [X5], [X1]) = [0 0 0 0][X9] + [0 0 0 0][X5] + [0 0 0 0][X1] + [0] [ X8] [X4] [X0] [0 0 0 0][X8] [0 0 0 1][X4] [0 0 0 1][X0] [1] [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] [g]([X5], [X1]) = [0 0 0 0][X5] + [0 0 1 0][X1] + [1] [X4] [X0] [0 0 0 1][X4] [0 0 0 0][X0] [1] [0] [0] [b'] = [0] [1] [0] [0] [d'] = [0] [0] [0] [0] [c] = [1] [0] [0] [0] [b] = [0] [1] [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] [.]([X5], [X1]) = [0 0 0 0][X5] + [0 0 0 0][X1] + [0] [X4] [X0] [0 0 0 0][X4] [0 0 0 0][X0] [0] [X7] [X3] [1 0 0 1][X7] [1 0 0 0][X3] [0] [X6] [X2] [0 0 1 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 0][X0] [0] [0] [0] [e] = [0] [0] [X11] [X7] [X3] [1 0 0 0][X11] [1 0 0 0][X7] [1 0 0 0][X3] [0] [X10] [X6] [X2] [0 0 0 0][X10] [0 0 0 0][X6] [0 0 0 0][X2] [0] [if]([ X9], [X5], [X1]) = [0 0 0 0][X9] + [0 0 0 0][X5] + [0 0 0 0][X1] + [0] [ X8] [X4] [X0] [0 0 0 0][X8] [0 0 0 0][X4] [0 0 0 0][X0] [0] Qed