YES O(n^4) TRS: { a(c(d(x))) -> c(x), u(b(d(d(x)))) -> b(x), v(c(x)) -> b(x), v(a(c(x))) -> u(b(d(x))), v(a(a(x))) -> u(v(x)), w(c(x)) -> b(x), w(a(c(x))) -> u(b(d(x))), w(a(a(x))) -> u(w(x)) } DUP: We consider a non-duplicating system. Trs: { a(c(d(x))) -> c(x), u(b(d(d(x)))) -> b(x), v(c(x)) -> b(x), v(a(c(x))) -> u(b(d(x))), v(a(a(x))) -> u(v(x)), w(c(x)) -> b(x), w(a(c(x))) -> u(b(d(x))), w(a(a(x))) -> u(w(x)) } Matrix Interpretation: Interpretation class: triangular [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [w]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [v]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [u]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [b]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 1 0 0][X3] [0] [X2] [0 1 0 0][X2] [1] [d]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 1 0 0][X3] [0] [X2] [0 1 0 0][X2] [1] [a]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 0 0 0][X3] [1] [X2] [0 1 0 0][X2] [0] [c]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] Qed