YES O(n^4) TRS: { mark(h(X)) -> active(h(X)), mark(g(X)) -> active(g(X)), mark(d()) -> active(d()), mark(c()) -> active(c()), h(mark(X)) -> h(X), h(active(X)) -> h(X), active(h(d())) -> mark(g(c())), active(g(X)) -> mark(h(X)), active(c()) -> mark(d()), g(mark(X)) -> g(X), g(active(X)) -> g(X) } DUP: We consider a non-duplicating system. Trs: { mark(h(X)) -> active(h(X)), mark(g(X)) -> active(g(X)), mark(d()) -> active(d()), mark(c()) -> active(c()), h(mark(X)) -> h(X), h(active(X)) -> h(X), active(h(d())) -> mark(g(c())), active(g(X)) -> mark(h(X)), active(c()) -> mark(d()), g(mark(X)) -> g(X), g(active(X)) -> g(X) } Matrix Interpretation: Interpretation class: triangular [2] [0] [c] = [1] [1] [0] [3] [d] = [1] [0] [X3] [1 3 0 0][X3] [2] [X2] [0 1 0 0][X2] [0] [g]([X1]) = [0 0 0 1][X1] + [1] [X0] [0 0 0 0][X0] [0] [X3] [1 0 0 0][X3] [0] [X2] [0 1 0 3][X2] [2] [active]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [0] [X3] [1 3 0 0][X3] [0] [X2] [0 1 0 0][X2] [0] [h]([X1]) = [0 0 0 0][X1] + [1] [X0] [0 0 0 0][X0] [0] [X3] [1 0 1 0][X3] [0] [X2] [0 1 1 3][X2] [1] [mark]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [0] Qed