YES(?,O(n^2)) TRS: { f(x, y) -> g(x, y), g(h x, y) -> h f(x, y), g(h x, y) -> h g(x, y)} DUP: We consider a non-duplicating system. Trs: { f(x, y) -> g(x, y), g(h x, y) -> h f(x, y), g(h x, y) -> h g(x, y)} Matrix Interpretation: Interpretation class: triangular [X1] [1 0][X1] [0] [h]([X0]) = [0 1][X0] + [1] [X3] [X1] [1 2][X3] [1 0][X1] [0] [g]([X2], [X0]) = [0 1][X2] + [0 0][X0] + [0] [X3] [X1] [1 2][X3] [1 0][X1] [1] [f]([X2], [X0]) = [0 1][X2] + [0 0][X0] + [0] Qed