YES Problem: f(a()) -> g(h(a())) h(g(x)) -> g(h(f(x))) k(x,h(x),a()) -> h(x) k(f(x),y,x) -> f(x) Proof: Matrix Interpretation Processor: dim=1 interpretation: [k](x0, x1, x2) = x0 + 4x1 + 3x2 + 3, [g](x0) = 4x0, [h](x0) = 4x0, [f](x0) = x0, [a] = 0 orientation: f(a()) = 0 >= 0 = g(h(a())) h(g(x)) = 16x >= 16x = g(h(f(x))) k(x,h(x),a()) = 17x + 3 >= 4x = h(x) k(f(x),y,x) = 4x + 4y + 3 >= x = f(x) problem: f(a()) -> g(h(a())) h(g(x)) -> g(h(f(x))) Matrix Interpretation Processor: dim=3 interpretation: [1 1 1] [g](x0) = [0 0 0]x0 [0 0 0] , [1 0 0] [h](x0) = [0 0 0]x0 [0 0 0] , [1 1 1] [f](x0) = [0 0 1]x0 [0 0 1] , [0] [a] = [0] [1] orientation: [1] [0] f(a()) = [1] >= [0] = g(h(a())) [1] [0] [1 1 1] [1 1 1] h(g(x)) = [0 0 0]x >= [0 0 0]x = g(h(f(x))) [0 0 0] [0 0 0] problem: h(g(x)) -> g(h(f(x))) Matrix Interpretation Processor: dim=3 interpretation: [1 0 0] [0] [g](x0) = [0 0 0]x0 + [0] [0 0 0] [1], [1 0 1] [h](x0) = [1 0 0]x0 [0 0 1] , [1 0 0] [f](x0) = [0 0 0]x0 [0 0 0] orientation: [1 0 0] [1] [1 0 0] [0] h(g(x)) = [1 0 0]x + [0] >= [0 0 0]x + [0] = g(h(f(x))) [0 0 0] [1] [0 0 0] [1] problem: Qed