YES Problem: strict: t(f(x),g(y),f(z())) -> t(z(),g(x),g(y)) t(g(x),g(y),f(z())) -> t(f(y),f(z()),x) weak: f(g(x)) -> g(f(x)) g(f(x)) -> f(g(x)) f(f(x)) -> g(g(x)) g(g(x)) -> f(f(x)) Proof: Matrix Interpretation Processor: dim=5 interpretation: [1 1 1 1 0] [0 0 0 1 0] [g](x0) = [0 0 0 0 1]x0 [0 0 0 0 0] [0 0 0 0 0] , [1 0 1 1 0] [1 0 1 0 0] [1 0 1 0 1] [1] [1 0 1 0 1] [1 1 1 0 0] [0 0 1 0 0] [1] [t](x0, x1, x2) = [0 1 0 0 0]x0 + [0 0 0 0 0]x1 + [0 0 0 0 0]x2 + [0] [0 1 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0] [0 1 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0], [1 0 1 0 1] [0 0 0 0 0] [f](x0) = [0 1 0 1 0]x0 [0 0 0 0 0] [0 0 0 1 0] , [0] [0] [z] = [0] [1] [0] orientation: [1 1 1 1 1] [1 1 1 1 1] [3] [1 1 1 1 1] [1 1 1 1 1] [2] [1 1 1 2 1] [1 1 1 2 1] [2] [1 1 1 2 1] [0 0 0 0 1] [1] t(f(x),g(y),f(z())) = [0 0 0 0 0]x + [0 0 0 0 0]y + [0] >= [0 0 0 0 0]x + [0 0 0 0 0]y + [0] = t(z(),g(x),g(y)) [0 0 0 0 0] [0 0 0 0 0] [0] [0 0 0 0 0] [0 0 0 0 0] [0] [0 0 0 0 0] [0 0 0 0 0] [0] [0 0 0 0 0] [0 0 0 0 0] [0] [1 1 1 1 1] [1 1 1 1 1] [3] [1 0 1 0 1] [1 1 1 1 1] [2] [1 1 1 1 1] [1 1 1 2 1] [2] [0 0 1 0 0] [1 1 1 2 1] [2] t(g(x),g(y),f(z())) = [0 0 0 1 0]x + [0 0 0 0 0]y + [0] >= [0 0 0 0 0]x + [0 0 0 0 0]y + [0] = t(f(y),f(z()),x) [0 0 0 1 0] [0 0 0 0 0] [0] [0 0 0 0 0] [0 0 0 0 0] [0] [0 0 0 1 0] [0 0 0 0 0] [0] [0 0 0 0 0] [0 0 0 0 0] [0] [1 1 1 1 1] [1 1 1 1 1] [0 0 0 0 0] [0 0 0 0 0] f(g(x)) = [0 0 0 1 0]x >= [0 0 0 1 0]x = g(f(x)) [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [1 1 1 1 1] [1 1 1 1 1] [0 0 0 0 0] [0 0 0 0 0] g(f(x)) = [0 0 0 1 0]x >= [0 0 0 1 0]x = f(g(x)) [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [1 1 1 2 1] [1 1 1 2 1] [0 0 0 0 0] [0 0 0 0 0] f(f(x)) = [0 0 0 0 0]x >= [0 0 0 0 0]x = g(g(x)) [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [1 1 1 2 1] [1 1 1 2 1] [0 0 0 0 0] [0 0 0 0 0] g(g(x)) = [0 0 0 0 0]x >= [0 0 0 0 0]x = f(f(x)) [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] problem: strict: weak: f(g(x)) -> g(f(x)) g(f(x)) -> f(g(x)) f(f(x)) -> g(g(x)) g(g(x)) -> f(f(x)) Qed