YES Problem: strict: f(g(f(x))) -> f(g(g(g(f(x))))) weak: g(x) -> g(g(x)) g(x) -> g(g(f(g(g(x))))) f(x) -> g(g(f(g(g(x))))) Proof: Arctic Interpretation Processor: dimension: 3 interpretation: [0 0 0 ] [g](x0) = [-& -& 0 ]x0 [-& -& -&] , [0 1 0] [f](x0) = [0 1 0]x0 [0 1 0] orientation: [1 2 1] [0 1 0] f(g(f(x))) = [1 2 1]x >= [0 1 0]x = f(g(g(g(f(x))))) [1 2 1] [0 1 0] [0 0 0 ] [0 0 0 ] g(x) = [-& -& 0 ]x >= [-& -& -&]x = g(g(x)) [-& -& -&] [-& -& -&] [0 0 0 ] [0 0 0 ] g(x) = [-& -& 0 ]x >= [-& -& -&]x = g(g(f(g(g(x))))) [-& -& -&] [-& -& -&] [0 1 0] [0 0 0 ] f(x) = [0 1 0]x >= [-& -& -&]x = g(g(f(g(g(x))))) [0 1 0] [-& -& -&] problem: strict: weak: g(x) -> g(g(x)) g(x) -> g(g(f(g(g(x))))) f(x) -> g(g(f(g(g(x))))) Qed