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 ] [g](x0) = [0 -& 2 ]x0 [-& -& -&] , [0 0 2] [f](x0) = [0 0 3]x0 [0 0 1] orientation: [2 2 3] [0 0 2] f(g(f(x))) = [2 2 3]x >= [0 0 2]x = f(g(g(g(f(x))))) [2 2 3] [0 0 2] [0 -& 0 ] [0 -& 0 ] g(x) = [0 -& 2 ]x >= [0 -& 0 ]x = g(g(x)) [-& -& -&] [-& -& -&] [0 -& 0 ] [0 -& 0 ] g(x) = [0 -& 2 ]x >= [0 -& 0 ]x = g(g(f(g(g(x))))) [-& -& -&] [-& -& -&] [0 0 2] [0 -& 0 ] f(x) = [0 0 3]x >= [0 -& 0 ]x = g(g(f(g(g(x))))) [0 0 1] [-& -& -&] 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