YES(?,O(n^2)) Problem: g(f(x,y),z) -> f(x,g(y,z)) g(h(x,y),z) -> g(x,f(y,z)) g(x,h(y,z)) -> h(g(x,y),z) Proof: RT Transformation Processor: strict: g(f(x,y),z) -> f(x,g(y,z)) g(h(x,y),z) -> g(x,f(y,z)) g(x,h(y,z)) -> h(g(x,y),z) weak: Matrix Interpretation Processor: dimension: 1 interpretation: [h](x0, x1) = x0 + x1 + 1, [g](x0, x1) = x0 + x1, [f](x0, x1) = x0 + x1 orientation: g(f(x,y),z) = x + y + z >= x + y + z = f(x,g(y,z)) g(h(x,y),z) = x + y + z + 1 >= x + y + z = g(x,f(y,z)) g(x,h(y,z)) = x + y + z + 1 >= x + y + z + 1 = h(g(x,y),z) problem: strict: g(f(x,y),z) -> f(x,g(y,z)) g(x,h(y,z)) -> h(g(x,y),z) weak: g(h(x,y),z) -> g(x,f(y,z)) Matrix Interpretation Processor: dimension: 2 interpretation: [1 2] [2] [h](x0, x1) = x0 + [0 0]x1 + [9], [1 2] [1 2] [2 ] [g](x0, x1) = [0 1]x0 + [0 1]x1 + [10], [1 0] [3] [f](x0, x1) = [0 0]x0 + x1 + [6] orientation: [1 0] [1 2] [1 2] [17] [1 0] [1 2] [1 2] [5 ] g(f(x,y),z) = [0 0]x + [0 1]y + [0 1]z + [16] >= [0 0]x + [0 1]y + [0 1]z + [16] = f(x,g(y,z)) [1 2] [1 2] [1 2] [22] [1 2] [1 2] [1 2] [4 ] g(x,h(y,z)) = [0 1]x + [0 1]y + [0 0]z + [19] >= [0 1]x + [0 1]y + [0 0]z + [19] = h(g(x,y),z) [1 2] [1 2] [1 2] [22] [1 2] [1 0] [1 2] [17] g(h(x,y),z) = [0 1]x + [0 0]y + [0 1]z + [19] >= [0 1]x + [0 0]y + [0 1]z + [16] = g(x,f(y,z)) problem: strict: weak: g(f(x,y),z) -> f(x,g(y,z)) g(x,h(y,z)) -> h(g(x,y),z) g(h(x,y),z) -> g(x,f(y,z)) Qed