YES Problem: f(f(x,y),z) -> f(x,f(y,z)) f(i(x1),x1) -> e() Proof: Matrix Interpretation Processor: dimension: 1 interpretation: [e] = 0, [i](x0) = x0 + 1, [f](x0, x1) = x0 + x1 orientation: f(f(x,y),z) = x + y + z >= x + y + z = f(x,f(y,z)) f(i(x1),x1) = 2x1 + 1 >= 0 = e() problem: f(f(x,y),z) -> f(x,f(y,z)) Matrix Interpretation Processor: dimension: 1 interpretation: [f](x0, x1) = 2x0 + x1 + 1 orientation: f(f(x,y),z) = 4x + 2y + z + 3 >= 2x + 2y + z + 2 = f(x,f(y,z)) problem: Qed