YES Problem: p(p(b(a(x0)),x1),p(x2,x3)) -> p(p(b(x2),a(a(b(x1)))),p(x3,x0)) Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 0 0] [0] [b](x0) = [0 0 0]x0 + [0] [0 0 1] [1], [1 0 0] [0] [a](x0) = [0 0 0]x0 + [0] [1 1 1] [1], [1 0 1] [1 1 0] [p](x0, x1) = [0 0 0]x0 + [0 0 1]x1 [0 0 0] [0 0 0] orientation: [2 1 1] [1 1 0] [1 0 1] [1 1 1] [2] [1 1 1] [1 0 0] [1 0 1] [1 0 1] [1] p(p(b(a(x0)),x1),p(x2,x3)) = [0 0 0]x0 + [0 0 0]x1 + [0 0 0]x2 + [0 0 0]x3 + [0] >= [0 0 0]x0 + [0 0 0]x1 + [0 0 0]x2 + [0 0 0]x3 + [0] = p(p(b(x2),a(a(b(x1)))),p(x3,x0)) [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] problem: Qed