YES Problem: a(a(b(d(b(d(a(x1))))))) -> a(a(c(a(a(b(d(x1))))))) a(a(c(x1))) -> c(c(a(a(x1)))) c(c(c(x1))) -> b(d(c(b(d(x1))))) Proof: Matrix Interpretation Processor: dim=3 interpretation: [1 0 0] [c](x0) = [0 1 0]x0 [0 0 0] , [1 0 0] [b](x0) = [0 0 1]x0 [0 0 1] , [1 0 0] [d](x0) = [0 0 0]x0 [0 0 1] , [1 1 0] [0] [a](x0) = [0 0 0]x0 + [0] [0 0 1] [1] orientation: [1 1 1] [1] [1 0 1] [0] a(a(b(d(b(d(a(x1))))))) = [0 0 0]x1 + [0] >= [0 0 0]x1 + [0] = a(a(c(a(a(b(d(x1))))))) [0 0 1] [3] [0 0 0] [2] [1 1 0] [0] [1 1 0] a(a(c(x1))) = [0 0 0]x1 + [0] >= [0 0 0]x1 = c(c(a(a(x1)))) [0 0 0] [2] [0 0 0] [1 0 0] [1 0 0] c(c(c(x1))) = [0 1 0]x1 >= [0 0 0]x1 = b(d(c(b(d(x1))))) [0 0 0] [0 0 0] problem: a(a(c(x1))) -> c(c(a(a(x1)))) c(c(c(x1))) -> b(d(c(b(d(x1))))) Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = x0 + 1, [b](x0) = x0, [d](x0) = x0 + 1, [a](x0) = 4x0 orientation: a(a(c(x1))) = 16x1 + 16 >= 16x1 + 2 = c(c(a(a(x1)))) c(c(c(x1))) = x1 + 3 >= x1 + 3 = b(d(c(b(d(x1))))) problem: c(c(c(x1))) -> b(d(c(b(d(x1))))) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [c](x0) = [2 0]x0, [0 0 ] [b](x0) = [-& -&]x0, [0 -&] [d](x0) = [0 -&]x0 orientation: [2 2] [0 -&] c(c(c(x1))) = [4 2]x1 >= [-& -&]x1 = b(d(c(b(d(x1))))) problem: Qed