YES Problem: a(s(x1)) -> s(a(x1)) b(a(b(s(x1)))) -> a(b(s(a(x1)))) b(a(b(b(x1)))) -> c(s(x1)) c(s(x1)) -> a(b(a(b(x1)))) a(b(a(a(x1)))) -> b(a(b(a(x1)))) Proof: String Reversal Processor: s(a(x1)) -> a(s(x1)) s(b(a(b(x1)))) -> a(s(b(a(x1)))) b(b(a(b(x1)))) -> s(c(x1)) s(c(x1)) -> b(a(b(a(x1)))) a(a(b(a(x1)))) -> a(b(a(b(x1)))) Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = 8x0 + 15, [b](x0) = 2x0 + 2, [a](x0) = 2x0 + 2, [s](x0) = 2x0 orientation: s(a(x1)) = 4x1 + 4 >= 4x1 + 2 = a(s(x1)) s(b(a(b(x1)))) = 16x1 + 28 >= 16x1 + 26 = a(s(b(a(x1)))) b(b(a(b(x1)))) = 16x1 + 30 >= 16x1 + 30 = s(c(x1)) s(c(x1)) = 16x1 + 30 >= 16x1 + 30 = b(a(b(a(x1)))) a(a(b(a(x1)))) = 16x1 + 30 >= 16x1 + 30 = a(b(a(b(x1)))) problem: b(b(a(b(x1)))) -> s(c(x1)) s(c(x1)) -> b(a(b(a(x1)))) a(a(b(a(x1)))) -> a(b(a(b(x1)))) Matrix Interpretation Processor: dim=4 interpretation: [1 0 0 1] [1] [0 1 0 0] [1] [c](x0) = [0 0 1 1]x0 + [1] [0 0 1 0] [0], [1 1 0 0] [0] [0 1 1 1] [0] [b](x0) = [0 0 0 0]x0 + [1] [0 0 0 0] [0], [1 0 0 1] [0] [0 0 0 0] [1] [a](x0) = [0 0 1 0]x0 + [0] [0 1 0 1] [0], [1 0 0 1] [1] [0 1 1 0] [1] [s](x0) = [0 0 0 0]x0 + [1] [0 0 0 0] [0] orientation: [1 2 1 1] [3] [1 0 1 1] [2] [0 1 1 1] [3] [0 1 1 1] [3] b(b(a(b(x1)))) = [0 0 0 0]x1 + [1] >= [0 0 0 0]x1 + [1] = s(c(x1)) [0 0 0 0] [0] [0 0 0 0] [0] [1 0 1 1] [2] [1 0 0 1] [2] [0 1 1 1] [3] [0 1 1 1] [3] s(c(x1)) = [0 0 0 0]x1 + [1] >= [0 0 0 0]x1 + [1] = b(a(b(a(x1)))) [0 0 0 0] [0] [0 0 0 0] [0] [1 1 1 2] [2] [1 1 0 0] [1] [0 0 0 0] [1] [0 0 0 0] [1] a(a(b(a(x1)))) = [0 0 0 0]x1 + [1] >= [0 0 0 0]x1 + [1] = a(b(a(b(x1)))) [0 1 1 1] [2] [0 1 1 1] [2] problem: s(c(x1)) -> b(a(b(a(x1)))) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [c](x0) = [3 2]x0, [0 -&] [b](x0) = [-& -&]x0, [2 0] [a](x0) = [3 3]x0, [0 2 ] [s](x0) = [-& -&]x0 orientation: [5 4 ] [4 2 ] s(c(x1)) = [-& -&]x1 >= [-& -&]x1 = b(a(b(a(x1)))) problem: Qed