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