YES Problem: b(a(a(x1))) -> a(b(c(x1))) c(a(x1)) -> a(c(x1)) b(c(a(x1))) -> a(b(c(x1))) c(b(x1)) -> b(a(x1)) a(c(b(x1))) -> c(b(a(x1))) Proof: Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = 2x0 + 3, [b](x0) = x0 + 1, [a](x0) = 2x0 + 4 orientation: b(a(a(x1))) = 4x1 + 13 >= 4x1 + 12 = a(b(c(x1))) c(a(x1)) = 4x1 + 11 >= 4x1 + 10 = a(c(x1)) b(c(a(x1))) = 4x1 + 12 >= 4x1 + 12 = a(b(c(x1))) c(b(x1)) = 2x1 + 5 >= 2x1 + 5 = b(a(x1)) a(c(b(x1))) = 4x1 + 14 >= 4x1 + 13 = c(b(a(x1))) problem: b(c(a(x1))) -> a(b(c(x1))) c(b(x1)) -> b(a(x1)) Arctic Interpretation Processor: dimension: 2 interpretation: [2 -&] [c](x0) = [2 0 ]x0, [0 2] [b](x0) = [0 0]x0, [0 2 ] [a](x0) = [-& 0 ]x0 orientation: [4 6] [4 2] b(c(a(x1))) = [2 4]x1 >= [2 0]x1 = a(b(c(x1))) [2 4] [0 2] c(b(x1)) = [2 4]x1 >= [0 2]x1 = b(a(x1)) problem: b(c(a(x1))) -> a(b(c(x1))) KBO Processor: weight function: w0 = 1 w(c) = w(b) = w(a) = 1 precedence: b > c ~ a problem: Qed