YES Problem: a(b(x1)) -> b(a(x1)) b(a(x1)) -> a(a(c(b(x1)))) Proof: Arctic Interpretation Processor: dimension: 2 interpretation: [0 -&] [c](x0) = [-& -&]x0, [0 0] [a](x0) = [0 1]x0, [0 1] [b](x0) = [1 2]x0 orientation: [1 2] [1 2] a(b(x1)) = [2 3]x1 >= [2 3]x1 = b(a(x1)) [1 2] [0 1] b(a(x1)) = [2 3]x1 >= [1 2]x1 = a(a(c(b(x1)))) problem: a(b(x1)) -> b(a(x1)) KBO Processor: weight function: w0 = 1 w(a) = w(b) = 1 precedence: a > b problem: Qed