YES Problem: b(c(x1)) -> c(b(x1)) c(b(x1)) -> a(a(a(x1))) a(a(a(a(x1)))) -> b(c(x1)) Proof: Arctic Interpretation Processor: dimension: 2 interpretation: [1 0] [a](x0) = [0 0]x0, [3 2] [b](x0) = [2 2]x0, [1 0 ] [c](x0) = [0 -&]x0 orientation: [4 3] [4 3] b(c(x1)) = [3 2]x1 >= [3 2]x1 = c(b(x1)) [4 3] [3 2] c(b(x1)) = [3 2]x1 >= [2 1]x1 = a(a(a(x1))) [4 3] [4 3] a(a(a(a(x1)))) = [3 2]x1 >= [3 2]x1 = b(c(x1)) problem: b(c(x1)) -> c(b(x1)) a(a(a(a(x1)))) -> b(c(x1)) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [a](x0) = [0 1]x0, [b](x0) = x0, [1 2] [c](x0) = [0 0]x0 orientation: [1 2] [1 2] b(c(x1)) = [0 0]x1 >= [0 0]x1 = c(b(x1)) [2 3] [1 2] a(a(a(a(x1)))) = [3 4]x1 >= [0 0]x1 = b(c(x1)) problem: b(c(x1)) -> c(b(x1)) KBO Processor: weight function: w0 = 1 w(b) = w(c) = 1 precedence: b > c problem: Qed