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