YES Problem: a(b(a(x1))) -> b(b(b(b(x1)))) a(b(b(x1))) -> b(b(a(a(x1)))) Proof: Arctic Interpretation Processor: dimension: 3 interpretation: [0 0 0 ] [b](x0) = [-& -& 0 ]x0 [-& 0 -&] , [0 1 0 ] [a](x0) = [-& 0 -&]x0 [0 1 0 ] orientation: [1 2 1] [0 0 0 ] a(b(a(x1))) = [0 1 0]x1 >= [-& 0 -&]x1 = b(b(b(b(x1)))) [1 2 1] [-& -& 0 ] [0 1 0 ] [0 1 0 ] a(b(b(x1))) = [-& 0 -&]x1 >= [-& 0 -&]x1 = b(b(a(a(x1)))) [0 1 0 ] [0 1 0 ] 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