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