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