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