YES Problem: a(b(x)) -> b(a(x)) a(c(x)) -> x Proof: DP Processor: DPs: a#(b(x)) -> a#(x) TRS: a(b(x)) -> b(a(x)) a(c(x)) -> x Matrix Interpretation Processor: dim=3 interpretation: [a#](x0) = [0 1 0]x0 + [1], [1 1 0] [c](x0) = [0 0 0]x0 [1 1 1] , [1 0 0] [a](x0) = [0 0 1]x0 [0 0 1] , [0 0 0] [1] [b](x0) = [0 1 0]x0 + [1] [0 0 1] [1] orientation: a#(b(x)) = [0 1 0]x + [2] >= [0 1 0]x + [1] = a#(x) [0 0 0] [1] [0 0 0] [1] a(b(x)) = [0 0 1]x + [1] >= [0 0 1]x + [1] = b(a(x)) [0 0 1] [1] [0 0 1] [1] [1 1 0] a(c(x)) = [1 1 1]x >= x = x [1 1 1] problem: DPs: TRS: a(b(x)) -> b(a(x)) a(c(x)) -> x Qed