YES Problem: F(H(x),y) -> F(H(x),I(I(y))) F(x,G(y)) -> F(I(x),G(y)) I(x) -> x Proof: Church Rosser Transformation Processor (critical pair closing system, Thm 2.11): I(H(x31)) -> H(x31) F(H(x33),G(x32)) -> F(H(x33),I(I(G(x32)))) critical peaks: joinable Matrix Interpretation Processor: dim=2 interpretation: [1 1] [0] [G](x0) = [0 0]x0 + [2], [1 0] [I](x0) = [0 0]x0, [2 0] [2 1] [0] [F](x0, x1) = [0 0]x0 + [0 0]x1 + [2], [2 0] [H](x0) = [0 0]x0 orientation: [2 0] [2 0] I(H(x31)) = [0 0]x31 >= [0 0]x31 = H(x31) [2 2] [4 0] [2] [2 2] [4 0] [0] F(H(x33),G(x32)) = [0 0]x32 + [0 0]x33 + [2] >= [0 0]x32 + [0 0]x33 + [2] = F(H(x33),I(I(G(x32)))) problem: I(H(x31)) -> H(x31) Matrix Interpretation Processor: dim=1 interpretation: [I](x0) = x0 + 1, [H](x0) = x0 + 4 orientation: I(H(x31)) = x31 + 5 >= x31 + 4 = H(x31) problem: Qed