YES Problem: a(x) -> x a(a(x)) -> b(c(x)) b(x) -> x c(x) -> x c(b(x)) -> b(a(c(x))) Proof: Church Rosser Transformation Processor (critical pair closing system, Thm 2.11): a(x47) -> x47 c(x48) -> x48 b(x49) -> x49 critical peaks: joinable Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = x0 + 1, [a](x0) = x0 + 1, [b](x0) = x0 + 1 orientation: a(x47) = x47 + 1 >= x47 = x47 c(x48) = x48 + 1 >= x48 = x48 b(x49) = x49 + 1 >= x49 = x49 problem: Qed