YES Problem: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) s(s(x)) -> x Proof: Church Rosser Transformation Processor (critical pair closing system, Thm 2.11): +(s(x28),x29) -> s(+(x28,x29)) s(s(x32)) -> x32 critical peaks: joinable Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0 + 2, [+](x0, x1) = x0 + 4x1 + 4 orientation: +(s(x28),x29) = x28 + 4x29 + 6 >= x28 + 4x29 + 6 = s(+(x28,x29)) s(s(x32)) = x32 + 4 >= x32 = x32 problem: +(s(x28),x29) -> s(+(x28,x29)) Matrix Interpretation Processor: dim=1 interpretation: [s](x0) = x0 + 1, [+](x0, x1) = 2x0 + 4x1 + 5 orientation: +(s(x28),x29) = 2x28 + 4x29 + 7 >= 2x28 + 4x29 + 6 = s(+(x28,x29)) problem: Qed