YES Problem: +(0(),y) -> y +(s(0()),y) -> s(+(0(),y)) +(x,y) -> +(y,x) s(s(x)) -> x Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(s(0()),y) -> s(+(0(),y)) s(s(x)) -> x +(y,0()) -> y +(y,s(0())) -> s(y) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(x,y) -> +(y,x) TRS S:+(0(),y) -> y +(s(0()),y) -> s(+(0(),y)) s(s(x)) -> x +(y,0()) -> y +(y,s(0())) -> s(y) S is linear and P is reversible. CP(S,S) = 0() = 0(), s(0()) = s(0()), s(+(0(),0())) = s(0()), s(+(0(),s(0()))) = s(s(0())), s(x253) = s(x253), s(0()) = s(+(0(),0())), s(s(0())) = s(+(0(),s(0()))) CP(S,P union P^-1) = y = +(y,0()), x = +(x,0()), s(+(0(),y)) = +(y,s(0())), s(+(0(),x)) = +(x,s(0())), x = +(0(),x), y = +(0(),y), s(x) = +(s(0()),x), s(y) = +(s(0()),y) CP(P union P^-1,S) = +(y,0()) = y, +(y,s(0())) = s(+(0(),y)), +(0(),y) = y, +(s(0()),y) = s(y) We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + x1 + 3, [0] = 0, [s](x0) = x0 + 2 orientation: +(0(),y) = y + 3 >= y = y +(s(0()),y) = y + 5 >= y + 5 = s(+(0(),y)) s(s(x)) = x + 4 >= x = x +(y,0()) = y + 3 >= y = y +(y,s(0())) = y + 5 >= y + 2 = s(y) problem: +(s(0()),y) -> s(+(0(),y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + 4x1 + 1, [0] = 0, [s](x0) = x0 + 1 orientation: +(s(0()),y) = 4y + 3 >= 4y + 2 = s(+(0(),y)) problem: Qed