YES Problem: +(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) +(x,y) -> +(y,x) Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(x,y) -> +(y,x) TRS S:+(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) S is left-linear and P is reversible. CP(S,S) = 0() = 0(), s(y) = s(+(0(),y)), s(x) = s(+(x,0())), s(+(x154,0())) = s(x154), s(+(x156,s(y))) = s(+(s(x156),y)), s(+(0(),x159)) = s(x159), s(+(s(x),x161)) = s(+(x,s(x161))) CP(S,P union P^-1) = y = +(y,0()), x = +(x,0()), x = +(0(),x), y = +(0(),y), s(+(x178,y)) = +(y,s(x178)), s(+(x180,x)) = +(x,s(x180)), s(+(x,x183)) = +(s(x183),x), s(+(y,x185)) = +(s(x185),y) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 4x0 + 6x1 + 2, [0] = 0, [s](x0) = x0 + 3 orientation: +(0(),y) = 6y + 2 >= y = y +(x,0()) = 4x + 2 >= x = x +(s(x),y) = 4x + 6y + 14 >= 4x + 6y + 5 = s(+(x,y)) +(x,s(y)) = 4x + 6y + 20 >= 4x + 6y + 5 = s(+(x,y)) problem: Qed