YES Problem: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,y) -> +(y,x) Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(x20)) -> s(+(x,x20)) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(x,y) -> +(y,x) TRS S:+(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(x20)) -> s(+(x,x20)) S is left-linear and P is reversible. CP(S,S) = 0() = 0(), s(x20) = s(+(0(),x20)), s(+(x172,0())) = s(x172), s(+(x174,s(x20))) = s(+(s(x174),x20)), s(x) = s(+(x,0())), s(+(0(),x179)) = s(x179), s(+(s(x),x181)) = s(+(x,s(x181))) CP(S,P union P^-1) = y = +(y,0()), x = +(x,0()), s(+(x196,y)) = +(y,s(x196)), s(+(x198,x)) = +(x,s(x198)), x = +(0(),x), y = +(0(),y), s(+(x,x203)) = +(s(x203),x), s(+(y,x205)) = +(s(x205),y) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 3x1, [0] = 5, [s](x0) = x0 + 7 orientation: +(0(),y) = 3y + 5 >= y = y +(s(x),y) = x + 3y + 7 >= x + 3y + 7 = s(+(x,y)) +(x,0()) = x + 15 >= x = x +(x,s(x20)) = x + 3x20 + 21 >= x + 3x20 + 7 = s(+(x,x20)) problem: +(s(x),y) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + 4x1 + 7, [s](x0) = x0 + 1 orientation: +(s(x),y) = 2x + 4y + 9 >= 2x + 4y + 8 = s(+(x,y)) problem: Qed