YES Problem: +(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: +(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:+(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) S is left-linear and P is reversible. CP(S,S) = s(+(x62,s(y))) = s(+(s(x62),y)), s(+(s(x),x65)) = s(+(x,s(x65))) CP(S,P union P^-1) = s(+(x74,y)) = +(y,s(x74)), s(+(x76,x)) = +(x,s(x76)), s(+(x,x79)) = +(s(x79),x), s(+(y,x81)) = +(s(x81),y) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 2x1 + 7, [s](x0) = x0 + 6 orientation: +(s(x),y) = x + 2y + 13 >= x + 2y + 13 = s(+(x,y)) +(x,s(y)) = x + 2y + 19 >= x + 2y + 13 = s(+(x,y)) problem: +(s(x),y) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 6x0 + x1 + 2, [s](x0) = x0 + 3 orientation: +(s(x),y) = 6x + y + 20 >= 6x + y + 5 = s(+(x,y)) problem: Qed