YES Problem: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) T' = (P union S) with TRS P: TRS S:+(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(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(+(x112,0())) = s(x112), s(+(x114,s(y))) = s(+(s(x114),y)), s(x) = s(+(x,0())), s(+(0(),x119)) = s(x119), s(+(s(x),x121)) = s(+(x,s(x121))) CP(S,P union P^-1) = PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + 2x1 + 5, [0] = 1, [s](x0) = x0 orientation: +(0(),y) = 2y + 7 >= y = y +(s(x),y) = 2x + 2y + 5 >= 2x + 2y + 5 = s(+(x,y)) +(x,0()) = 2x + 7 >= x = x +(x,s(y)) = 2x + 2y + 5 >= 2x + 2y + 5 = s(+(x,y)) problem: +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) 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