YES Problem: +(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) +(x,+(y,z)) -> +(+(x,y),z) +(+(x,y),z) -> +(x,+(y,z)) 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,z)) -> +(+(x,y),z) +(+(x,y),z) -> +(x,+(y,z)) T' = (P union S) with TRS P:+(x,+(y,z)) -> +(+(x,y),z) +(+(x,y),z) -> +(x,+(y,z)) TRS S:+(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) S is linear and P is reversible. CP(S,S) = 0() = 0(), s(y) = s(+(0(),y)), s(x) = s(+(x,0())), s(+(x319,0())) = s(x319), s(+(x321,s(y))) = s(+(s(x321),y)), s(+(0(),x324)) = s(x324), s(+(s(x),x326)) = s(+(x,s(x326))) CP(S,P union P^-1) = +(y,z) = +(+(0(),y),z), +(x,z) = +(+(x,0()),z), +(y,z) = +(0(),+(y,z)), +(x,y) = +(+(x,y),0()), +(x,y) = +(x,+(y,0())), +(x,z) = +(x,+(0(),z)), s(+(x357,+(y,z))) = +(+(s(x357),y),z), +(x,s(+(x359,z))) = +(+(x,s(x359)),z), +(s(+(x361,y)),z) = +(s(x361),+(y,z)), +(x,s(+(y,x364))) = +(+(x,y),s(x364)), s(+(+(x,y),x366)) = +(x,+(y,s(x366))), +(s(+(x,x368)),z) = +(x,+(s(x368),z)) CP(P union P^-1,S) = +(+(0(),x418),x419) = +(x418,x419), +(+(s(x),x421),x422) = s(+(x,+(x421,x422))), +(x423,+(x424,0())) = +(x423,x424), +(x426,+(x427,s(y))) = s(+(+(x426,x427),y)) We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + x1 + 2, [0] = 2, [s](x0) = x0 + 2 orientation: +(0(),y) = y + 6 >= y = y +(x,0()) = 2x + 4 >= x = x +(s(x),y) = 2x + y + 6 >= 2x + y + 4 = s(+(x,y)) +(x,s(y)) = 2x + y + 4 >= 2x + y + 4 = s(+(x,y)) problem: +(x,s(y)) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 4x1, [s](x0) = x0 + 5 orientation: +(x,s(y)) = x + 4y + 20 >= x + 4y + 5 = s(+(x,y)) problem: Qed