YES Problem: +(0(),y) -> y +(x,s(y)) -> s(+(x,y)) +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(x,s(y)) -> s(+(x,y)) +(x,0()) -> x +(s(x55),y) -> s(+(x55,y)) +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) T' = (P union S) with TRS P:+(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) TRS S:+(0(),y) -> y +(x,s(y)) -> s(+(x,y)) +(x,0()) -> x +(s(x55),y) -> s(+(x55,y)) S is left-linear and P is reversible. CP(S,S) = s(y) = s(+(0(),y)), 0() = 0(), s(+(0(),x273)) = s(x273), s(+(s(x55),x275)) = s(+(x55,s(x275))), s(x55) = s(+(x55,0())), s(+(x278,s(y))) = s(+(s(x278),y)), s(+(x280,0())) = s(x280) CP(S,P union P^-1) = +(y,z) = +(0(),+(y,z)), y = +(y,0()), +(y,z) = +(+(0(),y),z), +(x,z) = +(+(x,0()),z), x = +(x,0()), s(+(+(x,y),x324)) = +(x,+(y,s(x324))), +(s(+(x,x326)),z) = +(x,+(s(x326),z)), s(+(x,x328)) = +(s(x328),x), +(x,s(+(y,x330))) = +(+(x,y),s(x330)), s(+(y,x332)) = +(s(x332),y), +(x,y) = +(x,+(y,0())), +(x,z) = +(x,+(0(),z)), x = +(0(),x), +(x,y) = +(+(x,y),0()), y = +(0(),y), +(s(+(x338,y)),z) = +(s(x338),+(y,z)), s(+(x340,y)) = +(y,s(x340)), s(+(x342,+(y,z))) = +(+(s(x342),y),z), +(x,s(+(x344,z))) = +(+(x,s(x344)),z), s(+(x346,x)) = +(x,s(x346)) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 4x0 + x1 + 7, [0] = 0, [s](x0) = x0 orientation: +(0(),y) = y + 7 >= y = y +(x,s(y)) = 4x + y + 7 >= 4x + y + 7 = s(+(x,y)) +(x,0()) = 4x + 7 >= x = x +(s(x55),y) = 4x55 + y + 7 >= 4x55 + y + 7 = s(+(x55,y)) problem: +(x,s(y)) -> s(+(x,y)) +(s(x55),y) -> s(+(x55,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = x0 + 4x1 + 5, [s](x0) = x0 + 1 orientation: +(x,s(y)) = x + 4y + 9 >= x + 4y + 6 = s(+(x,y)) +(s(x55),y) = x55 + 4y + 6 >= x55 + 4y + 6 = s(+(x55,y)) problem: +(s(x55),y) -> s(+(x55,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 6x0 + x1 + 2, [s](x0) = x0 + 3 orientation: +(s(x55),y) = 6x55 + y + 20 >= 6x55 + y + 5 = s(+(x55,y)) problem: Qed