YES Problem: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) *(k(),0()) -> 0() *(k(),s(y)) -> +(k(),*(k(),y)) +(x,y) -> +(y,x) +(+(x,y),z) -> +(x,+(y,z)) Proof: AT confluence processor Complete TRS T' of input TRS: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) *(k(),0()) -> 0() *(k(),s(y)) -> +(k(),*(k(),y)) +(x,y) -> +(y,x) +(+(x,y),z) -> +(x,+(y,z)) T' = (P union S) with TRS P:+(x,y) -> +(y,x) +(+(x,y),z) -> +(x,+(y,z)) TRS S:+(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) *(k(),0()) -> 0() *(k(),s(y)) -> +(k(),*(k(),y)) S is left-linear and P is reversible. CP(S,S) = 0() = 0(), s(x) = s(+(x,0())), s(+(0(),x366)) = s(x366), s(+(s(x),x368)) = s(+(x,s(x368))), s(y) = s(+(0(),y)), s(+(x371,0())) = s(x371), s(+(x373,s(y))) = s(+(s(x373),y)) CP(S,P union P^-1) = x = +(0(),x), +(x,y) = +(x,+(y,0())), +(x,z) = +(x,+(0(),z)), y = +(0(),y), +(x,y) = +(+(x,y),0()), s(+(x,x423)) = +(s(x423),x), s(+(+(x,y),x425)) = +(x,+(y,s(x425))), +(s(+(x,x427)),z) = +(x,+(s(x427),z)), s(+(y,x429)) = +(s(x429),y), +(x,s(+(y,x431))) = +(+(x,y),s(x431)), y = +(y,0()), +(y,z) = +(0(),+(y,z)), x = +(x,0()), +(y,z) = +(+(0(),y),z), +(x,z) = +(+(x,0()),z), s(+(x437,y)) = +(y,s(x437)), +(s(+(x439,y)),z) = +(s(x439),+(y,z)), s(+(x441,x)) = +(x,s(x441)), s(+(x443,+(y,z))) = +(+(s(x443),y),z), +(x,s(+(x445,z))) = +(+(x,s(x445)),z) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [*](x0, x1) = 4x0 + 4x1, [+](x0, x1) = x0 + x1 + 5, [k] = 0, [0] = 0, [s](x0) = x0 + 2 orientation: +(x,0()) = x + 5 >= x = x +(x,s(y)) = x + y + 7 >= x + y + 7 = s(+(x,y)) +(0(),y) = y + 5 >= y = y +(s(x),y) = x + y + 7 >= x + y + 7 = s(+(x,y)) *(k(),0()) = 0 >= 0 = 0() *(k(),s(y)) = 4y + 8 >= 4y + 5 = +(k(),*(k(),y)) problem: +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,y)) *(k(),0()) -> 0() Matrix Interpretation Processor: dim=1 interpretation: [*](x0, x1) = 4x0 + 2x1 + 4, [+](x0, x1) = x0 + x1 + 4, [k] = 2, [0] = 2, [s](x0) = x0 + 1 orientation: +(x,s(y)) = x + y + 5 >= x + y + 5 = s(+(x,y)) +(s(x),y) = x + y + 5 >= x + y + 5 = s(+(x,y)) *(k(),0()) = 16 >= 2 = 0() problem: +(x,s(y)) -> s(+(x,y)) +(s(x),y) -> s(+(x,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(x),y) = x + 4y + 6 >= x + 4y + 6 = 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