YES Problem: +(x,y) -> +(y,x) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(+(x,y),z) -> +(x,+(y,z)) Proof: AT confluence processor Complete TRS T' of input TRS: +(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(x50)) -> s(+(x,x50)) +(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:+(0(),y) -> y +(s(x),y) -> s(+(x,y)) +(x,0()) -> x +(x,s(x50)) -> s(+(x,x50)) S is left-linear and P is reversible. CP(S,S) = 0() = 0(), s(x50) = s(+(0(),x50)), s(+(x272,0())) = s(x272), s(+(x274,s(x50))) = s(+(s(x274),x50)), s(x) = s(+(x,0())), s(+(0(),x279)) = s(x279), s(+(s(x),x281)) = s(+(x,s(x281))) CP(S,P union P^-1) = y = +(y,0()), +(y,z) = +(0(),+(y,z)), x = +(x,0()), +(y,z) = +(+(0(),y),z), +(x,z) = +(+(x,0()),z), s(+(x323,y)) = +(y,s(x323)), +(s(+(x325,y)),z) = +(s(x325),+(y,z)), s(+(x327,x)) = +(x,s(x327)), s(+(x329,+(y,z))) = +(+(s(x329),y),z), +(x,s(+(x331,z))) = +(+(x,s(x331)),z), x = +(0(),x), +(x,y) = +(x,+(y,0())), +(x,z) = +(x,+(0(),z)), y = +(0(),y), +(x,y) = +(+(x,y),0()), s(+(x,x339)) = +(s(x339),x), s(+(+(x,y),x341)) = +(x,+(y,s(x341))), +(s(+(x,x343)),z) = +(x,+(s(x343),z)), s(+(y,x345)) = +(s(x345),y), +(x,s(+(y,x347))) = +(+(x,y),s(x347)) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [0] = 5, [+](x0, x1) = x0 + 3x1, [s](x0) = x0 + 7 orientation: +(0(),y) = 3y + 5 >= y = y +(s(x),y) = x + 3y + 7 >= x + 3y + 7 = s(+(x,y)) +(x,0()) = x + 15 >= x = x +(x,s(x50)) = x + 3x50 + 21 >= x + 3x50 + 7 = s(+(x,x50)) problem: +(s(x),y) -> s(+(x,y)) Matrix Interpretation Processor: dim=1 interpretation: [+](x0, x1) = 2x0 + 4x1 + 7, [s](x0) = x0 + 1 orientation: +(s(x),y) = 2x + 4y + 9 >= 2x + 4y + 8 = s(+(x,y)) problem: Qed