YES Problem: and3(x,y,F()) -> F() and3(T(),T(),T()) -> T() and3(x,y,z) -> and3(y,z,x) Proof: AT confluence processor Complete TRS T' of input TRS: and3(x,y,F()) -> F() and3(T(),T(),T()) -> T() and3(y,F(),x) -> F() and3(F(),y,z) -> F() and3(x,y,z) -> and3(y,z,x) T' = (P union S) with TRS P:and3(x,y,z) -> and3(y,z,x) TRS S:and3(x,y,F()) -> F() and3(T(),T(),T()) -> T() and3(y,F(),x) -> F() and3(F(),y,z) -> F() S is left-linear and P is reversible. CP(S,S) = F() = F() CP(S,P union P^-1) = F() = and3(y,F(),x), F() = and3(F(),y,z), T() = and3(T(),T(),T()), F() = and3(F(),z,x), F() = and3(x,y,F()), F() = and3(y,z,F()), F() = and3(x,F(),z) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [and3](x0, x1, x2) = x0 + 2x1 + 2x2, [F] = 6, [T] = 0 orientation: and3(x,y,F()) = x + 2y + 12 >= 6 = F() and3(T(),T(),T()) = 0 >= 0 = T() and3(y,F(),x) = 2x + y + 12 >= 6 = F() and3(F(),y,z) = 2y + 2z + 6 >= 6 = F() problem: and3(T(),T(),T()) -> T() and3(F(),y,z) -> F() Matrix Interpretation Processor: dim=1 interpretation: [and3](x0, x1, x2) = x0 + 4x1 + 2x2, [F] = 0, [T] = 4 orientation: and3(T(),T(),T()) = 28 >= 4 = T() and3(F(),y,z) = 4y + 2z >= 0 = F() problem: and3(F(),y,z) -> F() Matrix Interpretation Processor: dim=1 interpretation: [and3](x0, x1, x2) = x0 + 2x1 + 4x2 + 1, [F] = 0 orientation: and3(F(),y,z) = 2y + 4z + 1 >= 0 = F() problem: Qed