YES Problem: not(T()) -> F() not(F()) -> T() or(x,T()) -> T() or(x,F()) -> x or(x,y) -> or(y,x) or(or(x,y),z) -> or(x,or(y,z)) and(x,T()) -> x and(x,F()) -> F() and(x,y) -> and(y,x) and(and(x,y),z) -> and(x,and(y,z)) imply(x,y) -> or(not(x),y) Proof: sorted: (order) 0:not(T()) -> F() not(F()) -> T() or(x,T()) -> T() or(x,F()) -> x or(x,y) -> or(y,x) or(or(x,y),z) -> or(x,or(y,z)) imply(x,y) -> or(not(x),y) 1:and(x,T()) -> x and(x,F()) -> F() and(x,y) -> and(y,x) and(and(x,y),z) -> and(x,and(y,z)) ----- sorts [0>2, 1>7, 1>8, 2>3, 2>4, 4>5, 5>6, 5>7, 5>8] sort attachment (non-strict) not : 5 -> 4 T : 8 F : 7 or : 2 x 2 -> 2 and : 1 x 1 -> 1 imply : 6 x 3 -> 0 ----- 0:not(T()) -> F() not(F()) -> T() or(x,T()) -> T() or(x,F()) -> x or(x,y) -> or(y,x) or(or(x,y),z) -> or(x,or(y,z)) imply(x,y) -> or(not(x),y) AT confluence processor Complete TRS T' of input TRS: not(T()) -> F() not(F()) -> T() or(x,T()) -> T() or(x,F()) -> x imply(x,y) -> or(not(x),y) or(T(),x) -> T() or(F(),x) -> x or(x,y) -> or(y,x) or(or(x,y),z) -> or(x,or(y,z)) T' = (P union S) with TRS P:or(x,y) -> or(y,x) or(or(x,y),z) -> or(x,or(y,z)) TRS S:not(T()) -> F() not(F()) -> T() or(x,T()) -> T() or(x,F()) -> x imply(x,y) -> or(not(x),y) or(T(),x) -> T() or(F(),x) -> x S is linear and P is reversible. CP(S,S) = T() = T(), F() = F() CP(S,P union P^-1) = T() = or(T(),x), T() = or(x,or(y,T())), or(T(),z) = or(x,or(T(),z)), T() = or(T(),y), or(x,T()) = or(or(x,y),T()), x = or(F(),x), or(x,y) = or(x,or(y,F())), or(x,z) = or(x,or(F(),z)), y = or(F(),y), or(x,y) = or(or(x,y),F()), T() = or(y,T()), or(T(),z) = or(T(),or(y,z)), T() = or(x,T()), T() = or(or(T(),y),z), or(x,T()) = or(or(x,T()),z), y = or(y,F()), or(y,z) = or(F(),or(y,z)), x = or(x,F()), or(y,z) = or(or(F(),y),z), or(x,z) = or(or(x,F()),z) CP(P union P^-1,S) = or(T(),x) = T(), or(F(),x) = x, or(x,T()) = T(), or(x,F()) = x, or(x853,or(x854,T())) = T(), or(x856,or(x857,F())) = or(x856,x857), or(or(T(),x868),x869) = T(), or(or(F(),x871),x872) = or(x871,x872) We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [not](x0) = x0 + 2, [or](x0, x1) = 2x0 + x1, [imply](x0, x1) = 2x0 + x1 + 4, [T] = 3, [F] = 1 orientation: not(T()) = 5 >= 1 = F() not(F()) = 3 >= 3 = T() or(x,T()) = 2x + 3 >= 3 = T() or(x,F()) = 2x + 1 >= x = x imply(x,y) = 2x + y + 4 >= 2x + y + 4 = or(not(x),y) or(T(),x) = x + 6 >= 3 = T() or(F(),x) = x + 2 >= x = x problem: not(F()) -> T() or(x,T()) -> T() imply(x,y) -> or(not(x),y) Matrix Interpretation Processor: dim=1 interpretation: [not](x0) = x0, [or](x0, x1) = 2x0 + x1, [imply](x0, x1) = 2x0 + x1, [T] = 0, [F] = 4 orientation: not(F()) = 4 >= 0 = T() or(x,T()) = 2x >= 0 = T() imply(x,y) = 2x + y >= 2x + y = or(not(x),y) problem: or(x,T()) -> T() imply(x,y) -> or(not(x),y) Matrix Interpretation Processor: dim=1 interpretation: [not](x0) = x0, [or](x0, x1) = 4x0 + 2x1 + 1, [imply](x0, x1) = 5x0 + 2x1 + 1, [T] = 2 orientation: or(x,T()) = 4x + 5 >= 2 = T() imply(x,y) = 5x + 2y + 1 >= 4x + 2y + 1 = or(not(x),y) problem: imply(x,y) -> or(not(x),y) Matrix Interpretation Processor: dim=1 interpretation: [not](x0) = x0, [or](x0, x1) = x0 + x1, [imply](x0, x1) = x0 + x1 + 1 orientation: imply(x,y) = x + y + 1 >= x + y = or(not(x),y) problem: Qed 1:and(x,T()) -> x and(x,F()) -> F() and(x,y) -> and(y,x) and(and(x,y),z) -> and(x,and(y,z)) AT confluence processor Complete TRS T' of input TRS: and(x,T()) -> x and(x,F()) -> F() and(T(),y) -> y and(F(),y) -> F() and(x,y) -> and(y,x) and(and(x,y),z) -> and(x,and(y,z)) T' = (P union S) with TRS P:and(x,y) -> and(y,x) and(and(x,y),z) -> and(x,and(y,z)) TRS S:and(x,T()) -> x and(x,F()) -> F() and(T(),y) -> y and(F(),y) -> F() S is left-linear and P is reversible. CP(S,S) = T() = T(), F() = F() CP(S,P union P^-1) = x = and(T(),x), and(x,y) = and(x,and(y,T())), and(x,z) = and(x,and(T(),z)), y = and(T(),y), and(x,y) = and(and(x,y),T()), F() = and(F(),x), F() = and(x,and(y,F())), and(F(),z) = and(x,and(F(),z)), F() = and(F(),y), and(x,F()) = and(and(x,y),F()), y = and(y,T()), and(y,z) = and(T(),and(y,z)), x = and(x,T()), and(y,z) = and(and(T(),y),z), and(x,z) = and(and(x,T()),z), F() = and(y,F()), and(F(),z) = and(F(),and(y,z)), F() = and(x,F()), F() = and(and(F(),y),z), and(x,F()) = and(and(x,F()),z) PCP_in(P union P^-1,S) = We have to check termination of S: Matrix Interpretation Processor: dim=1 interpretation: [and](x0, x1) = 5x0 + 5x1, [T] = 5, [F] = 0 orientation: and(x,T()) = 5x + 25 >= x = x and(x,F()) = 5x >= 0 = F() and(T(),y) = 5y + 25 >= y = y and(F(),y) = 5y >= 0 = F() problem: and(x,F()) -> F() and(F(),y) -> F() Matrix Interpretation Processor: dim=1 interpretation: [and](x0, x1) = 2x0 + 4x1, [F] = 2 orientation: and(x,F()) = 2x + 8 >= 2 = F() and(F(),y) = 4y + 4 >= 2 = F() problem: Qed