Definition precise {A} {JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}{AG: ageable A}{XA: Age_alg A} (P: pred A) : Prop :=
     forall w w1 w2, P w1 -> P w2 -> join_sub w1 w -> join_sub w2 w -> w1=w2.Definition precise2  {A} {JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}{AG: ageable A}{XA: Age_alg A} (P: pred A) : Prop :=
     forall Q R, (P * (Q && R) = (P * Q) && (P * R))%pred.

Lemma precise_emp {A} {JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}{AG: ageable A}{XA: Age_alg A}: precise emp.