Definition wk_split {A} {JA: Join A} :=
      forall a b c d e : A, join a b c -> join d e c -> joins a d -> join_sub d b.

Lemma ewand_sepcon {A} {JA: Join A}{PA: Perm_alg A}{AG: ageable A}{XA: Age_alg A}: forall P Q R, (ewand (P * Q) R = ewand P (ewand Q R))%pred.