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_assoc {A} {JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}{CrA: Cross_alg A}{AG: ageable A}{XA: Age_alg A}:
Trip_alg A ->
forall P Q R: pred A,
(forall w1 w2 w3, join w1 w2 w3 -> P w3 -> P w1) ->
(forall w w', comparable w w' -> P w -> R w' -> joins w w') ->
(ewand TT P) && (ewand TT R) |-- emp ->
(ewand P (Q * R) = (ewand P Q * R))%pred.