Module Share : SHARE_MODEL := tree_shares.Share.
Definition share : Type := Share.t.
Instance pa_share : Perm_alg share := Share.pa.
Instance sa_share : Sep_alg share := Share.sa.
Instance ca_share : Canc_alg share := Share.ca.
Definition emptyshare : share := Share.bot.
Definition fullshare : share := Share.top.

Theorem leq_join_sub : forall s1 s2:Share.t,
s1 <= s2 <-> join_sub s1 s2.