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(* 02110-1301 USA                                                     *)
Require Export DistributedReferenceCounting.machine4.invariant5.
Require Export DistributedReferenceCounting.machine4.invariant7.
Unset Standard Proposition Elimination Names.
(* changes: In safety1 and safety2, I had to use sigma_but_strictly_positive, instead of sigma_strictly_positive.  In safety2, the case ~s2=owner should not be isolated *)
Remark add_reduce : forall x : Z, (x > 0)%Z -> (x + 1 - 1 > 0)%Z.

Lemma safety2 :
forall c : Config,
legal c ->
forall s1 s2 : Site,
In_queue Message copy (bm c s1 s2) -> (st c owner > 0)%Z.