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(* 02110-1301 USA                                                     *)
Require Export DistributedReferenceCounting.machine1.invariant6.
Unset Standard Proposition Elimination Names.

Lemma parent_invariant_inductive :
forall (c : Config) (t : class_trans c),
legal c ->
(legal c ->
forall s : Site,
indirect_son1 c s -> exists s1 : Site, direct_son c s1 /\ ancestor c s1 s) ->
legal (transition c t) ->
forall s : Site,
indirect_son1 (transition c t) s ->
exists s1 : Site,
direct_son (transition c t) s1 /\ ancestor (transition c t) s1 s.