sts.v 13 KB
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From prelude Require Export sets.
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From algebra Require Export cmra.
From algebra Require Import dra.
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Local Arguments valid _ _ !_ /.
Local Arguments op _ _ !_ !_ /.
Local Arguments unit _ _ !_ /.

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Module sts.
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Record stsT := STS {
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  state : Type;
  token : Type;
  trans : relation state;
  tok   : state  set token;
}.

(* The type of bounds we can give to the state of an STS. This is the type
   that we equip with an RA structure. *)
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Inductive bound (sts : stsT) :=
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  | bound_auth : state sts  set (token sts)  bound sts
  | bound_frag : set (state sts)  set (token sts ) bound sts.
Arguments bound_auth {_} _ _.
Arguments bound_frag {_} _ _.

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Section sts_core.
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Context (sts : stsT).
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Infix "≼" := dra_included.
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Notation state := (state sts).
Notation token := (token sts).
Notation trans := (trans sts).
Notation tok := (tok sts).

Inductive equiv : Equiv (bound sts) :=
  | auth_equiv s T1 T2 : T1  T2  bound_auth s T1  bound_auth s T2
  | frag_equiv S1 S2 T1 T2 : T1  T2  S1  S2 
                             bound_frag S1 T1  bound_frag S2 T2.
Global Existing Instance equiv.
Inductive step : relation (state * set token) :=
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  | Step s1 s2 T1 T2 :
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     trans s1 s2  tok s1  T1    tok s2  T2   
     tok s1  T1  tok s2  T2  step (s1,T1) (s2,T2).
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Hint Resolve Step.
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Inductive frame_step (T : set token) (s1 s2 : state) : Prop :=
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  | Frame_step T1 T2 :
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     T1  (tok s1  T)    step (s1,T1) (s2,T2)  frame_step T s1 s2.
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Hint Resolve Frame_step.
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Record closed (S : set state) (T : set token) : Prop := Closed {
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  closed_ne : S  ;
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  closed_disjoint s : s  S  tok s  T  ;
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  closed_step s1 s2 : s1  S  frame_step T s1 s2  s2  S
}.
Lemma closed_steps S T s1 s2 :
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  closed S T  s1  S  rtc (frame_step T) s1 s2  s2  S.
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Proof. induction 3; eauto using closed_step. Qed.
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Global Instance valid : Valid (bound sts) := λ x,
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  match x with
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  | bound_auth s T => tok s  T   | bound_frag S' T => closed S' T
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  end.
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Definition up (s : state) (T : set token) : set state :=
  mkSet (rtc (frame_step T) s).
Definition up_set (S : set state) (T : set token) : set state
  := S = λ s, up s T.
Global Instance unit : Unit (bound sts) := λ x,
  match x with
  | bound_frag S' _ => bound_frag (up_set S'  ) 
  | bound_auth s _  => bound_frag (up s ) 
  end.
Inductive disjoint : Disjoint (bound sts) :=
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  | frag_frag_disjoint S1 S2 T1 T2 :
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     S1  S2    T1  T2    bound_frag S1 T1  bound_frag S2 T2
  | auth_frag_disjoint s S T1 T2 : s  S  T1  T2   
                                   bound_auth s T1  bound_frag S T2
  | frag_auth_disjoint s S T1 T2 : s  S  T1  T2   
                                   bound_frag S T1  bound_auth s T2.
Global Existing Instance disjoint.
Global Instance op : Op (bound sts) := λ x1 x2,
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  match x1, x2 with
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  | bound_frag S1 T1, bound_frag S2 T2 => bound_frag (S1  S2) (T1  T2)
  | bound_auth s T1, bound_frag _ T2 => bound_auth s (T1  T2)
  | bound_frag _ T1, bound_auth s T2 => bound_auth s (T1  T2)
  | bound_auth s T1, bound_auth _ T2 =>
    bound_auth s (T1  T2)(* never happens *)
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  end.
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Global Instance minus : Minus (bound sts) := λ x1 x2,
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  match x1, x2 with
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  | bound_frag S1 T1, bound_frag S2 T2 => bound_frag
                                            (up_set S1 (T1  T2)) (T1  T2)
  | bound_auth s T1, bound_frag _ T2 => bound_auth s (T1  T2)
  | bound_frag _ T2, bound_auth s T1 =>
    bound_auth s (T1  T2) (* never happens *)
  | bound_auth s T1, bound_auth _ T2 => bound_frag (up s (T1  T2)) (T1  T2)
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  end.

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Hint Extern 10 (base.equiv (A:=set _) _ _) => solve_elem_of : sts.
Hint Extern 10 (¬(base.equiv (A:=set _) _ _)) => solve_elem_of : sts.
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Hint Extern 10 (_  _) => solve_elem_of : sts.
Hint Extern 10 (_  _) => solve_elem_of : sts.
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Instance: Equivalence (() : relation (bound sts)).
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Proof.
  split.
  * by intros []; constructor.
  * by destruct 1; constructor.
  * destruct 1; inversion_clear 1; constructor; etransitivity; eauto.
Qed.
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Instance framestep_proper : Proper (() ==> (=) ==> (=) ==> impl) frame_step.
Proof. intros ?? HT ?? <- ?? <-; destruct 1; econstructor; eauto with sts. Qed.
Instance closed_proper' : Proper (() ==> () ==> impl) closed.
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Proof.
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  intros ?? HT ?? HS; destruct 1;
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    constructor; intros until 0; rewrite -?HS -?HT; eauto.
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Qed.
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Instance closed_proper : Proper (() ==> () ==> iff) closed.
Proof. by split; apply closed_proper'. Qed.
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Lemma closed_op T1 T2 S1 S2 :
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  closed S1 T1  closed S2 T2 
  T1  T2    S1  S2    closed (S1  S2) (T1  T2).
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Proof.
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  intros [_ ? Hstep1] [_ ? Hstep2] ?; split; [done|solve_elem_of|].
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  intros s3 s4; rewrite !elem_of_intersection; intros [??] [T3 T4 ?]; split.
  * apply Hstep1 with s3, Frame_step with T3 T4; auto with sts.
  * apply Hstep2 with s3, Frame_step with T3 T4; auto with sts.
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Qed.
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Instance up_preserving : Proper ((=) ==> flip () ==> ()) up.
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Proof.
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  intros s ? <- T T' HT ; apply elem_of_subseteq.
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  induction 1 as [|s1 s2 s3 [T1 T2]]; [constructor|].
  eapply rtc_l; [eapply Frame_step with T1 T2|]; eauto with sts.
Qed.
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Instance up_proper : Proper ((=) ==> () ==> ()) up.
Proof. by intros ??? ?? [??]; split; apply up_preserving. Qed.
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Instance up_set_preserving : Proper (() ==> flip () ==> ()) up_set.
Proof.
  intros S1 S2 HS T1 T2 HT. rewrite /up_set.
  f_equiv; last done. move =>s1 s2 Hs. simpl in HT. by apply up_preserving.
Qed.
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Instance up_set_proper : Proper (() ==> () ==> ()) up_set.
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Proof.
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    by intros ?? EQ1 ?? EQ2; split; apply up_set_preserving; rewrite ?EQ1 ?EQ2.
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Qed.
Lemma elem_of_up s T : s  up s T.
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Proof. constructor. Qed.
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Lemma subseteq_up_set S T : S  up_set S T.
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Proof. intros s ?; apply elem_of_bind; eauto using elem_of_up. Qed.
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Lemma up_up_set s T : up s T  up_set {[ s ]} T.
Proof. by rewrite /up_set collection_bind_singleton. Qed.
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Lemma closed_up_set S T :
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  ( s, s  S  tok s  T  )  S    closed (up_set S T) T.
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Proof.
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  intros HS Hne; unfold up_set; split.
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  * assert ( s, s  up s T) by eauto using elem_of_up. solve_elem_of.
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  * intros s; rewrite !elem_of_bind; intros (s'&Hstep&Hs').
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    specialize (HS s' Hs'); clear Hs' Hne S.
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    induction Hstep as [s|s1 s2 s3 [T1 T2 ? Hstep] ? IH]; auto.
    inversion_clear Hstep; apply IH; clear IH; auto with sts.
  * intros s1 s2; rewrite !elem_of_bind; intros (s&?&?) ?; exists s.
    split; [eapply rtc_r|]; eauto.
Qed.
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Lemma closed_up_set_empty S : S    closed (up_set S ) .
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Proof. eauto using closed_up_set with sts. Qed.
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Lemma closed_up s T : tok s  T    closed (up s T) T.
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Proof.
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  intros; rewrite -(collection_bind_singleton (λ s, up s T) s).
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  apply closed_up_set; solve_elem_of.
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Qed.
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Lemma closed_up_empty s : closed (up s ) .
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Proof. eauto using closed_up with sts. Qed.
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Lemma up_closed S T : closed S T  up_set S T  S.
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Proof.
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  intros; split; auto using subseteq_up_set; intros s.
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  unfold up_set; rewrite elem_of_bind; intros (s'&Hstep&?).
  induction Hstep; eauto using closed_step.
Qed.
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Global Instance dra : DRA (bound sts).
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Proof.
  split.
  * apply _.
  * by do 2 destruct 1; constructor; setoid_subst.
  * by destruct 1; constructor; setoid_subst.
  * by intros ? [|]; destruct 1; inversion_clear 1; constructor; setoid_subst.
  * by do 2 destruct 1; constructor; setoid_subst.
  * assert ( T T' S s,
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      closed S T  s  S  tok s  T'    tok s  (T  T')  ).
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    { intros S T T' s [??]; solve_elem_of. }
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    destruct 3; simpl in *; auto using closed_op with sts.
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  * intros []; simpl; eauto using closed_up, closed_up_set, closed_ne with sts.
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  * intros ???? (z&Hy&?&Hxz); destruct Hxz; inversion Hy;clear Hy; setoid_subst;
      rewrite ?disjoint_union_difference; auto using closed_up with sts.
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    eapply closed_up_set; eauto 2 using closed_disjoint with sts.
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  * intros [] [] []; constructor; rewrite ?assoc; auto with sts.
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  * destruct 4; inversion_clear 1; constructor; auto with sts.
  * destruct 4; inversion_clear 1; constructor; auto with sts.
  * destruct 1; constructor; auto with sts.
  * destruct 3; constructor; auto with sts.
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  * intros [|S T]; constructor; auto using elem_of_up with sts.
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    assert (S  up_set S   S  ) by eauto using subseteq_up_set, closed_ne.
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    solve_elem_of.
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  * intros [|S T]; constructor; auto with sts.
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    assert (S  up_set S ); auto using subseteq_up_set with sts.
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  * intros [s T|S T]; constructor; auto with sts.
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    + rewrite (up_closed (up _ _)); auto using closed_up with sts.
    + rewrite (up_closed (up_set _ _));
        eauto using closed_up_set, closed_ne with sts.
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  * intros x y ?? (z&Hy&?&Hxz); exists (unit (x  y)); split_ands.
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    + destruct Hxz;inversion_clear Hy;constructor;unfold up_set; solve_elem_of.
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    + destruct Hxz; inversion_clear Hy; simpl;
        auto using closed_up_set_empty, closed_up_empty with sts.
    + destruct Hxz; inversion_clear Hy; constructor;
        repeat match goal with
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        | |- context [ up_set ?S ?T ] =>
           unless (S  up_set S T) by done; pose proof (subseteq_up_set S T)
        | |- context [ up ?s ?T ] =>
           unless (s  up s T) by done; pose proof (elem_of_up s T)
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        end; auto with sts.
  * intros x y ?? (z&Hy&_&Hxz); destruct Hxz; inversion_clear Hy; constructor;
      repeat match goal with
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      | |- context [ up_set ?S ?T ] =>
         unless (S  up_set S T) by done; pose proof (subseteq_up_set S T)
      | |- context [ up ?s ?T ] =>
           unless (s  up s T) by done; pose proof (elem_of_up s T)
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      end; auto with sts.
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  * intros x y ?? (z&Hy&?&Hxz); destruct Hxz as [S1 S2 T1 T2| |];
      inversion Hy; clear Hy; constructor; setoid_subst;
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      rewrite ?disjoint_union_difference; auto.
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    split; [|apply intersection_greatest; auto using subseteq_up_set with sts].
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    apply intersection_greatest; [auto with sts|].
    intros s2; rewrite elem_of_intersection.
    unfold up_set; rewrite elem_of_bind; intros (?&s1&?&?&?).
    apply closed_steps with T2 s1; auto with sts.
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Qed.
Lemma step_closed s1 s2 T1 T2 S Tf :
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  step (s1,T1) (s2,T2)  closed S Tf  s1  S  T1  Tf   
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  s2  S  T2  Tf    tok s2  T2  .
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Proof.
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  inversion_clear 1 as [???? HR Hs1 Hs2]; intros [?? Hstep]??; split_ands; auto.
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  * eapply Hstep with s1, Frame_step with T1 T2; auto with sts.
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  * solve_elem_of -Hstep Hs1 Hs2.
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Qed.
End sts_core.

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Section stsRA.
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Context (sts : stsT).
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Canonical Structure RA := validityRA (bound sts).
Definition auth (s : state sts) (T : set (token sts)) : RA :=
  to_validity (bound_auth s T).
Definition frag (S : set (state sts)) (T : set (token sts)) : RA :=
  to_validity (bound_frag S T).
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Lemma update_auth s1 s2 T1 T2 :
  step sts (s1,T1) (s2,T2)  auth s1 T1 ~~> auth s2 T2.
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Proof.
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  intros ?; apply validity_update; inversion 3 as [|? S ? Tf|]; subst.
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  destruct (step_closed sts s1 s2 T1 T2 S Tf) as (?&?&?); auto.
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  repeat (done || constructor).
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Qed.
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Lemma sts_update_frag S1 S2 (T : set (token sts)) :
  S1  S2  closed sts S2 T 
  frag S1 T ~~> frag S2 T.
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Proof.
  move=>HS Hcl. eapply validity_update; inversion 3 as [|? S ? Tf|]; subst.
  - split; first done. constructor; last done. solve_elem_of.
  - split; first done. constructor; solve_elem_of.
Qed.

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Lemma frag_included S1 S2 T1 T2 :
  closed sts S2 T2 
  frag S1 T1  frag S2 T2  
  (closed sts S1 T1   Tf, T2  T1  Tf  T1  Tf   
                            S2  (S1  up_set sts S2 Tf)).
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Proof.
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  move=>Hcl2. split.
  - intros [xf EQ]. destruct xf as [xf vf Hvf]. destruct xf as [Sf Tf|Sf Tf].
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    { exfalso. inversion_clear EQ as [Hv EQ']. apply EQ' in Hcl2. simpl in Hcl2.
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      inversion Hcl2. }
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    inversion_clear EQ as [Hv EQ'].
    move:(EQ' Hcl2)=>{EQ'} EQ. inversion_clear EQ as [|? ? ? ? HT HS].
    destruct Hv as [Hv _]. move:(Hv Hcl2)=>{Hv} [/= Hcl1  [Hclf Hdisj]].
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    apply Hvf in Hclf. simpl in Hclf. clear Hvf.
    inversion_clear Hdisj. split; last (exists Tf; split_ands); [done..|].
    apply (anti_symm ()).
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    + move=>s HS2. apply elem_of_intersection. split; first by apply HS.
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      by apply sts.subseteq_up_set.
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    + move=>s /elem_of_intersection [HS1 Hscl]. apply HS. split; first done.
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      destruct Hscl as [s' [Hsup Hs']].
      eapply sts.closed_steps; last (hnf in Hsup; eexact Hsup); first done.
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      solve_elem_of +HS Hs'.
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  - intros (Hcl1 & Tf & Htk & Hf & Hs).
    exists (frag (up_set sts S2 Tf) Tf).
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    split; first split; simpl;[|done|].
    + intros _. split_ands; first done.
      * apply sts.closed_up_set; last by eapply sts.closed_ne.
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        move=>s Hs2. move:(closed_disjoint sts _ _ Hcl2 _ Hs2).
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        solve_elem_of +Htk.
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      * constructor; last done. rewrite -Hs. by eapply sts.closed_ne.
    + intros _. constructor; [ solve_elem_of +Htk | done].
Qed.

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Lemma frag_included' S1 S2 T :
  closed sts S2 T  closed sts S1 T 
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  S2  S1  sts.up_set sts S2  
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  frag S1 T  frag S2 T.
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Proof.
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  intros. apply frag_included; first done.
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  split; first done. exists . split_ands; done || solve_elem_of+.
Qed.
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End stsRA.
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End sts.