Theory Project (Isabelle2005: October 2005)

# Theory Project

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theory Project
imports Extend
begin

    (*  Title:      HOL/UNITY/Project.ML
        ID:         $Id: Project.thy,v 1.13 2005/06/17 14:13:10 haftmann Exp $
        Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
        Copyright   1999  University of Cambridge

    Projections of state sets (also of actions and programs)

    Inheritance of GUARANTEES properties under extension
    *)

    header{*Projections of State Sets*}

    theory Project imports Extend begin

    constdefs
      projecting :: "['c program => 'c set, 'a*'b => 'c,
                      'a program, 'c program set, 'a program set] => bool"
        "projecting C h F X' X ==
           ∀G. extend h F\<squnion>G ∈ X' --> F\<squnion>project h (C G) G ∈ X"

      extending :: "['c program => 'c set, 'a*'b => 'c, 'a program,
                     'c program set, 'a program set] => bool"
        "extending C h F Y' Y ==
           ∀G. extend h F  ok G --> F\<squnion>project h (C G) G ∈ Y
                  --> extend h F\<squnion>G ∈ Y'"

      subset_closed :: "'a set set => bool"
        "subset_closed U == ∀A ∈ U. Pow A ⊆ U"

    lemma (in Extend) project_extend_constrains_I:
         "F ∈ A co B ==> project h C (extend h F) ∈ A co B"
    apply (auto simp add: extend_act_def project_act_def constrains_def)
    done

    subsection{*Safety*}

    (*used below to prove Join_project_ensures*)
    lemma (in Extend) project_unless [rule_format]:
         "[| G ∈ stable C;  project h C G ∈ A unless B |]
          ==> G ∈ (C ∩ extend_set h A) unless (extend_set h B)"
    apply (simp add: unless_def project_constrains)
    apply (blast dest: stable_constrains_Int intro: constrains_weaken)
    done

    (*Generalizes project_constrains to the program F\<squnion>project h C G
      useful with guarantees reasoning*)
    lemma (in Extend) Join_project_constrains:
         "(F\<squnion>project h C G ∈ A co B)  =
            (extend h F\<squnion>G ∈ (C ∩ extend_set h A) co (extend_set h B) &
             F ∈ A co B)"
    apply (simp (no_asm) add: project_constrains)
    apply (blast intro: extend_constrains [THEN iffD2, THEN constrains_weaken]
                 dest: constrains_imp_subset)
    done

    (*The condition is required to prove the left-to-right direction
      could weaken it to G ∈ (C ∩ extend_set h A) co C*)
    lemma (in Extend) Join_project_stable:
         "extend h F\<squnion>G ∈ stable C
          ==> (F\<squnion>project h C G ∈ stable A)  =
              (extend h F\<squnion>G ∈ stable (C ∩ extend_set h A) &
               F ∈ stable A)"
    apply (unfold stable_def)
    apply (simp only: Join_project_constrains)
    apply (blast intro: constrains_weaken dest: constrains_Int)
    done

    (*For using project_guarantees in particular cases*)
    lemma (in Extend) project_constrains_I:
         "extend h F\<squnion>G ∈ extend_set h A co extend_set h B
          ==> F\<squnion>project h C G ∈ A co B"
    apply (simp add: project_constrains extend_constrains)
    apply (blast intro: constrains_weaken dest: constrains_imp_subset)
    done

    lemma (in Extend) project_increasing_I:
         "extend h F\<squnion>G ∈ increasing (func o f)
          ==> F\<squnion>project h C G ∈ increasing func"
    apply (unfold increasing_def stable_def)
    apply (simp del: Join_constrains
                add: project_constrains_I extend_set_eq_Collect)
    done

    lemma (in Extend) Join_project_increasing:
         "(F\<squnion>project h UNIV G ∈ increasing func)  =
          (extend h F\<squnion>G ∈ increasing (func o f))"
    apply (rule iffI)
    apply (erule_tac [2] project_increasing_I)
    apply (simp del: Join_stable
                add: increasing_def Join_project_stable)
    apply (auto simp add: extend_set_eq_Collect extend_stable [THEN iffD1])
    done

    (*The UNIV argument is essential*)
    lemma (in Extend) project_constrains_D:
         "F\<squnion>project h UNIV G ∈ A co B
          ==> extend h F\<squnion>G ∈ extend_set h A co extend_set h B"
    by (simp add: project_constrains extend_constrains)

    subsection{*"projecting" and union/intersection (no converses)*}

    lemma projecting_Int:
         "[| projecting C h F XA' XA;  projecting C h F XB' XB |]
          ==> projecting C h F (XA' ∩ XB') (XA ∩ XB)"
    by (unfold projecting_def, blast)

    lemma projecting_Un:
         "[| projecting C h F XA' XA;  projecting C h F XB' XB |]
          ==> projecting C h F (XA' ∪ XB') (XA ∪ XB)"
    by (unfold projecting_def, blast)

    lemma projecting_INT:
         "[| !!i. i ∈ I ==> projecting C h F (X' i) (X i) |]
          ==> projecting C h F (\<Inter>i ∈ I. X' i) (\<Inter>i ∈ I. X i)"
    by (unfold projecting_def, blast)

    lemma projecting_UN:
         "[| !!i. i ∈ I ==> projecting C h F (X' i) (X i) |]
          ==> projecting C h F (\<Union>i ∈ I. X' i) (\<Union>i ∈ I. X i)"
    by (unfold projecting_def, blast)

    lemma projecting_weaken:
         "[| projecting C h F X' X;  U'<=X';  X ⊆ U |] ==> projecting C h F U' U"
    by (unfold projecting_def, auto)

    lemma projecting_weaken_L:
         "[| projecting C h F X' X;  U'<=X' |] ==> projecting C h F U' X"
    by (unfold projecting_def, auto)

    lemma extending_Int:
         "[| extending C h F YA' YA;  extending C h F YB' YB |]
          ==> extending C h F (YA' ∩ YB') (YA ∩ YB)"
    by (unfold extending_def, blast)

    lemma extending_Un:
         "[| extending C h F YA' YA;  extending C h F YB' YB |]
          ==> extending C h F (YA' ∪ YB') (YA ∪ YB)"
    by (unfold extending_def, blast)

    lemma extending_INT:
         "[| !!i. i ∈ I ==> extending C h F (Y' i) (Y i) |]
          ==> extending C h F (\<Inter>i ∈ I. Y' i) (\<Inter>i ∈ I. Y i)"
    by (unfold extending_def, blast)

    lemma extending_UN:
         "[| !!i. i ∈ I ==> extending C h F (Y' i) (Y i) |]
          ==> extending C h F (\<Union>i ∈ I. Y' i) (\<Union>i ∈ I. Y i)"
    by (unfold extending_def, blast)

    lemma extending_weaken:
         "[| extending C h F Y' Y;  Y'<=V';  V ⊆ Y |] ==> extending C h F V' V"
    by (unfold extending_def, auto)

    lemma extending_weaken_L:
         "[| extending C h F Y' Y;  Y'<=V' |] ==> extending C h F V' Y"
    by (unfold extending_def, auto)

    lemma projecting_UNIV: "projecting C h F X' UNIV"
    by (simp add: projecting_def)

    lemma (in Extend) projecting_constrains:
         "projecting C h F (extend_set h A co extend_set h B) (A co B)"
    apply (unfold projecting_def)
    apply (blast intro: project_constrains_I)
    done

    lemma (in Extend) projecting_stable:
         "projecting C h F (stable (extend_set h A)) (stable A)"
    apply (unfold stable_def)
    apply (rule projecting_constrains)
    done

    lemma (in Extend) projecting_increasing:
         "projecting C h F (increasing (func o f)) (increasing func)"
    apply (unfold projecting_def)
    apply (blast intro: project_increasing_I)
    done

    lemma (in Extend) extending_UNIV: "extending C h F UNIV Y"
    apply (simp (no_asm) add: extending_def)
    done

    lemma (in Extend) extending_constrains:
         "extending (%G. UNIV) h F (extend_set h A co extend_set h B) (A co B)"
    apply (unfold extending_def)
    apply (blast intro: project_constrains_D)
    done

    lemma (in Extend) extending_stable:
         "extending (%G. UNIV) h F (stable (extend_set h A)) (stable A)"
    apply (unfold stable_def)
    apply (rule extending_constrains)
    done

    lemma (in Extend) extending_increasing:
         "extending (%G. UNIV) h F (increasing (func o f)) (increasing func)"
    by (force simp only: extending_def Join_project_increasing)

    subsection{*Reachability and project*}

    (*In practice, C = reachable(...): the inclusion is equality*)
    lemma (in Extend) reachable_imp_reachable_project:
         "[| reachable (extend h F\<squnion>G) ⊆ C;
             z ∈ reachable (extend h F\<squnion>G) |]
          ==> f z ∈ reachable (F\<squnion>project h C G)"
    apply (erule reachable.induct)
    apply (force intro!: reachable.Init simp add: split_extended_all, auto)
     apply (rule_tac act = x in reachable.Acts)
     apply auto
     apply (erule extend_act_D)
    apply (rule_tac act1 = "Restrict C act"
           in project_act_I [THEN [3] reachable.Acts], auto)
    done

    lemma (in Extend) project_Constrains_D:
         "F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ A Co B
          ==> extend h F\<squnion>G ∈ (extend_set h A) Co (extend_set h B)"
    apply (unfold Constrains_def)
    apply (simp del: Join_constrains
                add: Join_project_constrains, clarify)
    apply (erule constrains_weaken)
    apply (auto intro: reachable_imp_reachable_project)
    done

    lemma (in Extend) project_Stable_D:
         "F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Stable A
          ==> extend h F\<squnion>G ∈ Stable (extend_set h A)"
    apply (unfold Stable_def)
    apply (simp (no_asm_simp) add: project_Constrains_D)
    done

    lemma (in Extend) project_Always_D:
         "F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Always A
          ==> extend h F\<squnion>G ∈ Always (extend_set h A)"
    apply (unfold Always_def)
    apply (force intro: reachable.Init simp add: project_Stable_D split_extended_all)
    done

    lemma (in Extend) project_Increasing_D:
         "F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Increasing func
          ==> extend h F\<squnion>G ∈ Increasing (func o f)"
    apply (unfold Increasing_def, auto)
    apply (subst extend_set_eq_Collect [symmetric])
    apply (simp (no_asm_simp) add: project_Stable_D)
    done

    subsection{*Converse results for weak safety: benefits of the argument C *}

    (*In practice, C = reachable(...): the inclusion is equality*)
    lemma (in Extend) reachable_project_imp_reachable:
         "[| C ⊆ reachable(extend h F\<squnion>G);
             x ∈ reachable (F\<squnion>project h C G) |]
          ==> ∃y. h(x,y) ∈ reachable (extend h F\<squnion>G)"
    apply (erule reachable.induct)
    apply  (force intro: reachable.Init)
    apply (auto simp add: project_act_def)
    apply (force del: Id_in_Acts intro: reachable.Acts extend_act_D)+
    done

    lemma (in Extend) project_set_reachable_extend_eq:
         "project_set h (reachable (extend h F\<squnion>G)) =
          reachable (F\<squnion>project h (reachable (extend h F\<squnion>G)) G)"
    by (auto dest: subset_refl [THEN reachable_imp_reachable_project]
                   subset_refl [THEN reachable_project_imp_reachable])

    (*UNUSED*)
    lemma (in Extend) reachable_extend_Join_subset:
         "reachable (extend h F\<squnion>G) ⊆ C
          ==> reachable (extend h F\<squnion>G) ⊆
              extend_set h (reachable (F\<squnion>project h C G))"
    apply (auto dest: reachable_imp_reachable_project)
    done

    lemma (in Extend) project_Constrains_I:
         "extend h F\<squnion>G ∈ (extend_set h A) Co (extend_set h B)
          ==> F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ A Co B"
    apply (unfold Constrains_def)
    apply (simp del: Join_constrains
                add: Join_project_constrains extend_set_Int_distrib)
    apply (rule conjI)
     prefer 2
     apply (force elim: constrains_weaken_L
                  dest!: extend_constrains_project_set
                         subset_refl [THEN reachable_project_imp_reachable])
    apply (blast intro: constrains_weaken_L)
    done

    lemma (in Extend) project_Stable_I:
         "extend h F\<squnion>G ∈ Stable (extend_set h A)
          ==> F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Stable A"
    apply (unfold Stable_def)
    apply (simp (no_asm_simp) add: project_Constrains_I)
    done

    lemma (in Extend) project_Always_I:
         "extend h F\<squnion>G ∈ Always (extend_set h A)
          ==> F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Always A"
    apply (unfold Always_def)
    apply (auto simp add: project_Stable_I)
    apply (unfold extend_set_def, blast)
    done

    lemma (in Extend) project_Increasing_I:
        "extend h F\<squnion>G ∈ Increasing (func o f)
         ==> F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Increasing func"
    apply (unfold Increasing_def, auto)
    apply (simp (no_asm_simp) add: extend_set_eq_Collect project_Stable_I)
    done

    lemma (in Extend) project_Constrains:
         "(F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ A Co B)  =
          (extend h F\<squnion>G ∈ (extend_set h A) Co (extend_set h B))"
    apply (blast intro: project_Constrains_I project_Constrains_D)
    done

    lemma (in Extend) project_Stable:
         "(F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Stable A)  =
          (extend h F\<squnion>G ∈ Stable (extend_set h A))"
    apply (unfold Stable_def)
    apply (rule project_Constrains)
    done

    lemma (in Extend) project_Increasing:
       "(F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ Increasing func)  =
        (extend h F\<squnion>G ∈ Increasing (func o f))"
    apply (simp (no_asm_simp) add: Increasing_def project_Stable extend_set_eq_Collect)
    done

    subsection{*A lot of redundant theorems: all are proved to facilitate reasoning
        about guarantees.*}

    lemma (in Extend) projecting_Constrains:
         "projecting (%G. reachable (extend h F\<squnion>G)) h F
                     (extend_set h A Co extend_set h B) (A Co B)"

    apply (unfold projecting_def)
    apply (blast intro: project_Constrains_I)
    done

    lemma (in Extend) projecting_Stable:
         "projecting (%G. reachable (extend h F\<squnion>G)) h F
                     (Stable (extend_set h A)) (Stable A)"
    apply (unfold Stable_def)
    apply (rule projecting_Constrains)
    done

    lemma (in Extend) projecting_Always:
         "projecting (%G. reachable (extend h F\<squnion>G)) h F
                     (Always (extend_set h A)) (Always A)"
    apply (unfold projecting_def)
    apply (blast intro: project_Always_I)
    done

    lemma (in Extend) projecting_Increasing:
         "projecting (%G. reachable (extend h F\<squnion>G)) h F
                     (Increasing (func o f)) (Increasing func)"
    apply (unfold projecting_def)
    apply (blast intro: project_Increasing_I)
    done

    lemma (in Extend) extending_Constrains:
         "extending (%G. reachable (extend h F\<squnion>G)) h F
                      (extend_set h A Co extend_set h B) (A Co B)"
    apply (unfold extending_def)
    apply (blast intro: project_Constrains_D)
    done

    lemma (in Extend) extending_Stable:
         "extending (%G. reachable (extend h F\<squnion>G)) h F
                      (Stable (extend_set h A)) (Stable A)"
    apply (unfold extending_def)
    apply (blast intro: project_Stable_D)
    done

    lemma (in Extend) extending_Always:
         "extending (%G. reachable (extend h F\<squnion>G)) h F
                      (Always (extend_set h A)) (Always A)"
    apply (unfold extending_def)
    apply (blast intro: project_Always_D)
    done

    lemma (in Extend) extending_Increasing:
         "extending (%G. reachable (extend h F\<squnion>G)) h F
                      (Increasing (func o f)) (Increasing func)"
    apply (unfold extending_def)
    apply (blast intro: project_Increasing_D)
    done

    subsection{*leadsETo in the precondition (??)*}

    subsubsection{*transient*}

    lemma (in Extend) transient_extend_set_imp_project_transient:
         "[| G ∈ transient (C ∩ extend_set h A);  G ∈ stable C |]
          ==> project h C G ∈ transient (project_set h C ∩ A)"
    apply (auto simp add: transient_def Domain_project_act)
    apply (subgoal_tac "act `` (C ∩ extend_set h A) ⊆ - extend_set h A")
     prefer 2
     apply (simp add: stable_def constrains_def, blast)
    (*back to main goal*)
    apply (erule_tac V = "?AA ⊆ -C ∪ ?BB" in thin_rl)
    apply (drule bspec, assumption)
    apply (simp add: extend_set_def project_act_def, blast)
    done

    (*converse might hold too?*)
    lemma (in Extend) project_extend_transient_D:
         "project h C (extend h F) ∈ transient (project_set h C ∩ D)
          ==> F ∈ transient (project_set h C ∩ D)"
    apply (simp add: transient_def Domain_project_act, safe)
    apply blast+
    done

    subsubsection{*ensures -- a primitive combining progress with safety*}

    (*Used to prove project_leadsETo_I*)
    lemma (in Extend) ensures_extend_set_imp_project_ensures:
         "[| extend h F ∈ stable C;  G ∈ stable C;
             extend h F\<squnion>G ∈ A ensures B;  A-B = C ∩ extend_set h D |]
          ==> F\<squnion>project h C G
                ∈ (project_set h C ∩ project_set h A) ensures (project_set h B)"
    apply (simp add: ensures_def project_constrains Join_transient extend_transient,
           clarify)
    apply (intro conjI)
    (*first subgoal*)
    apply (blast intro: extend_stable_project_set
                      [THEN stableD, THEN constrains_Int, THEN constrains_weaken]
                 dest!: extend_constrains_project_set equalityD1)
    (*2nd subgoal*)
    apply (erule stableD [THEN constrains_Int, THEN constrains_weaken])
        apply assumption
       apply (simp (no_asm_use) add: extend_set_def)
       apply blast
     apply (simp add: extend_set_Int_distrib extend_set_Un_distrib)
     apply (blast intro!: extend_set_project_set [THEN subsetD], blast)
    (*The transient part*)
    apply auto
     prefer 2
     apply (force dest!: equalityD1
                  intro: transient_extend_set_imp_project_transient
                             [THEN transient_strengthen])
    apply (simp (no_asm_use) add: Int_Diff)
    apply (force dest!: equalityD1
                 intro: transient_extend_set_imp_project_transient
                   [THEN project_extend_transient_D, THEN transient_strengthen])
    done

    text{*Transferring a transient property upwards*}
    lemma (in Extend) project_transient_extend_set:
         "project h C G ∈ transient (project_set h C ∩ A - B)
          ==> G ∈ transient (C ∩ extend_set h A - extend_set h B)"
    apply (simp add: transient_def project_set_def extend_set_def project_act_def)
    apply (elim disjE bexE)
     apply (rule_tac x=Id in bexI)
      apply (blast intro!: rev_bexI )+
    done

    lemma (in Extend) project_unless2 [rule_format]:
         "[| G ∈ stable C;  project h C G ∈ (project_set h C ∩ A) unless B |]
          ==> G ∈ (C ∩ extend_set h A) unless (extend_set h B)"
    by (auto dest: stable_constrains_Int intro: constrains_weaken
             simp add: unless_def project_constrains Diff_eq Int_assoc
                       Int_extend_set_lemma)

    lemma (in Extend) extend_unless:
       "[|extend h F ∈ stable C; F ∈ A unless B|]
        ==> extend h F ∈ C ∩ extend_set h A unless extend_set h B"
    apply (simp add: unless_def stable_def)
    apply (drule constrains_Int)
    apply (erule extend_constrains [THEN iffD2])
    apply (erule constrains_weaken, blast)
    apply blast
    done

    (*Used to prove project_leadsETo_D*)
    lemma (in Extend) Join_project_ensures [rule_format]:
         "[| extend h F\<squnion>G ∈ stable C;
             F\<squnion>project h C G ∈ A ensures B |]
          ==> extend h F\<squnion>G ∈ (C ∩ extend_set h A) ensures (extend_set h B)"
    apply (auto simp add: ensures_eq extend_unless project_unless)
    apply (blast intro:  extend_transient [THEN iffD2] transient_strengthen)
    apply (blast intro: project_transient_extend_set transient_strengthen)
    done

    text{*Lemma useful for both STRONG and WEAK progress, but the transient
        condition's very strong*}

    (*The strange induction formula allows induction over the leadsTo
      assumption's non-atomic precondition*)
    lemma (in Extend) PLD_lemma:
         "[| extend h F\<squnion>G ∈ stable C;
             F\<squnion>project h C G ∈ (project_set h C ∩ A) leadsTo B |]
          ==> extend h F\<squnion>G ∈
              C ∩ extend_set h (project_set h C ∩ A) leadsTo (extend_set h B)"
    apply (erule leadsTo_induct)
      apply (blast intro: leadsTo_Basis Join_project_ensures)
     apply (blast intro: psp_stable2 [THEN leadsTo_weaken_L] leadsTo_Trans)
    apply (simp del: UN_simps add: Int_UN_distrib leadsTo_UN extend_set_Union)
    done

    lemma (in Extend) project_leadsTo_D_lemma:
         "[| extend h F\<squnion>G ∈ stable C;
             F\<squnion>project h C G ∈ (project_set h C ∩ A) leadsTo B |]
          ==> extend h F\<squnion>G ∈ (C ∩ extend_set h A) leadsTo (extend_set h B)"
    apply (rule PLD_lemma [THEN leadsTo_weaken])
    apply (auto simp add: split_extended_all)
    done

    lemma (in Extend) Join_project_LeadsTo:
         "[| C = (reachable (extend h F\<squnion>G));
             F\<squnion>project h C G ∈ A LeadsTo B |]
          ==> extend h F\<squnion>G ∈ (extend_set h A) LeadsTo (extend_set h B)"
    by (simp del: Join_stable    add: LeadsTo_def project_leadsTo_D_lemma
                                      project_set_reachable_extend_eq)

    subsection{*Towards the theorem @{text project_Ensures_D}*}

    lemma (in Extend) project_ensures_D_lemma:
         "[| G ∈ stable ((C ∩ extend_set h A) - (extend_set h B));
             F\<squnion>project h C G ∈ (project_set h C ∩ A) ensures B;
             extend h F\<squnion>G ∈ stable C |]
          ==> extend h F\<squnion>G ∈ (C ∩ extend_set h A) ensures (extend_set h B)"
    (*unless*)
    apply (auto intro!: project_unless2 [unfolded unless_def]
                intro: project_extend_constrains_I
                simp add: ensures_def)
    (*transient*)
    (*A G-action cannot occur*)
     prefer 2
     apply (blast intro: project_transient_extend_set)
    (*An F-action*)
    apply (force elim!: extend_transient [THEN iffD2, THEN transient_strengthen]
                 simp add: split_extended_all)
    done

    lemma (in Extend) project_ensures_D:
         "[| F\<squnion>project h UNIV G ∈ A ensures B;
             G ∈ stable (extend_set h A - extend_set h B) |]
          ==> extend h F\<squnion>G ∈ (extend_set h A) ensures (extend_set h B)"
    apply (rule project_ensures_D_lemma [of _ UNIV, THEN revcut_rl], auto)
    done

    lemma (in Extend) project_Ensures_D:
         "[| F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ A Ensures B;
             G ∈ stable (reachable (extend h F\<squnion>G) ∩ extend_set h A -
                         extend_set h B) |]
          ==> extend h F\<squnion>G ∈ (extend_set h A) Ensures (extend_set h B)"
    apply (unfold Ensures_def)
    apply (rule project_ensures_D_lemma [THEN revcut_rl])
    apply (auto simp add: project_set_reachable_extend_eq [symmetric])
    done

    subsection{*Guarantees*}

    lemma (in Extend) project_act_Restrict_subset_project_act:
         "project_act h (Restrict C act) ⊆ project_act h act"
    apply (auto simp add: project_act_def)
    done

    lemma (in Extend) subset_closed_ok_extend_imp_ok_project:
         "[| extend h F ok G; subset_closed (AllowedActs F) |]
          ==> F ok project h C G"
    apply (auto simp add: ok_def)
    apply (rename_tac act)
    apply (drule subsetD, blast)
    apply (rule_tac x = "Restrict C  (extend_act h act)" in rev_image_eqI)
    apply simp +
    apply (cut_tac project_act_Restrict_subset_project_act)
    apply (auto simp add: subset_closed_def)
    done

    (*Weak precondition and postcondition
      Not clear that it has a converse [or that we want one!]*)

    (*The raw version; 3rd premise could be weakened by adding the
      precondition extend h F\<squnion>G ∈ X' *)
    lemma (in Extend) project_guarantees_raw:
     assumes xguary:  "F ∈ X guarantees Y"
         and closed:  "subset_closed (AllowedActs F)"
         and project: "!!G. extend h F\<squnion>G ∈ X'
                            ==> F\<squnion>project h (C G) G ∈ X"
         and extend:  "!!G. [| F\<squnion>project h (C G) G ∈ Y |]
                            ==> extend h F\<squnion>G ∈ Y'"
     shows "extend h F ∈ X' guarantees Y'"
    apply (rule xguary [THEN guaranteesD, THEN extend, THEN guaranteesI])
    apply (blast intro: closed subset_closed_ok_extend_imp_ok_project)
    apply (erule project)
    done

    lemma (in Extend) project_guarantees:
         "[| F ∈ X guarantees Y;  subset_closed (AllowedActs F);
             projecting C h F X' X;  extending C h F Y' Y |]
          ==> extend h F ∈ X' guarantees Y'"
    apply (rule guaranteesI)
    apply (auto simp add: guaranteesD projecting_def extending_def
                          subset_closed_ok_extend_imp_ok_project)
    done

    (*It seems that neither "guarantees" law can be proved from the other.*)

    subsection{*guarantees corollaries*}

    subsubsection{*Some could be deleted: the required versions are easy to prove*}

    lemma (in Extend) extend_guar_increasing:
         "[| F ∈ UNIV guarantees increasing func;
             subset_closed (AllowedActs F) |]
          ==> extend h F ∈ X' guarantees increasing (func o f)"
    apply (erule project_guarantees)
    apply (rule_tac [3] extending_increasing)
    apply (rule_tac [2] projecting_UNIV, auto)
    done

    lemma (in Extend) extend_guar_Increasing:
         "[| F ∈ UNIV guarantees Increasing func;
             subset_closed (AllowedActs F) |]
          ==> extend h F ∈ X' guarantees Increasing (func o f)"
    apply (erule project_guarantees)
    apply (rule_tac [3] extending_Increasing)
    apply (rule_tac [2] projecting_UNIV, auto)
    done

    lemma (in Extend) extend_guar_Always:
         "[| F ∈ Always A guarantees Always B;
             subset_closed (AllowedActs F) |]
          ==> extend h F
                ∈ Always(extend_set h A) guarantees Always(extend_set h B)"
    apply (erule project_guarantees)
    apply (rule_tac [3] extending_Always)
    apply (rule_tac [2] projecting_Always, auto)
    done

    subsubsection{*Guarantees with a leadsTo postcondition*}

    lemma (in Extend) project_leadsTo_D:
         "F\<squnion>project h UNIV G ∈ A leadsTo B
          ==> extend h F\<squnion>G ∈ (extend_set h A) leadsTo (extend_set h B)"
    apply (rule_tac C1 = UNIV in project_leadsTo_D_lemma [THEN leadsTo_weaken], auto)
    done

    lemma (in Extend) project_LeadsTo_D:
         "F\<squnion>project h (reachable (extend h F\<squnion>G)) G ∈ A LeadsTo B
           ==> extend h F\<squnion>G ∈ (extend_set h A) LeadsTo (extend_set h B)"
    apply (rule refl [THEN Join_project_LeadsTo], auto)
    done

    lemma (in Extend) extending_leadsTo:
         "extending (%G. UNIV) h F
                    (extend_set h A leadsTo extend_set h B) (A leadsTo B)"
    apply (unfold extending_def)
    apply (blast intro: project_leadsTo_D)
    done

    lemma (in Extend) extending_LeadsTo:
         "extending (%G. reachable (extend h F\<squnion>G)) h F
                    (extend_set h A LeadsTo extend_set h B) (A LeadsTo B)"
    apply (unfold extending_def)
    apply (blast intro: project_LeadsTo_D)
    done

    ML
    {*
    val projecting_Int = thm "projecting_Int";
    val projecting_Un = thm "projecting_Un";
    val projecting_INT = thm "projecting_INT";
    val projecting_UN = thm "projecting_UN";
    val projecting_weaken = thm "projecting_weaken";
    val projecting_weaken_L = thm "projecting_weaken_L";
    val extending_Int = thm "extending_Int";
    val extending_Un = thm "extending_Un";
    val extending_INT = thm "extending_INT";
    val extending_UN = thm "extending_UN";
    val extending_weaken = thm "extending_weaken";
    val extending_weaken_L = thm "extending_weaken_L";
    val projecting_UNIV = thm "projecting_UNIV";
    *}

    end

lemma project_extend_constrains_I:

      [| Extend h; F ∈ A co B |] ==> project h C (extend h F) ∈ A co B

### Safety

lemma project_unless:

      [| Extend h; G ∈ stable C; project h C G ∈ A unless B |]
      ==> G ∈ C ∩ extend_set h A unless extend_set h B

lemma Join_project_constrains:

      Extend h
      ==> (F Join project h C G ∈ A co B) =
          (extend h F Join G ∈ C ∩ extend_set h A co extend_set h B ∧ F ∈ A co B)

lemma Join_project_stable:

      [| Extend h; extend h F Join G ∈ stable C |]
      ==> (F Join project h C G ∈ stable A) =
          (extend h F Join G ∈ stable (C ∩ extend_set h A) ∧ F ∈ stable A)

lemma project_constrains_I:

      [| Extend h; extend h F Join G ∈ extend_set h A co extend_set h B |]
      ==> F Join project h C G ∈ A co B

lemma project_increasing_I:

      [| Extend h; extend h F Join G ∈ increasing (func o (%z. fst (inv h z))) |]
      ==> F Join project h C G ∈ increasing func

lemma Join_project_increasing:

      Extend h
      ==> (F Join project h UNIV G ∈ increasing func) =
          (extend h F Join G ∈ increasing (func o (%z. fst (inv h z))))

lemma project_constrains_D:

      [| Extend h; F Join project h UNIV G ∈ A co B |]
      ==> extend h F Join G ∈ extend_set h A co extend_set h B

### "projecting" and union/intersection (no converses)

lemma projecting_Int:

      [| projecting C h F XA' XA; projecting C h F XB' XB |]
      ==> projecting C h F (XA' ∩ XB') (XA ∩ XB)

lemma projecting_Un:

      [| projecting C h F XA' XA; projecting C h F XB' XB |]
      ==> projecting C h F (XA' ∪ XB') (XA ∪ XB)

lemma projecting_INT:

      (!!i. i ∈ I ==> projecting C h F (X' i) (X i))
      ==> projecting C h F (INT i:I. X' i) (INT i:I. X i)

lemma projecting_UN:

      (!!i. i ∈ I ==> projecting C h F (X' i) (X i))
      ==> projecting C h F (UN i:I. X' i) (UN i:I. X i)

lemma projecting_weaken:

      [| projecting C h F X' X; U' ⊆ X'; X ⊆ U |] ==> projecting C h F U' U

lemma projecting_weaken_L:

      [| projecting C h F X' X; U' ⊆ X' |] ==> projecting C h F U' X

lemma extending_Int:

      [| extending C h F YA' YA; extending C h F YB' YB |]
      ==> extending C h F (YA' ∩ YB') (YA ∩ YB)

lemma extending_Un:

      [| extending C h F YA' YA; extending C h F YB' YB |]
      ==> extending C h F (YA' ∪ YB') (YA ∪ YB)

lemma extending_INT:

      (!!i. i ∈ I ==> extending C h F (Y' i) (Y i))
      ==> extending C h F (INT i:I. Y' i) (INT i:I. Y i)

lemma extending_UN:

      (!!i. i ∈ I ==> extending C h F (Y' i) (Y i))
      ==> extending C h F (UN i:I. Y' i) (UN i:I. Y i)

lemma extending_weaken:

      [| extending C h F Y' Y; Y' ⊆ V'; V ⊆ Y |] ==> extending C h F V' V

lemma extending_weaken_L:

      [| extending C h F Y' Y; Y' ⊆ V' |] ==> extending C h F V' Y

lemma projecting_UNIV:

      projecting C h F X' UNIV

lemma projecting_constrains:

      Extend h ==> projecting C h F (extend_set h A co extend_set h B) (A co B)

lemma projecting_stable:

      Extend h ==> projecting C h F (stable (extend_set h A)) (stable A)

lemma projecting_increasing:

      Extend h
      ==> projecting C h F (increasing (func o (%z. fst (inv h z)))) (increasing func)

lemma extending_UNIV:

      Extend h ==> extending C h F UNIV Y

lemma extending_constrains:

      Extend h
      ==> extending (%G. UNIV) h F (extend_set h A co extend_set h B) (A co B)

lemma extending_stable:

      Extend h ==> extending (%G. UNIV) h F (stable (extend_set h A)) (stable A)

lemma extending_increasing:

      Extend h
      ==> extending (%G. UNIV) h F (increasing (func o (%z. fst (inv h z))))
           (increasing func)

### Reachability and project

lemma reachable_imp_reachable_project:

      [| Extend h; reachable (extend h F Join G) ⊆ C;
         z ∈ reachable (extend h F Join G) |]
      ==> fst (inv h z) ∈ reachable (F Join project h C G)

lemma project_Constrains_D:

      [| Extend h; F Join project h (reachable (extend h F Join G)) G ∈ A Co B |]
      ==> extend h F Join G ∈ extend_set h A Co extend_set h B

lemma project_Stable_D:

      [| Extend h; F Join project h (reachable (extend h F Join G)) G ∈ Stable A |]
      ==> extend h F Join G ∈ Stable (extend_set h A)

lemma project_Always_D:

      [| Extend h; F Join project h (reachable (extend h F Join G)) G ∈ Always A |]
      ==> extend h F Join G ∈ Always (extend_set h A)

lemma project_Increasing_D:

      [| Extend h;
         F Join project h (reachable (extend h F Join G)) G ∈ Increasing func |]
      ==> extend h F Join G ∈ Increasing (func o (%z. fst (inv h z)))

### Converse results for weak safety: benefits of the argument C

lemma reachable_project_imp_reachable:

      [| Extend h; C ⊆ reachable (extend h F Join G);
         x ∈ reachable (F Join project h C G) |]
      ==> ∃y. h (x, y) ∈ reachable (extend h F Join G)

lemma project_set_reachable_extend_eq:

      Extend h
      ==> project_set h (reachable (extend h F Join G)) =
          reachable (F Join project h (reachable (extend h F Join G)) G)

lemma reachable_extend_Join_subset:

      [| Extend h; reachable (extend h F Join G) ⊆ C |]
      ==> reachable (extend h F Join G)
          ⊆ extend_set h (reachable (F Join project h C G))

lemma project_Constrains_I:

      [| Extend h; extend h F Join G ∈ extend_set h A Co extend_set h B |]
      ==> F Join project h (reachable (extend h F Join G)) G ∈ A Co B

lemma project_Stable_I:

      [| Extend h; extend h F Join G ∈ Stable (extend_set h A) |]
      ==> F Join project h (reachable (extend h F Join G)) G ∈ Stable A

lemma project_Always_I:

      [| Extend h; extend h F Join G ∈ Always (extend_set h A) |]
      ==> F Join project h (reachable (extend h F Join G)) G ∈ Always A

lemma project_Increasing_I:

      [| Extend h; extend h F Join G ∈ Increasing (func o (%z. fst (inv h z))) |]
      ==> F Join project h (reachable (extend h F Join G)) G ∈ Increasing func

lemma project_Constrains:

      Extend h
      ==> (F Join project h (reachable (extend h F Join G)) G ∈ A Co B) =
          (extend h F Join G ∈ extend_set h A Co extend_set h B)

lemma project_Stable:

      Extend h
      ==> (F Join project h (reachable (extend h F Join G)) G ∈ Stable A) =
          (extend h F Join G ∈ Stable (extend_set h A))

lemma project_Increasing:

      Extend h
      ==> (F Join project h (reachable (extend h F Join G)) G ∈ Increasing func) =
          (extend h F Join G ∈ Increasing (func o (%z. fst (inv h z))))

### A lot of redundant theorems: all are proved to facilitate reasoning about guarantees.

lemma projecting_Constrains:

      Extend h
      ==> projecting (%G. reachable (extend h F Join G)) h F
           (extend_set h A Co extend_set h B) (A Co B)

lemma projecting_Stable:

      Extend h
      ==> projecting (%G. reachable (extend h F Join G)) h F (Stable (extend_set h A))
           (Stable A)

lemma projecting_Always:

      Extend h
      ==> projecting (%G. reachable (extend h F Join G)) h F (Always (extend_set h A))
           (Always A)

lemma projecting_Increasing:

      Extend h
      ==> projecting (%G. reachable (extend h F Join G)) h F
           (Increasing (func o (%z. fst (inv h z)))) (Increasing func)

lemma extending_Constrains:

      Extend h
      ==> extending (%G. reachable (extend h F Join G)) h F
           (extend_set h A Co extend_set h B) (A Co B)

lemma extending_Stable:

      Extend h
      ==> extending (%G. reachable (extend h F Join G)) h F (Stable (extend_set h A))
           (Stable A)

lemma extending_Always:

      Extend h
      ==> extending (%G. reachable (extend h F Join G)) h F (Always (extend_set h A))
           (Always A)

lemma extending_Increasing:

      Extend h
      ==> extending (%G. reachable (extend h F Join G)) h F
           (Increasing (func o (%z. fst (inv h z)))) (Increasing func)

### leadsETo in the precondition (??)

#### transient

lemma transient_extend_set_imp_project_transient:

      [| Extend h; G ∈ transient (C ∩ extend_set h A); G ∈ stable C |]
      ==> project h C G ∈ transient (project_set h C ∩ A)

lemma project_extend_transient_D:

      [| Extend h; project h C (extend h F) ∈ transient (project_set h C ∩ D) |]
      ==> F ∈ transient (project_set h C ∩ D)

#### ensures -- a primitive combining progress with safety

lemma ensures_extend_set_imp_project_ensures:

      [| Extend h; extend h F ∈ stable C; G ∈ stable C;
         extend h F Join G ∈ A ensures B; A - B = C ∩ extend_set h D |]
      ==> F Join project h C G
          ∈ project_set h C ∩ project_set h A ensures project_set h B

lemma project_transient_extend_set:

      [| Extend h; project h C G ∈ transient (project_set h C ∩ A - B) |]
      ==> G ∈ transient (C ∩ extend_set h A - extend_set h B)

lemma project_unless2:

      [| Extend h; G ∈ stable C; project h C G ∈ project_set h C ∩ A unless B |]
      ==> G ∈ C ∩ extend_set h A unless extend_set h B

lemma extend_unless:

      [| Extend h; extend h F ∈ stable C; F ∈ A unless B |]
      ==> extend h F ∈ C ∩ extend_set h A unless extend_set h B

lemma Join_project_ensures:

      [| Extend h; extend h F Join G ∈ stable C; F Join project h C G ∈ A ensures B |]
      ==> extend h F Join G ∈ C ∩ extend_set h A ensures extend_set h B

lemma PLD_lemma:

      [| Extend h; extend h F Join G ∈ stable C;
         F Join project h C G ∈ project_set h C ∩ A leadsTo B |]
      ==> extend h F Join G
          ∈ C ∩ extend_set h (project_set h C ∩ A) leadsTo extend_set h B

lemma project_leadsTo_D_lemma:

      [| Extend h; extend h F Join G ∈ stable C;
         F Join project h C G ∈ project_set h C ∩ A leadsTo B |]
      ==> extend h F Join G ∈ C ∩ extend_set h A leadsTo extend_set h B

lemma Join_project_LeadsTo:

      [| Extend h; C = reachable (extend h F Join G);
         F Join project h C G ∈ A LeadsTo B |]
      ==> extend h F Join G ∈ extend_set h A LeadsTo extend_set h B

### Towards the theorem @{text project_Ensures_D}

lemma project_ensures_D_lemma:

      [| Extend h; G ∈ stable (C ∩ extend_set h A - extend_set h B);
         F Join project h C G ∈ project_set h C ∩ A ensures B;
         extend h F Join G ∈ stable C |]
      ==> extend h F Join G ∈ C ∩ extend_set h A ensures extend_set h B

lemma project_ensures_D:

      [| Extend h; F Join project h UNIV G ∈ A ensures B;
         G ∈ stable (extend_set h A - extend_set h B) |]
      ==> extend h F Join G ∈ extend_set h A ensures extend_set h B

lemma project_Ensures_D:

      [| Extend h; F Join project h (reachable (extend h F Join G)) G ∈ A Ensures B;
         G ∈ stable
              (reachable (extend h F Join G) ∩ extend_set h A - extend_set h B) |]
      ==> extend h F Join G ∈ extend_set h A Ensures extend_set h B

### Guarantees

lemma project_act_Restrict_subset_project_act:

      Extend h ==> project_act h (Restrict C act) ⊆ project_act h act

lemma subset_closed_ok_extend_imp_ok_project:

      [| Extend h; extend h F ok G; subset_closed (AllowedActs F) |]
      ==> F ok project h C G

lemma project_guarantees_raw:

      [| Extend h; F ∈ X guarantees Y; subset_closed (AllowedActs F);
         !!G. extend h F Join G ∈ X' ==> F Join project h (C G) G ∈ X;
         !!G. F Join project h (C G) G ∈ Y ==> extend h F Join G ∈ Y' |]
      ==> extend h F ∈ X' guarantees Y'

lemma project_guarantees:

      [| Extend h; F ∈ X guarantees Y; subset_closed (AllowedActs F);
         projecting C h F X' X; extending C h F Y' Y |]
      ==> extend h F ∈ X' guarantees Y'

### guarantees corollaries

#### Some could be deleted: the required versions are easy to prove

lemma extend_guar_increasing:

      [| Extend h; F ∈ UNIV guarantees increasing func;
         subset_closed (AllowedActs F) |]
      ==> extend h F ∈ X' guarantees increasing (func o (%z. fst (inv h z)))

lemma extend_guar_Increasing:

      [| Extend h; F ∈ UNIV guarantees Increasing func;
         subset_closed (AllowedActs F) |]
      ==> extend h F ∈ X' guarantees Increasing (func o (%z. fst (inv h z)))

lemma extend_guar_Always:

      [| Extend h; F ∈ Always A guarantees Always B; subset_closed (AllowedActs F) |]
      ==> extend h F ∈ Always (extend_set h A) guarantees Always (extend_set h B)

#### Guarantees with a leadsTo postcondition

lemma project_leadsTo_D:

      [| Extend h; F Join project h UNIV G ∈ A leadsTo B |]
      ==> extend h F Join G ∈ extend_set h A leadsTo extend_set h B

lemma project_LeadsTo_D:

      [| Extend h; F Join project h (reachable (extend h F Join G)) G ∈ A LeadsTo B |]
      ==> extend h F Join G ∈ extend_set h A LeadsTo extend_set h B

lemma extending_leadsTo:

      Extend h
      ==> extending (%G. UNIV) h F (extend_set h A leadsTo extend_set h B)
           (A leadsTo B)

lemma extending_LeadsTo:

      Extend h
      ==> extending (%G. reachable (extend h F Join G)) h F
           (extend_set h A LeadsTo extend_set h B) (A LeadsTo B)