src/HOL/UNITY/Constrains.thy
author paulson
Sat Feb 08 16:05:33 2003 +0100 (2003-02-08)
changeset 13812 91713a1915ee
parent 13805 3786b2fd6808
child 16417 9bc16273c2d4
permissions -rw-r--r--
converting HOL/UNITY to use unconditional fairness
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(*  Title:      HOL/UNITY/Constrains
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1998  University of Cambridge
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Weak safety relations: restricted to the set of reachable states.
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*)
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header{*Weak Safety*}
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theory Constrains = UNITY:
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consts traces :: "['a set, ('a * 'a)set set] => ('a * 'a list) set"
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  (*Initial states and program => (final state, reversed trace to it)...
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    Arguments MUST be curried in an inductive definition*)
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inductive "traces init acts"  
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  intros 
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         (*Initial trace is empty*)
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    Init:  "s \<in> init ==> (s,[]) \<in> traces init acts"
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    Acts:  "[| act: acts;  (s,evs) \<in> traces init acts;  (s,s'): act |]
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	    ==> (s', s#evs) \<in> traces init acts"
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consts reachable :: "'a program => 'a set"
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inductive "reachable F"
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  intros 
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    Init:  "s \<in> Init F ==> s \<in> reachable F"
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    Acts:  "[| act: Acts F;  s \<in> reachable F;  (s,s'): act |]
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	    ==> s' \<in> reachable F"
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constdefs
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  Constrains :: "['a set, 'a set] => 'a program set"  (infixl "Co" 60)
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    "A Co B == {F. F \<in> (reachable F \<inter> A)  co  B}"
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  Unless  :: "['a set, 'a set] => 'a program set"     (infixl "Unless" 60)
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    "A Unless B == (A-B) Co (A \<union> B)"
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  Stable     :: "'a set => 'a program set"
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    "Stable A == A Co A"
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  (*Always is the weak form of "invariant"*)
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  Always :: "'a set => 'a program set"
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    "Always A == {F. Init F \<subseteq> A} \<inter> Stable A"
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  (*Polymorphic in both states and the meaning of \<le> *)
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  Increasing :: "['a => 'b::{order}] => 'a program set"
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    "Increasing f == \<Inter>z. Stable {s. z \<le> f s}"
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subsection{*traces and reachable*}
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lemma reachable_equiv_traces:
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     "reachable F = {s. \<exists>evs. (s,evs) \<in> traces (Init F) (Acts F)}"
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apply safe
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apply (erule_tac [2] traces.induct)
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apply (erule reachable.induct)
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apply (blast intro: reachable.intros traces.intros)+
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done
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lemma Init_subset_reachable: "Init F \<subseteq> reachable F"
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by (blast intro: reachable.intros)
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lemma stable_reachable [intro!,simp]:
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     "Acts G \<subseteq> Acts F ==> G \<in> stable (reachable F)"
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by (blast intro: stableI constrainsI reachable.intros)
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(*The set of all reachable states is an invariant...*)
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lemma invariant_reachable: "F \<in> invariant (reachable F)"
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apply (simp add: invariant_def)
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apply (blast intro: reachable.intros)
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done
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(*...in fact the strongest invariant!*)
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lemma invariant_includes_reachable: "F \<in> invariant A ==> reachable F \<subseteq> A"
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apply (simp add: stable_def constrains_def invariant_def)
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apply (rule subsetI)
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apply (erule reachable.induct)
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apply (blast intro: reachable.intros)+
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done
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subsection{*Co*}
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(*F \<in> B co B' ==> F \<in> (reachable F \<inter> B) co (reachable F \<inter> B')*)
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lemmas constrains_reachable_Int =  
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    subset_refl [THEN stable_reachable [unfolded stable_def], 
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                 THEN constrains_Int, standard]
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(*Resembles the previous definition of Constrains*)
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lemma Constrains_eq_constrains: 
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     "A Co B = {F. F \<in> (reachable F  \<inter>  A) co (reachable F  \<inter>  B)}"
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apply (unfold Constrains_def)
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apply (blast dest: constrains_reachable_Int intro: constrains_weaken)
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done
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lemma constrains_imp_Constrains: "F \<in> A co A' ==> F \<in> A Co A'"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_weaken_L)
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done
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lemma stable_imp_Stable: "F \<in> stable A ==> F \<in> Stable A"
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apply (unfold stable_def Stable_def)
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apply (erule constrains_imp_Constrains)
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done
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lemma ConstrainsI: 
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    "(!!act s s'. [| act: Acts F;  (s,s') \<in> act;  s \<in> A |] ==> s': A')  
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     ==> F \<in> A Co A'"
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apply (rule constrains_imp_Constrains)
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apply (blast intro: constrainsI)
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done
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lemma Constrains_empty [iff]: "F \<in> {} Co B"
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by (unfold Constrains_def constrains_def, blast)
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lemma Constrains_UNIV [iff]: "F \<in> A Co UNIV"
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by (blast intro: ConstrainsI)
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lemma Constrains_weaken_R: 
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    "[| F \<in> A Co A'; A'<=B' |] ==> F \<in> A Co B'"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_weaken_R)
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done
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lemma Constrains_weaken_L: 
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    "[| F \<in> A Co A'; B \<subseteq> A |] ==> F \<in> B Co A'"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_weaken_L)
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done
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lemma Constrains_weaken: 
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   "[| F \<in> A Co A'; B \<subseteq> A; A'<=B' |] ==> F \<in> B Co B'"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_weaken)
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done
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(** Union **)
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lemma Constrains_Un: 
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    "[| F \<in> A Co A'; F \<in> B Co B' |] ==> F \<in> (A \<union> B) Co (A' \<union> B')"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_Un [THEN constrains_weaken])
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done
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lemma Constrains_UN: 
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  assumes Co: "!!i. i \<in> I ==> F \<in> (A i) Co (A' i)"
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  shows "F \<in> (\<Union>i \<in> I. A i) Co (\<Union>i \<in> I. A' i)"
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apply (unfold Constrains_def)
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apply (rule CollectI)
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apply (rule Co [unfolded Constrains_def, THEN CollectD, THEN constrains_UN, 
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                THEN constrains_weaken],   auto)
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done
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(** Intersection **)
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lemma Constrains_Int: 
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    "[| F \<in> A Co A'; F \<in> B Co B' |] ==> F \<in> (A \<inter> B) Co (A' \<inter> B')"
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apply (unfold Constrains_def)
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apply (blast intro: constrains_Int [THEN constrains_weaken])
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done
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lemma Constrains_INT: 
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  assumes Co: "!!i. i \<in> I ==> F \<in> (A i) Co (A' i)"
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  shows "F \<in> (\<Inter>i \<in> I. A i) Co (\<Inter>i \<in> I. A' i)"
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apply (unfold Constrains_def)
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apply (rule CollectI)
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apply (rule Co [unfolded Constrains_def, THEN CollectD, THEN constrains_INT, 
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                THEN constrains_weaken],   auto)
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done
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lemma Constrains_imp_subset: "F \<in> A Co A' ==> reachable F \<inter> A \<subseteq> A'"
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by (simp add: constrains_imp_subset Constrains_def)
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lemma Constrains_trans: "[| F \<in> A Co B; F \<in> B Co C |] ==> F \<in> A Co C"
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apply (simp add: Constrains_eq_constrains)
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apply (blast intro: constrains_trans constrains_weaken)
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done
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lemma Constrains_cancel:
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     "[| F \<in> A Co (A' \<union> B); F \<in> B Co B' |] ==> F \<in> A Co (A' \<union> B')"
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by (simp add: Constrains_eq_constrains constrains_def, blast)
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subsection{*Stable*}
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(*Useful because there's no Stable_weaken.  [Tanja Vos]*)
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lemma Stable_eq: "[| F \<in> Stable A; A = B |] ==> F \<in> Stable B"
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by blast
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lemma Stable_eq_stable: "(F \<in> Stable A) = (F \<in> stable (reachable F \<inter> A))"
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by (simp add: Stable_def Constrains_eq_constrains stable_def)
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lemma StableI: "F \<in> A Co A ==> F \<in> Stable A"
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by (unfold Stable_def, assumption)
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lemma StableD: "F \<in> Stable A ==> F \<in> A Co A"
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by (unfold Stable_def, assumption)
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lemma Stable_Un: 
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    "[| F \<in> Stable A; F \<in> Stable A' |] ==> F \<in> Stable (A \<union> A')"
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apply (unfold Stable_def)
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apply (blast intro: Constrains_Un)
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done
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lemma Stable_Int: 
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    "[| F \<in> Stable A; F \<in> Stable A' |] ==> F \<in> Stable (A \<inter> A')"
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apply (unfold Stable_def)
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apply (blast intro: Constrains_Int)
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done
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lemma Stable_Constrains_Un: 
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    "[| F \<in> Stable C; F \<in> A Co (C \<union> A') |]    
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     ==> F \<in> (C \<union> A) Co (C \<union> A')"
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apply (unfold Stable_def)
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apply (blast intro: Constrains_Un [THEN Constrains_weaken])
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done
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lemma Stable_Constrains_Int: 
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    "[| F \<in> Stable C; F \<in> (C \<inter> A) Co A' |]    
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     ==> F \<in> (C \<inter> A) Co (C \<inter> A')"
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apply (unfold Stable_def)
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apply (blast intro: Constrains_Int [THEN Constrains_weaken])
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done
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lemma Stable_UN: 
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    "(!!i. i \<in> I ==> F \<in> Stable (A i)) ==> F \<in> Stable (\<Union>i \<in> I. A i)"
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by (simp add: Stable_def Constrains_UN) 
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lemma Stable_INT: 
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    "(!!i. i \<in> I ==> F \<in> Stable (A i)) ==> F \<in> Stable (\<Inter>i \<in> I. A i)"
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by (simp add: Stable_def Constrains_INT) 
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lemma Stable_reachable: "F \<in> Stable (reachable F)"
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by (simp add: Stable_eq_stable)
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subsection{*Increasing*}
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lemma IncreasingD: 
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     "F \<in> Increasing f ==> F \<in> Stable {s. x \<le> f s}"
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by (unfold Increasing_def, blast)
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lemma mono_Increasing_o: 
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     "mono g ==> Increasing f \<subseteq> Increasing (g o f)"
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apply (simp add: Increasing_def Stable_def Constrains_def stable_def 
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                 constrains_def)
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apply (blast intro: monoD order_trans)
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done
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lemma strict_IncreasingD: 
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     "!!z::nat. F \<in> Increasing f ==> F \<in> Stable {s. z < f s}"
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by (simp add: Increasing_def Suc_le_eq [symmetric])
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lemma increasing_imp_Increasing: 
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     "F \<in> increasing f ==> F \<in> Increasing f"
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apply (unfold increasing_def Increasing_def)
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apply (blast intro: stable_imp_Stable)
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done
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lemmas Increasing_constant =  
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    increasing_constant [THEN increasing_imp_Increasing, standard, iff]
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subsection{*The Elimination Theorem*}
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(*The "free" m has become universally quantified! Should the premise be !!m
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instead of \<forall>m ?  Would make it harder to use in forward proof.*)
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lemma Elimination: 
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    "[| \<forall>m. F \<in> {s. s x = m} Co (B m) |]  
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     ==> F \<in> {s. s x \<in> M} Co (\<Union>m \<in> M. B m)"
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by (unfold Constrains_def constrains_def, blast)
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(*As above, but for the trivial case of a one-variable state, in which the
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  state is identified with its one variable.*)
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lemma Elimination_sing: 
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    "(\<forall>m. F \<in> {m} Co (B m)) ==> F \<in> M Co (\<Union>m \<in> M. B m)"
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by (unfold Constrains_def constrains_def, blast)
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subsection{*Specialized laws for handling Always*}
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(** Natural deduction rules for "Always A" **)
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lemma AlwaysI: "[| Init F \<subseteq> A;  F \<in> Stable A |] ==> F \<in> Always A"
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by (simp add: Always_def)
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lemma AlwaysD: "F \<in> Always A ==> Init F \<subseteq> A & F \<in> Stable A"
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by (simp add: Always_def)
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lemmas AlwaysE = AlwaysD [THEN conjE, standard]
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lemmas Always_imp_Stable = AlwaysD [THEN conjunct2, standard]
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(*The set of all reachable states is Always*)
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lemma Always_includes_reachable: "F \<in> Always A ==> reachable F \<subseteq> A"
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apply (simp add: Stable_def Constrains_def constrains_def Always_def)
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apply (rule subsetI)
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apply (erule reachable.induct)
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apply (blast intro: reachable.intros)+
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done
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lemma invariant_imp_Always: 
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     "F \<in> invariant A ==> F \<in> Always A"
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apply (unfold Always_def invariant_def Stable_def stable_def)
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apply (blast intro: constrains_imp_Constrains)
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done
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lemmas Always_reachable =
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    invariant_reachable [THEN invariant_imp_Always, standard]
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lemma Always_eq_invariant_reachable:
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     "Always A = {F. F \<in> invariant (reachable F \<inter> A)}"
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apply (simp add: Always_def invariant_def Stable_def Constrains_eq_constrains
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                 stable_def)
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apply (blast intro: reachable.intros)
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done
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(*the RHS is the traditional definition of the "always" operator*)
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lemma Always_eq_includes_reachable: "Always A = {F. reachable F \<subseteq> A}"
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by (auto dest: invariant_includes_reachable simp add: Int_absorb2 invariant_reachable Always_eq_invariant_reachable)
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lemma Always_UNIV_eq [simp]: "Always UNIV = UNIV"
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by (auto simp add: Always_eq_includes_reachable)
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lemma UNIV_AlwaysI: "UNIV \<subseteq> A ==> F \<in> Always A"
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by (auto simp add: Always_eq_includes_reachable)
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lemma Always_eq_UN_invariant: "Always A = (\<Union>I \<in> Pow A. invariant I)"
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apply (simp add: Always_eq_includes_reachable)
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apply (blast intro: invariantI Init_subset_reachable [THEN subsetD] 
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                    invariant_includes_reachable [THEN subsetD])
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done
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lemma Always_weaken: "[| F \<in> Always A; A \<subseteq> B |] ==> F \<in> Always B"
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by (auto simp add: Always_eq_includes_reachable)
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subsection{*"Co" rules involving Always*}
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lemma Always_Constrains_pre:
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     "F \<in> Always INV ==> (F \<in> (INV \<inter> A) Co A') = (F \<in> A Co A')"
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by (simp add: Always_includes_reachable [THEN Int_absorb2] Constrains_def 
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              Int_assoc [symmetric])
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lemma Always_Constrains_post:
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     "F \<in> Always INV ==> (F \<in> A Co (INV \<inter> A')) = (F \<in> A Co A')"
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by (simp add: Always_includes_reachable [THEN Int_absorb2] 
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              Constrains_eq_constrains Int_assoc [symmetric])
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(* [| F \<in> Always INV;  F \<in> (INV \<inter> A) Co A' |] ==> F \<in> A Co A' *)
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lemmas Always_ConstrainsI = Always_Constrains_pre [THEN iffD1, standard]
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(* [| F \<in> Always INV;  F \<in> A Co A' |] ==> F \<in> A Co (INV \<inter> A') *)
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lemmas Always_ConstrainsD = Always_Constrains_post [THEN iffD2, standard]
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(*The analogous proof of Always_LeadsTo_weaken doesn't terminate*)
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lemma Always_Constrains_weaken:
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     "[| F \<in> Always C;  F \<in> A Co A';    
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         C \<inter> B \<subseteq> A;   C \<inter> A' \<subseteq> B' |]  
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      ==> F \<in> B Co B'"
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apply (rule Always_ConstrainsI, assumption)
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apply (drule Always_ConstrainsD, assumption)
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apply (blast intro: Constrains_weaken)
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done
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(** Conjoining Always properties **)
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lemma Always_Int_distrib: "Always (A \<inter> B) = Always A \<inter> Always B"
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by (auto simp add: Always_eq_includes_reachable)
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lemma Always_INT_distrib: "Always (INTER I A) = (\<Inter>i \<in> I. Always (A i))"
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by (auto simp add: Always_eq_includes_reachable)
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lemma Always_Int_I:
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     "[| F \<in> Always A;  F \<in> Always B |] ==> F \<in> Always (A \<inter> B)"
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by (simp add: Always_Int_distrib)
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(*Allows a kind of "implication introduction"*)
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lemma Always_Compl_Un_eq:
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     "F \<in> Always A ==> (F \<in> Always (-A \<union> B)) = (F \<in> Always B)"
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by (auto simp add: Always_eq_includes_reachable)
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(*Delete the nearest invariance assumption (which will be the second one
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  used by Always_Int_I) *)
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lemmas Always_thin = thin_rl [of "F \<in> Always A", standard]
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subsection{*Totalize*}
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lemma reachable_imp_reachable_tot:
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      "s \<in> reachable F ==> s \<in> reachable (totalize F)"
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apply (erule reachable.induct)
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 apply (rule reachable.Init) 
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 apply simp 
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apply (rule_tac act = "totalize_act act" in reachable.Acts) 
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apply (auto simp add: totalize_act_def) 
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done
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lemma reachable_tot_imp_reachable:
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      "s \<in> reachable (totalize F) ==> s \<in> reachable F"
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apply (erule reachable.induct)
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 apply (rule reachable.Init, simp) 
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apply (force simp add: totalize_act_def intro: reachable.Acts) 
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done
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lemma reachable_tot_eq [simp]: "reachable (totalize F) = reachable F"
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by (blast intro: reachable_imp_reachable_tot reachable_tot_imp_reachable) 
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lemma totalize_Constrains_iff [simp]: "(totalize F \<in> A Co B) = (F \<in> A Co B)"
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by (simp add: Constrains_def) 
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lemma totalize_Stable_iff [simp]: "(totalize F \<in> Stable A) = (F \<in> Stable A)"
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by (simp add: Stable_def)
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lemma totalize_Always_iff [simp]: "(totalize F \<in> Always A) = (F \<in> Always A)"
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by (simp add: Always_def)
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end