src/HOL/UNITY/Guar.thy
author wenzelm
Fri Mar 28 19:43:54 2008 +0100 (2008-03-28)
changeset 26462 dac4e2bce00d
parent 16647 c6d81ddebb0e
child 27682 25aceefd4786
permissions -rw-r--r--
avoid rebinding of existing facts;
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(*  Title:      HOL/UNITY/Guar.thy
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1999  University of Cambridge
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From Chandy and Sanders, "Reasoning About Program Composition",
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Technical Report 2000-003, University of Florida, 2000.
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Revised by Sidi Ehmety on January 2001
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Added: Compatibility, weakest guarantees, etc.
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and Weakest existential property,
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from Charpentier and Chandy "Theorems about Composition",
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Fifth International Conference on Mathematics of Program, 2000.
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*)
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header{*Guarantees Specifications*}
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theory Guar imports Comp begin
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instance program :: (type) order
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  by (intro_classes,
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      (assumption | rule component_refl component_trans component_antisym
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                     program_less_le)+)
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text{*Existential and Universal properties.  I formalize the two-program
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      case, proving equivalence with Chandy and Sanders's n-ary definitions*}
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constdefs
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  ex_prop  :: "'a program set => bool"
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   "ex_prop X == \<forall>F G. F ok G -->F \<in> X | G \<in> X --> (F\<squnion>G) \<in> X"
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  strict_ex_prop  :: "'a program set => bool"
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   "strict_ex_prop X == \<forall>F G.  F ok G --> (F \<in> X | G \<in> X) = (F\<squnion>G \<in> X)"
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  uv_prop  :: "'a program set => bool"
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   "uv_prop X == SKIP \<in> X & (\<forall>F G. F ok G --> F \<in> X & G \<in> X --> (F\<squnion>G) \<in> X)"
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  strict_uv_prop  :: "'a program set => bool"
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   "strict_uv_prop X == 
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      SKIP \<in> X & (\<forall>F G. F ok G --> (F \<in> X & G \<in> X) = (F\<squnion>G \<in> X))"
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text{*Guarantees properties*}
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constdefs
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  guar :: "['a program set, 'a program set] => 'a program set"
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          (infixl "guarantees" 55)  (*higher than membership, lower than Co*)
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   "X guarantees Y == {F. \<forall>G. F ok G --> F\<squnion>G \<in> X --> F\<squnion>G \<in> Y}"
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  (* Weakest guarantees *)
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   wg :: "['a program, 'a program set] =>  'a program set"
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  "wg F Y == Union({X. F \<in> X guarantees Y})"
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   (* Weakest existential property stronger than X *)
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   wx :: "('a program) set => ('a program)set"
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   "wx X == Union({Y. Y \<subseteq> X & ex_prop Y})"
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  (*Ill-defined programs can arise through "Join"*)
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  welldef :: "'a program set"
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  "welldef == {F. Init F \<noteq> {}}"
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  refines :: "['a program, 'a program, 'a program set] => bool"
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			("(3_ refines _ wrt _)" [10,10,10] 10)
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  "G refines F wrt X ==
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     \<forall>H. (F ok H & G ok H & F\<squnion>H \<in> welldef \<inter> X) --> 
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         (G\<squnion>H \<in> welldef \<inter> X)"
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  iso_refines :: "['a program, 'a program, 'a program set] => bool"
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                              ("(3_ iso'_refines _ wrt _)" [10,10,10] 10)
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  "G iso_refines F wrt X ==
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   F \<in> welldef \<inter> X --> G \<in> welldef \<inter> X"
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lemma OK_insert_iff:
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     "(OK (insert i I) F) = 
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      (if i \<in> I then OK I F else OK I F & (F i ok JOIN I F))"
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by (auto intro: ok_sym simp add: OK_iff_ok)
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subsection{*Existential Properties*}
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lemma ex1 [rule_format]: 
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 "[| ex_prop X; finite GG |] ==>  
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     GG \<inter> X \<noteq> {}--> OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X"
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apply (unfold ex_prop_def)
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apply (erule finite_induct)
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apply (auto simp add: OK_insert_iff Int_insert_left)
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done
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lemma ex2: 
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     "\<forall>GG. finite GG & GG \<inter> X \<noteq> {} --> OK GG (%G. G) -->(\<Squnion>G \<in> GG. G):X 
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      ==> ex_prop X"
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apply (unfold ex_prop_def, clarify)
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apply (drule_tac x = "{F,G}" in spec)
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apply (auto dest: ok_sym simp add: OK_iff_ok)
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done
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(*Chandy & Sanders take this as a definition*)
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lemma ex_prop_finite:
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     "ex_prop X = 
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      (\<forall>GG. finite GG & GG \<inter> X \<noteq> {} & OK GG (%G. G)--> (\<Squnion>G \<in> GG. G) \<in> X)"
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by (blast intro: ex1 ex2)
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(*Their "equivalent definition" given at the end of section 3*)
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lemma ex_prop_equiv: 
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     "ex_prop X = (\<forall>G. G \<in> X = (\<forall>H. (G component_of H) --> H \<in> X))"
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apply auto
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apply (unfold ex_prop_def component_of_def, safe, blast, blast) 
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apply (subst Join_commute) 
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apply (drule ok_sym, blast) 
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done
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subsection{*Universal Properties*}
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lemma uv1 [rule_format]: 
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     "[| uv_prop X; finite GG |] 
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      ==> GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X"
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apply (unfold uv_prop_def)
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apply (erule finite_induct)
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apply (auto simp add: Int_insert_left OK_insert_iff)
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done
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lemma uv2: 
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     "\<forall>GG. finite GG & GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X  
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      ==> uv_prop X"
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apply (unfold uv_prop_def)
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apply (rule conjI)
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 apply (drule_tac x = "{}" in spec)
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 prefer 2
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 apply clarify 
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 apply (drule_tac x = "{F,G}" in spec)
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apply (auto dest: ok_sym simp add: OK_iff_ok)
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done
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(*Chandy & Sanders take this as a definition*)
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lemma uv_prop_finite:
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     "uv_prop X = 
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      (\<forall>GG. finite GG & GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G): X)"
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by (blast intro: uv1 uv2)
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subsection{*Guarantees*}
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lemma guaranteesI:
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     "(!!G. [| F ok G; F\<squnion>G \<in> X |] ==> F\<squnion>G \<in> Y) ==> F \<in> X guarantees Y"
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by (simp add: guar_def component_def)
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lemma guaranteesD: 
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     "[| F \<in> X guarantees Y;  F ok G;  F\<squnion>G \<in> X |] ==> F\<squnion>G \<in> Y"
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by (unfold guar_def component_def, blast)
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(*This version of guaranteesD matches more easily in the conclusion
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  The major premise can no longer be  F \<subseteq> H since we need to reason about G*)
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lemma component_guaranteesD: 
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     "[| F \<in> X guarantees Y;  F\<squnion>G = H;  H \<in> X;  F ok G |] ==> H \<in> Y"
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by (unfold guar_def, blast)
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lemma guarantees_weaken: 
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     "[| F \<in> X guarantees X'; Y \<subseteq> X; X' \<subseteq> Y' |] ==> F \<in> Y guarantees Y'"
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by (unfold guar_def, blast)
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lemma subset_imp_guarantees_UNIV: "X \<subseteq> Y ==> X guarantees Y = UNIV"
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by (unfold guar_def, blast)
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(*Equivalent to subset_imp_guarantees_UNIV but more intuitive*)
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lemma subset_imp_guarantees: "X \<subseteq> Y ==> F \<in> X guarantees Y"
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by (unfold guar_def, blast)
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(*Remark at end of section 4.1 *)
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lemma ex_prop_imp: "ex_prop Y ==> (Y = UNIV guarantees Y)"
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apply (simp (no_asm_use) add: guar_def ex_prop_equiv)
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apply safe
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 apply (drule_tac x = x in spec)
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 apply (drule_tac [2] x = x in spec)
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 apply (drule_tac [2] sym)
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apply (auto simp add: component_of_def)
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done
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lemma guarantees_imp: "(Y = UNIV guarantees Y) ==> ex_prop(Y)"
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by (auto simp add: guar_def ex_prop_equiv component_of_def dest: sym)
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lemma ex_prop_equiv2: "(ex_prop Y) = (Y = UNIV guarantees Y)"
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apply (rule iffI)
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apply (rule ex_prop_imp)
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apply (auto simp add: guarantees_imp) 
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done
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subsection{*Distributive Laws.  Re-Orient to Perform Miniscoping*}
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lemma guarantees_UN_left: 
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     "(\<Union>i \<in> I. X i) guarantees Y = (\<Inter>i \<in> I. X i guarantees Y)"
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by (unfold guar_def, blast)
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lemma guarantees_Un_left: 
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     "(X \<union> Y) guarantees Z = (X guarantees Z) \<inter> (Y guarantees Z)"
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by (unfold guar_def, blast)
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lemma guarantees_INT_right: 
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     "X guarantees (\<Inter>i \<in> I. Y i) = (\<Inter>i \<in> I. X guarantees Y i)"
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by (unfold guar_def, blast)
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lemma guarantees_Int_right: 
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     "Z guarantees (X \<inter> Y) = (Z guarantees X) \<inter> (Z guarantees Y)"
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by (unfold guar_def, blast)
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lemma guarantees_Int_right_I:
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     "[| F \<in> Z guarantees X;  F \<in> Z guarantees Y |]  
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     ==> F \<in> Z guarantees (X \<inter> Y)"
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by (simp add: guarantees_Int_right)
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lemma guarantees_INT_right_iff:
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     "(F \<in> X guarantees (INTER I Y)) = (\<forall>i\<in>I. F \<in> X guarantees (Y i))"
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by (simp add: guarantees_INT_right)
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lemma shunting: "(X guarantees Y) = (UNIV guarantees (-X \<union> Y))"
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by (unfold guar_def, blast)
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lemma contrapositive: "(X guarantees Y) = -Y guarantees -X"
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by (unfold guar_def, blast)
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(** The following two can be expressed using intersection and subset, which
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    is more faithful to the text but looks cryptic.
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**)
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lemma combining1: 
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    "[| F \<in> V guarantees X;  F \<in> (X \<inter> Y) guarantees Z |] 
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     ==> F \<in> (V \<inter> Y) guarantees Z"
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by (unfold guar_def, blast)
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lemma combining2: 
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    "[| F \<in> V guarantees (X \<union> Y);  F \<in> Y guarantees Z |] 
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     ==> F \<in> V guarantees (X \<union> Z)"
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by (unfold guar_def, blast)
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(** The following two follow Chandy-Sanders, but the use of object-quantifiers
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    does not suit Isabelle... **)
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(*Premise should be (!!i. i \<in> I ==> F \<in> X guarantees Y i) *)
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lemma all_guarantees: 
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     "\<forall>i\<in>I. F \<in> X guarantees (Y i) ==> F \<in> X guarantees (\<Inter>i \<in> I. Y i)"
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by (unfold guar_def, blast)
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(*Premises should be [| F \<in> X guarantees Y i; i \<in> I |] *)
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lemma ex_guarantees: 
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     "\<exists>i\<in>I. F \<in> X guarantees (Y i) ==> F \<in> X guarantees (\<Union>i \<in> I. Y i)"
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by (unfold guar_def, blast)
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subsection{*Guarantees: Additional Laws (by lcp)*}
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lemma guarantees_Join_Int: 
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    "[| F \<in> U guarantees V;  G \<in> X guarantees Y; F ok G |]  
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     ==> F\<squnion>G \<in> (U \<inter> X) guarantees (V \<inter> Y)"
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apply (simp add: guar_def, safe)
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 apply (simp add: Join_assoc)
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apply (subgoal_tac "F\<squnion>G\<squnion>Ga = G\<squnion>(F\<squnion>Ga) ")
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 apply (simp add: ok_commute)
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apply (simp add: Join_ac)
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done
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lemma guarantees_Join_Un: 
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    "[| F \<in> U guarantees V;  G \<in> X guarantees Y; F ok G |]   
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     ==> F\<squnion>G \<in> (U \<union> X) guarantees (V \<union> Y)"
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apply (simp add: guar_def, safe)
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 apply (simp add: Join_assoc)
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apply (subgoal_tac "F\<squnion>G\<squnion>Ga = G\<squnion>(F\<squnion>Ga) ")
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 apply (simp add: ok_commute)
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apply (simp add: Join_ac)
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done
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lemma guarantees_JN_INT: 
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     "[| \<forall>i\<in>I. F i \<in> X i guarantees Y i;  OK I F |]  
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      ==> (JOIN I F) \<in> (INTER I X) guarantees (INTER I Y)"
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apply (unfold guar_def, auto)
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apply (drule bspec, assumption)
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apply (rename_tac "i")
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apply (drule_tac x = "JOIN (I-{i}) F\<squnion>G" in spec)
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apply (auto intro: OK_imp_ok
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            simp add: Join_assoc [symmetric] JN_Join_diff JN_absorb)
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done
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lemma guarantees_JN_UN: 
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    "[| \<forall>i\<in>I. F i \<in> X i guarantees Y i;  OK I F |]  
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     ==> (JOIN I F) \<in> (UNION I X) guarantees (UNION I Y)"
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apply (unfold guar_def, auto)
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apply (drule bspec, assumption)
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apply (rename_tac "i")
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apply (drule_tac x = "JOIN (I-{i}) F\<squnion>G" in spec)
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apply (auto intro: OK_imp_ok
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            simp add: Join_assoc [symmetric] JN_Join_diff JN_absorb)
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done
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subsection{*Guarantees Laws for Breaking Down the Program (by lcp)*}
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lemma guarantees_Join_I1: 
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     "[| F \<in> X guarantees Y;  F ok G |] ==> F\<squnion>G \<in> X guarantees Y"
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by (simp add: guar_def Join_assoc)
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lemma guarantees_Join_I2:         
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     "[| G \<in> X guarantees Y;  F ok G |] ==> F\<squnion>G \<in> X guarantees Y"
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apply (simp add: Join_commute [of _ G] ok_commute [of _ G])
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apply (blast intro: guarantees_Join_I1)
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done
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lemma guarantees_JN_I: 
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     "[| i \<in> I;  F i \<in> X guarantees Y;  OK I F |]  
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      ==> (\<Squnion>i \<in> I. (F i)) \<in> X guarantees Y"
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apply (unfold guar_def, clarify)
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apply (drule_tac x = "JOIN (I-{i}) F\<squnion>G" in spec)
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apply (auto intro: OK_imp_ok 
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            simp add: JN_Join_diff JN_Join_diff Join_assoc [symmetric])
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done
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(*** well-definedness ***)
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lemma Join_welldef_D1: "F\<squnion>G \<in> welldef ==> F \<in> welldef"
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by (unfold welldef_def, auto)
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lemma Join_welldef_D2: "F\<squnion>G \<in> welldef ==> G \<in> welldef"
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by (unfold welldef_def, auto)
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(*** refinement ***)
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lemma refines_refl: "F refines F wrt X"
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by (unfold refines_def, blast)
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(*We'd like transitivity, but how do we get it?*)
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lemma refines_trans:
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     "[| H refines G wrt X;  G refines F wrt X |] ==> H refines F wrt X"
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apply (simp add: refines_def) 
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oops
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lemma strict_ex_refine_lemma: 
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     "strict_ex_prop X  
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      ==> (\<forall>H. F ok H & G ok H & F\<squnion>H \<in> X --> G\<squnion>H \<in> X)  
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              = (F \<in> X --> G \<in> X)"
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by (unfold strict_ex_prop_def, auto)
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lemma strict_ex_refine_lemma_v: 
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     "strict_ex_prop X  
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      ==> (\<forall>H. F ok H & G ok H & F\<squnion>H \<in> welldef & F\<squnion>H \<in> X --> G\<squnion>H \<in> X) =  
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          (F \<in> welldef \<inter> X --> G \<in> X)"
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apply (unfold strict_ex_prop_def, safe)
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apply (erule_tac x = SKIP and P = "%H. ?PP H --> ?RR H" in allE)
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apply (auto dest: Join_welldef_D1 Join_welldef_D2)
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done
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lemma ex_refinement_thm:
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     "[| strict_ex_prop X;   
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         \<forall>H. F ok H & G ok H & F\<squnion>H \<in> welldef \<inter> X --> G\<squnion>H \<in> welldef |]  
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      ==> (G refines F wrt X) = (G iso_refines F wrt X)"
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apply (rule_tac x = SKIP in allE, assumption)
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apply (simp add: refines_def iso_refines_def strict_ex_refine_lemma_v)
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done
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lemma strict_uv_refine_lemma: 
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     "strict_uv_prop X ==> 
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      (\<forall>H. F ok H & G ok H & F\<squnion>H \<in> X --> G\<squnion>H \<in> X) = (F \<in> X --> G \<in> X)"
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by (unfold strict_uv_prop_def, blast)
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lemma strict_uv_refine_lemma_v: 
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     "strict_uv_prop X  
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      ==> (\<forall>H. F ok H & G ok H & F\<squnion>H \<in> welldef & F\<squnion>H \<in> X --> G\<squnion>H \<in> X) =  
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          (F \<in> welldef \<inter> X --> G \<in> X)"
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apply (unfold strict_uv_prop_def, safe)
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apply (erule_tac x = SKIP and P = "%H. ?PP H --> ?RR H" in allE)
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apply (auto dest: Join_welldef_D1 Join_welldef_D2)
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done
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lemma uv_refinement_thm:
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     "[| strict_uv_prop X;   
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         \<forall>H. F ok H & G ok H & F\<squnion>H \<in> welldef \<inter> X --> 
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             G\<squnion>H \<in> welldef |]  
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      ==> (G refines F wrt X) = (G iso_refines F wrt X)"
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apply (rule_tac x = SKIP in allE, assumption)
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apply (simp add: refines_def iso_refines_def strict_uv_refine_lemma_v)
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done
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(* Added by Sidi Ehmety from Chandy & Sander, section 6 *)
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lemma guarantees_equiv: 
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    "(F \<in> X guarantees Y) = (\<forall>H. H \<in> X \<longrightarrow> (F component_of H \<longrightarrow> H \<in> Y))"
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by (unfold guar_def component_of_def, auto)
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   399
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   400
lemma wg_weakest: "!!X. F\<in> (X guarantees Y) ==> X \<subseteq> (wg F Y)"
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by (unfold wg_def, auto)
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   402
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lemma wg_guarantees: "F\<in> ((wg F Y) guarantees Y)"
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   404
by (unfold wg_def guar_def, blast)
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   405
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   406
lemma wg_equiv: "(H \<in> wg F X) = (F component_of H --> H \<in> X)"
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   407
by (simp add: guarantees_equiv wg_def, blast)
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   408
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lemma component_of_wg: "F component_of H ==> (H \<in> wg F X) = (H \<in> X)"
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   410
by (simp add: wg_equiv)
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   411
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   412
lemma wg_finite: 
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    "\<forall>FF. finite FF & FF \<inter> X \<noteq> {} --> OK FF (%F. F)  
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          --> (\<forall>F\<in>FF. ((\<Squnion>F \<in> FF. F): wg F X) = ((\<Squnion>F \<in> FF. F):X))"
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apply clarify
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apply (subgoal_tac "F component_of (\<Squnion>F \<in> FF. F) ")
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apply (drule_tac X = X in component_of_wg, simp)
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apply (simp add: component_of_def)
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   419
apply (rule_tac x = "\<Squnion>F \<in> (FF-{F}) . F" in exI)
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   420
apply (auto intro: JN_Join_diff dest: ok_sym simp add: OK_iff_ok)
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   421
done
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   422
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   423
lemma wg_ex_prop: "ex_prop X ==> (F \<in> X) = (\<forall>H. H \<in> wg F X)"
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   424
apply (simp (no_asm_use) add: ex_prop_equiv wg_equiv)
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   425
apply blast
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   426
done
paulson@13792
   427
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   428
(** From Charpentier and Chandy "Theorems About Composition" **)
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   429
(* Proposition 2 *)
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   430
lemma wx_subset: "(wx X)<=X"
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   431
by (unfold wx_def, auto)
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   432
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lemma wx_ex_prop: "ex_prop (wx X)"
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apply (simp add: wx_def ex_prop_equiv cong: bex_cong, safe, blast)
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   435
apply force 
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   436
done
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   437
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   438
lemma wx_weakest: "\<forall>Z. Z<= X --> ex_prop Z --> Z \<subseteq> wx X"
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   439
by (auto simp add: wx_def)
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   440
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   441
(* Proposition 6 *)
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   442
lemma wx'_ex_prop: "ex_prop({F. \<forall>G. F ok G --> F\<squnion>G \<in> X})"
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   443
apply (unfold ex_prop_def, safe)
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   444
 apply (drule_tac x = "G\<squnion>Ga" in spec)
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   445
 apply (force simp add: ok_Join_iff1 Join_assoc)
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   446
apply (drule_tac x = "F\<squnion>Ga" in spec)
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   447
apply (simp add: ok_Join_iff1 ok_commute  Join_ac) 
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   448
done
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   449
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   450
text{* Equivalence with the other definition of wx *}
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   451
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   452
lemma wx_equiv: "wx X = {F. \<forall>G. F ok G --> (F\<squnion>G) \<in> X}"
paulson@13792
   453
apply (unfold wx_def, safe)
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   454
 apply (simp add: ex_prop_def, blast) 
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   455
apply (simp (no_asm))
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   456
apply (rule_tac x = "{F. \<forall>G. F ok G --> F\<squnion>G \<in> X}" in exI, safe)
paulson@13792
   457
apply (rule_tac [2] wx'_ex_prop)
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   458
apply (drule_tac x = SKIP in spec)+
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   459
apply auto 
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   460
done
paulson@13792
   461
paulson@13792
   462
paulson@14112
   463
text{* Propositions 7 to 11 are about this second definition of wx. 
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   They are the same as the ones proved for the first definition of wx,
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   465
 by equivalence *}
paulson@13792
   466
   
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   467
(* Proposition 12 *)
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   468
(* Main result of the paper *)
paulson@14112
   469
lemma guarantees_wx_eq: "(X guarantees Y) = wx(-X \<union> Y)"
paulson@14112
   470
by (simp add: guar_def wx_equiv)
paulson@13792
   471
paulson@13792
   472
paulson@13792
   473
(* Rules given in section 7 of Chandy and Sander's
paulson@13792
   474
    Reasoning About Program composition paper *)
paulson@13792
   475
lemma stable_guarantees_Always:
paulson@14112
   476
     "Init F \<subseteq> A ==> F \<in> (stable A) guarantees (Always A)"
paulson@13792
   477
apply (rule guaranteesI)
paulson@14112
   478
apply (simp add: Join_commute)
paulson@13792
   479
apply (rule stable_Join_Always1)
paulson@14112
   480
 apply (simp_all add: invariant_def Join_stable)
paulson@13792
   481
done
paulson@13792
   482
paulson@13792
   483
lemma constrains_guarantees_leadsTo:
paulson@13805
   484
     "F \<in> transient A ==> F \<in> (A co A \<union> B) guarantees (A leadsTo (B-A))"
paulson@13792
   485
apply (rule guaranteesI)
paulson@13792
   486
apply (rule leadsTo_Basis')
paulson@14112
   487
 apply (drule constrains_weaken_R)
paulson@14112
   488
  prefer 2 apply assumption
paulson@14112
   489
 apply blast
paulson@13792
   490
apply (blast intro: Join_transient_I1)
paulson@13792
   491
done
paulson@13792
   492
paulson@7400
   493
end