src/HOL/UNITY/Guar.thy
author wenzelm
Sat Nov 04 15:24:40 2017 +0100 (21 months ago)
changeset 67003 49850a679c2c
parent 63146 f1ecba0272f9
child 67613 ce654b0e6d69
permissions -rw-r--r--
more robust sorted_entries;
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(*  Title:      HOL/UNITY/Guar.thy
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Author:     Sidi Ehmety
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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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Compatibility, weakest guarantees, etc.  and Weakest existential
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property, 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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section\<open>Guarantees Specifications\<close>
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theory Guar
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imports Comp
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begin
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instance program :: (type) order
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  by standard (auto simp add: program_less_le dest: component_antisym intro: component_trans)
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text\<open>Existential and Universal properties.  I formalize the two-program
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      case, proving equivalence with Chandy and Sanders's n-ary definitions\<close>
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definition ex_prop :: "'a program set => bool" where
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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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definition strict_ex_prop  :: "'a program set => bool" where
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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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definition uv_prop  :: "'a program set => bool" where
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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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definition strict_uv_prop  :: "'a program set => bool" where
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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\<open>Guarantees properties\<close>
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definition guar :: "['a program set, 'a program set] => 'a program set" (infixl "guarantees" 55) where
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          (*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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definition wg :: "['a program, 'a program set] => 'a program set" where
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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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definition wx :: "('a program) set => ('a program)set" where
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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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definition welldef :: "'a program set" where
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  "welldef == {F. Init F \<noteq> {}}"
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definition refines :: "['a program, 'a program, 'a program set] => bool"
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                        ("(3_ refines _ wrt _)" [10,10,10] 10) where
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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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definition iso_refines :: "['a program, 'a program, 'a program set] => bool"
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                              ("(3_ iso'_refines _ wrt _)" [10,10,10] 10) where
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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\<open>Existential Properties\<close>
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lemma ex1:
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  assumes "ex_prop X" and "finite GG"
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  shows "GG \<inter> X \<noteq> {} \<Longrightarrow> OK GG (%G. G) \<Longrightarrow> (\<Squnion>G \<in> GG. G) \<in> X"
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  apply (atomize (full))
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  using assms(2) apply induct
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   using assms(1) apply (unfold ex_prop_def)
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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\<open>Universal Properties\<close>
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lemma uv1:
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  assumes "uv_prop X"
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    and "finite GG"
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    and "GG \<subseteq> X"
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    and "OK GG (%G. G)"
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  shows "(\<Squnion>G \<in> GG. G) \<in> X"
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  using assms(2-)
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  apply induct
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   using assms(1)
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   apply (unfold uv_prop_def)
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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\<open>Guarantees\<close>
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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\<open>Distributive Laws.  Re-Orient to Perform Miniscoping\<close>
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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\<open>Guarantees: Additional Laws (by lcp)\<close>
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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\<open>Guarantees Laws for Breaking Down the Program (by lcp)\<close>
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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 simp add: 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" for PP RR 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" for PP RR 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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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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lemma wg_guarantees: "F\<in> ((wg F Y) guarantees Y)"
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by (unfold wg_def guar_def, blast)
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lemma wg_equiv: "(H \<in> wg F X) = (F component_of H --> H \<in> X)"
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by (simp add: guarantees_equiv wg_def, blast)
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   401
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lemma component_of_wg: "F component_of H ==> (H \<in> wg F X) = (H \<in> X)"
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   403
by (simp add: wg_equiv)
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   404
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   405
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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   412
apply (rule_tac x = "\<Squnion>F \<in> (FF-{F}) . F" in exI)
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   413
apply (auto intro: JN_Join_diff dest: ok_sym simp add: OK_iff_ok)
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   414
done
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   415
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   416
lemma wg_ex_prop: "ex_prop X ==> (F \<in> X) = (\<forall>H. H \<in> wg F X)"
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apply (simp (no_asm_use) add: ex_prop_equiv wg_equiv)
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   418
apply blast
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   419
done
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   420
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   421
(** From Charpentier and Chandy "Theorems About Composition" **)
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(* Proposition 2 *)
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   423
lemma wx_subset: "(wx X)<=X"
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   424
by (unfold wx_def, auto)
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   425
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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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apply force 
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   429
done
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   430
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   431
lemma wx_weakest: "\<forall>Z. Z<= X --> ex_prop Z --> Z \<subseteq> wx X"
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by (auto simp add: wx_def)
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   433
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   434
(* Proposition 6 *)
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   435
lemma wx'_ex_prop: "ex_prop({F. \<forall>G. F ok G --> F\<squnion>G \<in> X})"
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   436
apply (unfold ex_prop_def, safe)
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   437
 apply (drule_tac x = "G\<squnion>Ga" in spec)
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   438
 apply (force simp add: Join_assoc)
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   439
apply (drule_tac x = "F\<squnion>Ga" in spec)
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   440
apply (simp add: ok_commute  Join_ac) 
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   441
done
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   442
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   443
text\<open>Equivalence with the other definition of wx\<close>
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   444
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   445
lemma wx_equiv: "wx X = {F. \<forall>G. F ok G --> (F\<squnion>G) \<in> X}"
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   446
apply (unfold wx_def, safe)
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   447
 apply (simp add: ex_prop_def, blast) 
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   448
apply (simp (no_asm))
paulson@13819
   449
apply (rule_tac x = "{F. \<forall>G. F ok G --> F\<squnion>G \<in> X}" in exI, safe)
paulson@13792
   450
apply (rule_tac [2] wx'_ex_prop)
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   451
apply (drule_tac x = SKIP in spec)+
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   452
apply auto 
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   453
done
paulson@13792
   454
paulson@13792
   455
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   456
text\<open>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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   458
 by equivalence\<close>
paulson@13792
   459
   
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   460
(* Proposition 12 *)
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   461
(* Main result of the paper *)
paulson@14112
   462
lemma guarantees_wx_eq: "(X guarantees Y) = wx(-X \<union> Y)"
paulson@14112
   463
by (simp add: guar_def wx_equiv)
paulson@13792
   464
paulson@13792
   465
paulson@13792
   466
(* Rules given in section 7 of Chandy and Sander's
paulson@13792
   467
    Reasoning About Program composition paper *)
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   468
lemma stable_guarantees_Always:
paulson@14112
   469
     "Init F \<subseteq> A ==> F \<in> (stable A) guarantees (Always A)"
paulson@13792
   470
apply (rule guaranteesI)
paulson@14112
   471
apply (simp add: Join_commute)
paulson@13792
   472
apply (rule stable_Join_Always1)
wenzelm@44871
   473
 apply (simp_all add: invariant_def)
paulson@13792
   474
done
paulson@13792
   475
paulson@13792
   476
lemma constrains_guarantees_leadsTo:
paulson@13805
   477
     "F \<in> transient A ==> F \<in> (A co A \<union> B) guarantees (A leadsTo (B-A))"
paulson@13792
   478
apply (rule guaranteesI)
paulson@13792
   479
apply (rule leadsTo_Basis')
paulson@14112
   480
 apply (drule constrains_weaken_R)
paulson@14112
   481
  prefer 2 apply assumption
paulson@14112
   482
 apply blast
paulson@13792
   483
apply (blast intro: Join_transient_I1)
paulson@13792
   484
done
paulson@13792
   485
paulson@7400
   486
end