(* Title: HOL/UNITY/Guar.thy
ID: $Id$
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1999 University of Cambridge
From Chandy and Sanders, "Reasoning About Program Composition",
Technical Report 2000-003, University of Florida, 2000.
Revised by Sidi Ehmety on January 2001
Added: Compatibility, weakest guarantees, etc.
and Weakest existential property,
from Charpentier and Chandy "Theorems about Composition",
Fifth International Conference on Mathematics of Program, 2000.
*)
header{*Guarantees Specifications*}
theory Guar = Comp:
instance program :: (type) order
by (intro_classes,
(assumption | rule component_refl component_trans component_antisym
program_less_le)+)
constdefs
(*Existential and Universal properties. I formalize the two-program
case, proving equivalence with Chandy and Sanders's n-ary definitions*)
ex_prop :: "'a program set => bool"
"ex_prop X == \<forall>F G. F ok G -->F \<in> X | G \<in> X --> (F Join G) \<in> X"
strict_ex_prop :: "'a program set => bool"
"strict_ex_prop X == \<forall>F G. F ok G --> (F \<in> X | G \<in> X) = (F Join G \<in> X)"
uv_prop :: "'a program set => bool"
"uv_prop X == SKIP \<in> X & (\<forall>F G. F ok G --> F \<in> X & G \<in> X --> (F Join G) \<in> X)"
strict_uv_prop :: "'a program set => bool"
"strict_uv_prop X ==
SKIP \<in> X & (\<forall>F G. F ok G --> (F \<in> X & G \<in> X) = (F Join G \<in> X))"
guar :: "['a program set, 'a program set] => 'a program set"
(infixl "guarantees" 55) (*higher than membership, lower than Co*)
"X guarantees Y == {F. \<forall>G. F ok G --> F Join G \<in> X --> F Join G \<in> Y}"
(* Weakest guarantees *)
wg :: "['a program, 'a program set] => 'a program set"
"wg F Y == Union({X. F \<in> X guarantees Y})"
(* Weakest existential property stronger than X *)
wx :: "('a program) set => ('a program)set"
"wx X == Union({Y. Y \<subseteq> X & ex_prop Y})"
(*Ill-defined programs can arise through "Join"*)
welldef :: "'a program set"
"welldef == {F. Init F \<noteq> {}}"
refines :: "['a program, 'a program, 'a program set] => bool"
("(3_ refines _ wrt _)" [10,10,10] 10)
"G refines F wrt X ==
\<forall>H. (F ok H & G ok H & F Join H \<in> welldef \<inter> X) -->
(G Join H \<in> welldef \<inter> X)"
iso_refines :: "['a program, 'a program, 'a program set] => bool"
("(3_ iso'_refines _ wrt _)" [10,10,10] 10)
"G iso_refines F wrt X ==
F \<in> welldef \<inter> X --> G \<in> welldef \<inter> X"
lemma OK_insert_iff:
"(OK (insert i I) F) =
(if i \<in> I then OK I F else OK I F & (F i ok JOIN I F))"
by (auto intro: ok_sym simp add: OK_iff_ok)
(*** existential properties ***)
lemma ex1 [rule_format]:
"[| ex_prop X; finite GG |] ==>
GG \<inter> X \<noteq> {}--> OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X"
apply (unfold ex_prop_def)
apply (erule finite_induct)
apply (auto simp add: OK_insert_iff Int_insert_left)
done
lemma ex2:
"\<forall>GG. finite GG & GG \<inter> X \<noteq> {} --> OK GG (%G. G) -->(\<Squnion>G \<in> GG. G):X
==> ex_prop X"
apply (unfold ex_prop_def, clarify)
apply (drule_tac x = "{F,G}" in spec)
apply (auto dest: ok_sym simp add: OK_iff_ok)
done
(*Chandy & Sanders take this as a definition*)
lemma ex_prop_finite:
"ex_prop X =
(\<forall>GG. finite GG & GG \<inter> X \<noteq> {} & OK GG (%G. G)--> (\<Squnion>G \<in> GG. G) \<in> X)"
by (blast intro: ex1 ex2)
(*Their "equivalent definition" given at the end of section 3*)
lemma ex_prop_equiv:
"ex_prop X = (\<forall>G. G \<in> X = (\<forall>H. (G component_of H) --> H \<in> X))"
apply auto
apply (unfold ex_prop_def component_of_def, safe)
apply blast
apply blast
apply (subst Join_commute)
apply (drule ok_sym, blast)
done
(*** universal properties ***)
lemma uv1 [rule_format]:
"[| uv_prop X; finite GG |]
==> GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X"
apply (unfold uv_prop_def)
apply (erule finite_induct)
apply (auto simp add: Int_insert_left OK_insert_iff)
done
lemma uv2:
"\<forall>GG. finite GG & GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G) \<in> X
==> uv_prop X"
apply (unfold uv_prop_def)
apply (rule conjI)
apply (drule_tac x = "{}" in spec)
prefer 2
apply clarify
apply (drule_tac x = "{F,G}" in spec)
apply (auto dest: ok_sym simp add: OK_iff_ok)
done
(*Chandy & Sanders take this as a definition*)
lemma uv_prop_finite:
"uv_prop X =
(\<forall>GG. finite GG & GG \<subseteq> X & OK GG (%G. G) --> (\<Squnion>G \<in> GG. G): X)"
by (blast intro: uv1 uv2)
(*** guarantees ***)
lemma guaranteesI:
"(!!G. [| F ok G; F Join G \<in> X |] ==> F Join G \<in> Y)
==> F \<in> X guarantees Y"
by (simp add: guar_def component_def)
lemma guaranteesD:
"[| F \<in> X guarantees Y; F ok G; F Join G \<in> X |]
==> F Join G \<in> Y"
by (unfold guar_def component_def, blast)
(*This version of guaranteesD matches more easily in the conclusion
The major premise can no longer be F \<subseteq> H since we need to reason about G*)
lemma component_guaranteesD:
"[| F \<in> X guarantees Y; F Join G = H; H \<in> X; F ok G |]
==> H \<in> Y"
by (unfold guar_def, blast)
lemma guarantees_weaken:
"[| F \<in> X guarantees X'; Y \<subseteq> X; X' \<subseteq> Y' |] ==> F \<in> Y guarantees Y'"
by (unfold guar_def, blast)
lemma subset_imp_guarantees_UNIV: "X \<subseteq> Y ==> X guarantees Y = UNIV"
by (unfold guar_def, blast)
(*Equivalent to subset_imp_guarantees_UNIV but more intuitive*)
lemma subset_imp_guarantees: "X \<subseteq> Y ==> F \<in> X guarantees Y"
by (unfold guar_def, blast)
(*Remark at end of section 4.1 *)
lemma ex_prop_imp: "ex_prop Y ==> (Y = UNIV guarantees Y)"
apply (simp (no_asm_use) add: guar_def ex_prop_equiv)
apply safe
apply (drule_tac x = x in spec)
apply (drule_tac [2] x = x in spec)
apply (drule_tac [2] sym)
apply (auto simp add: component_of_def)
done
lemma guarantees_imp: "(Y = UNIV guarantees Y) ==> ex_prop(Y)"
apply (simp (no_asm_use) add: guar_def ex_prop_equiv)
apply safe
apply (auto simp add: component_of_def dest: sym)
done
lemma ex_prop_equiv2: "(ex_prop Y) = (Y = UNIV guarantees Y)"
apply (rule iffI)
apply (rule ex_prop_imp)
apply (auto simp add: guarantees_imp)
done
(** Distributive laws. Re-orient to perform miniscoping **)
lemma guarantees_UN_left:
"(\<Union>i \<in> I. X i) guarantees Y = (\<Inter>i \<in> I. X i guarantees Y)"
by (unfold guar_def, blast)
lemma guarantees_Un_left:
"(X \<union> Y) guarantees Z = (X guarantees Z) \<inter> (Y guarantees Z)"
by (unfold guar_def, blast)
lemma guarantees_INT_right:
"X guarantees (\<Inter>i \<in> I. Y i) = (\<Inter>i \<in> I. X guarantees Y i)"
by (unfold guar_def, blast)
lemma guarantees_Int_right:
"Z guarantees (X \<inter> Y) = (Z guarantees X) \<inter> (Z guarantees Y)"
by (unfold guar_def, blast)
lemma guarantees_Int_right_I:
"[| F \<in> Z guarantees X; F \<in> Z guarantees Y |]
==> F \<in> Z guarantees (X \<inter> Y)"
by (simp add: guarantees_Int_right)
lemma guarantees_INT_right_iff:
"(F \<in> X guarantees (INTER I Y)) = (\<forall>i\<in>I. F \<in> X guarantees (Y i))"
by (simp add: guarantees_INT_right)
lemma shunting: "(X guarantees Y) = (UNIV guarantees (-X \<union> Y))"
by (unfold guar_def, blast)
lemma contrapositive: "(X guarantees Y) = -Y guarantees -X"
by (unfold guar_def, blast)
(** The following two can be expressed using intersection and subset, which
is more faithful to the text but looks cryptic.
**)
lemma combining1:
"[| F \<in> V guarantees X; F \<in> (X \<inter> Y) guarantees Z |]
==> F \<in> (V \<inter> Y) guarantees Z"
by (unfold guar_def, blast)
lemma combining2:
"[| F \<in> V guarantees (X \<union> Y); F \<in> Y guarantees Z |]
==> F \<in> V guarantees (X \<union> Z)"
by (unfold guar_def, blast)
(** The following two follow Chandy-Sanders, but the use of object-quantifiers
does not suit Isabelle... **)
(*Premise should be (!!i. i \<in> I ==> F \<in> X guarantees Y i) *)
lemma all_guarantees:
"\<forall>i\<in>I. F \<in> X guarantees (Y i) ==> F \<in> X guarantees (\<Inter>i \<in> I. Y i)"
by (unfold guar_def, blast)
(*Premises should be [| F \<in> X guarantees Y i; i \<in> I |] *)
lemma ex_guarantees:
"\<exists>i\<in>I. F \<in> X guarantees (Y i) ==> F \<in> X guarantees (\<Union>i \<in> I. Y i)"
by (unfold guar_def, blast)
(*** Additional guarantees laws, by lcp ***)
lemma guarantees_Join_Int:
"[| F \<in> U guarantees V; G \<in> X guarantees Y; F ok G |]
==> F Join G \<in> (U \<inter> X) guarantees (V \<inter> Y)"
apply (unfold guar_def)
apply (simp (no_asm))
apply safe
apply (simp add: Join_assoc)
apply (subgoal_tac "F Join G Join Ga = G Join (F Join Ga) ")
apply (simp add: ok_commute)
apply (simp (no_asm_simp) add: Join_ac)
done
lemma guarantees_Join_Un:
"[| F \<in> U guarantees V; G \<in> X guarantees Y; F ok G |]
==> F Join G \<in> (U \<union> X) guarantees (V \<union> Y)"
apply (unfold guar_def)
apply (simp (no_asm))
apply safe
apply (simp add: Join_assoc)
apply (subgoal_tac "F Join G Join Ga = G Join (F Join Ga) ")
apply (simp add: ok_commute)
apply (simp (no_asm_simp) add: Join_ac)
done
lemma guarantees_JN_INT:
"[| \<forall>i\<in>I. F i \<in> X i guarantees Y i; OK I F |]
==> (JOIN I F) \<in> (INTER I X) guarantees (INTER I Y)"
apply (unfold guar_def, auto)
apply (drule bspec, assumption)
apply (rename_tac "i")
apply (drule_tac x = "JOIN (I-{i}) F Join G" in spec)
apply (auto intro: OK_imp_ok
simp add: Join_assoc [symmetric] JN_Join_diff JN_absorb)
done
lemma guarantees_JN_UN:
"[| \<forall>i\<in>I. F i \<in> X i guarantees Y i; OK I F |]
==> (JOIN I F) \<in> (UNION I X) guarantees (UNION I Y)"
apply (unfold guar_def, auto)
apply (drule bspec, assumption)
apply (rename_tac "i")
apply (drule_tac x = "JOIN (I-{i}) F Join G" in spec)
apply (auto intro: OK_imp_ok
simp add: Join_assoc [symmetric] JN_Join_diff JN_absorb)
done
(*** guarantees laws for breaking down the program, by lcp ***)
lemma guarantees_Join_I1:
"[| F \<in> X guarantees Y; F ok G |] ==> F Join G \<in> X guarantees Y"
apply (unfold guar_def)
apply (simp (no_asm))
apply safe
apply (simp add: Join_assoc)
done
lemma guarantees_Join_I2:
"[| G \<in> X guarantees Y; F ok G |] ==> F Join G \<in> X guarantees Y"
apply (simp add: Join_commute [of _ G] ok_commute [of _ G])
apply (blast intro: guarantees_Join_I1)
done
lemma guarantees_JN_I:
"[| i \<in> I; F i \<in> X guarantees Y; OK I F |]
==> (\<Squnion>i \<in> I. (F i)) \<in> X guarantees Y"
apply (unfold guar_def, clarify)
apply (drule_tac x = "JOIN (I-{i}) F Join G" in spec)
apply (auto intro: OK_imp_ok simp add: JN_Join_diff JN_Join_diff Join_assoc [symmetric])
done
(*** well-definedness ***)
lemma Join_welldef_D1: "F Join G \<in> welldef ==> F \<in> welldef"
by (unfold welldef_def, auto)
lemma Join_welldef_D2: "F Join G \<in> welldef ==> G \<in> welldef"
by (unfold welldef_def, auto)
(*** refinement ***)
lemma refines_refl: "F refines F wrt X"
by (unfold refines_def, blast)
(* Goalw [refines_def]
"[| H refines G wrt X; G refines F wrt X |] ==> H refines F wrt X"
by Auto_tac
qed "refines_trans"; *)
lemma strict_ex_refine_lemma:
"strict_ex_prop X
==> (\<forall>H. F ok H & G ok H & F Join H \<in> X --> G Join H \<in> X)
= (F \<in> X --> G \<in> X)"
by (unfold strict_ex_prop_def, auto)
lemma strict_ex_refine_lemma_v:
"strict_ex_prop X
==> (\<forall>H. F ok H & G ok H & F Join H \<in> welldef & F Join H \<in> X --> G Join H \<in> X) =
(F \<in> welldef \<inter> X --> G \<in> X)"
apply (unfold strict_ex_prop_def, safe)
apply (erule_tac x = SKIP and P = "%H. ?PP H --> ?RR H" in allE)
apply (auto dest: Join_welldef_D1 Join_welldef_D2)
done
lemma ex_refinement_thm:
"[| strict_ex_prop X;
\<forall>H. F ok H & G ok H & F Join H \<in> welldef \<inter> X --> G Join H \<in> welldef |]
==> (G refines F wrt X) = (G iso_refines F wrt X)"
apply (rule_tac x = SKIP in allE, assumption)
apply (simp add: refines_def iso_refines_def strict_ex_refine_lemma_v)
done
lemma strict_uv_refine_lemma:
"strict_uv_prop X ==>
(\<forall>H. F ok H & G ok H & F Join H \<in> X --> G Join H \<in> X) = (F \<in> X --> G \<in> X)"
by (unfold strict_uv_prop_def, blast)
lemma strict_uv_refine_lemma_v:
"strict_uv_prop X
==> (\<forall>H. F ok H & G ok H & F Join H \<in> welldef & F Join H \<in> X --> G Join H \<in> X) =
(F \<in> welldef \<inter> X --> G \<in> X)"
apply (unfold strict_uv_prop_def, safe)
apply (erule_tac x = SKIP and P = "%H. ?PP H --> ?RR H" in allE)
apply (auto dest: Join_welldef_D1 Join_welldef_D2)
done
lemma uv_refinement_thm:
"[| strict_uv_prop X;
\<forall>H. F ok H & G ok H & F Join H \<in> welldef \<inter> X -->
G Join H \<in> welldef |]
==> (G refines F wrt X) = (G iso_refines F wrt X)"
apply (rule_tac x = SKIP in allE, assumption)
apply (simp add: refines_def iso_refines_def strict_uv_refine_lemma_v)
done
(* Added by Sidi Ehmety from Chandy & Sander, section 6 *)
lemma guarantees_equiv:
"(F \<in> X guarantees Y) = (\<forall>H. H \<in> X \<longrightarrow> (F component_of H \<longrightarrow> H \<in> Y))"
by (unfold guar_def component_of_def, auto)
lemma wg_weakest: "!!X. F:(X guarantees Y) ==> X \<subseteq> (wg F Y)"
by (unfold wg_def, auto)
lemma wg_guarantees: "F:((wg F Y) guarantees Y)"
by (unfold wg_def guar_def, blast)
lemma wg_equiv:
"(H \<in> wg F X) = (F component_of H --> H \<in> X)"
apply (unfold wg_def)
apply (simp (no_asm) add: guarantees_equiv)
apply (rule iffI)
apply (rule_tac [2] x = "{H}" in exI)
apply (blast+)
done
lemma component_of_wg: "F component_of H ==> (H \<in> wg F X) = (H \<in> X)"
by (simp add: wg_equiv)
lemma wg_finite:
"\<forall>FF. finite FF & FF \<inter> X \<noteq> {} --> OK FF (%F. F)
--> (\<forall>F\<in>FF. ((\<Squnion>F \<in> FF. F): wg F X) = ((\<Squnion>F \<in> FF. F):X))"
apply clarify
apply (subgoal_tac "F component_of (\<Squnion>F \<in> FF. F) ")
apply (drule_tac X = X in component_of_wg, simp)
apply (simp add: component_of_def)
apply (rule_tac x = "\<Squnion>F \<in> (FF-{F}) . F" in exI)
apply (auto intro: JN_Join_diff dest: ok_sym simp add: OK_iff_ok)
done
lemma wg_ex_prop: "ex_prop X ==> (F \<in> X) = (\<forall>H. H \<in> wg F X)"
apply (simp (no_asm_use) add: ex_prop_equiv wg_equiv)
apply blast
done
(** From Charpentier and Chandy "Theorems About Composition" **)
(* Proposition 2 *)
lemma wx_subset: "(wx X)<=X"
by (unfold wx_def, auto)
lemma wx_ex_prop: "ex_prop (wx X)"
apply (unfold wx_def)
apply (simp (no_asm) add: ex_prop_equiv)
apply safe
apply blast
apply auto
done
lemma wx_weakest: "\<forall>Z. Z<= X --> ex_prop Z --> Z \<subseteq> wx X"
by (unfold wx_def, auto)
(* Proposition 6 *)
lemma wx'_ex_prop: "ex_prop({F. \<forall>G. F ok G --> F Join G \<in> X})"
apply (unfold ex_prop_def, safe)
apply (drule_tac x = "G Join Ga" in spec)
apply (force simp add: ok_Join_iff1 Join_assoc)
apply (drule_tac x = "F Join Ga" in spec)
apply (simp (no_asm_use) add: ok_Join_iff1)
apply safe
apply (simp (no_asm_simp) add: ok_commute)
apply (subgoal_tac "F Join G = G Join F")
apply (simp (no_asm_simp) add: Join_assoc)
apply (simp (no_asm) add: Join_commute)
done
(* Equivalence with the other definition of wx *)
lemma wx_equiv:
"wx X = {F. \<forall>G. F ok G --> (F Join G):X}"
apply (unfold wx_def, safe)
apply (simp (no_asm_use) add: ex_prop_def)
apply (drule_tac x = x in spec)
apply (drule_tac x = G in spec)
apply (frule_tac c = "x Join G" in subsetD, safe)
apply (simp (no_asm))
apply (rule_tac x = "{F. \<forall>G. F ok G --> F Join G \<in> X}" in exI, safe)
apply (rule_tac [2] wx'_ex_prop)
apply (rotate_tac 1)
apply (drule_tac x = SKIP in spec, auto)
done
(* Propositions 7 to 11 are about this second definition of wx. And
they are the same as the ones proved for the first definition of wx by equivalence *)
(* Proposition 12 *)
(* Main result of the paper *)
lemma guarantees_wx_eq:
"(X guarantees Y) = wx(-X \<union> Y)"
apply (unfold guar_def)
apply (simp (no_asm) add: wx_equiv)
done
(* {* Corollary, but this result has already been proved elsewhere *}
"ex_prop(X guarantees Y)"
by (simp_tac (simpset() addsimps [guar_wx_iff, wx_ex_prop]) 1);
qed "guarantees_ex_prop";
*)
(* Rules given in section 7 of Chandy and Sander's
Reasoning About Program composition paper *)
lemma stable_guarantees_Always:
"Init F \<subseteq> A ==> F:(stable A) guarantees (Always A)"
apply (rule guaranteesI)
apply (simp (no_asm) add: Join_commute)
apply (rule stable_Join_Always1)
apply (simp_all add: invariant_def Join_stable)
done
(* To be moved to WFair.ML *)
lemma leadsTo_Basis': "[| F \<in> A co A \<union> B; F \<in> transient A |] ==> F \<in> A leadsTo B"
apply (drule_tac B = "A-B" in constrains_weaken_L)
apply (drule_tac [2] B = "A-B" in transient_strengthen)
apply (rule_tac [3] ensuresI [THEN leadsTo_Basis])
apply (blast+)
done
lemma constrains_guarantees_leadsTo:
"F \<in> transient A ==> F \<in> (A co A \<union> B) guarantees (A leadsTo (B-A))"
apply (rule guaranteesI)
apply (rule leadsTo_Basis')
apply (drule constrains_weaken_R)
prefer 2 apply assumption
apply blast
apply (blast intro: Join_transient_I1)
done
end