src/ZF/UNITY/ClientImpl.thy
author wenzelm
Sun Oct 07 15:49:25 2007 +0200 (2007-10-07)
changeset 24892 c663e675e177
parent 24051 896fb015079c
child 24893 b8ef7afe3a6b
permissions -rw-r--r--
replaced some 'translations' by 'abbreviation';
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(*  Title:      ZF/UNITY/ClientImpl.thy
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    ID:         $Id$
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    Author:     Sidi O Ehmety, Cambridge University Computer Laboratory
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    Copyright   2002  University of Cambridge
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Distributed Resource Management System:  Client Implementation
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*)
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theory ClientImpl imports AllocBase Guar begin
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abbreviation "ask == Var(Nil)" (* input history:  tokens requested *)
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abbreviation "giv == Var([0])" (* output history: tokens granted *)
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abbreviation "rel == Var([1])" (* input history: tokens released *)
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abbreviation "tok == Var([2])" (* the number of available tokens *)
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axioms
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  type_assumes:
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  "type_of(ask) = list(tokbag) & type_of(giv) = list(tokbag) & 
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   type_of(rel) = list(tokbag) & type_of(tok) = nat"
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  default_val_assumes:
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  "default_val(ask) = Nil & default_val(giv)  = Nil & 
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   default_val(rel)  = Nil & default_val(tok)  = 0"
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(*Array indexing is translated to list indexing as A[n] == nth(n-1,A). *)
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constdefs
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 (** Release some client_tokens **)
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  client_rel_act ::i
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    "client_rel_act ==
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     {<s,t> \<in> state*state.
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      \<exists>nrel \<in> nat. nrel = length(s`rel) &
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                   t = s(rel:=(s`rel)@[nth(nrel, s`giv)]) &
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                   nrel < length(s`giv) &
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                   nth(nrel, s`ask) \<le> nth(nrel, s`giv)}"
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  (** Choose a new token requirement **)
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  (** Including t=s suppresses fairness, allowing the non-trivial part
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      of the action to be ignored **)
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  client_tok_act :: i
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 "client_tok_act == {<s,t> \<in> state*state. t=s |
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		     t = s(tok:=succ(s`tok mod NbT))}"
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  client_ask_act :: i
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  "client_ask_act == {<s,t> \<in> state*state. t=s | (t=s(ask:=s`ask@[s`tok]))}"
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  client_prog :: i
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  "client_prog ==
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   mk_program({s \<in> state. s`tok \<le> NbT & s`giv = Nil &
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	               s`ask = Nil & s`rel = Nil},
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                    {client_rel_act, client_tok_act, client_ask_act},
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                   \<Union>G \<in> preserves(lift(rel)) Int
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			 preserves(lift(ask)) Int
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	                 preserves(lift(tok)).  Acts(G))"
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declare type_assumes [simp] default_val_assumes [simp]
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(* This part should be automated *)
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lemma ask_value_type [simp,TC]: "s \<in> state ==> s`ask \<in> list(nat)"
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apply (unfold state_def)
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apply (drule_tac a = ask in apply_type, auto)
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done
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lemma giv_value_type [simp,TC]: "s \<in> state ==> s`giv \<in> list(nat)"
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apply (unfold state_def)
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apply (drule_tac a = giv in apply_type, auto)
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done
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lemma rel_value_type [simp,TC]: "s \<in> state ==> s`rel \<in> list(nat)"
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apply (unfold state_def)
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apply (drule_tac a = rel in apply_type, auto)
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done
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lemma tok_value_type [simp,TC]: "s \<in> state ==> s`tok \<in> nat"
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apply (unfold state_def)
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apply (drule_tac a = tok in apply_type, auto)
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done
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(** The Client Program **)
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lemma client_type [simp,TC]: "client_prog \<in> program"
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apply (unfold client_prog_def)
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apply (simp (no_asm))
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done
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declare client_prog_def [THEN def_prg_Init, simp]
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declare client_prog_def [THEN def_prg_AllowedActs, simp]
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declare client_prog_def [program]
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declare  client_rel_act_def [THEN def_act_simp, simp]
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declare  client_tok_act_def [THEN def_act_simp, simp]
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declare  client_ask_act_def [THEN def_act_simp, simp]
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lemma client_prog_ok_iff:
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  "\<forall>G \<in> program. (client_prog ok G) <->  
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   (G \<in> preserves(lift(rel)) & G \<in> preserves(lift(ask)) &  
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    G \<in> preserves(lift(tok)) &  client_prog \<in> Allowed(G))"
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by (auto simp add: ok_iff_Allowed client_prog_def [THEN def_prg_Allowed])
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lemma client_prog_preserves:
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    "client_prog:(\<Inter>x \<in> var-{ask, rel, tok}. preserves(lift(x)))"
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apply (rule Inter_var_DiffI, force)
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apply (rule ballI)
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apply (rule preservesI, safety, auto)
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done
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lemma preserves_lift_imp_stable:
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     "G \<in> preserves(lift(ff)) ==> G \<in> stable({s \<in> state. P(s`ff)})";
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apply (drule preserves_imp_stable)
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apply (simp add: lift_def) 
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done
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lemma preserves_imp_prefix:
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     "G \<in> preserves(lift(ff)) 
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      ==> G \<in> stable({s \<in> state. \<langle>k, s`ff\<rangle> \<in> prefix(nat)})";
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by (erule preserves_lift_imp_stable) 
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(*Safety property 1: ask, rel are increasing: (24) *)
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lemma client_prog_Increasing_ask_rel: 
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"client_prog: program guarantees Incr(lift(ask)) Int Incr(lift(rel))"
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apply (unfold guar_def)
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apply (auto intro!: increasing_imp_Increasing 
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            simp add: client_prog_ok_iff increasing_def preserves_imp_prefix)
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apply (safety, force, force)+
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done
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declare nth_append [simp] append_one_prefix [simp]
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lemma NbT_pos2: "0<NbT"
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apply (cut_tac NbT_pos)
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apply (rule Ord_0_lt, auto)
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done
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(*Safety property 2: the client never requests too many tokens.
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With no Substitution Axiom, we must prove the two invariants simultaneously. *)
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lemma ask_Bounded_lemma: 
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"[| client_prog ok G; G \<in> program |] 
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      ==> client_prog \<squnion> G \<in>    
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              Always({s \<in> state. s`tok \<le> NbT}  Int   
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                      {s \<in> state. \<forall>elt \<in> set_of_list(s`ask). elt \<le> NbT})"
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apply (rotate_tac -1)
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apply (auto simp add: client_prog_ok_iff)
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apply (rule invariantI [THEN stable_Join_Always2], force) 
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 prefer 2
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 apply (fast intro: stable_Int preserves_lift_imp_stable, safety)
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apply (auto dest: ActsD)
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apply (cut_tac NbT_pos)
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apply (rule NbT_pos2 [THEN mod_less_divisor])
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apply (auto dest: ActsD preserves_imp_eq simp add: set_of_list_append)
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done
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(* Export version, with no mention of tok in the postcondition, but
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  unfortunately tok must be declared local.*)
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lemma client_prog_ask_Bounded: 
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    "client_prog \<in> program guarantees  
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                   Always({s \<in> state. \<forall>elt \<in> set_of_list(s`ask). elt \<le> NbT})"
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apply (rule guaranteesI)
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apply (erule ask_Bounded_lemma [THEN Always_weaken], auto)
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done
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(*** Towards proving the liveness property ***)
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lemma client_prog_stable_rel_le_giv: 
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    "client_prog \<in> stable({s \<in> state. <s`rel, s`giv> \<in> prefix(nat)})"
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by (safety, auto)
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lemma client_prog_Join_Stable_rel_le_giv: 
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"[| client_prog \<squnion> G \<in> Incr(lift(giv)); G \<in> preserves(lift(rel)) |]  
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    ==> client_prog \<squnion> G \<in> Stable({s \<in> state. <s`rel, s`giv> \<in> prefix(nat)})"
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apply (rule client_prog_stable_rel_le_giv [THEN Increasing_preserves_Stable])
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apply (auto simp add: lift_def)
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done
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lemma client_prog_Join_Always_rel_le_giv:
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     "[| client_prog \<squnion> G \<in> Incr(lift(giv)); G \<in> preserves(lift(rel)) |]  
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    ==> client_prog \<squnion> G  \<in> Always({s \<in> state. <s`rel, s`giv> \<in> prefix(nat)})"
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by (force intro!: AlwaysI client_prog_Join_Stable_rel_le_giv)
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lemma def_act_eq:
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     "A == {<s, t> \<in> state*state. P(s, t)} ==> A={<s, t> \<in> state*state. P(s, t)}"
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by auto
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lemma act_subset: "A={<s,t> \<in> state*state. P(s, t)} ==> A<=state*state"
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by auto
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lemma transient_lemma: 
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"client_prog \<in>  
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  transient({s \<in> state. s`rel = k & <k, h> \<in> strict_prefix(nat)  
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   & <h, s`giv> \<in> prefix(nat) & h pfixGe s`ask})"
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apply (rule_tac act = client_rel_act in transientI)
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apply (simp (no_asm) add: client_prog_def [THEN def_prg_Acts])
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apply (simp (no_asm) add: client_rel_act_def [THEN def_act_eq, THEN act_subset])
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apply (auto simp add: client_prog_def [THEN def_prg_Acts] domain_def)
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apply (rule ReplaceI)
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apply (rule_tac x = "x (rel:= x`rel @ [nth (length (x`rel), x`giv) ]) " in exI)
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apply (auto intro!: state_update_type app_type length_type nth_type, auto)
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apply (blast intro: lt_trans2 prefix_length_le strict_prefix_length_lt)
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apply (blast intro: lt_trans2 prefix_length_le strict_prefix_length_lt)
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apply (simp (no_asm_use) add: gen_prefix_iff_nth)
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apply (subgoal_tac "h \<in> list(nat)")
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 apply (simp_all (no_asm_simp) add: prefix_type [THEN subsetD, THEN SigmaD1])
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apply (auto simp add: prefix_def Ge_def)
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apply (drule strict_prefix_length_lt)
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apply (drule_tac x = "length (x`rel) " in spec)
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apply auto
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apply (simp (no_asm_use) add: gen_prefix_iff_nth)
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apply (auto simp add: id_def lam_def)
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done
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lemma strict_prefix_is_prefix: 
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    "<xs, ys> \<in> strict_prefix(A) <->  <xs, ys> \<in> prefix(A) & xs\<noteq>ys"
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apply (unfold strict_prefix_def id_def lam_def)
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apply (auto dest: prefix_type [THEN subsetD])
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done
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lemma induct_lemma: 
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"[| client_prog \<squnion> G \<in> Incr(lift(giv)); client_prog ok G; G \<in> program |]  
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  ==> client_prog \<squnion> G \<in>  
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  {s \<in> state. s`rel = k & <k,h> \<in> strict_prefix(nat)  
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   & <h, s`giv> \<in> prefix(nat) & h pfixGe s`ask}   
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        LeadsTo {s \<in> state. <k, s`rel> \<in> strict_prefix(nat)  
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                          & <s`rel, s`giv> \<in> prefix(nat) &  
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                                  <h, s`giv> \<in> prefix(nat) &  
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                h pfixGe s`ask}"
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apply (rule single_LeadsTo_I)
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 prefer 2 apply simp
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apply (frule client_prog_Increasing_ask_rel [THEN guaranteesD])
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apply (rotate_tac [3] 2)
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apply (auto simp add: client_prog_ok_iff)
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apply (rule transient_lemma [THEN Join_transient_I1, THEN transient_imp_leadsTo, THEN leadsTo_imp_LeadsTo, THEN PSP_Stable, THEN LeadsTo_weaken])
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apply (rule Stable_Int [THEN Stable_Int, THEN Stable_Int])
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apply (erule_tac f = "lift (giv) " and a = "s`giv" in Increasing_imp_Stable)
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apply (simp (no_asm_simp))
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apply (erule_tac f = "lift (ask) " and a = "s`ask" in Increasing_imp_Stable)
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apply (simp (no_asm_simp))
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apply (erule_tac f = "lift (rel) " and a = "s`rel" in Increasing_imp_Stable)
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apply (simp (no_asm_simp))
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apply (erule client_prog_Join_Stable_rel_le_giv, blast, simp_all)
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 prefer 2
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 apply (blast intro: sym strict_prefix_is_prefix [THEN iffD2] prefix_trans prefix_imp_pfixGe pfixGe_trans)
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apply (auto intro: strict_prefix_is_prefix [THEN iffD1, THEN conjunct1] 
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                   prefix_trans)
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done
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lemma rel_progress_lemma: 
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"[| client_prog \<squnion> G  \<in> Incr(lift(giv)); client_prog ok G; G \<in> program |]  
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  ==> client_prog \<squnion> G  \<in>  
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     {s \<in> state. <s`rel, h> \<in> strict_prefix(nat)  
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           & <h, s`giv> \<in> prefix(nat) & h pfixGe s`ask}   
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                      LeadsTo {s \<in> state. <h, s`rel> \<in> prefix(nat)}"
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apply (rule_tac f = "\<lambda>x \<in> state. length(h) #- length(x`rel)" 
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       in LessThan_induct)
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apply (auto simp add: vimage_def)
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 prefer 2 apply (force simp add: lam_def) 
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apply (rule single_LeadsTo_I)
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 prefer 2 apply simp 
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apply (subgoal_tac "h \<in> list(nat)")
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 prefer 2 apply (blast dest: prefix_type [THEN subsetD]) 
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apply (rule induct_lemma [THEN LeadsTo_weaken])
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    apply (simp add: length_type lam_def)
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apply (auto intro: strict_prefix_is_prefix [THEN iffD2]
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            dest: common_prefix_linear  prefix_type [THEN subsetD])
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apply (erule swap)
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apply (rule imageI)
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 apply (force dest!: simp add: lam_def) 
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apply (simp add: length_type lam_def, clarify) 
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apply (drule strict_prefix_length_lt)+
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apply (drule less_imp_succ_add, simp)+
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apply clarify 
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apply simp 
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apply (erule diff_le_self [THEN ltD])
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done
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lemma progress_lemma: 
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"[| client_prog \<squnion> G \<in> Incr(lift(giv)); client_prog ok G; G \<in> program |] 
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 ==> client_prog \<squnion> G
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       \<in> {s \<in> state. <h, s`giv> \<in> prefix(nat) & h pfixGe s`ask}   
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         LeadsTo  {s \<in> state. <h, s`rel> \<in> prefix(nat)}"
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apply (rule client_prog_Join_Always_rel_le_giv [THEN Always_LeadsToI], 
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       assumption)
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apply (force simp add: client_prog_ok_iff)
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apply (rule LeadsTo_weaken_L) 
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apply (rule LeadsTo_Un [OF rel_progress_lemma 
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                           subset_refl [THEN subset_imp_LeadsTo]])
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apply (auto intro: strict_prefix_is_prefix [THEN iffD2]
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            dest: common_prefix_linear prefix_type [THEN subsetD])
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done
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(*Progress property: all tokens that are given will be released*)
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lemma client_prog_progress: 
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"client_prog \<in> Incr(lift(giv))  guarantees   
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      (\<Inter>h \<in> list(nat). {s \<in> state. <h, s`giv> \<in> prefix(nat) & 
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              h pfixGe s`ask} LeadsTo {s \<in> state. <h, s`rel> \<in> prefix(nat)})"
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apply (rule guaranteesI)
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apply (blast intro: progress_lemma, auto)
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done
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lemma client_prog_Allowed:
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     "Allowed(client_prog) =  
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      preserves(lift(rel)) Int preserves(lift(ask)) Int preserves(lift(tok))"
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apply (cut_tac v = "lift (ask)" in preserves_type)
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apply (auto simp add: Allowed_def client_prog_def [THEN def_prg_Allowed] 
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                      cons_Int_distrib safety_prop_Acts_iff)
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done
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paulson@14072
   311
end