Theory TLA

(*  Title:      HOL/TLA/TLA.thy
    Author:     Stephan Merz
    Copyright:  1998 University of Munich
*)

section ‹The temporal level of TLA›

theory TLA
imports Init
begin

consts
  (** abstract syntax **)
  Box        :: "('w::world) form ⇒ temporal"
  Dmd        :: "('w::world) form ⇒ temporal"
  leadsto    :: "['w::world form, 'v::world form] ⇒ temporal"
  Stable     :: "stpred ⇒ temporal"
  WF         :: "[action, 'a stfun] ⇒ temporal"
  SF         :: "[action, 'a stfun] ⇒ temporal"

  (* Quantification over (flexible) state variables *)
  EEx        :: "('a stfun ⇒ temporal) ⇒ temporal"       (binder "Eex " 10)
  AAll       :: "('a stfun ⇒ temporal) ⇒ temporal"       (binder "Aall " 10)

  (** concrete syntax **)
syntax
  "_Box"     :: "lift ⇒ lift"                        ("(□_)" [40] 40)
  "_Dmd"     :: "lift ⇒ lift"                        ("(◇_)" [40] 40)
  "_leadsto" :: "[lift,lift] ⇒ lift"                 ("(_ ↝ _)" [23,22] 22)
  "_stable"  :: "lift ⇒ lift"                        ("(stable/ _)")
  "_WF"      :: "[lift,lift] ⇒ lift"                 ("(WF'(_')'_(_))" [0,60] 55)
  "_SF"      :: "[lift,lift] ⇒ lift"                 ("(SF'(_')'_(_))" [0,60] 55)

  "_EEx"     :: "[idts, lift] ⇒ lift"                ("(3∃∃ _./ _)" [0,10] 10)
  "_AAll"    :: "[idts, lift] ⇒ lift"                ("(3∀∀ _./ _)" [0,10] 10)

translations
  "_Box"      ==   "CONST Box"
  "_Dmd"      ==   "CONST Dmd"
  "_leadsto"  ==   "CONST leadsto"
  "_stable"   ==   "CONST Stable"
  "_WF"       ==   "CONST WF"
  "_SF"       ==   "CONST SF"
  "_EEx v A"  ==   "Eex v. A"
  "_AAll v A" ==   "Aall v. A"

  "sigma ⊨ □F"         <= "_Box F sigma"
  "sigma ⊨ ◇F"         <= "_Dmd F sigma"
  "sigma ⊨ F ↝ G"      <= "_leadsto F G sigma"
  "sigma ⊨ stable P"    <= "_stable P sigma"
  "sigma ⊨ WF(A)_v"     <= "_WF A v sigma"
  "sigma ⊨ SF(A)_v"     <= "_SF A v sigma"
  "sigma ⊨ ∃∃x. F"    <= "_EEx x F sigma"
  "sigma ⊨ ∀∀x. F"    <= "_AAll x F sigma"

axiomatization where
  (* Definitions of derived operators *)
  dmd_def:      "⋀F. TEMP ◇F  ==  TEMP ¬□¬F"

axiomatization where
  boxInit:      "⋀F. TEMP □F  ==  TEMP □Init F" and
  leadsto_def:  "⋀F G. TEMP F ↝ G  ==  TEMP □(Init F ⟶ ◇G)" and
  stable_def:   "⋀P. TEMP stable P  ==  TEMP □($P ⟶ P$)" and
  WF_def:       "TEMP WF(A)_v  ==  TEMP ◇□ Enabled(<A>_v) ⟶ □◇<A>_v" and
  SF_def:       "TEMP SF(A)_v  ==  TEMP □◇ Enabled(<A>_v) ⟶ □◇<A>_v" and
  aall_def:     "TEMP (∀∀x. F x)  ==  TEMP ¬ (∃∃x. ¬ F x)"

axiomatization where
(* Base axioms for raw TLA. *)
  normalT:    "⋀F G. ⊢ □(F ⟶ G) ⟶ (□F ⟶ □G)" and    (* polymorphic *)
  reflT:      "⋀F. ⊢ □F ⟶ F" and         (* F::temporal *)
  transT:     "⋀F. ⊢ □F ⟶ □□F" and     (* polymorphic *)
  linT:       "⋀F G. ⊢ ◇F ∧ ◇G ⟶ (◇(F ∧ ◇G)) ∨ (◇(G ∧ ◇F))" and
  discT:      "⋀F. ⊢ □(F ⟶ ◇(¬F ∧ ◇F)) ⟶ (F ⟶ □◇F)" and
  primeI:     "⋀P. ⊢ □P ⟶ Init P`" and
  primeE:     "⋀P F. ⊢ □(Init P ⟶ □F) ⟶ Init P` ⟶ (F ⟶ □F)" and
  indT:       "⋀P F. ⊢ □(Init P ∧ ¬□F ⟶ Init P` ∧ F) ⟶ Init P ⟶ □F" and
  allT:       "⋀F. ⊢ (∀x. □(F x)) = (□(∀ x. F x))"

axiomatization where
  necT:       "⋀F. ⊢ F ⟹ ⊢ □F"      (* polymorphic *)

axiomatization where
(* Flexible quantification: refinement mappings, history variables *)
  eexI:       "⊢ F x ⟶ (∃∃x. F x)" and
  eexE:       "⟦ sigma ⊨ (∃∃x. F x); basevars vs;
                 (⋀x. ⟦ basevars (x, vs); sigma ⊨ F x ⟧ ⟹ (G sigma)::bool)
              ⟧ ⟹ G sigma" and
  history:    "⊢ ∃∃h. Init(h = ha) ∧ □(∀x. $h = #x ⟶ h` = hb x)"


(* Specialize intensional introduction/elimination rules for temporal formulas *)

lemma tempI [intro!]: "(⋀sigma. sigma ⊨ (F::temporal)) ⟹ ⊢ F"
  apply (rule intI)
  apply (erule meta_spec)
  done

lemma tempD [dest]: "⊢ (F::temporal) ⟹ sigma ⊨ F"
  by (erule intD)


(* ======== Functions to "unlift" temporal theorems ====== *)

ML ‹
(* The following functions are specialized versions of the corresponding
   functions defined in theory Intensional in that they introduce a
   "world" parameter of type "behavior".
*)
fun temp_unlift ctxt th =
  (rewrite_rule ctxt @{thms action_rews} (th RS @{thm tempD}))
    handle THM _ => action_unlift ctxt th;

(* Turn  ⊢ F = G  into meta-level rewrite rule  F == G *)
val temp_rewrite = int_rewrite

fun temp_use ctxt th =
  case Thm.concl_of th of
    Const _ $ (Const (\<^const_name>‹Intensional.Valid›, _) $ _) =>
            ((flatten (temp_unlift ctxt th)) handle THM _ => th)
  | _ => th;

fun try_rewrite ctxt th = temp_rewrite ctxt th handle THM _ => temp_use ctxt th;
›

attribute_setup temp_unlift =
  ‹Scan.succeed (Thm.rule_attribute [] (temp_unlift o Context.proof_of))›
attribute_setup temp_rewrite =
  ‹Scan.succeed (Thm.rule_attribute [] (temp_rewrite o Context.proof_of))›
attribute_setup temp_use =
  ‹Scan.succeed (Thm.rule_attribute [] (temp_use o Context.proof_of))›
attribute_setup try_rewrite =
  ‹Scan.succeed (Thm.rule_attribute [] (try_rewrite o Context.proof_of))›


(* ------------------------------------------------------------------------- *)
(***           "Simple temporal logic": only □ and ◇                     ***)
(* ------------------------------------------------------------------------- *)
section "Simple temporal logic"

(* □¬F == □¬Init F *)
lemmas boxNotInit = boxInit [of "LIFT ¬F", unfolded Init_simps] for F

lemma dmdInit: "TEMP ◇F == TEMP ◇ Init F"
  apply (unfold dmd_def)
  apply (unfold boxInit [of "LIFT ¬F"])
  apply (simp (no_asm) add: Init_simps)
  done

lemmas dmdNotInit = dmdInit [of "LIFT ¬F", unfolded Init_simps] for F

(* boxInit and dmdInit cannot be used as rewrites, because they loop.
   Non-looping instances for state predicates and actions are occasionally useful.
*)
lemmas boxInit_stp = boxInit [where 'a = state]
lemmas boxInit_act = boxInit [where 'a = "state * state"]
lemmas dmdInit_stp = dmdInit [where 'a = state]
lemmas dmdInit_act = dmdInit [where 'a = "state * state"]

(* The symmetric equations can be used to get rid of Init *)
lemmas boxInitD = boxInit [symmetric]
lemmas dmdInitD = dmdInit [symmetric]
lemmas boxNotInitD = boxNotInit [symmetric]
lemmas dmdNotInitD = dmdNotInit [symmetric]

lemmas Init_simps = Init_simps boxInitD dmdInitD boxNotInitD dmdNotInitD

(* ------------------------ STL2 ------------------------------------------- *)
lemmas STL2 = reflT

(* The "polymorphic" (generic) variant *)
lemma STL2_gen: "⊢ □F ⟶ Init F"
  apply (unfold boxInit [of F])
  apply (rule STL2)
  done

(* see also STL2_pr below: "⊢ □P ⟶ Init P & Init (P`)" *)


(* Dual versions for ◇ *)
lemma InitDmd: "⊢ F ⟶ ◇ F"
  apply (unfold dmd_def)
  apply (auto dest!: STL2 [temp_use])
  done

lemma InitDmd_gen: "⊢ Init F ⟶ ◇F"
  apply clarsimp
  apply (drule InitDmd [temp_use])
  apply (simp add: dmdInitD)
  done


(* ------------------------ STL3 ------------------------------------------- *)
lemma STL3: "⊢ (□□F) = (□F)"
  by (auto elim: transT [temp_use] STL2 [temp_use])

(* corresponding elimination rule introduces double boxes:
   ⟦ (sigma ⊨ □F); (sigma ⊨ □□F) ⟹ PROP W ⟧ ⟹ PROP W
*)
lemmas dup_boxE = STL3 [temp_unlift, THEN iffD2, elim_format]
lemmas dup_boxD = STL3 [temp_unlift, THEN iffD1]

(* dual versions for ◇ *)
lemma DmdDmd: "⊢ (◇◇F) = (◇F)"
  by (auto simp add: dmd_def [try_rewrite] STL3 [try_rewrite])

lemmas dup_dmdE = DmdDmd [temp_unlift, THEN iffD2, elim_format]
lemmas dup_dmdD = DmdDmd [temp_unlift, THEN iffD1]


(* ------------------------ STL4 ------------------------------------------- *)
lemma STL4:
  assumes "⊢ F ⟶ G"
  shows "⊢ □F ⟶ □G"
  apply clarsimp
  apply (rule normalT [temp_use])
   apply (rule assms [THEN necT, temp_use])
  apply assumption
  done

(* Unlifted version as an elimination rule *)
lemma STL4E: "⟦ sigma ⊨ □F; ⊢ F ⟶ G ⟧ ⟹ sigma ⊨ □G"
  by (erule (1) STL4 [temp_use])

lemma STL4_gen: "⊢ Init F ⟶ Init G ⟹ ⊢ □F ⟶ □G"
  apply (drule STL4)
  apply (simp add: boxInitD)
  done

lemma STL4E_gen: "⟦ sigma ⊨ □F; ⊢ Init F ⟶ Init G ⟧ ⟹ sigma ⊨ □G"
  by (erule (1) STL4_gen [temp_use])

(* see also STL4Edup below, which allows an auxiliary boxed formula:
       □A /\ F => G
     -----------------
     □A /\ □F => □G
*)

(* The dual versions for ◇ *)
lemma DmdImpl:
  assumes prem: "⊢ F ⟶ G"
  shows "⊢ ◇F ⟶ ◇G"
  apply (unfold dmd_def)
  apply (fastforce intro!: prem [temp_use] elim!: STL4E [temp_use])
  done

lemma DmdImplE: "⟦ sigma ⊨ ◇F; ⊢ F ⟶ G ⟧ ⟹ sigma ⊨ ◇G"
  by (erule (1) DmdImpl [temp_use])

(* ------------------------ STL5 ------------------------------------------- *)
lemma STL5: "⊢ (□F ∧ □G) = (□(F ∧ G))"
  apply auto
  apply (subgoal_tac "sigma ⊨ □ (G ⟶ (F ∧ G))")
     apply (erule normalT [temp_use])
     apply (fastforce elim!: STL4E [temp_use])+
  done

(* rewrite rule to split conjunctions under boxes *)
lemmas split_box_conj = STL5 [temp_unlift, symmetric]


(* the corresponding elimination rule allows to combine boxes in the hypotheses
   (NB: F and G must have the same type, i.e., both actions or temporals.)
   Use "addSE2" etc. if you want to add this to a claset, otherwise it will loop!
*)
lemma box_conjE:
  assumes "sigma ⊨ □F"
     and "sigma ⊨ □G"
  and "sigma ⊨ □(F∧G) ⟹ PROP R"
  shows "PROP R"
  by (rule assms STL5 [temp_unlift, THEN iffD1] conjI)+

(* Instances of box_conjE for state predicates, actions, and temporals
   in case the general rule is "too polymorphic".
*)
lemmas box_conjE_temp = box_conjE [where 'a = behavior]
lemmas box_conjE_stp = box_conjE [where 'a = state]
lemmas box_conjE_act = box_conjE [where 'a = "state * state"]

(* Define a tactic that tries to merge all boxes in an antecedent. The definition is
   a bit kludgy in order to simulate "double elim-resolution".
*)

lemma box_thin: "⟦ sigma ⊨ □F; PROP W ⟧ ⟹ PROP W" .

ML ‹
fun merge_box_tac ctxt i =
   REPEAT_DETERM (EVERY [eresolve_tac ctxt @{thms box_conjE} i, assume_tac ctxt i,
    eresolve_tac ctxt @{thms box_thin} i])

fun merge_temp_box_tac ctxt i =
  REPEAT_DETERM (EVERY [eresolve_tac ctxt @{thms box_conjE_temp} i, assume_tac ctxt i,
    Rule_Insts.eres_inst_tac ctxt [((("'a", 0), Position.none), "behavior")] [] @{thm box_thin} i])

fun merge_stp_box_tac ctxt i =
  REPEAT_DETERM (EVERY [eresolve_tac ctxt @{thms box_conjE_stp} i, assume_tac ctxt i,
    Rule_Insts.eres_inst_tac ctxt [((("'a", 0), Position.none), "state")] [] @{thm box_thin} i])

fun merge_act_box_tac ctxt i =
  REPEAT_DETERM (EVERY [eresolve_tac ctxt @{thms box_conjE_act} i, assume_tac ctxt i,
    Rule_Insts.eres_inst_tac ctxt [((("'a", 0), Position.none), "state * state")] [] @{thm box_thin} i])
›

method_setup merge_box = ‹Scan.succeed (SIMPLE_METHOD' o merge_box_tac)›
method_setup merge_temp_box = ‹Scan.succeed (SIMPLE_METHOD' o merge_temp_box_tac)›
method_setup merge_stp_box = ‹Scan.succeed (SIMPLE_METHOD' o merge_stp_box_tac)›
method_setup merge_act_box = ‹Scan.succeed (SIMPLE_METHOD' o merge_act_box_tac)›

(* rewrite rule to push universal quantification through box:
      (sigma ⊨ □(∀x. F x)) = (∀x. (sigma ⊨ □F x))
*)
lemmas all_box = allT [temp_unlift, symmetric]

lemma DmdOr: "⊢ (◇(F ∨ G)) = (◇F ∨ ◇G)"
  apply (auto simp add: dmd_def split_box_conj [try_rewrite])
  apply (erule contrapos_np, merge_box, fastforce elim!: STL4E [temp_use])+
  done

lemma exT: "⊢ (∃x. ◇(F x)) = (◇(∃x. F x))"
  by (auto simp: dmd_def Not_Rex [try_rewrite] all_box [try_rewrite])

lemmas ex_dmd = exT [temp_unlift, symmetric]

lemma STL4Edup: "⋀sigma. ⟦ sigma ⊨ □A; sigma ⊨ □F; ⊢ F ∧ □A ⟶ G ⟧ ⟹ sigma ⊨ □G"
  apply (erule dup_boxE)
  apply merge_box
  apply (erule STL4E)
  apply assumption
  done

lemma DmdImpl2:
    "⋀sigma. ⟦ sigma ⊨ ◇F; sigma ⊨ □(F ⟶ G) ⟧ ⟹ sigma ⊨ ◇G"
  apply (unfold dmd_def)
  apply auto
  apply (erule notE)
  apply merge_box
  apply (fastforce elim!: STL4E [temp_use])
  done

lemma InfImpl:
  assumes 1: "sigma ⊨ □◇F"
    and 2: "sigma ⊨ □G"
    and 3: "⊢ F ∧ G ⟶ H"
  shows "sigma ⊨ □◇H"
  apply (insert 1 2)
  apply (erule_tac F = G in dup_boxE)
  apply merge_box
  apply (fastforce elim!: STL4E [temp_use] DmdImpl2 [temp_use] intro!: 3 [temp_use])
  done

(* ------------------------ STL6 ------------------------------------------- *)
(* Used in the proof of STL6, but useful in itself. *)
lemma BoxDmd: "⊢ □F ∧ ◇G ⟶ ◇(□F ∧ G)"
  apply (unfold dmd_def)
  apply clarsimp
  apply (erule dup_boxE)
  apply merge_box
  apply (erule contrapos_np)
  apply (fastforce elim!: STL4E [temp_use])
  done

(* weaker than BoxDmd, but more polymorphic (and often just right) *)
lemma BoxDmd_simple: "⊢ □F ∧ ◇G ⟶ ◇(F ∧ G)"
  apply (unfold dmd_def)
  apply clarsimp
  apply merge_box
  apply (fastforce elim!: notE STL4E [temp_use])
  done

lemma BoxDmd2_simple: "⊢ □F ∧ ◇G ⟶ ◇(G ∧ F)"
  apply (unfold dmd_def)
  apply clarsimp
  apply merge_box
  apply (fastforce elim!: notE STL4E [temp_use])
  done

lemma DmdImpldup:
  assumes 1: "sigma ⊨ □A"
    and 2: "sigma ⊨ ◇F"
    and 3: "⊢ □A ∧ F ⟶ G"
  shows "sigma ⊨ ◇G"
  apply (rule 2 [THEN 1 [THEN BoxDmd [temp_use]], THEN DmdImplE])
  apply (rule 3)
  done

lemma STL6: "⊢ ◇□F ∧ ◇□G ⟶ ◇□(F ∧ G)"
  apply (auto simp: STL5 [temp_rewrite, symmetric])
  apply (drule linT [temp_use])
   apply assumption
  apply (erule thin_rl)
  apply (rule DmdDmd [temp_unlift, THEN iffD1])
  apply (erule disjE)
   apply (erule DmdImplE)
   apply (rule BoxDmd)
  apply (erule DmdImplE)
  apply auto
  apply (drule BoxDmd [temp_use])
   apply assumption
  apply (erule thin_rl)
  apply (fastforce elim!: DmdImplE [temp_use])
  done


(* ------------------------ True / False ----------------------------------------- *)
section "Simplification of constants"

lemma BoxConst: "⊢ (□#P) = #P"
  apply (rule tempI)
  apply (cases P)
   apply (auto intro!: necT [temp_use] dest: STL2_gen [temp_use] simp: Init_simps)
  done

lemma DmdConst: "⊢ (◇#P) = #P"
  apply (unfold dmd_def)
  apply (cases P)
  apply (simp_all add: BoxConst [try_rewrite])
  done

lemmas temp_simps [temp_rewrite, simp] = BoxConst DmdConst


(* ------------------------ Further rewrites ----------------------------------------- *)
section "Further rewrites"

lemma NotBox: "⊢ (¬□F) = (◇¬F)"
  by (simp add: dmd_def)

lemma NotDmd: "⊢ (¬◇F) = (□¬F)"
  by (simp add: dmd_def)

(* These are not declared by default, because they could be harmful,
   e.g. □F & ¬□F becomes □F & ◇¬F !! *)
lemmas more_temp_simps1 =
  STL3 [temp_rewrite] DmdDmd [temp_rewrite] NotBox [temp_rewrite] NotDmd [temp_rewrite]
  NotBox [temp_unlift, THEN eq_reflection]
  NotDmd [temp_unlift, THEN eq_reflection]

lemma BoxDmdBox: "⊢ (□◇□F) = (◇□F)"
  apply (auto dest!: STL2 [temp_use])
  apply (rule ccontr)
  apply (subgoal_tac "sigma ⊨ ◇□□F ∧ ◇□¬□F")
   apply (erule thin_rl)
   apply auto
    apply (drule STL6 [temp_use])
     apply assumption
    apply simp
   apply (simp_all add: more_temp_simps1)
  done

lemma DmdBoxDmd: "⊢ (◇□◇F) = (□◇F)"
  apply (unfold dmd_def)
  apply (auto simp: BoxDmdBox [unfolded dmd_def, try_rewrite])
  done

lemmas more_temp_simps2 = more_temp_simps1 BoxDmdBox [temp_rewrite] DmdBoxDmd [temp_rewrite]


(* ------------------------ Miscellaneous ----------------------------------- *)

lemma BoxOr: "⋀sigma. ⟦ sigma ⊨ □F ∨ □G ⟧ ⟹ sigma ⊨ □(F ∨ G)"
  by (fastforce elim!: STL4E [temp_use])

(* "persistently implies infinitely often" *)
lemma DBImplBD: "⊢ ◇□F ⟶ □◇F"
  apply clarsimp
  apply (rule ccontr)
  apply (simp add: more_temp_simps2)
  apply (drule STL6 [temp_use])
   apply assumption
  apply simp
  done

lemma BoxDmdDmdBox: "⊢ □◇F ∧ ◇□G ⟶ □◇(F ∧ G)"
  apply clarsimp
  apply (rule ccontr)
  apply (unfold more_temp_simps2)
  apply (drule STL6 [temp_use])
   apply assumption
  apply (subgoal_tac "sigma ⊨ ◇□¬F")
   apply (force simp: dmd_def)
  apply (fastforce elim: DmdImplE [temp_use] STL4E [temp_use])
  done


(* ------------------------------------------------------------------------- *)
(***          TLA-specific theorems: primed formulas                       ***)
(* ------------------------------------------------------------------------- *)
section "priming"

(* ------------------------ TLA2 ------------------------------------------- *)
lemma STL2_pr: "⊢ □P ⟶ Init P ∧ Init P`"
  by (fastforce intro!: STL2_gen [temp_use] primeI [temp_use])

(* Auxiliary lemma allows priming of boxed actions *)
lemma BoxPrime: "⊢ □P ⟶ □($P ∧ P$)"
  apply clarsimp
  apply (erule dup_boxE)
  apply (unfold boxInit_act)
  apply (erule STL4E)
  apply (auto simp: Init_simps dest!: STL2_pr [temp_use])
  done

lemma TLA2:
  assumes "⊢ $P ∧ P$ ⟶ A"
  shows "⊢ □P ⟶ □A"
  apply clarsimp
  apply (drule BoxPrime [temp_use])
  apply (auto simp: Init_stp_act_rev [try_rewrite] intro!: assms [temp_use]
    elim!: STL4E [temp_use])
  done

lemma TLA2E: "⟦ sigma ⊨ □P; ⊢ $P ∧ P$ ⟶ A ⟧ ⟹ sigma ⊨ □A"
  by (erule (1) TLA2 [temp_use])

lemma DmdPrime: "⊢ (◇P`) ⟶ (◇P)"
  apply (unfold dmd_def)
  apply (fastforce elim!: TLA2E [temp_use])
  done

lemmas PrimeDmd = InitDmd_gen [temp_use, THEN DmdPrime [temp_use]]

(* ------------------------ INV1, stable --------------------------------------- *)
section "stable, invariant"

lemma ind_rule:
   "⟦ sigma ⊨ □H; sigma ⊨ Init P; ⊢ H ⟶ (Init P ∧ ¬□F ⟶ Init(P`) ∧ F) ⟧
    ⟹ sigma ⊨ □F"
  apply (rule indT [temp_use])
   apply (erule (2) STL4E)
  done

lemma box_stp_act: "⊢ (□$P) = (□P)"
  by (simp add: boxInit_act Init_simps)

lemmas box_stp_actI = box_stp_act [temp_use, THEN iffD2]
lemmas box_stp_actD = box_stp_act [temp_use, THEN iffD1]

lemmas more_temp_simps3 = box_stp_act [temp_rewrite] more_temp_simps2

lemma INV1:
  "⊢ (Init P) ⟶ (stable P) ⟶ □P"
  apply (unfold stable_def boxInit_stp boxInit_act)
  apply clarsimp
  apply (erule ind_rule)
   apply (auto simp: Init_simps elim: ind_rule)
  done

lemma StableT:
    "⋀P. ⊢ $P ∧ A ⟶ P` ⟹ ⊢ □A ⟶ stable P"
  apply (unfold stable_def)
  apply (fastforce elim!: STL4E [temp_use])
  done

lemma Stable: "⟦ sigma ⊨ □A; ⊢ $P ∧ A ⟶ P` ⟧ ⟹ sigma ⊨ stable P"
  by (erule (1) StableT [temp_use])

(* Generalization of INV1 *)
lemma StableBox: "⊢ (stable P) ⟶ □(Init P ⟶ □P)"
  apply (unfold stable_def)
  apply clarsimp
  apply (erule dup_boxE)
  apply (force simp: stable_def elim: STL4E [temp_use] INV1 [temp_use])
  done

lemma DmdStable: "⊢ (stable P) ∧ ◇P ⟶ ◇□P"
  apply clarsimp
  apply (rule DmdImpl2)
   prefer 2
   apply (erule StableBox [temp_use])
  apply (simp add: dmdInitD)
  done

(* ---------------- (Semi-)automatic invariant tactics ---------------------- *)

ML ‹
(* inv_tac reduces goals of the form ... ⟹ sigma ⊨ □P *)
fun inv_tac ctxt =
  SELECT_GOAL
    (EVERY
     [auto_tac ctxt,
      TRY (merge_box_tac ctxt 1),
      resolve_tac ctxt [temp_use ctxt @{thm INV1}] 1, (* fail if the goal is not a box *)
      TRYALL (eresolve_tac ctxt @{thms Stable})]);

(* auto_inv_tac applies inv_tac and then tries to attack the subgoals
   in simple cases it may be able to handle goals like ⊢ MyProg ⟶ □Inv.
   In these simple cases the simplifier seems to be more useful than the
   auto-tactic, which applies too much propositional logic and simplifies
   too late.
*)
fun auto_inv_tac ctxt =
  SELECT_GOAL
    (inv_tac ctxt 1 THEN
      (TRYALL (action_simp_tac
        (ctxt addsimps [@{thm Init_stp}, @{thm Init_act}]) [] [@{thm squareE}])));
›

method_setup invariant = ‹
  Method.sections Clasimp.clasimp_modifiers >> (K (SIMPLE_METHOD' o inv_tac))
›

method_setup auto_invariant = ‹
  Method.sections Clasimp.clasimp_modifiers >> (K (SIMPLE_METHOD' o auto_inv_tac))
›

lemma unless: "⊢ □($P ⟶ P` ∨ Q`) ⟶ (stable P) ∨ ◇Q"
  apply (unfold dmd_def)
  apply (clarsimp dest!: BoxPrime [temp_use])
  apply merge_box
  apply (erule contrapos_np)
  apply (fastforce elim!: Stable [temp_use])
  done


(* --------------------- Recursive expansions --------------------------------------- *)
section "recursive expansions"

(* Recursive expansions of □ and ◇ for state predicates *)
lemma BoxRec: "⊢ (□P) = (Init P ∧ □P`)"
  apply (auto intro!: STL2_gen [temp_use])
   apply (fastforce elim!: TLA2E [temp_use])
  apply (auto simp: stable_def elim!: INV1 [temp_use] STL4E [temp_use])
  done

lemma DmdRec: "⊢ (◇P) = (Init P ∨ ◇P`)"
  apply (unfold dmd_def BoxRec [temp_rewrite])
  apply (auto simp: Init_simps)
  done

lemma DmdRec2: "⋀sigma. ⟦ sigma ⊨ ◇P; sigma ⊨ □¬P` ⟧ ⟹ sigma ⊨ Init P"
  apply (force simp: DmdRec [temp_rewrite] dmd_def)
  done

lemma InfinitePrime: "⊢ (□◇P) = (□◇P`)"
  apply auto
   apply (rule classical)
   apply (rule DBImplBD [temp_use])
   apply (subgoal_tac "sigma ⊨ ◇□P")
    apply (fastforce elim!: DmdImplE [temp_use] TLA2E [temp_use])
   apply (subgoal_tac "sigma ⊨ ◇□ (◇P ∧ □¬P`)")
    apply (force simp: boxInit_stp [temp_use]
      elim!: DmdImplE [temp_use] STL4E [temp_use] DmdRec2 [temp_use])
   apply (force intro!: STL6 [temp_use] simp: more_temp_simps3)
  apply (fastforce intro: DmdPrime [temp_use] elim!: STL4E [temp_use])
  done

lemma InfiniteEnsures:
  "⟦ sigma ⊨ □N; sigma ⊨ □◇A; ⊢ A ∧ N ⟶ P` ⟧ ⟹ sigma ⊨ □◇P"
  apply (unfold InfinitePrime [temp_rewrite])
  apply (rule InfImpl)
    apply assumption+
  done

(* ------------------------ fairness ------------------------------------------- *)
section "fairness"

(* alternative definitions of fairness *)
lemma WF_alt: "⊢ WF(A)_v = (□◇¬Enabled(<A>_v) ∨ □◇<A>_v)"
  apply (unfold WF_def dmd_def)
  apply fastforce
  done

lemma SF_alt: "⊢ SF(A)_v = (◇□¬Enabled(<A>_v) ∨ □◇<A>_v)"
  apply (unfold SF_def dmd_def)
  apply fastforce
  done

(* theorems to "box" fairness conditions *)
lemma BoxWFI: "⊢ WF(A)_v ⟶ □WF(A)_v"
  by (auto simp: WF_alt [try_rewrite] more_temp_simps3 intro!: BoxOr [temp_use])

lemma WF_Box: "⊢ (□WF(A)_v) = WF(A)_v"
  by (fastforce intro!: BoxWFI [temp_use] dest!: STL2 [temp_use])

lemma BoxSFI: "⊢ SF(A)_v ⟶ □SF(A)_v"
  by (auto simp: SF_alt [try_rewrite] more_temp_simps3 intro!: BoxOr [temp_use])

lemma SF_Box: "⊢ (□SF(A)_v) = SF(A)_v"
  by (fastforce intro!: BoxSFI [temp_use] dest!: STL2 [temp_use])

lemmas more_temp_simps = more_temp_simps3 WF_Box [temp_rewrite] SF_Box [temp_rewrite]

lemma SFImplWF: "⊢ SF(A)_v ⟶ WF(A)_v"
  apply (unfold SF_def WF_def)
  apply (fastforce dest!: DBImplBD [temp_use])
  done

(* A tactic that "boxes" all fairness conditions. Apply more_temp_simps to "unbox". *)
ML ‹
fun box_fair_tac ctxt =
  SELECT_GOAL (REPEAT (dresolve_tac ctxt [@{thm BoxWFI}, @{thm BoxSFI}] 1))
›


(* ------------------------------ leads-to ------------------------------ *)

section "↝"

lemma leadsto_init: "⊢ (Init F) ∧ (F ↝ G) ⟶ ◇G"
  apply (unfold leadsto_def)
  apply (auto dest!: STL2 [temp_use])
  done

(* ⊢ F & (F ↝ G) ⟶ ◇G *)
lemmas leadsto_init_temp = leadsto_init [where 'a = behavior, unfolded Init_simps]

lemma streett_leadsto: "⊢ (□◇Init F ⟶ □◇G) = (◇(F ↝ G))"
  apply (unfold leadsto_def)
  apply auto
    apply (simp add: more_temp_simps)
    apply (fastforce elim!: DmdImplE [temp_use] STL4E [temp_use])
   apply (fastforce intro!: InitDmd [temp_use] elim!: STL4E [temp_use])
  apply (subgoal_tac "sigma ⊨ □◇◇G")
   apply (simp add: more_temp_simps)
  apply (drule BoxDmdDmdBox [temp_use])
   apply assumption
  apply (fastforce elim!: DmdImplE [temp_use] STL4E [temp_use])
  done

lemma leadsto_infinite: "⊢ □◇F ∧ (F ↝ G) ⟶ □◇G"
  apply clarsimp
  apply (erule InitDmd [temp_use, THEN streett_leadsto [temp_unlift, THEN iffD2, THEN mp]])
  apply (simp add: dmdInitD)
  done

(* In particular, strong fairness is a Streett condition. The following
   rules are sometimes easier to use than WF2 or SF2 below.
*)
lemma leadsto_SF: "⊢ (Enabled(<A>_v) ↝ <A>_v) ⟶ SF(A)_v"
  apply (unfold SF_def)
  apply (clarsimp elim!: leadsto_infinite [temp_use])
  done

lemma leadsto_WF: "⊢ (Enabled(<A>_v) ↝ <A>_v) ⟶ WF(A)_v"
  by (clarsimp intro!: SFImplWF [temp_use] leadsto_SF [temp_use])

(* introduce an invariant into the proof of a leadsto assertion.
   □I ⟶ ((P ↝ Q)  =  (P /\ I ↝ Q))
*)
lemma INV_leadsto: "⊢ □I ∧ (P ∧ I ↝ Q) ⟶ (P ↝ Q)"
  apply (unfold leadsto_def)
  apply clarsimp
  apply (erule STL4Edup)
   apply assumption
  apply (auto simp: Init_simps dest!: STL2_gen [temp_use])
  done

lemma leadsto_classical: "⊢ (Init F ∧ □¬G ↝ G) ⟶ (F ↝ G)"
  apply (unfold leadsto_def dmd_def)
  apply (force simp: Init_simps elim!: STL4E [temp_use])
  done

lemma leadsto_false: "⊢ (F ↝ #False) = (□¬F)"
  apply (unfold leadsto_def)
  apply (simp add: boxNotInitD)
  done

lemma leadsto_exists: "⊢ ((∃x. F x) ↝ G) = (∀x. (F x ↝ G))"
  apply (unfold leadsto_def)
  apply (auto simp: allT [try_rewrite] Init_simps elim!: STL4E [temp_use])
  done

(* basic leadsto properties, cf. Unity *)

lemma ImplLeadsto_gen: "⊢ □(Init F ⟶ Init G) ⟶ (F ↝ G)"
  apply (unfold leadsto_def)
  apply (auto intro!: InitDmd_gen [temp_use]
    elim!: STL4E_gen [temp_use] simp: Init_simps)
  done

lemmas ImplLeadsto =
  ImplLeadsto_gen [where 'a = behavior and 'b = behavior, unfolded Init_simps]

lemma ImplLeadsto_simple: "⋀F G. ⊢ F ⟶ G ⟹ ⊢ F ↝ G"
  by (auto simp: Init_def intro!: ImplLeadsto_gen [temp_use] necT [temp_use])

lemma EnsuresLeadsto:
  assumes "⊢ A ∧ $P ⟶ Q`"
  shows "⊢ □A ⟶ (P ↝ Q)"
  apply (unfold leadsto_def)
  apply (clarsimp elim!: INV_leadsto [temp_use])
  apply (erule STL4E_gen)
  apply (auto simp: Init_defs intro!: PrimeDmd [temp_use] assms [temp_use])
  done

lemma EnsuresLeadsto2: "⊢ □($P ⟶ Q`) ⟶ (P ↝ Q)"
  apply (unfold leadsto_def)
  apply clarsimp
  apply (erule STL4E_gen)
  apply (auto simp: Init_simps intro!: PrimeDmd [temp_use])
  done

lemma ensures:
  assumes 1: "⊢ $P ∧ N ⟶ P` ∨ Q`"
    and 2: "⊢ ($P ∧ N) ∧ A ⟶ Q`"
  shows "⊢ □N ∧ □(□P ⟶ ◇A) ⟶ (P ↝ Q)"
  apply (unfold leadsto_def)
  apply clarsimp
  apply (erule STL4Edup)
   apply assumption
  apply clarsimp
  apply (subgoal_tac "sigmaa ⊨ □($P ⟶ P` ∨ Q`) ")
   apply (drule unless [temp_use])
   apply (clarsimp dest!: INV1 [temp_use])
  apply (rule 2 [THEN DmdImpl, temp_use, THEN DmdPrime [temp_use]])
   apply (force intro!: BoxDmd_simple [temp_use]
     simp: split_box_conj [try_rewrite] box_stp_act [try_rewrite])
  apply (force elim: STL4E [temp_use] dest: 1 [temp_use])
  done

lemma ensures_simple:
  "⟦ ⊢ $P ∧ N ⟶ P` ∨ Q`;
      ⊢ ($P ∧ N) ∧ A ⟶ Q`
   ⟧ ⟹ ⊢ □N ∧ □◇A ⟶ (P ↝ Q)"
  apply clarsimp
  apply (erule (2) ensures [temp_use])
  apply (force elim!: STL4E [temp_use])
  done

lemma EnsuresInfinite:
    "⟦ sigma ⊨ □◇P; sigma ⊨ □A; ⊢ A ∧ $P ⟶ Q` ⟧ ⟹ sigma ⊨ □◇Q"
  apply (erule leadsto_infinite [temp_use])
  apply (erule EnsuresLeadsto [temp_use])
  apply assumption
  done


(*** Gronning's lattice rules (taken from TLP) ***)
section "Lattice rules"

lemma LatticeReflexivity: "⊢ F ↝ F"
  apply (unfold leadsto_def)
  apply (rule necT InitDmd_gen)+
  done

lemma LatticeTransitivity: "⊢ (G ↝ H) ∧ (F ↝ G) ⟶ (F ↝ H)"
  apply (unfold leadsto_def)
  apply clarsimp
  apply (erule dup_boxE) (* □□(Init G ⟶ H) *)
  apply merge_box
  apply (clarsimp elim!: STL4E [temp_use])
  apply (rule dup_dmdD)
  apply (subgoal_tac "sigmaa ⊨ ◇Init G")
   apply (erule DmdImpl2)
   apply assumption
  apply (simp add: dmdInitD)
  done

lemma LatticeDisjunctionElim1: "⊢ (F ∨ G ↝ H) ⟶ (F ↝ H)"
  apply (unfold leadsto_def)
  apply (auto simp: Init_simps elim!: STL4E [temp_use])
  done

lemma LatticeDisjunctionElim2: "⊢ (F ∨ G ↝ H) ⟶ (G ↝ H)"
  apply (unfold leadsto_def)
  apply (auto simp: Init_simps elim!: STL4E [temp_use])
  done

lemma LatticeDisjunctionIntro: "⊢ (F ↝ H) ∧ (G ↝ H) ⟶ (F ∨ G ↝ H)"
  apply (unfold leadsto_def)
  apply clarsimp
  apply merge_box
  apply (auto simp: Init_simps elim!: STL4E [temp_use])
  done

lemma LatticeDisjunction: "⊢ (F ∨ G ↝ H) = ((F ↝ H) ∧ (G ↝ H))"
  by (auto intro: LatticeDisjunctionIntro [temp_use]
    LatticeDisjunctionElim1 [temp_use]
    LatticeDisjunctionElim2 [temp_use])

lemma LatticeDiamond: "⊢ (A ↝ B ∨ C) ∧ (B ↝ D) ∧ (C ↝ D) ⟶ (A ↝ D)"
  apply clarsimp
  apply (subgoal_tac "sigma ⊨ (B ∨ C) ↝ D")
  apply (erule_tac G = "LIFT (B ∨ C)" in LatticeTransitivity [temp_use])
   apply (fastforce intro!: LatticeDisjunctionIntro [temp_use])+
  done

lemma LatticeTriangle: "⊢ (A ↝ D ∨ B) ∧ (B ↝ D) ⟶ (A ↝ D)"
  apply clarsimp
  apply (subgoal_tac "sigma ⊨ (D ∨ B) ↝ D")
   apply (erule_tac G = "LIFT (D ∨ B)" in LatticeTransitivity [temp_use])
  apply assumption
  apply (auto intro: LatticeDisjunctionIntro [temp_use] LatticeReflexivity [temp_use])
  done

lemma LatticeTriangle2: "⊢ (A ↝ B ∨ D) ∧ (B ↝ D) ⟶ (A ↝ D)"
  apply clarsimp
  apply (subgoal_tac "sigma ⊨ B ∨ D ↝ D")
   apply (erule_tac G = "LIFT (B ∨ D)" in LatticeTransitivity [temp_use])
   apply assumption
  apply (auto intro: LatticeDisjunctionIntro [temp_use] LatticeReflexivity [temp_use])
  done

(*** Lamport's fairness rules ***)
section "Fairness rules"

lemma WF1:
  "⟦ ⊢ $P ∧ N  ⟶ P` ∨ Q`;
      ⊢ ($P ∧ N) ∧ <A>_v ⟶ Q`;
      ⊢ $P ∧ N ⟶ $(Enabled(<A>_v)) ⟧
  ⟹ ⊢ □N ∧ WF(A)_v ⟶ (P ↝ Q)"
  apply (clarsimp dest!: BoxWFI [temp_use])
  apply (erule (2) ensures [temp_use])
  apply (erule (1) STL4Edup)
  apply (clarsimp simp: WF_def)
  apply (rule STL2 [temp_use])
  apply (clarsimp elim!: mp intro!: InitDmd [temp_use])
  apply (erule STL4 [temp_use, THEN box_stp_actD [temp_use]])
  apply (simp add: split_box_conj box_stp_actI)
  done

(* Sometimes easier to use; designed for action B rather than state predicate Q *)
lemma WF_leadsto:
  assumes 1: "⊢ N ∧ $P ⟶ $Enabled (<A>_v)"
    and 2: "⊢ N ∧ <A>_v ⟶ B"
    and 3: "⊢ □(N ∧ [¬A]_v) ⟶ stable P"
  shows "⊢ □N ∧ WF(A)_v ⟶ (P ↝ B)"
  apply (unfold leadsto_def)
  apply (clarsimp dest!: BoxWFI [temp_use])
  apply (erule (1) STL4Edup)
  apply clarsimp
  apply (rule 2 [THEN DmdImpl, temp_use])
  apply (rule BoxDmd_simple [temp_use])
   apply assumption
  apply (rule classical)
  apply (rule STL2 [temp_use])
  apply (clarsimp simp: WF_def elim!: mp intro!: InitDmd [temp_use])
  apply (rule 1 [THEN STL4, temp_use, THEN box_stp_actD])
  apply (simp (no_asm_simp) add: split_box_conj [try_rewrite] box_stp_act [try_rewrite])
  apply (erule INV1 [temp_use])
  apply (rule 3 [temp_use])
  apply (simp add: split_box_conj [try_rewrite] NotDmd [temp_use] not_angle [try_rewrite])
  done

lemma SF1:
  "⟦ ⊢ $P ∧ N  ⟶ P` ∨ Q`;
      ⊢ ($P ∧ N) ∧ <A>_v ⟶ Q`;
      ⊢ □P ∧ □N ∧ □F ⟶ ◇Enabled(<A>_v) ⟧
  ⟹ ⊢ □N ∧ SF(A)_v ∧ □F ⟶ (P ↝ Q)"
  apply (clarsimp dest!: BoxSFI [temp_use])
  apply (erule (2) ensures [temp_use])
  apply (erule_tac F = F in dup_boxE)
  apply merge_temp_box
  apply (erule STL4Edup)
  apply assumption
  apply (clarsimp simp: SF_def)
  apply (rule STL2 [temp_use])
  apply (erule mp)
  apply (erule STL4 [temp_use])
  apply (simp add: split_box_conj [try_rewrite] STL3 [try_rewrite])
  done

lemma WF2:
  assumes 1: "⊢ N ∧ <B>_f ⟶ <M>_g"
    and 2: "⊢ $P ∧ P` ∧ <N ∧ A>_f ⟶ B"
    and 3: "⊢ P ∧ Enabled(<M>_g) ⟶ Enabled(<A>_f)"
    and 4: "⊢ □(N ∧ [¬B]_f) ∧ WF(A)_f ∧ □F ∧ ◇□Enabled(<M>_g) ⟶ ◇□P"
  shows "⊢ □N ∧ WF(A)_f ∧ □F ⟶ WF(M)_g"
  apply (clarsimp dest!: BoxWFI [temp_use] BoxDmdBox [temp_use, THEN iffD2]
    simp: WF_def [where A = M])
  apply (erule_tac F = F in dup_boxE)
  apply merge_temp_box
  apply (erule STL4Edup)
   apply assumption
  apply (clarsimp intro!: BoxDmd_simple [temp_use, THEN 1 [THEN DmdImpl, temp_use]])
  apply (rule classical)
  apply (subgoal_tac "sigmaa ⊨ ◇ (($P ∧ P` ∧ N) ∧ <A>_f)")
   apply (force simp: angle_def intro!: 2 [temp_use] elim!: DmdImplE [temp_use])
  apply (rule BoxDmd_simple [THEN DmdImpl, unfolded DmdDmd [temp_rewrite], temp_use])
  apply (simp add: NotDmd [temp_use] not_angle [try_rewrite])
  apply merge_act_box
  apply (frule 4 [temp_use])
     apply assumption+
  apply (drule STL6 [temp_use])
   apply assumption
  apply (erule_tac V = "sigmaa ⊨ ◇□P" in thin_rl)
  apply (erule_tac V = "sigmaa ⊨ □F" in thin_rl)
  apply (drule BoxWFI [temp_use])
  apply (erule_tac F = "ACT N ∧ [¬B]_f" in dup_boxE)
  apply merge_temp_box
  apply (erule DmdImpldup)
   apply assumption
  apply (auto simp: split_box_conj [try_rewrite] STL3 [try_rewrite]
    WF_Box [try_rewrite] box_stp_act [try_rewrite])
   apply (force elim!: TLA2E [where P = P, temp_use])
  apply (rule STL2 [temp_use])
  apply (force simp: WF_def split_box_conj [try_rewrite]
    elim!: mp intro!: InitDmd [temp_use] 3 [THEN STL4, temp_use])
  done

lemma SF2:
  assumes 1: "⊢ N ∧ <B>_f ⟶ <M>_g"
    and 2: "⊢ $P ∧ P` ∧ <N ∧ A>_f ⟶ B"
    and 3: "⊢ P ∧ Enabled(<M>_g) ⟶ Enabled(<A>_f)"
    and 4: "⊢ □(N ∧ [¬B]_f) ∧ SF(A)_f ∧ □F ∧ □◇Enabled(<M>_g) ⟶ ◇□P"
  shows "⊢ □N ∧ SF(A)_f ∧ □F ⟶ SF(M)_g"
  apply (clarsimp dest!: BoxSFI [temp_use] simp: 2 [try_rewrite] SF_def [where A = M])
  apply (erule_tac F = F in dup_boxE)
  apply (erule_tac F = "TEMP ◇Enabled (<M>_g) " in dup_boxE)
  apply merge_temp_box
  apply (erule STL4Edup)
   apply assumption
  apply (clarsimp intro!: BoxDmd_simple [temp_use, THEN 1 [THEN DmdImpl, temp_use]])
  apply (rule classical)
  apply (subgoal_tac "sigmaa ⊨ ◇ (($P ∧ P` ∧ N) ∧ <A>_f)")
   apply (force simp: angle_def intro!: 2 [temp_use] elim!: DmdImplE [temp_use])
  apply (rule BoxDmd_simple [THEN DmdImpl, unfolded DmdDmd [temp_rewrite], temp_use])
  apply (simp add: NotDmd [temp_use] not_angle [try_rewrite])
  apply merge_act_box
  apply (frule 4 [temp_use])
     apply assumption+
  apply (erule_tac V = "sigmaa ⊨ □F" in thin_rl)
  apply (drule BoxSFI [temp_use])
  apply (erule_tac F = "TEMP ◇Enabled (<M>_g)" in dup_boxE)
  apply (erule_tac F = "ACT N ∧ [¬B]_f" in dup_boxE)
  apply merge_temp_box
  apply (erule DmdImpldup)
   apply assumption
  apply (auto simp: split_box_conj [try_rewrite] STL3 [try_rewrite]
    SF_Box [try_rewrite] box_stp_act [try_rewrite])
   apply (force elim!: TLA2E [where P = P, temp_use])
  apply (rule STL2 [temp_use])
  apply (force simp: SF_def split_box_conj [try_rewrite]
    elim!: mp InfImpl [temp_use] intro!: 3 [temp_use])
  done

(* ------------------------------------------------------------------------- *)
(***           Liveness proofs by well-founded orderings                   ***)
(* ------------------------------------------------------------------------- *)
section "Well-founded orderings"

lemma wf_leadsto:
  assumes 1: "wf r"
    and 2: "⋀x. sigma ⊨ F x ↝ (G ∨ (∃y. #((y,x)∈r) ∧ F y))    "
  shows "sigma ⊨ F x ↝ G"
  apply (rule 1 [THEN wf_induct])
  apply (rule LatticeTriangle [temp_use])
   apply (rule 2)
  apply (auto simp: leadsto_exists [try_rewrite])
  apply (case_tac "(y,x) ∈ r")
   apply force
  apply (force simp: leadsto_def Init_simps intro!: necT [temp_use])
  done

(* If r is well-founded, state function v cannot decrease forever *)
lemma wf_not_box_decrease: "⋀r. wf r ⟹ ⊢ □[ (v`, $v) ∈ #r ]_v ⟶ ◇□[#False]_v"
  apply clarsimp
  apply (rule ccontr)
  apply (subgoal_tac "sigma ⊨ (∃x. v=#x) ↝ #False")
   apply (drule leadsto_false [temp_use, THEN iffD1, THEN STL2_gen [temp_use]])
   apply (force simp: Init_defs)
  apply (clarsimp simp: leadsto_exists [try_rewrite] not_square [try_rewrite] more_temp_simps)
  apply (erule wf_leadsto)
  apply (rule ensures_simple [temp_use])
   apply (auto simp: square_def angle_def)
  done

(* "wf r  ⟹  ⊢ ◇□[ (v`, $v) : #r ]_v ⟶ ◇□[#False]_v" *)
lemmas wf_not_dmd_box_decrease =
  wf_not_box_decrease [THEN DmdImpl, unfolded more_temp_simps]

(* If there are infinitely many steps where v decreases, then there
   have to be infinitely many non-stuttering steps where v doesn't decrease.
*)
lemma wf_box_dmd_decrease:
  assumes 1: "wf r"
  shows "⊢ □◇((v`, $v) ∈ #r) ⟶ □◇<(v`, $v) ∉ #r>_v"
  apply clarsimp
  apply (rule ccontr)
  apply (simp add: not_angle [try_rewrite] more_temp_simps)
  apply (drule 1 [THEN wf_not_dmd_box_decrease [temp_use]])
  apply (drule BoxDmdDmdBox [temp_use])
   apply assumption
  apply (subgoal_tac "sigma ⊨ □◇ ((#False) ::action)")
   apply force
  apply (erule STL4E)
  apply (rule DmdImpl)
  apply (force intro: 1 [THEN wf_irrefl, temp_use])
  done

(* In particular, for natural numbers, if n decreases infinitely often
   then it has to increase infinitely often.
*)
lemma nat_box_dmd_decrease: "⋀n::nat stfun. ⊢ □◇(n` < $n) ⟶ □◇($n < n`)"
  apply clarsimp
  apply (subgoal_tac "sigma ⊨ □◇<¬ ((n`,$n) ∈ #less_than)>_n")
   apply (erule thin_rl)
   apply (erule STL4E)
   apply (rule DmdImpl)
   apply (clarsimp simp: angle_def [try_rewrite])
  apply (rule wf_box_dmd_decrease [temp_use])
   apply (auto elim!: STL4E [temp_use] DmdImplE [temp_use])
  done


(* ------------------------------------------------------------------------- *)
(***           Flexible quantification over state variables                ***)
(* ------------------------------------------------------------------------- *)
section "Flexible quantification"

lemma aallI:
  assumes 1: "basevars vs"
    and 2: "(⋀x. basevars (x,vs) ⟹ sigma ⊨ F x)"
  shows "sigma ⊨ (∀∀x. F x)"
  by (auto simp: aall_def elim!: eexE [temp_use] intro!: 1 dest!: 2 [temp_use])

lemma aallE: "⊢ (∀∀x. F x) ⟶ F x"
  apply (unfold aall_def)
  apply clarsimp
  apply (erule contrapos_np)
  apply (force intro!: eexI [temp_use])
  done

(* monotonicity of quantification *)
lemma eex_mono:
  assumes 1: "sigma ⊨ ∃∃x. F x"
    and 2: "⋀x. sigma ⊨ F x ⟶ G x"
  shows "sigma ⊨ ∃∃x. G x"
  apply (rule unit_base [THEN 1 [THEN eexE]])
  apply (rule eexI [temp_use])
  apply (erule 2 [unfolded intensional_rews, THEN mp])
  done

lemma aall_mono:
  assumes 1: "sigma ⊨ ∀∀x. F(x)"
    and 2: "⋀x. sigma ⊨ F(x) ⟶ G(x)"
  shows "sigma ⊨ ∀∀x. G(x)"
  apply (rule unit_base [THEN aallI])
  apply (rule 2 [unfolded intensional_rews, THEN mp])
  apply (rule 1 [THEN aallE [temp_use]])
  done

(* Derived history introduction rule *)
lemma historyI:
  assumes 1: "sigma ⊨ Init I"
    and 2: "sigma ⊨ □N"
    and 3: "basevars vs"
    and 4: "⋀h. basevars(h,vs) ⟹ ⊢ I ∧ h = ha ⟶ HI h"
    and 5: "⋀h s t. ⟦ basevars(h,vs); N (s,t); h t = hb (h s) (s,t) ⟧ ⟹ HN h (s,t)"
  shows "sigma ⊨ ∃∃h. Init (HI h) ∧ □(HN h)"
  apply (rule history [temp_use, THEN eexE])
  apply (rule 3)
  apply (rule eexI [temp_use])
  apply clarsimp
  apply (rule conjI)
   prefer 2
   apply (insert 2)
   apply merge_box
   apply (force elim!: STL4E [temp_use] 5 [temp_use])
  apply (insert 1)
  apply (force simp: Init_defs elim!: 4 [temp_use])
  done

(* ----------------------------------------------------------------------
   example of a history variable: existence of a clock
*)

lemma "⊢ ∃∃h. Init(h = #True) ∧ □(h` = (¬$h))"
  apply (rule tempI)
  apply (rule historyI)
  apply (force simp: Init_defs intro!: unit_base [temp_use] necT [temp_use])+
  done

end