Theory PDS

theory PDS imports "P_Automata" "HOL-Library.While_Combinator" begin


section ‹PDS›

datatype 'label operation = pop | swap 'label | push 'label 'label
type_synonym ('ctr_loc, 'label) rule = "('ctr_loc × 'label) × ('ctr_loc × 'label operation)"
type_synonym ('ctr_loc, 'label) conf = "'ctr_loc × 'label list"


text ‹We define push down systems.›

locale PDS =
  fixes Δ :: "('ctr_loc, 'label::finite) rule set"
  (* 'ctr_loc is the type of control locations *)
  
begin

primrec lbl :: "'label operation ⇒ 'label list" where
  "lbl pop = []"
| "lbl (swap γ) = [γ]" 
| "lbl (push γ  γ') = [γ, γ']"

definition is_rule :: "'ctr_loc × 'label ⇒ 'ctr_loc × 'label operation ⇒ bool" (infix "↪" 80) where
  "pγ ↪ p'w ≡ (pγ,p'w) ∈ Δ"

inductive_set transition_rel :: "(('ctr_loc, 'label) conf × unit × ('ctr_loc, 'label) conf) set" where
  "(p, γ) ↪ (p', w) ⟹ 
   ((p, γ#w'), (), (p', (lbl w)@w')) ∈ transition_rel"

interpretation LTS transition_rel .

notation step_relp (infix "⇒" 80)
notation step_starp (infix "⇒⇧*" 80)

lemma step_relp_def2:
  "(p, γw') ⇒ (p',ww') ⟷ (∃γ w' w. γw' = γ#w' ∧ ww' = (lbl w)@w' ∧ (p, γ) ↪ (p', w))"
  by (metis (no_types, lifting) PDS.transition_rel.intros step_relp_def transition_rel.cases)

end


section ‹PDS with P automata›

type_synonym ('ctr_loc, 'label) sat_rule = "('ctr_loc, 'label) transition set ⇒ ('ctr_loc, 'label) transition set ⇒ bool"

datatype ('ctr_loc, 'noninit, 'label) state =
  is_Init: Init (the_Ctr_Loc: 'ctr_loc) (* p ∈ P *)
  | is_Noninit: Noninit (the_St: 'noninit) (* q ∈ Q ∧ q ∉ P *)
  | is_Isolated: Isolated (the_Ctr_Loc: 'ctr_loc) (the_Label: 'label) (* q⇩p⇩γ *)

lemma finitely_many_states:
  assumes "finite (UNIV :: 'ctr_loc set)"
  assumes "finite (UNIV :: 'noninit set)"
  assumes "finite (UNIV :: 'label set)"
  shows "finite (UNIV :: ('ctr_loc, 'noninit, 'label) state set)"
proof -
  define Isolated' :: "('ctr_loc * 'label) ⇒ ('ctr_loc, 'noninit, 'label) state" where 
    "Isolated' == λ(c :: 'ctr_loc, l:: 'label). Isolated c l"
  define Init' :: "'ctr_loc ⇒ ('ctr_loc, 'noninit, 'label) state" where
    "Init' = Init"
  define Noninit' :: "'noninit ⇒ ('ctr_loc, 'noninit, 'label) state" where
    "Noninit' = Noninit"

  have split: "UNIV = (Init' ` UNIV) ∪ (Noninit' ` UNIV) ∪ (Isolated' ` (UNIV :: (('ctr_loc * 'label) set)))"
    unfolding Init'_def Noninit'_def
  proof (rule; rule; rule; rule)
    fix x :: "('ctr_loc, 'noninit, 'label) state"
    assume "x ∈ UNIV"
    moreover
    assume "x ∉ range Isolated'"
    moreover
    assume "x ∉ range Noninit"
    ultimately
    show "x ∈ range Init"
      by (metis Isolated'_def prod.simps(2) range_eqI state.exhaust)
  qed

  have "finite (Init' ` (UNIV:: 'ctr_loc set))"
    using assms by auto
  moreover
  have "finite (Noninit' ` (UNIV:: 'noninit set))"
    using assms by auto
  moreover
  have "finite (UNIV :: (('ctr_loc * 'label) set))"
    using assms by (simp add: finite_Prod_UNIV)
  then have "finite (Isolated' ` (UNIV :: (('ctr_loc * 'label) set)))"
    by auto
  ultimately
  show "finite (UNIV :: ('ctr_loc, 'noninit, 'label) state set)"
    unfolding split by auto
qed

instantiation state :: (finite, finite, finite) finite begin

instance by standard (simp add: finitely_many_states)

end


locale PDS_with_P_automata = PDS Δ
  for Δ :: "('ctr_loc::enum, 'label::finite) rule set"
    +
  fixes final_inits :: "('ctr_loc::enum) set"
  fixes final_noninits :: "('noninit::finite) set"
begin

(* Corresponds to Schwoon's F *)
definition finals :: "('ctr_loc, 'noninit::finite, 'label) state set" where
  "finals = Init ` final_inits ∪ Noninit ` final_noninits"

lemma F_not_Ext: "¬(∃f∈finals. is_Isolated f)"
  using finals_def by fastforce

(* Corresponds to Schwoon's P *)
definition inits :: "('ctr_loc, 'noninit, 'label) state set" where 
  "inits = {q. is_Init q}"

lemma inits_code[code]: "inits = set (map Init Enum.enum)"
  by (auto simp: inits_def is_Init_def simp flip: UNIV_enum)

definition noninits :: "('ctr_loc, 'noninit, 'label) state set" where
  "noninits = {q. is_Noninit q}"

definition isols :: "('ctr_loc, 'noninit, 'label) state set" where
  "isols = {q. is_Isolated q}"

sublocale LTS transition_rel .
notation step_relp (infix "⇒" 80)
notation step_starp (infix "⇒⇧*" 80)

definition accepts :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ ('ctr_loc, 'label) conf ⇒ bool" where
  "accepts ts ≡ λ(p,w). (∃q ∈ finals. (Init p,w,q) ∈ LTS.trans_star ts)"

lemma accepts_accepts_aut: "accepts ts (p, w) ⟷ P_Automaton.accepts_aut ts Init finals p w"
  unfolding accepts_def P_Automaton.accepts_aut_def inits_def by auto

definition accepts_ε :: "(('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ ('ctr_loc, 'label) conf ⇒ bool" where
  "accepts_ε ts ≡ λ(p,w). (∃q ∈ finals. (Init p,w,q) ∈ LTS_ε.trans_star_ε ts)"

abbreviation ε :: "'label option" where
  "ε == None"

lemma accepts_mono[mono]: "mono accepts" 
proof (rule, rule)
  fix c :: "('ctr_loc, 'label) conf"
  fix ts ts' :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set"
  assume accepts_ts: "accepts ts c"
  assume tsts': "ts ⊆ ts'"
  obtain p l where pl_p: "c = (p,l)"
    by (cases c)
  obtain q where q_p:  "q ∈ finals ∧ (Init p, l, q) ∈ LTS.trans_star ts"
    using accepts_ts unfolding pl_p accepts_def by auto
  then have "(Init p, l, q) ∈ LTS.trans_star ts'"
    using tsts' LTS_trans_star_mono monoD by blast 
  then have "accepts ts' (p,l)"
    unfolding accepts_def using q_p by auto
  then show "accepts ts' c"
    unfolding pl_p .
qed

lemma accepts_cons: "(Init p, γ, Init p') ∈ ts ⟹ accepts ts (p', w) ⟹ accepts ts (p, γ # w)"
  using LTS.trans_star.trans_star_step accepts_def by fastforce 

definition lang :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ ('ctr_loc, 'label) conf set" where
  "lang ts = {c. accepts ts c}"

lemma lang_lang_aut: "lang ts = (λ(s,w). (s, w)) ` (P_Automaton.lang_aut ts Init finals)"
  unfolding lang_def P_Automaton.lang_aut_def
  by (auto simp: inits_def accepts_def P_Automaton.accepts_aut_def image_iff intro!: exI[of _ "Init _"])

lemma lang_aut_lang: "P_Automaton.lang_aut ts Init finals = lang ts"
  unfolding lang_lang_aut
  by (auto 0 3 simp: P_Automaton.lang_aut_def P_Automaton.accepts_aut_def inits_def image_iff)

definition lang_ε :: "(('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ ('ctr_loc, 'label) conf set" where
  "lang_ε ts = {c. accepts_ε ts c}"


subsection ‹Saturations›

definition saturated :: "('c, 'l) sat_rule ⇒ ('c, 'l) transition set ⇒ bool" where
  "saturated rule ts ⟷ (∄ts'. rule ts ts')"

definition saturation :: "('c, 'l) sat_rule ⇒ ('c, 'l) transition set ⇒ ('c, 'l) transition set ⇒ bool" where
  "saturation rule ts ts' ⟷ rule⇧*⇧* ts ts' ∧ saturated rule ts'"

lemma no_infinite: 
  assumes "⋀ts ts' :: ('c ::finite, 'l::finite) transition set. rule ts ts' ⟹ card ts' = Suc (card ts)"
  assumes "∀i :: nat. rule (tts i) (tts (Suc i))"
  shows "False"
proof -
  define f where "f i = card (tts i)" for i
  have f_Suc: "∀i. f i < f (Suc i)"
    using assms f_def lessI by metis
  have "∀i. ∃j. f j > i"
  proof 
    fix i
    show "∃j. i < f j"
    proof(induction i)
      case 0
      then show ?case 
        by (metis f_Suc neq0_conv)
    next
      case (Suc i)
      then show ?case
        by (metis Suc_lessI f_Suc)
    qed
  qed
  then have "∃j. f j > card (UNIV :: ('c, 'l) transition set)"
    by auto
  then show False
    by (metis card_seteq f_def finite_UNIV le_eq_less_or_eq nat_neq_iff subset_UNIV)
qed

lemma saturation_termination:
  assumes "⋀ts ts' :: ('c ::finite, 'l::finite) transition set. rule ts ts' ⟹ card ts' = Suc (card ts)"
  shows "¬(∃tts. (∀i :: nat. rule (tts i) (tts (Suc i))))"
  using assms no_infinite by blast 

lemma saturation_exi: 
  assumes "⋀ts ts' :: ('c ::finite, 'l::finite) transition set. rule ts ts' ⟹ card ts' = Suc (card ts)"
  shows "∃ts'. saturation rule ts ts'"
proof (rule ccontr)
  assume a: "∄ts'. saturation rule ts ts'"
  define g where "g ts = (SOME ts'. rule ts ts')" for ts
  define tts where "tts i = (g ^^ i) ts" for i
  have "∀i :: nat. rule⇧*⇧* ts (tts i) ∧ rule (tts i) (tts (Suc i))"
  proof 
    fix i
    show "rule⇧*⇧* ts (tts i) ∧ rule (tts i) (tts (Suc i))"
    proof (induction i)
      case 0
      have "rule ts (g ts)"
        by (metis g_def a rtranclp.rtrancl_refl saturation_def saturated_def someI)
      then show ?case
        using tts_def a saturation_def by auto 
    next
      case (Suc i)
      then have sat_Suc: "rule⇧*⇧* ts (tts (Suc i))"
        by fastforce
      then have "rule (g ((g ^^ i) ts)) (g (g ((g ^^ i) ts)))"
        by (metis Suc.IH tts_def g_def a r_into_rtranclp rtranclp_trans saturation_def saturated_def 
            someI)
      then have "rule (tts (Suc i)) (tts (Suc (Suc i)))"
        unfolding tts_def by simp
      then show ?case
        using sat_Suc by auto
    qed
  qed
  then have "∀i. rule (tts i) (tts (Suc i))"
    by auto
  then show False
    using no_infinite assms by auto
qed


subsection ‹Saturation rules›

inductive pre_star_rule :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ (('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ bool" where 
  add_trans: "(p, γ) ↪ (p', w) ⟹ (Init p', lbl w, q) ∈ LTS.trans_star ts ⟹
    (Init p, γ, q) ∉ ts ⟹ pre_star_rule ts (ts ∪ {(Init p, γ, q)})"

definition pre_star1 :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ (('ctr_loc, 'noninit, 'label) state, 'label) transition set" where
  "pre_star1 ts =
    (⋃((p, γ), (p', w)) ∈ Δ. ⋃q ∈ LTS.reach ts (Init p') (lbl w). {(Init p, γ, q)})"

lemma pre_star1_mono: "mono pre_star1"
  unfolding pre_star1_def
  by (auto simp: mono_def LTS.trans_star_code[symmetric] elim!: bexI[rotated]
    LTS_trans_star_mono[THEN monoD, THEN subsetD])

lemma pre_star_rule_pre_star1:
  assumes "X ⊆ pre_star1 ts"
  shows "pre_star_rule⇧*⇧* ts (ts ∪ X)"
proof -
  have "finite X"
    by simp
  from this assms show ?thesis
  proof (induct X arbitrary: ts rule: finite_induct)
    case (insert x F)
    then obtain p γ p' w q where *: "(p, γ) ↪ (p', w)" 
      "(Init p', lbl w, q) ∈ LTS.trans_star ts" and x:
      "x = (Init p, γ, q)"
      by (auto simp: pre_star1_def is_rule_def LTS.trans_star_code)
    with insert show ?case
    proof (cases "(Init p, γ, q) ∈ ts")
      case False
      with insert(1,2,4) x show ?thesis
        by (intro converse_rtranclp_into_rtranclp[of pre_star_rule, OF add_trans[OF * False]])
          (auto intro!: insert(3)[of "insert x ts", simplified x Un_insert_left]
            intro: pre_star1_mono[THEN monoD, THEN set_mp, of ts])
    qed (simp add: insert_absorb)
  qed simp
qed

lemma pre_star_rule_pre_star1s: "pre_star_rule⇧*⇧* ts (((λs. s ∪ pre_star1 s) ^^ k) ts)"
  by (induct k) (auto elim!: rtranclp_trans intro: pre_star_rule_pre_star1)

definition "pre_star_loop = while_option (λs. s ∪ pre_star1 s ≠ s) (λs. s ∪ pre_star1 s)"
definition "pre_star_exec = the o pre_star_loop"
definition "pre_star_exec_check A = (if inits ⊆ LTS.srcs A then pre_star_loop A else None)"

definition "accept_pre_star_exec_check A c = (if inits ⊆ LTS.srcs A then Some (accepts (pre_star_exec A) c) else None)"

lemma while_option_finite_subset_Some: fixes C :: "'a set"
  assumes "mono f" and "!!X. X ⊆ C ⟹ f X ⊆ C" and "finite C" and X: "X ⊆ C" "X ⊆ f X"
  shows "∃P. while_option (λA. f A ≠ A) f X = Some P"
proof(rule measure_while_option_Some[where
    f= "%A::'a set. card C - card A" and P= "%A. A ⊆ C ∧ A ⊆ f A" and s= X])
  fix A assume A: "A ⊆ C ∧ A ⊆ f A" "f A ≠ A"
  show "(f A ⊆ C ∧ f A ⊆ f (f A)) ∧ card C - card (f A) < card C - card A"
    (is "?L ∧ ?R")
  proof
    show ?L by(metis A(1) assms(2) monoD[OF ‹mono f›])
    show ?R 
      by (metis A assms(2,3) card_seteq diff_less_mono2 equalityI linorder_le_less_linear 
          rev_finite_subset)
  qed
qed (simp add: X)

lemma pre_star_exec_terminates: "∃t. pre_star_loop s = Some t"
  unfolding pre_star_loop_def
  by (rule while_option_finite_subset_Some[where C=UNIV])
    (auto simp: mono_def dest: pre_star1_mono[THEN monoD])

lemma pre_star_exec_code[code]:
  "pre_star_exec s = (let s' = pre_star1 s in if s' ⊆ s then s else pre_star_exec (s ∪ s'))"
  unfolding pre_star_exec_def pre_star_loop_def o_apply
  by (subst while_option_unfold)(auto simp: Let_def)

lemma saturation_pre_star_exec: "saturation pre_star_rule ts (pre_star_exec ts)"
proof -
  from pre_star_exec_terminates obtain t where t: "pre_star_loop ts = Some t"
    by blast
  obtain k where k: "t = ((λs. s ∪ pre_star1 s) ^^ k) ts" and le: "pre_star1 t ⊆ t"
    using while_option_stop2[OF t[unfolded pre_star_loop_def]] by auto
  have "(⋃{us. pre_star_rule t us}) - t ⊆ pre_star1 t"
    by (auto simp: pre_star1_def LTS.trans_star_code[symmetric] prod.splits is_rule_def
      pre_star_rule.simps)
  from subset_trans[OF this le] show ?thesis
    unfolding saturation_def saturated_def pre_star_exec_def o_apply k t
    by (auto 9 0 simp: pre_star_rule_pre_star1s subset_eq pre_star_rule.simps)
qed

inductive post_star_rules :: "(('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ (('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ bool" where
  add_trans_pop: 
  "(p, γ) ↪ (p', pop) ⟹ 
   (Init p, [γ], q) ∈ LTS_ε.trans_star_ε ts ⟹ 
   (Init p', ε, q) ∉ ts ⟹ 
   post_star_rules ts (ts ∪ {(Init p', ε, q)})"
| add_trans_swap: 
  "(p, γ) ↪ (p', swap γ') ⟹ 
   (Init p, [γ], q) ∈ LTS_ε.trans_star_ε ts ⟹ 
   (Init p', Some γ', q) ∉ ts ⟹ 
   post_star_rules ts (ts ∪ {(Init p', Some γ', q)})"
| add_trans_push_1: 
  "(p, γ) ↪ (p', push γ' γ'') ⟹ 
   (Init p, [γ], q) ∈ LTS_ε.trans_star_ε ts ⟹ 
   (Init p', Some γ', Isolated p' γ') ∉ ts ⟹ 
   post_star_rules ts (ts ∪ {(Init p', Some γ', Isolated p' γ')})"
| add_trans_push_2: 
  "(p, γ) ↪ (p', push γ' γ'') ⟹ 
   (Init p, [γ], q) ∈ LTS_ε.trans_star_ε ts ⟹ 
   (Isolated p' γ', Some γ'', q) ∉ ts ⟹ 
   (Init p', Some γ', Isolated p' γ') ∈ ts ⟹ 
   post_star_rules ts (ts ∪ {(Isolated p' γ', Some γ'', q)})"

lemma pre_star_rule_mono:
  "pre_star_rule ts ts' ⟹ ts ⊂ ts'"
  unfolding pre_star_rule.simps by auto

lemma post_star_rules_mono:
  "post_star_rules ts ts' ⟹ ts ⊂ ts'"
proof(induction rule: post_star_rules.induct)
  case (add_trans_pop p γ p' q ts)
  then show ?case by auto
next
  case (add_trans_swap p γ p' γ' q ts)
  then show ?case by auto
next
  case (add_trans_push_1 p γ p' γ' γ'' q ts)
  then show ?case by auto
next
  case (add_trans_push_2 p γ p' γ' γ'' q ts)
  then show ?case by auto
qed

lemma pre_star_rule_card_Suc: "pre_star_rule ts ts' ⟹ card ts' = Suc (card ts)"
  unfolding pre_star_rule.simps by auto

lemma post_star_rules_card_Suc: "post_star_rules ts ts' ⟹ card ts' = Suc (card ts)"
proof(induction rule: post_star_rules.induct)
  case (add_trans_pop p γ p' q ts)
  then show ?case by auto
next
  case (add_trans_swap p γ p' γ' q ts)
  then show ?case by auto
next
  case (add_trans_push_1 p γ p' γ' γ'' q ts)
  then show ?case by auto
next
  case (add_trans_push_2 p γ p' γ' γ'' q ts)
  then show ?case by auto
qed


lemma pre_star_saturation_termination: 
  "¬(∃tts. (∀i :: nat. pre_star_rule (tts i) (tts (Suc i))))"
  using no_infinite pre_star_rule_card_Suc by blast 

lemma post_star_saturation_termination: 
  "¬(∃tts. (∀i :: nat. post_star_rules (tts i) (tts (Suc i))))"
  using no_infinite post_star_rules_card_Suc by blast

lemma pre_star_saturation_exi: 
  shows "∃ts'. saturation pre_star_rule ts ts'"
  using pre_star_rule_card_Suc saturation_exi by blast

lemma post_star_saturation_exi: 
  shows "∃ts'. saturation post_star_rules ts ts'"
  using post_star_rules_card_Suc saturation_exi by blast

lemma pre_star_rule_incr: "pre_star_rule A B ⟹ A ⊆ B"
proof(induction rule: pre_star_rule.inducts)
  case (add_trans p γ p' w q rel)
  then show ?case 
    by auto
qed

lemma post_star_rules_incr: "post_star_rules A B ⟹ A ⊆ B"
proof(induction rule: post_star_rules.inducts)
  case (add_trans_pop p γ p' q ts)
  then show ?case
    by auto
next
  case (add_trans_swap p γ p' γ' q ts)
  then show ?case 
    by auto
next
  case (add_trans_push_1 p γ p' γ' γ'' q ts)
  then show ?case 
    by auto
next
  case (add_trans_push_2 p γ p' γ' γ'' q ts)
  then show ?case 
    by auto
qed

lemma saturation_rtranclp_pre_star_rule_incr: "pre_star_rule⇧*⇧* A B ⟹ A ⊆ B"
proof (induction rule: rtranclp_induct)
  case base
  then show ?case by auto
next
  case (step y z)
  then show ?case
    using pre_star_rule_incr by auto
qed

lemma saturation_rtranclp_post_star_rule_incr: "post_star_rules⇧*⇧* A B ⟹ A ⊆ B"
proof (induction rule: rtranclp_induct)
  case base
  then show ?case by auto
next
  case (step y z)
  then show ?case
    using post_star_rules_incr by auto
qed

lemma pre_star'_incr_trans_star:
  "pre_star_rule⇧*⇧* A A' ⟹ LTS.trans_star A ⊆ LTS.trans_star A'"
  using mono_def LTS_trans_star_mono saturation_rtranclp_pre_star_rule_incr by metis

lemma post_star'_incr_trans_star:
  "post_star_rules⇧*⇧* A A' ⟹ LTS.trans_star A ⊆ LTS.trans_star A'"
  using mono_def LTS_trans_star_mono saturation_rtranclp_post_star_rule_incr by metis

lemma post_star'_incr_trans_star_ε:
  "post_star_rules⇧*⇧* A A' ⟹ LTS_ε.trans_star_ε A ⊆ LTS_ε.trans_star_ε A'"
  using mono_def LTS_ε_trans_star_ε_mono saturation_rtranclp_post_star_rule_incr by metis

lemma pre_star_lim'_incr_trans_star:
  "saturation pre_star_rule A A' ⟹ LTS.trans_star A ⊆ LTS.trans_star A'"
  by (simp add: pre_star'_incr_trans_star saturation_def)

lemma post_star_lim'_incr_trans_star:
  "saturation post_star_rules A A' ⟹ LTS.trans_star A ⊆ LTS.trans_star A'"
  by (simp add: post_star'_incr_trans_star saturation_def)

lemma post_star_lim'_incr_trans_star_ε:
  "saturation post_star_rules A A' ⟹ LTS_ε.trans_star_ε A ⊆ LTS_ε.trans_star_ε A'"
  by (simp add: post_star'_incr_trans_star_ε saturation_def)


subsection ‹Pre* lemmas›

lemma inits_srcs_iff_Ctr_Loc_srcs:
  "inits ⊆ LTS.srcs A ⟷ (∄q γ q'. (q, γ, Init q') ∈ A)"
proof 
  assume "inits ⊆ LTS.srcs A"
  then show "∄q γ q'. (q, γ, Init q') ∈ A"
    by (simp add: Collect_mono_iff LTS.srcs_def inits_def)
next
  assume "∄q γ q'. (q, γ, Init q') ∈ A"
  show "inits ⊆ LTS.srcs A"
    by (metis LTS.srcs_def2 inits_def ‹∄q γ q'. (q, γ, Init q') ∈ A› mem_Collect_eq 
        state.collapse(1) subsetI)
qed

lemma lemma_3_1:
  assumes "p'w ⇒⇧* pv"
  assumes "pv ∈ lang A"
  assumes "saturation pre_star_rule A A'"
  shows "accepts A' p'w"
  using assms
proof (induct rule: converse_rtranclp_induct)
  case base
  define p where "p = fst pv"
  define v where "v = snd pv"
  from base have "∃q ∈ finals. (Init p, v, q) ∈ LTS.trans_star A'"
    unfolding lang_def p_def v_def using pre_star_lim'_incr_trans_star accepts_def by fastforce 
  then show ?case
    unfolding accepts_def p_def v_def by auto
next
  case (step p'w p''u) 
  define p' where "p' = fst p'w"
  define w  where "w = snd p'w"
  define p'' where "p'' = fst p''u"
  define u  where "u = snd p''u"
  have p'w_def: "p'w = (p', w)"
    using p'_def w_def by auto
  have p''u_def: "p''u = (p'', u)"
    using p''_def u_def by auto

  then have "accepts A' (p'', u)" 
    using step by auto
  then obtain q where q_p: "q ∈ finals ∧ (Init p'', u, q) ∈ LTS.trans_star A'"
    unfolding accepts_def by auto
  have "∃γ w1 u1. w=γ#w1 ∧ u=lbl u1@w1 ∧ (p', γ) ↪ (p'', u1)"
    using p''u_def p'w_def step.hyps(1) step_relp_def2 by auto
  then obtain γ w1 u1 where γ_w1_u1_p: "w=γ#w1 ∧ u=lbl u1@w1 ∧ (p', γ) ↪ (p'', u1)"
    by blast

  then have "∃q1. (Init p'', lbl u1, q1) ∈ LTS.trans_star A' ∧ (q1, w1, q) ∈ LTS.trans_star A'"
    using q_p LTS.trans_star_split by auto

  then obtain q1 where q1_p: "(Init p'', lbl u1, q1) ∈ LTS.trans_star A' ∧ (q1, w1, q) ∈ LTS.trans_star A'"
    by auto

  then have in_A': "(Init p', γ, q1) ∈ A'"
    using γ_w1_u1_p add_trans[of p' γ p'' u1 q1 A'] saturated_def saturation_def step.prems by metis

  then have "(Init p', γ#w1, q) ∈ LTS.trans_star A'"
    using LTS.trans_star.trans_star_step q1_p by meson
  then have t_in_A': "(Init p', w, q) ∈ LTS.trans_star A'"
    using γ_w1_u1_p by blast

  from q_p t_in_A' have "q ∈ finals ∧ (Init p', w, q) ∈ LTS.trans_star A'"
    by auto
  then show ?case
    unfolding accepts_def p'w_def by auto 
qed

lemma word_into_init_empty_states:
  fixes A :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set"
  assumes "(p, w, ss, Init q) ∈ LTS.trans_star_states A"
  assumes "inits ⊆ LTS.srcs A"
  shows "w = [] ∧ p = Init q ∧ ss=[p]"
proof -
  define q1 :: "('ctr_loc, 'noninit, 'label) state" where 
    "q1 = Init q"
  have q1_path: "(p, w, ss, q1) ∈ LTS.trans_star_states A"
    by (simp add: assms(1) q1_def)
  moreover
  have "q1 ∈ inits"
    by (simp add: inits_def q1_def)
  ultimately
  have "w = [] ∧ p = q1 ∧ ss=[p]"
  proof(induction rule: LTS.trans_star_states.induct[OF q1_path])
    case (1 p)
    then show ?case by auto
  next
    case (2 p γ q' w ss q)
    have "∄q γ q'. (q, γ, Init q') ∈ A"
      using assms(2) unfolding inits_def LTS.srcs_def by (simp add: Collect_mono_iff) 
    then show ?case
      using 2 assms(2) by (metis inits_def is_Init_def mem_Collect_eq)
  qed
  then show ?thesis
    using q1_def by fastforce
qed

(* This corresponds to and slightly generalizes Schwoon's lemma 3.2(b) *)
lemma word_into_init_empty:
  fixes A :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition set"
  assumes "(p, w, Init q) ∈ LTS.trans_star A"
  assumes "inits ⊆ LTS.srcs A"
  shows "w = [] ∧ p = Init q"
  using assms word_into_init_empty_states LTS.trans_star_trans_star_states by metis

lemma step_relp_append_aux:
  assumes "pu ⇒⇧* p1y"
  shows "(fst pu, snd pu @ v) ⇒⇧* (fst p1y, snd p1y @ v)"
  using assms 
proof (induction rule: rtranclp_induct)
  case base
  then show ?case by auto
next
  case (step p'w p1y)
  define p where "p = fst pu"
  define u where "u = snd pu"
  define p' where "p' = fst p'w"
  define w where "w = snd p'w"
  define p1 where "p1 = fst p1y"
  define y where "y = snd p1y"
  have step_1: "(p,u) ⇒⇧* (p',w)"
    by (simp add: p'_def p_def step.hyps(1) u_def w_def)
  have step_2: "(p',w) ⇒ (p1,y)"
    by (simp add: p'_def p1_def step.hyps(2) w_def y_def)
  have step_3: "(p, u @ v) ⇒⇧* (p', w @ v)"
    by (simp add: p'_def p_def step.IH u_def w_def)

  note step' = step_1 step_2 step_3

  from step'(2) have "∃γ w' wa. w = γ # w' ∧ y = lbl wa @ w' ∧ (p', γ) ↪ (p1, wa)"
    using step_relp_def2[of p' w p1 y] by auto
  then obtain γ w' wa where γ_w'_wa_p: " w = γ # w' ∧ y = lbl wa @ w' ∧ (p', γ) ↪ (p1, wa)"
    by metis
  then have "(p, u @ v) ⇒⇧* (p1, y @ v)"
    by (metis (no_types, lifting) PDS.step_relp_def2 append.assoc append_Cons rtranclp.simps step_3)
  then show ?case
    by (simp add: p1_def p_def u_def y_def)
qed

lemma step_relp_append:
  assumes "(p, u) ⇒⇧* (p1, y)"
  shows "(p, u @ v) ⇒⇧* (p1, y @ v)"
  using assms step_relp_append_aux by auto

lemma step_relp_append_empty:
  assumes "(p, u) ⇒⇧* (p1, [])"
  shows "(p, u @ v) ⇒⇧* (p1, v)"
  using step_relp_append[OF assms] by auto

lemma lemma_3_2_a':
  assumes "inits ⊆ LTS.srcs A"
  assumes "pre_star_rule⇧*⇧* A A'"
  assumes "(Init p, w, q) ∈ LTS.trans_star A'"
  shows "∃p' w'. (Init p', w', q) ∈ LTS.trans_star A ∧ (p, w) ⇒⇧* (p', w')"
  using assms(2) assms(3)
proof (induction arbitrary: p q w rule: rtranclp_induct)
  case base
  then have "(Init p, w, q) ∈ LTS.trans_star A ∧ (p, w) ⇒⇧* (p, w)"
    by auto
  then show ?case
    by auto
next
  case (step Aiminus1 Ai)

  from step(2) obtain p1 γ p2 w2 q' where p1_γ_p2_w2_q'_p:
    "Ai = Aiminus1 ∪ {(Init p1, γ, q')}"
    "(p1, γ) ↪ (p2, w2)"
    "(Init p2, lbl w2, q') ∈ LTS.trans_star Aiminus1"
    "(Init p1, γ, q') ∉ Aiminus1"
    by (meson pre_star_rule.cases)

  define t :: "(('ctr_loc, 'noninit, 'label) state, 'label) transition"
    where "t = (Init p1, γ, q')"

  obtain ss where ss_p: "(Init p, w, ss, q) ∈ LTS.trans_star_states Ai"
    using step(4) LTS.trans_star_trans_star_states by metis

  define j where "j = count (transitions_of' (Init p, w, ss, q)) t"

  from j_def ss_p show ?case
  proof (induction j arbitrary: p q w ss)
    case 0
    then have "(Init p, w, q) ∈ LTS.trans_star Aiminus1"
      using count_zero_remove_trans_star_states_trans_star p1_γ_p2_w2_q'_p(1) t_def by metis
    then show ?case
      using step.IH by metis
  next
    case (Suc j')
    have "∃u v u_ss v_ss.
            ss = u_ss@v_ss ∧ w = u@[γ]@v ∧
            (Init p,u,u_ss, Init p1) ∈ LTS.trans_star_states Aiminus1 ∧
            (Init p1,[γ],q') ∈ LTS.trans_star Ai ∧
            (q',v,v_ss,q) ∈ LTS.trans_star_states Ai ∧
            (Init p, w, ss, q) = ((Init p, u, u_ss, Init p1), γ) @@⇧γ (q', v, v_ss, q)"
      using split_at_first_t[of "Init p" w ss q Ai j' "Init p1" γ q' Aiminus1]
      using Suc(2,3) t_def  p1_γ_p2_w2_q'_p(1,4) t_def by auto
    then obtain u v u_ss v_ss where u_v_u_ss_v_ss_p:
      "ss = u_ss@v_ss ∧ w = u@[γ]@v"
      "(Init p,u,u_ss, Init p1) ∈ LTS.trans_star_states Aiminus1"
      "(Init p1,[γ],q') ∈ LTS.trans_star Ai"
      "(q',v,v_ss,q) ∈ LTS.trans_star_states Ai"
      "(Init p, w, ss, q) = ((Init p, u, u_ss, Init p1), γ) @@⇧γ (q', v, v_ss, q)"
      by blast
    from this(2) have "∃p'' w''. (Init p'', w'', Init p1) ∈ LTS.trans_star A ∧ (p, u) ⇒⇧* (p'', w'')"
      using Suc(1)[of p u _ "Init p1"] step.IH step.prems(1)
      by (meson LTS.trans_star_states_trans_star LTS.trans_star_trans_star_states) 
    from this this(1) have VIII: "(p, u) ⇒⇧* (p1, [])"
      using word_into_init_empty assms(1) by blast

    note IX = p1_γ_p2_w2_q'_p(2)
    note III = p1_γ_p2_w2_q'_p(3)
    from III have III_2: "∃w2_ss. (Init p2, lbl w2, w2_ss, q') ∈ LTS.trans_star_states Aiminus1"
      using LTS.trans_star_trans_star_states[of "Init p2" "lbl w2" q' Aiminus1] by auto
    then obtain w2_ss where III_2: "(Init p2, lbl w2, w2_ss, q') ∈ LTS.trans_star_states Aiminus1"
      by blast

    from III have V: 
      "(Init p2, lbl w2, w2_ss, q') ∈ LTS.trans_star_states Aiminus1" 
      "(q', v, v_ss, q) ∈ LTS.trans_star_states Ai"
      using III_2 ‹(q', v, v_ss, q) ∈ LTS.trans_star_states Ai› by auto

    define w2v where "w2v = lbl w2 @ v"
    define w2v_ss where "w2v_ss = w2_ss @ tl v_ss"

    from V(1) have "(Init p2, lbl w2, w2_ss, q') ∈ LTS.trans_star_states Ai"
      using trans_star_states_mono p1_γ_p2_w2_q'_p(1) using Un_iff subsetI by (metis (no_types))
    then have V_merged: "(Init p2, w2v, w2v_ss, q) ∈ LTS.trans_star_states Ai"
      using V(2) unfolding w2v_def w2v_ss_def by (meson LTS.trans_star_states_append)

    have j'_count: "j' = count (transitions_of' (Init p2, w2v, w2v_ss, q)) t"
    proof -
      define countts where
        "countts == λx. count (transitions_of' x) t"

      have "countts (Init p, w, ss, q) = Suc j' "
        using Suc.prems(1) countts_def by force
      moreover
      have "countts (Init p, u, u_ss, Init p1) = 0"
        using LTS.avoid_count_zero countts_def p1_γ_p2_w2_q'_p(4) t_def u_v_u_ss_v_ss_p(2) 
        by fastforce
      moreover
      from u_v_u_ss_v_ss_p(5) have "countts (Init p, w, ss, q) = countts (Init p, u, u_ss, Init p1) + 1 + countts (q', v, v_ss, q)"
        using count_combine_trans_star_states countts_def t_def u_v_u_ss_v_ss_p(2) 
          u_v_u_ss_v_ss_p(4) by fastforce
      ultimately
      have "Suc j' = 0 + 1 + countts (q', v, v_ss, q)"
        by auto
      then have "j' = countts (q', v, v_ss, q)"
        by auto
      moreover
      have "countts (Init p2, lbl w2, w2_ss, q') = 0"
        using III_2 LTS.avoid_count_zero countts_def p1_γ_p2_w2_q'_p(4) t_def by fastforce
      moreover
      have "(Init p2, w2v, w2v_ss, q) = (Init p2, lbl w2, w2_ss, q') @@´ (q', v, v_ss, q)"
        using w2v_def w2v_ss_def by auto
      then have "countts (Init p2, w2v, w2v_ss, q) = countts (Init p2, lbl w2, w2_ss, q') + countts (q', v, v_ss, q)"
        using ‹(Init p2, lbl w2, w2_ss, q') ∈ LTS.trans_star_states Ai› 
          count_append_trans_star_states countts_def t_def u_v_u_ss_v_ss_p(4) by fastforce
      ultimately
      show ?thesis
        by (simp add: countts_def)
    qed

    have "∃p' w'. (Init p', w', q) ∈ LTS.trans_star A ∧ (p2, w2v) ⇒⇧* (p', w')"
      using Suc(1) using j'_count V_merged by auto
    then obtain p' w' where p'_w'_p: "(Init p', w', q) ∈ LTS.trans_star A" "(p2, w2v) ⇒⇧* (p', w')"
      by blast

    note X = p'_w'_p(2)

    have "(p,w) = (p,u@[γ]@v)"
      using ‹ss = u_ss @ v_ss ∧ w = u @ [γ] @ v› by blast

    have "(p,u@[γ]@v) ⇒⇧* (p1,γ#v)"
      using VIII step_relp_append_empty by auto

    from X have "(p1,γ#v) ⇒ (p2, w2v)"
      by (metis IX LTS.step_relp_def transition_rel.intros w2v_def)

    from X have
      "(p2, w2v) ⇒⇧* (p', w')"
      by simp

    have "(p, w) ⇒⇧* (p', w')"
      using X ‹(p, u @ [γ] @ v) ⇒⇧* (p1, γ # v)› ‹(p, w) = (p, u @ [γ] @ v)› ‹(p1, γ # v) ⇒ (p2, w2v)› by auto

    then have "(Init p', w', q) ∈ LTS.trans_star A ∧ (p, w) ⇒⇧* (p', w')"
      using p'_w'_p(1) by auto
    then show ?case
      by metis
  qed
qed 

lemma lemma_3_2_a:
  assumes "inits ⊆ LTS.srcs A"
  assumes "saturation pre_star_rule A A'"
  assumes "(Init p, w, q) ∈ LTS.trans_star A'"
  shows "∃p' w'. (Init p', w', q) ∈ LTS.trans_star A ∧ (p, w) ⇒⇧* (p', w')"
  using assms lemma_3_2_a' saturation_def by metis

― ‹Corresponds to one direction of Schwoon's theorem 3.2›
theorem pre_star_rule_subset_pre_star_lang:
  assumes "inits ⊆ LTS.srcs A"
  assumes "pre_star_rule⇧*⇧* A A'"
  shows "{c. accepts A' c} ⊆ pre_star (lang A)"
proof
  fix c :: "'ctr_loc × 'label list"
  assume c_a: "c ∈ {w. accepts A' w}"
  define p where "p = fst c"
  define w where "w = snd c"
  from p_def w_def c_a have "accepts A' (p,w)"
    by auto
  then have "∃q ∈ finals. (Init p, w, q) ∈ LTS.trans_star A'"
    unfolding accepts_def by auto
  then obtain q where q_p: "q ∈ finals" "(Init p, w, q) ∈ LTS.trans_star A'"
    by auto
  then have "∃p' w'. (p,w) ⇒⇧* (p',w') ∧ (Init p', w', q) ∈ LTS.trans_star A"
    using lemma_3_2_a' assms(1) assms(2) by metis
  then obtain p' w' where p'_w'_p: "(p,w) ⇒⇧* (p',w')" "(Init p', w', q) ∈ LTS.trans_star A"
    by auto
  then have "(p', w') ∈ lang A"
    unfolding lang_def unfolding accepts_def using q_p(1) by auto
  then have "(p,w) ∈ pre_star (lang A)"
    unfolding pre_star_def using p'_w'_p(1) by auto
  then show "c ∈ pre_star (lang A)"
    unfolding p_def w_def by auto
qed

― ‹Corresponds to Schwoon's theorem 3.2›
theorem pre_star_rule_accepts_correct:
  assumes "inits ⊆ LTS.srcs A"
  assumes "saturation pre_star_rule A A'"
  shows "{c. accepts A' c} = pre_star (lang A)"
proof (rule; rule)
  fix c :: "'ctr_loc × 'label list"
  define p where "p = fst c"
  define w where "w = snd c"
  assume "c ∈ pre_star (lang A)"
  then have "(p,w) ∈ pre_star (lang A)"
    unfolding p_def w_def by auto
  then have "∃p' w'. (p',w') ∈ lang A ∧ (p,w) ⇒⇧* (p',w')"
    unfolding pre_star_def by force
  then obtain p' w' where "(p',w') ∈ lang A ∧ (p,w) ⇒⇧* (p',w')"
    by auto
  then have "∃q ∈ finals. (Init p, w, q) ∈ LTS.trans_star A'"
    using lemma_3_1 assms(2) unfolding accepts_def by force
  then have "accepts A' (p,w)"
    unfolding accepts_def by auto
  then show "c ∈ {c. accepts A' c}"
    using p_def w_def by auto
next
  fix c :: "'ctr_loc × 'label list"
  assume "c ∈ {w. accepts A' w}"
  then show "c ∈ pre_star (lang A)"
    using pre_star_rule_subset_pre_star_lang assms unfolding saturation_def by auto
qed

― ‹Corresponds to Schwoon's theorem 3.2›
theorem pre_star_rule_correct:
  assumes "inits ⊆ LTS.srcs A"
  assumes "saturation pre_star_rule A A'"
  shows "lang A' = pre_star (lang A)"
  using assms(1) assms(2) lang_def pre_star_rule_accepts_correct by auto

theorem pre_star_exec_accepts_correct:
  assumes "inits ⊆ LTS.srcs A"
  shows "{c. accepts (pre_star_exec A) c} = pre_star (lang A)"
  using pre_star_rule_accepts_correct[of A "pre_star_exec A"] saturation_pre_star_exec[of A] 
    assms by auto

theorem pre_star_exec_lang_correct:
  assumes "inits ⊆ LTS.srcs A"
  shows "lang (pre_star_exec A) = pre_star (lang A)"
  using pre_star_rule_correct[of A "pre_star_exec A"] saturation_pre_star_exec[of A] assms by auto

theorem pre_star_exec_check_accepts_correct:
  assumes "pre_star_exec_check A ≠ None"
  shows "{c. accepts (the (pre_star_exec_check A)) c} = pre_star (lang A)"
  using pre_star_exec_accepts_correct assms unfolding pre_star_exec_check_def pre_star_exec_def
  by (auto split: if_splits)

theorem pre_star_exec_check_correct:
  assumes "pre_star_exec_check A ≠ None"
  shows "lang (the (pre_star_exec_check A)) = pre_star (lang A)"
  using pre_star_exec_check_accepts_correct assms unfolding lang_def by auto

theorem accept_pre_star_exec_correct_True:
  assumes "inits ⊆ LTS.srcs A"
  assumes "accepts (pre_star_exec A) c"
  shows "c ∈ pre_star (lang A)"
  using pre_star_exec_accepts_correct assms(1) assms(2) by blast

theorem accept_pre_star_exec_correct_False:
  assumes "inits ⊆ LTS.srcs A"
  assumes "¬accepts (pre_star_exec A) c"
  shows "c ∉ pre_star (lang A)"
  using pre_star_exec_accepts_correct assms(1) assms(2) by blast

theorem accept_pre_star_exec_correct_Some_True:
  assumes "accept_pre_star_exec_check A c = Some True"
  shows "c ∈ pre_star (lang A)"
proof -
  have "inits ⊆ LTS.srcs A"
    using assms unfolding accept_pre_star_exec_check_def
    by (auto split: if_splits)
  moreover
  have "accepts (pre_star_exec A) c"
    using assms
    using accept_pre_star_exec_check_def calculation by auto
  ultimately
  show "c ∈ pre_star (lang A)"
    using accept_pre_star_exec_correct_True by auto
qed

theorem accept_pre_star_exec_correct_Some_False:
  assumes "accept_pre_star_exec_check A c = Some False"
  shows "c ∉ pre_star (lang A)"
proof -
  have "inits ⊆ LTS.srcs A"
    using assms unfolding accept_pre_star_exec_check_def
    by (auto split: if_splits)
  moreover
  have "¬accepts (pre_star_exec A) c"
    using assms
    using accept_pre_star_exec_check_def calculation by auto
  ultimately
  show "c ∉ pre_star (lang A)"
    using accept_pre_star_exec_correct_False by auto
qed

theorem accept_pre_star_exec_correct_None:
  assumes "accept_pre_star_exec_check A c = None"
  shows "¬inits ⊆ LTS.srcs A"
  using assms unfolding accept_pre_star_exec_check_def by auto


subsection ‹Post* lemmas›

lemma lemma_3_3':
  assumes "pv ⇒⇧* p'w"
    and "(fst pv, snd pv) ∈ lang_ε A"
    and "saturation post_star_rules A A'"
  shows "accepts_ε A' (fst p'w, snd p'w)"
  using assms
proof (induct arbitrary: pv rule: rtranclp_induct)
  case base
  show ?case
    using assms post_star_lim'_incr_trans_star_ε
    by (auto simp: lang_ε_def accepts_ε_def)
next
  case (step p''u p'w)
  define p' where "p' = fst p'w"
  define w  where "w = snd p'w"
  define p'' where "p'' = fst p''u"
  define u  where "u = snd p''u"
  have p'w_def: "p'w = (p', w)"
    using p'_def w_def by auto
  have p''u_def: "p''u = (p'', u)"
    using p''_def u_def by auto

  then have "accepts_ε A' (p'', u)"
    using assms(2) p''_def step.hyps(3) step.prems(2) u_def by metis
  then have "∃q. q ∈ finals ∧ (Init p'', u, q) ∈ LTS_ε.trans_star_ε A'"
    by (auto simp: accepts_ε_def)
  then obtain q where q_p: "q ∈ finals ∧ (Init p'', u, q) ∈ LTS_ε.trans_star_ε A'"
    by metis
  then have "∃u_ε. q ∈ finals ∧ LTS_ε.ε_exp u_ε u ∧ (Init p'', u_ε, q) ∈ LTS.trans_star A'"
    using LTS_ε.trans_star_ε_iff_ε_exp_trans_star[of "Init p''" u q A'] by auto
  then obtain u_ε where II: "q ∈ finals" "LTS_ε.ε_exp u_ε u" "(Init p'', u_ε, q) ∈ LTS.trans_star A'"
    by blast
  have "∃γ u1 w1. u=γ#u1 ∧ w=lbl w1@u1 ∧ (p'', γ) ↪ (p', w1)"
    using p''u_def p'w_def step.hyps(2) step_relp_def2 by auto
  then obtain γ u1 w1 where III: "u=γ#u1" "w=lbl w1@u1" "(p'', γ) ↪ (p', w1)"
    by blast

  have p'_inits: "Init p' ∈ inits"
    unfolding inits_def by auto
  have p''_inits: "Init p'' ∈ inits"
    unfolding inits_def by auto

  have "∃γ_ε u1_ε. LTS_ε.ε_exp γ_ε [γ] ∧ LTS_ε.ε_exp u1_ε u1 ∧ (Init p'', γ_ε@u1_ε, q) ∈ LTS.trans_star A'"
  proof -
    have "∃γ_ε u1_ε. LTS_ε.ε_exp γ_ε [γ] ∧ LTS_ε.ε_exp u1_ε u1 ∧ u_ε = γ_ε @ u1_ε" 
      using LTS_ε.ε_exp_split'[of u_ε γ u1] II(2) III(1) by auto
    then obtain γ_ε u1_ε where "LTS_ε.ε_exp γ_ε [γ] ∧ LTS_ε.ε_exp u1_ε u1 ∧ u_ε = γ_ε @ u1_ε" 
      by auto
    then have "(Init p'', γ_ε@u1_ε , q) ∈ LTS.trans_star A'"
      using II(3) by auto
    then show ?thesis
      using ‹LTS_ε.ε_exp γ_ε [γ] ∧ LTS_ε.ε_exp u1_ε u1 ∧ u_ε = γ_ε @ u1_ε› by blast
  qed
  then obtain γ_ε u1_ε where 
    iii: "LTS_ε.ε_exp γ_ε [γ]" and 
    iv: "LTS_ε.ε_exp u1_ε u1" "(Init p'', γ_ε@u1_ε, q) ∈ LTS.trans_star A'"
    by blast
  then have VI: "∃q1. (Init p'', γ_ε, q1) ∈ LTS.trans_star A' ∧ (q1, u1_ε, q) ∈ LTS.trans_star A'"
    by (simp add: LTS.trans_star_split)
  then obtain q1 where VI: "(Init p'', γ_ε, q1) ∈ LTS.trans_star A'" "(q1, u1_ε, q) ∈ LTS.trans_star A'"
    by blast

  then have VI_2: "(Init p'', [γ], q1) ∈ LTS_ε.trans_star_ε A'" "(q1, u1, q) ∈ LTS_ε.trans_star_ε A'"
    by (meson LTS_ε.trans_star_ε_iff_ε_exp_trans_star iii VI(2) iv(1))+

  show ?case
  proof (cases w1)
    case pop
    then have r: "(p'', γ) ↪ (p', pop)"
      using III(3) by blast
    then have "(Init p', ε, q1) ∈ A'"
      using VI_2(1) add_trans_pop assms saturated_def saturation_def p'_inits by metis
    then have "(Init p', w, q) ∈ LTS_ε.trans_star_ε A'"
      using III(2) VI_2(2) pop LTS_ε.trans_star_ε.trans_star_ε_step_ε by fastforce
    then have "accepts_ε A' (p', w)"
      unfolding accepts_ε_def using II(1) by blast
    then show ?thesis
      using p'_def w_def by force
  next
    case (swap γ')
    then have r: "(p'', γ) ↪ (p', swap γ')"
      using III(3) by blast
    then have "(Init p', Some γ', q1) ∈ A'"
      by (metis VI_2(1) add_trans_swap assms(3) saturated_def saturation_def)
    have "(Init p', w, q) ∈ LTS_ε.trans_star_ε A'"
      using III(2) LTS_ε.trans_star_ε.trans_star_ε_step_γ VI_2(2) append_Cons append_self_conv2 
        lbl.simps(3) swap ‹(Init p', Some γ', q1) ∈ A'› by fastforce
    then have "accepts_ε A' (p', w)"
      unfolding accepts_ε_def
      using II(1) by blast
    then show ?thesis
      using p'_def w_def by force
  next
    case (push γ' γ'')
    then have r: "(p'', γ) ↪ (p', push γ' γ'')"
      using III(3) by blast
    from this VI_2 iii post_star_rules.intros(3)[OF this, of q1 A', OF VI_2(1)] 
    have "(Init p', Some γ', Isolated p' γ') ∈ A'"
      using assms(3) by (meson saturated_def saturation_def) 
    from this r VI_2 iii post_star_rules.intros(4)[OF r, of q1 A', OF VI_2(1)] 
    have "(Isolated p' γ', Some γ'', q1) ∈ A'"
      using assms(3) using saturated_def saturation_def by metis
    have "(Init p', [γ'], Isolated p' γ') ∈ LTS_ε.trans_star_ε A' ∧
          (Isolated p' γ', [γ''], q1) ∈ LTS_ε.trans_star_ε A' ∧
          (q1, u1, q) ∈ LTS_ε.trans_star_ε A'"
      by (metis LTS_ε.trans_star_ε.simps VI_2(2) ‹(Init p', Some γ', Isolated p' γ') ∈ A'› 
          ‹(Isolated p' γ', Some γ'', q1) ∈ A'›)
    have "(Init p', w, q) ∈ LTS_ε.trans_star_ε A'"
      using III(2) VI_2(2) ‹(Init p', Some γ', Isolated p' γ') ∈ A'› 
        ‹(Isolated p' γ', Some γ'', q1) ∈ A'› push LTS_ε.append_edge_edge_trans_star_ε by auto
    then have "accepts_ε A' (p', w)"
      unfolding accepts_ε_def
      using II(1) by blast
    then show ?thesis
      using p'_def w_def by force

  qed
qed

lemma lemma_3_3:
  assumes "(p,v) ⇒⇧* (p',w)"
  and "(p, v) ∈ lang_ε A"
  and "saturation post_star_rules A A'"
  shows "accepts_ε A' (p', w)"
  using assms lemma_3_3' by force

lemma init_only_hd:
  assumes "(ss, w) ∈ LTS.path_with_word A"
  assumes "inits ⊆ LTS.srcs A"
  assumes "count (transitions_of (ss, w)) t > 0"
  assumes "t = (Init p1, γ, q1)"
  shows "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
  using assms LTS.source_only_hd by (metis LTS.srcs_def2 inits_srcs_iff_Ctr_Loc_srcs)

lemma no_edge_to_Ctr_Loc_avoid_Ctr_Loc:
  assumes "(p, w, qq) ∈ LTS.trans_star Aiminus1"
  assumes "w ≠ []"
  assumes "inits ⊆ LTS.srcs Aiminus1"
  shows "qq ∉ inits"
  using assms LTS.no_end_in_source by (metis subset_iff)

lemma no_edge_to_Ctr_Loc_avoid_Ctr_Loc_ε:
  assumes "(p, [γ], qq) ∈ LTS_ε.trans_star_ε Aiminus1"
  assumes "inits ⊆ LTS.srcs Aiminus1"
  shows "qq ∉ inits"
  using assms LTS_ε.no_edge_to_source_ε by (metis subset_iff)

lemma no_edge_to_Ctr_Loc_post_star_rules':
  assumes "post_star_rules⇧*⇧* A Ai"
  assumes "∄q γ q'. (q, γ, Init q') ∈ A"
  shows "∄q γ q'. (q, γ, Init q') ∈ Ai"
using assms 
proof (induction rule: rtranclp_induct)
  case base
  then show ?case by auto
next
  case (step Aiminus1 Ai)
  then have ind: "∄q γ q'. (q, γ, Init q') ∈ Aiminus1"
    by auto
  from step(2) show ?case
  proof (cases rule: post_star_rules.cases)
    case (add_trans_pop p γ p' q)
    have "q ∉ inits"
      using ind no_edge_to_Ctr_Loc_avoid_Ctr_Loc_ε inits_srcs_iff_Ctr_Loc_srcs
      by (metis local.add_trans_pop(3))
    then have "∄qq. q = Init qq"
      by (simp add: inits_def is_Init_def)
    then show ?thesis
      using ind local.add_trans_pop(1) by auto
  next
    case (add_trans_swap p γ p' γ' q)
    have "q ∉ inits"
      using add_trans_swap ind no_edge_to_Ctr_Loc_avoid_Ctr_Loc_ε inits_srcs_iff_Ctr_Loc_srcs 
      by metis
    then have "∄qq. q = Init qq"
      by (simp add: inits_def is_Init_def)
    then show ?thesis
      using ind local.add_trans_swap(1) by auto
  next
    case (add_trans_push_1 p γ p' γ' γ'' q)
    have "q ∉ inits"
      using add_trans_push_1 ind no_edge_to_Ctr_Loc_avoid_Ctr_Loc_ε inits_srcs_iff_Ctr_Loc_srcs 
      by metis
    then have "∄qq. q = Init qq"
      by (simp add: inits_def is_Init_def)
    then show ?thesis
      using ind local.add_trans_push_1(1) by auto
  next
    case (add_trans_push_2 p γ p' γ' γ'' q)
    have "q ∉ inits"
      using add_trans_push_2 ind no_edge_to_Ctr_Loc_avoid_Ctr_Loc_ε inits_srcs_iff_Ctr_Loc_srcs 
      by metis
    then have "∄qq. q = Init qq"
      by (simp add: inits_def is_Init_def)
    then show ?thesis
      using ind local.add_trans_push_2(1) by auto
  qed
qed

lemma no_edge_to_Ctr_Loc_post_star_rules:
  assumes "post_star_rules⇧*⇧* A Ai"
  assumes "inits ⊆ LTS.srcs A"
  shows "inits ⊆ LTS.srcs Ai"
  using assms no_edge_to_Ctr_Loc_post_star_rules' inits_srcs_iff_Ctr_Loc_srcs by metis

lemma source_and_sink_isolated:
  assumes "N ⊆ LTS.srcs A"
  assumes "N ⊆ LTS.sinks A"
  shows "∀p γ q. (p, γ, q) ∈ A ⟶ p ∉ N ∧ q ∉ N"
  by (metis LTS.srcs_def2 LTS.sinks_def2 assms(1) assms(2) in_mono)

lemma post_star_rules_Isolated_source_invariant':
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p', Some γ', Isolated p' γ') ∉ A'"
  shows "∄p γ. (p, γ, Isolated p' γ') ∈ A'"
  using assms 
proof (induction rule: rtranclp_induct)
  case base
  then show ?case 
    unfolding isols_def is_Isolated_def using LTS.isolated_no_edges by fastforce
next
  case (step Aiminus1 Ai)
  from step(2) show ?case
  proof (cases rule: post_star_rules.cases)
    case (add_trans_pop p''' γ'' p'' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then have nin: "∄p γ. (p, γ, Isolated p' γ') ∈ Aiminus1"
      using local.add_trans_pop(1) step.IH step.prems(1,2) by fastforce
    then have "Isolated p' γ' ≠ q"
      using add_trans_pop(4) LTS_ε.trans_star_not_to_source_ε LTS.srcs_def2
      by (metis local.add_trans_pop(3) state.distinct(3))
    then have "∄p γ. (p, γ, Isolated p' γ') = (Init p'', ε, q)"
      by auto
    then show ?thesis
      using nin add_trans_pop(1) by auto
  next
    case (add_trans_swap p'''' γ'' p'' γ''' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then have nin: "∄p γ. (p, γ, Isolated p' γ') ∈ Aiminus1"
      using local.add_trans_swap(1) step.IH step.prems(1,2) by fastforce
    then have "Isolated p' γ' ≠ q"
      using LTS.srcs_def2 
      by (metis state.distinct(4) LTS_ε.trans_star_not_to_source_ε local.add_trans_swap(3)) 
    then have "∄p γ. (p, γ, Isolated p' γ') = (Init p'', Some γ''', q)"
      by auto
    then show ?thesis
      using nin add_trans_swap(1) by auto
  next
    case (add_trans_push_1 p'''' γ'' p'' γ''' γ''''' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then show ?thesis
      using add_trans_push_1(1) Un_iff state.inject(2) prod.inject singleton_iff step.IH 
        step.prems(1,2) by blast 
  next
    case (add_trans_push_2 p'''' γ'' p'' γ''' γ'''' q)
    have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) .
    then have nin: "∄p γ. (p, γ, Isolated p' γ') ∈ Aiminus1"
      using local.add_trans_push_2(1) step.IH step.prems(1) by fastforce
    then have "Isolated p' γ' ≠ q"
      using LTS.srcs_def2 local.add_trans_push_2(3) 
      by (metis state.disc(1,3) LTS_ε.trans_star_not_to_source_ε)
    then have "∄p γ. (p, γ, Isolated p' γ') = (Init p'', ε, q)"
      by auto
    then show ?thesis
      using nin add_trans_push_2(1) by auto
  qed
qed

lemma post_star_rules_Isolated_source_invariant:
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p', Some γ', Isolated p' γ') ∉ A'"
  shows "Isolated p' γ' ∈ LTS.srcs A'"
  by (meson LTS.srcs_def2 assms(1) assms(2) assms(3) post_star_rules_Isolated_source_invariant')

lemma post_star_rules_Isolated_sink_invariant':
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p', Some γ', Isolated p' γ') ∉ A'"
  shows "∄p γ. (Isolated p' γ', γ, p) ∈ A'"
  using assms 
proof (induction rule: rtranclp_induct)
  case base
  then show ?case
    unfolding isols_def is_Isolated_def
    using LTS.isolated_no_edges by fastforce  
next
  case (step Aiminus1 Ai)
  from step(2) show ?case
  proof (cases rule: post_star_rules.cases)
    case (add_trans_pop p''' γ'' p'' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then have nin: "∄p γ. (Isolated p' γ', γ, p) ∈ Aiminus1"
      using local.add_trans_pop(1) step.IH step.prems(1,2) by fastforce
    then have "Isolated p' γ' ≠ q"
      using add_trans_pop(4) 
        LTS_ε.trans_star_not_to_source_ε[of "Init p'''" "[γ'']" q Aiminus1 "Isolated p' γ'"]
        post_star_rules_Isolated_source_invariant local.add_trans_pop(1) step.hyps(1) step.prems(1,2)
        UnI1 local.add_trans_pop(3) by (metis (full_types) state.distinct(3))
    then have "∄p γ. (p, γ, Isolated p' γ') = (Init p'', ε, q)"
      by auto
    then show ?thesis
      using nin add_trans_pop(1) by auto
  next
    case (add_trans_swap p'''' γ'' p'' γ''' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then have nin: "∄p γ. (Isolated p' γ', γ, p) ∈ Aiminus1"
      using local.add_trans_swap(1) step.IH step.prems(1,2) by fastforce
    then have "Isolated p' γ' ≠ q"
      using LTS_ε.trans_star_not_to_source_ε[of "Init p''''" "[γ'']" q Aiminus1] 
        local.add_trans_swap(3) post_star_rules_Isolated_source_invariant[of _ Aiminus1 p' γ'] UnCI 
        local.add_trans_swap(1) step.hyps(1) step.prems(1,2) state.simps(7) by metis
    then have "∄p γ. (p, γ, Isolated p' γ') = (Init p'', Some γ''', q)"
      by auto
    then show ?thesis
      using nin add_trans_swap(1) by auto
  next
    case (add_trans_push_1 p'''' γ'' p'' γ''' γ''''' q)
    then have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then show ?thesis
      using add_trans_push_1(1) Un_iff state.inject prod.inject singleton_iff step.IH 
        step.prems(1,2) by blast 
  next
    case (add_trans_push_2 p'''' γ'' p'' γ''' γ'''' q)
    have "(Init p', Some γ', Isolated p' γ') ∉ Ai"
      using step.prems(2) by blast
    then have nin: "∄p γ. (Isolated p' γ', γ, p) ∈ Aiminus1"
      using local.add_trans_push_2(1) step.IH step.prems(1,2) by fastforce
    then have "Isolated p' γ' ≠ q"
      using state.disc(3) 
        LTS_ε.trans_star_not_to_source_ε[of "Init p''''" "[γ'']" q Aiminus1 "Isolated p' γ'"] 
        local.add_trans_push_2(3)
      using post_star_rules_Isolated_source_invariant[of _ Aiminus1 p' γ'] UnCI 
        local.add_trans_push_2(1) step.hyps(1) step.prems(1,2) state.disc(1) by metis
    then have "∄p γ. (Isolated p' γ', γ, p) = (Init p'', ε, q)"
      by auto
    then show ?thesis
      using nin add_trans_push_2(1)
      using local.add_trans_push_2 step.prems(2) by auto 
  qed
qed

lemma post_star_rules_Isolated_sink_invariant:
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p', Some γ', Isolated p' γ') ∉ A'"
  shows "Isolated p' γ' ∈ LTS.sinks A'"
  by (meson LTS.sinks_def2 assms(1,2,3) post_star_rules_Isolated_sink_invariant')


― ‹Corresponds to Schwoon's lemma 3.4›
lemma rtranclp_post_star_rules_constains_successors_states:
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p, w, ss, q) ∈ LTS.trans_star_states A'"
  shows "(¬is_Isolated q ⟶ (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p',w') ⇒⇧* (p, LTS_ε.remove_ε w))) ∧
         (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, LTS_ε.remove_ε w))"
  using assms
proof (induction arbitrary: p q w ss rule: rtranclp_induct)
  case base
  {
    assume ctr_loc: "is_Init q ∨ is_Noninit q"
    then have "(Init p, LTS_ε.remove_ε w, q) ∈ LTS_ε.trans_star_ε A"
      using base LTS_ε.trans_star_states_trans_star_ε by metis
    then have "∃p' w'. (p', w', q) ∈ LTS_ε.trans_star_ε A"
      by auto
    then have ?case
      using ctr_loc ‹(Init p, LTS_ε.remove_ε w, q) ∈ LTS_ε.trans_star_ε A› by blast
  }
  moreover
  {
    assume "is_Isolated q"
    then have ?case
    proof (cases w)
      case Nil
      then have False using base
        using LTS.trans_star_empty LTS.trans_star_states_trans_star ‹is_Isolated q›
        by (metis state.disc(7))
      then show ?thesis
        by metis
    next
      case (Cons γ w_rest)
      then have "(Init p, γ#w_rest, ss, q) ∈ LTS.trans_star_states A"
        using base Cons by blast
      then have "∃s γ'. (s, γ', q) ∈ A"
        using LTS.trans_star_states_transition_relation by metis
      then have False
        using ‹is_Isolated q› isols_def base.prems(2) LTS.isolated_no_edges
        by (metis mem_Collect_eq subset_eq)
      then show ?thesis
        by auto
    qed
  }
  ultimately
  show ?case
   by (meson state.exhaust_disc)
next
  case (step Aiminus1 Ai)
  from step(2) have "∃p1 γ p2 w2 q1. Ai = Aiminus1 ∪ {(p1, γ, q1)} ∧ (p1, γ, q1) ∉ Aiminus1"
    by (cases rule: post_star_rules.cases) auto
  then obtain p1 γ q1 where p1_γ_p2_w2_q'_p:
    "Ai = Aiminus1 ∪ {(p1, γ, q1)}" 
    "(p1, γ, q1) ∉ Aiminus1"
    by auto

  define t where "t = (p1, γ, q1)"
  define j where "j = count (transitions_of' (Init p, w, ss, q)) t"

  note ss_p = step(6)

  from j_def ss_p show ?case
  proof (induction j arbitrary: p q w ss)
    case 0
    then have "(Init p, w, ss, q) ∈ LTS.trans_star_states Aiminus1"
      using count_zero_remove_path_with_word_trans_star_states p1_γ_p2_w2_q'_p(1) t_def
      by metis 
    then show ?case
      using step by auto
  next
    case (Suc j)
    from step(2) show ?case
    proof (cases rule: post_star_rules.cases)
      case (add_trans_pop p2 γ2 p1 q1) (* Note: p1 shadows p1 from above. q1 shadows q1 from above. *)
      note III = add_trans_pop(3)
      note VI = add_trans_pop(2)
      have t_def: "t = (Init p1, ε, q1)"
        using local.add_trans_pop(1) local.add_trans_pop p1_γ_p2_w2_q'_p(1) t_def by blast
      have init_Ai: "inits ⊆ LTS.srcs Ai"
        using step(1,2) step(4)
        using no_edge_to_Ctr_Loc_post_star_rules 
        using r_into_rtranclp by (metis)
      have t_hd_once: "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
      proof -
        have "(ss, w) ∈ LTS.path_with_word Ai"
          using Suc(3) LTS.trans_star_states_path_with_word by metis
        moreover 
        have "inits ⊆ LTS.srcs Ai"
          using init_Ai by auto
        moreover 
        have "0 < count (transitions_of (ss, w)) t"
          by (metis Suc.prems(1) transitions_of'.simps zero_less_Suc)
        moreover 
        have "t = (Init p1, ε, q1)"
          using t_def by auto
        moreover 
        have "Init p1 ∈ inits"
          by (simp add: inits_def)
        ultimately
        show "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
          using init_only_hd[of ss w Ai t p1 ε q1] by auto
      qed

      have "transition_list (ss, w) ≠ []"
        by (metis LTS.trans_star_states_path_with_word LTS.path_with_word.simps Suc.prems(1)
            Suc.prems(2) count_empty less_not_refl2 list.distinct(1) transition_list.simps(1) 
            transitions_of'.simps transitions_of.simps(2) zero_less_Suc)
      then have ss_w_split: "([Init p1,q1], [ε]) @´ (tl ss,  tl w) = (ss, w)"
        using t_hd_once t_def hd_transition_list_append_path_with_word by metis
      then have ss_w_split': "(Init p1, [ε], [Init p1,q1], q1) @@´ (q1, tl w, tl ss, q) = (Init p1, w, ss, q)"
        by auto
      have VII: "p = p1"
      proof -
        have "(Init p, w, ss, q) ∈ LTS.trans_star_states Ai"
          using Suc.prems(2) by blast
        moreover
        have "t = hd (transition_list' (Init p, w, ss, q))"
          using ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› 
          by fastforce
        moreover
        have "transition_list' (Init p, w, ss, q) ≠ []"
          by (simp add: ‹transition_list (ss, w) ≠ []›)
        moreover
        have "t = (Init p1, ε, q1)"
          using t_def by auto
        ultimately
        show "p = p1"
          using LTS.hd_is_hd by fastforce
      qed
      have "j=0"
        using Suc(2) ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› 
        by force
      have "(Init p1, [ε], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai"
      proof -
        have "(Init p1, ε, q1) ∈ Ai"
          using local.add_trans_pop(1) by auto
        moreover
        have "(Init p1, ε, q1) ∉ Aiminus1"
          by (simp add: local.add_trans_pop)
        ultimately
        show "(Init p1, [ε], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai"
          by (meson LTS.trans_star_states.trans_star_states_refl 
              LTS.trans_star_states.trans_star_states_step)
      qed
      have "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
      proof -
        from Suc(3) have "(ss, w) ∈ LTS.path_with_word Ai"
          by (meson LTS.trans_star_states_path_with_word)
        then have tl_ss_w_Ai: "(tl ss, tl w) ∈ LTS.path_with_word Ai"
          by (metis LTS.path_with_word.simps ‹transition_list (ss, w) ≠ []› list.sel(3) 
              transition_list.simps(2))
        from t_hd_once have zero_p1_ε_q1: "0 = count (transitions_of (tl ss, tl w)) (Init p1, ε, q1)"
          using count_append_path_with_word_γ[of "[hd ss]" "[]" "tl ss" "hd w" "tl w" "Init p1" ε q1, simplified]
            ‹(Init p1, [ε], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai› 
            ‹transition_list (ss, w) ≠ []› Suc.prems(2) VII 
            LTS.transition_list_Cons[of "Init p" w ss q Ai ε q1] by (auto simp: t_def)
        have Ai_Aiminus1: "Ai = Aiminus1 ∪ {(Init p1, ε, q1)}"
          using local.add_trans_pop(1) by auto
        from t_hd_once tl_ss_w_Ai zero_p1_ε_q1 Ai_Aiminus1 
          count_zero_remove_path_with_word[OF tl_ss_w_Ai, of "Init p1" ε q1 Aiminus1] 
        have "(tl ss, tl w) ∈ LTS.path_with_word Aiminus1"
          by auto
        moreover
        have "hd (tl ss) = q1"
          using Suc.prems(2) VII ‹transition_list (ss, w) ≠ []› t_def 
            LTS.transition_list_Cons t_hd_once by fastforce
        moreover
        have "last ss = q"
          by (metis LTS.trans_star_states_last Suc.prems(2))
        ultimately
        show "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
          by (metis (no_types, lifting) LTS.trans_star_states_path_with_word 
              LTS.path_with_word_trans_star_states LTS.path_with_word_not_empty Suc.prems(2) 
              last_ConsR list.collapse)
      qed
      have "w = ε # (tl w)"
        by (metis Suc(3) VII ‹transition_list (ss, w) ≠ []› list.distinct(1) list.exhaust_sel 
            list.sel(1) t_def LTS.transition_list_Cons t_hd_once)
      then have w_tl_ε: "LTS_ε.remove_ε w = LTS_ε.remove_ε (tl w)"
        by (metis LTS_ε.remove_ε_def removeAll.simps(2))

      have "∃γ2'. LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1"
        using add_trans_pop
        by (simp add: LTS_ε.trans_star_ε_ε_exp_trans_star) 
      then obtain γ2' where "LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1"
        by blast
      then have "∃ss2. (Init p2, γ2', ss2, q1) ∈ LTS.trans_star_states Aiminus1"
        by (simp add: LTS.trans_star_trans_star_states)
      then obtain ss2 where IIII_1: "(Init p2, γ2', ss2, q1) ∈ LTS.trans_star_states Aiminus1"
        by blast
      have IIII_2: "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
        using ss_w_split' Suc(3) Suc(2) ‹j=0›
        using ‹(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1› by blast
      have IIII: "(Init p2, γ2' @ tl w, ss2 @ (tl (tl ss)), q) ∈ LTS.trans_star_states Aiminus1"
        using IIII_1 IIII_2 by (meson LTS.trans_star_states_append)

      from Suc(1)[of p2 "γ2' @ tl w" "ss2 @ (tl (tl ss))" q]
      have V: "(¬is_Isolated q ⟶
     (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)))) ∧
    (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)))"
        using IIII
        using step.IH step.prems(1,2,3) by blast

      have "¬is_Isolated q ∨ is_Isolated q"
        using state.exhaust_disc by blast
      then show ?thesis
      proof
        assume ctr_q: "¬is_Isolated q"
        then have "∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
          using V by auto
        then obtain p' w' where
          VIII:"(Init p', w', q) ∈ LTS_ε.trans_star_ε A" and steps: "(p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
          by blast
        then have "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)) ∧ 
                   (p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, LTS_ε.remove_ε (tl w))"
        proof -
          have γ2'_γ2: "LTS_ε.remove_ε γ2' = [γ2]"
            by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_def ‹LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1›)
          have "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
            using steps by auto
          moreover
          have rule: "(p2, γ2) ↪ (p, pop)"
            using VI VII by auto 
          from steps have steps': "(p', w') ⇒⇧* (p2, γ2 # (LTS_ε.remove_ε (tl w)))"
            using γ2'_γ2
            by (metis Cons_eq_appendI LTS_ε.remove_ε_append_dist self_append_conv2) 
          from rule steps' have "(p2,  γ2 # (LTS_ε.remove_ε (tl w))) ⇒⇧* (p, LTS_ε.remove_ε (tl w))"
            using  VIII
            by (metis PDS.transition_rel.intros append_self_conv2 lbl.simps(1) r_into_rtranclp 
                step_relp_def) (* VII *) 
          then have "(p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, LTS_ε.remove_ε (tl w))"
            by (simp add: LTS_ε.remove_ε_append_dist γ2'_γ2)
          ultimately
          show "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)) ∧ 
                (p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, LTS_ε.remove_ε (tl w))"
            by auto
        qed
        then have "(p',w') ⇒⇧* (p, LTS_ε.remove_ε (tl w)) ∧ (Init p', w', q) ∈ LTS_ε.trans_star_ε A"
          using VIII by force
        then have "∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p, LTS_ε.remove_ε w)"
          using w_tl_ε by auto
        then show ?thesis
          using ctr_q ‹p = p1› by blast 
      next
        assume "is_Isolated q"
        from V have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, γ2#(LTS_ε.remove_ε w))"
          by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_append_dist LTS_ε.remove_ε_def 
              ‹LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1› ‹is_Isolated q› 
              append_Cons append_self_conv2 w_tl_ε)
          
        then have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p1, LTS_ε.remove_ε w)"
          using VI by (metis append_Nil lbl.simps(1) rtranclp.simps step_relp_def2) 
        then have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, LTS_ε.remove_ε w)"
          using VII by auto
        then show ?thesis
          using ‹is_Isolated q› by blast
      qed
    next
      case (add_trans_swap p2 γ2 p1 γ' q1) (* Adjusted from previous case *)
      note III = add_trans_swap(3)
      note VI = add_trans_swap(2)
      have t_def: "t = (Init p1, Some γ', q1)"
        using local.add_trans_swap(1) local.add_trans_swap p1_γ_p2_w2_q'_p(1) t_def by blast
      have init_Ai: "inits ⊆ LTS.srcs Ai"
        using step(1,2,4) no_edge_to_Ctr_Loc_post_star_rules by (meson r_into_rtranclp)
      have t_hd_once: "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
      proof -
        have "(ss, w) ∈ LTS.path_with_word Ai"
          using Suc(3) LTS.trans_star_states_path_with_word by metis
        moreover 
        have "inits ⊆ LTS.srcs Ai"
          using init_Ai by auto
        moreover 
        have "0 < count (transitions_of (ss, w)) t"
          by (metis Suc.prems(1) transitions_of'.simps zero_less_Suc)
        moreover 
        have "t = (Init p1, Some γ', q1)"
          using t_def
          by auto
        moreover 
        have "Init p1 ∈ inits"
          using inits_def by force
        ultimately
        show "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
          using init_only_hd[of ss w Ai t p1 _ q1] by auto
      qed

      have "transition_list (ss, w) ≠ []"
        by (metis LTS.trans_star_states_path_with_word LTS.path_with_word.simps Suc.prems(1,2) 
            count_empty less_not_refl2 list.distinct(1) transition_list.simps(1) transitions_of'.simps 
            transitions_of.simps(2) zero_less_Suc)
      then have ss_w_split: "([Init p1,q1], [Some γ']) @´ (tl ss,  tl w) = (ss, w)"
        using  t_hd_once t_def hd_transition_list_append_path_with_word by metis
      then have ss_w_split': "(Init p1, [Some γ'], [Init p1,q1], q1) @@´ (q1, tl w, tl ss, q) = (Init p1, w, ss, q)"
        by auto
      have VII: "p = p1"
      proof -
        have "(Init p, w, ss, q) ∈ LTS.trans_star_states Ai"
          using Suc.prems(2) by blast
        moreover
        have "t = hd (transition_list' (Init p, w, ss, q))"
          using ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› by fastforce
        moreover
        have "transition_list' (Init p, w, ss, q) ≠ []"
          by (simp add: ‹transition_list (ss, w) ≠ []›)
        moreover
        have "t = (Init p1, Some γ', q1)"
          using t_def by auto
        ultimately
        show "p = p1"
          using LTS.hd_is_hd by fastforce
      qed
      have "j=0"
        using Suc(2) ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› by force
      have "(Init p1, [Some γ'], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai"
      proof -
        have "(Init p1, Some γ', q1) ∈ Ai"
          using local.add_trans_swap(1) by auto
        moreover
        have "(Init p1, Some γ', q1) ∉ Aiminus1"
          using local.add_trans_swap(4) by blast
        ultimately
        show "(Init p1, [Some γ'], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai"
          by (meson LTS.trans_star_states.trans_star_states_refl LTS.trans_star_states.trans_star_states_step)
      qed
      have "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
      proof -
        from Suc(3) have "(ss, w) ∈ LTS.path_with_word Ai"
          by (meson LTS.trans_star_states_path_with_word)
        then have tl_ss_w_Ai: "(tl ss, tl w) ∈ LTS.path_with_word Ai"
          by (metis LTS.path_with_word.simps ‹transition_list (ss, w) ≠ []› list.sel(3) 
              transition_list.simps(2))
        from t_hd_once have zero_p1_ε_q1: "0 = count (transitions_of (tl ss, tl w)) (Init p1, Some γ', q1)"
          using count_append_path_with_word_γ[of "[hd ss]" "[]" "tl ss" "hd w" "tl w" "Init p1" "Some γ'" q1, simplified]
            ‹(Init p1, [Some γ'], [Init p1, q1], q1) ∈ LTS.trans_star_states Ai› ‹transition_list (ss, w) ≠ []›
            Suc.prems(2) VII LTS.transition_list_Cons[of "Init p" w ss q Ai "Some γ'" q1]
          by (auto simp: t_def)
        have Ai_Aiminus1: "Ai = Aiminus1 ∪ {(Init p1, Some γ', q1)}"
          using local.add_trans_swap(1) by auto 
        from t_hd_once tl_ss_w_Ai zero_p1_ε_q1 Ai_Aiminus1 
          count_zero_remove_path_with_word[OF tl_ss_w_Ai, of "Init p1" _ q1 Aiminus1] 
        have "(tl ss, tl w) ∈ LTS.path_with_word Aiminus1"
          by auto
        moreover
        have "hd (tl ss) = q1"
          using Suc.prems(2) VII ‹transition_list (ss, w) ≠ []› t_def LTS.transition_list_Cons t_hd_once by fastforce
        moreover
        have "last ss = q"
          by (metis LTS.trans_star_states_last Suc.prems(2))
        ultimately
        show "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
          by (metis (no_types, lifting) LTS.trans_star_states_path_with_word 
              LTS.path_with_word_trans_star_states LTS.path_with_word_not_empty Suc.prems(2) 
              last_ConsR list.collapse)
      qed
      have "w = Some γ' # (tl w)"
        by (metis Suc(3) VII ‹transition_list (ss, w) ≠ []› list.distinct(1) list.exhaust_sel 
            list.sel(1) t_def LTS.transition_list_Cons t_hd_once)
      then have w_tl_ε: "LTS_ε.remove_ε w = LTS_ε.remove_ε (Some γ'#tl w)"
        using LTS_ε.remove_ε_def removeAll.simps(2)
        by presburger 
      have "∃γ2'. LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1"
        using add_trans_swap by (simp add: LTS_ε.trans_star_ε_ε_exp_trans_star) 
      then obtain γ2' where "LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1"
        by blast
      then have "∃ss2. (Init p2, γ2', ss2, q1) ∈ LTS.trans_star_states Aiminus1"
        by (simp add: LTS.trans_star_trans_star_states)
      then obtain ss2 where IIII_1: "(Init p2, γ2', ss2, q1) ∈ LTS.trans_star_states Aiminus1"
        by blast
      have IIII_2: "(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1"
        using ss_w_split' Suc(3) Suc(2) ‹j=0›
        using ‹(q1, tl w, tl ss, q) ∈ LTS.trans_star_states Aiminus1› by blast
      have IIII: "(Init p2, γ2' @ tl w, ss2 @ (tl (tl ss)), q) ∈ LTS.trans_star_states Aiminus1"
        using IIII_1 IIII_2 by (meson LTS.trans_star_states_append)

      from Suc(1)[of p2 "γ2' @ tl w" "ss2 @ (tl (tl ss))" q]
      have V: "(¬is_Isolated q ⟶
     (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)))) ∧
    (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)))"
        using IIII
        using step.IH step.prems(1,2,3) by blast

      have "¬is_Isolated q ∨ is_Isolated q"
        using state.exhaust_disc by blast
      then show ?thesis
      proof
        assume ctr_q: "¬is_Isolated q"
        then have "∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
          using V by auto
        then obtain p' w' where
          VIII:"(Init p', w', q) ∈ LTS_ε.trans_star_ε A" and steps: "(p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
          by blast
        then have "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)) ∧ 
                   (p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w))"
        proof -
          have γ2'_γ2: "LTS_ε.remove_ε γ2' = [γ2]"
            by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_def ‹LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1›)
          have "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
            using steps by auto
          moreover
          have rule: "(p2, γ2) ↪ (p, swap γ')"
            using VI VII by auto 
          from steps have steps': "(p', w') ⇒⇧* (p2, γ2 # (LTS_ε.remove_ε (tl w)))"
            using γ2'_γ2
            by (metis Cons_eq_appendI LTS_ε.remove_ε_append_dist self_append_conv2) 
          from rule steps' have "(p2,  γ2 # (LTS_ε.remove_ε (tl w))) ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w))"
            using  VIII
            using PDS.transition_rel.intros append_self_conv2 lbl.simps(1) r_into_rtranclp step_relp_def
            by fastforce
          then have "(p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w))"
            by (simp add: LTS_ε.remove_ε_append_dist γ2'_γ2)
          ultimately
          show "(p',w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w)) ∧ 
                (p2, LTS_ε.remove_ε (γ2' @ tl w)) ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w))"
            by auto
        qed
        then have "(p',w') ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w)) ∧ (Init p', w', q) ∈ LTS_ε.trans_star_ε A"
          using VIII by force
        then have "∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p, LTS_ε.remove_ε w)"
          using LTS_ε.remove_ε_Cons_tl by (metis ‹w = Some γ' # tl w›) 
        then show ?thesis
          using ctr_q ‹p = p1› by blast 
      next
        assume "is_Isolated q"
        from V this have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2' @ tl w))"
          by auto
        then have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, γ2#(LTS_ε.remove_ε (tl w)))"
          by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_append_dist LTS_ε.remove_ε_def
              ‹LTS_ε.ε_exp γ2' [γ2] ∧ (Init p2, γ2', q1) ∈ LTS.trans_star Aiminus1› append_Cons 
              append_self_conv2)
        then have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p1, γ' # LTS_ε.remove_ε (tl w))"
          using VI
          by (metis (no_types) append_Cons append_Nil lbl.simps(2) rtranclp.rtrancl_into_rtrancl
              step_relp_def2)
        then have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, γ' # LTS_ε.remove_ε (tl w))"
          using VII by auto
        then show ?thesis
          using ‹is_Isolated q›
          by (metis LTS_ε.remove_ε_Cons_tl w_tl_ε)
      qed
    next
      case (add_trans_push_1 p2 γ2 p1 γ1 γ'' q1')
      then have t_def: "t = (Init p1, Some γ1, Isolated p1 γ1)"
        using local.add_trans_pop(1) local.add_trans_pop p1_γ_p2_w2_q'_p(1) t_def by blast
      have init_Ai: "inits ⊆ LTS.srcs Ai"
        using step(1,2) step(4)
        using no_edge_to_Ctr_Loc_post_star_rules
        by (meson r_into_rtranclp)
      have t_hd_once: "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
      proof -
        have "(ss, w) ∈ LTS.path_with_word Ai"
          using Suc(3) LTS.trans_star_states_path_with_word by metis
        moreover 
        have  "inits ⊆ LTS.srcs Ai"
          using init_Ai by auto
        moreover 
        have "0 < count (transitions_of (ss, w)) t"
          by (metis Suc.prems(1) transitions_of'.simps zero_less_Suc)
        moreover 
        have "t = (Init p1, Some γ1, Isolated p1 γ1)"
          using t_def by auto
        moreover 
        have "Init p1 ∈ inits"
          using inits_def by fastforce
        ultimately
        show "hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1"
          using init_only_hd[of ss w Ai t] by auto
      qed
      have "transition_list (ss, w) ≠ []"
        by (metis LTS.trans_star_states_path_with_word LTS.path_with_word.simps Suc.prems(1,2) 
            count_empty less_not_refl2 list.distinct(1) transition_list.simps(1) 
            transitions_of'.simps transitions_of.simps(2) zero_less_Suc)

      have VII: "p = p1"
      proof -
        have "(Init p, w, ss, q) ∈ LTS.trans_star_states Ai"
          using Suc.prems(2) by blast
        moreover
        have "t = hd (transition_list' (Init p, w, ss, q))"
          using ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› by fastforce
        moreover
        have "transition_list' (Init p, w, ss, q) ≠ []"
          by (simp add: ‹transition_list (ss, w) ≠ []›)
        moreover
        have "t = (Init p1, Some γ1, Isolated p1 γ1)"
          using t_def by auto
        ultimately
        show "p = p1"
          using LTS.hd_is_hd by fastforce
      qed
      from add_trans_push_1(4) have "∄p γ. (Isolated p1 γ1, γ, p) ∈ Aiminus1"
        using post_star_rules_Isolated_sink_invariant[of A Aiminus1 p1 γ1] step.hyps(1) 
          step.prems(1,2,3) unfolding LTS.sinks_def by blast 
      then have "∄p γ. (Isolated p1 γ1, γ, p) ∈ Ai"
        using local.add_trans_push_1(1) by blast
      then have ss_w_short: "ss = [Init p1, Isolated p1 γ1] ∧ w = [Some γ1]"
        using Suc.prems(2) VII ‹hd (transition_list (ss, w)) = t ∧ count (transitions_of (ss, w)) t = 1› t_def
        LTS.nothing_after_sink[of "Init p1" "Isolated p1 γ1" "tl (tl ss)" "Some γ1" "tl w" Ai] ‹transition_list (ss, w) ≠ []›
        LTS.trans_star_states_path_with_word[of "Init p" w ss q Ai]
        LTS.transition_list_Cons[of "Init p" w ss q Ai]
        by (auto simp: LTS.sinks_def2)
      then have q_ext: "q = Isolated p1 γ1"
        using LTS.trans_star_states_last Suc.prems(2) by fastforce
      have "(p1, [γ1]) ⇒⇧* (p, LTS_ε.remove_ε w)"
        using ss_w_short unfolding LTS_ε.remove_ε_def
        using VII by force
      have "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, LTS_ε.remove_ε w)"
        by (simp add: ‹(p1, [γ1]) ⇒⇧* (p, LTS_ε.remove_ε w)› q_ext)
      then show ?thesis
        using q_ext by auto
    next
      case (add_trans_push_2 p2 γ2 p1 γ1 γ'' q') (* Adjusted from previous case *)
      note IX = add_trans_push_2(3)
      note XIII = add_trans_push_2(2)
      have t_def: "t = (Isolated p1 γ1, Some γ'', q')"
        using local.add_trans_push_2(1,4) p1_γ_p2_w2_q'_p(1) t_def by blast
      have init_Ai: "inits ⊆ LTS.srcs Ai"
        using step(1,2) step(4)
        using no_edge_to_Ctr_Loc_post_star_rules
        by (meson r_into_rtranclp)

      from Suc(2,3) split_at_first_t[of "Init p" w ss q Ai j "Isolated p1 γ1" "Some γ''" q' Aiminus1] t_def
      have "∃u v u_ss v_ss.
              ss = u_ss @ v_ss ∧
              w = u @ [Some γ''] @ v ∧
              (Init p, u, u_ss, Isolated p1 γ1) ∈ LTS.trans_star_states Aiminus1 ∧
              (Isolated p1 γ1, [Some γ''], q') ∈ LTS.trans_star Ai ∧ (q', v, v_ss, q) ∈ LTS.trans_star_states Ai"
        using local.add_trans_push_2(1,4) by blast
      then obtain u v u_ss v_ss where
           ss_split: "ss = u_ss @ v_ss" and
           w_split: "w = u @ [Some γ''] @ v" and
           X_1: "(Init p, u, u_ss, Isolated p1 γ1) ∈ LTS.trans_star_states Aiminus1" and
           out_trans: "(Isolated p1 γ1, [Some γ''], q') ∈ LTS.trans_star Ai" and
           path: "(q', v, v_ss, q) ∈ LTS.trans_star_states Ai"
        by auto
      from step(3)[of p u u_ss "Isolated p1 γ1"] X_1 have
        "(¬is_Isolated (Isolated p1 γ1) ⟶
           (∃p' w'. (Init p', w', Isolated p1 γ1) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p, LTS_ε.remove_ε u))) ∧
         (is_Isolated (Isolated p1 γ1) ⟶ 
           (the_Ctr_Loc (Isolated p1 γ1), [the_Label (Isolated p1 γ1)]) ⇒⇧* (p, LTS_ε.remove_ε u))"
        using step.prems(1,2,3) by auto 
      then have "(the_Ctr_Loc (Isolated p1 γ1), [the_Label (Isolated p1 γ1)]) ⇒⇧* (p, LTS_ε.remove_ε u)"
        by auto
      then have p1_γ1_p_u: "(p1, [γ1]) ⇒⇧* (p, LTS_ε.remove_ε u)"
        by auto
      from IX have "∃γ2ε γ2ss. LTS_ε.ε_exp γ2ε [γ2] ∧ (Init p2, γ2ε, γ2ss, q') ∈ LTS.trans_star_states Aiminus1"
        by (meson LTS.trans_star_trans_star_states LTS_ε.trans_star_ε_ε_exp_trans_star)
      then obtain γ2ε γ2ss where XI_1: "LTS_ε.ε_exp γ2ε [γ2] ∧ (Init p2, γ2ε, γ2ss, q') ∈ LTS.trans_star_states Aiminus1"
        by blast
      have "(q', v, v_ss, q) ∈ LTS.trans_star_states Ai"
        using path .
      have ind:
        "(¬is_Isolated q ⟶ (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v)))) ∧
         (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v)))"
      proof -
        have γ2ss_len: "length γ2ss = Suc (length γ2ε)"
          by (meson LTS.trans_star_states_length XI_1)
          
        have v_ss_empty: "v_ss ≠ []"
          by (metis LTS.trans_star_states.simps path list.distinct(1))
          
        have γ2ss_last: "last γ2ss = hd v_ss"
          by (metis LTS.trans_star_states_hd LTS.trans_star_states_last XI_1 path)


        have cv: "j = count (transitions_of ((v_ss, v))) t"
        proof -
          have last_u_ss: "Isolated p1 γ1 = last u_ss"
            by (meson LTS.trans_star_states_last X_1)
          have q'_hd_v_ss: "q' = hd v_ss"
            by (meson LTS.trans_star_states_hd path)

          have "count (transitions_of' (((Init p, u, u_ss, Isolated p1 γ1), Some γ'') @@⇧γ (q', v, v_ss, q)))
                (Isolated p1 γ1, Some γ'', q') =
                count (transitions_of' (Init p, u, u_ss, Isolated p1 γ1)) (Isolated p1 γ1, Some γ'', q') +
                (if Isolated p1 γ1 = last u_ss ∧ q' = hd v_ss ∧ Some γ'' = Some γ'' then 1 else 0) +
                count (transitions_of' (q', v, v_ss, q)) (Isolated p1 γ1, Some γ'', q')"
            using count_append_trans_star_states_γ_length[of u_ss u v_ss "Init p" "Isolated p1 γ1" "Some γ''" q' v q "Isolated p1 γ1" "Some γ''" q'] t_def ss_split w_split X_1
            by (meson LTS.trans_star_states_length v_ss_empty)
          then have "count (transitions_of (u_ss @ v_ss, u @ Some γ'' # v)) (last u_ss, Some γ'', hd v_ss) = Suc (count (transitions_of (u_ss, u)) (last u_ss, Some γ'', hd v_ss) + count (transitions_of (v_ss, v)) (last u_ss, Some γ'', hd v_ss))"
            using last_u_ss q'_hd_v_ss by auto
          then have "j = count (transitions_of' ((q',v, v_ss, q))) t"
            using last_u_ss q'_hd_v_ss X_1 ss_split w_split add_trans_push_2(4) Suc(2)
              LTS.avoid_count_zero[of "Init p" u u_ss "Isolated p1 γ1" Aiminus1 "Isolated p1 γ1" "Some γ''" q']
            by (auto simp: t_def)
          then show "j = count (transitions_of ((v_ss, v))) t"
             by force
        qed
        have p2_q'_states_Aiminus1: "(Init p2, γ2ε, γ2ss, q') ∈ LTS.trans_star_states Aiminus1"
          using XI_1 by blast
        then have cγ2: "count (transitions_of (γ2ss, γ2ε)) t = 0"
          using LTS.avoid_count_zero local.add_trans_push_2(4) t_def by fastforce
        have "j = count (transitions_of ((γ2ss, γ2ε) @´ (v_ss, v))) t"
          using LTS.count_append_path_with_word[of γ2ss γ2ε v_ss v "Isolated p1 γ1" "Some γ''" q'] t_def
            cγ2 cv γ2ss_len v_ss_empty γ2ss_last
          by force 
        then have j_count: "j = count (transitions_of' (Init p2, γ2ε @ v, γ2ss @ tl v_ss, q)) t"
          by simp

        have "(γ2ss, γ2ε) ∈ LTS.path_with_word Aiminus1"
          by (meson LTS.trans_star_states_path_with_word p2_q'_states_Aiminus1)
        then have γ2ss_path: "(γ2ss, γ2ε) ∈ LTS.path_with_word Ai"
          using add_trans_push_2(1) 
          path_with_word_mono'[of γ2ss γ2ε Aiminus1 Ai] by auto

        have path': "(v_ss, v) ∈ LTS.path_with_word Ai"
          by (meson LTS.trans_star_states_path_with_word path)
        have "(γ2ss, γ2ε) @´ (v_ss, v) ∈ LTS.path_with_word Ai"
          using γ2ss_path path' LTS.append_path_with_word_path_with_word γ2ss_last
          by auto
        then have "(γ2ss @ tl v_ss, γ2ε @ v) ∈ LTS.path_with_word Ai"
           by auto


        have "(Init p2, γ2ε @ v, γ2ss @ tl v_ss, q) ∈ LTS.trans_star_states Ai"
          by (metis (no_types, lifting) LTS.path_with_word_trans_star_states 
              LTS.trans_star_states_append LTS.trans_star_states_hd XI_1 path γ2ss_path γ2ss_last)
          
        from this Suc(1)[of p2 "γ2ε @ v" "γ2ss @ tl v_ss" q]
        show
          "(¬is_Isolated q ⟶ (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v)))) ∧
           (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v)))"
          using j_count by fastforce
      qed

      show ?thesis
      proof (cases "is_Init q ∨ is_Noninit q")
        case True
        have "(∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v)))"
          using True ind by fastforce
        then obtain p' w' where p'_w'_p: "(Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v))"
          by auto
        then have "(p', w') ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v))"
          by auto
        have p2_γ2εv_p1_γ1_γ''_v: "(p2, LTS_ε.remove_ε (γ2ε @ v)) ⇒⇧* (p1, γ1#γ''#LTS_ε.remove_ε v)"
        proof -
          have "γ2 #(LTS_ε.remove_ε v) = LTS_ε.remove_ε (γ2ε @ v)"
            using XI_1
            by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_append_dist LTS_ε.remove_ε_def append_Cons 
                self_append_conv2) 
          moreover
          from XIII have "(p2, γ2 #(LTS_ε.remove_ε v)) ⇒⇧* (p1, γ1#γ''#LTS_ε.remove_ε v)"
            by (metis PDS.transition_rel.intros append_Cons append_Nil lbl.simps(3) r_into_rtranclp 
                step_relp_def)
          ultimately
          show "(p2, LTS_ε.remove_ε (γ2ε @ v)) ⇒⇧* (p1, γ1#γ''#LTS_ε.remove_ε v)"
            by auto
        qed
        have p1_γ1γ''v_p_uv: "(p1, γ1#γ''#LTS_ε.remove_ε v) ⇒⇧* (p, (LTS_ε.remove_ε u) @ (γ''#LTS_ε.remove_ε v))"
          by (metis p1_γ1_p_u append_Cons append_Nil step_relp_append)
        have "(p, (LTS_ε.remove_ε u) @ (γ''#LTS_ε.remove_ε v)) = (p, LTS_ε.remove_ε w)"
          by (metis (no_types, lifting) Cons_eq_append_conv LTS_ε.remove_ε_Cons_tl 
              LTS_ε.remove_ε_append_dist w_split hd_Cons_tl list.inject list.sel(1) list.simps(3) 
              self_append_conv2)
        then show ?thesis
          using True p1_γ1γ''v_p_uv p2_γ2εv_p1_γ1_γ''_v p'_w'_p by fastforce
      next
        case False
        then have q_nlq_p2_γ2εv: "(the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p2, LTS_ε.remove_ε (γ2ε @ v))"
          using ind state.exhaust_disc
          by blast
        have p2_γ2εv_p1_γ1γ''v: "(p2, LTS_ε.remove_ε (γ2ε @ v))  ⇒⇧* (p1, γ1 # γ'' # LTS_ε.remove_ε v)"
          by (metis (mono_tags) LTS_ε.ε_exp_def LTS_ε.remove_ε_append_dist LTS_ε.remove_ε_def XIII 
              XI_1 append_Cons append_Nil lbl.simps(3) r_into_rtranclp step_relp_def2)
          
        have p1_γ1γ''_v_p_uγ''v: "(p1, γ1 # γ'' # LTS_ε.remove_ε v) ⇒⇧* (p, LTS_ε.remove_ε u @ γ'' # LTS_ε.remove_ε v)"
          by (metis p1_γ1_p_u append_Cons append_Nil step_relp_append)
          
        have "(p, LTS_ε.remove_ε u @ γ'' # LTS_ε.remove_ε v) = (p, LTS_ε.remove_ε w)"
          by (metis LTS_ε.remove_ε_Cons_tl LTS_ε.remove_ε_append_dist append_Cons append_Nil w_split 
              hd_Cons_tl list.distinct(1) list.inject)
          
        then show ?thesis
          using False p1_γ1γ''_v_p_uγ''v p2_γ2εv_p1_γ1γ''v q_nlq_p2_γ2εv
          by (metis (no_types, lifting) ind rtranclp_trans) 
      qed
    qed
  qed
qed

― ‹Corresponds to Schwoon's lemma 3.4›
lemma rtranclp_post_star_rules_constains_successors:
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p, w, q) ∈ LTS.trans_star A'"
  shows "(¬is_Isolated q ⟶ (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p',w') ⇒⇧* (p, LTS_ε.remove_ε w))) ∧
         (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, LTS_ε.remove_ε w))"
  using rtranclp_post_star_rules_constains_successors_states assms 
  by (metis LTS.trans_star_trans_star_states) 


― ‹Corresponds to Schwoon's lemma 3.4›
lemma post_star_rules_saturation_constains_successors:
  assumes "saturation post_star_rules A A'"
  assumes "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  assumes "(Init p, w, q) ∈ LTS.trans_star A'"
  shows "(¬is_Isolated q ⟶ (∃p' w'. (Init p', w', q) ∈ LTS_ε.trans_star_ε A ∧ (p',w') ⇒⇧* (p, LTS_ε.remove_ε w))) ∧
         (is_Isolated q ⟶ (the_Ctr_Loc q, [the_Label q]) ⇒⇧* (p, LTS_ε.remove_ε w))"
  using rtranclp_post_star_rules_constains_successors assms saturation_def by metis

― ‹Corresponds to one direction of Schwoon's theorem 3.3›
theorem post_star_rules_subset_post_star_lang:
  assumes "post_star_rules⇧*⇧* A A'"
  assumes "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  shows "{c. accepts_ε A' c} ⊆ post_star (lang_ε A)"
proof
  fix c :: "('ctr_loc, 'label) conf"
  define p where "p = fst c"
  define w where "w = snd c"
  assume "c ∈  {c. accepts_ε A' c}"
  then have "accepts_ε A' (p,w)"
    unfolding p_def w_def by auto
  then obtain q where q_p: "q ∈ finals" "(Init p, w, q) ∈ LTS_ε.trans_star_ε A'" 
    unfolding accepts_ε_def by auto
  then obtain w' where w'_def: "LTS_ε.ε_exp w' w ∧ (Init p, w', q) ∈ LTS.trans_star A'"
    by (meson LTS_ε.trans_star_ε_iff_ε_exp_trans_star)
  then have path: "(Init p, w', q) ∈ LTS.trans_star A'"
    by auto
  have "¬ is_Isolated q"
    using F_not_Ext q_p(1) by blast
  then obtain p' w'a where "(Init p', w'a, q) ∈ LTS_ε.trans_star_ε A ∧ (p', w'a) ⇒⇧* (p, LTS_ε.remove_ε w')"
    using rtranclp_post_star_rules_constains_successors[OF assms(1) assms(2) assms(3) path] by auto
  then have "(Init p', w'a, q) ∈ LTS_ε.trans_star_ε A ∧ (p', w'a) ⇒⇧* (p, w)"
    using w'_def 
    by (metis LTS_ε.ε_exp_def LTS_ε.remove_ε_def 
        ‹LTS_ε.ε_exp w' w ∧ (Init p, w', q) ∈ LTS.trans_star A'›)
  then have "(p,w) ∈ post_star (lang_ε A)"
    using ‹q ∈ finals› unfolding LTS.post_star_def accepts_ε_def lang_ε_def by fastforce
  then show "c ∈ post_star (lang_ε A)"
    unfolding p_def w_def by auto
qed

― ‹Corresponds to Schwoon's theorem 3.3›
theorem post_star_rules_accepts_ε_correct:
  assumes "saturation post_star_rules A A'"
  assumes  "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  shows "{c. accepts_ε A' c} = post_star (lang_ε A)"
proof (rule; rule)
  fix c :: "('ctr_loc, 'label) conf"
  define p where "p = fst c"
  define w where "w = snd c"
  assume "c ∈ post_star (lang_ε A)"
  then obtain p' w' where "(p', w') ⇒⇧* (p, w) ∧ (p', w') ∈ lang_ε A"
    by (auto simp: post_star_def p_def w_def)
  then have "accepts_ε A' (p, w)"
    using lemma_3_3[of p' w' p w A A'] assms(1) by auto 
  then have "accepts_ε A' c"
    unfolding p_def w_def by auto
  then show "c ∈ {c. accepts_ε A' c}"
    by auto
next
  fix c :: "('ctr_loc, 'label) conf"
  assume "c ∈  {c. accepts_ε A' c}"
  then show "c ∈ post_star (lang_ε A)"
    using assms post_star_rules_subset_post_star_lang unfolding saturation_def by blast
qed

― ‹Corresponds to Schwoon's theorem 3.3›
theorem post_star_rules_correct:
  assumes "saturation post_star_rules A A'"
  assumes "inits ⊆ LTS.srcs A"
  assumes "isols ⊆ LTS.isolated A"
  shows "lang_ε A' = post_star (lang_ε A)"
  using assms lang_ε_def post_star_rules_accepts_ε_correct by presburger

end

subsection ‹Intersection Automata›

definition accepts_inters :: "(('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒ (('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state) set ⇒ ('ctr_loc, 'label) conf ⇒ bool" where
  "accepts_inters ts finals ≡ λ(p,w). (∃qq ∈ finals. ((Init p, Init p),w,qq) ∈ LTS.trans_star ts)"

lemma accepts_inters_accepts_aut_inters:
  assumes "ts12 = inters ts1 ts2"
  assumes "finals12 = inters_finals finals1 finals2"
  shows "accepts_inters ts12 finals12 (p,w) ⟷
         Intersection_P_Automaton.accepts_aut_inters ts1 Init finals1 ts2
            finals2 p w"
  by (simp add: Intersection_P_Automaton.accepts_aut_inters_def PDS_with_P_automata.inits_def 
      P_Automaton.accepts_aut_def accepts_inters_def assms)

definition lang_inters :: "(('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state, 'label) transition set ⇒  (('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state) set ⇒ ('ctr_loc, 'label) conf set" where
  "lang_inters ts finals = {c. accepts_inters ts finals c}"

lemma lang_inters_lang_aut_inters:
  assumes "ts12 = inters ts1 ts2"
  assumes "finals12 = inters_finals finals1 finals2"
  shows "(λ(p,w). (p, w)) ` lang_inters ts12 finals12 =
         Intersection_P_Automaton.lang_aut_inters ts1 Init finals1 ts2 finals2"
  using assms
  by (auto simp: Intersection_P_Automaton.lang_aut_inters_def
    Intersection_P_Automaton.inters_accept_iff
    accepts_inters_accepts_aut_inters lang_inters_def is_Init_def
    PDS_with_P_automata.inits_def P_Automaton.accepts_aut_def image_iff)

lemma inters_accept_iff: 
  assumes "ts12 = inters ts1 ts2"
  assumes "finals12 = inters_finals (PDS_with_P_automata.finals final_initss1 final_noninits1) 
                        (PDS_with_P_automata.finals final_initss2 final_noninits2)"
  shows
  "accepts_inters ts12 finals12 (p,w) ⟷ 
     PDS_with_P_automata.accepts final_initss1 final_noninits1 ts1 (p,w) ∧ 
     PDS_with_P_automata.accepts final_initss2 final_noninits2 ts2 (p,w)"
  using accepts_inters_accepts_aut_inters Intersection_P_Automaton.inters_accept_iff assms
  by (simp add: Intersection_P_Automaton.inters_accept_iff accepts_inters_accepts_aut_inters 
      PDS_with_P_automata.accepts_accepts_aut) 

lemma inters_lang:
  assumes "ts12 = inters ts1 ts2"
  assumes "finals12 = 
             inters_finals (PDS_with_P_automata.finals final_initss1 final_noninits1) 
               (PDS_with_P_automata.finals final_initss2 final_noninits2)"
  shows "lang_inters ts12 finals12 = 
           PDS_with_P_automata.lang final_initss1 final_noninits1 ts1 ∩ 
           PDS_with_P_automata.lang final_initss2 final_noninits2 ts2"
  using assms by (auto simp add: PDS_with_P_automata.lang_def inters_accept_iff lang_inters_def)


subsection ‹Intersection epsilon-Automata›

context PDS_with_P_automata begin

interpretation LTS transition_rel .
notation step_relp (infix "⇒" 80)
notation step_starp (infix "⇒⇧*" 80)

definition accepts_ε_inters :: "(('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ ('ctr_loc, 'label) conf ⇒ bool" where
  "accepts_ε_inters ts ≡ λ(p,w). (∃q1 ∈ finals. ∃q2 ∈ finals. ((Init p, Init p),w,(q1,q2)) ∈ LTS_ε.trans_star_ε ts)"

definition lang_ε_inters :: "(('ctr_loc, 'noninit, 'label) state * ('ctr_loc, 'noninit, 'label) state, 'label option) transition set ⇒ ('ctr_loc, 'label) conf set" where
  "lang_ε_inters ts = {c. accepts_ε_inters ts c}"

lemma trans_star_trans_star_ε_inter:
  assumes "LTS_ε.ε_exp w1 w"
  assumes  "LTS_ε.ε_exp w2 w"
  assumes "(p1, w1, p2) ∈ LTS.trans_star ts1"
  assumes "(q1, w2, q2) ∈ LTS.trans_star ts2"
  shows "((p1,q1), w :: 'label list, (p2,q2)) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
  using assms
proof (induction "length w1 + length w2" arbitrary: w1 w2 w p1 q1 rule: less_induct)
  case less
  then show ?case
  proof (cases "∃α w1' w2' β. w1=Some α#w1' ∧ w2=Some β#w2'")
    case True
    from True obtain α β w1' w2' where True'':
      "w1=Some α#w1'"
      "w2=Some β#w2'"
      by auto
    have "α = β"
      by (metis True''(1) True''(2) LTS_ε.ε_exp_Some_hd less.prems(1) less.prems(2))
    then have True':   
      "w1=Some α#w1'"
      "w2=Some α#w2'"
      using True'' by auto
    define w' where "w' = tl w"
    obtain p' where p'_p: "(p1, Some α, p') ∈ ts1 ∧ (p', w1', p2) ∈ LTS.trans_star ts1"
      using less True'(1) by (metis LTS_ε.trans_star_cons_ε)
    obtain q' where q'_p: "(q1, Some α, q') ∈ ts2 ∧(q', w2', q2) ∈ LTS.trans_star ts2"
      using less True'(2) by (metis LTS_ε.trans_star_cons_ε) 
    have ind: "((p', q'), w', p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
    proof -
      have "length w1' + length w2' < length w1 + length w2"
        using True'(1) True'(2) by simp
      moreover
      have "LTS_ε.ε_exp w1' w'"
        by (metis (no_types) LTS_ε.ε_exp_def less(2) True'(1) list.map(2) list.sel(3) 
            option.simps(3) removeAll.simps(2) w'_def)
      moreover
      have "LTS_ε.ε_exp w2' w'"
        by (metis (no_types) LTS_ε.ε_exp_def less(3) True'(2) list.map(2) list.sel(3) 
            option.simps(3) removeAll.simps(2) w'_def)
      moreover
      have "(p', w1', p2) ∈ LTS.trans_star ts1"
        using p'_p by simp
      moreover
      have "(q', w2', q2) ∈ LTS.trans_star ts2"
        using q'_p by simp
      ultimately
      show "((p', q'), w', p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
        using less(1)[of w1' w2' w' p' q'] by auto
    qed
    moreover
    have "((p1, q1), Some α, (p', q')) ∈ (inters_ε ts1 ts2)"
      by (simp add: inters_ε_def p'_p q'_p)
    ultimately
    have "((p1, q1), α#w', p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
      by (meson LTS_ε.trans_star_ε.trans_star_ε_step_γ)
    moreover
    have "length w > 0"
      using less(3) True' LTS_ε.ε_exp_Some_length by metis
    moreover
    have "hd w = α"
      using less(3) True' LTS_ε.ε_exp_Some_hd by metis
    ultimately
    show ?thesis
      using w'_def by force
  next
    case False
    note False_outer_outer_outer_outer = False
    show ?thesis 
    proof (cases "w1 = [] ∧ w2 = []")
      case True
      then have same: "p1 = p2 ∧ q1 = q2"
        by (metis LTS.trans_star_empty less.prems(3) less.prems(4))
      have "w = []"
        using True less(2) LTS_ε.exp_empty_empty by auto
      then show ?thesis
        using less True
        by (simp add: LTS_ε.trans_star_ε.trans_star_ε_refl same)
    next
      case False
      note False_outer_outer_outer = False
      show ?thesis
      proof (cases "∃w1'. w1=ε#w1'")
        case True (* Adapted from above. *)
        then obtain w1' where True':
          "w1=ε#w1'"
          by auto
        obtain p' where p'_p: "(p1, ε, p') ∈ ts1 ∧ (p', w1', p2) ∈ LTS.trans_star ts1"
          using less True'(1) by (metis LTS_ε.trans_star_cons_ε)
        have q'_p: " (q1, w2, q2) ∈ LTS.trans_star ts2"
          using less by (metis) 
        have ind: "((p', q1), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
        proof -
          have "length w1' + length w2 < length w1 + length w2"
            using True'(1) by simp
          moreover
          have "LTS_ε.ε_exp w1' w"
            by (metis (no_types) LTS_ε.ε_exp_def less(2) True'(1) removeAll.simps(2))
          moreover
          have "LTS_ε.ε_exp w2 w"
            by (metis (no_types) less(3))
          moreover
          have "(p', w1', p2) ∈ LTS.trans_star ts1"
            using p'_p by simp
          moreover
          have "(q1, w2, q2) ∈ LTS.trans_star ts2"
            using q'_p by simp
          ultimately
          show "((p', q1), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
            using less(1)[of w1' w2 w p' q1] by auto
        qed
        moreover
        have "((p1, q1), ε, (p', q1)) ∈ (inters_ε ts1 ts2)"
          by (simp add: inters_ε_def p'_p q'_p)
        ultimately
        have "((p1, q1), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
          using LTS_ε.trans_star_ε.simps by fastforce
        then
        show ?thesis
           by force
      next
        case False
        note False_outer_outer = False
        then show ?thesis
        proof (cases "∃w2'. w2 = ε # w2'")
          case True (* Adapted from above. *)
          then obtain w2' where True':
            "w2=ε#w2'"
            by auto
          have p'_p: "(p1, w1, p2) ∈ LTS.trans_star ts1"
            using less by (metis)
          obtain q' where q'_p: "(q1, ε, q') ∈ ts2 ∧(q', w2', q2) ∈ LTS.trans_star ts2"
            using less True'(1) by (metis LTS_ε.trans_star_cons_ε) 
          have ind: "((p1, q'), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
          proof -
            have "length w1 + length w2' < length w1 + length w2"
              using True'(1) True'(1) by simp
            moreover
            have "LTS_ε.ε_exp w1 w"
              by (metis (no_types) less(2))
            moreover
            have "LTS_ε.ε_exp w2' w"
              by (metis (no_types) LTS_ε.ε_exp_def less(3) True'(1) removeAll.simps(2))
            moreover
            have "(p1, w1, p2) ∈ LTS.trans_star ts1"
              using p'_p by simp
            moreover
            have "(q', w2', q2) ∈ LTS.trans_star ts2"
              using q'_p by simp
            ultimately
            show "((p1, q'), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
              using less(1)[of w1 w2' w p1 q'] by auto
          qed
          moreover
          have "((p1, q1), ε, (p1, q')) ∈ (inters_ε ts1 ts2)"
            by (simp add: inters_ε_def p'_p q'_p)
          ultimately
          have "((p1, q1), w, p2, q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
            using LTS_ε.trans_star_ε.simps by fastforce
          then
          show ?thesis
            by force
        next
          case False
          then have "(w1 = [] ∧ (∃α w2'. w2 = Some α # w2')) ∨ ((∃α w1'. w1 = Some α # w1') ∧ w2 = [])"
            using False_outer_outer False_outer_outer_outer False_outer_outer_outer_outer
            by (metis neq_Nil_conv option.exhaust_sel)
          then show ?thesis
            by (metis LTS_ε.ε_exp_def LTS_ε.ε_exp_Some_length less.prems(1,2)  less_numeral_extra(3) 
                list.simps(8) list.size(3) removeAll.simps(1))
        qed
      qed
    qed
  qed
qed

lemma trans_star_ε_inter:
  assumes "(p1, w :: 'label list, p2) ∈ LTS_ε.trans_star_ε ts1"
  assumes "(q1, w, q2) ∈ LTS_ε.trans_star_ε ts2"
  shows "((p1, q1), w, (p2, q2)) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
proof -
  have "∃w1'. LTS_ε.ε_exp w1' w ∧ (p1, w1', p2) ∈ LTS.trans_star ts1"
    using assms by (simp add: LTS_ε.trans_star_ε_ε_exp_trans_star)
  then obtain w1' where "LTS_ε.ε_exp w1' w ∧ (p1, w1', p2) ∈ LTS.trans_star ts1"
    by auto
  moreover
  have "∃w2'. LTS_ε.ε_exp w2' w ∧ (q1, w2', q2) ∈ LTS.trans_star ts2"
    using assms by (simp add: LTS_ε.trans_star_ε_ε_exp_trans_star)
  then obtain w2' where "LTS_ε.ε_exp w2' w ∧ (q1, w2', q2) ∈ LTS.trans_star ts2"
    by auto
  ultimately
  show ?thesis
    using trans_star_trans_star_ε_inter by metis
qed

lemma inters_trans_star_ε1:
  assumes "(p1q2, w :: 'label list, p2q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
  shows "(fst p1q2, w, fst p2q2) ∈ LTS_ε.trans_star_ε ts1"
  using assms 
proof (induction rule: LTS_ε.trans_star_ε.induct[OF assms(1)])
  case (1 p)
  then show ?case
    by (simp add: LTS_ε.trans_star_ε.trans_star_ε_refl) 
next
  case (2 p γ q' w q)
  then have ind: "(fst q', w, fst q) ∈ LTS_ε.trans_star_ε ts1"
    by auto
  from 2(1) have "(p, Some γ, q') ∈ 
                     {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2} ∪ 
                     {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1} ∪
                     {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts1}"
    unfolding inters_ε_def by auto
  moreover                
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2}"
    then have "∃p1 q1. p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, Some γ, p2) ∈ ts1 ∧ (q1, Some γ, q2) ∈ ts2)"
      by simp
    then obtain p1 q1 where "p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, Some γ, p2) ∈ ts1 ∧ (q1, Some γ, q2) ∈ ts2)"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_γ ind by fastforce
  }
  moreover
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1}"
    then have ?case
      by auto
  }
  moreover
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts1}"
    then have ?case
      by auto
  }  
  ultimately 
  show ?case 
    by auto
next
  case (3 p q' w q)
  then have ind: "(fst q', w, fst q) ∈ LTS_ε.trans_star_ε ts1"
    by auto
  from 3(1) have "(p, ε, q') ∈
                     {((p1, q1), α, (p2, q2)) | p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2} ∪
                     {((p1, q1), ε, (p2, q1)) | p1 p2 q1. (p1, ε, p2) ∈ ts1} ∪
                     {((p1, q1), ε, (p1, q2)) | p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    unfolding inters_ε_def by auto
  moreover                
  {
    assume "(p, ε, q') ∈ {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2}"
    then have "∃p1 q1. p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, ε, p2) ∈ ts1 ∧ (q1, ε, q2) ∈ ts2)"
      by simp
    then obtain p1 q1 where "p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, ε, p2) ∈ ts1 ∧ (q1, ε, q2) ∈ ts2)"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }
  moreover
  {
    assume "(p, ε, q') ∈ {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1}"
    then have "∃p1 p2 q1. p = (p1, q1) ∧ q' = (p2, q1) ∧ (p1, ε, p2) ∈ ts1"
      by auto
    then obtain p1 p2 q1 where "p = (p1, q1) ∧ q' = (p2, q1) ∧ (p1, ε, p2) ∈ ts1"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }
  moreover
  {
    assume "(p, ε, q') ∈ {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    then have "∃p1 q1 q2. p = (p1, q1) ∧ q' = (p1, q2) ∧ (q1, ε, q2) ∈ ts2"
      by auto
    then obtain p1 q1 q2 where "p = (p1, q1) ∧ q' = (p1, q2) ∧ (q1, ε, q2) ∈ ts2"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }  
  ultimately 
  show ?case 
    by auto
qed

lemma inters_trans_star_ε:
  assumes "(p1q2, w :: 'label list, p2q2) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2)"
  shows "(snd p1q2, w, snd p2q2) ∈ LTS_ε.trans_star_ε ts2"
  using assms 
proof (induction rule: LTS_ε.trans_star_ε.induct[OF assms(1)])
  case (1 p)
  then show ?case
    by (simp add: LTS_ε.trans_star_ε.trans_star_ε_refl) 
next
  case (2 p γ q' w q)
  then have ind: "(snd q', w, snd q) ∈ LTS_ε.trans_star_ε ts2"
    by auto
  from 2(1) have "(p, Some γ, q') ∈ 
                     {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2} ∪ 
                     {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1} ∪
                     {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    unfolding inters_ε_def by auto
  moreover                
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2}"
    then have "∃p1 q1. p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, Some γ, p2) ∈ ts1 ∧ (q1, Some γ, q2) ∈ ts2)"
      by simp
    then obtain p1 q1 where "p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, Some γ, p2) ∈ ts1 ∧ (q1, Some γ, q2) ∈ ts2)"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_γ ind by fastforce
  }
  moreover
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1}"
    then have ?case
      by auto
  }
  moreover
  {
    assume "(p, Some γ, q') ∈ {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    then have ?case
      by auto
  }  
  ultimately 
  show ?case 
    by auto
next
  case (3 p q' w q)
  then have ind: "(snd q', w, snd q) ∈ LTS_ε.trans_star_ε ts2"
    by auto
  from 3(1) have "(p, ε, q') ∈
                     {((p1, q1), α, (p2, q2)) | p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2} ∪
                     {((p1, q1), ε, (p2, q1)) | p1 p2 q1. (p1, ε, p2) ∈ ts1} ∪
                     {((p1, q1), ε, (p1, q2)) | p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    unfolding inters_ε_def by auto
  moreover                
  {
    assume "(p, ε, q') ∈ {((p1, q1), α, p2, q2) |p1 q1 α p2 q2. (p1, α, p2) ∈ ts1 ∧ (q1, α, q2) ∈ ts2}"
    then have "∃p1 q1. p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, ε, p2) ∈ ts1 ∧ (q1, ε, q2) ∈ ts2)"
      by simp
    then obtain p1 q1 where "p = (p1, q1) ∧ (∃p2 q2. q' = (p2, q2) ∧ (p1, ε, p2) ∈ ts1 ∧ (q1, ε, q2) ∈ ts2)"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }
  moreover
  {
    assume "(p, ε, q') ∈ {((p1, q1), ε, p2, q1) |p1 p2 q1. (p1, ε, p2) ∈ ts1}"
    then have "∃p1 p2 q1. p = (p1, q1) ∧ q' = (p2, q1) ∧ (p1, ε, p2) ∈ ts1"
      by auto
    then obtain p1 p2 q1 where "p = (p1, q1) ∧ q' = (p2, q1) ∧ (p1, ε, p2) ∈ ts1"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }
  moreover
  {
    assume "(p, ε, q') ∈ {((p1, q1), ε, p1, q2) |p1 q1 q2. (q1, ε, q2) ∈ ts2}"
    then have "∃p1 q1 q2. p = (p1, q1) ∧ q' = (p1, q2) ∧ (q1, ε, q2) ∈ ts2"
      by auto
    then obtain p1 q1 q2 where "p = (p1, q1) ∧ q' = (p1, q2) ∧ (q1, ε, q2) ∈ ts2"
      by auto
    then have ?case
      using LTS_ε.trans_star_ε.trans_star_ε_step_ε ind by fastforce
  }
  ultimately
  show ?case
    by auto
qed

lemma inters_trans_star_ε_iff:
  "((p1,q2), w :: 'label list, (p2,q2)) ∈ LTS_ε.trans_star_ε (inters_ε ts1 ts2) ⟷ 
   (p1, w, p2) ∈ LTS_ε.trans_star_ε ts1 ∧ (q2, w, q2) ∈ LTS_ε.trans_star_ε ts2"
  by (metis fst_conv inters_trans_star_ε inters_trans_star_ε1 snd_conv trans_star_ε_inter)

lemma inters_ε_accept_ε_iff: 
  "accepts_ε_inters (inters_ε ts1 ts2) c ⟷ accepts_ε ts1 c ∧ accepts_ε ts2 c"
proof
  assume "accepts_ε_inters (inters_ε ts1 ts2) c"
  then show "accepts_ε ts1 c ∧ accepts_ε ts2 c"
    using accepts_ε_def accepts_ε_inters_def inters_trans_star_ε inters_trans_star_ε1 by fastforce
next
  assume asm: "accepts_ε ts1 c ∧ accepts_ε ts2 c"
  define p where "p = fst c"
  define w where "w = snd c"

  from asm have "accepts_ε ts1 (p,w) ∧ accepts_ε ts2 (p,w)"
    using p_def w_def by auto
  then have "(∃q∈finals. (Init p, w, q) ∈ LTS_ε.trans_star_ε ts1) ∧ 
             (∃q∈finals. (Init p, w, q) ∈ LTS_ε.trans_star_ε ts2)" 
    unfolding accepts_ε_def by auto
  then show "accepts_ε_inters (inters_ε ts1 ts2) c"
    using accepts_ε_inters_def p_def trans_star_ε_inter w_def by fastforce
qed

lemma inters_ε_lang_ε: "lang_ε_inters (inters_ε ts1 ts2) = lang_ε ts1 ∩ lang_ε ts2"
  unfolding lang_ε_inters_def lang_ε_def using inters_ε_accept_ε_iff by auto


subsection ‹Dual search›

lemma dual1: 
  "post_star (lang_ε A1) ∩ pre_star (lang A2) = {c. ∃c1 ∈ lang_ε A1. ∃c2 ∈ lang A2. c1 ⇒⇧* c ∧ c ⇒⇧* c2}"
proof -
  have "post_star (lang_ε A1) ∩ pre_star (lang A2) = {c. c ∈ post_star (lang_ε A1) ∧ c ∈ pre_star (lang A2)}"
    by auto
  moreover
  have "... = {c. (∃c1 ∈ lang_ε A1. c1 ⇒⇧* c) ∧ (∃c2 ∈ lang A2. c ⇒⇧* c2)}"
    unfolding post_star_def pre_star_def by auto
  moreover
  have "... = {c. ∃c1 ∈ lang_ε A1. ∃c2 ∈ lang A2. c1 ⇒⇧* c ∧ c ⇒⇧* c2}"
    by auto
  ultimately
  show ?thesis by metis
qed

lemma dual2: 
  "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {} ⟷ (∃c1 ∈ lang_ε A1. ∃c2 ∈ lang A2. c1 ⇒⇧* c2)"
proof (rule)
  assume "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {}"
  then show "∃c1∈lang_ε A1. ∃c2∈lang A2. c1 ⇒⇧* c2"
    by (auto simp: pre_star_def post_star_def intro: rtranclp_trans)
next
  assume "∃c1∈lang_ε A1. ∃c2∈lang A2. c1 ⇒⇧* c2"
  then show "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {}"
    using dual1 by auto
qed

lemma LTS_ε_of_LTS_Some: "(p, Some γ, q') ∈ LTS_ε_of_LTS A2' ⟷ (p, γ, q') ∈ A2'"
  unfolding LTS_ε_of_LTS_def ε_edge_of_edge_def by (auto simp add: rev_image_eqI)

lemma LTS_ε_of_LTS_None: "(p, None, q') ∉ LTS_ε_of_LTS A2'"
  unfolding LTS_ε_of_LTS_def ε_edge_of_edge_def by (auto)

lemma trans_star_ε_LTS_ε_of_LTS_trans_star:
  assumes "(p,w,q) ∈ LTS_ε.trans_star_ε (LTS_ε_of_LTS A2')"
  shows "(p,w,q) ∈ LTS.trans_star A2'"
  using assms
proof (induction rule: LTS_ε.trans_star_ε.induct[OF assms(1)] )
  case (1 p)
  then show ?case
    by (simp add: LTS.trans_star.trans_star_refl)
next
  case (2 p γ q' w q)
  moreover
  have "(p, γ, q') ∈ A2'"
    using 2(1) using LTS_ε_of_LTS_Some by metis
  moreover
  have "(q', w, q) ∈ LTS.trans_star A2'"
    using "2.IH" 2(2) by auto
  ultimately show ?case
    by (meson LTS.trans_star.trans_star_step)
next
  case (3 p q' w q)
  then show ?case
    using LTS_ε_of_LTS_None by fastforce
qed

lemma trans_star_trans_star_ε_LTS_ε_of_LTS:
  assumes "(p,w,q) ∈ LTS.trans_star A2'"
  shows "(p,w,q) ∈ LTS_ε.trans_star_ε (LTS_ε_of_LTS A2')"
  using assms
proof (induction rule: LTS.trans_star.induct[OF assms(1)])
  case (1 p)
  then show ?case
    by (simp add: LTS_ε.trans_star_ε.trans_star_ε_refl)
next
  case (2 p γ q' w q)
  then show ?case
    by (meson LTS_ε.trans_star_ε.trans_star_ε_step_γ LTS_ε_of_LTS_Some)
qed


lemma accepts_ε_LTS_ε_of_LTS_iff_accepts: "accepts_ε (LTS_ε_of_LTS A2') (p, w) ⟷ accepts A2' (p, w)"
  using accepts_ε_def accepts_def trans_star_ε_LTS_ε_of_LTS_trans_star 
    trans_star_trans_star_ε_LTS_ε_of_LTS by fastforce

lemma lang_ε_LTS_ε_of_LTS_is_lang: "lang_ε (LTS_ε_of_LTS A2') = lang A2'"
  unfolding lang_ε_def lang_def using accepts_ε_LTS_ε_of_LTS_iff_accepts by auto

theorem dual_star_correct_early_termination:
  assumes "inits ⊆ LTS.srcs A1"
  assumes "inits ⊆ LTS.srcs A2"
  assumes "isols ⊆ LTS.isolated A1"
  assumes "isols ⊆ LTS.isolated A2"
  assumes "post_star_rules⇧*⇧* A1 A1'"
  assumes "pre_star_rule⇧*⇧* A2 A2'"
  assumes "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {}"
  shows "∃c1 ∈ lang_ε A1. ∃c2 ∈ lang A2. c1 ⇒⇧* c2"
proof -
  have "{c. accepts_ε A1' c} ⊆ post_star (lang_ε A1)"
    using assms using  post_star_rules_subset_post_star_lang by auto
  then have A1'_correct: "lang_ε A1' ⊆ post_star (lang_ε A1)"
    unfolding lang_ε_def by auto

  have "{c. accepts A2' c} ⊆ pre_star (lang A2)" 
    using pre_star_rule_subset_pre_star_lang[of A2 A2'] assms by auto
  then have A2'_correct: "lang A2' ⊆ pre_star (lang A2)" 
    unfolding lang_def by auto

  have "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) = lang_ε A1' ∩ lang_ε (LTS_ε_of_LTS A2')"
    using inters_ε_lang_ε[of A1' "(LTS_ε_of_LTS A2')"] by auto
  moreover
  have "... = lang_ε A1' ∩ lang A2'"
    using lang_ε_LTS_ε_of_LTS_is_lang by auto
  moreover
  have "... ⊆ post_star (lang_ε A1) ∩ pre_star (lang A2)"
    using A1'_correct A2'_correct by auto
  ultimately
  have inters_correct: "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ⊆ post_star (lang_ε A1) ∩ pre_star (lang A2)"
    by metis

  from assms have "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {}"
    using inters_correct by auto
  then show "∃c1∈lang_ε A1. ∃c2∈lang A2. c1 ⇒⇧* c2"
    using dual2 by auto

qed

theorem dual_star_correct_saturation:
  assumes "inits ⊆ LTS.srcs A1"
  assumes "inits ⊆ LTS.srcs A2"
  assumes "isols ⊆ LTS.isolated A1"
  assumes "isols ⊆ LTS.isolated A2"
  assumes "saturation post_star_rules A1 A1'"
  assumes "saturation pre_star_rule A2 A2'"
  shows "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {} ⟷ (∃c1 ∈ lang_ε A1. ∃c2 ∈ lang A2. c1 ⇒⇧* c2)"
proof -
  have "{c. accepts_ε A1' c} = post_star (lang_ε A1)"
    using post_star_rules_accepts_ε_correct[of A1 A1'] assms by auto
  then have A1'_correct: "lang_ε A1' = post_star (lang_ε A1)"
    unfolding lang_ε_def by auto

  have "{c. accepts A2' c} = pre_star (lang A2)" 
    using pre_star_rule_accepts_correct[of A2 A2'] assms by auto
  then have A2'_correct: "lang A2' = pre_star (lang A2)" 
    unfolding lang_def by auto

  have "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) = lang_ε A1' ∩ lang_ε (LTS_ε_of_LTS A2')"
    using inters_ε_lang_ε[of A1' "(LTS_ε_of_LTS A2')"] by auto
  moreover
  have "... = lang_ε A1' ∩ lang A2'"
    using lang_ε_LTS_ε_of_LTS_is_lang by auto
  moreover
  have "... = post_star (lang_ε A1) ∩ pre_star (lang A2)"
    using A1'_correct A2'_correct by auto
  ultimately
  have inters_correct: "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) = post_star (lang_ε A1) ∩ pre_star (lang A2)"
    by metis

  show ?thesis
  proof 
    assume "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {}"
    then have "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {}"
      using inters_correct by auto
    then show "∃c1∈lang_ε A1. ∃c2∈lang A2. c1 ⇒⇧* c2"
      using dual2 by auto
  next
    assume "∃c1∈lang_ε A1. ∃c2∈lang A2. c1 ⇒⇧* c2"
    then have "post_star (lang_ε A1) ∩ pre_star (lang A2) ≠ {}"
      using dual2 by auto
    then show "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {}"
      using inters_correct by auto
  qed
qed

theorem dual_star_correct_early_termination_configs:
  assumes "inits ⊆ LTS.srcs A1"
  assumes "inits ⊆ LTS.srcs A2"
  assumes "isols ⊆ LTS.isolated A1"
  assumes "isols ⊆ LTS.isolated A2"
  assumes "lang_ε A1 = {c1}"
  assumes "lang A2 = {c2}"
  assumes "post_star_rules⇧*⇧* A1 A1'"
  assumes "pre_star_rule⇧*⇧* A2 A2'"
  assumes "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {}"
  shows "c1 ⇒⇧* c2"
  using dual_star_correct_early_termination assms by (metis singletonD)

theorem dual_star_correct_saturation_configs:
  assumes "inits ⊆ LTS.srcs A1"
  assumes "inits ⊆ LTS.srcs A2"
  assumes "isols ⊆ LTS.isolated A1"
  assumes "isols ⊆ LTS.isolated A2"
  assumes "lang_ε A1 = {c1}"
  assumes "lang A2 = {c2}"
  assumes "saturation post_star_rules A1 A1'"
  assumes "saturation pre_star_rule A2 A2'"
  shows "lang_ε_inters (inters_ε A1' (LTS_ε_of_LTS A2')) ≠ {} ⟷ c1 ⇒⇧* c2"
  using assms dual_star_correct_saturation by auto

end

end