Theory IOA

theory IOA
imports Asig
(*  Title:      HOL/IOA/IOA.thy
Author: Tobias Nipkow & Konrad Slind
Copyright 1994 TU Muenchen
*)


header {* The I/O automata of Lynch and Tuttle *}

theory IOA
imports Asig
begin

type_synonym 'a seq = "nat => 'a"
type_synonym 'a oseq = "nat => 'a option"
type_synonym ('a, 'b) execution = "'a oseq * 'b seq"
type_synonym ('a, 's) transition = "('s * 'a * 's)"
type_synonym ('a,'s) ioa = "'a signature * 's set * ('a, 's) transition set"

consts

(* IO automata *)
state_trans::"['action signature, ('action,'state)transition set] => bool"
asig_of ::"('action,'state)ioa => 'action signature"
starts_of ::"('action,'state)ioa => 'state set"
trans_of ::"('action,'state)ioa => ('action,'state)transition set"
IOA ::"('action,'state)ioa => bool"

(* Executions, schedules, and traces *)

is_execution_fragment ::"[('action,'state)ioa, ('action,'state)execution] => bool"
has_execution ::"[('action,'state)ioa, ('action,'state)execution] => bool"
executions :: "('action,'state)ioa => ('action,'state)execution set"
mk_trace :: "[('action,'state)ioa, 'action oseq] => 'action oseq"
reachable :: "[('action,'state)ioa, 'state] => bool"
invariant :: "[('action,'state)ioa, 'state=>bool] => bool"
has_trace :: "[('action,'state)ioa, 'action oseq] => bool"
traces :: "('action,'state)ioa => 'action oseq set"
NF :: "'a oseq => 'a oseq"

(* Composition of action signatures and automata *)
compatible_asigs ::"('a => 'action signature) => bool"
asig_composition ::"('a => 'action signature) => 'action signature"
compatible_ioas ::"('a => ('action,'state)ioa) => bool"
ioa_composition ::"('a => ('action, 'state)ioa) =>('action,'a => 'state)ioa"

(* binary composition of action signatures and automata *)
compat_asigs ::"['action signature, 'action signature] => bool"
asig_comp ::"['action signature, 'action signature] => 'action signature"
compat_ioas ::"[('action,'s)ioa, ('action,'t)ioa] => bool"
par ::"[('a,'s)ioa, ('a,'t)ioa] => ('a,'s*'t)ioa" (infixr "||" 10)

(* Filtering and hiding *)
filter_oseq :: "('a => bool) => 'a oseq => 'a oseq"

restrict_asig :: "['a signature, 'a set] => 'a signature"
restrict :: "[('a,'s)ioa, 'a set] => ('a,'s)ioa"

(* Notions of correctness *)
ioa_implements :: "[('action,'state1)ioa, ('action,'state2)ioa] => bool"

(* Instantiation of abstract IOA by concrete actions *)
rename:: "('a, 'b)ioa => ('c => 'a option) => ('c,'b)ioa"

defs

state_trans_def:
"state_trans asig R ==
(!triple. triple:R --> fst(snd(triple)):actions(asig)) &
(!a. (a:inputs(asig)) --> (!s1. ? s2. (s1,a,s2):R))"



asig_of_def: "asig_of == fst"
starts_of_def: "starts_of == (fst o snd)"
trans_of_def: "trans_of == (snd o snd)"

ioa_def:
"IOA(ioa) == (is_asig(asig_of(ioa)) &
(~ starts_of(ioa) = {}) &
state_trans (asig_of ioa) (trans_of ioa))"



(* An execution fragment is modelled with a pair of sequences:
* the first is the action options, the second the state sequence.
* Finite executions have None actions from some point on.
*******)

is_execution_fragment_def:
"is_execution_fragment A ex ==
let act = fst(ex); state = snd(ex)
in !n a. (act(n)=None --> state(Suc(n)) = state(n)) &
(act(n)=Some(a) --> (state(n),a,state(Suc(n))):trans_of(A))"



executions_def:
"executions(ioa) == {e. snd e 0:starts_of(ioa) &
is_execution_fragment ioa e}"



reachable_def:
"reachable ioa s == (? ex:executions(ioa). ? n. (snd ex n) = s)"


invariant_def: "invariant A P == (!s. reachable A s --> P(s))"


(* Restrict the trace to those members of the set s *)
filter_oseq_def:
"filter_oseq p s ==
(%i. case s(i)
of None => None
| Some(x) => if p x then Some x else None)"



mk_trace_def:
"mk_trace(ioa) == filter_oseq(%a. a:externals(asig_of(ioa)))"


(* Does an ioa have an execution with the given trace *)
has_trace_def:
"has_trace ioa b ==
(? ex:executions(ioa). b = mk_trace ioa (fst ex))"


normal_form_def:
"NF(tr) == @nf. ? f. mono(f) & (!i. nf(i)=tr(f(i))) &
(!j. j ~: range(f) --> nf(j)= None) &
(!i. nf(i)=None --> (nf (Suc i)) = None) "


(* All the traces of an ioa *)

traces_def:
"traces(ioa) == {trace. ? tr. trace=NF(tr) & has_trace ioa tr}"

(*
traces_def:
"traces(ioa) == {tr. has_trace ioa tr}"
*)


compat_asigs_def:
"compat_asigs a1 a2 ==
(((outputs(a1) Int outputs(a2)) = {}) &
((internals(a1) Int actions(a2)) = {}) &
((internals(a2) Int actions(a1)) = {}))"



compat_ioas_def:
"compat_ioas ioa1 ioa2 == compat_asigs (asig_of(ioa1)) (asig_of(ioa2))"


asig_comp_def:
"asig_comp a1 a2 ==
(((inputs(a1) Un inputs(a2)) - (outputs(a1) Un outputs(a2)),
(outputs(a1) Un outputs(a2)),
(internals(a1) Un internals(a2))))"



par_def:
"(ioa1 || ioa2) ==
(asig_comp (asig_of ioa1) (asig_of ioa2),
{pr. fst(pr):starts_of(ioa1) & snd(pr):starts_of(ioa2)},
{tr. let s = fst(tr); a = fst(snd(tr)); t = snd(snd(tr))
in (a:actions(asig_of(ioa1)) | a:actions(asig_of(ioa2))) &
(if a:actions(asig_of(ioa1)) then
(fst(s),a,fst(t)):trans_of(ioa1)
else fst(t) = fst(s))
&
(if a:actions(asig_of(ioa2)) then
(snd(s),a,snd(t)):trans_of(ioa2)
else snd(t) = snd(s))})"



restrict_asig_def:
"restrict_asig asig actns ==
(inputs(asig) Int actns, outputs(asig) Int actns,
internals(asig) Un (externals(asig) - actns))"



restrict_def:
"restrict ioa actns ==
(restrict_asig (asig_of ioa) actns, starts_of(ioa), trans_of(ioa))"



ioa_implements_def:
"ioa_implements ioa1 ioa2 ==
((inputs(asig_of(ioa1)) = inputs(asig_of(ioa2))) &
(outputs(asig_of(ioa1)) = outputs(asig_of(ioa2))) &
traces(ioa1) <= traces(ioa2))"


rename_def:
"rename ioa ren ==
(({b. ? x. Some(x)= ren(b) & x : inputs(asig_of(ioa))},
{b. ? x. Some(x)= ren(b) & x : outputs(asig_of(ioa))},
{b. ? x. Some(x)= ren(b) & x : internals(asig_of(ioa))}),
starts_of(ioa) ,
{tr. let s = fst(tr); a = fst(snd(tr)); t = snd(snd(tr))
in
? x. Some(x) = ren(a) & (s,x,t):trans_of(ioa)})"



declare Let_def [simp]

lemmas ioa_projections = asig_of_def starts_of_def trans_of_def
and exec_rws = executions_def is_execution_fragment_def

lemma ioa_triple_proj:
"asig_of(x,y,z) = x & starts_of(x,y,z) = y & trans_of(x,y,z) = z"
apply (simp add: ioa_projections)
done

lemma trans_in_actions:
"[| IOA(A); (s1,a,s2):trans_of(A) |] ==> a:actions(asig_of(A))"
apply (unfold ioa_def state_trans_def actions_def is_asig_def)
apply (erule conjE)+
apply (erule allE, erule impE, assumption)
apply simp
done


lemma filter_oseq_idemp: "filter_oseq p (filter_oseq p s) = filter_oseq p s"
apply (simp add: filter_oseq_def)
apply (rule ext)
apply (case_tac "s i")
apply simp_all
done

lemma mk_trace_thm:
"(mk_trace A s n = None) =
(s(n)=None | (? a. s(n)=Some(a) & a ~: externals(asig_of(A))))
&
(mk_trace A s n = Some(a)) =
(s(n)=Some(a) & a : externals(asig_of(A)))"

apply (unfold mk_trace_def filter_oseq_def)
apply (case_tac "s n")
apply auto
done

lemma reachable_0: "s:starts_of(A) ==> reachable A s"
apply (unfold reachable_def)
apply (rule_tac x = "(%i. None, %i. s)" in bexI)
apply simp
apply (simp add: exec_rws)
done

lemma reachable_n:
"!!A. [| reachable A s; (s,a,t) : trans_of(A) |] ==> reachable A t"
apply (unfold reachable_def exec_rws)
apply (simp del: bex_simps)
apply (simp (no_asm_simp) only: split_tupled_all)
apply safe
apply (rename_tac ex1 ex2 n)
apply (rule_tac x = "(%i. if i<n then ex1 i else (if i=n then Some a else None) , %i. if i<Suc n then ex2 i else t)" in bexI)
apply (rule_tac x = "Suc n" in exI)
apply (simp (no_asm))
apply simp
apply (metis ioa_triple_proj less_antisym)
done


lemma invariantI:
assumes p1: "!!s. s:starts_of(A) ==> P(s)"
and p2: "!!s t a. [|reachable A s; P(s)|] ==> (s,a,t): trans_of(A) --> P(t)"
shows "invariant A P"
apply (unfold invariant_def reachable_def Let_def exec_rws)
apply safe
apply (rename_tac ex1 ex2 n)
apply (rule_tac Q = "reachable A (ex2 n) " in conjunct1)
apply simp
apply (induct_tac n)
apply (fast intro: p1 reachable_0)
apply (erule_tac x = na in allE)
apply (case_tac "ex1 na", simp_all)
apply safe
apply (erule p2 [THEN mp])
apply (fast dest: reachable_n)+
done

lemma invariantI1:
"[| !!s. s : starts_of(A) ==> P(s);
!!s t a. reachable A s ==> P(s) --> (s,a,t):trans_of(A) --> P(t)
|] ==> invariant A P"

apply (blast intro!: invariantI)
done

lemma invariantE:
"[| invariant A P; reachable A s |] ==> P(s)"
apply (unfold invariant_def)
apply blast
done

lemma actions_asig_comp:
"actions(asig_comp a b) = actions(a) Un actions(b)"
apply (auto simp add: actions_def asig_comp_def asig_projections)
done

lemma starts_of_par:
"starts_of(A || B) = {p. fst(p):starts_of(A) & snd(p):starts_of(B)}"
apply (simp add: par_def ioa_projections)
done

(* Every state in an execution is reachable *)
lemma states_of_exec_reachable:
"ex:executions(A) ==> !n. reachable A (snd ex n)"
apply (unfold reachable_def)
apply fast
done


lemma trans_of_par4:
"(s,a,t) : trans_of(A || B || C || D) =
((a:actions(asig_of(A)) | a:actions(asig_of(B)) | a:actions(asig_of(C)) |
a:actions(asig_of(D))) &
(if a:actions(asig_of(A)) then (fst(s),a,fst(t)):trans_of(A)
else fst t=fst s) &
(if a:actions(asig_of(B)) then (fst(snd(s)),a,fst(snd(t))):trans_of(B)
else fst(snd(t))=fst(snd(s))) &
(if a:actions(asig_of(C)) then
(fst(snd(snd(s))),a,fst(snd(snd(t)))):trans_of(C)
else fst(snd(snd(t)))=fst(snd(snd(s)))) &
(if a:actions(asig_of(D)) then
(snd(snd(snd(s))),a,snd(snd(snd(t)))):trans_of(D)
else snd(snd(snd(t)))=snd(snd(snd(s)))))"

(*SLOW*)
apply (simp (no_asm) add: par_def actions_asig_comp prod_eq_iff ioa_projections)
done

lemma cancel_restrict: "starts_of(restrict ioa acts) = starts_of(ioa) &
trans_of(restrict ioa acts) = trans_of(ioa) &
reachable (restrict ioa acts) s = reachable ioa s"

apply (simp add: is_execution_fragment_def executions_def
reachable_def restrict_def ioa_projections)
done

lemma asig_of_par: "asig_of(A || B) = asig_comp (asig_of A) (asig_of B)"
apply (simp add: par_def ioa_projections)
done


lemma externals_of_par: "externals(asig_of(A1||A2)) =
(externals(asig_of(A1)) Un externals(asig_of(A2)))"

apply (simp add: externals_def asig_of_par asig_comp_def
asig_inputs_def asig_outputs_def Un_def set_diff_eq)
apply blast
done

lemma ext1_is_not_int2:
"[| compat_ioas A1 A2; a:externals(asig_of(A1))|] ==> a~:internals(asig_of(A2))"
apply (unfold externals_def actions_def compat_ioas_def compat_asigs_def)
apply auto
done

lemma ext2_is_not_int1:
"[| compat_ioas A2 A1 ; a:externals(asig_of(A1))|] ==> a~:internals(asig_of(A2))"
apply (unfold externals_def actions_def compat_ioas_def compat_asigs_def)
apply auto
done

lemmas ext1_ext2_is_not_act2 = ext1_is_not_int2 [THEN int_and_ext_is_act]
and ext1_ext2_is_not_act1 = ext2_is_not_int1 [THEN int_and_ext_is_act]

end