TLAPS and Coq proof of TwoPC protocol.

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.*.aux
*.a
*.cma
*.cmi
*.cmo
*.cmx
*.cmxa
*.cmxs
*.glob
*.ml.d
*.ml4.d
*.mli.d
*.mllib.d
*.mlpack.d
*.native
*.o
*.v.d
*.vio
*.vo
.coq-native/
.csdp.cache
.lia.cache
.nia.cache
.nlia.cache
.nra.cache
csdp.cache
lia.cache
nia.cache
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(* Copyright (c) 2008-2012, Adam Chlipala
*
* This work is licensed under a
* Creative Commons Attribution-Noncommercial-No Derivative Works 3.0
* Unported License.
* The license text is available at:
* http://creativecommons.org/licenses/by-nc-nd/3.0/
*)
Require Import Eqdep List Omega.
Set Implicit Arguments.
(** A version of [injection] that does some standard simplifications afterward: clear the hypothesis in question, bring the new facts above the double line, and attempt substitution for known variables. *)
Ltac inject H := injection H; clear H; intros; try subst.
(** Try calling tactic function [f] on all hypotheses, keeping the first application that doesn't fail. *)
Ltac appHyps f :=
match goal with
| [ H : _ |- _ ] => f H
end.
(** Succeed iff [x] is in the list [ls], represented with left-associated nested tuples. *)
Ltac inList x ls :=
match ls with
| x => idtac
| (_, x) => idtac
| (?LS, _) => inList x LS
end.
(** Try calling tactic function [f] on every element of tupled list [ls], keeping the first call not to fail. *)
Ltac app f ls :=
match ls with
| (?LS, ?X) => f X || app f LS || fail 1
| _ => f ls
end.
(** Run [f] on every element of [ls], not just the first that doesn't fail. *)
Ltac all f ls :=
match ls with
| (?LS, ?X) => f X; all f LS
| (_, _) => fail 1
| _ => f ls
end.
(** Workhorse tactic to simplify hypotheses for a variety of proofs.
* Argument [invOne] is a tuple-list of predicates for which we always do inversion automatically. *)
Ltac simplHyp invOne :=
(** Helper function to do inversion on certain hypotheses, where [H] is the hypothesis and [F] its head symbol *)
let invert H F :=
(** We only proceed for those predicates in [invOne]. *)
inList F invOne;
(** This case covers an inversion that succeeds immediately, meaning no constructors of [F] applied. *)
(inversion H; fail)
(** Otherwise, we only proceed if inversion eliminates all but one constructor case. *)
|| (inversion H; [idtac]; clear H; try subst) in
match goal with
(** Eliminate all existential hypotheses. *)
| [ H : ex _ |- _ ] => destruct H
(** Find opportunities to take advantage of injectivity of data constructors, for several different arities. *)
| [ H : ?F ?X = ?F ?Y |- ?G ] =>
(** This first branch of the [||] fails the whole attempt iff the arguments of the constructor applications are already easy to prove equal. *)
(assert (X = Y); [ assumption | fail 1 ])
(** If we pass that filter, then we use injection on [H] and do some simplification as in [inject].
* The odd-looking check of the goal form is to avoid cases where [injection] gives a more complex result because of dependent typing, which we aren't equipped to handle here. *)
|| (injection H;
match goal with
| [ |- X = Y -> G ] =>
try clear H; intros; try subst
end)
| [ H : ?F ?X ?U = ?F ?Y ?V |- ?G ] =>
(assert (X = Y); [ assumption
| assert (U = V); [ assumption | fail 1 ] ])
|| (injection H;
match goal with
| [ |- U = V -> X = Y -> G ] =>
try clear H; intros; try subst
end)
(** Consider some different arities of a predicate [F] in a hypothesis that we might want to invert. *)
| [ H : ?F _ |- _ ] => invert H F
| [ H : ?F _ _ |- _ ] => invert H F
| [ H : ?F _ _ _ |- _ ] => invert H F
| [ H : ?F _ _ _ _ |- _ ] => invert H F
| [ H : ?F _ _ _ _ _ |- _ ] => invert H F
(** Use an (axiom-dependent!) inversion principle for dependent pairs, from the standard library. *)
| [ H : existT _ ?T _ = existT _ ?T _ |- _ ] => generalize (inj_pair2 _ _ _ _ _ H); clear H
(** If we're not ready to use that principle yet, try the standard inversion, which often enables the previous rule. *)
| [ H : existT _ _ _ = existT _ _ _ |- _ ] => inversion H; clear H
(** Similar logic to the cases for constructor injectivity above, but specialized to [Some], since the above cases won't deal with polymorphic constructors. *)
| [ H : Some _ = Some _ |- _ ] => injection H; clear H
end.
(** Find some hypothesis to rewrite with, ensuring that [auto] proves all of the extra subgoals added by [rewrite]. *)
Ltac rewriteHyp :=
match goal with
| [ H : _ |- _ ] => rewrite H by solve [ auto ]
end.
(** Combine [autorewrite] with automatic hypothesis rewrites. *)
Ltac rewriterP := repeat (rewriteHyp; autorewrite with core in *).
Ltac rewriter := autorewrite with core in *; rewriterP.
(** This one is just so darned useful, let's add it as a hint here. *)
Hint Rewrite app_ass.
(** Devious marker predicate to use for encoding state within proof goals *)
Definition done (T : Type) (x : T) := True.
(** Try a new instantiation of a universally quantified fact, proved by [e].
* [trace] is an accumulator recording which instantiations we choose. *)
Ltac inster e trace :=
(** Does [e] have any quantifiers left? *)
match type of e with
| forall x : _, _ =>
(** Yes, so let's pick the first context variable of the right type. *)
match goal with
| [ H : _ |- _ ] =>
inster (e H) (trace, H)
| _ => fail 2
end
| _ =>
(** No more quantifiers, so now we check if the trace we computed was already used. *)
match trace with
| (_, _) =>
(** We only reach this case if the trace is nonempty, ensuring that [inster] fails if no progress can be made. *)
match goal with
| [ H : done (trace, _) |- _ ] =>
(** Uh oh, found a record of this trace in the context! Abort to backtrack to try another trace. *)
fail 1
| _ =>
(** What is the type of the proof [e] now? *)
let T := type of e in
match type of T with
| Prop =>
(** [e] should be thought of as a proof, so let's add it to the context, and also add a new marker hypothesis recording our choice of trace. *)
generalize e; intro;
assert (done (trace, tt)) by constructor
| _ =>
(** [e] is something beside a proof. Better make sure no element of our current trace was generated by a previous call to [inster], or we might get stuck in an infinite loop! (We store previous [inster] terms in second positions of tuples used as arguments to [done] in hypotheses. Proofs instantiated by [inster] merely use [tt] in such positions.) *)
all ltac:(fun X =>
match goal with
| [ H : done (_, X) |- _ ] => fail 1
| _ => idtac
end) trace;
(** Pick a new name for our new instantiation. *)
let i := fresh "i" in (pose (i := e);
assert (done (trace, i)) by constructor)
end
end
end
end.
(** After a round of application with the above, we will have a lot of junk [done] markers to clean up; hence this tactic. *)
Ltac un_done :=
repeat match goal with
| [ H : done _ |- _ ] => clear H
end.
Require Import JMeq.
(** A more parameterized version of the famous [crush]. Extra arguments are:
* - A tuple-list of lemmas we try [inster]-ing
* - A tuple-list of predicates we try inversion for *)
Ltac crush' lemmas invOne :=
(** A useful combination of standard automation *)
let sintuition := simpl in *; intuition; try subst;
repeat (simplHyp invOne; intuition; try subst); try congruence in
(** A fancier version of [rewriter] from above, which uses [crush'] to discharge side conditions *)
let rewriter := autorewrite with core in *;
repeat (match goal with
| [ H : ?P |- _ ] =>
match P with
| context[JMeq] => fail 1 (** JMeq is too fancy to deal with here. *)
| _ => rewrite H by crush' lemmas invOne
end
end; autorewrite with core in *) in
(** Now the main sequence of heuristics: *)
(sintuition; rewriter;
match lemmas with
| false => idtac (** No lemmas? Nothing to do here *)
| _ =>
(** Try a loop of instantiating lemmas... *)
repeat ((app ltac:(fun L => inster L L) lemmas
(** ...or instantiating hypotheses... *)
|| appHyps ltac:(fun L => inster L L));
(** ...and then simplifying hypotheses. *)
repeat (simplHyp invOne; intuition)); un_done
end;
sintuition; rewriter; sintuition;
(** End with a last attempt to prove an arithmetic fact with [omega], or prove any sort of fact in a context that is contradictory by reasoning that [omega] can do. *)
try omega; try (elimtype False; omega)).
(** [crush] instantiates [crush'] with the simplest possible parameters. *)
Ltac crush := crush' false fail.
(** * Wrap Program's [dependent destruction] in a slightly more pleasant form *)
Require Import Program.Equality.
(** Run [dependent destruction] on [E] and look for opportunities to simplify the result.
The weird introduction of [x] helps get around limitations of [dependent destruction], in terms of which sorts of arguments it will accept (e.g., variables bound to hypotheses within Ltac [match]es). *)
Ltac dep_destruct E :=
let x := fresh "x" in
remember E as x; simpl in x; dependent destruction x;
try match goal with
| [ H : _ = E |- _ ] => try rewrite <- H in *; clear H
end.
(** Nuke all hypotheses that we can get away with, without invalidating the goal statement. *)
Ltac clear_all :=
repeat match goal with
| [ H : _ |- _ ] => clear H
end.
(** Instantiate a quantifier in a hypothesis [H] with value [v], or, if [v] doesn't have the right type, with a new unification variable.
* Also prove the lefthand sides of any implications that this exposes, simplifying [H] to leave out those implications. *)
Ltac guess v H :=
repeat match type of H with
| forall x : ?T, _ =>
match type of T with
| Prop =>
(let H' := fresh "H'" in
assert (H' : T); [
solve [ eauto 6 ]
| specialize (H H'); clear H' ])
|| fail 1
| _ =>
specialize (H v)
|| let x := fresh "x" in
evar (x : T);
let x' := eval unfold x in x in
clear x; specialize (H x')
end
end.
(** Version of [guess] that leaves the original [H] intact *)
Ltac guessKeep v H :=
let H' := fresh "H'" in
generalize H; intro H'; guess v H'.

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(* Forward chaining of applications, to facilitate "saturating" the known facts
without specializing. See Clément's thesis
http://pit-claudel.fr/clement/MSc/#org036d20e for a nicer explanation.
*)
Inductive Learnt {P:Prop} :=
| AlreadyLearnt (H:P).
Local Ltac learn_fact H :=
let P := type of H in
lazymatch goal with
(* matching the type of H with the Learnt hypotheses means the
learning fails even when the proposition is known by a different
but unifiable type term *)
| [ Hlearnt: @Learnt P |- _ ] =>
fail 0 "already knew" P "through" Hlearnt
| _ => pose proof H; pose proof (AlreadyLearnt H)
end.
Tactic Notation "learn" constr(H) := learn_fact H.

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# Makefile originally taken from coq-club.
%: Makefile.coq phony
+make -f Makefile.coq $@
all: Makefile.coq
+make -f Makefile.coq all
clean: Makefile.coq
+make -f Makefile.coq clean
rm -f Makefile.coq
Makefile.coq: _CoqProject Makefile
coq_makefile -f _CoqProject | sed 's/$$(COQCHK) $$(COQCHKFLAGS) $$(COQLIBS)/$$(COQCHK) $$(COQCHKFLAGS) $$(subst -Q,-R,$$(COQLIBS))/' > Makefile.coq
_CoqProject:
Makefile:
.PHONY: all clean

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Require Import List Bool Arith.
Require Import TwoPC.Crush TwoPC.Learn.
(** The collection of resource managers (RM). *)
Axiom RM : Type.
(** Assumes two RMs are distinguishable. *)
Axiom RMDecidable :
forall x y : RM, { x = y } + { x <> y }.
Inductive RMState : Set :=
RMWorking | RMPrepared | RMCommitted | RMAborted.
Inductive TMState : Set :=
| TMInit | TMCommitted | TMAborted.
Inductive Message : Type :=
MsgPrepared : RM -> Message
| MsgCommit | MsgAbort.
Record State := {
rmState : RM -> RMState;
tmState : TMState;
tmPrepared : RM -> bool;
msgs : list Message
}.
Inductive StateInit : State -> Prop :=
| InitIntro :
forall (rmInit : RM -> RMState) (tmPreparedInit : RM -> bool),
(forall rm, rmInit rm = RMWorking /\ tmPreparedInit rm = false) ->
StateInit {| rmState := rmInit;
tmState := TMInit;
tmPrepared := tmPreparedInit;
msgs := nil |}.
Inductive StateStep : State -> State -> Prop :=
| TMRcvPrepared :
forall rm rmState tmState msgs tmPrepared tmPrepared',
tmState = TMInit ->
In (MsgPrepared rm) msgs ->
(forall rm0, rm0 <> rm -> tmPrepared rm0 = tmPrepared' rm0) ->
tmPrepared' rm = true ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared';
msgs := msgs |}
| TMCommit :
forall rmState tmState tmState' tmPrepared msgs msgs',
tmState = TMInit ->
(forall rm, tmPrepared rm = true) ->
tmState' = TMCommitted ->
msgs' = cons MsgCommit msgs ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState;
tmState := tmState';
tmPrepared := tmPrepared;
msgs := msgs' |}
| TMAbort :
forall rmState tmState tmState' tmPrepared msgs msgs',
tmState = TMInit ->
tmState' = TMAborted ->
msgs' = cons MsgAbort msgs ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState;
tmState := tmState';
tmPrepared := tmPrepared;
msgs := msgs' |}
| RMPrepare :
forall rm rmState rmState' tmState tmPrepared msgs msgs',
rmState rm = RMWorking ->
(forall rm0, rm0 <> rm -> rmState rm0 = rmState' rm0) ->
rmState' rm = RMPrepared ->
msgs' = cons (MsgPrepared rm) msgs ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState';
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs' |}
| RMChooseToAbort :
forall rm rmState rmState' tmState tmPrepared msgs,
rmState rm = RMWorking ->
(forall rm0, rm0 <> rm -> rmState rm0 = rmState' rm0) ->
rmState' rm = RMAborted ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState';
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
| RMRcvCommitMsg :
forall rm rmState rmState' tmState tmPrepared msgs,
In MsgCommit msgs ->
(forall rm0, rm0 <> rm -> rmState rm0 = rmState' rm0) ->
rmState' rm = RMCommitted ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState';
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
| RMRcvAbortMsg :
forall rm rmState rmState' tmState tmPrepared msgs,
In MsgAbort msgs ->
(forall rm0, rm0 <> rm -> rmState rm0 = rmState' rm0) ->
rmState' rm = RMAborted ->
StateStep {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}
{| rmState := rmState';
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}.
Inductive StateMultiStep : State -> State -> Prop :=
| StateMultiStep0 :
forall state,
StateMultiStep state state
| StateMultiStep1 :
forall state state1 state2,
StateMultiStep state1 state2 ->
StateMultiStep state state1 ->
StateMultiStep state state2.
Inductive Consistency : State -> Prop :=
| ConsistencyIntro :
forall rmState tmState tmPrepared msgs,
( (* if one RM is committed, other RMs cannot be aborted. *)
(exists rm, rmState rm = RMCommitted) ->
(forall rm, rmState rm <> RMAborted)
) ->
( (* if one RM is aborted, other RMs cannot be committed. *)
(exists rm, rmState rm = RMAborted) ->
(forall rm, rmState rm <> RMCommitted)
) ->
Consistency {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}.
Inductive Invariant : State -> Prop :=
| InvariantIntro :
forall rmState tmState tmPrepared msgs,
(
tmState = TMInit -> (* 1PC *)
(
(forall rm, rmState rm <> RMCommitted) /\
(forall rm, (In (MsgPrepared rm) msgs <-> rmState rm = RMPrepared)) /\
(forall rm, tmPrepared rm = true -> rmState rm = RMPrepared)
)
) ->
( (* 2PC: Commit *)
tmState = TMCommitted ->
(
forall rm, rmState rm = RMCommitted \/ rmState rm = RMPrepared
)
) ->
( (* 2PC: Abort *)
tmState = TMAborted ->
(
forall rm, rmState rm <> RMCommitted
)
) ->
( (* Abort message in message list <==> TM is aborted *)
In MsgAbort msgs <-> tmState = TMAborted
) ->
( (* Committed message in message list <==> TM is committed *)
In MsgCommit msgs <-> tmState = TMCommitted
) ->
Invariant {| rmState := rmState;
tmState := tmState;
tmPrepared := tmPrepared;
msgs := msgs |}.
Ltac inst_rm x :=
repeat
( match goal with
| [ H: forall rm, _ |- _ ] => learn (H x)
end
);
repeat
( match goal with
| [ H : Learnt |- _ ] => clear H
end
).
Ltac invert H := inversion H; subst; clear H.
Lemma InvariantImpliesConsistency :
forall state, Invariant state -> Consistency state.
Proof.
intros.
invert H. constructor; crush.
+ destruct tmState0; crush;
try (inst_rm x; crush);
try (inst_rm rm; crush).
+ destruct tmState0; crush;
try (inst_rm x; crush);
try (inst_rm rm; crush).
Qed.
Lemma InitStateSatisfiesInvariant :
forall state, StateInit state -> Invariant state.
Proof.
intros.
invert H; constructor; crush;
try (inst_rm x); try (inst_rm rm); crush.
Qed.
Lemma StateStepKeepsInvariant :
forall state state',
StateStep state state' ->
Invariant state ->
Invariant state'.
Proof.
intros.
invert H0; invert H.
+ constructor; crush.
destruct (RMDecidable rm0 rm).
- inst_rm rm; crush.
- inst_rm rm0; eauto.
+ constructor; crush.
+ constructor; crush.
+ destruct tmState0.
- constructor; crush;
destruct (RMDecidable rm0 rm); crush; inst_rm rm; inst_rm rm0; crush.
- crush. inst_rm rm; crush.
- constructor; crush;
destruct (RMDecidable rm0 rm); crush; inst_rm rm; inst_rm rm0; crush.
+ destruct tmState0.
- constructor; crush;
destruct (RMDecidable rm0 rm); crush; inst_rm rm; inst_rm rm0; crush.
- crush. inst_rm rm; crush.
- constructor; crush;
destruct (RMDecidable rm0 rm); crush; inst_rm rm; inst_rm rm0; crush.
+ constructor; crush.
destruct (RMDecidable rm0 rm).
- crush.
- inst_rm rm0; crush.
left; crush.
right; crush.
+ constructor; crush.
destruct (RMDecidable rm0 rm).
- crush.
- inst_rm rm0; crush.
Qed.
Lemma Safety' :
forall state state',
StateMultiStep state state' ->
Invariant state ->
Invariant state'.
Proof.
induction 1; crush.
Qed.
Theorem Safety :
forall state state',
StateMultiStep state state' ->
StateInit state ->
Consistency state'.
Proof.
intros.
apply InvariantImpliesConsistency.
apply InitStateSatisfiesInvariant in H0.
eapply Safety'; eauto.
Qed.

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-R . TwoPC
TwoPC.v
Learn.v
Crush.v

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-------------------------------- MODULE TwoPC --------------------------------
EXTENDS TLAPS
CONSTANTS RM, RMState, TMState, Msgs
VARIABLES rmState, tmState, tmPrepared, msgs
vars == <<rmState, tmState, tmPrepared, msgs>>
AXIOM RMStateAxiom ==
/\ RMState = {"working", "prepared", "committed", "aborted"}
AXIOM TMStateAxiom ==
/\ TMState = {"init", "committed", "aborted"}
AXIOM MsgsAxiom ==
/\ Msgs = [type: {"prepared"}, rm: RM] \union [type: {"commit", "abort"}]
ExistAbortMsg ==
/\ [type |-> "abort"] \in msgs
ExistCommitMsg ==
/\ [type |-> "commit"] \in msgs
Init ==
/\ rmState = [rm \in RM |-> "working"]
/\ tmState = "init"
/\ tmPrepared = {}
/\ msgs = {}
TMRcvPrepared(rm) ==
/\ tmState = "init"
/\ [type |-> "prepared", rm |-> rm] \in msgs
/\ tmPrepared' = tmPrepared \union {rm}
/\ UNCHANGED <<rmState, tmState, msgs>>
TMCommit ==
/\ tmState = "init"
/\ tmPrepared = RM
/\ tmState' = "committed"
/\ msgs' = msgs \union {[type |-> "commit"]}
/\ UNCHANGED <<rmState, tmPrepared>>
TMAbort ==
/\ tmState = "init"
/\ tmState' = "aborted"
/\ msgs' = msgs \union {[type |-> "abort"]}
/\ UNCHANGED <<rmState, tmPrepared>>
RMPrepare(rm) ==
/\ rmState[rm] = "working"
/\ rmState' = [rmState EXCEPT ![rm] = "prepared"]
/\ msgs' = msgs \union {[type |-> "prepared", rm |-> rm]}
/\ UNCHANGED <<tmState, tmPrepared>>
RMChooseToAbort(rm) ==
/\ rmState[rm] = "working"
/\ rmState' = [rmState EXCEPT ![rm] = "aborted"]
/\ UNCHANGED <<tmState, tmPrepared, msgs>>
RMRcvCommitMsg(rm) ==
/\ ExistCommitMsg
/\ rmState' = [rmState EXCEPT ![rm] = "committed"]
/\ UNCHANGED <<tmState, tmPrepared, msgs>>
RMRcvAbortMsg(rm) ==
/\ ExistAbortMsg
/\ rmState' = [rmState EXCEPT ![rm] = "aborted"]
/\ UNCHANGED <<tmState, tmPrepared, msgs>>
RMOp(rm) ==
\/ TMRcvPrepared(rm)
\/ RMPrepare(rm)
\/ RMChooseToAbort(rm)
\/ RMRcvCommitMsg(rm)
\/ RMRcvAbortMsg(rm)
ChooseRMOp ==
/\ \E rm \in RM:
/\ RMOp(rm)
Next ==
\/ TMCommit
\/ TMAbort
\/ ChooseRMOp
Spec == Init /\ [][Next]_vars
RMStateTypeInvariant ==
/\ rmState \in [RM -> RMState]
TMStateTypeInvariant ==
/\ tmState \in TMState
TMPreparedTypeInvariant ==
/\ tmPrepared \subseteq RM
MsgsTypeInvariant ==
/\ msgs \subseteq Msgs
TypeInvariant ==
/\ RMStateTypeInvariant
/\ TMStateTypeInvariant
/\ TMPreparedTypeInvariant
/\ MsgsTypeInvariant
ExistCommittedRM ==
/\ \E rm \in RM: rmState[rm] = "committed"
ExistAbortedRM ==
/\ \E rm \in RM: rmState[rm] = "aborted"
Consistency ==
/\ ExistCommittedRM => ~ExistAbortedRM
/\ ExistAbortedRM => ~ExistCommittedRM
Invariant ==
/\ TypeInvariant
/\ ( tmState = "init" =>
( /\ \A rm \in RM : rmState[rm] # "committed"
/\ \A rm \in RM : [type |-> "prepared", rm |-> rm] \in msgs <=> rmState[rm] = "prepared"
/\ \A rm \in tmPrepared : rmState[rm] = "prepared" )
)
/\ ( tmState = "committed" =>
( /\ \A rm \in RM : (rmState[rm] = "committed" \/ rmState[rm] = "prepared") )
)
/\ ( tmState = "aborted" =>
( /\ \A rm \in RM : rmState[rm] # "committed" )
)
/\ tmState = "committed" <=> ExistCommitMsg
/\ tmState = "aborted" <=> ExistAbortMsg
LEMMA InvariantImpliesConsistency ==
Invariant => Consistency
<1> USE DEF TypeInvariant, TMStateTypeInvariant, RMStateTypeInvariant, TMPreparedTypeInvariant, MsgsTypeInvariant
<1> USE DEF Invariant, Consistency
<1> USE DEF ExistCommittedRM, ExistAbortedRM
<1>a CASE tmState = "init"
<2> QED BY <1>a, RMStateAxiom
<1>b CASE tmState = "committed"
<2> QED BY <1>b, RMStateAxiom
<1>c CASE tmState = "aborted"
<2> QED BY <1>c, RMStateAxiom
<1> QED BY <1>a, <1>b, <1>c, TMStateAxiom
LEMMA InitStateSatisfiesInvariant ==
Init => Invariant
<1> USE DEF TypeInvariant, TMStateTypeInvariant, RMStateTypeInvariant, TMPreparedTypeInvariant, MsgsTypeInvariant
<1> USE DEF Init, Invariant, ExistCommitMsg, ExistAbortMsg
<1> QED BY TMStateAxiom, RMStateAxiom, MsgsAxiom
LEMMA StateStepKeepsInvariant ==
Invariant /\ Next => Invariant'
<1> USE DEF TypeInvariant, TMStateTypeInvariant, RMStateTypeInvariant, TMPreparedTypeInvariant, MsgsTypeInvariant
<1> USE DEF Invariant, Next
<1> USE DEF ExistCommitMsg, ExistAbortMsg
<1> USE DEF TMCommit, TMAbort, ChooseRMOp
<1> USE DEF RMOp, TMRcvPrepared, RMPrepare, RMChooseToAbort, RMRcvCommitMsg, RMRcvAbortMsg
<1> USE TMStateAxiom, RMStateAxiom, MsgsAxiom
<1>a CASE TMCommit BY <1>a
<1>b CASE TMAbort BY <1>b
<1>c CASE ChooseRMOp
<2> PICK rm \in RM : RMOp(rm) BY <1>c
<2>a CASE TMRcvPrepared(rm) BY <2>a
<2>b CASE RMPrepare(rm) BY <2>b
<2>c CASE RMChooseToAbort(rm) BY <2>c
<2>d CASE RMRcvCommitMsg(rm) BY <2>d
<2>e CASE RMRcvAbortMsg(rm) BY <2>e
<2> QED BY <2>a, <2>b, <2>c, <2>d, <2>e
<1> QED BY <1>a, <1>b, <1>c
THEOREM Safety ==
Spec => []Consistency
<1> SUFFICES Spec => []Invariant BY InvariantImpliesConsistency, PTL
<1> SUFFICES ASSUME Init /\ [][Next]_vars PROVE []Invariant BY DEF Spec
<1> QED BY InitStateSatisfiesInvariant, StateStepKeepsInvariant, PTL
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