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comment(formal) = added various //@LF comments

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Leo Freitas 2024-03-28 16:25:58 +00:00
parent 1044f9d252
commit a3138e7102
1 changed files with 85 additions and 17 deletions
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102
formal/checklist.vdmsl
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@ -26,6 +26,7 @@ values
aircraft = mk_Aircraft(aircraft_panels, {"Before Start" |-> before_start_procedure});
types
--@LF can this be empty? perhaps seq1?
String = seq of char;
-- Aircraft
@ -35,6 +36,7 @@ types
-- 1 means off
SwitchState = <OFF> | <MIDDLE> | <ON>;
--@LF why have a type kist as a rename?
ItemState = SwitchState;
--@doc A switch, with the possible states it can be in, and the state that it is in
@ -42,15 +44,25 @@ types
position : SwitchState
middlePosition : bool
inv s ==
if s.middlePosition = false then
s.position <> <MIDDLE>
else true;
--@LF boolean conditions like these are clearer described as
-- not s.middlePosition => s.position <> <MIDDLE>
-- =
-- (s.position = <MIDDLE> => s.middlePosition)
--
--
--if s.middlePosition = false then
-- s.position <> <MIDDLE>
--else true;
(s.position = <MIDDLE> => s.middlePosition);
-- Knob
Knob ::
position : nat1
states : seq of int
inv k == k.position <= len k.states;
--@LF how can a state be an int? perhaps a proper type (i..e. subset of int range or a union?)
states : seq1 of int
inv k ==
--@LF if k.pos <= len k.states and pos is nat1, then states better be seq1 as well?! It implicitly already is anyhow.
k.position <= len k.states;
Lever = nat
inv t == t <= 100;
@ -59,6 +71,22 @@ types
thrust: Lever
reverser: Lever
inv t ==
--@LF again, this is "programming" not modelling. This one won't turn out as clear as the one for Switch
-- but it is effectively this
--
-- (t.thrust > 0 <=> t.reverser = 0)
--
-- that is, if t.thurst > 0 then t.reverser = 0 and
-- and , if not (t.thurst > 0) then not t.reverser = 0
-- ==
-- if (t.thurst <= 0) then t.reverser <> 0
--
-- coming to think of this, t.reverser is already >= 0 (i.e. it's a nat?).
-- so the else is spurious (i.e. it is a good as "true"). Don't you mean
-- "t.reverser > 0"? (i.e. if thurst is <= 0, then reverser cannot be zero)?
--
-- again, this is concrete example how logic is better to illstrate issue than if-then-else.
-- arguably this is also a matter of taste. But as-is, this seems wrong.
if t.thrust > 0 then
t.reverser = 0
else
@ -72,24 +100,46 @@ types
type : ItemType
object : Switch | Knob | Throttle
inv i ==
--@LF here I would write differently. This is protracted. I would use pattern matching
let type = i.type, object = i.object in
(type = <SWITCH> and is_Switch(object))
or (type = <KNOB> and is_Knob(object))
or (type = <THROTTLE> and is_Throttle(object));
--TODO add check for button
--@LF if type is always inline with the object, then why is it needed?
-- that is, would ItemType come from anywhere else but the way you consutrct object type?
-- this seems redudant (i.e. you just need object union type) perhaps as
ObjectType = Switch | Knob | Throttle;
ItemObject' ::
type : ItemType
object : ObjectType
inv mk_ItemObject'(type, object) ==
cases type:
<SWITCH> -> is_Switch(object),
<KNOB> -> is_Knob(object),
<THROTTLE>-> is_Throttle(object)
end;
--@doc Contains each ItemObject in the Aircraft, e.g. Fuel Pump switch
--@LF then String defintely shouldn't be empty. Otherwise, what does it mean to map empty to something?
-- dores it really need to be string?
Items = map String to ItemObject;
--@doc Contains the panels (all the items in the aircraft) and the checklist
Aircraft ::
items : Items
checklist : Checklist;
--@LF should the domains of these two maps be equal or contained? Should the maps be non-empty?
--e.g.
-- inv mk_Aircraft(i, c) == (dom i = dom c) or (dom i subset dom c); ?
-- Checklist
--@doc Item of a checklist, e.g. Landing gear down
ChecklistItem ::
--@LF again, empty string here doesn't make sense.
procedure : String
type : ItemType
--TODO Check is not only SwitchState
@ -99,16 +149,21 @@ types
--@doc This is the item with the complimentary item in the chcecklist
ItemAndChecklistItem ::
item : ItemObject
--@LF this name is bad. This is not a check list but a check list item! call it checkListItem!
checklist: ChecklistItem
inv i == i.item.type = i.checklist.type;
--@doc A section of a checklist, e.g. Landing Checklist
Procedure = seq of ChecklistItem
--@LF shouldn't this be non-empty? What's the point to map a checklist name to an empty procedure? Yes.
Procedure = seq1 of ChecklistItem
inv p ==
len p > 0 and
--len p > 0 and
--@LF the "trick" for "false not in set S" is neat. It forces a full evaluation, rather than short circuited (i.e. stops at first false).
-- I presume this was intended.
false not in set {
let first = p(x-1).checked, second = p(x).checked in
(first = second) or ((first = true) and (second = false))
--@LF boolean values don't need equality check
(first = second) or (first and not second)--((first = true) and (second = false))
| x in set {2,...,len p}};
--@doc Full checklist, e.g. Startup, Descent, Landing Checklist
@ -119,17 +174,23 @@ functions
--@doc Finds the index of the next item in the procedure that needs to be completed
procedure_next_item_index: Procedure -> nat1
procedure_next_item_index(p) ==
hd [ x | x in set {1,...,len p} & p(x).checked = false]
hd [ x | x in set {1,...,len p} & not p(x).checked ]--p(x).checked = false]
pre
-- Checks procedure has not already been completed
procedure_completed(p) = false
not procedure_completed(p)--procedure_completed(p) = false
post
-- Checks that the index of the item is the next one to be completed
p(RESULT).checked = false
and if RESULT > 1 then
p(RESULT-1).checked = true
else
true;
-- Checks that the index of the item is the next one to be completed
--@LF your def is quite confusing (to me)
--@LF how do you know that RESULT in inds p? Well, the definition above okay.
-- but you can't know whether p(RESULT-1) will! What if RESULT=1? p(RESULT-1)=p(0) which is invalid!
(not p(RESULT).checked)
and
(RESULT > 1 => p(RESULT-1).checked)
--p(RESULT).checked = false
--and if RESULT > 1 then
-- p(RESULT-1).checked = true
--else
-- true;
-- --@doc Checks if all the procedures have been completed
-- check_all_proc_completed: Checklist -> bool
@ -151,13 +212,20 @@ functions
--@doc Checks if the next item in the procedure has been completed
check_proc_item_complete: Procedure * Aircraft -> bool
check_proc_item_complete(p, a) ==
--@LF here you have a nice lemma to prove: procedure_next_item_index(p) in set inds p!
-- I think that's always true
let procItem = p(procedure_next_item_index(p)),
--@LF here you can't tell whether this will be true? i.e. procItem.procedure in set dom a.items?
item = a.items(procItem.procedure) in
--TODO need to be able to check for different types of Items
procItem.check = item.object.position
pre
procedure_completed(p) = false;
procedure_completed(p) = false
--@LF perhaps add
--and
--p(procedure_next_item_index(p)).procedure in set dom a.items?
;
--@doc Marks next item in procedure as complete
mark_proc_item_complete: Procedure -> Procedure