# nb-10 solutions — A procedure with parallel checks

*Checkable against `law test packs/examples/language-demo/procedure`
(6 checked, 6 passed). Identifiers and code as written.*

## 1. A review start attempted while in `Draft`

**Answer: the case stays `Draft` — `current_state(st1, Draft)` is
TRUE_ONLY and any `Filed` or `Review` query is NEITHER.**

`StartReview` declares `from Filed`, and a transition fires only from
its `from` state. An attempt while the case rests in `Draft` finds no
matching step, so it is absorbed with no effect — the same absorption
the `without the set` test shows for a guardless-blocked `File`. State
first, event second: the procedure checks where the case is before it
cares what happened.

## 2. The 44 kW boundary

**Answer: 44 kW derives `tech_ok` (the rule uses `<=`); 45 kW does
not — so 44 kW approves like the 22 kW test, 45 kW blocks like the
120 kW test.**

`TechWithinLimit` fires when `kw <= 44 kW`. A `44 kW` plate satisfies
the comparison, `TechAccept` reaches `TechOk`, both regions are
terminal, and `Decide` yields `Approved` TRUE_ONLY. A `45 kW` plate
fails the comparison exactly as `120 kW` does: `tech_ok` never holds,
the Tech region stays `TechPending`, the join is unsatisfied, and
`Approved` is NEITHER. Boundary included on one side only — `<=`
against the declared 44 kW teaching value.

## 3. Which region finished, and the one missing attempt

**Answer: Docs reached `DocsOk`; Tech stayed `TechPending`. Attempting
`TechAccept` with the `TechApproved` event flips `Approved` to
TRUE_ONLY.**

The join-waits test attempts `DocsAccept` (with `DocsFiled`) but never
attempts `TechAccept`. With the 22 kW plate the guard would hold, so
the single missing ingredient is the attempt itself: add the `tech`
assertion from the ready test — `attempted_transition(st1, TechAccept,
TechApproved { … })` at 13:00 — and both regions are terminal when
`Decide` fires on `ReviewComplete`, giving `Approved` TRUE_ONLY. This
is the article's changed condition in reverse: same setup, one attempt
added, join satisfied.

## 4. Why double filing stays `Filed`

**Answer: the second `File` finds the case already past its `from`
state, so it misfires; only `StartReview` on `ReviewStarted` moves
the case on to `Review`.**

The first attempt carries `Draft → Filed` and fires. The second
attempt names the same transition, whose `from` is `Draft` — but the
case now rests in `Filed`, so the step does not apply and the case
holds. Re-entry is absorbed, never re-executed. Progress needs a
different transition: `StartReview` (`from Filed`, `on
ReviewStarted`), which the ready test attempts at 11:00 to enter the
parallel state.

## 5. The three ingredients of `Decide`, and which the threshold breaks

**Answer: (a) the case rests in `Review` with both regions terminal,
(b) the `ReviewComplete` event is on record, (c) the join sees `DocsOk`
and `TechOk`. The over-threshold test keeps (a)-in-part and (b) but
breaks (c) via the Tech guard.**

Standing: filing and review entry succeeded (22-vs-120 differs only in
the plate), so the case is in `Review`. Event: `Decide` with
`ReviewComplete` at 14:00 is attempted in both tests. Regions: Docs
reaches `DocsOk` in both — but with 120 kW `tech_ok` never holds, so
`TechAccept` misfires, Tech stays `TechPending`, and `join all` refuses
the exit. Add nothing but a passing plate and the twin test `both
regions ready — decision taken` goes TRUE_ONLY.

## How to verify

```sh
law test packs/examples/language-demo/procedure
```

Expected: `итого: 6 проверено, 6 прошли, 0 не прошли, 0 не исполнены`.
The deciding tests are `filing with a complete set`,
`without the set the case stands still`, `re-entry holds the state`,
`both regions ready — decision taken`, `join waits for both regions`,
and `technical conditions above the threshold block the region`.