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julian 648d3254d6 wiki: valet / over-capacity mode; 'full' is a soft operator policy

Capture that refusing at capacity is the default, not absolute: an operator
may opt into valet over-capacity (customer hands over keys, operator stacks
the car into custody). Manned-only, new custody/session shape. Deferred;
not built into the entry flow. Made capacity-occupancy's FULL gate a soft
policy knob.

2026-06-15 18:32:40 +02:00

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Capacity & Occupancy

How many vehicles are inside, how many spaces remain, and what happens when the lot is full.

Occupancy is a projection (like everything else)

occupancy = count(open [[parking-session|sessions]]) — an entry with no matching exit. It is a fold over the signed append-only-event-chain, never a hand-maintained counter (a counter is editable and drifts; the chain is the truth). Spaces-free = capacity − occupancy.

capacity is admin-set per site (and per zone/level if the lot has sections — model a zone on capacity + on the entry so multi-level is a later addition, not a rewrite).
Permit concurrency (maxConcurrent, see permit) is the same kind of fold, scoped to one permit's open sessions.

Full → refuse entry + FULL sign

When occupancy ≥ capacity, the entry flow refuses (no vehicle_entry, no barrier open) and can drive a "FULL" sign (a relay/output, via the device adapter layer).
Safety/policy nuance: "full" blocks entry only — exit always works (fail-state-safety: exit fails open; never trap a vehicle). Permit holders may be allowed in past a "transient full" threshold (reserve spaces for subscribers) — an optional policy knob.
Counting drift is real: tailgating (two cars, one entry) and missed reads make the live count diverge from physical reality. The count is the system's occupancy; periodic ground-truth (a loop count, or the opencv-anpr-service count) reconciles it — surfaced as an anomaly, not silently corrected.

"Full" is a soft, operator-configurable policy

Refusing at capacity is the default, not an absolute. An operator may opt into valet-overcapacity — accept the car into operator custody (keys handed over, stacked beyond the marked count) instead of refusing. So the FULL gate is a policy knob (refuse vs. valet-accept), set by the operator per site. Valet is a manned-mode feature with its own custody/session shape — see valet-overcapacity (deferred).

Open

Zone/level granularity at launch vs. single capacity number.
Reserve-for-permits threshold.
The valet over-capacity mode + custody model (valet-overcapacity).

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