julian
9a4c7ee27b
Correction before schema work: the events table conflated the anti-fraud business ledger with device telemetry. Decision: ledger_events (signed, chained, reconciled) holds only business facts; device_events (unsigned, prunable) holds relay/printer/camera/reader/input telemetry. A raw button press is telemetry; the entry flow mints a signed vehicle_entry. Drops input_received-as-signed-event. New: decisions/event-streams-split, concepts/device-events; updated append-only-event-chain, index, log.
46 lines
1.9 KiB
Markdown
46 lines
1.9 KiB
Markdown
---
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type: concept
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tags: [parking, devices, monitoring, telemetry]
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sources: []
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updated: 2026-06-15
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status: open
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---
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# Device Events (telemetry)
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The **unsigned** operational record of what the hardware did and reported — distinct from the
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signed business [[append-only-event-chain|ledger]] (see [[event-streams-split]]). For monitoring,
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diagnostics, and live booth status — **not** anti-fraud.
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## What lands here
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- **Relays/barriers:** relay fired/released, pulseOpen issued (the *device-side* echo; the
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authoritative `barrier_open_command` is a signed ledger event).
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- **Printers:** paper-out / near-end / cover-open / cutter / offline (already polled —
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[[printer-status-monitoring]]).
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- **Cameras:** reachable/offline, snapshot success/failure ([[lpr-camera]]).
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- **Readers / inputs:** a raw read, raw input edges (Dingtian button `input N on/off` —
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[[device-input-flow]]).
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## Properties
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- **Unsigned, not chained** — no `prevHash`/`signature`. It's telemetry, so it carries none of the
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ledger's integrity machinery.
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- **Disposable** — high-volume and churny; **may rotate/prune** on a retention policy (the ledger
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never does).
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- **Device-keyed** — references the `lane_devices` instance; `lane` resolved via the same `LaneMap`
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as before. Stores raw device provenance.
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## The boundary that matters
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A device event is *evidence the host saw something happen*; it does **not** by itself authorize or
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record a business fact. A button press here becomes a **signed `vehicle_entry`** in the ledger only
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after the entry flow runs (ticket + barrier command). This keeps device chatter on the device side
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of the [[device-adapter-pattern|adapter boundary]] and the signed ledger focused on money/access.
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## Open
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- Retention/rotation policy (size- or age-based).
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- Whether any witness-grade device fact (e.g. a loop-sensor `barrier_open_observed`) should *also*
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write a signed ledger entry for [[reconciliation]] — see [[append-only-event-chain]].
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