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Design: age-based time (RFC 9171 Bundle Age), seq in identity hash

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kyle
2026-10-16 17:45:57 -07:00
parent 76f5a6bc77
commit 08f024766c
1 changed files with 22 additions and 13 deletions
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docs/superpowers/specs/2026-10-16-tines-design.md
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@@ -98,17 +98,19 @@ plus a policy.
``` ```
Observation { Observation {
id: ObservationId // content-derived hash of the fields below id: ObservationId // content-derived hash (see below)
observer: NodeId // who saw it observer: NodeId // who saw it
time: Timestamp // when they saw it (observer's clock) seq: u64 // observer-local, never repeats
topic: Topic // key for grouping/trimming, e.g. "door/3" age_ms: u64 // time since observed; mutable, grows per hop
payload: bytes // opaque to tines observed_at: Option<u64> // absolute ms since epoch, if observer had a clock
topic: Topic // key for grouping/trimming, e.g. "door/3"
payload: bytes // opaque to tines
} }
``` ```
Decisions: Decisions:
- `id` is a hash over `(observer, time, topic, payload)`. Two robots that - `id` is a hash over `(observer, seq, topic, payload)`. Two robots that
observe the same thing produce two observations; de-duplication is observe the same thing produce two observations; de-duplication is
by identity, not by meaning. Union is therefore idempotent and by identity, not by meaning. Union is therefore idempotent and
order-independent. An observation is an *event*, not a fact: the same order-independent. An observation is an *event*, not a fact: the same
@@ -119,13 +121,20 @@ Decisions:
core does not provision or persist it. Adapters may derive it from a core does not provision or persist it. Adapters may derive it from a
hardware unique ID (MCU chip UID, Jetson serial) or read it from hardware unique ID (MCU chip UID, Jetson serial) or read it from
config. *(My call.)* config. *(My call.)*
- `time` is the observer's local clock, as `u64` milliseconds since the - `time` is carried as **age, not a timestamp**, following RFC 9171's
Unix epoch, plus a `ClockQuality` tag: `Synced` (GPS/NTP), `FreeRunning` Bundle Age Block. Every observation carries `age_ms: u64`, the elapsed
(set once, drifting), or `BootRelative` (no RTC; ms since boot). The time since it was observed. Each holder increments it by its own
tag travels with the observation so the memory layer can decide how holding time (monotonic tick; every target has one) before forwarding.
much to trust cross-observer recency. `tines` does not attempt clock An observer that has a real clock may additionally set
sync. *(My call: the tag is the minimum needed to make a `observed_at: Option<u64>` (ms since Unix epoch). A receiver with a
`BootRelative` MCU observation honest rather than silently wrong.)* clock can pin a clockless observation at `now − age_ms`. Precision
degrades by each hop's tick error; `tines` does not attempt clock
sync. *(Kyle's suggestion; the RFC mapping and the optional absolute
field are my call.)*
- Because `age_ms` is mutable, it is **not** in the identity hash. The
hash covers `(observer, seq, topic, payload)` where `seq` is an
observer-local monotonic counter that must not repeat across reboots
(persisted, or `boot_count << 32 | counter`). *(My call.)*
- `topic` is a short byte string. Its structure (hierarchy, separators) - `topic` is a short byte string. Its structure (hierarchy, separators)
is application-defined but `tines` supports prefix matching for is application-defined but `tines` supports prefix matching for
trimming and queries. trimming and queries.