URML (open robot intent language): recording a validated-intent audit trail as an MCAP channel — request for comment

[idoco2003]

Hi MCAP community,

URML (urml.dev) is a small, Apache-2.0 language for describing robot intent: it validates a request against a capability manifest and a safety envelope, then dispatches. I'm writing because URML produces a structured audit record on every step, and recording it as a first-class MCAP channel would make it replayable, diffable, and visualizable in any MCAP-aware tool -- rather than tied to one viewer.

Nothing here asks the project to adopt, host, or maintain anything. This is a request for comment.

A URML runtime writes one MCAP channel of audit messages: per step, the typed intent, the validator verdict (failing pass + error code when refused), and the dispatched substrate calls, each with a log time. Because MCAP is serialization-agnostic, the audit schema can be JSON Schema (the same program/manifest schemas URML already exports) or protobuf -- no new format invented. A recorded .mcap then opens directly in Lichtblick or any MCAP reader, so the validated-intent stream is portable across the whole ecosystem. (The Foxglove SDK is the natural live-streaming complement; this is about MCAP as the on-disk format.)

Two real questions: (1) Is recording URML's validated-intent audit trail as a dedicated MCAP channel the right pattern (schema-encoded messages on their own channel)? (2) Should the audit schema be advertised as JSON Schema or protobuf for best cross-tool support, and are there conventions for an "intent + verdict" channel that would make it idiomatic for MCAP readers?

Full write-up: https://github.com/URML-MARS/URML/blob/main/docs/rfcs/0466-mcap-outreach.md

Thanks for MCAP; a serialization-agnostic open logging format is exactly the right place to make a validated-intent trail portable.

Ido Yahalomi (URML, greenvh@gmail.com)

AI-assisted prose, maintainer-reviewed before posting (see VIBE.md). Human-only correspondence available on request.