Version history

Open items. Nothing here is stable; do not implement against this section.

• Compact profile for streaming instrument data (repeated results sharing one header).
• Cross-organisation chain resolution: discovery rules when resolver is absent.
• Proposal to register flow.volumetric and angle quantity names.
• Under discussion: whether valid_until should permit a duration as well as a date.

• Added the supersedes member, replacing the convention of encoding revision information in notes.
• Added canonical CBOR (§6), so a record can move between JSON and CBOR without re-signing.
• Added the application/mtproto-bundle+zip media type.
• Registered frequency and resistance.dc.
• Clarified that traceable_to may be empty only for anchor records; 1.1 left this ambiguous and two implementations read it differently.
• Stated explicitly that consumers must preserve unknown members. This was always the intent but was not normative text.

• Corrected the worked example in §7: the signature was computed over the pre-canonical form.
• Fixed the schema's k constraint, which rejected non-integer coverage factors.
• Editorial: consistent use of “standard uncertainty” throughout.

• Replaced the ad-hoc unit strings of 1.0 with UCUM codes. This was the only breaking-in-practice change in the format's history, and it was worth it.
• Added the optional conditions member.
• Added distribution to quantity objects, defaulting to "normal".
• Made resolver optional and advisory after early deployments showed that mandatory resolution made offline verification impossible.

• First published version: record structure, traceability references, Ed25519 signatures over a canonical JSON form.