IANA registration of CBOR tag 44252

Status: registered. IANA assigned tag 44252 on 2026-08-19.

This document holds the registration request for CBOR tag 44252 (0xACDC) in the IANA registry "Concise Binary Object Representation (CBOR) Tags" as it was sent, together with what the registry now says. It is kept rather than retired: the request is what the entry means, and a reader who wants to know why the semantics line reads as it does should be able to see it.

Why this is possible without an RFC

The registry defines three registration policies (RFC 8949, Section 9.2):

Tag 44252 lies in the First Come First Served range: no RFC, no working group and no expert review are required. A stable, publicly reachable description of the semantics and a point of contact suffice.

Availability check (2026-08-14): 44252 is unassigned. The nearest neighbours are 43000/43001 (complex numbers); the range 43002..49999 is entirely unassigned. Note that First Come First Served literally means first come, first served — the number is only ours once IANA has recorded it.

Outcome (2026-08-19): recorded. 44252 is now the only assignment between 43002 and 49999, which are otherwise still unassigned on either side.

The request

Submit exactly this template:

Tag:                             44252

Data item:                       array

Semantics (short form):          Metrological value (quantity value with unit
                                 of measure, SI prefix and GUM measurement
                                 uncertainty)

Point of contact:                Achim Friedland <achim.friedland@graphdefined.com>

Description of semantics (URL):  https://github.com/OpenChargingTechnology/Whitepapers/blob/master/MetrologicalCBOR/README.md

The field names follow the templates of existing First Come First Served registrations (verified against the submitted templates of tags 40919 and 41728, which IANA publishes under https://www.iana.org/assignments/cbor-tags/template/<tag>).

How to submit

Use the IANA request form for protocol parameter assignments:

https://www.iana.org/form/protocol-assignment

Select the registry "Concise Binary Object Representation (CBOR) Tags" and paste the template above. Alternatively the request can be mailed to iana@iana.org with the registry name in the subject line. IANA confirms by mail and assigns a ticket number; First Come First Served requests are usually processed within a few business days.

Please check before sending

• The contact details become public. IANA publishes the contact name in the registry's Reference column and the mail address in the archived template (obfuscated, e.g. achim.friedland&graphdefined.com). The address used here is the one already present in every source file header of this repository, so nothing new is disclosed — swap it for a role address if you would rather not have a personal one in the registry.
• The URL is a master branch link. It stays valid as long as the file keeps its path, and it always shows the current specification. If you prefer immutability over currentness, use a commit permalink instead — but then errata will never reach readers of the registry.

What the registry entry says

The published semantics is not word for word the short form drafted above: it reads quantity value rather than quantity, and GUM measurement uncertainty rather than measurement uncertainty. Both are improvements — the first is the VIM term for what the tag actually carries, the second names the guide the uncertainty follows — and the registry is now the authority for that line. Section 8 of README.md quotes the registry, not this request.

After the assignment — done 2026-08-19

1. Note the assignment date in this file and set the status above to registered. Done; there is no ticket number to record, the entry itself is the confirmation.
2. Update Section 8 of README.md from "unassigned" to the assignment. Done, quoting the registry.
3. The tag number needed no code change, as expected: it lives in exactly one place per implementation — CBORTag.MetrologicalValue in CBORTag.cs, whose XML documentation is worded to serve as the registration's semantics text, and METROLOGICAL_VALUE_TAG in the TypeScript implementation.

If 44252 had been taken in the meantime

It was not, and this contingency is closed. The list is kept because it is still the answer to "where does the number appear", which is a question with a different reason to be asked now: an erratum, not a renumbering.

Should IANA report the number as assigned, pick another free number in the First Come First Served range and change CBORTag.MetrologicalValue — that single constant, the specification, this document and the golden vectors in MetrologicalValueTests.cs, the TypeScript implementation's METROLOGICAL_VALUE_TAG constant and the test-vectors annex are the places where the number appears.