Internet-Draft | Managing CBOR numbers in Internet-Drafts | February 2023 |
Bormann | Expires 26 August 2023 | [Page] |
CBOR-based protocols often make use of numbers allocated in a registry. While developing the protocols, those numbers may not yet be available. This impedes the generation of data models and examples that actually can be used by tools.¶
This short draft proposes a common way to handle these situations, without any changes to existing tools. Such changes are very well possible in the future, at which time this draft will be updated.¶
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A CBOR-based protocol might want to define a structure using CDDL [RFC8610][RFC9165], like that in Figure 1 (based on [RFC9290]):¶
problem-details = { ? &(title: -1) => oltext ? &(detail: -2) => oltext ? &(instance: -3) => ~uri ? &(response-code: -4) => uint .size 1 ? &(base-uri: -5) => ~uri ? &(base-lang: -6) => tag38-ltag ? &(base-rtl: -7) => tag38-direction / ... / * (uint .feature "extension") => any }
The key numbers shown in this structure are likely to be intended for allocation in an IANA section.¶
The key numbers will be used in an example in the specification such as shown in Figure 2.¶
{ / title / -1: "title of the error", / detail / -2: "detailed information about the error", / instance / -3: "coaps://pd.example/FA317434", / response-code / -4: 128, / 4.00 / 4711: { / ... / } }
However, during development, these numbers are not yet fixed; they are likely to move around as parts of the specification are added or deleted.¶
What not to do during development:¶
problem-details = { ? "title" => oltext ? "detail" => oltext ? "instance" => ~uri ? "response-code" => uint .size 1 ? "base-uri" => ~uri ? "base-lang" => tag38-ltag ? "base-rtl" => tag38-direction / ... / * (uint .feature "extension") => any }
{ "title": "title of the error", "detail": "detailed information about the error", "instance-code": "coaps://pd.example/FA317434", "response-code": 128, / 4.00 / 4711: { / ... / } }
This makes the model and the examples compile/check out without allocating numbers, but it also leads to several problems:¶
To make the transition to a published document easier, the document is instead written with the convention demonstrated in the following:¶
problem-details = { ? &(title-CPA: -1) => oltext ? &(detail-CPA: -2) => oltext ? &(instance-CPA: -3) => ~uri ? &(response-code-CPA: -4) => uint .size 1 ? &(base-uri-CPA: -5) => ~uri ? &(base-lang-CPA: -6) => tag38-ltag ? &(base-rtl-CPA: -7) => tag38-direction / ... / * (uint .feature "extension") => any }
CPA is short for "code point allocation", and is a reliable search key for finding the places that need to be updated after allocation.An earlier concept for this draft used TBD in place of CPA, as do many draft specifications being worked on today. TBD is better recognized than CPA, but also could be misunderstood to mean further work by the spec developer is required. A document submitted for publications should not really have "TBD" in it.¶
In the IANA section, the table to go into the registry is prepared as follows:¶
Key value | Name | CDDL Type | Brief description | Reference |
---|---|---|---|---|
CPA-1 | title |
text / tag38
|
short, human-readable summary of the problem shape | RFC XXXX |
CPA-2 | detail |
text / tag38
|
human-readable explanation specific to this occurrence of the problem | RFC XXXX |
CPA-3 | instance |
~uri
|
URI reference identifying specific occurrence of the problem | RFC XXXX |
CPA-4 | response-code |
uint .size 1
|
CoAP response code | RFC XXXX |
CPA-5 | base-uri |
~uri
|
Base URI | RFC XXXX |
CPA-6 | base-lang |
tag38-ltag
|
Base language tag (see tag38) | RFC XXXX |
CPA-7 | base-rtl |
tag38-direction
|
Base writing direction (see tag38) | RFC XXXX |
The provisionally made up key numbers will then be used in an example in the specification such as:¶
{ / title-CPA / -1: "title of the error", / detail-CPA / -2: "detailed information about the error", / instance-CPA / -3: "coaps://pd.example/FA317434", / response-code-CPA / -4: 128, / 4.00 / 4711: { / ... / } }
A "removeInRFC" note in the draft points the RFC editor to the present
document so the RFC editor knows what needs to be done at which point.
In the publication process, it is easy to remove the -CPA
suffixes
and CPA
prefixes for the RFC editor while filling in the actual IANA
allocated numbers and removing the note.¶
This document makes no requests of IANA. However, it specifies a procedure that can be followed during draft development that has a specific role for IANA and the interaction between RFC editor and IANA at important points during this development. This procedure is intended to be as little of an onus as possible, but that is the author's assessment only. IANA feedback is therefore requested.¶
The security considerations of [RFC8610] and [RFC8949] apply.¶
This document was motivated by the AUTH48 experience for RFC 9200..RFC 9203. Then, Jaime Jiménez made me finally write this document. Marco Tiloca provided useful comments on an early presentation of this idea.¶