Managing CBOR numbers in Internet-Drafts
draft-bormann-cbor-draft-numbers-03
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Carsten Bormann | ||
| Last updated | 2024-02-29 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-bormann-cbor-draft-numbers-03
Network Working Group C. Bormann
Internet-Draft Universität Bremen TZI
Intended status: Informational 29 February 2024
Expires: 1 September 2024
Managing CBOR numbers in Internet-Drafts
draft-bormann-cbor-draft-numbers-03
Abstract
CBOR-based protocols often make use of numbers allocated in a
registry. During development of 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. Also, in conjunction with the
application-oriented EDN literal "e", a further reduction in
editorial processing of CBOR examples around the time of approval can
be achieved.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 1 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Problem . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The Anti-Pattern . . . . . . . . . . . . . . . . . . . . . . 3
4. What to do during spec development . . . . . . . . . . . . . 4
4.1. Documents with Significant Generated Content Depending on
Assignments . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Reducing the editorial workload with CDDL definitions . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security considerations . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
(Please see abstract.) [RFC8949] [I-D.bormann-cbor-e-ref]
2. The Problem
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
}
Figure 1: CDDL data model, final form
The key numbers shown in this structure are likely to be intended for
allocation in an IANA section.
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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: {
/ ... /
}
}
Figure 2: CBOR-diag example, final form
However, during development, these numbers are not yet fixed; they
are likely to move around as parts of the specification are added or
deleted.
3. The Anti-Pattern
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
}
Figure 3: CDDL data model, muddled form
{
"title": "title of the error",
"detail": "detailed information about the error",
"instance-code": "coaps://pd.example/FA317434",
"response-code": 128, / 4.00 /
4711: {
/ ... /
}
}
Figure 4: CBOR-diag example, muddled form
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This makes the model and the examples compile/check out even before
having allocated the actually desired numbers, but it also leads to
several problems:
* It becomes hard to assess what the storage/transmission cost of
these structures will be.
* What is being checked in the CI (continuous integration) for the
document is rather different from the final form.
* Draft implementations trying to make use of these provisional
structures have to cater for text strings, which may not actually
be needed in the final form (which might expose specification bugs
once numbers are used, too late in the process).
* The work needed to put in the actual numbers, once allocated, is
significant and error-prone.
* It is not certain the CI system used during development can
interact with the RFC editor's way of editing the document for
publication.
4. What to do during spec development
To make the transition to a published document easier, the document
is instead written with the convention demonstrated in the following
example:
// This document uses the keys for a map as an example. Other such
// constructs involving assigned numbers might also require temporary
// values for exposition in a specification, e.g., CBOR tags. For
// the sake of keeping this document short, examples for these are
// not given.
// Including examples of other things that generate the need for
// temporary numbers, like tags, would be good.
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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
}
Figure 5: CDDL data model, development form
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 publication should not really have "TBD" in it.
In the IANA section, the table to go into the registry is prepared as
follows:
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+=====+===============+=================+=================+=========+
|Key | Name | CDDL Type | Brief |Reference|
|value| | | description | |
+=====+===============+=================+=================+=========+
|CPA-1| title | text / tag38 | short, human- |RFC XXXX |
| | | | readable | |
| | | | summary of the | |
| | | | problem shape | |
+-----+---------------+-----------------+-----------------+---------+
|CPA-2| detail | text / tag38 | human-readable |RFC XXXX |
| | | | explanation | |
| | | | specific to | |
| | | | this | |
| | | | occurrence of | |
| | | | the problem | |
+-----+---------------+-----------------+-----------------+---------+
|CPA-3| instance | ~uri | URI reference |RFC XXXX |
| | | | identifying | |
| | | | specific | |
| | | | occurrence of | |
| | | | the problem | |
+-----+---------------+-----------------+-----------------+---------+
|CPA-4| response-code | uint .size 1 | CoAP response |RFC XXXX |
| | | | code | |
+-----+---------------+-----------------+-----------------+---------+
|CPA-5| base-uri | ~uri | Base URI |RFC XXXX |
+-----+---------------+-----------------+-----------------+---------+
|CPA-6| base-lang | tag38-ltag | Base language |RFC XXXX |
| | | | tag (see | |
| | | | tag38) | |
+-----+---------------+-----------------+-----------------+---------+
|CPA-7| base-rtl | tag38-direction | Base writing |RFC XXXX |
| | | | direction (see | |
| | | | tag38) | |
+-----+---------------+-----------------+-----------------+---------+
Table 1: IANA table, development form
The provisionally made up key numbers will then be used in an example
in the specification such as:
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{
/ 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: {
/ ... /
}
}
Figure 6: CBOR-diag example, development form
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.
Note that in Table 1, the first column uses the name "CPA-1" for a
value that in the rest of the document is assumed to be "-1" (and
indicating a preference by the document author for this number); IANA
as well as the designated experts involved are expected by the
present document to decode this notation.
A "removeInRFC" note to the RFC Editor for Table 1 could have this
approximate contents: This document uses the CPA (code point
allocation) convention described in
[I-D.bormann-cbor-draft-numbers]. For each entry, please remove
the prefix "CPA" from the indicated value of the column
<REG_COLUMN>, and replace the residue with the value assigned by
IANA; perform the same substitution for all other occurrences of
the prefix "CPA" in the document. Finally, please remove this
note.
A "removeInRFC" note to the RFC Editor for Figure 6 could have
this approximate contents: This document uses the CPA (code point
allocation) convention described in
[I-D.bormann-cbor-draft-numbers]. For each item whose key textual
identifier has suffix "-CPA", please remove the suffix. Then,
consider the residue of the suffix removal, and replace the key
numeric identifier with the value assigned by IANA in the
<REG_COLUMN_1> of the registry <REG_NAME>, for the entry where the
value in the <REG_COLUMN_2> is equal to the residue. Finally,
please remove this note.
The RFC editor with IANA would then execute these instructions as
shown in Table 2 and Figure 7 (assuming the unlikely case that all
numbers allocated are ten times the number proposed):
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+=====+===============+=================+=================+=========+
|Key | Name | CDDL Type | Brief |Reference|
|value| | | description | |
+=====+===============+=================+=================+=========+
|-10 | title | text / tag38 | short, human- |RFC XXXX |
| | | | readable | |
| | | | summary of the | |
| | | | problem shape | |
+-----+---------------+-----------------+-----------------+---------+
|-20 | detail | text / tag38 | human-readable |RFC XXXX |
| | | | explanation | |
| | | | specific to | |
| | | | this | |
| | | | occurrence of | |
| | | | the problem | |
+-----+---------------+-----------------+-----------------+---------+
|-30 | instance | ~uri | URI reference |RFC XXXX |
| | | | identifying | |
| | | | specific | |
| | | | occurrence of | |
| | | | the problem | |
+-----+---------------+-----------------+-----------------+---------+
|-40 | response-code | uint .size 1 | CoAP response |RFC XXXX |
| | | | code | |
+-----+---------------+-----------------+-----------------+---------+
|-50 | base-uri | ~uri | Base URI |RFC XXXX |
+-----+---------------+-----------------+-----------------+---------+
|-60 | base-lang | tag38-ltag | Base language |RFC XXXX |
| | | | tag (see | |
| | | | tag38) | |
+-----+---------------+-----------------+-----------------+---------+
|-70 | base-rtl | tag38-direction | Base writing |RFC XXXX |
| | | | direction (see | |
| | | | tag38) | |
+-----+---------------+-----------------+-----------------+---------+
Table 2: IANA table, final form
{
/ title / -10: "title of the error",
/ detail / -20: "detailed information about the error",
/ instance / -30: "coaps://pd.example/FA317434",
/ response-code / -40: 128, / 4.00 /
4711: {
/ ... /
}
}
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Figure 7: CBOR-diag example, final form
4.1. Documents with Significant Generated Content Depending on
Assignments
Many documents have examples (which might even involve signatures
over the contents) that depend on the assignments in more than the
trivial way shown above, and regenerating them may not be easy for
the RFC editor to do.
Therefore, for these documents we need another step involving the
authors:
Immediately after allocation, but before the RFC-Editor EDIT step,
the authors need to regenerate these examples and other generated
content depending on the exact allocations.
In the current process, allocation is usually done after IESG
approval, after IANA action, so we would need to halt the EDIT step
for this regeneration.
Alternatively, we could be more aggressive in invoking some kind of
IANA Early Allocation process, near the end of the IESG review. One
way to do this with current tooling and process is to perform a late
form of actual IANA "Early" Allocation. Or we could amend [BCP9]
and/or [BCP100] in a more fundamental way.
// We probably need an indicator in addition to CPA that signifies an
// example or other text must be regenerated (vs. simply be updated
// by IANA) when proposed numbers are updated by IANA.
4.2. Reducing the editorial workload with CDDL definitions
[I-D.bormann-cbor-e-ref] defines a CBOR diagnostic notation
application extension that allows CBOR diagnostic notation to
reference constants defined in a CDDL model, the e'' application
extension.
If the draft contains a CDDL model that includes definitions of
constants that may then be used in CBOR diagnostic notation, the use
of e'' constant references makes it unnecessary to change the
constant value in the example when final values are defined for these
constants. (This application extension also can make the CBOR
diagnostic notation more readable and less distracting, replacing
constructs such as
/ title-CPA / -1
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by
e'title'
which removes the need to mention "CPA" and to provide a potentially
distracting copy of the value assignment in the example.)
5. IANA Considerations
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.
6. Security considerations
The security considerations of [RFC8610] and [RFC8949] apply.
7. References
7.1. Normative References
[I-D.bormann-cbor-draft-numbers]
Bormann, C., "Managing CBOR numbers in Internet-Drafts",
Work in Progress, Internet-Draft, draft-bormann-cbor-
draft-numbers-02, 2 September 2023,
<https://datatracker.ietf.org/doc/html/draft-bormann-cbor-
draft-numbers-02>.
[I-D.bormann-cbor-e-ref]
Bormann, C., "External References to Values in CBOR
Diagnostic Notation (EDN)", Work in Progress, Internet-
Draft, draft-bormann-cbor-e-ref-00, 29 February 2024,
<https://datatracker.ietf.org/doc/html/draft-bormann-cbor-
e-ref-00>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
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[RFC9165] Bormann, C., "Additional Control Operators for the Concise
Data Definition Language (CDDL)", RFC 9165,
DOI 10.17487/RFC9165, December 2021,
<https://www.rfc-editor.org/rfc/rfc9165>.
7.2. Informative References
[BCP100] Best Current Practice 100,
<https://www.rfc-editor.org/info/bcp100>.
At the time of writing, this BCP comprises the following:
Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
2014, <https://www.rfc-editor.org/info/rfc7120>.
[BCP9] Best Current Practice 9,
<https://www.rfc-editor.org/info/bcp9>.
At the time of writing, this BCP comprises the following:
Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
<https://www.rfc-editor.org/info/rfc2026>.
Dusseault, L. and R. Sparks, "Guidance on Interoperation
and Implementation Reports for Advancement to Draft
Standard", BCP 9, RFC 5657, DOI 10.17487/RFC5657,
September 2009, <https://www.rfc-editor.org/info/rfc5657>.
Housley, R., Crocker, D., and E. Burger, "Reducing the
Standards Track to Two Maturity Levels", BCP 9, RFC 6410,
DOI 10.17487/RFC6410, October 2011,
<https://www.rfc-editor.org/info/rfc6410>.
Resnick, P., "Retirement of the "Internet Official
Protocol Standards" Summary Document", BCP 9, RFC 7100,
DOI 10.17487/RFC7100, December 2013,
<https://www.rfc-editor.org/info/rfc7100>.
Kolkman, O., Bradner, S., and S. Turner, "Characterization
of Proposed Standards", BCP 9, RFC 7127,
DOI 10.17487/RFC7127, January 2014,
<https://www.rfc-editor.org/info/rfc7127>.
Dawkins, S., "Increasing the Number of Area Directors in
an IETF Area", BCP 9, RFC 7475, DOI 10.17487/RFC7475,
March 2015, <https://www.rfc-editor.org/info/rfc7475>.
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Halpern, J., Ed. and E. Rescorla, Ed., "IETF Stream
Documents Require IETF Rough Consensus", BCP 9, RFC 8789,
DOI 10.17487/RFC8789, June 2020,
<https://www.rfc-editor.org/info/rfc8789>.
Rosen, B., "Responsibility Change for the RFC Series",
BCP 9, RFC 9282, DOI 10.17487/RFC9282, June 2022,
<https://www.rfc-editor.org/info/rfc9282>.
[RFC9290] Fossati, T. and C. Bormann, "Concise Problem Details for
Constrained Application Protocol (CoAP) APIs", RFC 9290,
DOI 10.17487/RFC9290, October 2022,
<https://www.rfc-editor.org/rfc/rfc9290>.
Acknowledgements
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. Michael Richardson pointed out the issues
that led to Section 4.1. Carl Wallace provided further comments
shining light on the practical aspects of the proposals.
Author's Address
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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