The Use of Non-ASCII Characters in RFCs
draft-rswg-rfc7997bis-02
| Document | Type | Active Internet-Draft (rswg) | |
|---|---|---|---|
| Authors | Paul E. Hoffman , Heather Flanagan | ||
| Last updated | 2024-02-14 | ||
| RFC stream | Editorial | ||
| Intended RFC status | Informational | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | Editorial state | Active editorial stream document | |
| Consensus boilerplate | Unknown | ||
| Document shepherd | (None) |
draft-rswg-rfc7997bis-02
Network Working Group P. Hoffman
Internet-Draft ICANN
Obsoletes: 7997 (if approved) H. Flanagan
Updates: 7322 (if approved) Spherical Cow Consulting
Intended status: Informational 14 February 2024
Expires: 17 August 2024
The Use of Non-ASCII Characters in RFCs
draft-rswg-rfc7997bis-02
Abstract
The RFC Series has evolved to allow for the use of non-ASCII
characters in RFCs. While English remains the required language of
the Series, the encoding of RFCs is now in UTF-8, allowing for a
broader range of characters than typically used in the English
language. This document describes requirements and guidelines for
the RFC Editor regarding the use of non-ASCII characters in RFCs.
This document obsoletes RFC 7997. The differences reflect changes in
the practices of the RFC series since RFC 7997 was published, and
makes further changes based on agreements in the IETF community about
what characters are allowed in RFCs.
[[ A repository for this draft can be found here (https://github.com/
paulehoffman/7997bis). ]]
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 17 August 2024.
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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
and restrictions with respect to this document.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Changes from RFC 7997 . . . . . . . . . . . . . . . . . . 3
2. Basic Requirements for Non-ASCII Text in RFCs . . . . . . . . 4
3. Use of Non-ASCII Text in RFCs . . . . . . . . . . . . . . . . 4
3.1. Person and Company Identification . . . . . . . . . . . . 6
3.2. Keywords and Citation Tags . . . . . . . . . . . . . . . 6
3.3. Non-breaking Spaces and Hyphens . . . . . . . . . . . . . 7
4. XML Markup . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Internationalization Considerations . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
For much of the history of the RFC Series, the character encoding
used for RFCs has been ASCII [RFC20]. This was a sensible choice at
the time: the language of the Series has always been English, a
language that primarily uses ASCII-encoded characters (ignoring for a
moment words borrowed from more richly decorated alphabets); and,
ASCII is the "lowest common denominator" for character encoding,
making cross-platform viewing trivial.
There are limits to ASCII, however, that hinder its continued use as
the exclusive character encoding for the Series. At the time of the
publication of [RFC7997], the increasing need for easily readable,
internationalized content suggested that it is time to allow non-
ASCII characters in RFCs where necessary. To support this move away
from ASCII, RFCs switched to supporting UTF-8 as the default
character encoding and allowed support for a broad range of Unicode
characters [UnicodeCurrent].
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This document describes the rules under which non-ASCII characters
may be used in an RFC. These rules will be applied as the necessary
changes are made to submission checking and editorial tools.
This document updates the RFC Style Guide [RFC7322].
The details included in this document are expected to change based on
experience gained in publishing new RFCs.
1.1. Changes from RFC 7997
The following is an overview of the changes in this document from
[RFC7997]:
* Added the role of the RFC stream approving bodies and the RFC
Production Center (RPC) as described in [RFC9280]. All
responsibilities that were held by the RFC Editor in [RFC7997] are
handled by the RPC. When the RPC has questions about the content
of RFCs, the RPC asks the RFC stream approving bodies for input.
* Removed requirements of marking non-ASCII characters with XML
markup. Clarified that person and names with non-Latin characters
should have Latin transliterations.
* Removed the suggestion that character names for non-ASCII
characters be included, instead relying on the "U+NNNN" syntax
from [BCP137].
* Added the suggestion that non-ASCII characters generally appear in
NFC.
* Added that Non-ASCII text can appear in any part of an RFC.
* The basic requirements in Section 2 were softened to reflect the
realities of the variability of search engines and web browsers.
* Changed Section 3 from "Rules for the Use of Non-ASCII Characters"
to "Use of Non-ASCII Characters" because the RPC has used, and
should continue to use, their own discretion based on what makes
the RFC most useful.
* Language about the future was changed to the past tense to
indicate that [RFC7997] was already implemented. For example,
"RFCs will switch" was changed to to "RFCs switched", and so on.
Also added more acknowledgement of the use of non-ASCII characters
outside the narrow scope that was defined in [RFC7997].
* Updated the requirements on keywords and citation tags.
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* Greatly rearranged and simplified the text about person, company,
and postal names.
* Added text about non-breaking spaces and hypens.
2. Basic Requirements for Non-ASCII Text in RFCs
The following fundamental requirements inform the guidance and
examples provided in this document. They are:
* Searches against RFC indexes and database tables should return
expected results and support appropriate Unicode string matching
behaviors.
* RFCs should be displayed correctly across a wide range of readers
and browsers. People whose systems do not have the fonts needed
to display a particular RFC need to be able to read the various
publication formats and the XML correctly in order to understand
and implement the information described in the document.
* As stated in the RFC Style Guide [RFC7322], the language of the
RFC Series is English.
3. Use of Non-ASCII Text in RFCs
This section describes the guidelines for the use of non-ASCII
characters in an RFC. If the RPC identifies areas where the use of
non-ASCII characters in an RFC negatively impacts the readability of
the text, they can require that the authors supply alternate text or
change the non-ASCII characters to better suit the expected readers
of the RFC. When the RPC has questions about non-ASCII text in RFCs,
the RPC can ask the RFC stream approving bodies for input. The RPC
can also consult the RSAB and the RSWG on such matters.
In general, using the "U+NNNN" syntax from [BCP137] is the suggested
way to show Unicode code points as alternate text.
Characters in an RFC will generally appear in Normalization Form C
(NFC) as defined in [UnicodeNorm]. If the RFC would be more correct
and more understandable with particular characters not in NFC, the
RPC can make an exception and use unnormalized text. In such a case,
a text note should be included to describe why unnormalized text
used.
Non-ASCII text can appear in any part of an RFC, such as headings,
running text, and artwork. Non-ASCII text in person, company, and
postal names are covered later in Section 3.1.
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When the non-ASCII characters are required for correct protocol
operation and understanding, the characters' Unicode code points
should also appear in the text in the "U+NNNN" syntax, at least on
first use in the RFC. [BCP137] describes the pros and cons of
different options for identifying Unicode characters and may help
authors decide how to represent the non-ASCII characters in their
documents.
Where the use of non-ASCII characters is purely part of an example
and not otherwise required for correct protocol operation, giving the
Unicode equivalent of the non-ASCII characters is not required, but
it can improve the readability of the RFC. For example, for text
that says "The value can be followed by a monetary symbol such as ¥
or €", the RPC might require that it instead say "The value can be
followed by a monetary symbol such as ¥ (U+00A5) or € (U+20AC)".
Use of the actual non-ASCII character (such as common math symbols
like √ and ≤) is encouraged so that a reader can more easily see what
the character is. This is done without adding the "U+NNNN" syntax.
As another example, [RFC7564] says:
However, the problem is made more serious by introducing the full
range of Unicode code points into protocol strings. For example,
the characters U+13DA U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2 from
the Cherokee block look similar to the ASCII characters
"STPETER" as they might appear when presented using a "creative"
font family.
This could be replaced with:
However, the problem is made more serious by introducing the full
range of Unicode code points into protocol strings. For example,
the characters "ᏚᎢᎵᎬᎢᎬᏒ" (U+13DA U+13A2 U+13B5 U+13AC U+13A2
U+13AC U+13D2) from the Cherokee block look similar to the ASCII
characters "STPETER" as they might appear when presented using a
"creative" font family.
Code components may have different requirements for using the
"U+NNNN" syntax. The use of the "U+NNNN" syntax in code components
is recommended, except within a code component where one must follow
the rules of the programming language in which the code is being
written.
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3.1. Person and Company Identification
Person names and company names appear in several places within an RFC
(e.g., the header, Acknowledgements, and References). It is
important to note that non-ASCII characters in person and company
names are treated differently than other parts of the body of a
document. Names are often transliterated into Latin characters; non-
ASCII characters in other body text are shown with the "U+NNNN"
syntax after the character.
When a script outside the ASCII character set is used for an
individual name, an author-provided, ASCII-only transliteration can
appear immediately after the non-ASCII characters, surrounded by
parentheses. The RPC decides on a case-by-case basis whether to
include the ASCII-only transliteration.
Names of authors appear at the top of RFCs and in the References
section with a first initial (if available) and family name. For
example, Qin Wu's name might appear as "吴钦 (Q. Wu)". As another
example, Patrik Fältström's name might appear as "P. Fältström (P.
Faltstrom)", but the version with non-ASCII Latin characters also
might be left just as "P. Fältström".
In the Acknowledgements section, the person's full name is spelled
out in full without the first initial, such as "The following people
contributed to this document: 吴钦 (Qin Wu), ...".
Postal addresses may be used without additional Unicode character
identification.
If an author's email address includes non-ASCII characters and is a
valid email address at the time of publication, it may be given
without additional Unicode character identification.
3.2. Keywords and Citation Tags
Keywords (as tagged with the <keyword> element in XML) may contain
non-ASCII characters. Because the language of the RFC Series is
English, the keywords for an RFC are likely to be mostly in English
as well. Non-ASCII keywords can have parallel ASCII equivalents in
order to make searching more effective.
Citation tags (as defined in the anchor attributes of <reference>
elements) may contain non-ASCII characters if doing so make the
citation tag more useful to the reader. The RPC should prevent the
use of characters in citation tags that make RFCs difficult to read,
such as characters with right-to-left orientation.
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3.3. Non-breaking Spaces and Hyphens
Non-breaking space characters (U+00A0) and non-breaking hyphen
characters (U+2011) make searching for words and phrases in published
RFC more difficult. Therefore they should be used sparingly in RFCs.
4. XML Markup
[[ This section needs revision after community discussion ]]
As described above, use of non-ASCII characters in areas such as
email, company name, address, and name is allowed. In order to make
it easier for code to identify the appropriate ASCII alternatives,
authors must include an "ascii" attribute to their XML markup when an
ASCII alternative is required. See [RFC7991] for more detail on how
to tag ASCII alternatives.
5. Internationalization Considerations
The ability to use non-ASCII characters in RFCs in a clear and
consistent manner improves the ability to describe internationalized
protocols and recognizes the diversity of authors. However, the goal
of readability overrides the use of non-ASCII characters within the
text.
6. Security Considerations
Valid Unicode that matches the expected text must be verified in
order to preserve expected behavior and protocol information.
7. References
7.1. Normative References
[BCP137] Klensin, J., "ASCII Escaping of Unicode Characters",
BCP 137, RFC 5137, February 2008.
<https://www.rfc-editor.org/info/bcp137>
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016,
<https://www.rfc-editor.org/rfc/rfc7991>.
[RFC7997] Flanagan, H., Ed., "The Use of Non-ASCII Characters in
RFCs", RFC 7997, DOI 10.17487/RFC7997, December 2016,
<https://www.rfc-editor.org/rfc/rfc7997>.
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[RFC9280] Saint-Andre, P., Ed., "RFC Editor Model (Version 3)",
RFC 9280, DOI 10.17487/RFC9280, June 2022,
<https://www.rfc-editor.org/rfc/rfc9280>.
[UnicodeCurrent]
The Unicode Consortium, "The Unicode Standard", 2023,
<http://www.unicode.org/versions/latest/>.
7.2. Informative References
[RFC20] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/rfc/rfc20>.
[RFC7322] Flanagan, H. and S. Ginoza, "RFC Style Guide", RFC 7322,
DOI 10.17487/RFC7322, September 2014,
<https://www.rfc-editor.org/rfc/rfc7322>.
[RFC7564] Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation, Enforcement, and Comparison of
Internationalized Strings in Application Protocols",
RFC 7564, DOI 10.17487/RFC7564, May 2015,
<https://www.rfc-editor.org/rfc/rfc7564>.
[UnicodeNorm]
The Unicode Consortium, "Unicode Standard Annex", 2023,
<http://www.unicode.org/reports/tr15/>.
Appendix A. Acknowledgements
The acknowledgements from [RFC7997] are to the members of the IAB
i18n program, to the RFC Format Design Team: Nevil Brownlee, Tony
Hansen, Joe Hildebrand, Paul Hoffman, Ted Lemon, Julian Reschke, Adam
Roach, Alice Russo, Robert Sparks, and Dave Thaler.
This current document was greatly helped by contributions from the
RFC Series Working Group (RSWG), including from Brian Carpenter,
Carsten Bormann, Eliot Lear, John Levine, and Martin Thomson.
Authors' Addresses
Paul Hoffman
ICANN
Email: paul.hoffman@icann.org
Heather Flanagan
Spherical Cow Consulting
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Email: hlf@sphericalcowconsulting.com
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