Network Working Group P. Hoffman
Internet-Draft ICANN
Obsoletes: 7997 (if approved) 2 March 2023
Updates: 7322 (if approved)
Intended status: Informational
Expires: 3 September 2023
The Use of Non-ASCII Characters in RFCs
draft-hoffman-rfc7997bis-01
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 Production Center regarding the use of non-ASCII characters
in RFCs.
This document updates RFC 7997 to 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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 September 2023.
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Copyright Notice
Copyright (c) 2023 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/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Acknowledgements . . . . . . . . . . . . . . . . . . . . 3
1.2. Changes from RFC 7997 . . . . . . . . . . . . . . . . . . 3
2. Basic Requirements . . . . . . . . . . . . . . . . . . . . . 4
3. Use of Non-ASCII Characters . . . . . . . . . . . . . . . . . 4
3.1. General Usage throughout a Document . . . . . . . . . . . 5
3.2. Person and Company Names . . . . . . . . . . . . . . . . 5
3.3. Body of the Document . . . . . . . . . . . . . . . . . . 6
3.4. Keywords and Citation Tags . . . . . . . . . . . . . . . 7
3.5. Authors' Address Information . . . . . . . . . . . . . . 7
4. XML Markup . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Internationalization Considerations . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 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-
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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].
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. Acknowledgements
RFC 7997 was written by Heather Flanagan, who was the RFC Series
Editor (RSE) at the time of its publication. Getting the IETF
community to agree to the changes embodied in RFC 7997 was a
difficult task, and it is likely that this current document would be
much more difficult to write had RFC 7997 not been worked out first.
The acknowledgements from RFC 7997 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.
1.2. Changes from RFC 7997
The following is an overview of the changes in this document from RFC
7997:
* Added the role of the RFC stream approving bodies and the RFC
Production Center (RPC) as described in [RFC9280] throughout the
document. In short, all responsibilities that were held by the
RFC Editor in RFC 7997 are handled by the RPC. If the RPC has
questions about the content of RFCs, the RPC can ask the RFC
stream approving bodies for input.
* Removed requirements of marking non-ASCII characters with XML
markup. Clarified that names with non-Latin characters should
have Latin transliterations.
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* 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.
* Added the suggestion that non-ASCII characters appear in NFC.
* Language about the future was changed to the past tense to
indicate that RFC 7997 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 RFC 7997.
2. Basic Requirements
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 Characters
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.
In general, using the "U+NNNN" syntax from [BCP137] is the suggested
way to show Unicode code points as alternate text.
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Characters in an RFC will generally appear in Normalization Form C
(NFC), which is described in [UnicodeNorm] as "canonical
decomposition, followed by canonical composition". If the author
expects a different normalization form to appear in the published
RFC, that must be noted in the text of the RFC.
3.1. General Usage throughout a Document
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)".
Reference entries (bibliographic text) and tables follow the rules
given in this section.
[ The text from Section 3.3 could be moved here and some duplication
removed. ]
[ The example for this section from RFC 7997 has been removed. It
was, in fact, not an example of general usage but instead a protocol
example. ]
3.2. Person and Company Names
[ RFC 7997 was inconsistent in its rules and examples of when names
with non-ASCII characters should be spelled out using all-ASCII
transliteration. This section is significantly updated to clarify
how names with non-ASCII characters should appear in RFCs. ]
Person names and company names appear in several places within an RFC
(e.g., the header, Acknowledgements, and References).
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 "å´é’¦ (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".
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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: å´é’¦ (Qin Wu), ...".
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 transliterated into Latin characters; non-
ASCII characters in other body text are shown with U+ encoding after
the character.
3.3. Body of the Document
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 from [BCP137],
at least on first use in the RFC.
Use of the actual non-ASCII character (such as common math symbols
like √) is encouraged so that a reader can more easily see what the
character is. This is done without adding the "U+NNNN" syntax.
[ Removed "The use of the Unicode character names like "INCREMENT" in
addition to the use of Unicode code points is also encouraged." This
text was, in fact, wrong in 7997 because the character name did not
match the example. ]
For 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 "ášáŽ¢áŽµáŽ¬áŽ¢áŽ¬á’" (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.
[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.
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Code components may have different requirements for using the U+
notation. 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.
3.4. Keywords and Citation Tags
Keywords (as tagged with the <keyword> element in XML) and citation
tags (as defined in the anchor attributes of <reference> elements)
must contain only ASCII characters.
[ Does the WG still want this restriction? ]
3.5. Authors' Address Information
The purpose of providing authors' address information, either postal
or email, is to assist readers of an RFC in contacting the author or
authors. Authors may include the official postal address as
recognized by their company or local postal service 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.
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.
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7. References
7.1. Normative References
[BCP137] Klensin, J., "ASCII Escaping of Unicode Characters",
BCP 137, RFC 5137, February 2008.
[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>.
[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/>.
Author's Address
Paul Hoffman
ICANN
Email: paul.hoffman@icann.org
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