One document matched: draft-hoffman-utf8-rfcs-03.txt
Differences from draft-hoffman-utf8-rfcs-02.txt
Network Working Group P. Hoffman
Internet-Draft VPN Consortium
Updates: 2223 (if approved) T. Bray
Intended status: Informational Sun Microsystems
Expires: April 5, 2009 October 2, 2008
Using non-ASCII Characters in RFCs
draft-hoffman-utf8-rfcs-03.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document specifies a change to the IETF process in which
Internet Drafts and RFCs are allowed to contain non-ASCII characters.
The proposed change is to change the encoding of Internet Drafts and
RFCs to UTF-8.
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1. Introduction
The purpose of this document is to specify a way for the IETF to use
non-ASCII characters in Internet Drafts and RFCs.
Various guideline documents in the IETF, notably [RFC2223], specify
that RFCs must use only the US-ASCII character set. This restriction
has historically caused problems, notably:
o Names and addresses of authors of IETF documents are misspelled
o Names and document titles in references are misspelled
o Protocol examples that include non-ASCII characters cannot be
included straightforwardly
The first two issues cause real problems for people searching for
RFCs for particular authors or references that contain non-ASCII
characters. For many languages that use Latin characters outside the
ASCII range, there are not absolute mappings between those non-ASCII
characters and ASCII equivalents. A common example is that "a-with-
umlaut" (U+00E4) may be mapped to "a" or to "ae"; many other mapping
difficulties exist.
The third issue reduces the effectiveness of IETF specifications;
Implementors of protocols which carry textual payloads often
experience difficulty in achieving interoperability related to the
use of character sets from around the world. Specifications which
can provide concrete examples of such protocol scenarios will be of
significant benefit to these implementors.
Now that UTF-8 [RFC3629] is nearly universally available in text-
editing and display systems, the IETF can eliminate these problems by
allowing RFCs to use UTF-8.
This document uses example characters as specified in [RFC5137]. Had
the recommendations from this document already been implemented, this
alternate representation would, of course, not be necessary.
It is important to note that this document does not use RFC 2119
language (MUST, SHOULD, and so on). Instead, it lists practices that
the IETF should consider. If the ideas in this document are adopted,
the final list of rules for using UTF-8 in Internet Drafts and RFCs
would be published by the IAOC. The authors are open to changing
this and using 2119-style language if the community prefers it.
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2. Use of UTF-8 in Internet Drafts and RFCs
Upon publication of this document as an RFC, all existing RFCs and
Internet Drafts will be considered to be encoded in UTF-8. The RFC
Editor needs to change their processes to publish documents that are
valid UTF-8.
Similarly, upon acceptance of this document by the IETF, the IAOC
should direct the IETF Secretariat to have all Internet Drafts
encoded in UTF-8. The Secretariat needs to change their processes to
publish documents that are valid UTF-8.
2.1. Limits On the Locations In Which Non-ASCII Text May Be Used
It is suggested that the IETF Secretariat and RFC Editor limit non-
ASCII characters to the following:
o Names and addresses of authors, used at the top of RFCs and in
Author Contact sections
o Names and document titles used in References sections
o Quotations from non-English languages
o Protocol examples that show non-ASCII characters, for example in
Internationalized Domain Names (IDNs), Internationalized Resource
Identifiers (IRIs), and internationalized email addresses.
2.2. Allowable Character Repertoire
UTF-8 is an encoding of the Unicode Character Set and can be used to
any of its numeric codepoints, from 0 to 0x10FFFF inclusive.
Specifications encoded in UTF-8 should not contain the encodings of
certain Unicode codepoints. The codepoint ranges given in this
section are inclusive:
o The "ASCII control characters" in the ranges U+0000 to U+0008, and
U+000B to U+001F. These lack either visual representations,
interoperable semantics, or both.
o The Surrogate-block range U+D800 to U+DFFF. These codepoints do
not identify characters, but exist to support the UTF-16 encoding.
o The ZERO WIDTH NO-BREAK SPACE U+FEFF and its mirror image U+FFFE.
o The Private-Use-Area ranges, U+E000 to U+F8FF, U+F0000 to U+FFFFD,
and U+100000 to U+10FFFD.
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Specifications encoded in UTF-8 should not contain the encodings of
Unicode codepoints which are "Compatibility Characters", that is,
those whose properties include a compatibility decomposition. Note
that such characters occur rarely and detecting them requires run-
time access to the Unicode character database, which may not be
practical in some situations.
2.3. Normalization
Due to the way that Unicode uses combining characters, there are
sometimes multiple codepoint sequences that denote what, to a human,
is the same character. For example, the character "lowercase-a-with-
accent" can be spelled in two ways: as a single character (U+00E1) or
as two characters (U+0061 followed by U+0301). This can present
problems in searching and rendering.
The process of standardizing on one of these possibilities is
referred to as "normalization" and several "normalization forms" are
defined by the Unicode Consortium. All UTF-8 text appearing in RFCs
(but not necessarily Internet Drafts) ought to be normalized using
Normalization Form C.
2.4. Author and Employer Names
Authors can choose how to spell their names and the names of their
employers in the various parts of Internet Drafts they are writing.
The spelling at the top of the first page of the document needs to
match the spelling in the "Authors' Addresses" section near the end
of the document, but the latter can have alternate spellings to help
those searching documents by name. Postal information listed in the
"Authors' Addresses" section can also use non-ASCII.
For example, assume that an author whose name is <U+6653><U+4E1C>
F<U+00E4>ltstr<U+00F6>m has a preferred all-ASCII spelling of
Xiaodong Faltstrom. Two expected allowed methods for spelling his
name would be:
Network Working Group X. Faltstrom
Internet-Draft ExampleCo
. . .
Author's Address
Xiaodong Faltstrom (<U+6653><U+4E1C> F<U+00E4>ltstr<U+00F6>m)
ExampleCo
Email: xiaodong.faltstrom@example.com
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Network Working Group X. F<U+00E4>ltstr<U+00F6>m
Internet-Draft ExampleCo
. . .
Author's Address
<U+6653><U+4E1C> F<U+00E4>ltstr<U+00F6>m (Xiaodong Faltstrom)
ExampleCo
Email: xiaodong.faltstrom@example.com
3. Security Considerations
A display program that expects only US-ASCII input may fail when it
encounters octets outside the US-ASCII range of values. Such a
failure may become a security issue. For example, the program may
display incorrect results for the input. More seriously, the program
may have an internal error that causes it to fail in a security-
compromising fashion. Note that such a program is vulnerable to many
attacks other than just showing IETF documents.
Someone could insert a UTF-8 host name in an RFC that has visually
confusing characters. Another person could copy that host name out
of the RFC and have it resolve to an unintended DNS name. This
scenario seems quite far-fetched, given that tracking the RFC back to
the author is trivial.
4. IAOC considerations
If this document is adopted by the IETF, it will be up to the IAOC to
have the IETF Secretariat and the RFC Editor implement it. The IAOC
needs to consider all of the suggested rules in this document, both
the positive ones (such as allowing additional characters in some
parts of Internet Drafts and RFCs) and the negative ones (such as
disallowing particular characters from being used). The IAOC might
want to publish proposed instructions to he IETF Secretariat and the
RFC Editor and ask for community input on the specific instructions.
5. Informative References
[RFC2223] Postel, J. and J. Reynolds, "Instructions to RFC Authors",
RFC 2223, October 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
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[RFC5137] Klensin, J., "ASCII Escaping of Unicode Characters",
BCP 137, RFC 5137, February 2008.
Appendix A. Arguments Against Changing to UTF-8
Over more than a decade, the question of changing the encoding of
RFCs to UTF-8 has come up repeatedly. Although many people wanted
the change, various people had different reasons why they felt it was
a bad idea. This appendix is a summary of those arguments and an
explanation of why they are no longer as critical as they were long
ago.
A.1. Difficulty in Displaying
Some text display systems only know how to display US-ASCII.
Displaying an RFC that uses non-ASCII characters encoded in UTF-8
will cause those characters to be unreadable.
There are, of course, still such display systems, and there always
will be. However, the number is dwindling as more software is
improved to display non-ASCII characters and, in particular, to read
UTF-8 as an encoding. Of the systems that can only render US-ASCII,
only a small subset drop non-ASCII characters: the others show an
incorrect character in its place. Thus, the person using such a
system can often see that there is a problem, and can possibly choose
to get better display software.
A.2. Difficulty in Printing
Some printers can only print a limited set of characters due to the
fact that they are character-oriented, not graphical. Such printers
inherently cannot print characters they do not understand. Almost
all such printers print the ASCII characters just fine.
There are, of course, still such printers, and there always will be.
However, the number is dwindling as older printers are replaced with
ones that can print graphics so that now-common text features like
boldface and italics can be printed.
A.3. Insufficient Fonts
Almost no display system that can display text that is encoded with
UTF-8 can display every character in the Unicode repertoire. Thus,
some non-ASCII characters that are included in RFCs will not display
properly.
Virtually every system that can display Unicode knows how to
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substitute a replacement character for ones that cannot be displayed.
In fact, most such systems have glyphs for rendering unknown
characters and different glyphs for rendering known characters for
which the system has no font.
A.4. Inability to Search for Non-ASCII Characers
If authors start using non-ASCII characters in their names and/or
addresses, people who know the characters but are unfamiliar with the
user interface on their computers may not be able to enter those
characters in the search criteria. For example, some people do not
know how to enter "u-with-umlaut" in their operating system, even
though the operating system allows such input.
This is a valid concern, but one that is orthogonal to whether or not
RFCs should use these characters. The alternative (never go to
UTF-8) simply shifts the problem to forcing the user to guess which
ASCII-only spelling to use when searching.
Appendix B. Changes from -02 to -03
Changed the example name from Frank H<U+00F6>rst to <U+6653><U+4E1C>
F<U+00E4>ltstr<U+00F6>m.
In 2.1, changed "It is suggested that the RFC Editor limit..." to "It
is suggested that the IETF Secretariat and RFC Editor limit..."
Made 2.4 match 2.1 by saying that postal addresses can be in UTF-8 as
well.
Authors' Addresses
Paul Hoffman
VPN Consortium
Email: paul.hoffman@vpnc.org
Tim Bray
Sun Microsystems
Email: tbray@textuality.com
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