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<rfc category="info" docName="draft-flanagan-nonascii-05" ipr="trust200902">
<front>
 <title abbrev="non-ASCII in RFCs">The Use of Non-ASCII Characters in RFCs</title>

 <author fullname="Heather Flanagan" initials="H." role="editor"
            surname="Flanagan">
    <organization>RFC Editor</organization>
    <address>
      <postal>
        <street></street>
        <city></city>
        <region></region>
        <code></code>
        <country></country>
      </postal>
      <phone></phone>
      <email>rse@rfc-editor.org</email>
      <uri>http://orcid.org/0000-0002-2647-2220</uri>
   </address>
 </author>

 <date month="August" year="2015" day="19"/>

 <area>General</area>
 <workgroup>Internet Engineering Task Force</workgroup>
 <keyword>RFC Series, UTF-8, ASCII, format, non-ASCII</keyword>

 <abstract>
   <t>
In order to support the internationalization of protocols and a more
diverse Internet community, the RFC Series must evolve to allow for 
the use of non-ASCII characters in RFCs.  While English remains the 
required language of the Series, the encoding of future RFCs will
be in UTF-8, allowing for a broader range of characters than typically
used in the English language.  This document describes the RFC Editor 
requirements and guidance regarding the use of non-ASCII characters in RFCs.
   </t>
   <t>
This document updates RFC 7322.
   </t>
 </abstract>
</front>


<middle>

<section title="Introduction">
<t>
For much of the history of the RFC Series, the character encoding used
for RFCs has been <xref target="ANSI.X3-4.1986">ASCII</xref>.  
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.
</t>
<t>
There are limits to ASCII, however, that hinder its continued use as the
exclusive character encoding for the Series.  The increasing need for 
easily readable, internationalized content suggests it is time to allow 
non-ASCII characters in RFCs where necessary.  To support this move away 
from ASCII, RFCs will switch to supporting UTF-8 as the default character 
encoding and allow support for a broad range of Unicode character support. 
<xref target="UnicodeCurrent"/>  Note that the RFC Editor may reject any 
codepoint that does not render adequately in enough formats or on in enough 
rendering engines using the current tooling.
</t>
<t>
Given the continuing goal of maximum readability across platforms, the
use of non-ASCII characters should be limited in a document to only where 
necessary within the text.  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.
</t>
<t>
This document updates the <xref target="RFC7322">RFC Style Guide</xref>.
</t>
<t>The details described in this document are expected to change based on experience gained in implementing the RFC production center's toolset. Revised documents will be published capturing those changes as the toolset is completed. Other implementers must not expect those changes to remain backwards-compatible with the details described this document.</t>


</section>

<section title="Basic requirements">
<t>
Two fundamental requirements inform the guidance and examples provided
in this document.  They are:
</t>
<t><list style="symbols">
  <t>Searches against RFC indexes and database tables need to return
expected results and support appropriate Unicode string matching
behaviors; </t>

  <t>RFCs must be able to display correctly across a wide range of
readers and browsers.  People whose system does 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.</t>
</list>
</t>
</section>

<section title="Rules for the use of non-ASCII characters">
<t>
This section describes the guidelines for the use of non-ASCII characters 
in the header, body, and reference sections of an RFC.  If the RFC Editor 
identifies areas where the use of non-ASCII characters negatively impacts 
the readability of the text, they will request alternate text.
</t>
<t>
The RFC Editor may, in cases of entire words represented in non-ASCII
characters, ask for a set of reviewers to verify the meaning, spelling, 
characters, and grammar of the text.
</t>

<section title="General usage throughout a document">
<t>
Where the use of non-ASCII characters is purely as part of an example
and not otherwise required for correct protocol operation, escaping 
the non-ASCII character is not required.  Note, however, that as the 
language of the RFC Series is English, the use of non-ASCII characters 
is based on the spelling of words commonly used in the English language 
following the guidance in the <xref target="MerrWeb">Merriam-Webster 
dictionary</xref>. 
</t>
<t>
The RFC Editor will use the primary spelling listed in that dictionary
by default.
</t>
<t>Example of non-ASCII characters that do not require escaping
<xref target="RFC4475"/>:

<figure>
<artwork><![CDATA[
This particular response contains unreserved and non-ascii
UTF-8 characters.
This response is well formed.  A parser must accept this message.
Message Details : unreason
SIP/2.0 200 = 2**3 * 5**2 но сто девяносто девять - простое
Via: SIP/2.0/UDP 192.0.2.198;branch=z9hG4bK1324923
Call-ID: unreason.1234ksdfak3j2erwedfsASdf
CSeq: 35 INVITE
From: sip:user@example.com;tag=11141343
To: sip:user@example.edu;tag=2229 Content-Length: 154
Content-Type: application/sdp
]]></artwork>
</figure>
</t>
</section>

<section title="Authors, Contributors, and Acknowledgments">
<t>
Person names may appear in several places within an RFC.  In all cases,
valid Unicode is required.  For names that include non-ASCII characters, 
an author-provided, ASCII-only identifier is required to assist in search 
and indexing of the document.
</t>

<t> Example for the header:</t>

<figure>
<artwork><![CDATA[
Network Working Group                                        L. Daigle
Request for Comments: 2611                    Thinking Cat Enterprises
BCP: 33                                                   D. van Gulik
Category: Best Current Practice                    ISIS/CEO, JRC Ispra
                                                           R. Iannella
                                                          DSTC Pty Ltd
                                           P. Fältström (P. Faltstrom)
                                                         Tele2/Swipnet
                                                             June 1999
]]></artwork>
</figure>


<t>
Example for the Acknowledgements:
</t>
<t>
OLD:
The following people contributed significant text to early versions of
this draft: Patrik Faltstrom, William Chan, and Fred Baker.
</t>
<t>
PROPOSED/NEW:
The following people contributed significant text to early versions of
this draft: Patrik Fältström (Patrik Faltstrom), 陈智昌 (William Chan),
and Fred Baker.
</t>
</section>

<section title="Company Names">
<t>
Company names may appear in several places within an RFC.  The rules for
company names follow similar guidance to that of person names.  Valid
Unicode is required.  For company names that include non-ASCII 
characters, an ASCII-only identifier is required to assist in search and 
indexing of the document.
</t>
</section>

<section title="Body of the document">
<t>
When the mention of non-ASCII characters is required for correct
protocol operation and understanding, the characters' Unicode character
name or code point MUST be included in the text.
</t>

<t><list style="symbols">
  <t>Non-ASCII characters will require identifying the Unicode code
point.</t>

  <t>Use of the actual UTF-8 character (e.g., Δ) is encouraged so that
a reader can more easily see what the character is, if their device can
render the text.</t>

  <t>The use of the Unicode character names like "INCREMENT" in
addition to the use of Unicode code points is also encouraged.  When
used, Unicode character names should be in all capital letters.</t>
</list>
</t>

<t>Examples:</t>
<t>OLD <xref target="RFC7564"/>: </t>

<figure>
<artwork><![CDATA[
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.
]]></artwork>
</figure>

<t>NEW/ALLOWED:</t>

<figure>
<artwork><![CDATA[
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 
(ᏚᎢᎵᎬᎢᎬᏒ) from the Cherokee block look similar to the ASCII 
characters "STPETER" as they might appear when presented using a 
"creative" font family.
]]></artwork>
</figure>

<t>ALSO ACCEPTABLE:</t>

<figure>
<artwork><![CDATA[
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.
]]></artwork>
</figure>

<t>Example of proper identification of Unicode
characters in an RFC:</t>
<t>Acceptable:</t>
<t><list style="symbols">
<t>Temperature changes in the Temperature Control Protocol are indicated
by the U+2206 character.</t>
</list>
</t>

<t> Preferred: </t>

<t><list style="numbers">
  <t>Temperature changes in the Temperature Control Protocol are
indicated by the U+2206 character ("Δ").</t>

  <t>Temperature changes in the Temperature Control Protocol are
indicated by the U+2206 character (INCREMENT).</t>

  <t>Temperature changes in the Temperature Control Protocol are
indicated by the U+2206 character ("Δ", INCREMENT).</t>

  <t>Temperature changes in the Temperature Control Protocol are
indicated by the U+2206 character (INCREMENT, "Δ").</t>

  <t>Temperature changes in the Temperature Control Protocol are
indicated by the [Delta] character "Δ" (U+2206).</t>

  <t>Temperature changes in the Temperature Control Protocol are
indicated by the character "Δ" (INCREMENT, U+2206).</t>
</list>
</t>

<t>
Which option of (1), (2), (3), (4), (5), or (6) is preferred may depend
on context and the specific character(s) in question.  All are acceptable 
within an RFC.  BCP 137, "ASCII Escaping of Unicode Character" describes 
the pros and cons of different options for identifying Unicode characters 
in an ASCII document <xref target="RFC5137">BCP137</xref>.
</t>
</section>

<section title="Tables">
<t>
Tables follow the same rules for identifiers and characters as in
"Section 3.4. Body of the document".  If it is sensible (i.e., more
understandable for a reader) for a given document to have two tables -- 
one including the identifiers and non-ASCII characters and a second with 
just the non-ASCII characters -- that will be allowed on a case-by-case 
basis.
</t>
<t>
Original text from "Preparation, Enforcement, and Comparison of Internationalized Strings Representing Usernames and Passwords" <xref target="RFC7613"/>.
</t>
      <figure>
        <preamble>Table 3: A sample of legal passwords</preamble>
        <artwork><![CDATA[
+------------------------------------+------------------------------+
| # | Password                       | Notes                        |
+------------------------------------+------------------------------+
| 12| <correct horse battery staple> | ASCII space is allowed       |
+------------------------------------+------------------------------+
| 13| <Correct Horse Battery Staple> | Different from example 12    |
+------------------------------------+------------------------------+
| 14| <&#x3C0;&#xDF;&#xE5;>          | Non-ASCII letters are OK     |
|   |                                | (e.g., GREEK SMALL LETTER    |
|   |                                | PI, U+03C0)                  |
+------------------------------------+------------------------------+
| 15| <Jack of &#x2666;s>            | Symbols are OK (e.g., BLACK  |
|   |                                | DIAMOND SUIT, U+2666)        |
+------------------------------------+------------------------------+
| 16| <foo&#x1680;bar>               | OGHAM SPACE MARK, U+1680, is |
|   |                                | mapped to U+0020 and thus    |
|   |                                | the full string is mapped to |
|   |                                | <foo bar>                    |
+------------------------------------+------------------------------+
        ]]></artwork>
      </figure>
<t>Preferred text:</t>
      <figure>
        <preamble>Table 3: A sample of legal passwords</preamble>
        <artwork><![CDATA[
+------------------------------------+------------------------------+
| # | Password                       | Notes                        |
+------------------------------------+------------------------------+
| 12| <correct horse battery staple> | ASCII space is allowed       |
+------------------------------------+------------------------------+
| 13| <Correct Horse Battery Staple> | Different from example 12    |
+------------------------------------+------------------------------+
| 14| <πß๗>                          | Non-ASCII letters are OK     |
|   |                                | (e.g., GREEK SMALL LETTER    |
|   |                                | PI, U+03C0; LATIN SMALL      |
|   |                                | LETTER SHARP S, U+00DF; THAI |
|   |                                | DIGIT SEVEN, U+0E57)         |
+------------------------------------+------------------------------+
| 15| <Jack of ♦s>                   | Symbols are OK (e.g., BLACK  |
|   |                                | DIAMOND SUIT, U+2666)        |
+------------------------------------+------------------------------+
| 16| <foo bar>                      | OGHAM SPACE MARK, U+1680, is |
|   |                                | mapped to U+0020 and thus    |
|   |                                | the full string is mapped to |
|   |                                | <foo bar>                    |
+------------------------------------+------------------------------+
        ]]></artwork>
      </figure>
</section>

<section title="Code components">
<t>
The RFC Editor encourages the use of the U+ notation except within a
code component where you must follow the rules of the programming
language in which you are writing the code.
</t>
</section>

<section title="Bibliographic text">
<t>
The reference entry must be in English; whatever subfields are present
must be available in ASCII-encoded characters.  As long as good sense is
used, the reference entry may also include non-ASCII characters at the
author's discretion and as provided by the author.  The RFC Editor may
request a review of the non-ASCII reference entry.

This applies to both normative and informative references.
</t>

<t>Example:</t>

<figure>
<artwork><![CDATA[
[GOST3410] "Information technology. Cryptographic data security. 
           Signature and verification processes of [electronic]
           digital signature.", GOST R 34.10-2001, Gosudarstvennyi 
           Standard of Russian Federation, Government Committee of 
           Russia for Standards, 2001. (In Russian)

Allowable addition to the above citation:
           "Информационная технология. Криптографическая защита
           информации. Процессы формирования и проверки
           электронной цифровой подписи", GOST R 34.10-2001,
           Государственный стандарт Российской Федерации, 2001.
]]></artwork>
</figure>
</section>

<section title="Keywords and Citation Tags">
<t>
Keywords and citation tags must be ASCII only.
</t>
</section>

<section title="Address Information">
<t>
The purpose of providing address information, either postal or e-mail,
is to assist readers of an RFC to contact the author or authors.  Authors 
may include the official postal address as recognized by their company or 
local postal service without additional non-ASCII character escapes.  If 
the email address includes non-ASCII characters and is a valid email 
address at the time of publication, non-ASCII character escapes are not
required.
</t>
</section>
</section>

<section title="Normalization Forms">
<t>
Authors should not expect normalization forms to be preserved. If a
particular normalization form is expected, note that in the text of the
RFC.
</t>
</section>

<section title="XML Markup">
<t>As described above, use of non-ASCII characters in areas such as
email, company name, addresses, 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.  See 
<xref target="I-D.hoffman-xml2rfc"/> for more detail.
</t>
</section>


<section title="IANA Considerations">
<t>
This document makes no request of IANA.
</t>
<t>
Note to RFC Editor: this section may be removed on publication as an
RFC.
</t>
</section>

<section title="Internationalization Considerations">
<t>
The ability to use non-ASCII characters in RFCs in a clear and consistent 
manner will improve the ability to describe internationalized protocols 
and will recognize the diversity of authors. However, the goal of readability
will override the use of non-ASCII characters within the text.
</t>
</section>

<section title="Security Considerations">
<t>
Valid Unicode that matches the expected text must be verified in order
to preserve expected behavior and protocol information.
</t>
</section>

<section title="Change log - to be removed by the RFC Editor">
<section title="-04 to -05">
<t>Keywords: expanded section to include citation tags.</t>
<t>Internationalization considerations: reiterated that the use of non-ASCII 
characters is not automatically guaranteed.</t>
</section>
<section title="-04 to -05">
<t>Introduction: added statement regarding document subject to change.</t>
<t>Tables: added example.</t>
<t>Code: removed placeholder for example.</t>
</section>
<section title="-02 to -04">
<t>Introduction and Abstract: change to be clearer about what/why non-ASCII
   characters are being allowed.</t>
<t>XML Markup: section added.</t>
</section>
</section>

</middle>

<back>

<references title="References">

&ANSI.X3-4.1986;
&STD64;
&RFC4475;
&RFC5137;
&RFC6949;
&RFC7322;
&RFC7564;
&RFC7613;
&I-D.hoffman-xml2rfc;

<reference anchor="MerrWeb">
  <front>
    <title>Merriam-Webster's Collegiate Dictionary, 11th Edition</title>
    <author>
      <organization>Merriam-Webster,Inc.</organization>
    </author>
    <date year="2009" />
  </front>
</reference>
<reference anchor="UnicodeCurrent" target="http://www.unicode.org/versions/latest/">
  <front>
    <title>The Unicode Standard</title>
    <author>
      <organization>The Unicode Consortium</organization>
    </author>
    <date year="2014-present"/>
  </front>
</reference>
</references>


<section title="Acknowledgements">
<t>
With many thanks to the members of the IAB i18n program and the RFC Format 
Design Team.
</t>
</section>
</back>

</rfc>
