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rfc:rfc2278

Network Working Group N. Freed Request for Comments: 2278 Innosoft BCP: 19 J. Postel Category: Best Current Practice ISI

                                                          January 1998
                            IANA Charset
                      Registration Procedures

Status of this Memo

 This document specifies an Internet Best Current Practices for the
 Internet Community, and requests discussion and suggestions for
 improvements.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1998).  All Rights Reserved.

1. Abstract

 MIME [RFC-2045, RFC-2046, RFC-2047, RFC-2184] and various other
 modern Internet protocols are capable of using many different
 charsets. This in turn means that the ability to label different
 charsets is essential. This registration procedure exists solely to
 associate a specific name or names with a given charset and to give
 an indication of whether or not a given charset can be used in MIME
 text objects. In particular, the general applicability and
 appropriateness of a given registered charset is a protocol issue,
 not a registration issue, and is not dealt with by this registration
 procedure.

2. Definitions and Notation

 The following sections define various terms used in this document.

2.1. Requirements Notation

 This document occasionally uses terms that appear in capital letters.
 When the terms "MUST", "SHOULD", "MUST NOT", "SHOULD NOT", and "MAY"
 appear capitalized, they are being used to indicate particular
 requirements of this specification. A discussion of the meanings of
 these terms appears in [RFC-2119].

Freed & Postel Best Current Practice [Page 1] RFC 2278 Charset Registration January 1998

2.2. Character

 A member of a set of elements used for the organisation, control, or
 representation of data.

2.3. Charset

 The term "charset" (see historical note below) is used here to refer
 to a method of converting a sequence of octets into a sequence of
 characters. This conversion may also optionally produce additional
 control information such as directionality indicators.
 Note that unconditional and unambiguous conversion in the other
 direction is not required, in that not all characters may be
 representable by a given charset and a charset may provide more than
 one sequence of octets to represent a particular sequence of
 characters.
 This definition is intended to allow charsets to be defined in a
 variety of different ways, from simple single-table mappings such as
 US-ASCII to complex table switching methods such as those that use
 ISO 2022's techniques, to be used as charsets.  However, the
 definition associated with a charset name must fully specify the
 mapping to be performed.  In particular, use of external profiling
 information to determine the exact mapping is not permitted.
 HISTORICAL NOTE: The term "character set" was originally used in MIME
 to describe such straightforward schemes as US-ASCII and ISO-8859-1
 which consist of a small set of characters and a simple one-to-one
 mapping from single octets to single characters. Multi-octet
 character encoding schemes and switching techniques make the
 situation much more complex. As such, the definition of this term was
 revised to emphasize both the conversion aspect of the process, and
 the term itself has been changed to "charset" to emphasize that it is
 not, after all, just a set of characters. A discussion of these
 issues as well as specification of standard terminology for use in
 the IETF appears in RFC 2130.

2.4. Coded Character Set

 A Coded Character Set (CCS) is a mapping from a set of abstract
 characters to a set of integers. Examples of coded character sets are
 ISO 10646 [ISO-10646], US-ASCII [US-ASCII], and the ISO-8859 series
 [ISO-8859].

Freed & Postel Best Current Practice [Page 2] RFC 2278 Charset Registration January 1998

2.5. Character Encoding Scheme

 A Character Encoding Scheme (CES) is a mapping from a Coded Character
 Set or several coded character sets to a set of octets. A given CES
 is typically associated with a single CCS; for example, UTF-8 applies
 only to ISO 10646.

3. Registration Requirements

 Registered charsets are expected to conform to a number of
 requirements as described below.

3.1. Required Characteristics

 Registered charsets MUST conform to the definition of a "charset"
 given above.  In addition, charsets intended for use in MIME content
 types under the "text" top-level type must conform to the
 restrictions on that type described in RFC 2045. All registered
 charsets MUST note whether or not they are suitable for use in MIME.
 All charsets which are constructed as a composition of a CCS and a
 CES MUST either include the CCS and CES they are based on in their
 registration or else cite a definition of their CCS and CES that
 appears elsewhere.
 All registered charsets MUST be specified in a stable, openly
 available specification. Registration of charsets whose
 specifications aren't stable and openly available is forbidden.

3.2. New Charsets

 This registration mechanism is not intended to be a vehicle for the
 definition of entirely new charsets. This is due to the fact that the
 registration process does NOT contain adequate review mechanisims for
 such undertakings.
 As such, only charsets defined by other processes and standards
 bodies, or specific profiles of such charsets, are eligible for
 registration.

3.3. Naming Requirements

 One or more names MUST be assigned to all registered charsets.
 Multiple names for the same charset are permitted, but if multiple
 names are assigned a single primary name for the charset MUST be
 identified. All other names are considered to be aliases for the
 primary name and use of the primary name is preferred over use of any
 of the aliases.

Freed & Postel Best Current Practice [Page 3] RFC 2278 Charset Registration January 1998

 Each assigned name MUST uniquely identify a single charset.  All
 charset names MUST be suitable for use as the value of a MIME content
 type charset parameter and hence MUST conform to MIME parameter value
 syntax. This applies even if the specific charset being registered is
 not suitable for use with the "text" media type.
 Finally, charsets being registered for use with the "text" media type
 MUST have a primary name that conforms to the more restrictive syntax
 of the charset field in MIME encoded-words [RFC-2047, RFC-2184] and
 MIME extended parameter values [RFC-2184]. A combined ABNF definition
 for such names is as follows:
 mime-charset = 1*<Any CHAR except SPACE, CTLs, and cspecials>
 cspecials    = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "
                <"> / "/" / "[" / "]" / "?" / "." / "=" / "*"
 CHAR         =  <any ASCII character>        ; (  0-177,  0.-127.)
 SPACE        =  <ASCII SP, space>            ; (     40,      32.)
 CTL          =  <any ASCII control           ; (  0- 37,  0.- 31.)
                  character and DEL>          ; (    177,     127.)

3.4. Functionality Requirement

 Charsets must function as actual charsets: Registration of things
 that are better thought of as a transfer encoding, as a media type,
 or as a collection of separate entities of another type, is not
 allowed.  For example, although HTML could theoretically be thought
 of as a charset, it is really better thought of as a media type and
 as such it cannot be registered as a charset.

3.5. Usage and Implementation Requirements

 Use of a large number of charsets in a given protocol may hamper
 interoperability. However, the use of a large number of undocumented
 and/or unlabelled charsets hampers interoperability even more.
 A charset should therefore be registered ONLY if it adds significant
 functionality that is valuable to a large community, OR if it
 documents existing practice in a large community. Note that charsets
 registered for the second reason should be explicitly marked as being
 of limited or specialized use and should only be used in Internet
 messages with prior bilateral agreement.

3.6. Publication Requirements

 Charset registrations can be published in RFCs, however, RFC
 publication is not required to register a new charset.

Freed & Postel Best Current Practice [Page 4] RFC 2278 Charset Registration January 1998

 The registration of a charset does not imply endorsement, approval,
 or recommendation by the IANA, IESG, or IETF, or even certification
 that the specification is adequate. It is expected that applicability
 statements for particular applications will be published from time to
 time that recommend implementation of, and support for, charsets that
 have proven particularly useful in those contexts.

3.7. MIBenum Requirements

 Each registered charset MUST also be assigned a unique enumerated
 integer value. These "MIBenum" values are defined by and used in the
 Printer MIB [RFC-1759].
 A MIBenum value for each charset will be assigned by IANA at the time
 of registration.

4. Registration Procedure

 The following procedure has been implemented by the IANA for review
 and approval of new charsets.  This is not a formal standards
 process, but rather an administrative procedure intended to allow
 community comment and sanity checking without excessive time delay.

4.1. Present the Charset to the Community

 Send the proposed charset registration to the "ietf-
 charsets@iana.org" mailing list.  This mailing list has been
 established for the sole purpose of reviewing proposed charset
 registrations. Proposed charsets are not formally registered and must
 not be used; the "x-" prefix specified in RFC 2045 can be used until
 registration is complete.
 The intent of the public posting is to solicit comments and feedback
 on the definition of the charset and the name chosen for it over a
 two week period.

4.2. Charset Reviewer

 When the two week period has passed and the registration proposer is
 convinced that consensus has been achieved, the registration
 application should be submitted to IANA and the charset reviewer. The
 charset reviewer, who is appointed by the IETF Applications Area
 Director(s), either approves the request for registration or rejects
 it.  Rejection may occur because of significant objections raised on
 the list or objections raised externally.  If the charset reviewer
 considers the registration sufficiently important and controversial,
 a last call for comments may be issued to the full IETF. The charset

Freed & Postel Best Current Practice [Page 5] RFC 2278 Charset Registration January 1998

 reviewer may also recommend standards track processing (before or
 after registration) when that appears appropriate and the level of
 specification of the charset is adequate.
 Decisions made by the reviewer must be posted to the ietf-charsets
 mailing list within 14 days. Decisions made by the reviewer may be
 appealed to the IESG.

4.3. IANA Registration

 Provided that the charset registration has either passed review or
 has been successfully appealed to the IESG, the IANA will register
 the charset, assign a MIBenum value, and make its registration
 available to the community.

5. Location of Registered Charset List

 Charset registrations will be posted in the anonymous FTP file
 "ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets" and all
 registered charsets will be listed in the periodically issued
 "Assigned Numbers" RFC [currently RFC-1700].  The description of the
 charset may also be published as an Informational RFC by sending it
 to "rfc-editor@isi.edu" (please follow the instructions to RFC
 authors [RFC-2223]).

6. Registration Template

 To: ietf-charsets@iana.org
 Subject: Registration of new charset
 Charset name(s):
 (All names must be suitable for use as the value of a MIME content-
 type parameter.)
 Published specification(s):
 (A specification for the charset must be openly available that
 accurately describes what is being registered. If a charset is
 defined as a composition of a CCS and a CES then these defintions
 must either be included or referenced.)
 Person & email address to contact for further information:

Freed & Postel Best Current Practice [Page 6] RFC 2278 Charset Registration January 1998

7. Security Considerations

 This registration procedure is not known to raise any sort of
 security considerations that are appreciably different from those
 already existing in the protocols that employ registered charsets.

8. References

 [ISO-2022]
      International Standard -- Information Processing -- Character
      Code Structure and Extension Techniques, ISO/IEC 2022:1994, 4th
      ed.
 [ISO-8859]
      International Standard -- Information Processing -- 8-bit
      Single-Byte Coded Graphic Character Sets
      - Part 1: Latin Alphabet No. 1, ISO 8859-1:1987, 1st ed.
      - Part 2: Latin Alphabet No. 2, ISO 8859-2:1987, 1st ed.
      - Part 3: Latin Alphabet No. 3, ISO 8859-3:1988, 1st ed.
      - Part 4: Latin Alphabet No. 4, ISO 8859-4:1988, 1st ed.
      - Part 5: Latin/Cyrillic Alphabet, ISO 8859-5:1988, 1st
      ed.
      - Part 6: Latin/Arabic Alphabet, ISO 8859-6:1987, 1st ed.
      - Part 7: Latin/Greek Alphabet, ISO 8859-7:1987, 1st ed.
      - Part 8: Latin/Hebrew Alphabet, ISO 8859-8:1988, 1st ed.
      - Part 9: Latin Alphabet No. 5, ISO/IEC 8859-9:1989, 1st
      ed.
      International Standard -- Information Technology -- 8-bit
      Single-Byte Coded Graphic Character Sets
      - Part 10: Latin Alphabet No. 6, ISO/IEC 8859-10:1992,
      1st ed.
 [ISO-10646]
      ISO/IEC 10646-1:1993(E),  "Information technology --
      Universal Multiple-Octet Coded Character Set (UCS) --
      Part 1: Architecture and Basic Multilingual Plane",
      JTC1/SC2, 1993.
 [RFC-2048]
      Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
      Mail Extensions (MIME) Part Four: Registration Procedures", RFC
      2048, November 1996.
 [RFC-1700]
      Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC
      1700, October 1994.

Freed & Postel Best Current Practice [Page 7] RFC 2278 Charset Registration January 1998

 [RFC-1759]
      Smith, R., Wright, F., Hastings, T., Zilles, S., and J.
      Gyllenskog, "Printer MIB", RFC 1759, March 1995.
 [RFC-2045]
      Freed, N., and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part One: Format of Internet Message Bodies",
      RFC 2045, November 1996.
 [RFC-2046]
      Freed, N., and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part Two: Media Types", RFC 2046, November
      1996.
 [RFC-2047]
      Moore, K., "Multipurpose Internet Mail Extensions (MIME) Part
      Three: Representation of Non-Ascii Text in Internet Message
      Headers", RFC 2047, November 1996.
 [RFC-2119]
      Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [RFC-2130]
      Weider, C., Preston, C., Simonsen, K., Alvestrand, H., Atkinson,
      R., Crispin, M., and P. Svanberg, "Report from the IAB Character
      Set Workshop", RFC 2130, April 1997.
 [RFC-2184]
      Freed, N., and K. Moore, "MIME Parameter Value and Encoded Word
      Extensions: Character Sets, Languages, and Continuations", RFC
      2184, August 1997.
 [US-ASCII]
      Coded Character Set -- 7-Bit American Standard Code for
      Information Interchange, ANSI X3.4-1986.

Freed & Postel Best Current Practice [Page 8] RFC 2278 Charset Registration January 1998

9. Authors' Addresses

 Ned Freed
 Innosoft International, Inc.
 1050 Lakes Drive
 West Covina, CA 91790
 USA
 Phone: +1 626 919 3600
 Fax:   +1 626 919 3614
 EMail: ned.freed@innosoft.com
 Jon Postel
 USC/Information Sciences Institute
 4676 Admiralty Way
 Marina del Rey, CA  90292
 USA
 Phone: +1 310 822 1511
 Fax:   +1 310 823 6714
 EMail: Postel@ISI.EDU

Freed & Postel Best Current Practice [Page 9] RFC 2278 Charset Registration January 1998

Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Freed & Postel Best Current Practice [Page 10]

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