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RFC2278 - IANA Charset Registration Procedures

王朝other·作者佚名  2008-05-31
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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].

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 RFC2130.

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].

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 RFC2045. 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.

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.

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 RFC2045 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

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 RFCby 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:

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.

[RFC-1759]

Smith, R., Wright, F., Hastings, T., Zilles, S., and J.

Gyllenskog, "Printer MIB", RFC1759, March 1995.

[RFC-2045]

Freed, N., and N. Borenstein, "Multipurpose Internet Mail

Extensions (MIME) Part One: Format of Internet Message Bodies",

RFC2045, November 1996.

[RFC-2046]

Freed, N., and N. Borenstein, "Multipurpose Internet Mail

Extensions (MIME) Part Two: Media Types", RFC2046, November

1996.

[RFC-2047]

Moore, K., "Multipurpose Internet Mail Extensions (MIME) Part

Three: Representation of Non-Ascii Text in Internet Message

Headers", RFC2047, November 1996.

[RFC-2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement

Levels", BCP 14, RFC2119, 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", RFC2130, 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.

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

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.

 
 
 
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