Internet DRAFT - draft-iana-charset-reg-procedure
draft-iana-charset-reg-procedure
Network Working Group M. Mcfadden
Internet-Draft IANA
Obsoletes: 2978 (if approved) A. Melnikov, Ed.
Intended status: Best Current Practice Isode Ltd
Expires: October 26, 2015 April 24, 2015
IANA Charset Registration Procedures
draft-iana-charset-reg-procedure-01
Abstract
Multipurpose Internet Mail Extensions (MIME) (RFC-2045, RFC-2046,
RFC-2047, RFC-2231) and various other Internet protocols are capable
of using many different charsets. This in turn means that the
ability to label different charsets is essential.
This document obsoletes the IANA Charset Registration Procedures
originally defined in [RFC2978]. Specifically, this document
completely revises the registration procedures and the charset
registries. The charset registry is now divided into three parts
with separate registration procedures for each.
Note: The charset 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 to a particular application is a protocol
issue, not a registration issue, and is not dealt with by this
registration procedure.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 26, 2015.
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Copyright Notice
Copyright (c) 2015 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
(http://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Definitions and Notation . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3
1.2. Character . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Charset . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Coded Character Set . . . . . . . . . . . . . . . . . . . 4
1.5. Character Encoding Scheme . . . . . . . . . . . . . . . . 4
2. Charset Registration Requirements . . . . . . . . . . . . . . 4
2.1. Required Characteristics . . . . . . . . . . . . . . . . 4
2.2. New Charsets . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Naming Requirements . . . . . . . . . . . . . . . . . . . 5
2.4. Functionality Requirement . . . . . . . . . . . . . . . . 6
2.5. Usage and Implementation Requirements . . . . . . . . . . 6
2.6. Publication Requirements . . . . . . . . . . . . . . . . 6
2.7. MIBenum Requirements . . . . . . . . . . . . . . . . . . 6
3. The Charset Registry . . . . . . . . . . . . . . . . . . . . 7
3.1. The Recommended charset registry . . . . . . . . . . . . 7
3.2. The Widely-used Open Standard charset registry . . . . . 7
3.2.1. Submitting "Widely-used Open Standard" charset
Proposals to the IETF Community . . . . . . . . . . . 8
3.2.2. IANA Charset Registration Template . . . . . . . . . 8
3.2.3. Charset Reviewer . . . . . . . . . . . . . . . . . . 9
3.2.4. IANA Registration of "Widely-used Open Standard"
charsets . . . . . . . . . . . . . . . . . . . . . . 9
3.3. The Other charset subregistry . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4.1. Publication of Registered Charset List . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . 12
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Appendix A. Changes Since RFC 2978 . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Definitions and Notation
The following sections define terms used in this document.
1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Character
A member of a set of elements used for the organization, control, or
representation of data.
1.3. Charset
The term "charset" (referred to as a "character set" in previous
versions of this document) 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 [RFC0020] to complex table switching methods such as those
that use ISO 2022's [ISO-2022] techniques. 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
[ISO-8859] 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
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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].
1.4. Coded Character Set
A Coded Character Set (CCS) is a one-to-one mapping from a set of
abstract characters to a set of integers. Examples of coded
character sets are ISO 10646 [ISO-10646], US-ASCII [RFC0020], and the
ISO-8859 series [ISO-8859].
1.5. 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 octet sequences. A
given CES is sometimes associated with a single CCS; for example,
UTF-8 [RFC3629] applies only to ISO 10646.
2. Charset Registration Requirements
Registered charsets are expected to conform to a number of
requirements as described below.
2.1. 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 media 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
text.
All charsets which are constructed as a composition of one or more
CCS's and a CES MUST either include the CCS's and CES they are based
on in their registration or else cite a definition of their CCS's 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.
2.2. New Charsets
This registration mechanism is not intended to be a vehicle for the
design and definition of entirely new charsets. This is due to the
fact that the registration process does NOT contain adequate review
mechanisms for such undertakings.
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As such, only charsets defined by other processes and standards
bodies, or specific profiles or combinations of such charsets, are
eligible for registration.
2.3. 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 (see Section 5.1 of RFC 2045). This applies even if the
specific charset being registered is not suitable for use with the
"text" media type. All charsets MUST be assigned a name that
provides a display string for the associated "MIBenum" value defined
below. These "MIBenum" values are defined by and used in the Printer
MIB [RFC1759]. [[RFC 1759 got obsoleted by RFC 3805 and MIBEnum is
no longer there. Should we point to http://www.iana.org/assignments/
ianacharset-mib instead?]] Such names MUST begin with the letters
"cs" and MUST contain no more than 40 characters (including the "cs"
prefix) chosen from from the printable subset of US-ASCII. Only one
name beginning with "cs" may be assigned to a single charset. If no
name of this form is explicitly defined IANA will assign an alias
consisting of "cs" prepended to the primary charset name.
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 [RFC2047] [RFC2231] and
MIME extended parameter values [RFC2231]. A combined ABNF [RFC5234]
definition for such names is as follows:"
mime-charset = 1*mime-charset-chars
mime-charset-chars = ALPHA / DIGIT /
"!" / "#" / "$" / "%" / "&" /
"+" / "-" / "^" / "_" / "`" /
"{" / "}" / "~"
ALPHA = "A".."Z" ; Case insensitive ASCII Letter
DIGIT = "0".."9" ; Numeric digit
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2.4. Functionality Requirement
Charsets MUST function as actual charsets: Registration of things
that are better thought of as a transfer encoding, as a media type
[RFC2046], 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.
2.5. 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 unlabeled 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.
2.6. Publication Requirements
Charset registrations MAY 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.
Charset registrations SHOULD include a specification of mapping from
the charset into ISO 10646 (Unicode) [Unicode7.0] if specification of
such a mapping is feasible.
2.7. 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 [RFC1759]."
A MIBenum value for each charset will be assigned by IANA at the time
of registration. MIBenum values are not assigned by the person
registering the charset.
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3. The Charset Registry
The following procedure has been implemented by the IANA for review
and approval of new charsets. In [RFC2978] an Expert Review process
was used to add new charsets into the registry. This document
changes that model by creating a new charset registry with three new
subregistries. For each of the new registries, the registration
procedures and initial registrations are provided.
3.1. The Recommended charset registry
The first sub-registry of the full charset registry is the
"recommended" charset registry.
New registrations in the "recommended" charset registry require
"Standards Action" as defined by [RFC5226]. Specifically, the
charset MUST have a standards track RFC that defines the charset
itself and MUST ALSO have a standards track RFC recommending its use.
In the RFC that defines the charset, the document MUST have a single
recommended MIME charset label following the "mime-charset" syntax
defined in Section 2.3. It MUST also state whether it is suitable
for MIME text and have a reference to a formal specification or
translation table to Unicode [Unicode7.0].
There is one, initial entry in the Recommended charset registry:
UTF-8 [RFC3629].
3.2. The Widely-used Open Standard charset registry
The second sub-registry of the full charset registry is the "Widely-
used Open Standard" charset registry.
New registrations in the "Widely-used Open Standard" charset registry
require "Expert Review" as defined by [RFC5226]. In Section 3.2.2 of
this document a template is provided that allows proposals for new
charsets in this subregistry.
In the template that describes the charset, the template MUST provide
a single recommended MIME charset label following the "mime-charset"
syntax defined in Section 2.3. It MUST ALSO state whether it is
suitable for MIME text and have a reference to a formal specification
or translation table to Unicode.
The following charsets are to be moved from the historic charset
registry into the new "Widely-used Open Standard" subregistry: INSERT
A LIST OF CHARSET NAMES HERE. [[GUIDANCE IS REQUIRED FOR THIS
ENTRY]]
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3.2.1. Submitting "Widely-used Open Standard" charset Proposals to the
IETF Community
Send the proposed "Widely-used Open Standard" charset proposal to the
"ietf-charsets@iana.org" mailing list. (Information about joining
this list is available on the IANA Website, http://www.iana.org.)
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 posting of a charset to the list initiates a two week public
review process.
The intent of the public posting is to solicit comments and feedback
on the definition of the charset and the name chosen for it.
3.2.2. IANA Charset Registration Template
To: ietf-charsets@iana.org
Subject: Registration of new charset [names]
Charset name:
(All names must be suitable for use as the value of a MIME Content-
Type parameter, see Section 5.1 of RFC 2045.)
Charset aliases:
(All aliases must also be suitable for use as the value of a MIME
content-type parameter.)
Suitability for use in MIME text:
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 one or more CCS's and a CES then these
definitions MUST either be included or referenced.)
ISO 10646 equivalency table:
(A URI to a specification of how to translate from this charset to
ISO 10646 and vice versa SHOULD be provided.)
Additional information:
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Person & email address to contact for further information:
Intended usage:
(One of COMMON, LIMITED USE or OBSOLETE)
3.2.3. 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.
The charset reviewer must reach a decision and post it to the ietf-
charsets mailing list within two weeks. Decisions made by the
reviewer may be appealed to the IESG.
3.2.4. IANA Registration of "Widely-used Open Standard" charsets
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.
3.3. The Other charset subregistry
The third subregistry is for all other charsets. Registration of
charsets in the "other" charset subregistry is done on a "First Come,
First Served" basis as defined by [RFC5226].
4. IANA Considerations
This document requests that IANA completely revise the existing
charset registry. The new registry shold be divided into three
subregistries. These subregistries are: "Recommended charsets",
"Widely-used Open Standard charsets" and "Other charsets".
The registration procedure for the "Recommended charset" subregistry
is Standards Action required. IANA is directed to move the following
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entries from the [RFC2978] legacy registry to this subregistry: UTF-8
[RFC3629].
The registration procedure for the "Widely-used Open Standard
charset" subregistry is Expert Review. IANA is directed to move the
following entries from the [RFC2978] legacy registry to this
subregistry: INSERT A LIST OF CHARSET NAMES HERE. [[GUIDANCE IS
REQUIRED FOR THIS ENTRY]]
The registration procedure for the "Other charset" subregistry is
First Come First Served. IANA is directed to move the following
entries from the [RFC2978] legacy registry to this subregistry:
INSERT A LIST OF CHARSET NAMES HERE. [[GUIDANCE IS REQUIRED FOR THIS
ENTRY]]
In all cases the registration template specified in Section 3.2.2
must be used.
4.1. Publication of Registered Charset List
This document directs IANA to create a new XML-based registry for
charset registrations. This registry will be divided into three
subregistries as specified in Section 3 of this document."
New charset registrations will be published in the new, XML-based
registry. The proposed charset will use the approval process
appropriate for the indended, designated subregistry.
Legacy charset registrations will be converted to the new XML
registry. The instructions for converting the legacy registrations
into entries in the new subregistries are documented in Section 4 of
this document.
HISTORICAL NOTE: Previously, charset registrations were posted in the
anonymous FTP file "ftp://ftp.isi.edu/in-notes/iana/assignments/
character-sets" and all registered charsets were listed in the
periodically issued "Assigned Numbers" RFC.
5. Security Considerations
The conversion of this IANA registry - and the changes made to the
registration procedures for the new subregistries - introduces no
known security considerations. Security issues that relate to
charsets are dealt with in the RFCs that describe the protocols that
use those charsets.
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6. Acknowledgements
This document is a revision of RFC 2978 by Ned Freed and Jon Postel
and is largely based on their original text.
7. References
7.1. Normative References
[RFC0020] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969.
[RFC1759] Smith, R., Wright, F., Hastings, T., Zilles, S., and J.
Gyllenskog, "Printer MIB", RFC 1759, March 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded
Word Extensions:
Character Sets, Languages, and Continuations", RFC 2231,
November 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
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[Unicode7.0]
The Unicode Consortium, "The Unicode Standard, Version
7.0.0", 2014,
<http://www.unicode.org/versions/Unicode7.0.0/>.
7.2. Informative References
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000.
[RFC2130] Weider, C., Preston, C., Simonsen, K., Alvestrand, H.,
Atkinson, R., Crispin, M., and P. Svanberg, "The Report of
the IAB Character Set Workshop held 29 February - 1 March,
1996", RFC 2130, April 1997.
[ISO-2022]
International Organization for Standardization,
"Information technology - Character code structure and
extension techniques", ISO Standard 2022, 1994.
[ISO-10646]
International Organization for Standardization,
"Information Technology - Universal Multiple-octet coded
Character Set (UCS) - Part 1: Architecture and Basic
Multilingual Plane", ISO Standard 10646-1, May 1993.
[ISO-8859]
International Organization for Standardization,
"Information processing - 8-bit single-byte coded graphic
character sets - Part 1: Latin alphabet No. 1 (1987) -
Part 2: Latin alphabet No. 2 (1987) - Part 3: Latin
alphabet No. 3 (1988) - Part 4: Latin alphabet No. 4
(1988) - Part 5: Latin/Cyrillic alphabet (1988) - Part 6:
Latin/Arabic alphabet (1987) - Part 7: Latin/Greek
alphabet (1987) - Part 8: Latin/Hebrew alphabet (1988) -
Part 9: Latin alphabet No. 5 (1989) - Part 10: Latin
alphabet No. 6 (1992)", ISO Standard 8859, 1992.
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Appendix A. Changes Since RFC 2978
Created 3 new subregistries with different IANA registration
procedures instead of a single existing one.
Updated references, split them into Normative and Informative.
Erratum 357.
Disallow single quotes in charset names (as per RFC 2231). Erratum
1912. Note that vertical bar and backslash characters were
prohibited in RFC 2978 (a change from RFC 2278), but the change was
never noted in RFC 2978.
Authors' Addresses
Mark Mcfadden
IANA
EMail: mark.mcfadden@icann.org
Alexey Melnikov (editor)
Isode Ltd
14 Castle Mews
Hampton, Middlesex TW12 2NP
UK
EMail: Alexey.Melnikov@isode.com
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