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Versions: 00 01

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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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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