Network Working Group                                   A. Phillips, Ed.
Internet-Draft                                            Quest Software
Expires: December 25, 2005                                 M. Davis, Ed.
                                                                     IBM
                                                           June 23, 2005


                     Tags for Identifying Languages
                      draft-ietf-ltru-registry-06

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes the structure, content, construction, and
   semantics of language tags for use in cases where it is desirable to
   indicate the language used in an information object.  It also
   describes how to register values for use in language tags and the
   creation of user defined extensions for private interchange.  This
   document obsoletes RFC 3066 (which replaced RFC 1766).




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  The Language Tag . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1   Syntax . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2   Language Subtag Sources and Interpretation . . . . . . . .  6
       2.2.1   Primary Language Subtag  . . . . . . . . . . . . . . .  7
       2.2.2   Extended Language Subtags  . . . . . . . . . . . . . .  9
       2.2.3   Script Subtag  . . . . . . . . . . . . . . . . . . . . 10
       2.2.4   Region Subtag  . . . . . . . . . . . . . . . . . . . . 11
       2.2.5   Variant Subtags  . . . . . . . . . . . . . . . . . . . 12
       2.2.6   Extension Subtags  . . . . . . . . . . . . . . . . . . 13
       2.2.7   Private Use Subtags  . . . . . . . . . . . . . . . . . 15
       2.2.8   Pre-Existing RFC 3066 Registrations  . . . . . . . . . 15
       2.2.9   Classes of Conformance . . . . . . . . . . . . . . . . 15
   3.  Registry Format and Maintenance  . . . . . . . . . . . . . . . 17
     3.1   Format of the IANA Language Subtag Registry  . . . . . . . 17
     3.2   Maintenance of the Registry  . . . . . . . . . . . . . . . 22
     3.3   Stability of IANA Registry Entries . . . . . . . . . . . . 23
     3.4   Registration Procedure for Subtags . . . . . . . . . . . . 27
     3.5   Possibilities for Registration . . . . . . . . . . . . . . 30
     3.6   Extensions and Extensions Namespace  . . . . . . . . . . . 31
     3.7   Initialization of the Registry . . . . . . . . . . . . . . 34
   4.  Formation and Processing of Language Tags  . . . . . . . . . . 38
     4.1   Choice of Language Tag . . . . . . . . . . . . . . . . . . 38
     4.2   Meaning of the Language Tag  . . . . . . . . . . . . . . . 40
     4.3   Length Considerations  . . . . . . . . . . . . . . . . . . 41
       4.3.1   Working with Limited Buffer Sizes  . . . . . . . . . . 41
       4.3.2   Truncation of Language Tags  . . . . . . . . . . . . . 43
     4.4   Canonicalization of Language Tags  . . . . . . . . . . . . 43
     4.5   Considerations for Private Use Subtags . . . . . . . . . . 45
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 47
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 48
   7.  Character Set Considerations . . . . . . . . . . . . . . . . . 49
   8.  Changes from RFC 3066  . . . . . . . . . . . . . . . . . . . . 50
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
     9.1   Normative References . . . . . . . . . . . . . . . . . . . 54
     9.2   Informative References . . . . . . . . . . . . . . . . . . 55
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 56
   A.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 57
   B.  Examples of Language Tags (Informative)  . . . . . . . . . . . 58
   C.  Example Registry . . . . . . . . . . . . . . . . . . . . . . . 61
       Intellectual Property and Copyright Statements . . . . . . . . 64








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1.  Introduction

   Human beings on our planet have, past and present, used a number of
   languages.  There are many reasons why one would want to identify the
   language used when presenting or requesting information.

   User's language preferences often need to be identified so that
   appropriate processing can be applied.  For example, the user's
   language preferences in a Web browser can be used to select Web pages
   appropriately.  Language preferences can also be used to select among
   tools (such as dictionaries) to assist in the processing or
   understanding of content in different languages.

   In addition, knowledge about the particular language used by some
   piece of information content might be useful or even required by some
   types of processing; for example spell-checking, computer-synthesized
   speech, Braille transcription, or high-quality print renderings.

   One means of indicating the language used is by labeling the
   information content with an identifier or "tag".  These tags can be
   used to specify user preferences when selecting information content,
   or for labeling additional attributes of content and associated
   resources.

   Tags can also be used to indicate additional language attributes of
   content.  For example, indicating specific information about the
   dialect, writing system, or orthography used in a document or
   resource may enable the user to obtain information in a form that
   they can understand, or important in processing or rendering the
   given content into an appropriate form or style.

   This document specifies a particular identifier mechanism (the
   language tag) and a registration function for values to be used to
   form tags.  It also defines a mechanism for private use values and
   future extension.

   This document replaces RFC 3066, which replaced RFC 1766.  For a list
   of changes in this document, see Section 8.

   The keywords "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].









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2.  The Language Tag

   The language tag always defines a language as used (which includes
   being  spoken, written, signed, or otherwise signaled) by human
   beings for communication of information to other human beings.
   Computer languages such as programming languages are explicitly
   excluded.

2.1  Syntax

   The language tag is composed of one or more parts or "subtags".  Each
   subtag consists of a sequence of alpha-numeric characters.  Subtags
   are distinguished and separated from one another by a hyphen ("-").
   A language tag consists of a "primary language" subtag and a
   (possibly empty) series of subsequent subtags, each of which refines
   or narrows the range of language identified by the overall tag.

   Each type of subtag is distinguished by length, position in the tag,
   and content: subtags can be recognized solely by these features.
   This makes it possible to construct a parser that can extract and
   assign some semantic information to the subtags, even if the specific
   subtag values are not recognized.  Thus a parser need not have an up-
   to-date copy (or any copy at all) of the subtag registry to perform
   most searching and matching operations.



























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   The syntax of the language tag in ABNF [RFC2234bis] is:

   Language-Tag = (lang
                   *3("-" extlang)
                   ["-" script]
                   ["-" region]
                   *("-" variant)
                   *("-" extension)
                   ["-" privateuse])
                   / privateuse         ; private-use tag
                   / grandfathered      ; grandfathered registrations

   lang            = 2*4ALPHA           ; shortest ISO 639 code
                   / registered-lang
   extlang         = 3ALPHA             ; reserved for future use
   script          = 4ALPHA             ; ISO 15924 code
   region          = 2ALPHA             ; ISO 3166 code
                   / 3DIGIT             ; UN country number
   variant         =  5*8alphanum       ; registered variants
                   / ( DIGIT 3alphanum )
   extension       = singleton 1*("-" (2*8alphanum))
   privateuse      = ("x"/"X") 1*("-" (1*8alphanum))
   singleton       = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT
                   ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9"
                   ; Single letters: x/X is reserved for private use
   registered-lang = 4*8ALPHA          ; registered language subtag
   grandfathered   = 1*3ALPHA 1*2("-" (2*8alphanum))
                                       ; grandfathered registration
                                       ; Note: i is the only singleton
                                       ; that starts a grandfathered tag
   alphanum        = (ALPHA / DIGIT)   ; letters and numbers

                        Figure 1: Language Tag ABNF

   The character "-" is HYPHEN-MINUS (ABNF: %x2D).  All subtags have a
   maximum length of eight characters.  Note that there is a subtlety in
   the ABNF for 'variant': variants starting with a digit MAY be four
   characters long, while those starting with a letter MUST be at least
   five characters long.

   Whitespace is not permitted in a language tag.  For examples of
   language tags, see Appendix B.

   Note that although [RFC2234bis] refers to octets, the language tags
   described in this document are sequences of characters from the US-
   ASCII repertoire.  Language tags MAY be used in documents and
   applications that use other encodings, so long as these encompass the
   US-ASCII repertoire.  An example of this would be an XML document



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   that uses the UTF-16LE [RFC2781] encoding of [Unicode].

   The tags and their subtags, including private-use and extensions, are
   to be treated as case insensitive: there exist conventions for the
   capitalization of some of the subtags, but these MUST not be taken to
   carry meaning.

   For example:

   o  [ISO639-1] recommends that language codes be written in lower case
      ('mn' Mongolian).

   o  [ISO3166] recommends that country codes be capitalized ('MN'
      Mongolia).

   o  [ISO15924] recommends that script codes use lower case with the
      initial letter capitalized ('Cyrl' Cyrillic).

   However, in the tags defined by this document, the uppercase US-ASCII
   letters in the range 'A' through 'Z' are considered equivalent and
   mapped directly to their US-ASCII lowercase equivalents in the range
   'a' through 'z'.  Thus the tag "mn-Cyrl-MN" is not distinct from "MN-
   cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these
   variations conveys the same meaning: Mongolian written in the
   Cyrillic script as used in Mongolia.

2.2  Language Subtag Sources and Interpretation

   The namespace of language tags and their subtags is administered by
   the Internet Assigned Numbers Authority (IANA) [RFC2860] according to
   the rules in Section 5 of this document.  The registry maintained by
   IANA is the source for valid subtags: other standards referenced in
   this section provide the source material for that registry.

   Terminology in this section:

   o  Tag or tags refers to a complete language tag, such as
      "fr-Latn-CA".  Examples of tags in this document are enclosed in
      double-quotes ("en-US").

   o  Subtag refers to a specific section of a tag, delimited by hyphen,
      such as the subtag 'Latn' in "fr-Latn-CA".  Examples of subtags in
      this document are enclosed in single quotes ('Latn').

   o  Code or codes refers to values defined in external standards (and
      which are used as subtags in this document).  For example, 'Latn'
      is an [ISO15924] script code which was used to define the 'Latn'
      script subtag for use in a language tag.  Examples of codes in



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      this document are enclosed in single quotes ('en', 'Latn').

   The definitions in this section apply to the various subtags within
   the language tags defined by this document, excepting those
   "grandfathered" tags defined in Section 2.2.8.

   Language tags are designed so that each subtag type has unique length
   and content restrictions.  These make identification of the subtag's
   type possible, even if the content of the subtag itself is
   unrecognized.  This allows tags to be parsed and processed without
   reference to the latest version of the underlying standards or the
   IANA registry and makes the associated exception handling when
   parsing tags simpler.

   Subtags in the IANA registry that do not come from an underlying
   standard can only appear in specific positions in a tag.
   Specifically, they can only occur as primary language subtags or as
   variant subtags.

   Note that sequences of private-use and extension subtags MUST occur
   at the end of the sequence of subtags and MUST NOT be interspersed
   with subtags defined elsewhere in this document.

   Single letter and digit subtags are reserved for current or future
   use.  These include the following current uses:

   o  The single letter subtag 'x' is reserved to introduce a sequence
      of private-use subtags.  The interpretation of any private-use
      subtags is defined solely by private agreement and is not defined
      by the rules in this section or in any standard or registry
      defined in this document.

   o  All other single letter subtags are reserved to introduce
      standardized extension subtag sequences as described in
      Section 3.6.

   The single letter subtag 'i' is used by some grandfathered tags, such
   as "i-enochian", where it always appears in the first position and
   cannot be confused with an extension.

2.2.1  Primary Language Subtag

   The primary language subtag is the first subtag in a language tag
   (with the exception of private-use and certain grandfathered tags)
   and cannot be omitted.  The following rules apply to the primary
   language subtag:





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   1.  All two character language subtags were defined in the IANA
       registry according to the assignments found in the standard ISO
       639 Part 1, "ISO 639-1:2002, Codes for the representation of
       names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using
       assignments subsequently made by the ISO 639 Part 1 maintenance
       agency or governing standardization bodies.

   2.  All three character language subtags were defined in the IANA
       registry according to the assignments found in ISO 639 Part 2,
       "ISO 639-2:1998 - Codes for the representation of names of
       languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2], or
       assignments subsequently made by the ISO 639 Part 2 maintenance
       agency or governing standardization bodies.

   3.  The subtags in the range 'qaa' through 'qtz' are reserved for
       private use in language tags.  These subtags correspond to codes
       reserved by ISO 639-2 for private use.  These codes MAY be used
       for non-registered primary-language subtags (instead of using
       private-use subtags following 'x-').  Please refer to Section 4.5
       for more information on private use subtags.

   4.  All four character language subtags are reserved for possible
       future standardization.

   5.  All language subtags of 5 to 8 characters in length in the IANA
       registry were defined via the registration process in Section 3.4
       and MAY be used to form the primary language subtag.  At the time
       this document was created, there were no examples of this kind of
       subtag and future registrations of this type will be discouraged:
       primary languages are strongly RECOMMENDED for registration with
       ISO 639 and proposals rejected by ISO 639/RA will be closely
       scrutinized before they are registered with IANA.

   6.  The single character subtag 'x' as the primary subtag indicates
       that the language tag consists solely of subtags whose meaning is
       defined by private agreement.  For example, in the tag "x-fr-CH",
       the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the
       French language or the country of Switzerland (or any other value
       in the IANA registry) unless there is a private agreement in
       place to do so.  See Section 4.5.

   7.  The single character subtag 'i' is used by some grandfathered
       tags (see Section 2.2.8) such as "i-klingon" and "i-bnn".  (Other
       grandfathered tags have a primary language subtag in their first
       position)

   8.  Other values MUST NOT be assigned to the primary subtag except by
       revision or update of this document.



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   Note: For languages that have both an ISO 639-1 two character code
   and an ISO 639-2 three character code, only the ISO 639-1 two
   character code is defined in the IANA registry.

   Note: For languages that have no ISO 639-1 two character code and for
   which the ISO 639-2/T (Terminology) code and the ISO 639-2/B
   (Bibliographic) codes differ, only the Terminology code is defined in
   the IANA registry.  At the time this document was created, all
   languages that had both kinds of three character code were also
   assigned a two character code; it is not expected that future
   assignments of this nature will occur.

   Note: To avoid problems with versioning and subtag choice as
   experienced during the transition between RFC 1766 and RFC 3066, as
   well as the canonical nature of subtags defined by this document, the
   ISO 639 Registration Authority Joint Advisory Committee (ISO 639/
   RA-JAC) has included the following statement in [iso639.principles]:

   "A language code already in ISO 639-2 at the point of freezing ISO
   639-1 shall not later be added to ISO 639-1.  This is to ensure
   consistency in usage over time, since users are directed in Internet
   applications to employ the alpha-3 code when an alpha-2 code for that
   language is not available."

   In order to avoid instability of the canonical form of tags, if a two
   character code is added to ISO 639-1 for a language for which a three
   character code was already included in ISO 639-2, the two character
   code will not be added as a subtag in the registry.  See Section 3.3.

   For example, if some content were tagged with 'haw' (Hawaiian), which
   currently has no two character code, the tag would not be invalidated
   if ISO 639-1 were to assign a two character code to the Hawaiian
   language at a later date.

   For example, one of the grandfathered IANA registrations is
   "i-enochian".  The subtag 'enochian' could be registered in the IANA
   registry as a primary language subtag (assuming that ISO 639 does not
   register this language first), making tags such as "enochian-AQ" and
   "enochian-Latn" valid.

2.2.2  Extended Language Subtags

   The following rules apply to the extended language subtags:

   1.  Three letter subtags immediately following the primary subtag are
       reserved for future standardization, anticipating work that is
       currently under way on ISO 639.




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   2.  Extended language subtags MUST follow the primary subtag and
       precede any other subtags.

   3.  There MAY be up to three extended language subtags.

   4.  Extended language subtags MUST NOT be registered or used to form
       language tags.  Their syntax is described here so that
       implementations can be compatible with any future revision of
       this document which does provide for their registration.

   Extended language subtag records, once they appear in the registry,
   MUST include exactly one 'Prefix' field indicating an appropriate
   language subtag or sequence of subtags that MUST always appear as a
   prefix to the extended language subtag.

   Example: In a future revision or update of this document, the tag
   "zh-gan" (registered under RFC 3066) might become a valid non-
   grandfathered (that is, redundant) tag in which the subtag 'gan'
   might represent the Chinese dialect 'Gan'.

2.2.3  Script Subtag

   Script subtags are used to indicate the script or writing system
   variations that distinguish the written forms of a language or its
   dialects.  The following rules apply to the script subtags:

   1.  All four character subtags were defined according to
       [ISO15924]--"Codes for the representation of the names of
       scripts": alpha-4 script codes, or subsequently assigned by the
       ISO 15924 maintenance agency or governing standardization bodies,
       denoting the script or writing system used in conjunction with
       this language.

   2.  Script subtags MUST immediately follow the primary language
       subtag and all extended language subtags and MUST occur before
       any other type of subtag described below.

   3.  The script subtags 'Qaaa' through 'Qabx' are reserved for private
       use in language tags.  These subtags correspond to codes reserved
       by ISO 15924 for private use.  These codes MAY be used for non-
       registered script values.  Please refer to Section 4.5 for more
       information on private-use subtags.

   4.  Script subtags cannot be registered using the process in
       Section 3.4 of this document.  Variant subtags MAY be considered
       for registration for that purpose.





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   5.  There MUST be at most one script subtag in a language tag and the
       script subtag SHOULD be omitted when it adds no distinguishing
       value to the tag or when the primary language subtag's record
       includes a Supress-Script field listing the applicable script
       subtag.

   Example: "sr-Latn" represents Serbian written using the Latin script.

2.2.4  Region Subtag

   Region subtags are used to indicate regional or geographical
   variations that define a language or its dialects.  The following
   rules apply to the region subtags:

   1.  The region subtag defines language variations used in a specific
       region, geographic, or political area.  Region subtags MUST
       follow any language, extended language, or script subtags and
       MUST precede all other subtags.

   2.  All two character subtags following the primary subtag were
       defined in the IANA registry according to the assignments found
       in [ISO3166]--"Codes for the representation of names of countries
       and their subdivisions - Part 1: Country codes"--alpha-2 country
       codes or assignments subsequently made by the ISO 3166
       maintenance agency or governing standardization bodies.

   3.  All three character subtags consisting of digit (numeric)
       characters following the primary subtag were defined in the IANA
       registry according to the assignments found in UN Standard
       Country or Area Codes for Statistical  Use [UN_M.49] or
       assignments subsequently made by the governing standards body.
       Note that not all of the UN M.49 codes are defined in the IANA
       registry.  The following rules define which codes are entered
       into the registry as valid subtags:

       A.  UN numeric codes assigned to 'macro-geographical
           (continental)' or sub-regions MUST be registered in the
           registry.  These codes are not associated with an assigned
           ISO 3166 alpha-2 code and represent supra-national areas,
           usually covering more than one nation, state, province, or
           territory.

       B.  UN numeric codes for 'economic groupings' or 'other
           groupings' MUST NOT be registered in the IANA registry and
           MUST NOT be used to form language tags.

       C.  UN numeric codes for countries or areas with ambiguous ISO
           3166 alpha-2 codes, when entered into the registry, MUST be



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           defined according to the rules in Section 3.3 and MUST be
           used to form language tags that represent the country or
           region for which they are defined.

       D.  UN numeric codes for countries or areas for which there is an
           associated ISO 3166 alpha-2 code in the registry MUST NOT be
           entered into the registry and MUST NOT be used to form
           language tags.  Note that the ISO 3166-based subtag in the
           registry MUST actually be associated with the UN M.49 code in
           question.

       E.  All other UN numeric codes for countries or areas which do
           not have an associated ISO 3166 alpha-2 code MUST NOT be
           entered into the registry and MUST NOT be used to form
           language tags.  For more information about these codes, see
           Section 3.3.

   4.  Note: The alphanumeric codes in Appendix X of the UN document
       MUST NOT be entered into the registry and MUST NOT be used to
       form language tags.  (At the time this document was created these
       values match the ISO 3166 alpha-2 codes.)

   5.  There MUST be at most one region subtag in a language tag and the
       region subtag MAY be omitted, as when it adds no distinguishing
       value to the tag.

   6.  The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are
       reserved for private use in language tags.  These subtags
       correspond to codes reserved by ISO 3166 for private use.  These
       codes MAY be used for private use region subtags (instead of
       using a private-use subtag sequence).  Please refer to
       Section 4.5 for more information on private use subtags.

   "de-CH" represents German ('de') as used in Switzerland ('CH').

   "sr-Latn-CS" represents Serbian ('sr') written using Latin script
   ('Latn') as used in Serbia and Montenegro ('CS').

   "es-419" represents Spanish ('es') as used in the UN-defined Latin
   America and Caribbean region ('419').

2.2.5  Variant Subtags

   Variant subtags are used to indicate additional, well-recognized
   variations that define a language or its dialects which are not
   covered by other available subtags.  The following rules apply to the
   variant subtags:




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   1.  Variant subtags are not associated with any external standard.
       Variant subtags and their meanings are defined by the
       registration process defined in Section 3.4.

   2.  Variant subtags MUST follow all of the other defined subtags, but
       precede any extension or private-use subtag sequences.

   3.  More than one variant MAY be used to form the language tag.

   4.  Variant subtags MUST be registered with IANA according to the
       rules in Section 3.4 of this document before being used to form
       language tags.  In order to distinguish variants from other types
       of subtags, registrations MUST meet the following length and
       content restrictions:

       1.  Variant subtags that begin with a letter (a-z, A-Z) MUST be
           at least five characters long.

       2.  Variant subtags that begin with a digit (0-9) MUST be at
           least four characters long.

   Variant subtag records in the language subtag registry MAY include
   one or more 'Prefix' fields, which indicates the language tag or tags
   that would make a suitable prefix (with other subtags, as
   appropriate) in forming a language tag with the variant.  For
   example, the subtag 'nedis' has a Prefix of "sl", making it suitable
   to form language tags such as "sl-nedis" and "sl-IT-nedis", but not
   suitable for use in a tag such as "zh-nedis" or "it-IT-nedis".

   "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian.

   "de-CH-1996" represents German as used in Switzerland and as written
   using the spelling reform beginning in the year 1996 C.E.

   Most variants that share a prefix are mutually exclusive.  For
   example, the German orthographic variations '1996' and '1901' SHOULD
   NOT be used in the same tag, as they represent the dates of different
   spelling reforms.  A variant that can meaningfully be used in
   combination with another variant SHOULD include a 'Prefix' field in
   its registry record that lists that other variant.  For example, if
   another German variant 'example' were created that made sense to use
   with '1996', then 'example' should include two Prefix fields: "de"
   and "de-1996".

2.2.6  Extension Subtags

   Extensions provide a mechanism for extending language tags for use in
   various applications.  See: Section 3.6.  The following rules apply



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   to extensions:

   1.   Extension subtags are separated from the other subtags defined
        in this document by a single-letter subtag ("singleton").  The
        singleton MUST be one allocated to a registration authority via
        the mechanism described in Section 3.6 and cannot be the letter
        'x', which is reserved for private-use subtag sequences.

   2.   Note: Private-use subtag sequences starting with the singleton
        subtag 'x' are described below.

   3.   An extension MUST follow at least a primary language subtag.
        That is, a language tag cannot begin with an extension.
        Extensions extend language tags, they do not override or replace
        them.  For example, "a-value" is not a well-formed language tag,
        while "de-a-value" is.

   4.   Each singleton subtag MUST appear at most one time in each tag
        (other than as a private-use subtag).  That is, singleton
        subtags MUST NOT be repeated.  For example, the tag "en-a-bbb-a-
        ccc" is invalid because the subtag 'a' appears twice.  Note that
        the tag "en-a-bbb-x-a-ccc" is valid because the second
        appearance of the singleton 'a' is in a private use sequence.

   5.   Extension subtags MUST meet all of the requirements for the
        content and format of subtags defined in this document.

   6.   Extension subtags MUST meet whatever requirements are set by the
        document that defines their singleton prefix and whatever
        requirements are provided by the maintaining authority.

   7.   Each extension subtag MUST be from two to eight characters long
        and consist solely of letters or digits, with each subtag
        separated by a single '-'.

   8.   Each singleton MUST be followed by at least one extension
        subtag.  For example, the tag "tlh-a-b-foo" is invalid because
        the first singleton 'a' is followed immediately by another
        singleton 'b'.

   9.   Extension subtags MUST follow all language, extended language,
        script, region and variant subtags in a tag.

   10.  All subtags following the singleton and before another singleton
        are part of the extension.  Example: In the tag "fr-a-Latn", the
        subtag 'Latn' does not represent the script subtag 'Latn'
        defined in the IANA Language Subtag Registry.  Its meaning is
        defined by the extension 'a'.



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   11.  In the event that more than one extension appears in a single
        tag, the tag SHOULD be canonicalized as described in
        Section 4.4.

   For example, if the prefix singleton 'r' and the shown subtags were
   defined, then the following tag would be a valid example: "en-Latn-
   GB-boont-r-extended-sequence-x-private"

2.2.7  Private Use Subtags

   Private use subtags are used to indicate distinctions in language
   important in a given context by private agreement.  The following
   rules apply to private-use subtags:

   1.  Private-use subtags are separated from the other subtags defined
       in this document by the reserved single-character subtag 'x'.

   2.  Private-use subtags MUST follow all language, extended language,
       script, region, variant, and extension subtags in the tag.
       Another way of saying this is that all subtags following the
       singleton 'x' MUST be considered private use.  Example: The
       subtag 'US' in the tag "en-x-US" is a private use subtag.

   3.  A tag MAY consist entirely of private-use subtags.

   4.  No source is defined for private use subtags.  Use of private use
       subtags is by private agreement only.

   For example: Users who wished to utilize SIL Ethnologue for
   identification might agree to exchange tags such as "az-Arab-x-AZE-
   derbend".  This example contains two private-use subtags.  The first
   is 'AZE' and the second is 'derbend'.

2.2.8  Pre-Existing RFC 3066 Registrations

   Existing IANA-registered language tags from RFC 1766 and/or RFC 3066
   maintain their validity.  IANA will maintain these tags in the
   registry under either the "grandfathered" or "redundant" type.  For
   more information see Section 3.7.

   It is important to note that all language tags formed under the
   guidelines in this document were either legal, well-formed tags or
   could have been registered under RFC 3066.

2.2.9  Classes of Conformance

   Implementations sometimes need to describe their capabilities with
   regard to the rules and practices described in this document.  There



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   are two classes of conforming implementations described by this
   document: "well-formed" processors and "validating" processors.
   Claims of conformance SHOULD explicitly reference one of these
   definitions.

   An implementation that claims to check for well-formed language tags
   MUST:

   o  Check that the tag and all of its subtags, including extension and
      private-use subtags, conform to the ABNF or that the tag is on the
      list of grandfathered tags.

   o  Check that singleton subtags that identify extensions do not
      repeat.  For example, the tag "en-a-xx-b-yy-a-zz" is not well-
      formed.

   Well-formed processors are strongly encouraged to implement the
   canonicalization rules contained in Section 4.4.

   An implementation that claims to be validating MUST:

   o  Check that the tag is well-formed.

   o  Specify the particular registry date for which the implementation
      performs validation of subtags.

   o  Check that either the tag is a grandfathered tag, or that all
      language, script, region, and variant subtags consist of valid
      codes for use in language tags according to the IANA registry as
      of the particular date specified by the implementation.

   o  Specify which, if any, extension RFCs as defined in Section 3.6
      are supported, including version, revision, and date.

   o  For any such extensions supported, check that all subtags used in
      that extension are valid.

   o  For variant and extended language subtags, if the registry
      contains one or more 'Prefix' fields for that subtag, check that
      the tag matches at least one prefix.  The tag matches if all the
      subtags in the 'Prefix' also appear in the tag.  For example, the
      prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both
      the 'es' language subtag and 'CO' region subtag appear in the tag.








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3.  Registry Format and Maintenance

   This section defines the Language Subtag Registry and the maintenance
   and update procedures associated with it.

   The language subtag registry will be maintained so that, except for
   extension subtags, it is possible to validate all of the subtags that
   appear in a language tag under the provisions of this document or its
   revisions or successors.  In addition, the meaning of the various
   subtags will be unambiguous and stable over time.  (The meaning of
   private-use subtags, of course, is not defined by the IANA registry.)

   The registry defined under this document contains a comprehensive
   list of all of the subtags valid in language tags.  This allows
   implementers a straightforward and reliable way to validate language
   tags.

3.1  Format of the IANA Language Subtag Registry

   The IANA Language Subtag Registry ("the registry") will consist of a
   text file that is machine readable in the format described in this
   section, plus copies of the registration forms approved by the
   Language Subtag Reviewer in accordance with the process described in
   Section 3.4.  With the exception of the registration forms for
   grandfathered and redundant tags, no registration records will be
   maintained for the initial set of subtags.

   The registry will be in a modified record-jar format text file
   [record-jar].  Lines are limited to 72 characters, including all
   whitespace.

   Records are separated by lines containing only the sequence "%%"
   (%x25.25).

   Each field can be viewed as a single, logical  line  of ASCII
   characters,  comprising  a field-name and a field-body separated by a
   COLON character (%x3A).  For convenience, the field-body  portion  of
   this  conceptual entity  can be split into a multiple-line
   representation; this is called "folding".  The format of the registry
   is described by the following ABNF (per [RFC2234bis]):

   registry   = record *("%%" CRLF record)
   record     = 1*( field-name *SP ":" *SP field-body CRLF )
   field-name = *(ALPHA / DIGIT / "-")
   field-body = *(ASCCHAR/LWSP)
   ASCCHAR    = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26
   UNICHAR    = "&#x" 2*6HEXDIG ";"




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   The sequence '..' (%x2E.2E) in a field-body denotes a range of
   values.  Such a range represents all subtags of the same length that
   are alphabetically within that range, including the values explicitly
   mentioned.  For example 'a..c' denotes the values 'a', 'b', and 'c'.

   Characters from outside the US-ASCII repertoire, as well as the
   AMPERSAND character ("&", %x26) when it occurs in a field-body are
   represented by a "Numeric Character Reference" using hexadecimal
   notation in the style used by [XML10] (see
   <http://www.w3.org/TR/REC-xml/#dt-charref>).  This consists of the
   sequence "&#x" (%x26.23.78) followed by a hexadecimal representation
   of the character's code point in [ISO10646] followed by a closing
   semicolon (%x3B).  For example, the EURO SIGN, U+20AC, would be
   represented by the sequence "&#x20AC;".  Note that the hexadecimal
   notation MAY have between two and six digits.

   All fields whose field-body contains a date value use the "full-date"
   format specified in [RFC3339].  For example: "2004-06-28" represents
   June 28, 2004 in the Gregorian calendar.

   The first record in the file contains the single field whose field-
   name is "File-Date".  The field-body of this record contains the last
   modification date of this copy of the registry, making it possible to
   compare different versions of the registry.  The registry on the IANA
   website is the most current.  Versions with an older date than that
   one are not up-to-date.

   File-Date: 2004-06-28
   %%

   Subsequent records represent subtags in the registry.  Each of the
   fields in each record MUST occur no more than once, unless otherwise
   noted below.  Each record MUST contain the following fields:

   o  'Type'

      *  Type's field-value MUST consist of one of the following
         strings: "language", "extlang", "script", "region", "variant",
         "grandfathered", and "redundant" and denotes the type of tag or
         subtag.

   o  Either 'Subtag' or 'Tag'

      *  Subtag's field-value contains the subtag being defined.  This
         field MUST only appear in records of whose Type has one of
         these values: "language", "extlang", "script", "region", or
         "variant".




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      *  Tag's field-value contains a complete language tag.  This field
         MUST only appear in records whose Type has one of these values:
         "grandfathered" or "redundant".

   o  Description

      *  Description's field-value contains a non-normative description
         of the subtag or tag.

   o  Added

      *  Added's field-value contains the date the record was added to
         the registry.

   The 'Subtag' or 'Tag' field MUST use lowercase letters to form the
   subtag or tag, with two exceptions.  Subtags whose 'Type' field is
   'script' (in other words, subtags defined by ISO 15924) MUST use
   titlecase.  Subtags whose 'Type' field is 'region' (in other words,
   subtags defined by ISO 3166) MUST use uppercase.  These exceptions
   mirror the use of case in the underlying standards.

   The field 'Description' MAY appear more than one time.  At least one
   of the  'Description' fields MUST contain a description of the tag
   being registered written or transcribed into the Latin script; the
   same or additional fields MAY also include a description in a non-
   Latin script.  The 'Description' field is used for identification
   purposes and SHOULD NOT be taken to represent the actual native name
   of the language or variation or to be in any particular language.
   Most descriptions are taken directly from source standards such as
   ISO 639 or ISO 3166.

   Note: Descriptions in registry entries that correspond to ISO 639,
   ISO 15924,  ISO 3166 or UN M.49 codes are intended only to indicate
   the meaning of that identifier as defined in the source standard at
   the time it was added to the registry.  The description does not
   replace the content of the source standard itself.  The descriptions
   are not intended to be the English localized names for the subtags.
   Localization or translation of language tag and subtag descriptions
   is out of scope of this document.

   Each record MAY also contain the following fields:

   o  Preferred-Value

      *  For fields of type 'language', 'extlang', 'script', 'region',
         and 'variant', 'Preferred-Value' contains a subtag of the same
         'Type' which is preferred for forming the language tag.




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      *  For fields of type 'grandfathered' and 'redundant', a canonical
         mapping to a complete language tag.

   o  Deprecated

      *  Deprecated's field-value contains the date the record was
         deprecated.

   o  Prefix

      *  Prefix's field-value contains a language tag with which this
         subtag MAY be used to form a new language tag, perhaps with
         other subtags as well.  This field MUST only appear in records
         whose 'Type' field-value is 'variant' or 'extlang'.  For
         example, the 'Prefix' for the variant 'nedis' is 'sl', meaning
         that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate
         while the tag "is-nedis" is not.

   o  Comments

      *  Comments contains additional information about the subtag, as
         deemed appropriate for understanding the registry and
         implementing language tags using the subtag or tag.

   o  Suppress-Script

      *  Suppress-Script contains a script subtag that SHOULD NOT be
         used to form language tags with the associated primary language
         subtag.  This field MUST only appear in records whose 'Type'
         field-value is 'language'.  See Section 4.1.

   The field 'Deprecated' MAY be added to any record via the maintenance
   process described in Section 3.2 or via the registration process
   described in Section 3.4.  Usually the addition of a 'Deprecated'
   field is due to the action of one of the standards bodies, such as
   ISO 3166, withdrawing a code.  In some historical cases it might not
   have been  possible to reconstruct the original deprecation date.
   For these cases, an approximate date appears in the registry.
   Although valid in language tags, subtags and tags with a 'Deprecated'
   field are deprecated and validating processors SHOULD NOT generate
   these subtags.  Note that a record that contains a 'Deprecated' field
   and no corresponding 'Preferred-Value' field has no replacement
   mapping.

   Thie field 'Preferred-Value' contains a mapping between the record in
   which it appears and a tag or subtag which SHOULD be preferred when
   selected language tags.  These values form three groups:




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      ISO 639 language codes which were later withdrawn in favor of
      other codes.  These values are mostly a historical curiosity.

      ISO 3166 region codes which have been withdrawn in favor of a new
      code.  This sometimes happens when a country changes its name or
      administration in such a way that warrants a new region code.

      Tags grandfathered from RFC 3066.  In many cases these tags have
      become obsolete because the values they represent were later
      encoded by ISO 639.

   Records that contain a 'Preferred-Value' field MUST also have a
   'Deprecated' field.  This field contains a date of deprecation.  Thus
   a language tag processor can use the registry to construct the valid,
   non-deprecated set of subtags for a given date.  In addition, for any
   given tag, a processor can construct the set of valid language tags
   that correspond to that tag for all dates up to the date of the
   registry.  The ability to do these mappings MAY be beneficial to
   applications that are matching, selecting, for filtering content
   based on its language tags.

   Note that 'Preferred-Value' mappings in records of type 'region' MAY
   NOT represent exactly the same meaning as the original value.  There
   are many reasons for a country code to be changed and the effect this
   has on the formation of language tags will depend on the nature of
   the change in question.

   In particular, the 'Preferred-Value' field does not imply retagging
   content that uses the affected subtag.

   The field 'Preferred-Value' MUST NOT be modified once created in the
   registry.  The field MAY be added to records of type "grandfathered"
   and "region" according to the rules in Section 3.2.  Otherwise the
   field MUST NOT be added to any record already in the registry.

   The 'Preferred-Value' field in records of type "grandfathered" and
   "redundant" contains whole language tags that are strongly
   RECOMMENDED for use in place of the record's value.  In many cases
   the mappings were created by deprecation of the tags during the
   period before this document was adopted.  For example, the tag "no-
   nyn" was deprecated in favor of the ISO 639-1 defined language code
   'nn'.

   Records of type 'variant' MAY have more than one field of type
   'Prefix'.  Additional fields of this type MAY be added to a 'variant'
   record via the registration process.

   Records of type 'extlang' MUST have _exactly_ one 'Prefix' field.



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   The field-value of the 'Prefix' field consists of a language tag
   whose subtags are appropriate to use with this subtag.  For example,
   the variant subtag '1996' has a Prefix field of "de".  This means
   that tags starting with the sequence "de-" are appropriate with this
   subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while
   the tag "fr-1996" is an inappropriate choice.

   The field of type 'Prefix' MUST NOT be removed from any record.  The
   field-value for this type of field MUST NOT be modified.

   The field 'Comments' MAY appear more than once per record.  This
   field MAY be inserted or changed via the registration process and no
   guarantee of stability is provided.  The content of this field is not
   restricted, except by the need to register the information, the
   suitability of the request, and by reasonable practical size
   limitations.  Long screeds about a particular subtag are frowned
   upon.

   The field 'Suppress-Script' MUST only appear in records whose 'Type'
   field-value is 'language'.  This field MAY appear at most one time in
   a record.  This field indicates a script used to write the
   overwhelming majority of documents for the given language and which
   therefore adds no distinguishing information to a language tag.  It
   helps ensure greater compatibility between the language tags
   generated according to the rules in this document and language tags
   and tag processors or consumers based on RFC 3066.  For example,
   virtually all Icelandic documents are written in the Latin script,
   making the subtag 'Latn' redundant in the tag "is-Latn".

   For examples of registry entries and their format, see Appendix C.

3.2  Maintenance of the Registry

   Maintenance of the registry requires that as codes are assigned or
   withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language
   Subtag Reviewer will evaluate each change, determine whether it
   conflicts with existing registry entries, and submit the information
   to IANA for inclusion in the registry.  If an change takes place and
   the Language Subtag Reviewer does not do this in a timely manner,
   then any interested party MAY use the procedure in Section 3.4 to
   register the appropriate update.

   Note: The redundant and grandfathered entries together are the
   complete list of tags registered under [RFC3066].  The redundant tags
   are those that can now be formed using the subtags defined in the
   registry together with the rules of  Section 2.2.  The grandfathered
   entries are those that can never be legal under those same
   provisions.



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   The set of redundant and grandfathered tags is permanent and stable:
   no new entries will be added and none of the entries will be removed.
   Records of type 'grandfathered' MAY have their type converted to
   'redundant': see  Section 3.7 for more information.

   RFC 3066 tags that were deprecated prior to the adoption of this
   document are part of the list of grandfathered tags and their
   component subtags were not included as registered variants (although
   they remain eligible for registration).  For example, the tag "art-
   lojban" was deprecated in favor of the language subtag 'jbo'.

   The Language Subtag Reviewer MUST ensure that new subtags meet the
   requirements in Section 4.1 or submit an appropriate alternate subtag
   as described in that section.  If a change or addition to the
   registry is needed, the Language Subtag Reviewer will prepare the
   complete record, including all fields, and forward it to IANA for
   insertion into the registry.  If this represents a new subtag, then
   the message will indicate that this represents an INSERTION of a
   record.  If this represents a change to an existing subtag, then the
   message MUST indicate that this represents a MODIFICATION, as shown
   in the following example:

   LANGUAGE SUBTAG MODIFICATION
   File-Date: 2005-01-02
   %%
   Type: variant
   Subtag: nedis
   Description: Natisone dialect
   Description: Nadiza dialect
   Added: 2003-10-09
   Prefix: sl
   Comments: This is a comment shown
     as an example.
   %%

                                 Figure 4

   Whenever an entry is created or modified in the registry, the 'File-
   Date' record at the start of the registry is updated to reflect the
   most recent modification date in the [RFC3339] "full-date" format.

   Values in the 'Subtag' field MUST be lowercase except as provided for
   in Section 3.1.

3.3  Stability of IANA Registry Entries

   The stability of entries and their meaning in the registry is
   critical to the long term stability of language tags.  The rules in



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   this section guarantee that a specific language tag's meaning is
   stable over time and will not change.

   These rules specifically deal with how changes to codes (including
   withdrawal and deprecation of codes) maintained by ISO 639, ISO
   15924, ISO 3166, and UN M.49 are reflected in the IANA Language
   Subtag Registry.  Assignments to the IANA Language Subtag Registry
   MUST follow the following stability rules:

   o  Values in the fields 'Type', 'Subtag', 'Tag', 'Added',
      'Deprecated' and 'Preferred-Value' MUST NOT be changed and are
      guaranteed to be stable over time.

   o  Values in the 'Description' field MUST NOT be changed in a way
      that would invalidate previously-existing tags.  They MAY be
      broadened somewhat in scope, changed to add information, or
      adapted to the most common modern usage.  For example, countries
      occasionally change their official names: an historical example of
      this would be "Upper Volta" changing to "Burkina Faso".

   o  Values in the field 'Prefix' MAY be added to records of type
      'variant' via the registration process.

   o  Values in the field 'Prefix' MAY be modified, so long as the
      modifications broaden the set of prefixes.  That is, a prefix MAY
      be replaced by one of its own prefixes.  For example, the prefix
      "en-US" could be replaced by "en", but not by the prefixes "en-
      Latn", "fr", or "en-US-boont".  If one of those prefixes were
      needed, a new Prefix SHOULD be registered.

   o  Values in the field 'Prefix' MUST NOT be removed.

   o  The field 'Comments' MAY be added, changed, modified, or removed
      via the registration process or any of the processes or
      considerations described in this section.

   o  The field 'Suppress-Script' MAY be added or removed via the
      registration process.

   o  Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not
      conflict with existing subtags of the associated type and whose
      meaning is not the same as an existing subtag of the same type are
      entered into the IANA registry as new records.

   o  Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are
      withdrawn by their respective maintenance or registration
      authority remain valid in language tags.  A 'Deprecated' field
      containing the date of withdrawal is added to the record.  If a



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      new record of the same type is added that represents a replacement
      value, then a 'Preferred-Value' field MAY also be added.  The
      registration process MAY be used to add comments about the
      withdrawal of the code by the respective standard.

      *  The region code 'TL' was assigned to the country 'Timor-Leste',
         replacing the code 'TP' (which was assigned to 'East Timor'
         when it was under administration by Portugal).  The subtag 'TP'
         remains valid in language tags, but its record contains the a
         'Preferred-Value' of 'TL' and its field 'Deprecated' contains
         the date the new code was assigned ('2004-07-06').

   o  Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict
      with existing subtags of the associated type, including subtags
      that are deprecated, MUST NOT be entered into the registry.  The
      following additional considerations apply to subtag values that
      are reassigned:

      *  For ISO 639 codes, if the newly assigned code's meaning is not
         represented by a subtag in the IANA registry, the Language
         Subtag Reviewer, as described in Section 3.4, SHALL prepare a
         proposal for entering in the IANA registry as soon as practical
         a registered language subtag as an alternate value for the new
         code.  The form of the registered language subtag will be at
         the discretion of the Language Subtag Reviewer and MUST conform
         to other restrictions on language subtags in this document.

      *  For all subtags whose meaning is derived from an external
         standard (i.e.  ISO 639, ISO 15924, ISO 3166, or UN M.49), if a
         new meaning is assigned to an existing code and the new meaning
         broadens the meaning of that code, then the meaning for the
         associated subtag MAY be changed to match.  The meaning of a
         subtag MUST NOT be narrowed, however, as this can result in an
         unknown proportion of the existing uses of a subtag becoming
         invalid.  Note: ISO 639 MA/RA has adopted a similar stability
         policy.

      *  For ISO 15924 codes, if the newly assigned code's meaning is
         not represented by a subtag in the IANA registry, the Language
         Subtag Reviewer, as described in Section 3.4, SHALL prepare a
         proposal for entering in the IANA registry as soon as practical
         a registered variant subtag as an alternate value for the new
         code.  The form of the registered variant subtag will be at the
         discretion of the Language Subtag Reviewer and MUST conform to
         other restrictions on variant subtags in this document.

      *  For ISO 3166 codes, if the newly assigned code's meaning is
         associated with the same UN M.49 code as another 'region'



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         subtag, then the existing region subtag remains as the
         preferred value for that region and no new entry is created.  A
         comment MAY be added to the existing region subtag indicating
         the relationship to the new ISO 3166 code.

      *  For ISO 3166 codes, if the newly assigned code's meaning is
         associated with a UN M.49 code that is not represented by an
         existing region subtag, then the Language Subtag Reviewer, as
         described in Section 3.4, SHALL prepare a proposal for entering
         the appropriate UN M.49 country code as an entry in the IANA
         registry.

      *  Codes assigned by UN M.49 to countries or areas (as opposed to
         geographical regions and sub-regions) for which there is no
         corresponding ISO 3166 code MUST NOT be registered, except
         under the previous provision.  If it is necessary to identify a
         region for which only a UN M.49 code exists in language tags,
         then the registration authority for ISO 3166 SHOULD be
         petitioned to assign a code, which can then be registered for
         use in language tags.  At the time this document was written,
         there were only four such codes: 830 (Channel Islands), 831
         (Guernsey), 832 (Jersey), and 833 (Isle of Man).  This rule
         exists so that UN M.49 codes remain available as the value of
         last resort in cases where ISO 3166 reassigns a deprecated
         value in the registry.

      *  For ISO 3166 codes, if there is no associated UN numeric code,
         then the Language Subtag Reviewer SHALL petition the UN to
         create one.  If there is no response from the UN within ninety
         days of the request being sent, the Language Subtag Reviewer
         SHALL prepare a proposal for entering in the IANA registry as
         soon as practical a registered variant subtag as an alternate
         value for the new code.  The form of the registered variant
         subtag will be at the discretion of the Language Subtag
         Reviewer and MUST conform to other restrictions on variant
         subtags in this document.  This situation is very unlikely to
         ever occur.

   o  Stability provisions apply to grandfathered tags with this
      exception: should all of the subtags in a grandfathered tag become
      valid subtags in the IANA registry, then the field 'Type' in that
      record is changed from 'grandfathered' to 'redundant'.  Note that
      this will not affect language tags that match the grandfathered
      tag, since these tags will now match valid generative subtag
      sequences.  For example, if the subtag 'gan' in the language tag
      "zh-gan" were to be registered as an extended language subtag,
      then the grandfathered tag "zh-gan" would be deprecated (but
      existing content or implementations that use "zh-gan" would remain



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      valid).


3.4  Registration Procedure for Subtags

   The procedure given here MUST be used by anyone who wants to use a
   subtag not currently in the IANA Language Subtag Registry.

   Only subtags  of type 'language' and 'variant' will be considered for
   independent registration of new subtags.  Handling of subtags needed
   for stability and subtags necessary to keep the registry synchronized
   with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits
   defined by this document are described in Section 3.2.  Stability
   provisions are described in Section 3.3.

   This procedure MAY also be used to register or alter the information
   for the "Description", "Comments", "Deprecated", or "Prefix" fields
   in a subtag's record as described in Figure 9.  Changes to all other
   fields in the IANA registry are NOT permitted.

   Registering a new subtag or requesting modifications to an existing
   tag or subtag starts with the requester filling out the registration
   form reproduced below.  Note that each response is not limited in
   size so that the request can adequately describe the registration.
   The fields in the "Record Requested" section SHOULD follow the
   requirements in Section 3.1.

   LANGUAGE SUBTAG REGISTRATION FORM
   1. Name of requester:
   2. E-mail address of requester:
   3. Record Requested:

   Type:
   Subtag:
   Description:
   Prefix:
   Preferred-Value:
   Deprecated:
   Suppress-Script:
   Comments:

   4. Intended meaning of the subtag:
   5. Reference to published description
   of the language (book or article):
   6. Any other relevant information:

                                 Figure 5




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   The subtag registration form MUST be sent to
   <ietf-languages@iana.org> for a two week review period before it can
   be submitted to IANA.  (This is an open list and can be joined by
   sending a request to <ietf-languages-request@iana.org>.)

   Variant and extlang subtags are always registered for use with a
   particular range of language tags.  For example, the subtag 'rozaj'
   is intended for use with language tags that start with the primary
   language subtag "sl", since Resian is a dialect of Slovenian.  Thus
   the subtag 'rozaj' could be included in tags such as "sl-Latn-rozaj"
   or "sl-IT-rozaj".  This information is stored in the "Prefix" field
   in the registry.  Variant registration requests are REQUIRED to
   include at least one "Prefix" field in the registration form.

   The 'Prefix' field for a given registered subtag will be maintained
   in the IANA registry as a guide to usage.  Additional prefixes MAY be
   added by filing an additional registration form.  In that form, the
   "Any other relevant information:" field MUST indicate that it is the
   addition of a prefix.

   Requests to add a prefix to a variant subtag that imply a different
   semantic meaning will probably be rejected.  For example, a request
   to add the prefix "de" to the subtag 'nedis' so that the tag "de-
   nedis" represented some German dialect would be rejected.  The
   'nedis' subtag represents a particular Slovenian dialect and the
   additional registration would change the semantic meaning assigned to
   the subtag.  A separate subtag SHOULD be proposed instead.

   The 'Description' field MUST contain a description of the tag being
   registered written or transcribed into the Latin script; it MAY also
   include a description in a non-Latin script.  Non-ASCII characters
   MUST be escaped using the syntax described in Section 3.1.  The
   'Description' field is used for identification purposes and doesn't
   necessarily  represent the actual native name of the language or
   variation or to be in any particular language.

   While the 'Description' field itself is not guaranteed to be stable
   and errata corrections MAY be undertaken from time to time, attempts
   to provide translations or transcriptions of entries in the registry
   itself will probably be frowned upon by the community or rejected
   outright, as changes of this nature have an impact on the provisions
   in Section 3.3.

   The Language Subtag Reviewer is responsible for responding to
   requests for the registration of subtags through the registration
   process  and is appointed by the IESG.

   When the two week period has passed the Language Subtag Reviewer



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   either forwards the record to be inserted or modified to
   iana@iana.org according to the procedure described in Section 3.2, or
   rejects the request because of significant objections raised on the
   list or due to problems with constraints in this document (which MUST
   be explicitly cited).  The reviewer MAY also extend the review period
   in two week increments to permit further discussion.  The reviewer
   MUST indicate on the list whether the registration has been accepted,
   rejected, or extended following each two week period.

   Note that the reviewer can raise objections on the list if he or she
   so desires.  The important thing is that the objection MUST be made
   publicly.

   The applicant is free to modify a rejected application with
   additional information and submit it again; this restarts the two
   week comment period.

   Decisions made by the reviewer MAY be appealed to the IESG [RFC2028]
   under the same rules as other IETF decisions [RFC2026].

   All approved registration forms are available online in the directory
   http://www.iana.org/numbers.html under "languages".

   Updates or changes to existing records, including previous
   registrations, follow the same procedure as new registrations.  The
   Language Subtag Reviewer decides whether there is consensus to update
   the registration following the two week review period; normally
   objections by the original registrant will carry extra weight in
   forming such a consensus.

   Registrations are permanent and stable.  Once registered, subtags
   will not be removed from the registry and will remain a valid way in
   which to specify a specific language or variant.

   Note: The purpose of the "Description" in the registration form is
   intended as an aid to people trying to verify whether a language is
   registered or what language or language variation a particular subtag
   refers to.  In most cases, reference to an authoritative grammar or
   dictionary of that language will be useful; in cases where no such
   work exists, other well known works describing that language or in
   that language MAY be appropriate.  The subtag reviewer decides what
   constitutes "good enough" reference material.  This requirement is
   not intended to exclude particular languages or dialects due to the
   size of the speaker population or lack of a standardized orthography.
   Minority languages will be considered equally on their own merits.






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3.5  Possibilities for Registration

   Possibilities for registration of subtags or information about
   subtags include:

   o  Primary language subtags for languages not listed in ISO 639 that
      are not variants of any listed or registered language can be
      registered.  At the time this document was created there were no
      examples of this form of subtag.  Before attempting to register a
      language subtag, there MUST be an attempt to register the language
      with ISO 639.  No language subtags will be registered for codes
      that exist in ISO 639-1 or ISO 639-2, which are under
      consideration by the ISO 639 maintenance or registration
      authorities, or which have never been attempted for registration
      with those authorities.  If ISO 639 has previously rejected a
      language for registration, it is reasonable to assume that there
      must be additional very compelling evidence of need before it will
      be registered in the IANA registry (to the extent that it is very
      unlikely that any subtags will be registered of this type).

   o  Dialect or other divisions or variations within a language, its
      orthography, writing system, regional or historical usage,
      transliteration or other transformation, or distinguishing
      variation MAY be registered as variant subtags.  An example is the
      'rozaj' subtag (the Resian dialect of Slovenian).

   o  The addition or maintenance of fields (generally of an
      informational nature) in Tag or Subtag records as described in
      Section 3.1 and subject to the stability provisions in
      Section 3.3.  This includes  descriptions; comments; deprecation
      and preferred values for obsolete or withdrawn codes; or the
      addition of script or extlang information to primary language
      subtags.

   o  The addition of records and related field value changes necessary
      to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and
      UN  M.49 as described in Section 3.3.

   This document leaves the decision on what subtags  or changes to
   subtags are appropriate (or not) to the registration process
   described in Section 3.4.

   Note: four character primary language subtags are reserved to allow
   for the possibility of  alpha4 codes in some future addition to the
   ISO 639 family of standards.

   ISO 639 defines a maintenance agency for additions to and changes in
   the list of languages in ISO 639.  This agency is:



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   International Information Centre for Terminology (Infoterm)
   Aichholzgasse 6/12, AT-1120
   Wien, Austria
   Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72

   ISO 639-2 defines a maintenance agency for additions to and changes
   in the list of languages in ISO 639-2.  This agency is:

   Library of Congress
   Network Development and MARC Standards Office
   Washington, D.C. 20540 USA
   Phone: +1 202 707 6237  Fax: +1 202 707 0115
   URL: http://www.loc.gov/standards/iso639

   The maintenance agency for ISO 3166 (country codes) is:

   ISO 3166 Maintenance Agency
   c/o International Organization for Standardization
   Case postale 56
   CH-1211 Geneva 20 Switzerland
   Phone: +41 22 749 72 33  Fax: +41 22 749 73 49
   URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html

   The registration authority for ISO 15924 (script codes) is:

   Unicode Consortium Box 391476
   Mountain View, CA 94039-1476, USA
   URL: http://www.unicode.org/iso15924

   The Statistics Division of the United Nations Secretariat maintains
   the Standard Country or Area Codes for Statistical Use and can be
   reached at:

   Statistical Services Branch
   Statistics Division
   United Nations, Room DC2-1620
   New York, NY 10017, USA

   Fax: +1-212-963-0623
   E-mail: statistics@un.org
   URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm

3.6  Extensions and Extensions Namespace

   Extension subtags are those introduced by single-letter subtags other
   than 'x'.  They are reserved for the generation of identifiers which
   contain a language component, and are compatible with applications
   that understand language tags.  For example, they might be used to



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   define locale identifiers, which are generally based on language.

   The structure and form of extensions are defined by this document so
   that implementations can be created that are forward compatible with
   applications that might be created using single-letter subtags in the
   future.  In addition, defining a mechanism for maintaining single-
   letter subtags will lend to the stability of this document by
   reducing the likely need for future revisions or updates.

   Allocation of a single-letter subtag SHALL take the form of an RFC
   defining the name, purpose, processes, and procedures for maintaining
   the subtags.  The maintaining or registering authority, including
   name, contact email, discussion list email, and URL location of the
   registry MUST be indicated clearly in the RFC.  The RFC MUST specify
   or include each of the following:

   o  The specification MUST reference the specific version or revision
      of this document that governs its creation and MUST reference this
      section of this document.

   o  The specification and all subtags defined by the specification
      MUST follow the ABNF and other rules for the formation of tags and
      subtags as defined in this document.  In particular it MUST
      specify that case is not significant and that subtags MUST NOT
      exceed eight characters in length.

   o  The specification MUST specify a canonical representation.

   o  The specification of valid subtags MUST be available over the
      Internet and at no cost.

   o  The specification MUST be in the public domain or available via a
      royalty-free license acceptable to the IETF and specified in the
      RFC.

   o  The specification MUST be versioned and each version of the
      specification MUST be numbered, dated, and stable.

   o  The specification MUST be stable.  That is, extension subtags,
      once defined by a specification, MUST NOT be retracted or change
      in meaning in any substantial way.

   o  The specification MUST include in a separate section the
      registration form reproduced in this section (below) to be used in
      registering the extension upon publication as an RFC.

   o  IANA MUST be informed of changes to the contact information and
      URL for the specification.



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   IANA will maintain a registry of allocated single-letter (singleton)
   subtags.  This registry will use the record-jar format described by
   the ABNF in Section 3.1.  Upon publication of an extension as an RFC,
   the maintaining authority defined in the RFC MUST forward this
   registration form to iesg@ietf.org, who will forward the request to
   iana@iana.org.  The maintaining authority of the extension MUST
   maintain the accuracy of the record by sending an updated full copy
   of the record to iana@iana.org with the subject line "LANGUAGE TAG
   EXTENSION UPDATE" whenever content changes.  Only the 'Comments',
   'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in
   these updates.

   Failure to maintain this record, the corresponding registry, or meet
   other conditions imposed by this section of this document MAY be
   appealed to the IESG [RFC2028] under the same rules as other IETF
   decisions (see [RFC2026]) and MAY result in the authority to maintain
   the extension being withdrawn or reassigned by the IESG.
   %%
   Identifier:
   Description:
   Comments:
   Added:
   RFC:
   Authority:
   Contact_Email:
   Mailing_List:
   URL:
   %%

    Figure 6: Format of Records in the Language Tag Extensions Registry

   'Identifier' contains the single letter subtag (singleton) assigned
   to the extension.  The Internet-Draft submitted to define the
   extension SHOULD specify which letter to use, although the IESG MAY
   change the assignment when approving the RFC.

   'Description' contains the name and description of the extension.

   'Comments' is an OPTIONAL field and MAY contain a broader description
   of the extension.

   'Added' contains the date the RFC was published in the "full-date"
   format specified in [RFC3339].  For example: 2004-06-28 represents
   June 28, 2004, in the Gregorian calendar.

   'RFC' contains the RFC number assigned to the extension.

   'Authority' contains the name of the maintaining authority for the



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   extension.

   'Contact_Email' contains the email address used to contact the
   maintaining authority.

   'Mailing_List' contains the URL or subscription email address of the
   mailing list used by the maintaining authority.

   'URL' contains the URL of the registry for this extension.

   The determination of whether an Internet-Draft meets the above
   conditions and the decision to grant or withhold such authority rests
   solely with the IESG, and is subject to the normal review and appeals
   process associated with the RFC process.

   Extension authors are strongly cautioned that many (including most
   well-formed) processors will be unaware of any special relationships
   or meaning inherent in the order of extension subtags.  Extension
   authors SHOULD avoid subtag relationships or canonicalization
   mechanisms that interfere with matching or with length restrictions
   that sometimes exist in common protocols where the extension is used.
   In particular, applications MAY truncate the subtags in doing
   matching or in fitting into limited lengths, so it is RECOMMENDED
   that the most significant information be in the most significant
   (left-most) subtags, and that the specification gracefully handle
   truncated subtags.

   When a language tag is to be used in a specific, known, protocol, it
   is RECOMMENDED that that the language tag not contain extensions not
   supported by that protocol.  In addition, note that some protocols
   MAY impose upper limits on the length of the strings used to store or
   transport the language tag.

3.7  Initialization of the Registry

   Upon publication of this document as a BCP, the Language Subtag
   Registry MUST be created and populated with the initial set of
   subtags.  This includes converting the entries from the existing IANA
   language tag registry defined by RFC 3066 to the new format.  This
   section defines the process for defining the new registry and
   performing the conversion of the old registry.

   The impact on the IANA maintainers of the registry of this conversion
   will be a small increase in the frequency of new entries.  The
   initial set of records represents no impact on IANA, since the work
   to create it will be performed externally (as defined in this
   section).  Future work will be limited to inserting or replacing
   whole records preformatted for IANA by the Language Subtag Reviewer.



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   The initial registry will be created by the LTRU working group.
   Using the instructions in this document, the working group will
   prepare an Informational RFC by creating a series of Internet-Drafts
   containing the prototype registry according to the rules in Sections
   4.2.2 and 4.2.3 and subject to IESG review as described in Section
   6.1.1 of [RFC2026].

   When the Internet-Draft containing the prototype registry has been
   approved by the IESG for publication as an RFC, the document will be
   forwarded to IANA, which will post the contents of the new registry
   on-line.

   Tags in the RFC 3066 registry that are not deprecated that consist
   entirely of subtags that are defined by this document and which have
   the correct form and format for tags defined by this document are
   superseded by this document.  Such tags MUST be placed in records of
   type 'redundant' in the registry.  For example, "zh-Hant" is now
   defined by this document because 'zh' is an ISO 639-1 code and 'Hant'
   is an ISO 15924 code and both are defined in the registry.

   Tags in the RFC 3066 registry  that contain one or more subtags that
   do not match the valid registration pattern or which are not
   otherwise defined by this document MUST have records of type
   'grandfathered' created in the registry.  These records cannot become
   type 'redundant' except by revision of this document, but MAY have a
   'Deprecated' and 'Preferred-Value' field added to them if a subtag
   assignment or combination of assignments renders the tag obsolete.

   Tags in the RFC 3066 registry that have a notation that they are
   deprecated MUST be maintained as grandfathered entries.  The record
   for the grandfathered entry MUST contain a 'Deprecated' field with
   the most appropriate date that can be determined for when the RFC
   3066 record was deprecated.  The 'Comments' field SHOULD contain the
   reason for the deprecation.  The 'Preferred-Value' field MAY contain
   a tag that replaces the value.  For example, the tag "art-lojban" is
   deprecated and will be placed in the grandfathered section.  It's
   'Deprecated' field will contain the deprecation date (in this case
   "2003-09-02") and the 'Preferred-Value' field the value "jbo".

   The remaining tags in the RFC 3066 registry are not deprecated, have
   a format consistent with language tags as defined by this document,
   but contain subtags which are not defined by ISO 639, ISO 15924, or
   ISO 3166.  These subtags are consistent with registration as
   variants.  The initial registry SHALL contain appropriate variant
   records for the following subtags, and registered RFC 3066 tags
   containing these subtags MUST be entered into the initial registry as
   type 'redundant':




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      1901 (use with Prefix: de)

      1996 (use with Prefix: de)

      nedis (use with Prefix: sl)

      rozaj (use with Prefix: sl)

   All remaining RFC 3066 registered tags MUST be entered into the
   initial registry in records of type 'grandfathered'.  Interested
   parties MAY use the registration process in Section 3.4 in an attempt
   to register the variant subtags not already present in the registry.
   If all of the subtags in the original tag become fully defined by the
   resulting registrations, then the original tag is superseded by this
   document.  Such tags MUST have their record changed from type
   'grandfathered' to type 'redundant' in the registry.  Note that
   previous approval of a tag under RFC 3066 is no guarantee of approval
   of a variant subtag under this document.  The existing RFC 3066 tag
   maintains its validity, but the original reason for its registration
   might have become obsolete.  For example, the subtag 'boont' could be
   registered, resulting in the change of the grandfathered tag "en-
   boont" to type redundant in the registry.

   There MUST be a reasonable period in which the community can comment
   on the proposed list entries, which SHALL be no less than four weeks
   in length.  At the completion of this period, the chair(s) will
   notify iana@iana.org and the ltru and ietf-languages mail lists that
   the task is complete and forward the necessary materials to IANA for
   publication.

   Registrations that are in process under the rules defined in RFC 3066
   MAY be completed under the former rules, at the discretion of the
   language tag reviewer.  Any new registrations submitted after the
   request for conversion of the registry MUST be rejected.  New
   registrations completed under RFC 3066 SHALL be entered into the
   initial registry using the rules defined just above.

   All existing RFC 3066 language tag registrations will be maintained
   in perpetuity.

   Users of tags that are grandfathered SHOULD consider registering
   appropriate subtags in the IANA subtag registry (but are NOT REQUIRED
   to).

   UN numeric codes assigned to 'macro-geographical (continental)' MUST
   be defined in the IANA registry and made valid for use in language
   tags.  These codes MUST be added to the initial version of the
   registry.  The UN numeric codes for 'economic groupings' or 'other



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   groupings', and the alphanumeric codes in Appendix X of the UN
   document MUST NOT be added to the registry.  The UN numeric codes for
   countries or areas not associated with an assigned ISO 3166 alpha-2
   code MUST NOT be added to the initial version of the registry.  These
   values MAY be registered by individuals using the process defined in
   Section 3.4 and according to the rules in Section 3.3.

   When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49
   codes, the following criteria SHALL be applied to the inclusion,
   preferred value, and deprecation of codes:

   For each standard, the date of the standard referenced in RFC 1766 is
   selected as the starting date.  Codes that were valid on that date in
   the selected standard are added to the registry.  Codes that were
   previously assigned by but which were vacated or withdrawn before
   that date are not added to the registry.  For each successive change
   to the standard, any additional assignments are added to the
   registry.  Values that are withdrawn are marked as deprecated, but
   not removed.  Changes in meaning or assignment of a subtag are
   permitted during this process (for example, the ISO 3166 code 'CS'
   was originally assigned to 'Czechoslovakia' and is now assigned to
   'Serbia and Montenegro').  This continues up to the date that this
   document was adopted.  The resulting set of records is added to the
   registry.  Future changes or additions to this portion of the
   registry are governed by the provisions of this document.


























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4.  Formation and Processing of Language Tags

   This section addresses how to use the information in the registry
   with the tag syntax to choose, form and process language tags.

4.1  Choice of Language Tag

   One is sometimes faced with the choice between several possible tags
   for the same body of text.

   Interoperability is best served when all users use the same language
   tag in order to represent the same language.  If an application has
   requirements that make the rules here inapplicable, then that
   application risks damaging interoperability.  It is strongly
   RECOMMENDED that users not define their own rules for language tag
   choice.

   Subtags SHOULD only be used  where they add useful distinguishing
   information; extraneous subtags interfere with the meaning,
   understanding, and processing of language tags.  In particular, users
   and implementations SHOULD follow the 'Prefix' and 'Suppress-Script'
   fields in the registry (defined in Section 3.1): these fields provide
   guidance on when specific additional subtags SHOULD (and SHOULD NOT)
   be used in a language tag.

   Of particular note, many applications can benefit from the use of
   script subtags in language tags, as long as the use is consistent for
   a given context.  Script subtags were not formally defined in RFC
   3066 and their use can affect matching and subtag identification by
   implementations of RFC 3066, as these subtags appear between the
   primary language and region subtags.  For example, if a user requests
   content in an implementation of Section 2.5 of [RFC3066] using the
   language range "en-US", content labeled "en-Latn-US" will not match
   the request.  Therefore it is important to know when script subtags
   will customarily be used and when they ought not be used.  In the
   registry, the Suppress-Script field helps ensure greater
   compatibility between the language tags generated according to the
   rules in this document and language tags and tag processors or
   consumers based on RFC 3066 by defining when users SHOULD NOT include
   a script subtag with a particular primary language subtag.

   Extended language subtags (type 'extlang' in the registry, see
   Section 3.1) also appear between the primary language and region
   subtags and are reserved for future standardization.  Applications
   might benefit from their judicious use in forming language tags in
   the future.  Similar recommendations are expected to apply to their
   use as apply to script subtags.




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   Standards, protocols and applications that reference this document
   normatively but apply different rules to the ones given in this
   section MUST specify how the procedure varies from the one given
   here.

   The choice of subtags used to form a language tag SHOULD be guided by
   the following rules:

   1.  Use as precise a tag as possible, but no more specific than is
       justified.  Avoid using subtags that are not important for
       distinguishing content in an application.

       *  For example, 'de' might suffice for tagging an email written
          in German, while "de-CH-1996" is probably unnecessarily
          precise for such a task.

   2.  The script subtag SHOULD NOT be used to form language tags unless
       the script adds some distinguishing information to the tag.  The
       field 'Suppress-Script' in the primary language record in the
       registry indicates which script subtags do not add distinguishing
       information for most applications.

       *  For example, the subtag 'Latn' should not be used with the
          primary language 'en' because nearly all English documents are
          written in the Latin script and it adds no distinguishing
          information.  However, if a document were written in English
          mixing Latin script with another script such as Braille
          ('Brai'), then it might be appropriate to choose to indicate
          both scripts to aid in content selection, such as the
          application of a stylesheet.

   3.  If a tag or subtag has a 'Preferred-Value' field in its registry
       entry, then the  value of that field SHOULD be used to form the
       language tag in preference to the tag or subtag in which the
       preferred value appears.

       *  For example, use 'he' for Hebrew in preference to 'iw'.

   4.  The 'und' (Undetermined) primary language subtag SHOULD NOT be
       used to label content, even if the language is unknown.  Omitting
       the language tag altogether is preferred to using a tag with a
       primary language subtag of 'und'.  The 'und' subtag MAY be useful
       for protocols that require a language tag to be provided.  The
       'und' subtag MAY also be useful when matching language tags in
       certain situations.

   5.  The 'mul' (Multiple) primary language subtag SHOULD NOT be used
       whenever the protocol allows the separate tags for multiple



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       languages, as is the case for the Content-Language header in
       HTTP.  The 'mul' subtag conveys little useful information:
       content in multiple languages SHOULD individually tag the
       languages where they appear or otherwise indicate the actual
       language in preference to the 'mul' subtag.

   6.  The same variant subtag SHOULD NOT be used more than once within
       a language tag.

       *  For example, do not use "de-DE-1901-1901".

   To ensure consistent backward compatibility, this document contains
   several provisions to account for potential instability in the
   standards used to define the subtags that make up language tags.
   These provisions mean that no language tag created under the rules in
   this document will become obsolete.

4.2  Meaning of the Language Tag

   The relationship between the tag and the information it relates to is
   defined by the the context in which the tag appears.  Accordingly,
   this section can only give possible examples of its usage.

   o  For a single information object, the associated language tags
      might be interpreted as the set of languages that is necessary for
      a complete comprehension of the complete object.  Example: Plain
      text documents.

   o  For an aggregation of information objects, the associated language
      tags could be taken as the set of languages used inside components
      of that aggregation.  Examples: Document stores and libraries.

   o  For information objects whose purpose is to provide alternatives,
      the associated language tags could be regarded as a hint that the
      content is provided in several languages, and that one has to
      inspect each of the alternatives in order to find its language or
      languages.  In this case, the presence of multiple tags might not
      mean that one needs to be multi-lingual to get complete
      understanding of the document.  Example: MIME multipart/
      alternative.

   o  In markup languages, such as HTML and XML, language information
      can be added to each part of the document identified by the markup
      structure (including the whole document itself).  For example, one
      could write <span lang="fr">C'est la vie.</span> inside a
      Norwegian document; the Norwegian-speaking user could then access
      a French-Norwegian dictionary to find out what the marked section
      meant.  If the user were listening to that document through a



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      speech synthesis interface, this formation could be used to signal
      the synthesizer to appropriately apply French text-to-speech
      pronunciation rules to that span of text, instead of applying the
      inappropriate Norwegian rules.

   Language tags are related when they contain a similar sequence of
   subtags.  For example, if a language tag B contains language tag A as
   a prefix, then B is typically "narrower" or "more specific" than A.
   Thus "zh-Hant-TW" is more specific than "zh-Hant".

   This relationship is not guaranteed in all cases: specifically,
   languages that begin with the same sequence of subtags are NOT
   guaranteed to be mutually intelligible, although they might be.  For
   example, the tag "az" shares a prefix with both "az-Latn"
   (Azerbaijani written using the Latin script) and "az-Cyrl"
   (Azerbaijani written using the Cyrillic script).  A person fluent in
   one script might not be able to read the other, even though the text
   might be identical.  Content tagged as "az" most probably is written
   in just one script and thus might not be intelligible to a reader
   familiar with the other script.

4.3  Length Considerations

   [RFC3066] did not provide an upper limit on the size of language
   tags.  While RFC 3066 did define the semantics of particular subtags
   in such a way that most language tags consisted of language and
   region subtags with a combined total length of up to six characters,
   larger registered tags were not only possible but were actually
   registered.

   Neither the language tag syntax nor other requirements in this
   document  impose a fixed upper limit on the number of subtags in a
   language tag (and thus an upper bound on the size of a tag).  The
   language tag syntax suggests that, depending on the specific
   language, more subtags (and thus a longer tag) are sometimes
   necessary to completely identify the language for certain
   applications; thus it is possible to envision long or complex subtag
   sequences.

4.3.1  Working with Limited Buffer Sizes

   Some applications and protocols are forced to allocate fixed buffer
   sizes or otherwise limit the length of a language tag.  A conformant
   implementation or specification MAY refuse to support the storage of
   language tags which exceed a specified length.  Any such limitation
   SHOULD be clearly documented, and such documentation SHOULD include
   what happens to longer tags (for example, whether an error value is
   generated or the language tag is truncated).  A protocol that allows



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   tags to be truncated at an arbitrary limit, without giving any
   indication of what that limit is, has the potential for causing harm
   by changing the meaning of tags in substantial ways.

   In practice, most language tags do not require more than a few
   subtags and will not approach reasonably sized buffer limitations:
   see Section 4.1.

   Some specifications or protocols have limits on tag length but do not
   have a fixed length limitation.  For example, [RFC2231]  has no
   explicit length limitation: the length available for the language tag
   is constrained by the length of other header components (such as the
   charset's name) coupled with the 76 character limit in [RFC2047].
   Thus the "limit" might be 50 or more characters, but it could
   potentially be quite small.

   The considerations for assigning a buffer limit are:

      Implementations SHOULD NOT truncate language tags unless the
      meaning of the tag is purposefully being changed, or unless the
      tag does not fit into a limited buffer size specified by a
      protocol for storage or transmission.

      Implementations SHOULD warn the user when a tag is truncated since
      truncation changes the semantic meaning of the tag.

      Implementations of protocols or specifications that are space
      constrained but do not have a fixed limit SHOULD use the longest
      possible tag in preference to truncation.

      Protocols or specifications that specify limited buffer sizes for
      language tags MUST allow for language tags of up to 33 characters.

      Protocols or specifications that specify limited buffer sizes for
      language tags SHOULD allow for language tags of at least 42
      characters.

   The following illustration shows how the 42-character recommendation
   was derived.  The combination of language and extended language
   subtags was chosen for future compatibility.  At up to 15 characters,
   this combination is longer than the longest possible primary language
   subtag (8 characters):









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   language      =  3 (ISO 639-2; ISO 639-1 requires 2)
   extlang1      =  4 (each subsequent subtag includes '-')
   extlang2      =  4 (unlikely: needs prefix="language-extlang1")
   extlang3      =  4 (extremely unlikely)
   script        =  5 (if not suppressed: see Section 4.1)
   region        =  4 (UN M.49; ISO 3166 requires 3)
   variant1      =  9 (MUST have language as a prefix)
   variant2      =  9 (MUST have language-variant1 as a prefix)

   total         = 42 characters

              Figure 7: Derivation of the Limit on Tag Length


4.3.2  Truncation of Language Tags

   Truncation of a language tag alters the meaning of the tag, and thus
   SHOULD be avoided.  However, truncation of language tags is sometimes
   necessary due to limited buffer sizes.  Such truncation MUST NOT
   permit a subtag to be chopped off in the middle or the formation of
   invalid tags (for example, one ending with the "-" character).

   This means that applications or protocols which truncate tags MUST do
   so by progressively removing subtags along with their preceding "-"
   from the right side of the language tag until the tag is short enough
   for the given buffer.  If the resulting tag ends with a single-
   character subtag, that subtag and its preceding "-" MUST also be
   removed.  For example:

   Tag to truncate: zh-Hant-CN-variant1-a-extend1-x-wadegile-private1
   1. zh-Latn-CN-variant1-a-extend1-x-wadegile
   2. zh-Latn-CN-variant1-a-extend1
   3. zh-Latn-CN-variant1
   4. zh-Latn-CN
   5. zh-Latn
   6. zh

                    Figure 8: Example of Tag Truncation


4.4  Canonicalization of Language Tags

   Since a particular language tag is sometimes used by many processes,
   language tags SHOULD always be created or generated in a canonical
   form.

   A language tag is in canonical form when:




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   1.  The tag is well-formed according the rules in Section 2.1 and
       Section 2.2.

   2.  Subtags of type 'Region' that have a Preferred-Value mapping in
       the IANA registry (see Section 3.1) SHOULD be replaced with their
       mapped value.

   3.  Redundant or grandfathered tags that have a Preferred-Value
       mapping in the IANA registry (see Section 3.1) MUST be replaced
       with their mapped value.  These items are either deprecated
       mappings created before the adoption of this document (such as
       the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are
       the result of later registrations or additions to this document
       (for example, "zh-guoyu" might be mapped to a language-extlang
       combination such as "zh-cmn" by some future update of this
       document).

   4.  Other subtags that have a Preferred-Value mapping in the IANA
       registry (see Section 3.1) MUST be replaced with their mapped
       value.  These items consist entirely of clerical corrections to
       ISO 639-1 in which the deprecated subtags have been maintained
       for compatibility purposes.

   5.  If more than one extension subtag sequence exists, the extension
       sequences are ordered into case-insensitive ASCII order by
       singleton subtag.

   Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical
   form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in
   canonical form.

   Example: The language tag "en-NH" (English as used in the New
   Hebrides) is not canonical because the 'NH' subtag has a canonical
   mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its
   validity.

   Canonicalization of language tags does not imply anything about the
   use of upper or lowercase letters when processing or comparing
   subtags (and as described in Section 2.1).  All comparisons MUST be
   performed in a case-insensitive manner.

   When performing canonicalization of language tags, processors MAY
   regularize the case of the subtags (that is, this process is
   OPTIONAL), following the case used in the registry.  Note that this
   corresponds to the following casing rules: uppercase all non-initial
   two-letter subtags; titlecase all non-initial four-letter subtags;
   lowercase everything else.




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   Note: Case folding of ASCII letters in certain locales, unless
   carefully handled, sometimes produces non-ASCII character values.
   The Unicode Character Database file "SpecialCasing.txt" defines the
   specific cases that are known to cause problems with this.  In
   particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is
   uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE).
   Implementers SHOULD specify a locale-neutral casing operation to
   ensure that case folding of subtags does not produce this value,
   which is illegal in language tags.  For example, if one were to
   uppercase the region subtag 'in' using Turkish locale rules, the
   sequence U+0130 U+004E would result instead of the expected 'IN'.

   Note: if the field 'Deprecated' appears in a registry record without
   an accompanying 'Preferred-Value' field, then that tag or subtag is
   deprecated without a replacement.  Validating processors SHOULD NOT
   generate tags that include these values, although the values are
   canonical when they appear in a language tag.

   An extension MUST define any relationships that exist between the
   various subtags in the extension and thus MAY define an alternate
   canonicalization scheme for the extension's subtags.  Extensions MAY
   define how the order of the extension's subtags are interpreted.  For
   example, an extension could define that its subtags are in canonical
   order when the subtags are placed into ASCII order: that is, "en-a-
   aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa".  Another extension might
   define that the order of the subtags influences their semantic
   meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b-
   aaa-bbb-ccc").  However, extension specifications SHOULD be designed
   so that they are tolerant of the typical processes described in
   Section 3.6.

4.5  Considerations for Private Use Subtags

   Private-use subtags require private agreement between the parties
   that intend to use or exchange language tags that use them and great
   caution SHOULD be used in employing them in content or protocols
   intended for general use.  Private-use subtags are simply useless for
   information exchange without prior arrangement.

   The value and semantic meaning of private-use tags and of the subtags
   used within such a language tag are not defined by this document.

   The use of subtags defined in the IANA registry as having a specific
   private use meaning convey more information that a purely private use
   tag prefixed by the singleton subtag 'x'.  For applications this
   additional information MAY be useful.

   For example, the region subtags 'AA', 'ZZ' and in the ranges



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   'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY
   be used to form a language tag.  A tag such as "zh-Hans-XQ" conveys a
   great deal of public, interchangeable information about the language
   material (that it is Chinese in the simplified Chinese script and is
   suitable for some geographic region 'XQ').  While the precise
   geographic region is not known outside of private agreement, the tag
   conveys far more information than an opaque tag such as "x-someLang",
   which contains no information about the language subtag or script
   subtag outside of the private agreement.

   However, in some cases content tagged with private use subtags MAY
   interact with other systems in a different and possibly unsuitable
   manner compared to tags that use opaque, privately defined subtags,
   so the choice of the best approach sometimes depends on the
   particular domain in question.




































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5.  IANA Considerations

   This section deals with the processes and requirements necessary for
   IANA to undertake to maintain the subtag and extension registries as
   defined by this document and in accordance with the requirements of
   [RFC2434].

   The impact on the IANA maintainers of the two registries defined by
   this document will be a small increase in the frequency of new
   entries or updates.

   Upon adoption of this document, the process described in Section 3.7
   will be used to generate the initial Language Subtag Registry.  The
   initial set of records represents no impact on IANA, since the work
   to create it will be performed externally (as defined in that
   section).  The new registry will be listed under "Language Tags" at
   <http://www.iana.org/numbers.html>.  The existing directory of
   registration forms and RFC 3066 registrations will be relabeled as
   "Language Tags (Obsolete)" and maintained (but not added to or
   modified).

   Future work on the Language Subtag Registry will be limited to
   inserting or replacing whole records preformatted for IANA by the
   Language Subtag Reviewer as described in Section 3.2 of this
   document.  Each record will be sent to iana@iana.org with a subject
   line indicating whether the enclosed record is an insertion (of a new
   record) or a replacement of an existing record which has a Type and
   Subtag (or Tag) field that exactly matches the record sent.  Records
   cannot be deleted from the registry.

   The Language Tag Extensions registry will also be generated and sent
   to IANA as described in Section 3.6.  This registry can contain at
   most 35 records and thus changes to this registry are expected to be
   very infrequent.

   Future work by IANA on the Language Tag Extensions Registry is
   limited to two cases.  First, the IESG MAY request that new records
   be inserted into this registry from time to time.  These requests
   will include the record to insert in the exact format described in
   Section 3.6.  In addition, there MAY be occasional requests from the
   maintaining authority for a specific extension to update the contact
   information or URLs in the record.  These requests MUST include the
   complete, updated record.  IANA is not responsible for validating the
   information provided, only that it is properly formatted.  It should
   reasonably be seen to come from the maintaining authority named in
   the record present in the registry.





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6.  Security Considerations

   Language tags used in content negotiation, like any other information
   exchanged on the Internet, might be a source of concern because they
   might be used to infer the nationality of the sender, and thus
   identify potential targets for surveillance.

   This is a special case of the general problem that anything sent is
   visible to the receiving party and possibly to third parties as well.
   It is useful to be aware that such concerns can exist in some cases.

   The evaluation of the exact magnitude of the threat, and any possible
   countermeasures, is left to each application protocol (see BCP 72
   [RFC3552] for best current practice guidance on security threats and
   defenses).

   The language tag associated with a particular information item is of
   no consequence whatsoever in determining whether that content might
   contain possible homographs.  The fact that a text is tagged as being
   in one language or using a particular script subtag provides no
   assurance whatsoever that it does not contain characters from scripts
   other than the one(s) associated with or specified by that language
   tag.

   Since there is no limit to the number of variant, private use, and
   extension subtags, and consequently no limit on the possible length
   of a tag, implementations need to guard against buffer overflow
   attacks.  See Section 4.3 for details on language tag truncation,
   which can occur as a consequence of defenses against buffer overflow.

   Although the specification of valid subtags for an extension (see:
   Section 3.6) MUST be available over the Internet, implementations
   SHOULD NOT mechanically depend on it being always accessible, to
   prevent denial-of-service attacks.

















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7.  Character Set Considerations

   The syntax in this document requires that language tags use only the
   characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most
   character sets, so the composition of language tags should not have
   any character set issues.

   Rendering of characters based on the content of a language tag is not
   addressed in this memo.  Historically, some languages have relied on
   the use of specific character sets or other information in order to
   infer how a specific character should be rendered (notably this
   applies to language and culture specific variations of Han ideographs
   as used in Japanese, Chinese, and Korean).  When language tags are
   applied to spans of text, rendering engines can use that information
   in deciding which font to use in the absence of other information,
   particularly where languages with distinct writing traditions use the
   same characters.


































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8.  Changes from RFC 3066

   The main goals for this revision of language tags were the following:

   *Compatibility.* All valid RFC 3066 language tags  (including those
   in the IANA registry)  remain valid in this specification.  Thus
   there is complete backward compatibility of this specification with
   existing content.  In addition, this document defines language tags
   in such as way as to ensure future compatibility, and processors
   based solely on the RFC 3066 ABNF (such as those described in
   [XMLSchema]) will be able to process tags described by this document.

   *Stability.* Because of the changes in underlying ISO standards, a
   valid RFC 3066 language tag may become invalid (or have its meaning
   change) at a later date.  With so much of the world's computing
   infrastructure dependent on language tags, this is simply
   unacceptable: it invalidates content that may have an extensive
   shelf-life.  In this specification, once a language tag is valid, it
   remains valid forever.  Previously, there was no way to determine
   when two tags were equivalent.  This specification provides a stable
   mechanism for doing so, through the use of canonical forms.  These
   are also stable, so that implementations can depend on the use of
   canonical forms to assess equivalency.

   *Validity.*  The structure of language tags defined by this document
   makes it possible to determine if a particular tag is well-formed
   without regard for the actual content or "meaning" of the tag as a
   whole.  This is important because the registry and underlying
   standards  change over time.  In addition, it must be possible to
   determine if a tag is valid (or not) for a given point in time in
   order  to provide reproducible, testable results.  This process must
   not be error-prone; otherwise even intelligent people will generate
   implementations that give different results.  This specification
   provides for that by having a single data file, with specific
   versioning information, so that the validity of language tags at any
   point in time can be precisely determined (instead of interpolating
   values from many separate sources).

   *Extensibility.* It is important to be able to differentiate between
   written forms of language -- for many implementations this is more
   important than distinguishing between spoken variants of a language.
   Languages are written in a wide variety of different scripts, so this
   document provides for the generative use of ISO 15924 script codes.
   Like the generative use of ISO language and country codes in RFC
   3066, this allows combinations to be produced without resorting to
   the registration process.  The addition of UN codes provides for the
   generation of language tags with regional scope, which is also
   required for information technology.



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   The recast of the registry from containing whole language tags to
   subtags is a key part of this.  An important feature of RFC 3066 was
   that it allowed generative use of subtags.  This allows people to
   meaningfully use generated tags, without the delays in registering
   whole tags, and the burden on the registry of having to supply all of
   the combinations that people may find useful.

   Because of the widespread use of language tags, it is potentially
   disruptive to have periodic revisions of the core specification,
   despite demonstrated need.  The extension mechanism provides for a
   way for independent RFCs to define extensions to language tags.
   These extensions have a very constrained, well-defined structure to
   prevent extensions from interfering with implementations of language
   tags defined in this document.  The document also anticipates
   features of ISO 639-3 with the addition of the extended language
   subtags, as well as the possibility of other ISO 639 parts becoming
   useful for the formation of language tags in the future.  The use and
   definition of private use tags has also been modified, to allow
   people to move as much information as possible out of private use
   tags, and into the regular structure.  The goal is to dramatically
   reduce the need to produce a revision of this document in the future.

   The specific changes in this document to meet these goals are:

   o  Defines the ABNF and rules for subtags so that the category of all
      subtags can be determined without reference to the registry.

   o  Adds the concept of well-formed vs. validating processors,
      defining the rules by which an implementation can claim to be one
      or the other.

   o  Replaces the IANA language tag registry with a language subtag
      registry that provides a complete list of valid subtags in the
      IANA registry.  This allows for robust implementation and ease of
      maintenance.  The language subtag registry becomes the canonical
      source for forming language tags.

   o  Provides a process that guarantees stability of language tags, by
      handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in
      the event that they register a previously used value for a new
      purpose.

   o  Allows ISO 15924 script code subtags and allows them to be used
      generatively.  Defines a method for indicating in the registry
      when script subtags are necessary for a given language tag.

   o  Adds the concept of a variant subtag and allows variants to be
      used generatively.



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   o  Adds the ability to use a class of UN M.49 tags for  supra-
      national regions and to resolve conflicts in the assignment of ISO
      3166 codes.

   o  Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166
      as the mechanism for creating private-use language, script, and
      region subtags respectively.

   o  Adds a well-defined extension mechanism.

   o  Defines an extended language subtag, possibly for use with certain
      anticipated features of ISO 639-3.

   Ed Note: The following items are provided for the convenience of
   reviewers and will be removed from the final document.

   Changes between draft-ietf-ltru-registry-05 and this version are:

   o  Changes to the initial population rules to pre-register four
      subtags.  This included changing all the variant examples to use
      just those four subtags (nedis, rozaj, 1996, and 1901) in
      appropriate ways.  It also includes substandtial wordsmithing of
      the rules on handling RFC 3066 grandfathered/redundant
      registrations (A.Phillips)

   o  Rewrote the introduction to use "tag" instead of many (long,
      convoluted) synonyms and to generally simplify the text. (thread
      of #944) (M.Duerst, A.Phillips)

   o  Added an introduction to Section 2 (moved from Section 4.2).
      (M.Duerst)

   o  Reorganized the resulting Section 4.2.

   o  Divided Section 4.3 by added two subsections, moving paragraphs to
      fit into the proper sub-section.  Made the actual requirements
      into a list so that they would be very visible.  (I.McDonald)

   o  Added the processing instruction symrefs='yes' (F.Ellermann)

   o  Moved Length Considerations from Section 2.1 to Section 4.3.  Some
      text was moved or reorganized as a result and a small change was
      made in Section 4.1 (Choice) to ensure that no information was
      lost.  (A.Phillips)

   o  Added a small description of each subtag type to the sub-section
      on each subtag in Section 2.1.  (F.Charles)




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   o  Modified the restriction on using extended language subtags in
      Section 2.2.2 so that it is clearer.  (J.Cowan)

















































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9.  References

9.1  Normative References

   [ISO639-1]
              International Organization for Standardization, "ISO 639-
              1:2002, Codes for the representation of names of languages
              -- Part 1: Alpha-2 code", ISO Standard 639, 2002, <ISO
              639-1>.

   [ISO639-2]
              International Organization for Standardization, "ISO 639-
              2:1998 - Codes for the representation of names of
              languages -- Part 2: Alpha-3 code - edition 1",
              August 1988, <ISO 639-2>.

   [ISO15924]
              ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the
              representation of names of scripts", January 2004, <ISO
              15924>.

   [ISO3166]  International Organization for Standardization, "Codes for
              the representation of names of countries, 3rd edition",
              ISO Standard 3166, August 1988, <ISO 3166>.

   [UN_M.49]  Statistical Division, United Nations, "Standard Country or
              Area Codes for Statistical Use", UN Standard Country or
              Area Codes for Statistical Use, Revision 4 (United Nations
              publication, Sales No. 98.XVII.9, June 1999, <UN M.49>.

   [ISO10646]
              International Organization for Standardization, "ISO/IEC
              10646-1:2000. Information technology -- Universal
              Multiple-Octet Coded Character Set (UCS) -- Part 1:
              Architecture and Basic Multilingual Plane and ISO/IEC
              10646-2:2001. Information technology -- Universal
              Multiple-Octet Coded Character Set (UCS) -- Part 2:
              Supplementary Planes, as, from time to time, amended,
              replaced by a new edition or expanded by the addition of
              new parts", 2000, <ISO/IEC 10646>.

   [RFC2234bis]
              Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00
              (work in progress), March 2005.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.



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   [RFC2028]  Hovey, R. and S. Bradner, "The Organizations Involved in
              the IETF Standards Process", BCP 11, RFC 2028,
              October 1996.

   [RFC2047]  Moore, K., "MIME (Multipurpose Internet Mail Extensions)
              Part Three: Message Header Extensions for Non-ASCII Text",
              RFC 2047, November 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2781]  Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO
              10646", RFC 2781, February 2000.

   [RFC2860]  Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
              Understanding Concerning the Technical Work of the
              Internet Assigned Numbers Authority", RFC 2860, June 2000.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, July 2002.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              July 2003.

9.2  Informative References

   [iso639.principles]
              ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory
              Committee:  Working principles for ISO 639 maintenance",
              March 2000,
              <http://www.loc.gov/standards/iso639-2/
              iso639jac_n3r.html>.

   [record-jar]
              Raymond, E., "The Art of Unix Programming", 2003.

   [XML10]    Bray (et al), T., "Extensible Markup Language (XML) 1.0",
              02 2004.

   [XMLSchema]
              Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2:
              Datatypes Second Edition", 10 2004, <
              http://www.w3.org/TR/xmlschema-2/>.



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   [Unicode]  Unicode Consortium, "The Unicode Consortium. The Unicode
              Standard, Version 4.1.0, defined by: The Unicode Standard,
              Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-
              18578-1), as amended by Unicode 4.0.1
              (http://www.unicode.org/versions/Unicode4.0.1) and by
              Unicode 4.1.0
              (http://www.unicode.org/versions/Unicode4.1.0).",
              March 2005.

   [RFC1766]  Alvestrand, H., "Tags for the Identification of
              Languages", RFC 1766, March 1995.

   [RFC2231]  Freed, N. and K. Moore, "MIME Parameter Value and Encoded
              Word Extensions: Character Sets, Languages, and
              Continuations", RFC 2231, November 1997.

   [RFC3066]  Alvestrand, H., "Tags for the Identification of
              Languages", BCP 47, RFC 3066, January 2001.


Authors' Addresses

   Addison Phillips (editor)
   Quest Software

   Email: addison.phillips@quest.com


   Mark Davis (editor)
   IBM

   Email: mark.davis@us.ibm.com



















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Appendix A.  Acknowledgements

   Any list of contributors is bound to be incomplete; please regard the
   following as only a selection from the group of people who have
   contributed to make this document what it is today.

   The contributors to RFC 3066 and RFC 1766, the precursors of this
   document, made enormous contributions directly or indirectly to this
   document and are generally responsible for the success of language
   tags.

   The following people (in alphabetical order) contributed to this
   document or to RFCs 1766 and 3066:

   Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet,
   Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco
   Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable,
   John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank
   Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk-
   Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold,
   Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent
   Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald,
   Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George
   Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto
   Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois
   Yergeau and many, many others.

   Very special thanks must go to Harald Tveit Alvestrand, who
   originated RFCs 1766 and 3066, and without whom this document would
   not have been possible.  Special thanks must go to Michael Everson,
   who has served as language tag reviewer for almost the complete
   period since the publication of RFC 1766.  Special thanks to Doug
   Ewell, for his production of the first complete subtag registry, and
   his work in producing a test parser for verifying language tags.

















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Appendix B.  Examples of Language Tags (Informative)

   Simple language subtag:

      de (German)

      fr (French)

      ja (Japanese)

      i-enochian (example of a grandfathered tag)

   Language subtag plus Script subtag:

      zh-Hant (Chinese written using the Traditional Chinese script)

      zh-Hans (Chinese written using the Simplified Chinese script)

      sr-Cyrl (Serbian written using the  Cyrillic script)

      sr-Latn (Serbian written using the Latin script)

   Language-Script-Region:

      zh-Hans-CN (Chinese written using the Simplified script as used in
      mainland China)

      sr-Latn-CS (Serbian written using the Latin script as used in
      Serbia and Montenegro)

   Language-Variant:

      sl-rozaj (Resian dialect of Slovenian

      sl-nedis (Nadiza dialect of Slovenian)

   Language-Region-Variant:

      de-CH-1901 (German as used in Switzerland using the 1901 variant
      [othography])

      sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect)

   Language-Script-Region-Variant:







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      sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the
      Latin script as used in Italy.  Note that this tag is NOT
      RECOMMENDED because subtag 'sl' has a Suppress-Script value of
      'Latn')

   Language-Region:

      de-DE (German for Germany)

      en-US (English as used in the United States)

      es-419 (Spanish for Latin America and Caribbean region using the
      UN region code)

   Private-use subtags:

      de-CH-x-phonebk

      az-Arab-x-AZE-derbend

   Extended language subtags (examples ONLY: extended languages MUST be
   defined by revision or update to this document):

      zh-min

      zh-min-nan-Hant-CN

   Private-use registry values:

      x-whatever (private use using the singleton 'x')

      qaa-Qaaa-QM-x-southern (all private tags)

      de-Qaaa (German, with a private script)

      sr-Latn-QM (Serbian, Latin-script, private region)

      sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro)

   Tags that use extensions (examples ONLY: extensions MUST be defined
   by revision or update to this document or by RFC):

      en-US-u-islamCal

      zh-CN-a-myExt-x-private






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      en-a-myExt-b-another

   Some Invalid Tags:

      de-419-DE (two region tags)

      a-DE (use of a single character subtag in primary position; note
      that there are a few grandfathered tags that start with "i-" that
      are valid)

      ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter
      prefix)







































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Appendix C.  Example Registry

   Example Registry

   File-Date: 2005-04-18
   %%
   Type: language
   Subtag: aa
   Description: Afar
   Added: 2004-07-06
   %%
   Type: language
   Subtag: ab
   Description: Abkhazian
   Added: 2004-07-06
   %%
   Type: language
   Subtag: ae
   Description: Avestan
   Added: 2004-07-06
   %%
   Type: language
   Subtag: ar
   Description: Arabic
   Added: 2004-07-06
   Suppress-Script: Arab
   Comment: Arabic text is usually written in Arabic script
   %%
   Type: language
   Subtag: qaa..qtz
   Description: PRIVATE USE
   Added: 2004-08-01
   Comment: Use private use codes in preference
     to the x- singleton for primary language
   Comment: This is an example of two comments.
   %%
   Type: script
   Subtag: Arab
   Description: Arabic
   Added: 2004-07-06
   %%
   Type: script
   Subtag: Armn
   Description: Armenian
   Added: 2004-07-06
   %%
   Type: script
   Subtag: Bali



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   Description: Balinese
   Added: 2004-07-06
   %%
   Type: script
   Subtag: Batk
   Description: Batak
   Added: 2004-07-06
   %%
   Type: region
   Subtag: AA
   Description: PRIVATE USE
   Added: 2004-08-01
   %%
   Type: region
   Subtag: AD
   Description: Andorra
   Added: 2004-07-06
   %%
   Type: region
   Subtag: AE
   Description: United Arab Emirates
   Added: 2004-07-06
   %%
   Type: region
   Subtag: AX
   Description: &#xC5;land Islands
   Added: 2004-07-06
   Comments: The description shows a Unicode escape
     for the letter A-ring.
   %%
   Type: region
   Subtag: 001
   Description: World
   Added: 2004-07-06
   %%
   Type: region
   Subtag: 002
   Description: Africa
   Added: 2004-07-06
   %%
   Type: region
   Subtag: 003
   Description: North America
   Added: 2004-07-06
   %%
   Type: variant
   Subtag: 1901
   Description: Traditional German



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      orthography
   Added: 2004-09-09
   Prefix: de
   Comment: <shows continuation>
   %%
   Type: variant
   Subtag: nedis
   Description: Nadiza dialect
   Description: Natisone dialect
   Added: 2003-10-09
   Prefix: sl
   %%
   Type: grandfathered
   Tag: art-lojban
   Description: Lojban
   Added: 2001-11-11
   Canonical: jbo
   Deprecated: 2003-09-02
   %%
   Type: grandfathered
   Tag: en-GB-oed
   Description: English, Oxford English Dictionary spelling
   Added: 2003-07-09
   %%
   Type: grandfathered
   Tag: i-ami
   Description: 'Amis
   Added: 1999-05-25
   %%
   Type: grandfathered
   Tag: i-bnn
   Description: Bunun
   Added: 1999-05-25
   %%
   Type: redundant
   Tag: az-Arab
   Description: Azerbaijani in Arabic script
   Added: 2003-05-30
   %%
   Type: redundant
   Tag: az-Cyrl
   Description: Azerbaijani in Cyrillic script
   Added: 2003-05-30
   %%

                 Figure 9: Example of the Registry Format





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Acknowledgment

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   Internet Society.




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