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Network Working Group                                   A. Phillips, Ed.
Internet-Draft                                          webMethods, Inc.
Expires: August 15, 2005                                        M. Davis
                                                                     IBM
                                                       February 14, 2005


                     Tags for Identifying Languages
                       draft-phillips-langtags-10

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
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   RFC 3668.

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   This Internet-Draft will expire on August 15, 2005.

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
       2.1.1  Length Considerations  . . . . . . . . . . . . . . . .   5
     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  . . . . . . . . . . . . . . . . . . . .   9
       2.2.4  Region Subtag  . . . . . . . . . . . . . . . . . . . .  10
       2.2.5  Variant Subtags  . . . . . . . . . . . . . . . . . . .  11
       2.2.6  Extension Subtags  . . . . . . . . . . . . . . . . . .  11
       2.2.7  Private Use Subtags  . . . . . . . . . . . . . . . . .  12
       2.2.8  Pre-Existing RFC 3066 Registrations  . . . . . . . . .  13
       2.2.9  Possibilities for Registration . . . . . . . . . . . .  13
       2.2.10   Classes of Conformance . . . . . . . . . . . . . . .  14
     2.3  Choice of Language Tag . . . . . . . . . . . . . . . . . .  15
     2.4  Meaning of the Language Tag  . . . . . . . . . . . . . . .  16
       2.4.1  Canonicalization of Language Tags  . . . . . . . . . .  17
     2.5  Considerations for Private Use Subtags . . . . . . . . . .  18
   3.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  20
     3.1  Format of the IANA Language Subtag Registry  . . . . . . .  20
     3.2  Stability of IANA Registry Entries . . . . . . . . . . . .  24
     3.3  Registration Procedure for Subtags . . . . . . . . . . . .  27
     3.4  Extensions and Extensions Namespace  . . . . . . . . . . .  29
   4.   Security Considerations  . . . . . . . . . . . . . . . . . .  32
   5.   Character Set Considerations . . . . . . . . . . . . . . . .  33
   6.   Changes from RFC 3066  . . . . . . . . . . . . . . . . . . .  34
   7.   References . . . . . . . . . . . . . . . . . . . . . . . . .  36
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  38
   A.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  39
   B.   Examples of Language Tags (Informative)  . . . . . . . . . .  40
   C.   Conversion of the RFC 3066 Language Tag Registry . . . . . .  42
        Intellectual Property and Copyright Statements . . . . . . .  45
















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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.

   Information about a user's language preferences commonly needs to be
   identified so that appropriate processing can be applied.  For
   example, the user's language preferences in a browser can be used to
   select web pages appropriately.  A choice of language preference 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 may be useful or even required by some
   types of information 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 a language identifier.  These identifiers
   can also be used to specify user preferences when selecting
   information content, or for labeling additional attributes of content
   and associated resources.

   These identifiers can also be used to indicate additional attributes
   of content that are closely related to the language.  In particular,
   it is often necessary to indicate specific information about the
   dialect, writing system, or orthography used in a document or
   resource, as these attributes may be important for the user to obtain
   information in a form that they can understand, or important in
   selecting appropriate processing resources for the given content.

   This document specifies an identifier mechanism and a registration
   function for values to be used with that identifier mechanism.  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 6.

   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 [RFC 2119] [11].








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2.  The Language Tag

2.1  Syntax

   The language tag is composed of one or more parts: A primary language
   subtag and a (possibly empty) series of subsequent subtags.  Subtags
   are distinguished by their length, position in the subtag sequence,
   and content, so that each type of subtag 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 specific subtag values are not recognized.  Thus a parser need not
   have an up-to-date copy of the registered subtag values to perform
   most searching and matching operations.

   The syntax of this tag in ABNF [RFC 2234] [13] is:

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

   lang            = 2*3ALPHA           ; 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         = ALPHA (4*7alphanum) ; registered variants
                   / DIGIT (3*7alphanum)
   extension       = singleton 1*("-" (2*8alphanum)) ; extension subtag(s)
   privateuse      = ("x"/"X") 1*("-" (1*8alphanum)) ; private use subtag(s)
   singleton       = ("a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z")
                   ; 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).  Note that there is a
   subtlety in the ABNF for 'variant': variants may consist of sequences



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   of up to eight characters.

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

   Note that although [RFC 2234] [13] 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
   that uses the Unicode UTF-16LE encoding.

   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 should not be taken
   to carry meaning.

   For example:
   o  [ISO 639] [1] recommends that language codes be written in lower
      case ('mn' Mongolian).
   o  [ISO 3166] [4] recommends that country codes be capitalized ('MN'
      Mongolia).
   o  [ISO 15924] [3] 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' (ABNF: %x41) through 'Z' (ABNF: %x5A) are
   considered equivalent and mapped directly to their US-ASCII lowercase
   equivalents in the range 'a' (ABNF: %x61) through 'z' (ABNF: %x7A).
   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.

   For informative examples of language tags, see Appendix B at the end
   of this document.

2.1.1  Length Considerations

   Although neither the ABNF nor other guidelines in this document
   provide a fixed upper limit on the number of size of subtags in a
   Language Tag and it is possible to envision quite long and complex
   subtag sequences, in practice these are rare because additional
   granularity in tags seldom adds useful distinguishing information and
   because longer, more granular tags interefere with the meaning,
   understanding, and processing of language tags.

   In particular,  variant subtags SHOULD be used only with their
   recommended prefix.  This limits most tags to a sequence of four



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   subtags (excluding any extensions or private use sequences).  See
   Section 2.3 for more information on selecting the most appropriate
   Language Tag.

   A conformant implementation need not support the storage of language
   tags which exceed a specified length.  For an example, see [RFC 2231]
   [12].  Any such a limitation MUST be clearly documented, and such
   documentation SHOULD include the disposition of any longer tags (for
   example, whether an error value is generated or the language tag is
   truncated).  If truncation is permitted it SHOULD NOT permit a subtag
   to be divided.

2.2  Language Subtag Sources and Interpretation

   The namespace of language tags and their subtags is administered by
   the Internet Assigned Numbers Authority (IANA) [17] according to the
   rules in Section 3 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, separated 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 tags defined in external standards (and
      which are used as subtags in this document).  For example, 'Latn'
      is an [ISO 15924] [3] script code which was used to define the
      'Latn' script subtag for use in a language tag.  Examples of codes
      in 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 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



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   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
      3.4.

   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 subtag is the first subtag in a language tag and cannot
   be empty.  Except as noted, the primary subtag is the language
   subtag.  The following rules apply to the assignment and
   interpretation of the primary subtag:

   o  All 2-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" [ISO 639-1] [1], or using
      assignments subsequently made by the ISO 639 Part 1 maintenance
      agency or governing standardization bodies.
   o  All 3-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" [ISO 639-2] [2], or assignments
      subsequently made by the ISO 639 Part 2 maintenance agency or
      governing standardization bodies.
   o  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 2.5
      for more information on private use subtags.




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   o  All language subtags of 4 to 8 characters in length in the IANA
      registry were defined via the registration process in Section 3.3
      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 subtags rejected by ISO 639 will be closely
      scrutinized before they are registered with IANA.
   o  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 2.5.
   o  Other values MUST NOT be assigned to the primary subtag except by
      revision or update of this document.

   Note: For languages that have both an ISO 639-1 2-character code and
   an ISO 639-2 3-character code, only the ISO 639-1 2-character code is
   defined in the IANA registry.

   Note: For languages that have no ISO 639-1 2-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 3-character code were also assigned
   a 2-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 [6]:

   "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
   2-character code is added to ISO 639-1 for a language for which a
   3-character code was already included in ISO 639-2, the 2-character
   code will not be added as a subtag in the registry.  See Section 3.2.

   For example, if some content were tagged with 'haw' (Hawaiian), which



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   currently has no 2-character code, the tag would not be invalidated
   if ISO 639-1 were to assign a 2-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:

   o  Three letter subtags immediately following the primary subtag are
      reserved for future standardization, anticipating work that is
      currently under way on ISO 639.
   o  Extended language subtags MUST follow the primary subtag and
      precede any other subtags.
   o  There MAY be any additional number of extended language subtags.
   o  Extended language subtags will not be registered except by
      revision of this document.
   o  Extended language subtags MUST NOT be used to form language tags
      except by revision of this document.

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

2.2.3  Script Subtag

   The following rules apply to the script subtags:

   o  All 4-character subtags were defined according to ISO 15924
      [3]--"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.
   o  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.
   o  The 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 2.5 for more information
      on private-use subtags.



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   o  Script subtags cannot be registered using the process in Section
      3.3 of this document.  Variant subtags may be considered for
      registration for that purpose.

   Example: "de-Latn" represents German written using the Latin script.

2.2.4  Region Subtag

   The following rules apply to the region subtags:

   o  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.
   o  All 2-character subtags following the primary subtag were defined
      in the IANA registry according to the assignments found in ISO
      3166 [4]--"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.
   o  All 3-character codes consisting of digit (numeric) characters
      were defined in the IANA registry according to the assignments
      found in UN Standard Country or Area Codes for Statistical  Use
      [5] 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:
      *  UN numeric codes assigned to 'macro-geographical (continental)'
         or sub-regions not associated with an assigned ISO 3166 alpha-2
         code *are* defined.
      *  UN numeric codes for 'economic groupings' or 'other groupings'
         are *not* defined in the IANA registry and MUST NOT be used to
         form language tags.
      *  Countries with ambiguous ISO 3166 alpha-2 codes as defined in
         Section 3.2 are defined in the registry and are canonical for
         the given country or region defined.
      *  The alphanumeric codes in Appendix X of the UN document are
         *not* defined 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.)
   o  There may be at most one region subtag in a language tag.
   o  The 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 2.5 for more information on
      private use subtags.

   "de-Latn-CH" represents German ('de') written using the Latin script



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   ('Latn') 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

   The following rules apply to the variant subtags:

   o  Variant subtags, as a collection in the IANA registry, are not
      associated with any external standard.  Variant subtags and their
      meanings are defined by the registration process defined in
      Section 3.3.
   o  Variant subtags MUST follow all of the other defined subtags, but
      precede any extension or private-use subtag sequences.
   o  More than one variant MAY be used to form the language tag.
   o  Variant subtags MUST be registered with IANA according to the
      rules in Section 3.3 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:
      *  Variant subtags that begin with a letter (a-z, A-Z) MUST be at
         least five characters long.
      *  Variant subtags that begin with a digit (0-9) MUST be at least
         four characters long.
      *  The maximum length of a variant subtag is eight characters
         long.

   "en-boont" represents the Boontling dialect of English.

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

2.2.6  Extension Subtags

   The following rules apply to extensions:

   o  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 3.4 and cannot be the letter
      'x', which is reserved for private-use subtag sequences.
   o  Note: Private-use subtag sequences starting with the singleton
      subtag 'x' are described below.




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   o  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.
   o  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.
   o  Extension subtags MUST meet all of the requirements for the
      content and format of subtags defined in this document.
   o  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.
   o  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 '-'.
   o  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'.
   o  Extension subtags MUST follow all language, extended language,
      script, region and variant subtags in a tag.
   o  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'.
   o  In the event that more than one extension appears in a single tag,
      the tag SHOULD be canonicalized as described in Section 2.4.1.

   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

   The following rules apply to private-use subtags:

   o  Private-use subtags are separated from the other subtags defined
      in this document by the reserved single-character subtag 'x'.
   o  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.
   o  Unlike Extensions, a tag MAY consist entirely of private-use
      subtags.




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   o  No source is defined for private use subtags.  Use of private use
      subtags is by private agreement and SHOULD NOT be considered part
      of this document.

   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
   that are not defined by additions to this document maintain their
   validity.  IANA will maintain these tags in the registry under either
   the "grandfathered" or "redundant" type.  For more information see
   Appendix C.

   It is important to note that all language tags formed under the
   guidelines in this document were either legal, well-formed tags or
   were valid for potential registration under RFC 3066.

2.2.9  Possibilities for Registration

   Possibilities for registration of 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 variation, or historical
      usage may be registered as variant subtags.  An example is the
      'scouse' subtag (the Scouse dialect of English).

   This document leaves the decision on what subtags are appropriate or
   not to the registration process described in Section 3.3.

   ISO 639 defines a maintenance agency for additions to and changes in



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   the list of languages in ISO 639.  This agency is:

   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

2.2.10  Classes of Conformance

   Implementations may wish to express their level of conformance with
   the rules and practices described in this document.  There are



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   generally two classes of conforming implementations: "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 2.4.1.

   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 3.4
      are supported, including version, revision, and date.
   o  For any such extensions supported, check that all subtags used in
      that extension are valid.
   o  If the processor generates tags, it MUST do so in canonical form,
      including any supported extensions, as defined in Section 2.4.1.

2.3  Choice of Language Tag

   One may occasionally be faced with 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.

   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.




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   1.  Use as precise a tag as possible, but no more specific than is
       justified.  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.  Avoid using subtags that are not important for distinguishing
       content in an application.  For example, including the script
       subtag in "en-Latn-US" is generally unnecessary, since nearly all
       English texts are written in the Latin script and it is generally
       not important to filter out those few that are not.
   3.  Use the canonical subtag from the IANA registry in preference to
       any of its aliases.  For example, you should use 'he' for Hebrew
       in preference to 'iw'.
   4.  You SHOULD NOT use the 'UND' (Undetermined) language subtag to
       label content, even if the language is unknown.  Omitting the tag
       is preferred.  Some protocols may force you to give a value for
       the language tag and the 'UND' subtag may be useful when matching
       language tags in certain situations.
   5.  You SHOULD NOT use the 'MUL' (Multiple) subtag if the protocol
       allows you to use multiple languages, as is the case for the
       Content-Language header in HTTP.
   6.  You SHOULD NOT use the same variant subtag more than once within
       a language tag.  For example, you should not use
       "en-US-boont-boont".

   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.  In addition, tags that are in
   canonical form will always be in canonical form.

2.4  Meaning of the Language Tag

   The language tag always defines a language as spoken (or 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.

   If a language tag B contains language tag A as a prefix, then B is
   typically "narrower" or "more specific" than A.  For example,
   "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 may 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



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   one script may 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.

   The relationship between the tag and the information it relates to is
   defined by the standard describing the context in which it 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 required 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
      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 misapplying
      the Norwegian rules.

2.4.1  Canonicalization of Language Tags

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

   A language tag is in canonical form when:
   1.  The tag is well-formed according the rules in Section 2.1 and
       Section 2.2.
   2.  None of the subtags in the language tag has a canonical_value
       mapping in the IANA registry (see Section 3.1).  Subtags with a
       canonical_value mapping MUST be replaced with their mapping in



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       order to canonicalize the tag.
   3.  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).

   Note: Canonicalization of language tags does not imply anything about
   the use of upper or lowercase letter in subtags as described in
   Section 2.1.  All comparisons MUST be performed in a case-insensitive
   manner.

   An extension MUST define any relationships that may 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 3.4.

2.5  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 may depend on the particular
   domain in question.




































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3.  IANA Considerations

   This section deals with the processes and requirements necessary to
   maintain the registry of subtags and extensions for use in language
   tags as defined by this document and in accordance with the
   requirements of RFC 2434 [15].

   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 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 3.3.  With the
   exception of the registration forms for grandfathered and redundant
   tags, no registration records will be maintained for the initial set
   of subtags.

   Each record in the subtag registry will consist of a series of fields
   separated by the symbol "|" (%x7D) and terminated by a newline.  Text
   appearing after the symbol "#" (%x23) contains comments.  Whitespace
   surrounding fields in the file is ignored.  If a field contains more
   than one value, the values are separated by semicolons (%x3B).

   There is a single date record at the start of the file which
   indicates the most recent modification date of the file.  It has two
   fields: the type field is "date", and the second field is the
   modification date, in the "full-date" format specified in RFC 3339
   [20].  For example: 2004-06-28 represents June 28, 2004 in the
   Gregorian calendar:
      date | 2004-06-28

   The fields in each subtag record, in order, are:
      type| subtag| description| date| canonical_value|
      recommended_prefix # comments





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   o  The character "vertical line" ("|", %x7D) delimits each of the
      fields.
   o  Empty fields (and their separators) at the end of the record may
      be omitted.
   o  Leading or trailing whitespace in each field is not part of the
      content.
   o  When the type is "grandfathered" or "redundant", then the subtag
      field is actually a whole tag.
   o  The "recommended_prefix" field is empty, except where the type is
      "variant"
   o  The "comments" field  is optional and appears only at the end of a
      record, following a "number sign" ("#", %x23).
   o  The sequence '..' 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'.

   The field 'type' MUST consist of one of the following strings:
   "language", "extlang", "script", "region", "variant",
   "grandfathered", and "redundant" and denotes the type of subtag (or
   tag, in the case of "grandfathered" and "redundant").

   The field 'subtag' contains the subtag being defined.

   The field 'description' contains a description of the subtag
   transcribed into ASCII.

   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
   and localization or translation of language tag and subtag
   descriptions is out of scope of this document.

   The field 'date' contains the date the record was added to the
   registry in the "full-date" format specified in RFC 3339 [20].  For
   example: 2004-06-28 represents June 28, 2004, in the Gregorian
   calendar.

   The field 'canonical value' represents a canonical mapping of this
   record to a subtag record of the same 'type'.  Note that this field
   SHALL NOT be modified (except for records of type "grandfathered"):
   therefore a subtag whose record contains no canonical mapping when
   the record is created is a canonical form and will remain so.

   The field 'recommended prefix' is for use with registered variants



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   and contains a semicolon separated list of language-ranges considered
   most appropriate for use with this subtag.  Additional values can be
   added to this field for variants only via additional registration.
   Other modification of this field (such as removing or changing
   values) is not permitted.

   The field 'comments' may contain additional information about the
   subtag, as deemed appropriate for understanding the registry and
   implementing language tags using the various subtags.  These values
   can be changed via the registration process and no guarantee of
   stability is provided.


   # IANA Language Subtag Registry
   # This registry lists all valid subtags for language tags
   # created under RFC XXXX.
   date| 2004-08-07

   # language codes: ISO 639 and registered codes

   # ISO 639-1 (alpha-2) codes
   language| aa| Afar| 2004-07-06| |
   language| ab| Abkhazian| 2004-07-06| |
   language| ae| Avestan| 2004-07-06| |
   language| he| hebrew| 2004-06-28| |
   language| iw| hebrew| 2004-06-28| he | #note mapping
   language| qaa..qtz| PRIVATE USE| 2004-07-06| |
   language| raj| Rajasthani| 2004-07-06| |
   language| seuss| Hypothetical Language| 2005-04-01 | |# registered language

   # script codes: ISO 15924

   script| Arab| Arabic| 2004-07-06| |
   script| Armn| Armenian| 2004-07-06| |
   script| Bali| Balinese| 2004-07-06| |
   # region codes: ISO 3166 and UN codes

   # ISO 3166-1 alpha-2 codes

   region| AA| PRIVATE USE| 2004-08-01| |
   region| AD| Andorra| 2004-07-06| |
   region| AE| United Arab Emirates| 2004-07-06| |
   region| AF| Afghanistan| 2004-07-06| |
   region| CS| Serbia and Montenegro| 2003-07-23| |
   region| YU| Yugoslavia| 2004-06-28| |

   # United Nations M.49 numeric codes
   region| 001| World| 2004-07-06| |



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   region| 002| Africa| 2004-07-06| |
   region| 003| North America| 2004-07-06| |
   region| 005| South America| 2004-07-06| |
   region| 200| Czechoslovakia| 2004-07-06| | #formerly used code CS

   ## registered variants

   variant| boont| Boontling| 2003-02-14| | en
   variant| gaulish| Gaulish| 2001-05-25| | cel
   variant| guoyu| Mandarin or Standard Chinese| 1999-12-18| | zh

   # grandfathered from RFC 3066

   grandfathered| en-GB-oed| English, Oxford English Dictionary spelling| 2003-07-09| |
   grandfathered| i-ami| Amis| 1999-05-25| |
   grandfathered| i-bnn| Bunun| 1999-05-25| |

   # redundant
   # The following codes were registered as complete tags, but can now be
   # composed of registered subtags and do not require registration.

   redundant| art-lojban| Lojban| 2001-11-11| |  # use language art + variant lojban
   redundant| az-Arab| Azerbaijani in Arabic script| 2003-05-30| |  # use language az + script Arab
   redundant| az-Cyrl| Azerbaijani in Cyrillic script| 2003-05-30| |  # use language az + script Cyrl
   redundant| en-boont| Boontling| 2003-02-14| |  # use language en + variant boont

                Figure 2: Example of the Registry Format

   Maintenance of the registry requires that as new codes are assigned
   by ISO 639, ISO 15924, and ISO 3166, the Language Subtag Reviewer
   will evaluate each assignment, determine whether it conflicts with
   existing registry entries, and submit the information to IANA for
   inclusion in the registry.

   Note: The redundant and grandfathered entries together are the
   complete list of tags registered under RFC 3066 [18].  The redundant
   tags are those that can now be formed using the subtags defined in
   Section 2.2.  The grandfathered entries are those that can never be
   legal under those same provisions.  The items in both lists are
   permanent and stable, although grandfathered items may be deprecated
   over time.  Refer to Appendix C for more information.

   The Language Subtag Reviewer MUST ensure that new subtags meet the
   requirements in Section 2.3 or submit an appropriate alternate subtag
   as described in that section.  She or he will use the following form
   to submit this information:





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   LANGUAGE SUBTAG REGISTRATION FORM (NEW RECORD)
   Record Text:
   Type:
   Subtag:
   Description:
   Date:
   Canonical Mapping:
   Recommended Prefix:
   Comments:

                                Figure 3

   The field 'record text' contains the exact record that IANA is to
   insert into the Language Subtag Registry.  The contents of the
   remaining fields must exactly match those in this field.

   Whenever an entry is created or modified in the registry, the 'date'
   record at the start of the registry is updated to reflect the most
   recent modification date in the RFC 3339 [20] "full-date" format.

3.2  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
   this section guarantee that a specific language tag's meaning is
   stable over time and will not change and that the choice of language
   tag for specific content is also stable over time.

   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', 'date' and 'canonical
      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 'recommended prefix' MAY be added via the
      registration process.
   o  Values in the field 'recommended prefix' MAY be modified, so long
      as the modifications broaden the set of recommended prefixes.
      That is, a recommended prefix MAY be replaced by one of its own
      prefixes.  For example, the prefix "en-US" could be replaced by



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      "en", but not by the ranges "en-Latn", "fr", or "en-US-boont".
   o  Values in the field 'recommended 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  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 and their value is
      canonical for the meaning assigned to them.
   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.  The registration process
      MAY be used to add a note indicating the withdrawal of the code by
      the respective standard.
   o  Codes assigned by ISO 639, ISO 15924, or ISO 3166 that do not
      conflict with existing subtags of the associated type but which
      represent the same meaning as an existing subtag of that type are
      entered into the IANA registry as new records.  The field
      'canonical value' for that record MUST contain the existing subtag
      of the same meaning
      Example If ISO 3166 were to assign the code 'IM' to represent the
         value "Isle of Man" (represented in the IANA registry by the UN
         M.49 code '833'), '833' remains the canonical subtag and 'IM'
         would be assigned '833' as a canonical value.  This prevents
         tags that are in canonical form from becoming non-canonical.
      Example If the tag 'enochian' were registered as a primary
         language subtag and ISO 639 subsequently assigned an alpha-3
         code to the same language, the new ISO 639 code would be
         entered into the IANA registry as a subtag with a canonical
         mapping to 'enochian'.  The new ISO code can be used, but it is
         not canonical.
   o  Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict
      with existing subtags of the associated type MUST NOT be entered
      into the registry.  The following additional considerations apply:
      *  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 3.3, 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



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         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 3.3, 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'
         subtag, then the existing region subtag remains as the
         canonical entry for that region and no new entry is created.  A
         note 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 then the Language Subtag Reviewer,
         as described in Section 3.3, shall prepare a proposal for
         entering the appropriate numeric UN country code as an entry in
         the IANA 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 grandfathered tag
      MUST be marked as 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 valid).

   Language tags formed under RFC 3066 that use the region subtag 'CS'
   were ambiguous, since tags produced before 2003 used that code for



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   the (now dissolved) country Czechoslovakia.  ISO 3166 assigned this
   code to the country Serbia and Montenegro in 2003 and this draft
   makes that the canonical value for this subtag.  To form a language
   tag for the region Czechoslovakia, the UN M.49 code '200' is included
   in the registry.  As a practical matter, applications that encounter
   the RFC 3066 tag "cs-CS" or "sk-CS" MAY wish to convert that to
   "cs-200" or "sk-200" (or use one of the successor region subtags,
   such as 'CZ' or 'SK'), since that is the most likely interpretation.

3.3  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 primary language and variant subtags will be considered for
   independent registration.  (Subtags required for stability and
   subtags required to keep the registry synchronized with ISO 639, ISO
   15924, ISO 3166, and UN M.49 within the limits defined by this
   document are the only exceptions to this.  See Section 3.2.)

   This procedure MAY also be used to register or alter the information
   for the "description", "note", or "recommended prefix" fields in a
   subtag's record as described in Figure 2.  Changes to all other
   fields in the IANA registry are NOT permitted.

   If registering a new language subtag, the process starts by filling
   out the registration form reproduced below.  Note that each response
   is not limited in size and should take the room necessary to
   adequately describe the registration.

   LANGUAGE SUBTAG REGISTRATION FORM
   1. Name of requester:
   2. E-mail address of requester:
   3. Subtag to be registered:
   4. Type of Registration:
      [ ] language
      [ ] variant
   5. Description of subtag (in English or transcribed into ASCII):
   6. Intended meaning of the subtag:
   7. Recommended prefix(es) of subtag (for variants):
   8. Native name of the language or variation (transcribed into ASCII):
   9. Reference to published description of the language (book or article):
   10. Any other relevant information:

                                Figure 4

   The subtag registration form MUST be sent to
   <ietf-languages@iana.org> for a two week review period before it can



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   be submitted to IANA.  (This is an open list.  Requests to be added
   should be sent to <ietf-languages-request@iana.org>.)

   Variant subtags are generally registered for use with a particular
   range of language tags.  For example, the subtag 'boont' is intended
   for use with language tags that start with the primary language
   subtag "en", since Boontling is a dialect of English.  Thus the
   subtag 'boont' could be included in tags such as "en-Latn-boont" or
   "en-US-boont".  This information is stored in the "recommended
   prefix" field in the registry and MUST be provided in the
   registration form.

   Any subtag MAY be incorporated into a variety of language tags,
   according to the rules of Section 2.1, including tags that do not
   match any of the recommended prefixes of the registered subtag.
   (Note that this is probably a poor choice.) This makes validation
   simpler and thus more uniform across implementations, and does not
   require the registration of a separate subtag for the same purpose
   and meaning but a different recommended prefix.

   The recommended prefixes for a given registered subtag will be
   maintained in the IANA registry as a guide to usage.  If it is
   necessary to add an additional prefix to that list for an existing
   language tag, that can be done by filing an additional registration
   form.  In that form, the "Any other relevant information:" field
   should indicate that it is the addition of an additional recommended
   prefix.

   Requests to add a recommended prefix to a 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 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
   either forwards the request to iana@iana.org, or rejects it because
   of significant objections raised on the list or due to problems with
   constraints in this document (which should 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.



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   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 [RFC 2028]
   [10] under the same rules as other IETF decisions [RFC 2026] [21].

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

   Updates of registrations follow the same procedure as registrations.
   The subtag reviewer decides whether to allow a new registrant to
   update a registration made by someone else; normally objections by
   the original registrant would carry extra weight in such a decision.

   Registrations are permanent and stable.  Once registered, subtags
   will not be removed from the registry and will remain the canonical
   method of referring to a specific language or variant.  This
   provision does not apply to grandfathered tags, which may become
   deprecated due to registration of subtags.  For example, the tag
   "i-navajo" is deprecated in favor of the ISO 639-1 based subtag 'nv'.

   Note: The purpose of the "published 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.

3.4  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 process language tags according to this specification.  For
   example, they might be used to define locale identifiers, which are
   generally based on language.




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   The structure and form of extensions are defined by this document so
   that implementations can be created that are forward compatible with
   applications that may 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.

   IANA will maintain a registry of allocated single-letter subtags.
   This registry contains the following information: letter identifier;
   name; purpose; RFC defining the subtag namespace and its use; and the
   name, URL, and email address of the maintaining authority.

   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
   each of the following:
   o  The specification MUST reference the specific version or revision
      of this document that govern 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.
   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  IANA MUST be informed of changes to the contact information and
      URL for the specification.

   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



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   mechanisms that interfere with matching or with length restrictions
   that may 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, it should be noted that
   some protocols may impose upper limits on the length of the strings
   used to store or transport the language tag.






































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4.  Security Considerations

   The only security issue that has been raised with language tags since
   the publication of RFC 1766, which stated that "Security issues are
   believed to be irrelevant to this memo", is a concern with language
   identifiers used in content negotiation - that they may 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 you send
   is visible to the receiving party.  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.

   Although the specification of valid subtags for an extension 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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5.  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 presentation 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 may 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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6.  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 XML
   Schema version 1.0) 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



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   required for information technology.

   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 extlang subtags.  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  Changes the IANA language tag registry to 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.  Adds the concept of a variant subtag and allows
      variants to be used generatively.  Adds the ability to use a class
      of UN tags as regions.
   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.



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

   Changes between draft-09 and this version are:
   o  Split the document into two drafts: this document and
      draft-phillips-langmatching-00.  (A.Phillips, M.Davis)
   o  Removed all references to the matching and language ranges
      sections from this document.  (A.Phillips, M.Davis)
   o  Added a note about the fact that all tags valid under this
      document would have been valid or valid to register under RFC 3066
      to Section 2.2.8.  (A.Phillips)
   o  Modified text as appropriate in several sections, notably about
      extensions, so that matching is not referred to or is referred to
      only in general terms (A.Phillips, M.Davis)
   o  Expunged the terminology "language range", since that section goes
      with matching (A.Phillips, M.Davis)

7  References

   [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.

   [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.

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

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

   [5]   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.

   [6]   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>.

   [7]   Hardcastle-Kille, S., "Mapping between X.400(1988) / ISO 10021
         and RFC 822", RFC 1327, May 1992.

   [8]   Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail



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         Extensions) Part One: Mechanisms for Specifying and Describing
         the Format of Internet Message Bodies", RFC 1521, September
         1993.

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

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

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

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

   [13]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
         Specifications: ABNF", RFC 2234, November 1997.

   [14]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
         Resource Identifiers (URI): Generic Syntax", RFC 2396, August
         1998.

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

   [16]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
         Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
         HTTP/1.1", RFC 2616, June 1999.

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

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

   [19]  Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
         63, RFC 3629, November 2003.

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

   [21]  <http://www.ietf.org/rfc/rfc2026.txt>





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Authors' Addresses

   Addison Phillips (editor)
   webMethods, Inc.
   432 Lakeside Drive
   Sunnyvale, CA  94088
   US

   EMail: aphillips@webmethods.com


   Mark Davis
   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, Jeremy Carroll,
   John Clews, Jim Conklin, Peter Constable, John Cowan, Mark Crispin,
   Dave Crocker, Martin Duerst, Michael Everson, Doug Ewell, Ned Freed,
   Tim Goodwin, Dirk-Willem van Gulik, Marion Gunn, Joel Halpren,
   Elliotte Rusty Harold, Paul Hoffman, Richard Ishida, Olle Jarnefors,
   Kent Karlsson, John Klensin, Alain LaBonte, Eric Mader, Keith Moore,
   Chris Newman, Masataka Ohta, 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 (Traditional Chinese)
      en-Latn (English written in Latin script)
      sr-Cyrl (Serbian written with Cyrillic script)

   Language-Script-Region:
      zh-Hans-CN (Simplified Chinese for the PRC)
      sr-Latn-CS (Serbian, Latin script, Serbia and Montenegro)

   Language-Script-Region-Variant:
      en-Latn-US-boont (Boontling dialect of English)
      de-Latn-CH-1996 (German written in Latin script for Switzerland
      using the orthography of 1996)

   Language-Region:
      de-DE (German for Germany)
      zh-SG (Chinese for Singapore)
      cs-200 (Czech for Czechoslovakia)
      sr-CS (Serbian for Serbia and Montenegro)
      es-419 (Spanish for Latin America and Caribbean region using the
      UN region code)

   Other Mixtures:
      en-boont (Boontling dialect of English)

   private-use mechanism:
      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 subtags:
      x-whatever (private use using the singleton 'x')
      qaa-Qaaa-QM-x-southern (all private tags)






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      de-Qaaa (German, with a private script)
      de-Latn-QM (German, Latin-script, private region)
      de-Qaaa-DE (German, private script, for Germany)

   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
      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.  Conversion of the RFC 3066 Language Tag Registry

   Upon publication of this document as a BCP, the existing IANA
   language tag registry must be converted into the new subtag registry.
   This section defines the process for performing this conversion.

   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.

   When this document is published, an email request will be sent from
   the authors of this document to the list ietf-languages@iana.org
   requesting the conversion of the registry.  In that request, the
   authors of this document will provide a URL whose referred content is
   the proposed IANA Language Subtag Registry following conversion.
   There will be a Last Call period of not less than four weeks for
   comments and corrections to be discussed on the
   ietf-languages@iana.org mail list.  Changes as a result of comments
   will not restart the Last Call period.  At the end of the period, the
   authors will forward the URL to IANA, which will post the new
   registry on-line.

   Tags that are currently deprecated will be maintained as
   grandfathered entries.  The record for the grandfathered entry will
   contain a note indicating that the entry is 'deprecated' and reason
   for the deprecation.

   Tags that consist entirely of subtags that are valid under this
   document and which have the correct form and format for tags defined
   by this document are superseded by this document.  Such tags are
   placed in the 'redundant' section of the registry.  For example,
   zh-Hant is now defined by this document.

   Tags that contain subtags which are consistent with registration
   under the guidelines in this document will have a new subtag
   registration created for each eligible subtag.  If all of the subtags
   in the original tag are fully defined by the resulting registrations
   or by this document, then the original tag is superseded by this
   document.  Such tags are placed in the 'redundant' section of the
   registry.  For example, en-boont will result in a new subtag "boont"
   and the RFC 3066 registered tag 'en-boont' placed in the redundant
   section of the registry.

   Tags that contain one or more subtags that do not match the valid
   registration pattern and which are not otherwise defined by this
   document are marked as 'grandfathered' by this document.




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   There will be a reasonable period in which the community may comment
   on the proposed list entries, which SHALL be no less than four weeks
   in length.  At the completion of this period, the Language Subtag
   Reviewer will notify iana@iana.org and the 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.

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

   The rules governing the conversion of RFC 1766 and RFC 3066
   registered tags are:

   o  If the formerly registered tag would now be defined by this
      document, then the existing tag is superseded by this document and
      is placed in the 'redundant' section of the registry: no subtag
      will be registered as a result.  For example, 'zh-Hans' is now
      defined by the addition of ISO 15924 script codes.
   o  If the registered tag contained one or more subtags that follow
      the guidelines for registered language or variant subtags, and all
      of the subtags are either now defined by this document or would be
      valid to register, then each subtag not already covered by this
      document will be registered automatically by IANA without further
      review.  The RFC 3066 registered tag is placed in the 'redundant'
      section of the registry.  For example: the tag 'en-boont' fits the
      pattern for a registered variant.  The variant subtag "boont" will
      be registered automatically and 'en-boont' put into the
      'redundant' section of the registry.
   o  If the registered tag contains any subtags that are not otherwise
      valid for registration according to the rules in this document,
      then the tag as a whole is maintained as an exceptional case (that
      is, it is "grandfathered").  This includes special cases of Sign
      Language tags.  For example, the tag 'zh-min-nan' is not covered
      by any addition and is grandfathered, as is 'sgn-BE-fr' (Belgian
      French Sign Language).

   Users of tags that are grandfathered should consider registering
   appropriate subtags in the IANA subtag registry (but are not required
   to).

   Where two subtags have the same meaning, the priority of which to
   make canonical SHALL be the following:




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   o  As of January 1, 2005, if a code exists in the associated ISO
      standard and it is not deprecated or withdrawn as of that date,
      then it has priority.
   o  Otherwise, the earlier-registered tag in the associated ISO
      standard has priority.

   UN numeric codes assigned to 'macro-geographical (continental)' or
   sub-regions not associated with an assigned ISO 3166 alpha-2 code are
   defined in the IANA registry and are 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 groupings',
   and the alphanumeric codes in Appendix X of the UN document MUST NOT
   be added to the registry.






































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