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RFC 4646


Tags for Identifying Languages

Part 2 of 3, p. 18 to 38
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3.  Registry Format and Maintenance

   This section defines the Language Subtag Registry and the maintenance
   and update procedures associated with it, as well as a registry for
   extensions to language tags (Section 3.7).

   The Language Subtag Registry 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.  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.)

3.1.  Format of the IANA Language Subtag Registry

   The IANA Language Subtag Registry ("the registry") consists of a text
   file that is machine readable in the format described in this
   section, plus copies of the registration forms approved in accordance
   with the process described in Section 3.5.  The existing registration
   forms for grandfathered and redundant tags taken from RFC 3066 will
   be maintained as part of the obsolete RFC 3066 registry.  The
   remaining set of initial subtags will not have registration forms
   created for them.

   The registry is in the text format described below.  This format was
   based on the record-jar format described in [record-jar].

   Each line of text is limited to 72 characters, including all
   whitespace.  Records are separated by lines containing only the
   sequence "%%" (%x25.25).

   Each field can be viewed as a single, logical line of ASCII
   characters, comprising a field-name and a field-body separated by a
   COLON character (%x3A).  For convenience, the field-body portion of
   this conceptual entity can be split into a multiple-line
   representation; this is called "folding".  The format of the registry
   is described by the following ABNF (per [RFC4234]):

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

                      Figure 2: Registry Format ABNF

   The sequence '..' (%x2E.2E) in a field-body denotes a range of
   values.  Such a range represents all subtags of the same length that
   are in alphabetic or numeric order within that range, including the
   values explicitly mentioned.  For example 'a..c' denotes the values
   'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and

   Characters from outside the US-ASCII [ISO646] repertoire, as well as
   the AMPERSAND character ("&", %x26) when it occurs in a field-body,
   are represented by a "Numeric Character Reference" using hexadecimal
   notation in the style used by [XML10] (see
   <>).  This consists of the
   sequence "&#x" (%x26.23.78) followed by a hexadecimal representation
   of the character's code point in [ISO10646] followed by a closing
   semicolon (%x3B).  For example, the EURO SIGN, U+20AC, would be
   represented by the sequence "&#x20AC;".  Note that the hexadecimal
   notation MAY have between two and six digits.

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

   The first record in the file contains the single field whose field-
   name is "File-Date" (see Figure 3).  The field-body of this record
   contains the last modification date of this copy of the registry,
   making it possible to compare different versions of the registry.
   The registry on the IANA website is the most current.  Versions with
   an older date than that one are not up-to-date.

   File-Date: 2004-06-28

                 Figure 3: Example of the File-Date Record

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

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   o  'Type'

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

   o  Either 'Subtag' or 'Tag'

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

      *  Tag's field-value contains a complete language tag.  This field
         MUST only appear in records whose 'Type' has one of these
         values: "grandfathered" or "redundant".  Note that the field-
         value will always follow the 'grandfathered' production in the
         ABNF in Section 2.1

   o  Description

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

   o  Added

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

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

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

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

   Each record MAY also contain the following fields:

   o  Preferred-Value

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

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

   o  Deprecated

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

   o  Prefix

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

   o  Comments

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

   o  Suppress-Script

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

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   The field 'Deprecated' MAY be added to any record via the maintenance
   process described in Section 3.3 or via the registration process
   described in Section 3.5.  Usually, the addition of a 'Deprecated'
   field is due to the action of one of the standards bodies, such as
   ISO 3166, withdrawing a code.  In some historical cases, it might not
   have been possible to reconstruct the original deprecation date.  For
   these cases, an approximate date appears in the registry.  Although
   valid in language tags, subtags and tags with a 'Deprecated' field
   are deprecated and validating processors SHOULD NOT generate these
   subtags.  Note that a record that contains a 'Deprecated' field and
   no corresponding 'Preferred-Value' field has no replacement mapping.

   The field 'Preferred-Value' contains a mapping between the record in
   which it appears and another tag or subtag.  The value in this field
   is STRONGLY RECOMMENDED as the best choice to represent the value of
   this record when selecting a language tag.  These values form three

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

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

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

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

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

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

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   The field 'Preferred-Value' MUST NOT be modified once created in the
   registry.  The field MAY be added to records of type "grandfathered"
   and "region" according to the rules in Section 3.3.  Otherwise the
   field MUST NOT be added to any record already in the registry.

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

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

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

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

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

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

   The field 'Suppress-Script' MUST only appear in records whose 'Type'
   field-value is 'language'.  This field MUST NOT appear more than one
   time in a record.  This field indicates a script used to write the
   overwhelming majority of documents for the given language and that
   therefore adds no distinguishing information to a language tag.  It
   helps ensure greater compatibility between the language tags
   generated according to the rules in this document and language tags
   and tag processors or consumers based on RFC 3066.  For example,
   virtually all Icelandic documents are written in the Latin script,
   making the subtag 'Latn' redundant in the tag "is-Latn".

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3.2.  Language Subtag Reviewer

   The Language Subtag Reviewer is appointed by the IESG for an
   indefinite term, subject to removal or replacement at the IESG's
   discretion.  The Language Subtag Reviewer moderates the ietf-
   languages mailing list, responds to requests for registration, and
   performs the other registry maintenance duties described in
   Section 3.3.  Only the Language Subtag Reviewer is permitted to
   request IANA to change, update, or add records to the Language Subtag

   The performance or decisions of the Language Subtag Reviewer MAY be
   appealed to the IESG under the same rules as other IETF decisions
   (see [RFC2026]).  The IESG can reverse or overturn the decision of
   the Language Subtag Reviewer, provide guidance, or take other
   appropriate actions.

3.3.  Maintenance of the Registry

   Maintenance of the registry requires that as codes are assigned or
   withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language
   Subtag Reviewer MUST evaluate each change, determine whether it
   conflicts with existing registry entries, and submit the information
   to IANA for inclusion in the registry.  If a change takes place and
   the Language Subtag Reviewer does not do this in a timely manner,
   then any interested party MAY use the procedure in Section 3.5 to
   register the appropriate update.

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

   The set of redundant and grandfathered tags is permanent and stable:
   new entries in this section MUST NOT be added and existing entries
   MUST NOT be removed.  Records of type 'grandfathered' MAY have their
   type converted to 'redundant'; see item 12 in Section 3.6 for more
   information.  The decision-making process about which tags were
   initially grandfathered and which were made redundant is described in

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

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   The Language Subtag Reviewer MUST ensure that new subtags meet the
   requirements in Section 4.1 or submit an appropriate alternate subtag
   as described in that section.  When either a change or addition to
   the registry is needed, the Language Subtag Reviewer MUST prepare the
   complete record, including all fields, and forward it to IANA for
   insertion into the registry.  Each record being modified or inserted
   MUST be forwarded in a separate message.

   If a record represents a new subtag that does not currently exist in
   the registry, then the message's subject line MUST include the word
   "INSERT".  If the record represents a change to an existing subtag,
   then the subject line of the message MUST include the word "MODIFY".
   The message MUST contain both the record for the subtag being
   inserted or modified and the new File-Date record.  Here is an
   example of what the body of the message might contain:

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

         Figure 4: Example of a Language Subtag Modification Form

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

   Before forwarding a new registration to IANA, the Language Subtag
   Reviewer MUST ensure that values in the 'Subtag' field match case
   according to the description in Section 3.1.

3.4.  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.

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   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:

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

   2.   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; a historical example
        of this would be "Upper Volta" changing to "Burkina Faso".

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

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

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

   6.   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.

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

   8.   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.

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

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

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

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

        A.  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 3.5, 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.

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

        C.  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 3.5, 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

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            subtag will be at the discretion of the Language Subtag
            Reviewer and MUST conform to other restrictions on variant
            subtags in this document.

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

        E.  For ISO 3166 codes, if the newly assigned code's meaning is
            associated with a UN M.49 code that is not represented by an
            existing region subtag, then the Language Subtag Reviewer,
            as described in Section 3.5, SHALL prepare a proposal for
            entering the appropriate UN M.49 country code as an entry in
            the IANA registry.

        F.  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.

   11.  UN M.49 has codes for both countries and areas (such as '276'
        for Germany) and geographical regions and sub-regions (such as
        '150' for Europe).  UN M.49 country or area codes for which
        there is no corresponding ISO 3166 code SHOULD NOT be
        registered, except as a surrogate for an ISO 3166 code that is
        blocked from registration by an existing subtag.  If such a code
        becomes necessary, then the registration authority for ISO 3166
        SHOULD first be petitioned to assign a code to the region.  If
        the petition for a code assignment by ISO 3166 is refused or not
        acted on in a timely manner, the registration process described
        in Section 3.5 MAY then be used to register the corresponding UN
        M.49 code.  At the time this document was written, there were
        only four such codes: 830 (Channel Islands), 831 (Guernsey), 832
        (Jersey), and 833 (Isle of Man).  This way, UN M.49 codes remain
        available as the value of last resort in cases where ISO 3166
        reassigns a deprecated value in the registry.

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

3.5.  Registration Procedure for Subtags

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

   Only subtags of type 'language' and 'variant' will be considered for
   independent registration of new subtags.  Handling of subtags needed
   for stability and subtags necessary to keep the registry synchronized
   with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits
   defined by this document are described in Section 3.3.  Stability
   provisions are described in Section 3.4.

   This procedure MAY also be used to register or alter the information
   for the 'Description', 'Comments', 'Deprecated', or 'Prefix' fields
   in a subtag's record as described in Section 3.4.  Changes to all
   other fields in the IANA registry are NOT permitted.

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

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   1. Name of requester:
   2. E-mail address of requester:
   3. Record Requested:


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

              Figure 5: The Language Subtag Registration Form

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

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

   Extended language subtags are reserved for future standardization.
   These subtags will be REQUIRED to include exactly one 'Prefix' field
   once they are allowed for registration.

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

   Requests to add a prefix to a variant subtag that imply a different
   semantic meaning will probably be rejected.  For example, a request
   to add the prefix "de" to the subtag 'nedis' so that the tag

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   "de-nedis" represented some German dialect would be rejected.  The
   'nedis' subtag represents a particular Slovenian dialect and the
   additional registration would change the semantic meaning assigned to
   the subtag.  A separate subtag SHOULD be proposed instead.

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

   While the 'Description' field itself is not guaranteed to be stable
   and errata corrections MAY be undertaken from time to time, attempts
   to provide translations or transcriptions of entries in the registry
   itself will probably be frowned upon by the community or rejected
   outright, as changes of this nature have an impact on the provisions
   in Section 3.4.

   When the two-week period has passed, the Language Subtag Reviewer
   either forwards the record to be inserted or modified to according to the procedure described in Section 3.3, or
   rejects the request because of significant objections raised on the
   list or due to problems with constraints in this document (which MUST
   be explicitly cited).  The Language Subtag Reviewer MAY also extend
   the review period in two-week increments to permit further
   discussion.  The Language Subtag Reviewer MUST indicate on the list
   whether the registration has been accepted, rejected, or extended
   following each two-week period.

   Note that the Language Subtag Reviewer MAY 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 Language Subtag Reviewer MAY be appealed to the
   IESG [RFC2028] under the same rules as other IETF decisions

   All approved registration forms are available online in the directory under "languages".

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

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

   Note: The purpose of the "Description" in the registration form is to
   aid 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 Language 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.

3.6.  Possibilities for Registration

   Possibilities for registration of subtags or information about
   subtags include:

   o  Primary language subtags for languages not listed in ISO 639 that
      are not variants of any listed or registered language MAY 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.  Subtags MUST NOT be registered for codes that exist
      in ISO 639-1 or ISO 639-2, that are under consideration by the ISO
      639 maintenance or registration authorities, or that have never
      been attempted for registration with those authorities.  If ISO
      639 has previously rejected a language for registration, it is
      reasonable to assume that there must be additional, very
      compelling evidence of need before it will be registered in the
      IANA registry (to the extent that it is very unlikely that any
      subtags will be registered of this type).

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

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   o  The addition or maintenance of fields (generally of an
      informational nature) in Tag or Subtag records as described in
      Section 3.1 and subject to the stability provisions in
      Section 3.4.  This includes descriptions, comments, deprecation
      and preferred values for obsolete or withdrawn codes, or the
      addition of script or extlang information to primary language

   o  The addition of records and related field value changes necessary
      to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and
      UN M.49 as described in Section 3.4.

   Subtags proposed for registration that would cause all or part of a
   grandfathered tag to become redundant but whose meaning conflicts
   with or alters the meaning of the grandfathered tag MUST be rejected.

   This document leaves the decision on what subtags or changes to
   subtags are appropriate (or not) to the registration process
   described in Section 3.5.

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

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

   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

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   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

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

   Unicode Consortium Box 391476
   Mountain View, CA 94039-1476, USA

   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

3.7.  Extensions and Extensions Registry

   Extension subtags are those introduced by single-character subtags
   ("singletons") other than 'x'.  They are reserved for the generation
   of identifiers that contain a language component and are compatible
   with applications that understand language tags.

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

   Single-character subtags are assigned by IANA using the "IETF
   Consensus" policy defined by [RFC2434].  This policy requires the
   development of an RFC, which SHALL define the name, purpose,
   processes, and procedures for maintaining the subtags.  The
   maintaining or registering authority, including name, contact email,

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   discussion list email, and URL location of the registry, MUST be
   indicated clearly in the RFC.  The RFC MUST specify or include each
   of the following:

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

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

   o  The specification MUST specify a canonical representation.

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

3.8.  Initialization of the Registries

   Upon adoption of this document, an initial version of the Language
   Subtag Registry containing the various subtags initially valid in a
   language tag is necessary.  This collection of subtags, along with a
   description of the process used to create it, is described by
   [RFC4645].  IANA SHALL publish the initial version of the registry
   described by this document from the content of [RFC4645].  Once
   published by IANA, the maintenance procedures, rules, and
   registration processes described in this document will be available
   for new registrations or updates.

   Registrations that are in process under the rules defined in
   [RFC3066] when this document is adopted MAY be completed under the
   former rules, at the discretion of the Language Tag Reviewer (as
   described in [RFC3066]).  Until the IESG officially appoints a
   Language Subtag Reviewer, the existing Language Tag Reviewer SHALL
   serve as the Language Subtag Reviewer.

   Any new registrations submitted using the RFC 3066 forms or format
   after the adoption of this document and publication of the registry
   by IANA MUST be rejected.

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   An initial version of the Language Tag Extensions Registry described
   in Section 3.7 is also needed.  The Language Tag Extensions Registry
   SHALL be initialized with a single record containing a single field
   of type "File-Date" as a placeholder for future assignments.

(page 38 continued on part 3)

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