One document matched: draft-ietf-ltru-4646bis-13.xml
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<rfc ipr="full3978" docName="draft-ietf-ltru-4646bis-13" category="bcp" obsoletes="4646" xml:lang="en-US">
<front>
<title abbrev="language-tags">Tags for Identifying Languages</title>
<author initials="A" surname="Phillips" fullname="Addison Phillips" role="editor">
<organization>Lab126</organization>
<address>
<email>addison@inter-locale.com</email>
<uri>http://www.inter-locale.com</uri>
</address>
</author>
<author initials="M" surname="Davis" fullname="Mark Davis" role="editor">
<organization>Google</organization>
<address>
<email>mark.davis@google.com</email>
</address>
</author>
<date year="2008" month="April" day="29"/>
<area>LTRU</area>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<abstract>
<t>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.</t>
</abstract>
</front>
<middle>
<section title="Introduction" anchor="intro">
<t>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.</t>
<t>A user's language preferences often need to be identified
so that appropriate processing can be applied. For example, the user's language
preferences in a Web browser can be used to select Web pages appropriately. Language preferences can also be used to select among tools (such as
dictionaries) to assist in the processing or understanding of content in
different languages.</t>
<t>In addition, knowledge about the particular language used by some piece of information content might be
useful or even required by some types of processing; for example,
spell-checking, computer-synthesized speech, Braille transcription, or
high-quality print renderings.</t>
<t>One means of indicating the language used is by labeling the information content
with an identifier or "tag". These
tags can be used to specify user preferences when selecting information content,
or for labeling additional attributes of content and associated resources.</t>
<t>Tags can also be used to indicate additional language attributes of content. For example, indicating specific information about the dialect, writing system, or orthography used in a document or resource may enable the user to obtain information in a form that they can understand, or it can be important in processing or rendering the given content into an appropriate form or style.</t>
<t>This document specifies a particular identifier mechanism (the language tag) and a registration function for values
to be used to form tags. It also defines a mechanism for private use values and future extension.</t>
<t>This document replaces <xref target="RFC4646"/>, which replaced <xref target="RFC3066"/> and its predecessor <xref target="RFC1766"/>. For a list of changes
in this document, see <xref target="changes"/>.
</t>
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in <xref target="RFC2119"/>.</t>
</section>
<section title="The Language Tag" anchor="langtag">
<t>Language tags are used to help identify languages, whether spoken, written, signed, or otherwise signaled, for the purpose of communication. This includes constructed and artificial languages, but excludes languages not intended primarily for human communication, such as programming languages.</t>
<section title="Syntax" anchor="syntax">
<t>The language tag is composed of one or more parts, known as "subtags". Each subtag consists of a sequence of alphanumeric characters. Subtags are distinguished and separated from one another by a hyphen ("-", ABNF <xref target="RFC5234"/> %x2D). Usually a language tag contains a "primary language" subtag, followed by a (possibly empty) series of subsequent subtags, each of which refines or narrows the range of languages identified by the overall tag.</t>
<t>Most subtags are distinguished by length, position in the tag, and content: subtags can be recognized solely by these features. This makes it possible to construct a parser that can extract and assign some semantic information to the subtags, even if the specific subtag values are not recognized. Thus, a parser need not have a list of valid tags or subtags (that is, a copy of some version of the IANA Language Subtag Registry) in order to perform common searching and matching operations. The grandfathered tags registered under <xref target="RFC3066">RFC 3066</xref>, a fixed list that can never change, are the only exception to this ability to infer meaning from subtag structure.</t>
<figure anchor="ABNF" title="Language Tag ABNF">
<preamble>The syntax of the language tag in ABNF <xref target="RFC5234"/> is:</preamble>
<artwork type="abnf" name="abnf.text">
Language-Tag = langtag
/ privateuse ; private use tag
/ irregular ; tags grandfathered by rule
langtag = (language
["-" script]
["-" region]
*("-" variant)
*("-" extension)
["-" privateuse])
language = 2*3ALPHA ; shortest ISO 639 code
/ 4ALPHA ; reserved for future use
/ 5*8ALPHA ; registered language subtag
script = 4ALPHA ; ISO 15924 code
region = 2ALPHA ; ISO 3166-1 code
/ 3DIGIT ; UN M.49 code
variant = 5*8alphanum ; registered variants
/ (DIGIT 3alphanum)
extension = singleton 1*("-" (2*8alphanum))
singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT
; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9"
; Single alphanumerics
; "x" is reserved for private use
privateuse = "x" 1*("-" (1*8alphanum))
irregular = "en-GB-oed" / "i-ami" / "i-bnn" / "i-default"
/ "i-enochian" / "i-hak" / "i-klingon" / "i-lux"
/ "i-mingo" / "i-navajo" / "i-pwn" / "i-tao"
/ "i-tay" / "i-tsu" / "no-bok" / "no-nyn"
/ "sgn-BE-FR" / "sgn-BE-NL" / "sgn-CH-DE" / "zh-cmn"
/ "zh-cmn-Hans" / "zh-cmn-Hant" / "zh-gan"
/ "zh-min" / "zh-min-nan" / "zh-wuu" / "zh-yue"
alphanum = (ALPHA / DIGIT) ; letters and numbers
</artwork>
<postamble/>
</figure>
<t>All subtags have a maximum length of eight characters and whitespace is not permitted
in a language tag. There is a subtlety in the ABNF production 'variant': variants starting with a digit MAY be four characters long, while those starting with a letter MUST be at least five characters long. For examples of language tags, see <xref target="examples"/>.
</t>
<t>Note Well: the ABNF syntax does not distinguish between upper and lowercase. The appearance of upper and lowercase letters in the various ABNF productions above do not affect how implementations interpret tags. That is, the tag "I-AMI" matches the item "i-ami" in the 'irregular' production. At all times, the tags and their subtags, including private use and extensions, are to be
treated as case insensitive: there exist conventions for the
capitalization of some of the subtags, but these MUST NOT be taken to carry
meaning.</t>
<t>For example:
<list style="symbols">
<t>
<xref target="ISO639-1"/> recommends that language
codes be written in lowercase ('mn' Mongolian).</t>
<t>
<xref target="ISO3166-1"/>
recommends that country codes be capitalized ('MN' Mongolia).</t>
<t>
<xref target="ISO15924"/> recommends that script
codes use lowercase with the initial letter capitalized ('Cyrl' Cyrillic).</t>
</list>
</t>
<t>
However, in the tags defined by this document, the uppercase US-ASCII letters in the range 'A' through 'Z' are considered equivalent and mapped directly to their US-ASCII lowercase equivalents in the range 'a' through 'z'. Thus, the tag "mn-Cyrl-MN" is not
distinct from "MN-cYRL-mn" or "mN-cYrL-Mn" (or any other combination), and
each of these variations conveys the same meaning: Mongolian written in the
Cyrillic script as used in Mongolia.</t>
<t>Although case distinctions do not carry meaning in language tags, consistent formatting and presentation of the tags will aid users. The format of the tags and subtags in the registry is RECOMMENDED. In this format, all subtags, including all those following singletons (that is, in extension or private-use sequences) are in lowercase. The exceptions to this are: all other non-initial two-letter subtags are uppercase and all other non-initial four-letter subtags are titlecase. </t>
<t>Note that although <xref target="RFC5234"/> refers to octets,
the language tags described in this document are sequences of characters
from the US-ASCII <xref target="ISO646"/> 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 UTF-16LE <xref target="RFC2781"/> encoding of <xref target="Unicode"/>.</t>
</section>
<section anchor="sources" title="Language Subtag Sources and Interpretation">
<t>The namespace of language tags and their subtags is administered by the
Internet Assigned Numbers Authority (IANA) <xref target="RFC2860"/> according
to the rules in <xref target="iana"/> of this document. The Language Subtag Registry maintained
by IANA is the source for valid subtags: other standards referenced in this
section provide the source material for that registry.</t>
<t>Terminology used in this document:</t>
<t>
<list style="symbols">
<t>"Tag" refers to a complete language tag, such as "sr-Latn-RS" or "az-Arab-IR".
Examples of tags in this document are enclosed in double-quotes ("en-US").</t>
<t>"Subtag" refers to a specific section of a tag, delimited by hyphen, such
as the subtag 'Hant' in "zh-Hant-CN". Examples of subtags in this
document are enclosed in single quotes ('Hant').</t>
<t>"Code" refers to values defined in external standards (and which
are used as subtags in this document). For example,
'Hant' is an <xref target="ISO15924"/> script
code that was used to define the 'Hant' script subtag for use in
a language tag. Examples of codes in this document are enclosed in
single quotes ('en', 'Hant').</t>
</list>
</t>
<t>The definitions in this section apply to the various subtags within the
language tags defined by this document, excepting those "grandfathered"
tags defined in <xref target="preexisreg"/>.</t>
<t>Language tags are designed so that each subtag type has unique length and
content restrictions. These make
identification of the subtag's type possible, even if the content of
the subtag itself is unrecognized. This allows tags to be parsed and
processed without reference to the latest version of the underlying
standards or the IANA registry and makes the associated exception
handling when parsing tags simpler.</t>
<t>Subtags in the IANA registry that do not come from an underlying standard
can only appear in specific positions in a tag. Specifically, they can only
occur as primary language subtags or as variant subtags. </t>
<t>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.</t>
<t>Single-letter and single-digit subtags are reserved for current or future use.
These include the following current uses:</t>
<t>
<list style="symbols">
<t>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.</t>
<t>All other single-letter subtags are reserved to introduce standardized
extension subtag sequences as described in
<xref target="extensions"/>.</t>
<t hangText="Note: ">The single-letter subtag 'i' is used by some grandfathered
tags, such as "i-default", where it always appears in the first position and cannot be confused with an extension.</t>
</list>
</t>
<section anchor="primarylang" title="Primary Language Subtag">
<t>The primary language subtag is the first subtag in a language tag (with the exception of private use and certain grandfathered tags) and cannot be omitted.
The following rules apply to the primary language subtag:</t>
<t>
<list style="numbers">
<t>All two-character primary 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"
<xref target="ISO639-1"/>, or using
assignments subsequently made by the ISO 639-1 registration authority (RA)
or governing standardization bodies.</t>
<t>All three-character primary language subtags were defined in the IANA registry according
to the assignments found in either ISO 639 Part 2, "ISO 639-2:1998 - Codes for the representation of names of languages -- Part 2: Alpha-3 code - edition 1" <xref target="ISO639-2"/>, ISO 639 Part 3, "Codes for the representation of names of languages -- Part 3: Alpha-3 code for comprehensive coverage of languages" <xref target="ISO639-3"/>,
or assignments subsequently made by the relevant ISO 639
registration authorities or governing standardization bodies.</t>
<t>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
<xref target="privateuse"/> for more information on private use subtags.
</t>
<t>All four-character language subtags are reserved for possible future standardization.</t>
<t>All language subtags of 5 to 8 characters
in length in the IANA registry were defined via the registration process in
<xref target="registrationProc"/>
and MAY be used to form the primary language subtag.
At the time this document was created, there were no examples of
this kind of subtag and future registrations of this type will be
discouraged: primary languages are strongly RECOMMENDED for
registration with ISO 639, and proposals rejected by ISO 639/RA-JAC will be
closely scrutinized before they are registered with IANA.</t>
<t>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 <xref target="privateuse"/>.</t>
<t>The single-character subtag 'i' is used by some grandfathered tags (see <xref target="preexisreg"/>) such as "i-klingon" and "i-bnn". (Other grandfathered tags have a primary language subtag in their first position.)</t>
<t>Other values MUST NOT be assigned to the primary subtag except by
revision or update of this document.</t>
</list>
</t>
<t>Note: For languages that have both an ISO 639-1 two-character code
and a three character code assigned by either ISO 639-2 or ISO 639-3, only the ISO 639-1 two-character
code is defined in the IANA registry.</t>
<t>Note: For languages that have no ISO 639-1 two-character code and
for which the ISO 639-2/T (Terminology) code and the ISO 639-2/B
(Bibliographic) codes differ, only the Terminology code is defined in
the IANA registry.
At the time this document was created, all languages that
had both kinds of three-character
code were also assigned a two-character code; it is expected that
future assignments of this nature will not occur.</t>
<t>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 <xref target="iso639.prin"/>:<list>
<t>"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."</t>
</list>
</t>
<t>In order to avoid instability in the canonical form of tags, if a
two-character code is added to ISO 639-1 for a language for which a
three-character code was already included in either ISO 639-2 or ISO 639-3, the two-character code
MUST NOT be registered. See <xref target="ianastability"/>.</t>
<t>For example, if some content were tagged with
'haw' (Hawaiian), which currently has no two-character code, the tag
would not be invalidated if ISO 639-1 were to assign a two-character code
to the Hawaiian language at a later date.</t>
<t>Note: An example of independent primary language subtag registration might include: 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.
</t>
</section>
<section anchor="extlang" title="Extended Language Subtags">
<t>
<xref target="RFC4646"/> contained an additional type of subtag called the 'extended language subtag' to allow for certain kinds of compatibility mappings which ultimately were not used. These subtags were reserved for future use and ultimately removed from the ABNF. They MUST NOT be registered or used to form language tags. See also <xref target="conformance"/> for a discussion of the consequences of removing the 'extlang' production from grammar.</t>
<t>Note: a few grandfathered tags (<xref target="preexisreg"/>) matched the 'extlang' production in RFC 4646, and thus were not considered 'irregular'. These tags are still valid and were added to the 'irregular' production in the ABNF.</t>
</section>
<section anchor="script" title="Script Subtag">
<t>Script subtags are used to indicate the script or writing system variations that distinguish the written forms of a language or its dialects. The following rules apply to the script subtags:</t>
<t>
<list style="numbers">
<t>Script subtags MUST follow
the primary language subtag and
MUST precede any other type of subtag.</t>
<t>All four-character subtags were defined according to
<xref target="ISO15924"/>--"Codes for the representation
of the names of scripts": alpha-4 script codes, or subsequently
assigned by the ISO 15924 maintenance agency or governing
standardization bodies, denoting the script or writing system used in
conjunction with this language.</t>
<t>The script subtags 'Qaaa' through 'Qabx' are reserved for private use in
language tags. These
subtags correspond to codes reserved by ISO 15924 for private use.
These codes MAY be used for non-registered script values. Please refer to
<xref target="privateuse"/> for more information on private use subtags.</t>
<t>Script subtags MUST NOT be registered using the process in
<xref target="registrationProc"/> of this document. Variant subtags MAY be
considered for registration for that purpose.</t>
<t>There MUST be at most one script subtag in a language tag, and the script subtag SHOULD be omitted when it adds no distinguishing value to the tag or when the primary language subtag's record includes a Suppress-Script field listing the applicable script subtag.</t>
</list>
</t>
<t>Example: "sr-Latn" represents Serbian written using the Latin script.</t>
</section>
<section anchor="region" title="Region Subtag">
<t>Region subtags are used to indicate linguistic variations associated with or appropriate to a specific country, territory, or region. Typically, a region subtag is used to indicate regional dialects or usage, or region-specific spelling conventions. A region subtag can also be used to indicate that content is expressed in a way that is appropriate for use throughout a region, for instance, Spanish content tailored to be useful throughout Latin America. </t>
<t>The following rules apply to the region subtags:</t>
<t>
<list style="numbers">
<t>Region subtags MUST follow any
language or script subtags and MUST precede any other type of subtag.</t>
<t>All two-character subtags following the primary subtag were defined in the
IANA registry according to the assignments found in
<xref target="ISO3166-1"/> ("Codes for the representation of names of countries and their subdivisions -- Part 1: Country codes") using the list of alpha-2 country codes, or using assignments subsequently made
by the ISO 3166-1 maintenance agency or governing standardization bodies.
In
addition, the codes that are "exceptionally reserved" (as opposed to
"assigned") in ISO 3166-1 were also defined in the registry, with the
exception of 'UK', which is an exact synonym for the assigned code
'GB'.</t>
<t>All three-character subtags consisting of digit (numeric) characters following the primary subtag were
defined in the IANA registry according to the assignments found in
<xref target="UN_M.49">UN Standard Country or Area Codes for Statistical
Use</xref> or assignments subsequently made by the governing standards
body. Note that not all of the UN M.49 codes are defined in the IANA registry. The following rules define which codes are entered into the registry as valid subtags:<list style="letters">
<t>UN numeric codes assigned to 'macro-geographical
(continental)' or sub-regions MUST be registered in the registry. These codes are not associated with an assigned
ISO 3166-1 alpha-2 code and represent supra-national areas, usually covering more than one nation, state, province, or territory.</t>
<t>UN numeric codes for 'economic groupings' or 'other groupings' MUST NOT be
registered in the IANA registry and MUST NOT be used to form language tags.</t>
<t>UN numeric codes for countries or areas which are assigned ISO 3166-1 alpha2 codes already present in the registry, MUST be defined according to the rules in <xref target="ianastability"/> and MUST be used to form language tags that represent the country or region for which they are defined. This happens when ISO 3166-1 reassigns a code already included in the registry and formerly used for one country to another.</t>
<t>UN numeric codes for countries or areas for which there is an associated ISO 3166-1 alpha-2 code in the registry MUST NOT be entered into the registry and MUST NOT be used to form language tags. Note that the ISO 3166-based subtag in the registry MUST actually be associated with the UN M.49 code in question.</t>
<t>UN numeric codes and ISO 3166-1 alpha-2 codes for countries or areas listed as eligible for registration in <xref target="RFC4645"/> but not presently registered MAY be entered into the IANA registry via the process described in <xref target="registrationProc"/>. Once registered, these codes MAY be used to form language tags.</t>
<t>All other UN numeric codes for countries or areas that do not have an associated ISO 3166-1 alpha-2 code MUST NOT be entered into the registry and MUST NOT be used to form language tags. For more information about these codes, see <xref target="ianastability"/>.</t>
</list>
</t>
<t>Note: The alphanumeric codes in Appendix X of the UN document MUST NOT be entered into the registry
and MUST NOT be used to form language tags. (At the time this document was created, these values
matched the ISO 3166-1 alpha-2 codes.)</t>
<t>There MUST be at most one region subtag in a language tag and the region subtag MAY be omitted, as when it adds no distinguishing value to the tag.</t>
<t>The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ'
are reserved for private use in language
tags. These subtags correspond to codes reserved by ISO 3166 for private
use. These codes
MAY be used for private use region subtags (instead of using a private use
subtag sequence). Please refer to
<xref target="privateuse"/> for more information on private use subtags.</t>
</list>
</t>
<t hangText="Example: ">"de-AT" represents German ('de') as used in Austria ('AT').</t>
<t hangText="Example: ">"sr-Latn-RS" represents Serbian ('sr') written using
Latin script ('Latn') as used in Serbia ('RS').</t>
<t hangText="Example: ">"es-419" represents Spanish ('es') appropriate to the UN-defined
Latin America and Caribbean region ('419').</t>
</section>
<section anchor="variant" title="Variant Subtags">
<t>Variant subtags are used to indicate additional, well-recognized variations that define a language or its dialects that are not covered by other available subtags. The following rules apply to the variant subtags:</t>
<t>
<list style="numbers">
<t>Variant subtags MUST follow any language, script, or region subtags, but
MUST precede any extension or private use subtag sequences.</t>
<t>Variant subtags, as a collection, are not associated with any particular external standard. The meaning of variant subtags in the registry is defined in the course of the registration process defined in <xref target="registrationProc"/>. Note that any particular variant subtag might be associated with some external standard. However, association with a standard is not required for registration.</t>
<t>More than one variant MAY be used to form the language tag.</t>
<t>Variant subtags MUST be registered with IANA according to the rules in
<xref target="registrationProc"/> 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:
<list>
<t>Variant subtags that begin with a letter (a-z, A-Z) MUST be at
least five characters long.</t>
<t>Variant subtags that begin with a digit (0-9) MUST be at least
four characters long.</t>
</list>
</t>
<t>The same variant subtag MUST NOT be used more than once within a language tag.<list style="symbols">
<t>For example, the tag "de-DE-1901-1901" is not valid.</t>
</list>
</t>
</list>
</t>
<t hangText="Note: ">Variant subtag records in the language subtag registry MAY include one or more 'Prefix' fields. The 'Prefix' indicates the language tag or tags that would make a suitable prefix (with other subtags, as appropriate) in forming a language tag with the variant. That is, each of the subtags in the prefix SHOULD appear, in order, before the variant. For example, the subtag 'nedis' has a Prefix of "sl", making it suitable for forming language tags such as "sl-nedis" and "sl-IT-nedis", but not suitable for use in a tag such as "zh-nedis" or "it-IT-nedis".</t>
<t hangText="Example ">"sl-nedis" represents the Natisone or Nadiza dialect of Slovenian.</t>
<t hangText="Example ">"de-CH-1996" represents German as used in Switzerland
and as written using the spelling reform beginning in the year 1996 C.E.</t>
<t hangText="Note: ">Most variants that share a prefix are mutually exclusive. For example, the German orthographic variations '1996' and '1901' SHOULD NOT be used in the same tag, as they represent the dates of different spelling reforms. A variant that can meaningfully be used in combination with another variant SHOULD include a 'Prefix' field in its registry record that lists that other variant. For example, if another German variant 'example' were created that made sense to use with '1996', then 'example' should include two Prefix fields: "de" and "de-1996".</t>
</section>
<section anchor="extensionsubt" title="Extension Subtags">
<t>Extensions provide a mechanism for extending language tags for use in various applications. They are intended to identify information which is commonly used in association with languages or language tags, but which is not part of language identification. See <xref target="extensions"/>. The following rules apply to extensions:</t>
<t>
<list style="numbers">
<t>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.</t>
<t>Extension subtags are separated from the other subtags defined in
this document by a single-character subtag ("singleton"). The singleton
MUST be one allocated to a registration authority via the
mechanism described
in <xref target="extensions"/> and MUST NOT be the letter 'x', which
is reserved for private use subtag sequences.</t>
<t>Note: Private use subtag sequences starting with the singleton
subtag 'x' are described in <xref target="privateusesubt"/> below.</t>
<t>Each singleton subtag MUST appear at most one time in each tag (other than
as a private use subtag). That is,
singleton subtags MUST NOT be repeated. For example, the tag
"en-a-bbb-a-ccc" is invalid because the subtag 'a' appears twice. Note that the tag "en-a-bbb-x-a-ccc" is valid because the second appearance of the singleton 'a' is in a private use sequence.</t>
<t>Extension subtags MUST meet all of the requirements for the content
and format of subtags defined in this document.</t>
<t>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.</t>
<t>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 '-'.</t>
<t>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'.</t>
<t>Extension subtags MUST follow all language, script,
region, and variant subtags in a tag.</t>
<t>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'.</t>
<t>In the event that more than one extension appears in a single tag, the
tag SHOULD be canonicalized as described in <xref target="canonical"/>.</t>
</list>
</t>
<t>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"</t>
</section>
<section anchor="privateusesubt" title="Private Use Subtags">
<t>Private use subtags are used to indicate distinctions in language important in a given context by private agreement. The following rules apply to private use subtags:</t>
<t>
<list style="numbers">
<t>Private use subtags are separated from the other subtags
defined in this document by the reserved single-character subtag 'x'.</t>
<t>Private use subtags MUST conform to the format and content constraints defined in the ABNF for all subtags.</t>
<t>Private use subtags MUST follow all 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.</t>
<t>A tag MAY consist entirely of private use
subtags.</t>
<t>No source is defined for private use subtags. Use of private use
subtags is by private agreement only.</t>
<t>Private use subtags are NOT RECOMMENDED where alternatives exist or for general interchange. See <xref target="privateuse"/> for more information on private use subtag choice.</t>
</list>
</t>
<t> For example: The Unicode Consortium defines a set of private
use extensions in LDML (<xref target="UTS35"/>, Locale Data
Markup Language, the Unicode standard for defining locale data) such as
in the tag "es-419-x-ldml-collation-traditio", which indicates Latin
American Spanish with traditional order for sorted lists.</t>
</section>
<section anchor="preexisreg" title="Grandfathered Registrations">
<t>Prior to RFC 4646, whole language tags were registered according to the rules in RFC 1766 and/or RFC 3066. These registered tags maintain their validity. Of those tags, those that were made obsolete or redundant by the advent of RFC 4646, by this document, or by subsequent registration of subtags are maintained in the registry in records as "redundant" records. Those tags that do not match the 'langtag' production in the ABNF in this document or that contain subtags that do not individually appear in the registry are maintained in the registry in records of the "grandfathered" type. </t>
<t>Grandfathered tags contain one or more subtags that are not defined in the Language Subtag Registry (see <xref target="registry"/>). Redundant tags consist entirely of subtags defined above and whose independent registration was superseded by <xref target="RFC4646"/>. For
more information see <xref target="ianaconversion"/>.</t>
<t>Some grandfathered tags are "regular" in that they match the 'langtag' production in <xref target="ABNF"/>. In some cases, these tags could become redundant if their (currently unregistered) subtags were to be registered (as variants, for example). In other cases, although the subtags match the language tag pattern, the meaning assigned to the various subtags is prohibited by rules elsewhere in this document. Those tags can never become redundant.</t>
<t>The remaining grandfathered tags are "irregular" and do not match the 'langtag' production. These are listed in the 'irregular' production in <xref target="ABNF"/>. These grandfathered tags can never become redundant. Many of these tags have been superseded by other registrations: their record contains a Preferred-Value field that really ought to be used to form language tags representing that value.</t>
</section>
<section title="Classes of Conformance" anchor="conformance">
<t>Implementations sometimes need to describe their capabilities with regard to the rules and practices described in this document. Tags can be checked or verified in a number of ways, but two particular classes of tag conformance are formally defined here.</t>
<t>A tag is considered "well-formed" if it conforms to the <xref target="syntax">ABNF</xref>. Note that irregular grandfathered tags are now listed in the 'irregular' production. </t>
<t>A tag is considered "valid" if it satisfies these conditions:<list style="symbols">
<t>The tag is well-formed.</t>
<t>The tag is either a grandfathered tag, or all of its language, script, region, and variant subtags appear in the IANA language subtag registry as of the particular registry date.</t>
<t>There are no duplicate singleton (extension) subtags and no duplicate variant subtags.</t>
</list>
</t>
<t>Note that a tag's validity depends on the date of the registry used to validate the tag. A more recent copy of the registry might contain a subtag that an older version does not.</t>
<t>A tag is considered "valid" for a given <xref target="extensions">extension</xref> (as of a particular version, revision, and date) if it meets the criteria for "valid" above and also satisfies this condition:<list>
<t>Each subtag used in the extension part of the tag is valid according to the extension.</t>
</list>
</t>
<t>Some older implementations consider a tag "well-formed" if it matches the ABNF in <xref target="RFC4646"/>. In that version, a well-formed tag could contain a sequence matching the obsolete 'extlang' production. Other than a few grandfathered tags (which are handled separately), no valid tags have ever matched that pattern. The difference between that ABNF and <xref target="ABNF"/> is that the language production is replaced as follows:</t>
<figure anchor="obsolete.abnf" title="Obsolete Language ABNF">
<artwork name="altlang">
obs-primary-language = (2*3ALPHA [ extlang ]) ; shortest ISO 639 code
/ 4ALPHA ; reserved for future use
/ 5*8ALPHA ; registered language subtag
extlang = *3("-" 3ALPHA) ; removed in this version </artwork>
</figure>
<t>Older language tag implementations sometimes reference <xref target="RFC3066"/>. Again, all valid tags under that version also match this document's language tag ABNF. However, a wider array of tags could be considered "well-formed" under that document. The 'Language-Tag' production used in that document matches the following:</t>
<figure anchor="rfc3066abnf" title="RFC 3066 Language Tag Syntax">
<artwork name="rfc3066.abnf">
obs-language-tag = primary-subtag *( "-" subtag )
primary-subtag = 1*8ALPHA
subtag = 1*8(ALPHA / DIGIT)</artwork>
</figure>
<t>Language tags may be well-formed in terms of syntax but not valid in terms of content. Users MUST NOT assign and use their own subtags, other than private-use sequences (such as "en-x-personal") or by using subtags designated as private-use in the registry (such as "no-QQ", where 'QQ' is one of a range of private-use ISO 3166-1 codes). Not only is such assignment nonconformant, it also risks collision with a future possible assignment. The private use subtags and sequences are designed for this case.</t>
</section>
</section>
</section>
<section title="Registry Format and Maintenance" anchor="registry">
<t>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 (<xref target="extensions"/>).</t>
<t>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.)</t>
<section anchor="ianaformat" title="Format of the IANA Language Subtag Registry">
<t>The IANA Language Subtag Registry ("the registry") is a
machine-readable file in the format described in this section, plus copies of the
registration forms approved in accordance with
the process described in <xref target="registrationProc"/>. </t>
<t>Note: The existing registration forms for grandfathered and redundant tags taken from RFC 3066 have been maintained as part of the obsolete RFC 3066 registry. The subtags added to the registry by either <xref target="RFC4645"/> or <xref target="registry-update"/> do not have separate registration forms (so no forms are archived for these additions).</t>
<section title="File Format" anchor="fileformat">
<t>The registry consists of a series of records stored in the record-jar format (described in <xref target="record-jar"/>). Each record, in turn, consists of a series of fields that describe the various subtags and tags. The registry is a <xref target="Unicode">Unicode</xref> text file, using the <xref target="RFC3629">UTF-8</xref> character encoding.</t>
<t> Each field can be considered a single, logical line of <xref target="Unicode">Unicode</xref> characters, comprising a field-name and a field-body separated by a COLON character (%x3A).
Each field is terminated by the newline sequence CRLF. The text in each field MUST be in Unicode Normalization Form C (NFC).</t>
<t>A collection of fields forms a 'record'. Records are separated by lines containing only the sequence "%%" (%x25.25). </t>
<t>Although fields are logically a single line of text, each line of text in the file format is limited to 72 bytes in length. To accommodate this, the field-body can be split into a multiple-line representation; this
is called "folding". Folding is done according to customary conventions for line-wrapping.
This is typically on whitespace boundaries, but can occur between
other characters when the value does not include spaces, such as when a language does not use whitespace between
words. In any event, there MUST NOT be breaks inside a multibyte
UTF-8 sequence nor in the middle of a combining character sequence.
For more information, see <xref target="UAX14"/>.</t>
<t>Although the file format uses the UTF-8 encoding, unless otherwise indicated, fields are restricted to the printable characters from the <xref target="ISO646">US-ASCII</xref> repertoire.</t>
<t>The format of the registry is described by the following ABNF (per <xref target="RFC5234"/>): </t>
<figure title="Registry Format ABNF" anchor="record-jar-fig">
<artwork type="ABNF" name="record-jar">
registry = record *("%%" CRLF record)
record = 1*( field-name *SP ":" *SP field-body CRLF )
field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)]
field-body = *([[*SP CRLF] 1*SP] 1*CHARS)
CHARS = (%x21-10FFFF) ; Unicode code points
</artwork>
</figure>
<t>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 '13'.</t>
<t>All fields whose field-body contains a date value use the "full-date" format specified in <xref target="RFC3339"/>. For example: "2004-06-28" represents June 28, 2004, in the Gregorian
calendar.</t>
</section>
<section anchor="recordformat" title="Record Definitions">
<t>There are three types of records in the registry: "File-Date", "Subtag", and "Tag" records.</t>
<t>The first record in the registry is a "File-Date" record. This record contains the single field whose field-name is "File-Date" (see <xref target="record-jar-fig"/>). 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.
</t>
<figure anchor="file-date-fig" title="Example of the File-Date Record">
<artwork name="daterecord">
File-Date: 2004-06-28
%%</artwork>
</figure>
<t>Subsequent records represent either subtags or tags in the registry. "Subtag" records contain a field with a field-name of "Subtag", while, unsurprisingly, "Tag" records contain a field with a field-name of "Tag". Each of the fields in each
record
MUST occur no more than once, unless otherwise noted below.
Each record MUST contain the following fields:<list style="symbols">
<t>'Type'<list>
<t>Type's field-body MUST consist of one of the following strings: "language",
"script", "region", "variant", "grandfathered", and "redundant"
and denotes the type of tag or subtag.</t>
</list>
</t>
<t>Either 'Subtag' or 'Tag'<list>
<t>Subtag's field-body contains the subtag being defined. This field MUST only appear in records of whose 'Type' has one of these values: "language", "script", "region", or "variant".</t>
<t>Tag's field-body 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-body will always follow the 'grandfathered' production in the ABNF in <xref target="syntax"/>
</t>
</list>
</t>
<t>Description<list>
<t>Description's field-body contains a non-normative description of the subtag
or tag.</t>
</list>
</t>
<t>Added<list>
<t>Added's field-body contains the date the record was added to the registry.</t>
</list>
</t>
</list>
</t>
<t>Each record MAY also contain the following fields:<list style="symbols">
<t>Preferred-Value<list>
<t>For fields of type 'script', 'region', and 'variant', 'Preferred-Value' contains the subtag of the same 'Type' that is preferred for forming the language tag.</t>
<t>For fields of type 'language', 'Preferred-Value' contains the primary language subtag that is preferred when forming the language tag.</t>
<t>For fields of type 'grandfathered' and 'redundant', 'Preferred-Value' contains a canonical mapping to a complete language tag.</t>
</list>
</t>
<t>Deprecated<list>
<t>The field-body of the Deprecated field contains the date the record was deprecated.</t>
</list>
</t>
<t>Prefix<list>
<t>Prefix's field-body contains a language tag with which this subtag MAY be used to form a new language tag,
perhaps with other subtags as well. The Prefix's subtags appear before the subtag. This field MUST only appear in records whose 'Type' field-body is 'variant'. For example, the 'Prefix' for the variant 'nedis' is 'sl', meaning that the tags "sl-nedis" and "sl-IT-nedis" are appropriate while the tag "is-nedis" is not.</t>
</list>
</t>
<t>Comments<list>
<t>Comments contains additional information about the subtag, as
deemed appropriate for understanding the registry and implementing language
tags using the subtag or tag.</t>
</list>
</t>
<t>Suppress-Script<list>
<t>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-body is 'language'. See <xref target="choice"/>.</t>
</list>
</t>
<t>Macrolanguage<list>
<t>Macrolanguage contains a primary language subtag defined by ISO 639 as a "macrolanguage" that encompasses this language subtag. This field MUST only appear in records whose 'Type' field-body is 'language'.</t>
</list>
</t>
</list>
</t>
<t>Future versions of this document might add additional fields to the
registry, so implementations SHOULD ignore fields found in the registry
that are not defined in this document.</t>
</section>
<section anchor="subtagfield" title="Subtag and Tag Fields">
<t>The 'Subtag' field MUST NOT use uppercase letters to form the subtag, 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, the non-numeric region subtags defined by ISO 3166-1) MUST use all uppercase. These exceptions mirror the use of case in the underlying standards.</t>
<t>Each subtag in the tags contained in a 'Tag' field MUST be formatted using the rules in the preceding paragraph. That is, all subtags are lowercase except for subtags that represent script or region codes.</t>
</section>
<section anchor="descriptionfield" title="Description Field">
<t>The field 'Description' contains a description of the tag or subtag in the record. The 'Description' field MAY appear more than once per record, that is, there can be multiple descriptions for a given record. The 'Description' field MAY include the full range of Unicode characters. At least one of the 'Description' fields MUST be written or transcribed into the Latin script; additional 'Description' fields MAY also include a description in a non-Latin script. Each 'Description' field MUST be unique, both within the record in which it appears and for the collection of records of the same type. Moreover, formatting variations of the same description MUST NOT occur in that specific record or in any other record of the same type. For example, while the ISO 639-1 code 'fy' contains both the descriptions "Western Frisian" and "Frisian, Western", only one of these descriptions appears in the registry.</t>
<t>The 'Description' field is used for identification purposes. It doesn't necessarily represent the actual native name of the item in the record, nor are any of the descriptions guaranteed to be in any particular language (such as English or French, for example).</t>
<t>For subtags taken from a source standard (such as ISO 639 or ISO 15924), the 'Description' value(s) SHOULD also be taken from the source standard. Multiple descriptions in the source standard MUST be split into separate 'Description' fields. The source standard's descriptions MAY be edited, either prior to insertion or via the registration process. For fields of type 'language', the first 'Description' field appearing in the Registry
corresponds to the Reference Name assigned by ISO 639-3. This helps facilitate
cross-referencing between ISO 639 and the registry. </t>
<t>When creating or updating a record due to the action of one of the source standards, the Language Subtag Reviewer SHOULD remove duplicate or redundant descriptions and MAY edit descriptions to correct irregularities in formatting (such as misspellings, inappropriate apostrophes or other punctuation, or excessive or missing spaces) prior to submitting the proposed record to the ietf-languages list.</t>
<t>Note: Descriptions in
registry entries that correspond to ISO 639, ISO 15924, ISO 3166-1, 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 localized English names
for the subtags. Localization or translation of language tag and subtag descriptions is out of scope
of this document.</t>
<t>Descriptions SHOULD contain all and only that information necessary
to distinguish one subtag from others that it might be confused with.
They are not intended to provide general background information,
nor to provide all possible alternate names or designations.</t>
</section>
<section anchor="deprecatedfield" title="Deprecated Field">
<t>The field 'Deprecated' MAY be added, changed, or removed from any record via the maintenance process described in <xref target="maintreg"/> or via the registration process described in <xref target="registrationProc"/>. 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.</t>
</section>
<section anchor="preferredfield" title="Preferred-Value Field">
<t>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 groups:<list style="numbers">
<t>ISO 639 language codes that were later withdrawn in favor of other codes. These values are mostly a historical curiosity.</t>
<t>Codes that have been withdrawn in favor of a new code. In particular, this applies to region subtags taken from ISO 3166-1, because sometimes a country will change its name or administration in such a way that warrants a new region code. In some cases, countries have reverted to an older name, which might already be encoded.</t>
<t>Tags or subtags that have become obsolete because the values they represent were later encoded. Many of the grandfathered or redundant tags were later encoded by ISO 639, for example, and fit this pattern.</t>
</list>
</t>
<t>Records that contain a 'Preferred-Value' field MUST also have a 'Deprecated' field. This field contains the date on which the tag or subtag was deprecated in favor of the preferred value.</t>
<t>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.</t>
<t>The field MAY be added, changed, or removed from records according to the rules in <xref target="maintreg"/>. Addition, modification, or removal of a 'Preferred-Value' field in a record does not imply that content using the affected subtag needs to be retagged.</t>
<t>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, these mappings were created via deprecation of the tags during the period before <xref target="RFC4646"/> was adopted. For example, the tag "no-nyn" was deprecated in favor of the ISO 639-1-defined language code 'nn'. </t><t>Usually the addition, removal, or change of a Preferred-Value field for a
subtag is done to reflect changes in one of the source standards. For example, if an ISO 3166-1 region code is deprecated in favor of
another code, that SHOULD result in the addition of a Preferred-Value field.
</t><t>Changes to one subtag MAY affect other subtags as well: when proposing changes to the registry, the Language Subtag Reviewer will review the registry for such effects and propose the necessary changes using the process in <xref target="registrationProc"></xref>, although anyone MAY request such changes. For example:<list>
<t>Suppose that subtag 'XX' has a Preferred-Value of 'YY'. If 'YY' later changes to
have a Preferred-Value of 'ZZ', then the Preferred-Value for 'XX' MUST also change
to be 'ZZ'.</t>
<t>Suppose that a variant subtag 'dialect' represents a language not
yet available in any part of ISO 639. The later addition of a corresponding language
code in ISO 639 SHOULD result in the addition of a Preferred-Value for
'dialect'.</t>
</list>
</t>
</section>
<section anchor="prefixfield" title="Prefix Field">
<t>The 'Prefix' field contains an extended language range whose subtags are appropriate to use with this subtag: each of the subtags in one of the subtag's Prefix fields SHOULD appear before the variant in a valid tag. 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.</t>
<t>The field of type 'Prefix' MUST NOT be removed from any record. The field-body for this type of field MAY be modified, but only if the modification broadens the meaning of the subtag. That is, the field-body can be replaced only by a prefix of itself. For example, the Prefix "be-Latn" (Belarusian, Latin script) could be replaced by the Prefix "be" (Belarusian) but not by the Prefix "ru-Latn" (Russian, Latin script).</t>
<t>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.
</t>
<t>The field-body of the 'Prefix' field MUST NOT conflict with any 'Prefix' already registered for a given record. Such a conflict would occur when no valid tag could be constructed that would contain the prefix, such as when two subtags each have a 'Prefix' that contains the other subtag. For example, suppose that the subtag 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' cannot given the prefix 'avariant', for that would require a tag of the form "es-avariant-bvariant-avariant", which would not be valid.</t>
</section>
<section anchor="suppressfield" title="Suppress-Script Field">
<t>The field 'Suppress-Script' contains a script subtag (whose record appears in the registry). The field 'Suppress-Script' MUST only appear in records whose 'Type' field-body 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. This script code therefore adds no distinguishing information to a language tag. This helps ensure greater compatibility between the language tags generated according to the rules in this document and language tags and tag processors or consumers based on RFC 3066 by indicating that the script subtag SHOULD NOT be used for most documents in that language. For example, virtually all Icelandic documents are written in the Latin script, making the subtag 'Latn' redundant in the tag "is-Latn".</t>
<t>Many language subtag records do not have a Suppress-Script field. The
lack of a Suppress-Script might indicate that the language is
customarily written in more than one script or that the language is not
customarily written at all. It might also mean that sufficient
information was not available when the record was created and thus remains a candidate for future registration.</t>
</section>
<section title="Macrolanguage Field" anchor="macrolang">
<t>The Macrolanguage field contains a primary language subtag that encompasses this subtag's language. That is, the language subtag whose record this field appears in is sometimes considered to be a sub-language of the Macrolanguage. Macrolanguage values are defined by ISO 639-3 and the exact nature of the relationship between the encompassed and encompassing languages varies on a case-by-case basis. </t>
<t>This field can be useful to applications or users when selecting language tags or as additional metadata useful in matching. The Macrolanguage field can only occur in records of type 'language'. Only values assigned by ISO 639-3 will be considered for inclusion. Macrolanguage fields MAY be added or removed via the normal registration process whenever ISO 639-3 defines new values or withdraws old values. Macrolanguages are informational, and MAY be removed or changed if ISO 639-3 changes the values.</t>
<t>For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' (Norwegian). For more information see <xref target="choice"/>.</t>
</section>
<section anchor="commentsfield" title="Comments Field">
<t>The field 'Comments' conveys additional information about the record and MAY appear more than once per record. The field-body MAY include the full range of Unicode characters and is not restricted to any particular script. This field MAY be inserted or changed via the registration
process and no guarantee of stability is provided.</t>
<t>The content of this field is not restricted, except by the need to register the information, the suitability of the request, and by reasonable practical size limitations. The primary reason for the Comments field is subtag identification: to help
distinguish the subtag from others with which it might be confused. In
particular, large amounts of information about the use, history, or
general background of a subtag are frowned upon as these generally
belong and are encouraged in registration request forms themselves, but do not belong
in the registry record proper.</t>
</section>
</section>
<section anchor="subtagreviewer" title="Language Subtag Reviewer">
<t>The Language Subtag Reviewer moderates the ietf-languages mailing list, responds to requests for registration, and performs the other registry maintenance duties described in <xref target="maintreg"/>. Only the Language Subtag Reviewer is permitted to request IANA to change, update, or add records to the Language Subtag Registry. The Language Subtag Reviewer MAY delegate list moderation and other clerical duties as needed. </t>
<t>The Language Subtag Reviewer is appointed by the IESG for an indefinite term, subject to removal or replacement at the IESG's discretion. The IESG will solicit nominees for the position (upon adoption of this
document or upon a vacancy) and then solicit feedback on the nominees'
qualifications.
Qualified candidates should be familiar with BCP 47 and its requirements; be
willing to fairly, responsively, and judiciously administer the registration
process; and be suitably informed about the issues of language
identification so that the reviewer can assess the claims and
draw upon the contributions of language experts and subtag requesters.</t>
<t>The subsequent performance or decisions of the Language Subtag Reviewer MAY be appealed to the IESG under the same rules as other IETF decisions (see <xref target="RFC2026"/>). The IESG can reverse or overturn the decisions of the Language Subtag Reviewer, provide guidance, or take other appropriate actions.</t>
</section>
<section title="Maintenance of the Registry" anchor="maintreg">
<t>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 and determine the appropriate course of action according to the rules in this document. Such updates follow the registration process described in <xref target="registrationProc"/>. Usually the Language Subtag Reviewer will start the process for the new or updated record by filling in the registration form and submitting it. If a change to one of these standards takes place and the Language Subtag Reviewer does not do this in a timely manner, then any interested party MAY submit the form. Thereafter the registration process continues normally. </t><t>Note that some registrations affect other subtags--perhaps more than one--as when a region subtag is being deprecated in favor of a new value. The Language Subtag Reviewer is responsible for ensuring that any such changes are properly registered, with each change requiring its own registration form.</t>
<t>The Language Subtag Reviewer MUST ensure that new subtags meet the requirements
elsewhere in this document (and most especially in <xref target="ianastability"/>) or submit an appropriate registration form for an alternate subtag as described
in that section. Each individual subtag affected by a change MUST be sent to the ietf-languages list with its own registration form and in a separate message.</t>
</section>
<section anchor="ianastability" title="Stability of IANA Registry Entries">
<t>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. </t>
<t>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:
<list style="numbers">
<t>Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST
NOT be changed and are guaranteed to be stable over time.</t><t>Values in the fields 'Preferred-Value' and 'Deprecated' MAY be added, altered, or removed via the registration process. These changes SHOULD be limited to changes necessary to mirror changes in one of the underlying standards (ISO 639, ISO 15924, ISO 3166-1, or UN M.49) and typically alteration or removal of a Preferred-Value is limited specifically to region codes.</t>
<t>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 names; a historical example of this would be "Upper Volta" changing to "Burkina Faso".</t>
<t>Values in the field 'Prefix' MAY be added to records of type 'variant' via the registration process. If a prefix is added to a variant record, 'Comment' fields SHOULD be used to explain different usages with the various prefixes.</t>
<t>Values in the field 'Prefix' in records of type 'variant' 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.</t>
<t>Values in the field 'Prefix' MUST NOT be removed.</t>
<t>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.</t>
<t>The field 'Suppress-Script' MAY be added or removed via the registration process.</t>
<t>The field 'Macrolanguage' MAY be added or removed via the registration process, but only in response to changes made by ISO 639. The Macrolanguage field appears whenever a language has a corresponding Macrolanguage in ISO 639. That is, the macrolanguage fields in the registry exactly match those of ISO 639. No other macrolanguage mappings will be considered for registration. </t>
<t>Codes assigned by ISO 639-1 that do not conflict with existing two-letter primary language subtags and which have no corresponding three-letter primary defined in the registry are entered into the IANA registry as new records of type 'language'.</t>
<t>Codes assigned by ISO 639-2 that do not conflict with existing three-letter primary language subtags are entered into the IANA registry as new records of type 'language'.</t>
<t>Codes assigned by ISO 639-3 that do not conflict with existing three-letter primary language subtags are entered into the IANA registry as new primary language records. </t>
<t>Codes assigned by ISO 15924 and ISO 3166-1 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.</t>
<t>Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are withdrawn by their respective maintenance or registration authority remain valid in language tags. A 'Deprecated' field containing the date of withdrawal MUST be added to the record. If a new record of the same type is added that represents a replacement value, then a 'Preferred-Value' field MAY also be added. The registration process MAY be used to add comments about the withdrawal of the code by the respective standard.
<list style="hanging">
<t hangText="Example">The region code 'TL' was assigned to the country 'Timor-Leste', replacing the code 'TP' (which was assigned to 'East Timor' when it was under administration by Portugal). The subtag 'TP' remains valid in language tags, but its record contains the a 'Preferred-Value' of 'TL' and its field 'Deprecated' contains the date the new code was assigned ('2004-07-06').</t>
</list>
</t>
<t>Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 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:
<list style="letters">
<t>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 <xref target="registrationProc"/>, 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.</t>
<t>For all subtags whose meaning is derived from an external standard (that is, by ISO 639, ISO 15924, ISO 3166-1, 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.</t>
<t>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 <xref target="registrationProc"/>, 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.</t>
<t>For ISO 3166-1 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 3166-1 code.</t>
<t>For ISO 3166-1 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 <xref target="registrationProc"/>, SHALL prepare a proposal for entering the appropriate UN M.49 country code as an entry in the IANA registry. </t>
<t>For ISO 3166-1 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.</t>
</list>
</t>
<t>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 3166-1 code SHOULD NOT be registered, except as a surrogate for an ISO 3166-1 code that is blocked from registration by an existing subtag. If such a code becomes necessary, then the registration authority for ISO 3166-1 SHOULD first be petitioned to assign a code to the region. If the petition for a code assignment by ISO 3166-1 is refused
or not acted on in a timely manner, the registration process described in <xref target="registrationProc"/> MAY then be used to register the corresponding UN M.49 code. This way, UN M.49 codes remain available as the value of last resort in cases where ISO 3166-1 reassigns a deprecated value in the registry.</t>
<t>Stability provisions apply to grandfathered tags with this exception:
should it become possible to compose one of the grandfathered tags from registered subtags,
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, the variant subtag '1901' is registered, making the formerly-grandfathered tags such as "de-1901" and "de-AT-1901" redundant as a result. Of course,
these tags, where applied to existing content or in existing implementations, remain valid (all of their subtags are in the registry, after all), while new tags or applications using these subtags become possible.</t>
</list>
</t>
<t>Note: The redundant and grandfathered entries together are the complete list of tags registered under <xref target="RFC3066"/>. The redundant tags are those that can now be formed using the subtags defined in the registry together with the rules of <xref target="sources"/>. The grandfathered entries include those that can never be legal under those same provisions plus those tags that contain subtags not yet registered or, perhaps, inappropriate for registration. </t>
<t>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 <xref target="possibleReg"/> for more information. The decision-making process about which tags were initially grandfathered and which were made redundant is described in <xref target="RFC4645"/>.</t>
<t>RFC 3066 tags that were deprecated prior to the adoption of <xref target="RFC4646"/> 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'.</t>
</section>
<section anchor="registrationProc" title="Registration Procedure for Subtags">
<t>The procedure given here MUST be used by anyone who wants to use a subtag not currently in the IANA Language Subtag Registry.</t>
<t>Only subtags of type 'language' and 'variant' will be considered for independent
registration of new subtags. 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 also use this process, as described in <xref target="maintreg"/>. Stability provisions are described in
<xref target="ianastability"/>.</t>
<t>This procedure MAY also be used to register or alter the information for the 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value', or 'Suppress-Script' fields in a subtag's record as described in <xref target="ianastability"/>. Changes to all other fields in the IANA
registry are NOT permitted.</t>
<t>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 <xref target="ianaformat"/>.<figure anchor="regform.fig" title="The Language Subtag Registration Form">
<artwork>
LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester:
2. E-mail address of requester:
3. Record Requested:
Type:
Subtag:
Description:
Prefix:
Preferred-Value:
Deprecated:
Suppress-Script:
Macrolanguage:
Comments:
4. Intended meaning of the subtag:
5. Reference to published description
of the language (book or article):
6. Any other relevant information:
</artwork>
</figure>
</t>
<t>Examples of completed registration forms can be found in <xref target="regexamples"/> or online at <eref target="http://www.iana.org/assignments/lang-subtags-templates/">http://www.iana.org/assignments/lang-subtags-templates/</eref>.</t>
<t>The subtag registration form MUST be sent to <ietf-languages@iana.org> for
a two-week review period before it can be submitted to IANA. If modifications are made to the request during the course of the registration process (such as corrections to meet the requirements in <xref target="ianaformat"/>) the modified form MUST also be sent to <ietf-languages@iana.org> at least one week prior to submission to IANA.</t>
<t>The ietf-languages list is an open list and can be joined by sending a request to <ietf-languages-request@iana.org>. The list can be hosted by IANA or by any third party at the request of IESG.</t>
<t>Before forwarding a new registration to IANA, the Language Subtag Reviewer MUST ensure that all requirements in this document are met and that values in the 'Subtag' field match case according to the description in <xref target="ianaformat"/>. The Reviewer MUST also ensure that an appropriate File-Date record is included in the request, to assist IANA when updating the registry (see <xref target="iana-subtag-reg"></xref>).</t>
<t>Some fields in both the registration form as well as the registry record itself permit the use of non-ASCII characters. Registration requests SHOULD use the UTF-8 encoding for consistency and clarity. However, since some mail clients do not support this encoding, other encodings MAY be used for the registration request. The Language Subtag Reviewer is responsible for ensuring that the proper Unicode characters appear in both the archived request form and the registry record. In the case of a transcription or encoding error by IANA, the Language Subtag Reviewer will request that the registry be repaired, providing any necessary information to assist IANA.</t>
<t>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.</t>
<t>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.</t>
<t>Requests to add a prefix to a
variant subtag that imply a different semantic meaning SHOULD 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.</t>
<t>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. 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.</t>
<t>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 <xref target="ianastability"/>.</t>
<t>When the two-week period has passed, the Language Subtag Reviewer MUST take one of the following actions:<list style="symbols">
<t>Explicitly accept the request and forward the form containing the record to be inserted or modified to iana@iana.org according to the procedure described in <xref target="maintreg"/>.</t>
<t>Explicitly
reject the request because of significant objections raised on the list or due to
problems with constraints in this document (which MUST be explicitly cited).</t>
<t>Extend the review period by granting an additional two-week increment to permit further discussion. After each two-week increment, the Language Subtag Reviewer MUST indicate on the list whether the registration has been accepted, rejected, or extended.</t>
</list>
</t>
<t>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.</t>
<t>Sometimes the request needs to be modified as a result of discussion during the review period or due to requirements in this document. The applicant, Language Subtag Reviewer, or others are free to submit a modified version of the completed registration form, which will be considered in lieu of the original request with the explicit approval of the applicant. Such changes do not restart the two-week discussion period, although an application containing the final record submitted to IANA MUST appear on the list at least one week prior to the Language Subtag Reviewer forwarding the record to IANA. The applicant is also free to modify a rejected application with additional information and submit it again; this starts a new two-week comment period.</t>
<t>Registrations initiated due to the provisions of <xref target="maintreg"/> or <xref target="ianastability"/> SHALL NOT be rejected altogether (since they have to ultimately appear in the registry) and SHOULD be completed as quickly as possible. The review process allows list members to comment on the specific information in the form and the record it contains and thus help ensure that it is correct and consistent. The Language Subtag Reviewer MAY reject a specific version of the form, but MUST include in the rejection a suitable replacement, extending the review period as described above, until the form is in a format worthy of reviewer's approval.</t>
<t>Decisions made by the Language Subtag Reviewer MAY be appealed to the IESG
<xref target="RFC2028"/> under the same rules as other IETF
decisions <xref target="RFC2026"/>.
This includes a decision to extend the review period or the failure to announce a decision in a clear and timely manner.</t>
<t>The approved records appear in the Language Subtag Registry. The approved registration forms are available online under <eref target="http://www.iana.org/assignments/lang-subtags-templates/">http://www.iana.org/assignments/lang-subtags-templates/</eref>.</t>
<t>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.</t>
<t>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.</t>
<t>Note: The purpose of the "Reference to published description" section in the
registration form is to aid in verifying 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.
</t>
</section>
<section anchor="possibleReg" title="Possibilities for Registration">
<t>Possibilities for registration of subtags or information about subtags include:</t>
<t>
<list style="symbols">
<t>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 languages defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, or that are
under consideration by the ISO 639 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 as a primary language subtag in the IANA registry (to the extent that
it is very unlikely that any subtags will be registered of this type).</t>
<t>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).</t>
<t>The addition or maintenance of fields (generally of an informational nature) in Tag or Subtag records as described in <xref target="ianaformat"/> and subject to the stability provisions in <xref target="ianastability"/>. This includes descriptions, comments, deprecation and preferred values for obsolete or withdrawn codes, or the addition of script or macrolanguage information to primary language subtags.</t>
<t>The addition of records and related field value changes necessary to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and UN M.49 as described in <xref target="ianastability"/>.</t>
</list>
</t>
<t hangText="Note: ">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.</t>
<t>This document leaves the decision on what subtags or changes to subtags are appropriate (or not) to the
registration process described in <xref target="registrationProc"/>.</t>
<t>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.</t>
<t>ISO 639 defines a maintenance agency for additions to and changes in the list of
languages in ISO 639. This agency is:</t>
<t>International Information Centre for Terminology (Infoterm)<vspace blankLines="0"/>
Aichholzgasse 6/12, AT-1120<vspace blankLines="0"/>
Wien, Austria<vspace blankLines="0"/>
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72</t>
<t>ISO 639-2 defines a maintenance agency for additions to and changes in the list of languages in ISO 639-2. This agency is:</t>
<t>Library of Congress<vspace blankLines="0"/>
Network Development and MARC Standards Office<vspace blankLines="0"/>
Washington, D.C. 20540 USA<vspace blankLines="0"/>
Phone: +1 202 707 6237 Fax: +1 202 707 0115<vspace blankLines="0"/>
URL: http://www.loc.gov/standards/iso639-2</t>
<t>ISO 639-3 defines a maintenance agency for additions to and changes in the list of languages in ISO 639-3. This agency is:</t>
<t>SIL International<vspace blankLines="0"/>ISO 639-3 Registrar
<vspace blankLines="0"/>7500 W. Camp Wisdom Rd.
<vspace blankLines="0"/>Dallas, TX 75236 USA<vspace blankLines="0"/>
Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546<vspace blankLines="0"/> Email: iso639-3@sil.org<vspace blankLines="0"/>
URL: http://www.sil.org/iso639-3</t>
<t>The maintenance agency for ISO 3166-1 (country codes) is:</t>
<t>ISO 3166 Maintenance Agency<vspace blankLines="0"/>
c/o International Organization for Standardization<vspace blankLines="0"/>
Case postale 56<vspace blankLines="0"/>
CH-1211 Geneva 20 Switzerland<vspace blankLines="0"/>
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49<vspace blankLines="0"/>
URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html </t>
<t>The registration authority for ISO 15924 (script codes) is: </t>
<t>Unicode Consortium Box 391476<vspace blankLines="0"/>
Mountain View, CA 94039-1476, USA<vspace blankLines="0"/>
URL: http://www.unicode.org/iso15924 </t>
<t>The Statistics Division of the United Nations Secretariat maintains the
Standard Country or Area Codes for Statistical Use and can be reached at:</t>
<t>Statistical Services Branch<vspace blankLines="0"/>
Statistics Division<vspace blankLines="0"/>
United Nations, Room DC2-1620<vspace blankLines="0"/>
New York, NY 10017, USA<vspace blankLines="1"/>
Fax: +1-212-963-0623<vspace blankLines="0"/>
E-mail: statistics@un.org<vspace blankLines="0"/>
URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm</t>
</section>
<section anchor="extensions" title="Extensions and the Extensions Registry">
<t>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.</t>
<t>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.</t>
<t>Single-character subtags are assigned by IANA using the "IETF Consensus" policy defined by <xref target="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, 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:
<list style="symbols">
<t>The specification MUST reference the specific version or revision
of this document that governs its creation and MUST reference
this section of this document.</t>
<t>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.</t>
<t>The specification MUST specify a canonical representation.</t>
<t>The specification of valid subtags MUST be available
over the Internet and at no cost.</t>
<t>The specification MUST be in the public domain or available
via a royalty-free license acceptable to the IETF and specified
in the RFC.</t>
<t>The specification MUST be versioned, and each version of the
specification MUST be numbered, dated, and stable.</t>
<t>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.</t>
<t>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.</t>
<t>IANA MUST be informed of changes to the contact information and
URL for the specification.</t>
</list>
</t>
<t>IANA will maintain a registry of allocated single-character (singleton) subtags. This registry MUST use the record-jar format described by the ABNF in <xref target="ianaformat"/>. Upon publication of an extension as an RFC, the maintaining authority defined in the RFC MUST forward this registration form to iesg@ietf.org, who MUST forward the request to iana@iana.org. The maintaining authority of the extension MUST maintain the accuracy of the record by sending an updated full copy of the record to iana@iana.org with the subject line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in these updates.</t>
<t>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 <xref target="RFC2028"/> under the same rules as other IETF decisions (see <xref target="RFC2026"/>) and MAY result in the authority to maintain the extension being withdrawn or reassigned by the IESG.</t>
<figure title="Format of Records in the Language Tag Extensions Registry" anchor="extension_fmt_art">
<artwork name="LANGUAGE TAG EXTENSION REGISTRATION FORM">%%
Identifier:
Description:
Comments:
Added:
RFC:
Authority:
Contact_Email:
Mailing_List:
URL:
%%</artwork>
</figure>
<t>'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.</t>
<t>'Description' contains the name and description of the extension.</t>
<t>'Comments' is an OPTIONAL field and MAY contain a broader description of the extension.</t>
<t>'Added' contains the date the extension's RFC was published in
the "full-date" format specified in <xref target="RFC3339"/>. For example: 2004-06-28 represents June 28, 2004, in the
Gregorian calendar.</t>
<t>'RFC' contains the RFC number assigned to the extension.</t>
<t>'Authority' contains the name of the maintaining authority for the extension.</t>
<t>'Contact_Email' contains the email address used to contact the maintaining authority.</t>
<t>'Mailing_List' contains the URL or subscription email address of the mailing list used by the maintaining authority.</t>
<t>'URL' contains the URL of the registry for this extension.</t>
<t>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.</t>
<t hangText="Note: ">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.</t>
<t>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.</t>
</section>
<section title="Update of the Language Subtag Registry" anchor="ianaconversion">
<t>Upon adoption of this document the IANA Language Subtag Registry will need an update so that it contains the complete set of subtags valid in a language tag. This collection of subtags, along with a description of the process used to create it, is described by <xref target="registry-update"/>. IANA will publish the updated version of the registry described by this document using the instructions and content of <xref target="registry-update"/>. Once published by IANA, the maintenance procedures, rules, and registration processes described in this document will be available for new registrations or updates.</t>
<t>Registrations that are in process under the rules defined in <xref target="RFC4646"/> when this document is adopted
MUST be completed under the rules contained in this document.</t>
</section>
</section>
<section title="Formation and Processing of Language Tags">
<t>This section addresses how to use the information in the registry with the tag syntax to choose, form, and process language tags.</t>
<section anchor="choice" title="Choice of Language Tag">
<t>The guiding principle in forming language tags is to "tag content wisely." Sometimes there is a choice between several possible tags for the same content. The choice of which tag to use depends on the content and application in question and some amount of judgment might be necessary when selecting a tag.</t>
<t>Interoperability is best served when the same language tag
is used consistently 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. </t>
<t>A subtag SHOULD only be used when it adds useful distinguishing information to the tag. Extraneous subtags interfere with the meaning, understanding, and processing of language tags. In particular, users and implementations SHOULD follow the 'Prefix' and 'Suppress-Script' fields in the registry (defined in <xref target="ianaformat"/>): these fields provide guidance on when specific additional subtags SHOULD be used or avoided in a language tag.</t>
<t>Some applications can benefit from the use of script subtags in language tags, as long as the use is consistent for a given context. Script subtags are never appropriate for unwritten content (such as audio recordings).</t>
<t>Script subtags were formally defined in BCP 47 by <xref target="RFC4646"/>. Their use can affect matching and subtag identification for implementations of previous versions of BCP 47 (i.e. <xref target="RFC1766"/> or <xref target="RFC3066"/>), as these subtags appear between the primary language and region subtags. For example, if an implementation selects content using <xref target="RFC4647">Basic Filtering</xref> (originally described in Section 2.5 of <xref target="RFC3066"/>) and the user requested the language range "en-US", content labeled "en-Latn-US" will not match the request and thus not be selected. Therefore, it is important to know when script subtags will customarily be used and when they ought not be used. In the registry, the Suppress-Script field helps ensure greater compatibility between the language tags by defining when users SHOULD NOT include a script subtag with a particular primary language subtag.</t>
<t>The choice of subtags used to form a language tag SHOULD follow these guidelines:<list style="numbers">
<t>Use as precise a tag as possible, but no more specific than is justified.
Avoid using subtags that are not important for distinguishing content in an application. <list style="symbols">
<t>For example, 'de' might suffice for tagging an email written in German,
while "de-CH-1996" is probably unnecessarily precise for such a task.</t>
<t>Note that some subtag sequences might not represent the language a casual user might expect, especially if when relying on the subtag's description in the registry. For example, the Swiss German (Schweizerdeutsch) language is represented by "gsw-CH" and not by "de-CH". This latter tag represents German ('de') as used in Switzerland ('CH'), also known as Swiss High German (Schweizer Hochdeutsch). Both are real languages and distinguishing between them could be important to an application.</t>
</list>
</t>
<t>The script subtag SHOULD NOT be used to form language tags unless the script adds some distinguishing information to the tag. The field 'Suppress-Script' in the primary language record in the registry indicates script subtags that do not add distinguishing information for most applications. For example:<list style="symbols">
<t>The subtag 'Latn' should not be used with the primary language 'en' because nearly all English documents are written in the Latin script and it adds no distinguishing information. However, if a document were written in English mixing Latin script with another script such as Braille ('Brai'), then it might be appropriate to choose to indicate both scripts to aid in content selection, such as the application of a style sheet.</t>
<t>When labeling content that is unwritten (such as a recording of human speech), the script subtag should not be used, even if the language is customarily written in several scripts. Thus the subtitles to a movie might use the tag "zh-cmn-Hant" (Chinese, Mandarin, Traditional script), but the audio track for the same language would be tagged "zh-cmn".</t>
</list>
</t>
<t>If a tag or subtag has a 'Preferred-Value' field in its registry entry, then the value of that field SHOULD be used to form the language tag in preference to the tag or subtag in which the preferred value appears. <list style="symbols">
<t>For example, use 'he' for Hebrew in preference
to 'iw'.</t>
</list>
</t>
<t>
<xref target="ISO639-2"/> has defined several codes included in the subtag registry that require additional care when choosing language tags. In most of these cases, where omitting the language tag is permitted, such omission is preferable to using these codes. Language tags SHOULD NOT incorporate these subtags as a prefix, unless the additional information conveys some value to the application.<list>
<t>Use specific language subtags or subtag sequences in preference to subtags for language collections. A "language collection" is a subtag derived from one of the <xref target="ISO639-2"/> codes that represents multiple related languages. These codes are included as primary language subtags in the registry. For example, the code 'cmc' represents "Chamic languages". The registry contains values for each of the approximately ten individual languages represented by this collective code. Some other examples include the subtags Germanic languages ('gem') or Algonquian languages ('alg'). Since these codes are interpreted inclusively, content tagged with "en" (English), "de" (German), or "gsw" (Swiss German, Alemannic) could also (but SHOULD NOT) be tagged with "gem" (Germanic languages). Subtags derived from collection codes SHOULD NOT be used be used unless more specific language information is not available. Note that matching implementations generally do not understand the relationship between the collection and its encompassed languages, and so users ought not assume a subtag based on a language collection is a useful means for selecting content in its encompassed languages.</t>
<t>The 'mul' (Multiple) primary language subtag identifies content in multiple languages. It SHOULD NOT be used when a list of languages (such as Content-Language) or individual tags for each content element can be used instead.</t>
<t>The 'und' (Undetermined) primary language subtag identifies linguistic content whose language is not determined. It SHOULD NOT be used unless a language tag is required and language information is not available or cannot be determined.
Omitting the
language tag (where permitted) is preferred. The 'und' subtag MAY be useful for protocols
that require a language tag to be provided or where a primary language subtag is required (such as in "und-Latn"). The 'und' subtag MAY also
be useful when matching language tags in certain situations.</t>
<t>The 'zxx' (Non-Linguistic) primary language subtag identifies content that has no language. Some examples might include instrumental or electronic music; sound recordings consisting of nonverbal sounds; audiovisual materials with no narration, printed titles, or subtitles; machine-readable data files consisting of machine languages or character codes; or programming source code. Note: where there are fragments of linguistic content, such as programming source code containing comments written in English, the subtag 'zxx' might still be used to indicate the primary status of the content, just as 'en' can be applied to a predominantly English text that contains a few French phrases. </t>
<t>The 'mis' (Uncoded) primary language subtag identifies content whose language is known but which does not currently have a corresponding subtag. This subtag SHOULD NOT be used. Because the addition of other codes in the future can render its application invalid, it is inherently unstable and hence incompatible with the stability goals of BCP 47. It is always preferable to use other subtags: either 'und' or (with prior agreement) private use subtags.</t>
<t>The grandfathered tag "i-default" (Default Language) was originally registered according to <xref target="RFC1766"/> to meet the needs of <xref target="RFC2277"/>. It is used to indicate not a specific language, but rather, it identifies the condition or content used where the language preferences of the user cannot be established. It SHOULD NOT be used except as a means of labeling the default content for applications or protocols that require default language content to be labeled with that specific tag. It MAY also be used by an application or protocol to identify when the default language content is being returned.</t>
</list>
</t>
</list>
</t>
<t> Some of the languages in the registry are labeled "macrolanguages" by ISO 639-3, which defines the term as "clusters of closely-related language varieties that [...] can be considered distinct individual languages, yet in certain usage contexts a single language identity for all is needed". These correspond to codes registered in ISO 639-2 as single languages that were found to correspond to more than one language in ISO 639-3. The record for each of the languages encompassed by a macrolanguage contains a 'Macrolanguage' field in the registry; the macrolanguages themselves are not specially marked.</t>
<t>It is always permitted, and sometimes useful, to tag an encompassed language using the subtag for its macrolanguage. However, the Macrolanguage field doesn't define what the relationship is between the encompassed language and its macrolanguage, nor does it define how languages encompassed by the same macrolanguage are related to each other. In some cases, one of the encompassed languages serves as a standard form for the entire macrolanguage and is frequently identified with it; in other cases there is no dominant language, and the macrolanguage simply serves as a cover term for the entire group.</t>
<t>Applications MAY use macrolanguage information to improve matching or language negotiation. For example, the information that 'sr' (Serbian) and 'hr' (Croatian) share a macrolanguage expresses a closer relation between those languages than between, say, 'sr' (Serbian) and 'ma' (Macedonian). It is valid to use either the subtag of the encompassed language or of the macrolanguage to form language tags. However, many matching applications will not be aware of the relationship between the languages. Care in selecting which subtags are used is crucial to interoperability.</t>
<t>In general, use the most specific subtag to form the language tag. However, where the macrolanguage tag has been historically used to denote a dominant encompassed language, it SHOULD be used in place of the subtag specific to that encompassed language unless it is necessary to clearly distinguish the macrolanguage as a whole from that enclosed dominant language variety.</t>
<figure anchor="affectedLangs">
<preamble>The pairs of macro and encompassed languages affected by this issue when this document was published were:</preamble>
<artwork>
Arabic 'ar' Standard Arabic 'arb'
Konkani (macrolanguage) 'kok' Konkani (single language) 'knn'
Malay (macrolanguage) 'ms' Malay (single language) 'mly'
Swahili (macrolanguage) 'sw' Swahili (single language) 'swh'
Uzbek 'uz' Northern Uzbek 'uzn'
Chinese 'zh' Mandarin Chinese 'cmn'
</artwork>
</figure>
<t>In particular, the Chinese family of languages call for special consideration. Because the written form is very similar for most languages having 'zh' (Chinese) as a macrolanguage (and because historically subtags for the various encompassed languages were not available), languages such as 'yue' (Cantonese) have historically used either 'zh' or a tag (now grandfathered) beginning with 'zh'. This means that macrolanguage information can be usefully applied when searching for content or when providing fallbacks in language negotiation. For example, the information that 'yue' has a macrolangauge of 'zh' could be used in the Lookup algorithm to fallback from a request for "yue-Hans-CN" to "zh-Hans-CN" without losing the script and region information (even though the user did not specify "zh-Hans-CN" in their request).</t>
<t> 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 invalid, nor will a language tag have a
narrower scope in the future (it may have a broader scope).</t>
<t>Standards, protocols, and applications that reference this document normatively
but apply different rules to the ones given in this section MUST specify
how language tag selection varies from the guidelines given here. </t>
</section>
<section anchor="meaning" title="Meaning of the Language Tag">
<t>The meaning of a language tag is related to the meaning of the subtags that it contains. Each subtag, in turn, implies a certain range of expectations one might have for related content, although it is not a guarantee. For example, the use of a script subtag such as 'Arab' (Arabic script) does not mean that the content contains only Arabic characters. It does mean that the language involved is predominantly in the Arabic script. Thus a language tag and its subtags can encompass a very wide range of variation and yet remain appropriate in each particular instance.</t>
<t>Validity of a tag is not the only factor determining its usefulness. While every valid tag has a meaning, it might not represent any real-world language usage. This is unavoidable in a system in which subtags can be combined freely. For example, tags such as "ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia ) or "tlh-Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA phonetic transcription) are both valid and unlikely to represent a useful combination of language attributes.</t>
<t>The meaning of a given tag doesn't depend on the context in which it appears. The relationship between a tag's meaning and the information objects to which that tag is applied, however, can vary.<list style="symbols">
<t>For a single information object, the associated language tags might be
interpreted as the set of languages that is necessary for a complete
comprehension of the complete object. Example: Plain text documents.</t>
<t>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.</t>
<t>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.</t>
<t>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 applying the
inappropriate Norwegian rules.</t>
<t>Language tags form the basis for most implementations of locale identifiers. For example, see Unicode's CLDR (Common Locale Data Repository) project.</t>
</list>
</t>
<t>Language tags are related when they contain a similar sequence of subtags. For example, if a language tag B contains language tag A as a prefix, then B is typically
"narrower" or "more specific" than A. Thus, "zh-Hant-TW" is more specific
than "zh-Hant".</t>
<t>This relationship is not guaranteed in all cases: specifically,
languages that begin with the same sequence of subtags are NOT guaranteed to be
mutually intelligible, although they might be. For example, the tag "az"
shares a prefix with both "az-Latn" (Azerbaijani written using the Latin script)
and "az-Cyrl" (Azerbaijani written using the Cyrillic script). A person fluent
in one script might not be able to read the other, even though the text might be
identical. Content tagged as "az" most probably is written in just one script
and thus might not be intelligible to a reader familiar with the other script.</t>
<t>Similarly, not all subtags specify an actual distinction in language. For example, the tags "en-US" and "en-CA" mean, roughly, English with features
generally thought to be characteristic of the United States and Canada,
respectively. They do not imply that a significant dialectical boundary
exists between any arbitrarily selected point in the United States and any
arbitrarily selected point in Canada. Neither does a particular region subtag imply that linguistic distinctions do not exist within that region.</t>
</section>
<section anchor="length" title="Length Considerations">
<t>There is no defined upper limit on the size of language tags. While historically most language tags have consisted of language and region subtags with a combined total length of up to six characters, larger tags have always been both possible and actually appeared in use. </t>
<t>Neither the language tag syntax nor other requirements in this document impose a fixed upper limit on the number of subtags in a language tag (and thus an upper bound on the size of a tag). The language tag syntax suggests that, depending on the specific language, more subtags (and thus a longer tag) are sometimes necessary to completely identify the language for certain applications; thus, it is possible to envision long or complex subtag sequences. </t>
<section anchor="bufferLimits" title="Working with Limited Buffer Sizes">
<t>Some applications and protocols are forced to allocate fixed buffer sizes or otherwise limit the length of a language tag. A conformant implementation or specification MAY refuse to support the storage of
language tags
that exceed a specified length. Any such limitation SHOULD be clearly documented, and such documentation SHOULD include what happens to longer tags (for example, whether an error value is generated or the language tag is truncated). A protocol that allows tags to be truncated at an arbitrary limit, without giving any indication of what that limit is, has the potential for causing harm by changing the meaning of tags in substantial ways. </t>
<t>In practice, most language tags do not require more than a few subtags and will not approach reasonably sized buffer limitations; see <xref target="choice"/>.</t>
<t>Some specifications or protocols have limits on tag length but do not have a fixed length limitation. For example, <xref target="RFC2231"/> has no explicit length limitation: the length available for the language tag is constrained by the length of other header components (such as the charset's name) coupled with the 76-character limit in <xref target="RFC2047"/>. Thus, the "limit" might be 50 or more characters, but it could potentially be quite small.</t>
<t>The considerations for assigning a buffer limit are:<list>
<t>Implementations SHOULD NOT truncate language tags unless the meaning of the tag is purposefully being changed, or unless the tag does not fit into a limited buffer size specified by a protocol for storage or transmission.</t>
<t>Implementations SHOULD warn the user when a tag is truncated since truncation changes the semantic meaning of the tag.</t>
<t>Implementations of protocols or specifications that are space constrained but do not have a fixed limit SHOULD use the longest possible tag in preference to truncation.</t>
<t>Protocols or specifications that specify limited buffer sizes for language tags MUST allow for language tags of up to 33 characters.</t>
<t>Protocols or specifications that specify limited buffer sizes for language tags SHOULD allow for language tags of at least
30 characters. Note that <xref target="RFC4646">RFC 4646</xref> recommended a field size of 42 character because it included the permanently reserved (and unused) 'extlang' production. The current size recommendation does not include the use of the 'extlang' field. Protocols or specifications that commonly use extensions or private use subtags might wish to reserve or recommend a longer "minimum buffer" size.</t>
</list>
</t>
<t>The following illustration shows how the 30-character recommendation was derived:</t>
<figure title="Derivation of the Limit on Tag Length" anchor="longtag42">
<artwork>
language = 3 (ISO 639-2; ISO 639-1 requires 2)
script = 5 (if not suppressed: see Section 4.1)
region = 4 (UN M.49; ISO 3166-1 requires 3)
variant1 = 9 (needs 'language' as a prefix)
variant2 = 9 (needs 'language-variant1' as a prefix)
total = 30 characters
</artwork>
</figure>
</section>
<section anchor="truncation" title="Truncation of Language Tags">
<t>Truncation of a language tag alters the meaning of the tag, and thus SHOULD be avoided. However, truncation of language tags is sometimes necessary due to limited buffer sizes. Such truncation MUST NOT permit a subtag to be chopped off in the middle or the formation of invalid tags (for example, one ending with the "-" character).</t>
<t>This means that applications or protocols that truncate tags MUST do so
by progressively removing subtags along with their preceding "-" from the right side of the language tag until the tag is short enough for the given buffer. If the resulting tag ends with a single-character subtag, that subtag and its preceding "-" MUST also be removed. For example:</t>
<figure title="Example of Tag Truncation" anchor="truncationFigure">
<artwork name="truncation.artwork">
Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1
1. zh-Latn-CN-variant1-a-extend1-x-wadegile
2. zh-Latn-CN-variant1-a-extend1
3. zh-Latn-CN-variant1
4. zh-Latn-CN
5. zh-Latn
6. zh
</artwork>
</figure>
</section>
</section>
<section title="Canonicalization of Language Tags" anchor="canonical">
<t>Since a particular language tag is sometimes used by many processes, language tags SHOULD always be created or generated in a canonical form.</t>
<t>A language tag is in canonical form when:
<list style="numbers">
<t>The tag is well-formed according the rules in <xref target="syntax"/> and
<xref target="sources"/>.</t>
<t>Subtags of type 'Region' that have a Preferred-Value mapping
in the IANA registry (see <xref target="ianaformat"/>) MUST be
replaced with their mapped value. Note: In rare cases, the mapped value will also have a Preferred-Value.</t>
<t>Redundant or grandfathered tags that have a Preferred-Value mapping
in the IANA registry (see <xref target="ianaformat"/>) MUST
be replaced with their mapped value. These items either are
deprecated mappings created before the adoption of this document
(such as the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh")
or are the result of later registrations or additions to this
document (for example, "zh-hakka" was deprecated in favor of the
ISO 639-3 code 'hak' when this document was adopted).</t>
<t>Other subtags that have a Preferred-Value mapping
in the IANA registry (see <xref target="ianaformat"/>) MUST be
replaced with their mapped value. These items consist entirely of
clerical corrections to ISO 639-1 in which the deprecated subtags
have been maintained for compatibility purposes.</t>
<t>If more than one extension subtag sequence exists, the extension
sequences are ordered into case-insensitive ASCII order by singleton
subtag.</t>
</list>
</t>
<t>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 and potentially valid (extensions 'a' and 'b' are not defined as of the publication of this document) but not in canonical form (the extensions are not in alphabetical order).</t>
<t>Example: The language tag "en-BU" (English as used in Burma) is
not canonical because the 'BU' subtag has a canonical mapping to 'MM' (Myanmar), although the tag "en-BU" maintains its validity.</t>
<t>Canonicalization of language tags does not imply anything about the use of upper or lowercase letters when processing or comparing subtags (and as described in <xref target="syntax"/>). All comparisons MUST be performed in a case-insensitive manner.</t>
<t>When performing canonicalization of language tags, processors MAY regularize the case of the subtags (that is, this process is OPTIONAL), following the case used in the registry. Note that this corresponds to the following casing rules: uppercase all non-initial two-letter subtags; titlecase all non-initial four-letter subtags; lowercase everything else.</t>
<t>Note: Case folding of ASCII letters in certain locales, unless carefully handled, sometimes produces non-ASCII character values. The Unicode Character Database file "SpecialCasing.txt" defines the specific cases that are known to cause problems with this. In particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). Implementers SHOULD specify a locale-neutral casing operation to ensure that case folding of subtags does not produce this value, which is illegal in language tags. For example, if one were to uppercase the region subtag 'in' using Turkish locale rules, the sequence U+0130 U+004E would result instead of the expected 'IN'.</t>
<t>Note: if the field 'Deprecated' appears in a registry record without an accompanying 'Preferred-Value' field, then that tag or subtag is deprecated without a replacement. Validating processors SHOULD NOT generate tags that include these values, although the values are canonical when they appear in a language tag.</t>
<t>An extension MUST define any relationships that exist between the
various subtags in the extension and thus MAY define an alternate
canonicalization scheme for the extension's subtags. Extensions MAY
define how the order of the
extension's subtags are interpreted. For example, an extension could
define that its subtags are in canonical order when the subtags are placed
into ASCII order: that is, "en-a-aaa-bbb-ccc" instead of
"en-a-ccc-bbb-aaa". Another
extension might define that the order of the subtags influences their
semantic meaning (so that "en-b-ccc-bbb-aaa" has a different value from
"en-b-aaa-bbb-ccc"). However, extension specifications SHOULD be designed so that they are tolerant of the typical processes described in <xref target="extensions"/>.</t>
</section>
<section anchor="privateuse" title="Considerations for Private Use Subtags">
<t hangText="Note:">Private use subtags, like all other subtags, MUST conform to the format and content constraints in the ABNF. Private use
subtags have no meaning outside the private agreement between
the parties that intend to use or exchange language tags that employ them. The same subtags MAY be used with a different meaning under a separate private agreement. They SHOULD NOT be used where alternatives exist and SHOULD NOT be used in content or protocols
intended for general use. </t>
<t hangText="Note:">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.</t>
<t>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.</t>
<t>For example, the region subtags 'AA', 'ZZ', and in the ranges 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166-1 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.</t>
<t>However, in some cases content tagged with private use subtags MAY interact with other systems in a different and possibly unsuitable manner compared to tags that use opaque, privately defined subtags, so the choice of the best approach sometimes depends on the particular domain in question.</t>
</section>
</section>
<section anchor="iana" title="IANA Considerations">
<t>This section deals with the processes and requirements necessary
for IANA to undertake to maintain the subtag and extension registries as defined by this document and in accordance with the
requirements of <xref target="RFC2434"/>.</t>
<t>The impact on the IANA maintainers of the two registries defined by this document will be a
small increase in the frequency of new entries or updates. IANA also is required to create a new mailing list (described below in <xref target="iana-subtag-reg"/>) to announce registry changes and updates.</t>
<section title="Language Subtag Registry" anchor="iana-subtag-reg">
<t>Upon adoption of this document, IANA will update the registry using instructions and content provided in a companion document: <xref target="registry-update"/>. The criteria and process for selecting the updated set of records are described in that document. The updated
set of records represents no impact on IANA, since the work to create it will
be performed externally. </t>
<t>Future work on the Language Subtag Registry includes the following activities:<list style="symbols">
<t>Inserting or replacing whole records. These records are preformatted for IANA by the Language Subtag Reviewer, as described in <xref target="maintreg"/>.</t>
<t>Archiving and making publicly available the registration forms.</t>
<t>Announcing each updated version of the registry on the "ietf-languages-announcements@iana.org" mailing list.</t>
</list>
</t>
<t>Each registration form sent to IANA contains a single record for incorporation into the registry. The form will be sent to "iana@iana.org" by the Language Subtag Reviewer. It will have a subject line indicating whether the enclosed form represents an insertion of a new record (indicated by the word "INSERT" in the subject line) or a replacement of an existing record (indicated by the word "MODIFY" in the subject line). At no time can a record be deleted from the registry.</t>
<t>IANA will extract the record from the form and place the inserted or modified record into the appropriate section of the language subtag registry, grouping the records by their 'Type' field. Inserted records can be placed anywhere in the appropriate section; there is no guarantee of the order of the records beyond grouping them together by 'Type'. Modified records overwrite the record they replace.</t>
<t>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 <xref target="RFC3339"/> "full-date" format: included in any request to insert or modify records will be a new File-Date record indicating the acceptance date of the record. This record is to be placed first in the registry, replacing the existing File-Date record. In the event that the File-Date record present in the registry has a later date than the record being inserted or modified, then the latest (most recent) record will be preserved. IANA should attempt to process multiple registration requests in order according to the File-Date in the form, since one registration could otherwise cause a more recent change to be overwritten.</t>
<t>The updated registry file MUST use the UTF-8 character encoding and IANA MUST check the registry file for proper encoding. Non-ASCII characters can be sent to IANA by attaching the registration form to the email message or by using various encodings in the mail message body (UTF-8 is recommended). IANA will verify any unclear or corrupted characters with the Language Subtag Reviewer prior to posting the updated registry.</t>
<t>IANA will also archive and make publicly available from "http://www.iana.org/assignments/lang-subtags-templates/" each registration form. Note that multiple registrations can pertain to the same record in the registry.</t>
<t>Developers who are dependent upon the language subtag registry sometimes would like to be
informed of changes in the registry so that they can update their
implementations. When any change is made to the language subtag
registry, IANA will send an announcement message to
"ietf-languages-announcements@iana.org" (a self-subscribing list that only
IANA can post to). </t>
</section>
<section title="Extensions Registry" anchor="iana-ext-reg">
<t>The Language Tag Extensions Registry can contain at most 35 records and thus changes to this registry are expected to be very infrequent. </t>
<t>Future work by IANA on the Language Tag Extensions Registry is limited to two cases. First, the IESG MAY request that new records be inserted into this registry from time to time. These requests MUST include the record to insert in the exact format described in <xref target="extensions"/>. In addition, there MAY be occasional requests from the maintaining authority for a specific extension to update the contact information or URLs in the record. These requests MUST include the complete, updated record. IANA is not responsible for validating the information provided, only that it is properly formatted. It should reasonably be seen to come from the maintaining authority named in the record present in the registry.</t>
</section>
</section>
<section anchor="security" title="Security Considerations">
<t>Language tags used in content negotiation, like any other information exchanged on the Internet, might be a source of concern because they might be used to infer the nationality of the
sender, and thus identify potential targets for surveillance.</t>
<t>This is a special case of the general problem that anything sent is visible
to the receiving party and possibly to third parties as well. It is useful to be aware that such concerns can exist in
some cases.</t>
<t>The evaluation of the exact magnitude of the threat, and any possible
countermeasures, is left to each application protocol (see <xref target="RFC3552">BCP 72</xref> for best current practice guidance on security threats
and defenses).</t>
<t>The language tag associated with a particular information item is of no
consequence whatsoever in determining whether that content might
contain possible homographs. The fact that a text is tagged as being
in one language or using a particular script subtag provides no assurance whatsoever that it does not
contain characters from scripts other than the one(s) associated with or specified by
that language tag.</t>
<t> Since there is no limit to the number of variant, private use, and extension
subtags, and consequently no limit on the possible length of a tag,
implementations need to guard against buffer overflow attacks. See <xref target="length"/> for details on language tag truncation, which can occur as a
consequence of defenses against buffer overflow.</t>
<t hangText="Note: ">Although the specification of valid subtags for an
extension (see <xref target="extensions"/>) MUST be available over the Internet, implementations SHOULD NOT
mechanically depend on it being always accessible, to prevent
denial-of-service attacks.</t>
</section>
<section anchor="charset" title="Character Set Considerations">
<t>The syntax in this document requires that language tags use only
the characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in
most character sets, so the composition of language tags should not have any
character set issues.</t>
<t>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 sometimes 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. </t>
</section>
<section anchor="changes" title="Changes from RFC 4646">
<t>The main goal for this revision of this document was to incorporate ISO 639-3 and its attendant set of language codes into the IANA Language Subtag Registry, permitting the identification of many more languages and dialects than previously supported.</t>
<t>The specific changes in this document to meet these goals are:
<list style="symbols">
<t>Defines the incorporation of ISO 639-3 codes as language. It also permanently reserves and disallows the use of extlang subtags. The changes necessary to achieve this were:<list>
<t>Modified the ABNF comments.</t>
<t>Updated various registration and stability requirements sections to reference ISO 639-3 in addition to ISO 639-1 and ISO 639-2.</t>
<t>Edited the text to eliminate references to extended language subtags where they are no longer used.</t>
<t>Explained the change in the section on extended language subtags.</t>
</list>
</t>
<t>Changed the ABNF related to grandfathered tags. The irregular tags are now listed. Well-formed grandfathered tags are now described by the 'langtag' production and the 'grandfathered' production was removed as a result. Also: added description of both types of grandfathered tags to <xref target="preexisreg"/>.</t>
<t>Added the paragraph on "collections" to <xref target="choice"/>.</t>
<t>Changed the capitalization rules for 'Tag' fields in <xref target="ianaformat"/>.</t>
<t>Split section 3.1 up into subsections.</t>
<t>Modified section 3.5 to allow Suppress-Script fields to be added, modified, or removed via the registration process. This was an erratum from RFC 4646.</t>
<t>Modified examples that used region code 'CS' (formerly Serbia and Montenegro) to use 'RS' (Serbia) instead.</t>
<t>Modified the rules for creating and maintaining record 'Description' fields to prevent duplicates, including inverted duplicates.</t>
<t>Removed the lengthy description of why RFC 4646 was created from this section, which also caused the removal of the reference to XML Schema.</t>
<t>Modified the text in section 2.1 to place more emphasis on the fact that language tags are not case sensitive.</t>
<t>Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the Suppress-Script on 'Latn' with 'fr'.</t>
<t>Changed the requirements for well-formedness to make singleton repetition checking optional (it is required for validity checking) in <xref target="conformance"/>.</t>
<t>Changed the text in <xref target="conformance"/> referring to grandfathered checking to note that the list is now included in the ABNF.</t>
<t>Modified and added text to <xref target="subtagreviewer"/>. The job description was placed first. A note was added making clear that the Language Subtag Reviewer may delegate various non-critical duties, including list moderation. Finally, additional text was added to make the appointment process clear and to clarify that decisions and performance of the reviewer are appealable.</t>
<t>Added text to <xref target="registrationProc"/> clarifying that the ietf-languages list is operated by whomever the IESG appoints.</t>
<t>Added text to <xref target="descriptionfield"/> clarifying that the first Description in a 'language' record matches the corresponding Reference Name for the language in ISO 639-3.</t>
<t>Modified <xref target="conformance"/> to define classes of conformance related to specific tags (formerly 'well-formed' and 'valid' referred to implementations). Notes were added about the removal of 'extlang' from the ABNF provided in RFC 4646, allowing for well-formedness using this older definition. Reference to RFC 3066 well-formedness was also added.</t>
<t>Added text to the end of <xref target="recordformat"/> noting that future versions of this document might add new field types to the Registry format and recommending that implementations ignore any unrecognized fields.</t>
<t>Added text about what the lack of a Suppress-Script field means in a record to <xref target="suppressfield"/>.</t>
<t>Added text allowing the correction of misspellings and typographic errors to <xref target="descriptionfield"/>.</t>
<t>Added text to <xref target="prefixfield"/> disallowing Prefix field conflicts (such as circular prefix references).</t>
<t>Modified text in <xref target="registrationProc"/> to require the subtag reviewer to announce his/her decision (or extension) following the two-week period. Also clarified that any decision or failure to decide can be appealed.</t>
<t>Modified text in <xref target="choice"/> to include the (heretofore anecdotal) guiding principle of tag choice, and clarifying the non-use of script subtags in non-written applications. Also updated examples in this section to use Chamic languages as an example of language collections.</t>
<t>Prohibited multiple use of the same variant in a tag (i.e. "de-1901-1901"). Previously this was only a recommendation ("SHOULD").</t>
<t>Removed inappropriate <xref target="RFC2119"/> language from the illustration in <xref target="bufferLimits"/>.</t>
<t>Replaced the example of deprecating "zh-gouyu" with "zh-hakka"->"hak" in <xref target="canonical"/>, noting that it was this document that caused the change.</t>
<t>Replaced the section in <xref target="choice"/> dealing with "mul"/"und" to include the subtags 'zxx' and 'mis', as well as the tag "i-default". A normative reference to RFC 2277 was added, along with an informative reference to MARC21.</t>
<t>Added text to <xref target="registrationProc"/> clarifying that any modifications of a registration request must be sent to the ietf-languages list before submission to IANA.</t>
<t>Changed the ABNF for the record-jar format from using the LWSP production to use a folding whitespace production similar to obs-FWS in <xref target="RFC5234"/>. This effectively prevents unintentional blank lines inside a field. </t>
<t>Clarified and revised text in <xref target="maintreg"/>, <xref target="registrationProc"/>, and <xref target="iana-subtag-reg"/> to clarify that the Language Subtag Reviewer sends the complete registration forms to IANA, that IANA extracts the record from the form, and that the forms must also be archived separately from the registry.</t>
<t>Added text to <xref target="iana"/> requiring IANA to send an announcement to an ietf-languages-announce list whenever the registry is updated.</t>
<t>Modification of the registry to use UTF-8 as its character encoding. This also entails additional instructions to IANA and the Language Subtag Reviewer in the registration process.</t>
<t>Modified the rules in <xref target="region"/> so that "exceptionally reserved" ISO 3166-1 codes other than 'UK' were included into the registry. In particular, this allows the code 'EU' (European Union) to be used to form language tags or (more commonly) for applications that use the registry for region codes to reference this subtag.</t>
<t>Modified the <xref target="iana">IANA considerations section</xref> to remove unnecessary normative <xref target="RFC2119"/> language.</t>
</list>
</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="ISO639-1">
<front>
<title>ISO 639-1:2002. Codes for the representation of names of languages -- Part 1: Alpha-2 code</title>
<author>
<organization abbrev="ISO">International Organization for Standardization</organization>
</author>
<date month="" year="2002"/>
</front>
</reference>
<reference anchor="ISO639-2">
<front>
<title abbrev="ISO639-2">ISO 639-2:1998. Codes for the representation of names of languages --
Part 2: Alpha-3 code, first edition</title>
<author>
<organization abbrev="ISO">International Organization for Standardization</organization>
</author>
<date year="1998"/>
</front>
</reference>
<reference anchor="ISO639-3">
<front>
<title abbrev="ISO639-2">ISO 639-3:2007. Codes for the representation of names of languages --
Part 3: Alpha-3 code for comprehensive coverage of languages</title>
<author>
<organization abbrev="ISO">International Organization for Standardization</organization>
</author>
<date year="2007"/>
</front>
</reference>
<reference anchor="ISO15924">
<front>
<title abbrev="ISO15924">ISO 15924:2004. Information and documentation -- Codes for the representation of names of scripts</title>
<author>
<organization abbrev="ISO">International Organization for Standardization</organization>
</author>
<date year="2004" month="January" day="9"/>
</front>
</reference>
<reference anchor="ISO3166-1">
<front>
<title>ISO 3166-1:2006. Codes for the representation of names of countries and their subdivisions -- Part 1: Country codes</title>
<author>
<organization abbrev="ISO">International Organization for Standardization</organization>
</author>
<date year="2006" day="20" month="November"/>
</front>
</reference>
<reference anchor="UN_M.49">
<front>
<title>Standard Country or Area Codes for Statistical Use</title>
<author>
<organization>Statistics Division, United Nations</organization>
</author>
<date day="30" month="June" year="1999"/>
</front>
<seriesInfo name="UN" value="Standard Country or Area Codes for Statistical Use, Revision 4 (United Nations publication, Sales No. 98.XVII.9"/>
</reference>
<reference anchor="UAX14" target="http://www.unicode.org/reports/tr14/">
<front>
<title abbrev="UAX#14">Unicode Standard Annex #14: Line Breaking Properties</title>
<author surname="Freitag" initials="A" fullname="Asmus Freytag">
<organization>Unicode Consortium</organization>
</author>
<date day="22" month="August" year="2006"/>
</front>
</reference>
<reference anchor="ISO646">
<front>
<title>ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for information interchange. </title>
<author>
<organization>International Organization for Standardization</organization>
</author>
<date year="1991"/>
<abstract>
<t>This standard defines an International Reference Version (IRV) which corresponds exactly to what is widely known as ASCII or US-ASCII. ISO/IEC 646 was based on the earlier standard ECMA-6. ECMA has maintained its standard up to date with respect to ISO/IEC 646 and makes an electronic copy available at http://www.ecma-international.org/publications/standards/Ecma-006.htm. ISO/IEC 646 JTC 1/SC 2</t>
</abstract>
</front>
</reference>
&rfc2026;&rfc2028;
&rfc2119;
&rfc2277;
&rfc2434;
&rfc2860;
&rfc3339;
&rfc4645;&rfc4647;&rfc5234;</references>
<references title="Informative References">
<reference anchor="registry-update" target="http://www.ietf.org/internet-drafts/draft-ietf-ltru-initial-registry-00.txt">
<front>
<title abbrev="draft-ietf-ltru-initial-registry">Update to the Language Subtag Registry</title>
<author initials="D" surname="Ewell" fullname="Doug Ewell" role="editor">
<organization>LTRU Working Group</organization>
</author>
<date day="12" month="September" year="2006"/>
</front>
</reference>
<reference anchor="iso639.prin" target="http://www.loc.gov/standards/iso639-2/iso639jac_n3r.html">
<front>
<title>ISO 639 Joint Advisory Committee:
Working principles for ISO 639 maintenance</title>
<author>
<organization>ISO 639 Joint Advisory Committee</organization>
</author>
<date day="8" month="March" year="2000"/>
</front>
</reference>
<reference anchor="record-jar" target="urn:isbn:0-13-142901-9">
<front>
<title>The Art of Unix Programming</title>
<author fullname="Eric Steven Raymond" initials="E" surname="Raymond">
<organization/>
</author>
<date year="2003"/>
<note title="Note about record-jar:">
<t>This book contains the reference to the record-jar format in Chapter 5. An online version is here: http://www.faqs.org/docs/artu/ch05s02.html#id2906931.</t>
</note>
</front>
</reference>
<reference anchor="Unicode">
<front>
<title>The Unicode Consortium. The Unicode Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-49081-0)</title>
<author>
<organization>Unicode Consortium</organization>
</author>
<date year="2007" day="31" month="January"/>
</front>
</reference>
<reference anchor="UTS35" target="http://www.unicode.org/reports/tr35/">
<front>
<title>Unicode Technical Standard #35: Locale Data Markup Language (LDML)</title>
<author initials="M" surname="Davis" fullname="Mark Davis">
<organization>Unicode Consortium</organization>
</author>
<date day="21" month="December" year="2007"/>
</front>
</reference>&rfc1766;&rfc2047;&rfc2231;&rfc2781;&rfc3066;&rfc3552;&rfc3629;&rfc4646;</references>
<section anchor="acknowledgements" title="Acknowledgements">
<t>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. </t>
<t>The contributors to RFC 4646, RFC 4647, 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. </t>
<t>The following people contributed to this document:</t>
<t>Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion Gunn, Kent Karlsson, Chris Newman, Randy Presuhn, Stephen Silver, and many, many others.</t>
<t>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.
</t>
<t>Special thanks go to Michael Everson, who served as the Language Tag Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as the Language Subtag Reviewer since the adoption of RFC 4646. </t>
<t>Special thanks also to Doug Ewell, for his production of the first complete
subtag registry, his work to support and maintain new registrations, and his careful editorship of both RFC 4645 and <xref target="registry-update"/>.</t>
</section>
<section title="Examples of Language Tags (Informative)" anchor="examples">
<t>Simple language subtag:<list style="hanging">
<t>de (German)</t>
<t>fr (French)</t>
<t>ja (Japanese)</t>
<t>i-enochian (example of a grandfathered tag)</t>
</list>
</t>
<t>Language subtag plus Script subtag:<list style="hanging">
<t>zh-Hant (Chinese written using the Traditional Chinese script)</t>
<t>zh-Hans (Chinese written using the Simplified Chinese script)</t>
<t>sr-Cyrl (Serbian written using the Cyrillic script)</t>
<t>sr-Latn (Serbian written using the Latin script)</t>
</list>
</t>
<t>Language-Script-Region:<list style="hanging">
<t>zh-Hans-CN (Chinese written using the Simplified script as used in mainland China)</t>
<t>sr-Latn-RS (Serbian written using the Latin script as used in Serbia)</t>
</list>
</t>
<t>Language-Variant:<list>
<t>sl-rozaj (Resian dialect of Slovenian)</t>
<t>sl-nedis (Nadiza dialect of Slovenian)</t>
</list>
</t>
<t>Language-Region-Variant:<list>
<t>de-CH-1901 (German as used in Switzerland using the 1901 variant [orthography])</t>
<t>sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect)</t>
</list>
</t>
<t>Language-Script-Region-Variant:<list style="hanging">
<t>hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as used in Italy)</t>
</list>
</t>
<t>Language-Region:<list style="hanging">
<t>de-DE (German for Germany)</t>
<t>en-US (English as used in the United States)</t>
<t>es-419 (Spanish appropriate for the Latin America and Caribbean region using the UN region code)</t>
</list>
</t>
<t>Private use subtags:<list style="hanging">
<t>de-CH-x-phonebk</t>
<t>az-Arab-x-AZE-derbend</t>
</list>
</t>
<t>Private use registry values:<list style="hanging">
<t>x-whatever (private use using the singleton 'x')</t>
<t>qaa-Qaaa-QM-x-southern (all private tags)</t>
<t>de-Qaaa (German, with a private script)</t>
<t>sr-Latn-QM (Serbian, Latin-script, private region)</t>
<t>sr-Qaaa-RS (Serbian, private script, for Serbia)</t>
</list>
</t>
<t>Tags that use extensions (examples ONLY: extensions MUST be defined
by revision or update to this document or by RFC):
<list style="hanging">
<t>en-US-u-islamCal</t>
<t>zh-CN-a-myExt-x-private</t>
<t>en-a-myExt-b-another</t>
</list>
</t>
<t>Some Invalid Tags:<list style="hanging">
<t>de-419-DE (two region tags)</t>
<t>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)</t>
<t>ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter prefix)</t>
</list>
</t>
</section>
<section anchor="regexamples" title="Examples of Registration Forms">
<figure>
<artwork>LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester: Han Steenwijk
2. E-mail address of requester: han.steenwijk @ unipd.it
3. Record Requested:
Type: variant
Subtag: biske
Description: The San Giorgio dialect of Resian
Description: The Bila dialect of Resian
Prefix: sl-rozaj
Comments: The dialect of San Giorgio/Bila is one of the
four major local dialects of Resian
4. Intended meaning of the subtag: The local variety of Resian as
spoken in San Giorgio/Bila
5. Reference to published description of the language (book or
article):
-- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich
govorov, Varsava - Peterburg: Vende - Kozancikov, 1875.
</artwork>
</figure>
<figure>
<artwork>LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester: Jaska Zedlik
2. E-mail address of requester: jz53 @ zedlik.com
3. Record Requested:
Type: variant
Subtag: tarask
Description: Belarusian in Taraskievica orthography
Prefix: be
Comments: The subtag represents Branislau Taraskievic's Belarusian
orthography as published in "Bielaruski klasycny pravapis" by Juras
Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka
(Vilnia-Miensk 2005).
4. Intended meaning of the subtag:
The subtag is intended to represent the Belarusian orthography as
published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk
Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005).
5. Reference to published description of the language (book or article):
Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd.
"Bielaruskaha kamitetu", 1929, 5th edition.
Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier.
Bielaruski klasycny pravapis. Vilnia-Miensk, 2005.
6. Any other relevant information:
Belarusian in Taraskievica orthography became widely used, especially in
Belarusian-speaking Internet segment, but besides this some books and
newspapers are also printed using this orthography of Belarusian.
</artwork>
</figure>
</section>
</back>
</rfc>
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