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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.
1.
Introduction
2.
The Language Tag
2.1.
Syntax
2.1.1.
Formatting of Language Tags
2.2.
Language Subtag Sources and Interpretation
2.2.1.
Primary Language Subtag
2.2.2.
Extended Language Subtags
2.2.3.
Script Subtag
2.2.4.
Region Subtag
2.2.5.
Variant Subtags
2.2.6.
Extension Subtags
2.2.7.
Private Use Subtags
2.2.8.
Grandfathered and Redundant Registrations
2.2.9.
Classes of Conformance
3.
Registry Format and Maintenance
3.1.
Format of the IANA Language Subtag Registry
3.1.1.
File Format
3.1.2.
Record and Field Definitions
3.1.3.
Type Field
3.1.4.
Subtag and Tag Fields
3.1.5.
Description Field
3.1.6.
Deprecated Field
3.1.7.
Preferred-Value Field
3.1.8.
Prefix Field
3.1.9.
Suppress-Script Field
3.1.10.
Macrolanguage Field
3.1.11.
Scope Field
3.1.12.
Comments Field
3.2.
Language Subtag Reviewer
3.3.
Maintenance of the Registry
3.4.
Stability of IANA Registry Entries
3.5.
Registration Procedure for Subtags
3.6.
Possibilities for Registration
3.7.
Extensions and the Extensions Registry
3.8.
Update of the Language Subtag Registry
4.
Formation and Processing of Language Tags
4.1.
Choice of Language Tag
4.1.1.
Tagging Encompassed Languages
4.1.2.
Using Extended Language Subtags
4.2.
Meaning of the Language Tag
4.3.
Lists of Languages
4.4.
Length Considerations
4.4.1.
Working with Limited Buffer Sizes
4.4.2.
Truncation of Language Tags
4.5.
Canonicalization of Language Tags
4.6.
Considerations for Private Use Subtags
5.
IANA Considerations
5.1.
Language Subtag Registry
5.2.
Extensions Registry
6.
Security Considerations
7.
Character Set Considerations
8.
Changes from RFC 4646
9.
References
9.1.
Normative References
9.2.
Informative References
Appendix A.
Acknowledgements
Appendix B.
Examples of Language Tags (Informative)
Appendix C.
Examples of Registration Forms
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
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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.
The language of an information item or 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 information can also be used to select among tools (such as dictionaries) to assist in the processing or understanding of content in different languages. Knowledge about the particular language used by some piece of information content might be useful or even required by some types of processing; for example, spell-checking, computer-synthesized speech, Braille transcription, or high-quality print renderings.
One means of indicating the language used is by labeling the information content with an identifier or "tag". These tags can also be used to specify the user's preferences when selecting information content, or for labeling additional attributes of content and associated resources.
Sometimes language tags are 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.
This document specifies a particular identifier mechanism (the language tag) and a registration function for values to be used to form tags. It also defines a mechanism for private use values and future extension.
This document replaces [RFC4646] (Phillips, A. and M. Davis, “Tags for Identifying Languages,” September 2006.), which replaced [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.) and its predecessor [RFC1766] (Alvestrand, H., “Tags for the Identification of Languages,” March 1995.). For a list of changes in this document, see Section 8 (Changes from RFC 4646).
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).
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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.
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A language tag is composed from a sequence of one or more "subtags", each of which refines or narrows the range of language identified by the overall tag. Subtags, in turn, are a sequence of alphanumeric characters (letters and digits), distinguished and separated from other subtags in a tag by a hyphen ("-", ABNF (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.) [RFC5234] %x2D).
There are different types of subtag, each of which is distinguished by length, position in the tag, and content: each subtag's type can be recognized solely by these features. This makes it possible to extract and assign some semantic information to the subtags, even if the specific subtag values are not recognized. Thus, a language tag processor 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 only exceptions to this ability to infer meaning from subtag structure are the grandfathered tags listed in the productions 'regular' and 'irregular' below. These tags were registered under [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.) and are a fixed list that can never change.
The syntax of the language tag in ABNF [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.) is:
Language-Tag = langtag ; normal language tags
/ privateuse ; private use tag
/ grandfathered ; grandfathered tags
langtag = language
["-" script]
["-" region]
*("-" variant)
*("-" extension)
["-" privateuse]
language = 2*3ALPHA ; shortest ISO 639 code
["-" extlang] ; sometimes followed by
; extended language subtags
/ 4ALPHA ; or reserved for future use
/ 5*8ALPHA ; or registered language subtag
extlang = 3ALPHA ; selected ISO 639 codes
*2("-" 3ALPHA) ; permanently reserved
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))
; Single alphanumerics
; "x" reserved for private use
singleton = %x41-57 ; a - w
/ %x59-5A ; y - z
/ %x61-77 ; A - W
/ %x79-7A ; Y - Z
/ DIGIT ; 0 - 9
privateuse = "x" 1*("-" (1*8alphanum))
grandfathered = irregular ; non-redundant tags registered
/ regular ; during the RFC 3066 era
irregular = "en-GB-oed" ; irregular tags do not match
/ "i-ami" ; the 'langtag' production and
/ "i-bnn" ; would not otherwise be
/ "i-default" ; considered 'well-formed'
/ "i-enochian" ; These tags are all valid,
/ "i-hak" ; but most are deprecated
/ "i-klingon" ; in favor of more modern
/ "i-lux" ; subtags or subtag
/ "i-mingo" ; combination
/ "i-navajo"
/ "i-pwn"
/ "i-tao"
/ "i-tay"
/ "i-tsu"
/ "sgn-BE-FR"
/ "sgn-BE-NL"
/ "sgn-CH-DE"
regular = "art-lojban" ; these tags match the 'langtag'
/ "cel-gaulish" ; production, but their subtags
/ "no-bok" ; are not extended language
/ "no-nyn" ; or variant subtags: their meaning
/ "zh-guoyu" ; is defined by their registration
/ "zh-hakka" ; and all of these are deprecated
/ "zh-min" ; in favor of a more modern
/ "zh-min-nan" ; subtag or sequence of subtags
/ "zh-xiang"
alphanum = (ALPHA / DIGIT) ; letters and numbers
| Figure 1: Language Tag ABNF |
For examples of language tags, see Appendix B (Examples of Language Tags (Informative)).
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': a variant starting with a digit has a minimum length of four characters, while those starting with a letter have a minimum length of five characters.
Although [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.) refers to octets, the language tags described in this document are sequences of characters from the US-ASCII [ISO646] (International Organization for Standardization, “ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for information interchange.,” 1991.) repertoire. Language tags MAY be used in documents and applications that use other encodings, so long as these encompass the relevant part of the US-ASCII repertoire. An example of this would be an XML document that uses the UTF-16LE [RFC2781] (Hoffman, P. and F. Yergeau, “UTF-16, an encoding of ISO 10646,” February 2000.) encoding of [Unicode] (Unicode Consortium, “The Unicode Consortium. The Unicode Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-49081-0),” January 2007.).
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At all times, language 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.
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.
The ABNF syntax also does not distinguish between upper and lowercase: the uppercase US-ASCII letters in the range 'A' through 'Z' are always considered equivalent and mapped directly to their US-ASCII lowercase equivalents in the range 'a' through 'z'. So the tag "I-AMI" is considered equivalent to that value "i-ami" in the 'irregular' production.
Although case distinctions do not carry meaning in language tags, consistent formatting and presentation of language tags will aid users. The format of subtags in the registry is RECOMMENDED as the form to use in language tags. This format generally corresponds to the common conventions for the various ISO standards from which the subtags are derived.
These conventions include:
An implementation can reproduce this format without accessing the registry as follows: All subtags, including extension and private use subtags, use lowercase letters, with two exceptions: two-letter and four-letter subtags that neither appear at the start of the tag nor occur after singletons. Such two-letter subtags are all uppercase (as in the tags "en-CA-x-ca" or "sgn-BE-FR") and four-letter subtags are titlecase (as in the tag "az-Latn-x-latn").
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'.
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The namespace of language tags and their subtags is administered by the Internet Assigned Numbers Authority (IANA) [RFC2860] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.) according to the rules in Section 5 (IANA Considerations) 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.
Terminology used in this document:
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.
Some of the subtags in the IANA registry do not come from an underlying standard. These can only appear in specific positions in a tag: they can only occur as primary language subtags or as variant subtags.
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. These sequences are introduced by single-character subtags, which are reserved as follows:
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The primary language subtag is the first subtag in a language tag and cannot be omitted, with two exceptions:
The following rules apply to the primary language subtag:
- A.
- "ISO 639-2:1998 - Codes for the representation of names of languages -- Part 2: Alpha-3 code - edition 1" [ISO639‑2] (International Organization for Standardization, “ISO 639-2:1998. Codes for the representation of names of languages -- Part 2: Alpha-3 code, first edition,” 1998.)
- B.
- "ISO 639-3:2007 - Codes for the representation of names of languages -- Part 3: Alpha-3 code for comprehensive coverage of languages" [ISO639‑3] (International Organization for Standardization, “ISO 639-3:2007. Codes for the representation of names of languages -- Part 3: Alpha-3 code for comprehensive coverage of languages,” 2007.)
- C.
- "ISO 639-5:2008 - Codes for the representation of names of languages -- Part 5: Alpha-3 code for language families and groups" [ISO639‑5] (International Organization for Standardization, “ISO 639-5:1998. Codes for the representation of names of languages -- Part 5: Alpha-3 code for language families and groups,” May 2008.)
When languages have both an ISO 639-1 two-character code and a three character code (assigned by ISO 639-2, ISO 639-3, or ISO 639-5), only the ISO 639-1 two-character code is defined in the IANA registry.
When 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.
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 Section 3.4 (Stability of IANA Registry Entries).
For example, if some content were tagged with 'haw' (Hawaiian), which currently has no two-character code, the tag would not need to be changed if ISO 639-1 were to assign a two-character code to the Hawaiian language at a later date.
To avoid these problems with versioning and subtag choice (as experienced during the transition between RFC 1766 and RFC 3066), as well as to ensure the canonical nature of subtags defined by this document, the ISO 639 Registration Authority Joint Advisory Committee (ISO 639/RA-JAC) has included the following statement in [iso639.prin] (ISO 639 Joint Advisory Committee, “ISO 639 Joint Advisory Committee: Working principles for ISO 639 maintenance,” March 2000.):
"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."
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Extended language subtags are used to identify certain specially-selected languages that, for various historical and compatibility reasons, are closely identified with or tagged using an existing primary language subtag. Extended language subtags are always used with their enclosing primary language subtag (indicated with a 'Prefix' field in the registry) when used to form the language tag. All languages that have an extended language subtag in the registry also have an identical primary language subtag record in the registry. This primary language subtag is RECOMMENDED for forming the language tag. The following rules apply to the extended language subtags:
For example, the macrolanguage Chinese ('zh') encompasses a number of languages. For compatibility reasons, each of these languages has both a primary and extended language subtag in the registry. A few selected examples of these include Gan Chinese ('gan'), Cantonese Chinese ('yue') and Mandarin Chinese ('cmn'). Each is encompassed by the macrolanguage 'zh' (Chinese). Therefore, they each have the prefix "zh" in their registry records. Thus Gan Chinese is represented with tags beginning "zh-gan" or "gan"; Cantonese with tags beginning either "yue" or "zh-yue"; and Mandarin Chinese with "zh-cmn" or "cmn". The language subtag 'zh' can still be used without an extended language subtag to label a resource as some unspecified variety of Chinese, while the primary language subtag ('gan', 'yue', 'cmn') is preferred to using the extended language form ("zh-gan", "zh-yue", "zh-cmn").
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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:
For example: "sr-Latn" represents Serbian written using the Latin script.
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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 variations such as regional dialects or usage, or region-specific spelling conventions. It 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.
The following rules apply to the region subtags:
- A.
- UN numeric codes assigned to 'macro-geographical (continental)' or sub-regions MUST be registered in the registry. These codes are not associated with an assigned ISO 3166-1 alpha-2 code and represent supra-national areas, usually covering more than one nation, state, province, or territory.
- B.
- UN numeric codes for 'economic groupings' or 'other groupings' MUST NOT be registered in the IANA registry and MUST NOT be used to form language tags.
- C.
- When ISO 3166-1 reassigns a code formerly used for one country or area to another country or area and that code already is present in the registry, the UN numeric code for that country or area MUST be registered in the registry as described in Section 3.4 (Stability of IANA Registry Entries) and MUST be used to form language tags that represent the country or region for which it is defined (rather than the recycled ISO 3166-1 code).
- D.
- 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.
- E.
- UN numeric codes and ISO 3166-1 alpha-2 codes for countries or areas listed as eligible for registration in Section 4 of [RFC4645] (Ewell, D., “Initial Language Subtag Registry,” September 2006.) but not presently registered MAY be entered into the IANA registry via the process described in Section 3.5 (Registration Procedure for Subtags). Once registered, these codes MAY be used to form language tags.
- F.
- 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 Section 3.4 (Stability of IANA Registry Entries).
For example:
"de-AT" represents German ('de') as used in Austria ('AT').
"sr-Latn-RS" represents Serbian ('sr') written using Latin script ('Latn') as used in Serbia ('RS').
"es-419" represents Spanish ('es') appropriate to the UN-defined Latin America and Caribbean region ('419').
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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:
Variant subtag records in the language subtag registry MAY include one or more 'Prefix' fields. The 'Prefix' indicates a sequence of subtags 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".
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".
For example:
"sl-nedis" represents the Natisone or Nadiza dialect of Slovenian.
"de-CH-1996" represents German as used in Switzerland and as written using the spelling reform beginning in the year 1996 C.E.
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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 Section 3.7 (Extensions and the Extensions Registry). The following rules apply to extensions:
For example, if an extention were defined for the singleton 'r' and it defined the subtags shown, then the following tag would be a valid example: "en-Latn-GB-boont-r-extended-sequence-x-private"
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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:
For example: The Unicode Consortium defines a set of private use extensions in LDML ([UTS35] (Davis, M., “Unicode Technical Standard #35: Locale Data Markup Language (LDML),” December 2007.), Locale Data Markup Language, the Unicode standard for defining locale data) such as in the tag "es-419-x-ldml-collatio-traditio", which indicates Latin American Spanish with traditional order for sorted lists.
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Prior to RFC 4646, whole language tags were registered according to the rules in RFC 1766 and/or RFC 3066. All of these registered tags remain valid as language tags.
Many of these registered tags were made redundant by the advent of either RFC 4646 or this document. A redundant tag is a grandfathered registration whose individual subtags appear with the same semantic meaning in the registry. For example, the tag "zh-Hant" (Traditional Chinese) can now be composed from the subtags 'zh' (Chinese) and 'Hant' (Han script traditional variant). These redundant tags are maintained in the registry as records of type "redundant", mostly as a matter of historical curiousity.
The remainder of the previously registered tags are "grandfathered". These tags are classified into two groups: 'regular' and 'irregular'.
Grandfathered tags that (appear to) match the 'langtag' production in Figure 1 (Language Tag ABNF) are considered 'regular' grandfathered tags. These tags either contain subtags that do not individually appear in the registry, or their subtags appear but with a different semantic meaning: each tag, in its entirety, represents a language or collection of languages.
Grandfathered tags that do not match the 'langtag' production in the ABNF and would otherwise be invalid are considered 'irregular' grandfathered tags. With the exception of "en-GB-oed", which is a variant of "en-GB", each of them, in its entirety, represents a language.
Many of the grandfathered tags have been superseded by the subsequent addition of new subtags: each superseded record contains a Preferred-Value field that ought to be used to form language tags representing that value. For example, the tag "art-lojban" is superseded by the primary language subtag 'jbo'.
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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.
A tag is considered "well-formed" if it conforms to the ABNF (Syntax). Language tags may be well-formed in terms of syntax but not valid in terms of content. However, many operations involving language tags work well without knowing anything about the meaning or validity of the subtags.
A tag is considered "valid" if it satisfies these conditions:
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.
A tag is considered "valid" for a given extension (Extensions and the Extensions Registry) (as of a particular version, revision, and date) if it meets the criteria for "valid" above and also satisfies this condition:
Each subtag used in the extension part of the tag is valid according to the extension.
Older specifications or language tag implementations sometimes reference [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.). A wider array of tags was considered 'well-formed' under that document. Any tags that were valid for use under RFC 3066 are both 'well-formed' and 'valid' under this document's syntax; only invalid or illegal tags were well-formed by the early definition but no longer are. The language tag syntax under RFC 3066 was:
obs-language-tag = primary-subtag *( "-" subtag )
primary-subtag = 1*8ALPHA
subtag = 1*8(ALPHA / DIGIT)| Figure 2: RFC 3066 Language Tag Syntax |
Subtags designated for private use as well as private-use sequences introduced by the 'x' subtag are available for cases in which no assigned subtags are available and registration is not a suitable option. For example, one might use a tag such as "no-QQ", where 'QQ' is one of a range of private-use ISO 3166-1 codes to indicate an otherwise-undefined region. Users MUST NOT assign language tags that use subtags that do not appear in the registry other than in private-use sequences (such the subtag 'personal' in the tag "en-x-personal"). Besides not being 'valid', the user also risks collision with a future possible assignment or registrations.
Note well: although the 'Language-Tag' production appearing in this document is functionally equivalent to the one in [RFC4646] (Phillips, A. and M. Davis, “Tags for Identifying Languages,” September 2006.), it has been changed to prevent certain errors in well-formedness arising from the old 'grandfathered' production. This version of the ABNF is RECOMMENDED as a replacement for the older version.
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The IANA Language Subtag Registry ("the 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 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 registry.)
This section defines the registry along with the maintenance and update procedures associated with it, as well as a registry for extensions to language tags (Section 3.7 (Extensions and the Extensions Registry)).
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The IANA Language Subtag 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 Section 3.5 (Registration Procedure for Subtags).
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 [RFC4645] (Ewell, D., “Initial Language Subtag Registry,” September 2006.) or [registry‑update] (Ewell, D., Ed., “Update to the Language Subtag Registry,” September 2006.) do not have separate registration forms (so no forms are archived for these additions).
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The registry is a [Unicode] (Unicode Consortium, “The Unicode Consortium. The Unicode Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-49081-0),” January 2007.) text file, using the UTF-8 (Yergeau, F., “UTF-8, a transformation format of ISO 10646,” November 2003.) [RFC3629] character encoding, and consists of a series of records stored in the record-jar format (described in [record‑jar] (Raymond, E., “The Art of Unix Programming,” 2003.)). Each record, in turn, consists of a series of fields that describe the various subtags and tags.
Each field can be considered a single, logical line of characters. Each field contains a 'field-name' and a 'field-body'. These are separated by a 'field-separator'. The field-separator is a COLON character (%x3A) plus any surrounding whitespace. Each field is terminated by the newline sequence CRLF. The text in each field MUST be in Unicode Normalization Form C (NFC).
A collection of fields forms a 'record'. Records are separated by lines containing only the sequence "%%" (%x25.25).
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 [UAX14] (Freitag, A., “Unicode Standard Annex #14: Line Breaking Properties,” August 2006.).
Although the file format uses the UTF-8 encoding, fields are restricted to the printable characters from the US-ASCII (International Organization for Standardization, “ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for information interchange.,” 1991.) [ISO646] repertoire unless otherwise indicated in the description of a specific field-name (Record and Field Definitions).
The format of the registry is described by the following ABNF (per [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.)):
registry = record *("%%" CRLF record)
record = 1*field
field = ( field-name field-sep field-body CRLF )
field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)]
field-sep = *SP ":" *SP
field-body = *([[*SP CRLF] 1*SP] 1*CHARS)
CHARS = (%x21-10FFFF) ; Unicode code points
| Figure 3: Registry Format ABNF |
The sequence '..' (%x2E.2E) in a field-body denotes a range of values. Such a range represents all subtags of the same length that are in alphabetic or numeric order within that range, including the values explicitly mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and '13'.
All fields whose field-body contains a date value use the "full-date" format specified in [RFC3339] (Klyne, G., Ed. and C. Newman, “Date and Time on the Internet: Timestamps,” July 2002.). For example: "2004-06-28" represents June 28, 2004, in the Gregorian calendar.
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There are three types of records in the registry: "File-Date", "Subtag", and "Tag".
The first record in the registry is always the "File-Date" record. This record occurs only once in the file and contains a single field whose field-name is "File-Date". The field-body of this record contains the last modification date of this copy of the registry, making it possible to compare different versions of the registry. The registry on the IANA website is the most current. Versions with an older date than that one are not up-to-date.
File-Date: 2004-06-28 %%
| Figure 4: Example of the File-Date Record |
Subsequent records contain multiple fields and represent information about either subtags or tags. Both types of record have identical structure, except that "Subtag" records contain a field with a field-name of "Subtag", while, unsurprisingly, "Tag" records contain a field with a field-name of "Tag". Field-names MUST occur no more than once per record, with the exception of the 'Description', 'Comments', and sometimes the 'Prefix' field.
Each record MUST contain at least one of each of the following fields:
Each record MAY also contain the following fields:
Future versions of this document might add additional fields to the registry; implementations SHOULD ignore fields found in the registry that are not defined in this document.
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The field 'Type' contains the string identifying the record type it appears in. Values for the 'Type' field-body are: "language" (Section 2.2.1 (Primary Language Subtag)); "extlang" (Section 2.2.2 (Extended Language Subtags)); "script" (Section 2.2.3 (Script Subtag)); "region" (Section 2.2.4 (Region Subtag)); "variant" (Section 2.2.5 (Variant Subtags)); "grandfathered" or "redundant" (Section 2.2.8 (Grandfathered and Redundant Registrations)).
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The field 'Subtag' contains the subtag defined in the record. The field 'Tag' appears in records whose 'Type' is either 'grandfathered' or 'redundant' and contains a tag registered under [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.).
The 'Subtag' field-body MUST follow the casing conventions described in Section 2.1.1 (Formatting of Language Tags). All subtags use lowercase letters in the field-body, 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.
The 'Tag' field-body MUST be formatted according to the rules described in Section 2.1.1 (Formatting of Language Tags).
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The field 'Description' contains a description of the tag or subtag in the record. The 'Description' field MAY appear more than once per 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 be in any script or language.
The 'Description' field is used for identification purposes. 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. 'Description' fields don'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).
Descriptions in the registry 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 or as subsequently modified, within the bounds of the stability rules (Stability of IANA Registry Entries), via subsequent registration. The 'Description' does not replace the content of the source standard itself. 'Description' fields 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.
For subtags taken from a source standard (such as ISO 639 or ISO 15924), the 'Description' fields in the record are also initially taken from that source standard. Multiple descriptions in the source standard are split into separate 'Description' fields. The source standard's descriptions MAY be edited or modified, either prior to insertion or via the registration process, and additional or extraneous descriptions omitted or removed. Each 'Description' field MUST be unique within the record in which it appears and formatting variations of the same description SHOULD NOT occur in that specific record. For example, while the ISO 639-1 code 'fy' has both the description "Western Frisian" and and the description "Frisian, Western" in that standard, only one of these descriptions appears in the registry.
To help ensure that users do not become confused about which subtag to use, 'Description' fields assigned to a record of any specific type ('language', 'extlang', 'script', and so on) MUST be unique within that given record type with the following exception: if a particular 'Description' field occurs in multiple records of a given type, then at most one of the records can omit the 'Deprecated' field; all deprecated records that share a 'Description' MUST have the same 'Preferred-Value'; and all non-deprecated records MUST be that 'Preferred-Value'. This means that two records of the same type that share a 'Description' are also semantically equivalent and no more than one record with a given 'Description' is preferred for that meaning.
For example, consider the 'language' subtags 'zza' (Zaza) and 'diq' (Dimli). It so happens that 'zza' is a macrolanguage enclosing 'diq' and thus also has a description in ISO 639-3 of "Dimli". This description was edited to read "Dimli (macrolanguage)" in the registry record for 'zza' to prevent a collision.
By contrast, the subtags 'he' and 'iw' share a 'Description' value of "Hebrew"; this is permitted because 'iw' is deprecated and its 'Preferred-Value' is 'he'.
For fields of type 'language', the first 'Description' field appearing in the Registry corresponds whenever possible to the Reference Name assigned by ISO 639-3. This helps facilitate cross-referencing between ISO 639 and the registry.
When creating or updating a record due to the action of one of the source standards, the Language Subtag Reviewer 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 for consideration.
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The field 'Deprecated' contains the date the record was deprecated and MAY be added, changed, or removed from any record via the maintenance process described in Section 3.3 (Maintenance of the Registry) or via the registration process described in Section 3.5 (Registration Procedure for Subtags). 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. 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.
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. Some subtags and some grandfathered or redundant tags were deprecated before the initial creation of the registry. The exact rules for this appear in Section 2 of [RFC4645] (Ewell, D., “Initial Language Subtag Registry,” September 2006.). Note that these records have a 'Deprecated' field with an earlier date then the corresponding 'Added' field!
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The field 'Preferred-Value' contains a mapping between the record in which it appears and another tag or subtag (depending on the record's 'Type'). The value in this field is used for canonicalization (see Section 4.5 (Canonicalization of Language Tags)). In cases where the subtag or tag also has a 'Deprecated' field, then the 'Preferred-Value' is RECOMMENDED as the best choice to represent the value of this record when selecting a language tag.
Records containing a Preferred-Value fall into one of these four groups:
Records other than those of type 'extlang' 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.
For records of type 'extlang', the 'Preferred-Value' field appears without a corresponding 'Deprecated' field. An implementation MAY ignore these preferred value mappings, although if it ignores the mapping, it SHOULD do so consistently. It SHOULD also treat the Preferred-Value as equivalent to the mapped item. For example, the tags "zh-yue-Hant-HK" and "yue-Hant-HK" are semantically equivalent and ought to be treated as if they were the same tag.
Occasionally the deprecated code is preferred in certain contexts. For example, both "iw" and "he" can be used in the Java programming language, but "he" is converted on input to "iw", which is thus the canonical form in Java.
'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. For example, the region subtag 'YD' (Democratic Yemen) was deprecated in favor of the subtag 'YE' (Yemen) when those two countries unified in 1990.
A 'Preferred-Value' MAY be added to, changed, or removed from records according to the rules in Section 3.3 (Maintenance of the Registry). 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.
The 'Preferred-Value' fields in records of type "grandfathered" and "redundant" each contain an "extended language range" ([RFC4647] (Phillips, A. and M. Davis, “Matching of Language Tags,” September 2006.)) that is 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 [RFC4646] (Phillips, A. and M. Davis, “Tags for Identifying Languages,” September 2006.) was adopted. For example, the tag "no-nyn" was deprecated in favor of the ISO 639-1-defined language code 'nn'.
The 'Preferred-Value' field in subtag records of type "extlang" also contains an "extended language range". This allows the subtag to be deprecated in favor of either a single primary language subtag or a new language-extlang sequence.
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.
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 Section 3.5 (Registration Procedure for Subtags), although anyone MAY request such changes. For example:
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'.
Suppose that a registered language 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'.
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The 'Prefix' field contains an "extended language range" (see: [RFC4647] (Phillips, A. and M. Davis, “Matching of Language Tags,” September 2006.)) 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.
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).
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. Fields of type 'extlang' MUST have exactly one Prefix field.
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.
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The field 'Suppress-Script' contains a script subtag (whose record appears in the registry). The field 'Suppress-Script' MUST appear only in records whose 'Type' field-body is either 'language' or 'extlang'. 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. The subtag for such a script therefore adds no distinguishing information to a language tag and thus SHOULD NOT be used for most documents in that language. Omitting the script subtag indicated by this field helps ensure greater compatibility between the language tags generated according to the rules in this document and language tags and tag processors or consumers based on RFC 3066. For example, virtually all Icelandic documents are written in the Latin script, making the subtag 'Latn' redundant in the tag "is-Latn".
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.
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The field 'Macrolanguage' contains a primary language subtag (whose record appears in the registry). This field indicates a language that encompasses this subtag's language according to assignments made by ISO 639-3.
ISO 639-3 labels some languages in the registry as "macrolanguages". ISO 639-3 defines the term "Macrolanguage" to mean "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 individual languages that were found to correspond to more than one language in ISO 639-3.
A language contained within a macrolanguage is called an "encompassed language". The record for each encompassed language contains a 'Macrolanguage' field in the registry; the macrolanguages themselves are not specially marked. Note that some encompassed languages have ISO 639-1 or ISO 639-2 codes.
The Macrolanguage field can only occur in records of type 'language' or 'extlang'. 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. For more information on the use of this field and choosing between macrolanguage and encompassed language subtags, see Section 4.1.1 (Tagging Encompassed Languages).
For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' (Norwegian). For more information see Section 4.1 (Choice of Language Tag).
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The field 'Scope' contains classification information about a primary or extended language subtag derived from ISO 639. Most languages have a scope of 'individual', which means that the language is not a macrolanguage, collection, special code, or private use. That is, it is what one would normally consider to be 'a language'. Any primary or extended language subtag that has no 'Scope' field is an individual language.
Scope information can sometimes be helpful in selecting language tags, since it indicates the purpose or "scope" of the code assignment within ISO 639. The available values are:
The Scope field MAY appear in records of type 'language' or 'extlang'. Note that many of the prefixes for extended language subtags will have a Scope of 'macrolanguage' (although some will not) and that many languages that have a Scope of 'macrolanguage' will have extended language subtags associated with them.
The Scope field MAY be added, modified, or removed via the registration process, provided the change mirrors changes by ISO 639 to the assignment's classification. Such a change is expected to be rare.
For example, the primary language subtag 'zh' (Chinese) has a Scope of 'macrolanguage', while its enclosed language 'nan' (Min Nan Chinese) has a Scope of 'individual'. The special value 'und' (Undetermined) has a Scope of 'special'. The ISO 639-5 collection 'gem' (Germanic languages) has a Scope of 'collection'.
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The field 'Comments' contains 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.
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 as an aid to usage. Large amounts of information about the use, history, or general background of a subtag are frowned upon, as these generally belong in a registration request rather than in the registry.
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The Language Subtag Reviewer moderates the ietf-languages mailing list, responds to requests for registration, and performs the other registry maintenance duties described in Section 3.3 (Maintenance of the Registry). 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.
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.
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 [RFC2026] (Bradner, S., “The Internet Standards Process -- Revision 3,” October 1996.)). The IESG can reverse or overturn the decisions of the Language Subtag Reviewer, provide guidance, or take other appropriate actions.
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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 Section 3.5 (Registration Procedure for Subtags). 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.
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.
The Language Subtag Reviewer MUST ensure that new subtags meet the requirements elsewhere in this document (and most especially in Section 3.4 (Stability of IANA Registry Entries)) 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.
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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.
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:
- A.
- 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'. Note that languages given an ISO 639-1 code cannot be given extended language subtags, even if encompassed by a macrolanguage.
- B.
- Codes assigned by ISO 639-3 or ISO 639-5 that do not conflict with existing three-letter primary language subtags and which do not have ISO 639-1 codes assigned (or expected to be assigned) are entered into the IANA registry as new records of type 'language'. Note that these two standards now comprise a superset of ISO 639-2 codes. Codes that have a defined "macrolanguage" mapping at the time of their registration MUST contain a "Macrolanguage" field.
- C.
- Codes assigned by ISO 639-3 MAY also be considered for an extended language subtag registration. Note that they MUST be assigned a primary language subtag record of type 'language' even when an 'extlang' record is proposed. When considering extended language subtag assignment, these criteria apply:
- If a language has a macrolanguage mapping, and that macrolanguage has other encompassed languages that are assigned extended language subtags, then the new language SHOULD have an 'extlang' record assigned to it as well. For example, any language with a macrolanguage of 'zh' or 'ar'.
- 'Extlang' records SHOULD NOT be created for languages if other languages encompassed by the macrolanguage do not also include 'extlang' records. For example, if a new Serbo-Croatian ('sh') language were registered, it would not get an extlang record because other languages encompassed such as Serbian ('sr') do not include one in the registry.
- Sign languages SHOULD have an 'extlang' record with a 'Prefix' of 'sgn'.
- 'Extlang' records MUST NOT be created for items already in the registry. Extended language subtags will only be considered at the time of initial registration.
- Extended language subtag records MUST include the fields 'Prefix' and 'Preferred-Value' with field-values assigned as described in Section 2.2.2 (Extended Language Subtags).
- D.
- Any other codes assigned by ISO 639-2 that do not conflict with existing three-letter primary or extended language subtags and which do not have ISO 639-1 two-letter codes assigned are entered into the IANA registry as new records of type 'language'. This type of registration is not supposed to occur in the future.
- For 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').
- A.
- For ISO 639 codes, if the newly assigned code's meaning is not represented by a subtag in the IANA registry, the Language Subtag Reviewer, as described in Section 3.5 (Registration Procedure for Subtags), SHALL prepare a proposal for entering in the IANA registry as soon as practical a registered language subtag as an alternate value for the new code. The form of the registered language subtag will be at the discretion of the Language Subtag Reviewer and MUST conform to other restrictions on language subtags in this document.
- B.
- For all subtags whose meaning is derived from an external standard (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 registration authority (RA) has adopted a similar stability policy.
- C.
- For ISO 15924 codes, if the newly assigned code's meaning is not represented by a subtag in the IANA registry, the Language Subtag Reviewer, as described in Section 3.5 (Registration Procedure for Subtags), 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.
- D.
- 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.
- E.
- 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 Section 3.5 (Registration Procedure for Subtags), SHALL prepare a proposal for entering the appropriate UN M.49 country code as an entry in the IANA registry.
- F.
- 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.