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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
2.2.
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 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 Definitions
3.1.3.
Subtag and Tag Fields
3.1.4.
Description Field
3.1.5.
Deprecated Field
3.1.6.
Preferred-Value Field
3.1.7.
Prefix Field
3.1.8.
Suppress-Script Field
3.1.9.
Macrolanguage Field
3.1.10.
Scope Field
3.1.11.
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.
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.
In addition, knowledge about the particular language used by some piece of information content might be useful or even required by some types of processing; for example, spell-checking, computer-synthesized speech, Braille transcription, or high-quality print renderings.
One means of indicating the language used is by labeling the information content with an identifier or "tag". These tags can be used to specify user preferences when selecting information content, or for labeling additional attributes of content and associated resources.
Tags can also be used to indicate additional language attributes of content. For example, indicating specific information about the dialect, writing system, or orthography used in a document or resource may enable the user to obtain information in a form that they can understand, or 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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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 [RFC5234] (Crocker, D. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” January 2008.) %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.
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 RFC 3066 (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.) [RFC3066], a fixed list that can never change, are the only exception to this ability to infer meaning from subtag structure.
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
/ privateuse ; private use tag
/ irregular ; tags grandfathered by rule
langtag = (language
["-" script]
["-" region]
*("-" variant)
*("-" extension)
["-" privateuse])
language = 2*3ALPHA ; shortest ISO 639 code
[extlang] ; sometimes followed by
; extended language subtags
/ 4ALPHA ; reserved for future use
/ 5*8ALPHA ; 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))
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" / "sgn-BE-FR" / "sgn-BE-NL"
/ "sgn-CH-DE"
alphanum = (ALPHA / DIGIT) ; letters and numbers
| Figure 1: Language Tag ABNF |
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 Appendix B (Examples of Language Tags (Informative)).
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.
For example:
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.
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.
Note that 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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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:
The definitions in this section apply to the various subtags within the language tags defined by this document, excepting those "grandfathered" tags defined in Section 2.2.8 (Grandfathered Registrations).
Language tags are designed so that each subtag type has unique length and content restrictions. These make identification of the subtag's type possible, even if the content of the subtag itself is unrecognized. This allows tags to be parsed and processed without reference to the latest version of the underlying standards or the IANA registry and makes the associated exception handling when parsing tags simpler.
Subtags in the IANA registry that do not come from an underlying standard can only appear in specific positions in a tag. Specifically, they can only occur as primary language subtags or as variant subtags.
Note that sequences of private use and extension subtags MUST occur at the end of the sequence of subtags and MUST NOT be interspersed with subtags defined elsewhere in this document.
Single-letter and single-digit subtags are reserved for current or future use. These include the following current uses:
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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:
- 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.)
Note: For languages that 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.
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.
Note: To avoid problems with versioning and subtag choice as experienced during the transition between RFC 1766 and RFC 3066, as well as the canonical nature of subtags defined by this document, the ISO 639 Registration Authority Joint Advisory Committee (ISO 639/RA-JAC) has included the following statement in [iso639.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."
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 be invalidated if ISO 639-1 were to assign a two-character code to the Hawaiian language at a later date.
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.
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Extended language subtags are used to identify certain specially-selected languages that, for various historical reasons, are closely identified with 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. Some 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:
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 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.
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 [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).
"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".
"sl-nedis" represents the Natisone or Nadiza dialect of Slovenian.
"de-CH-1996" represents German as used in Switzerland and as written using the spelling reform beginning in the year 1996 C.E.
Most variants that share a prefix are mutually exclusive. For example, the German orthographic variations '1996' and '1901' SHOULD NOT be used in the same tag, as they represent the dates of different spelling reforms. A variant that can meaningfully be used in combination with another variant SHOULD include a 'Prefix' field in its registry record that lists that other variant. For example, if another German variant 'example' were created that made sense to use with '1996', then 'example' should include two Prefix fields: "de" and "de-1996".
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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 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"
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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. 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.
Grandfathered tags contain one or more subtags that are not defined in the Language Subtag Registry (see Section 3 (Registry Format and Maintenance)). Redundant tags consist entirely of subtags defined above and whose independent registration was superseded by [RFC4646] (Phillips, A. and M. Davis, “Tags for Identifying Languages,” September 2006.). For more information see Section 3.8 (Update of the Language Subtag Registry).
Some grandfathered tags are "regular" in that they match the 'langtag' production in Figure 1 (Language Tag 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.
The remaining grandfathered tags are "irregular" and do not match the 'langtag' production. These are listed in the 'irregular' production in Figure 1 (Language Tag 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.
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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. Irregular grandfathered tags are now listed in the 'irregular' production.
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 language tag implementations sometimes reference [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.). 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:
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 or 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 and 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"). Not only is such assignment nonconformant, it also risks collision with a future possible assignment or registration.
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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This section defines the Language Subtag Registry and the maintenance and update procedures associated with it, as well as a registry for extensions to language tags (Section 3.7 (Extensions and the Extensions Registry)).
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.)
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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 Section 3.5 (Registration Procedure for Subtags).
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 [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 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. 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.) [Unicode] text file, using the UTF-8 (Yergeau, F., “UTF-8, a transformation format of ISO 10646,” November 2003.) [RFC3629] character encoding.
Each field can be considered a single, logical line 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.) [Unicode] 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).
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 specific field description below.
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-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
| 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.
| TOC |
There are three types of records in the registry: "File-Date", "Subtag", and "Tag" records.
The first record in the registry is a "File-Date" record. This record contains the single field whose field-name is "File-Date" (see Figure 3 (Registry Format ABNF)). 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 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:
Each record MAY also contain the following fields:
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.
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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.
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.
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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, 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.
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).
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 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 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.
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.
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.
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The field 'Deprecated' 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. 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:
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.
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.
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' field in records of type "grandfathered" and "redundant" contains language ranges 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 [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" use the same format as grandfathered or redundant tags. 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'.
| TOC |
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.
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 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".
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. This information can sometimes be helpful in selecting language tags, since it indicates the purpose of the code assignment within ISO 639. The available values are:
The Scope field MUST appear in all records of type 'language' or 'extlang'. Records of type 'extlang' MUST NOT include a value other than 'individual'. Note that most of the prefixes for extended language subtags will have a Scope of 'macrolanguage' (although some will not).
The Scope fied MAY be modified via the registration process, should ISO 639 change 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' 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.
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.
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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:
- 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.
Note: The redundant and grandfathered entries together are the complete list of tags registered under [RFC3066] (Alvestrand, H., “Tags for the Identification of Languages,” January 2001.). The redundant tags are those that can now be formed using the subtags defined in the registry together with the rules of Section 2.2 (Language Subtag Sources and Interpretation). 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.
The set of redundant and grandfathered tags is permanent and stable: new entries in this section MUST NOT be added and existing entries MUST NOT be removed. Records of type 'grandfathered' MAY have their type converted to 'redundant'; see item 12 in Section 3.6 (Possibilities for Registration) for more information. The decision-making process about which tags were initially grandfathered and which were made redundant is described in [RFC4645] (Ewell, D., “Initial Language Subtag Registry,” September 2006.).
RFC 3066 tags that were deprecated prior to the adoption of [RFC4646] (Phillips, A. and M. Davis, “Tags for Identifying Languages,” September 2006.) are part of the list of grandfathered tags, and their component subtags were not included as registered variants (although they remain eligible for registration). For example, the tag "art-lojban" was deprecated in favor of the language subtag 'jbo'.
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The procedure given here MUST be used by anyone who wants to use a subtag not currently in the IANA Language Subtag Registry.
Only subtags of type 'language' and 'variant' will be considered for independent registration of new subtags. 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 Section 3.3 (Maintenance of the Registry). Stability provisions are described in Section 3.4 (Stability of IANA Registry Entries).
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 Section 3.4 (Stability of IANA Registry Entries). Changes to all other fields in the IANA registry are NOT permitted.
Registering a new subtag or requesting modifications to an existing tag or subtag starts with the requester filling out
the registration form reproduced below. Note that each response is not limited
in size so that the request can adequately describe the registration.
The fields in the "Record Requested" section SHOULD follow the requirements in Section 3.1 (Format of the IANA Language Subtag Registry).
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:
| Figure 5: The Language Subtag Registration Form |
Examples of completed registration forms can be found in Appendix C (Examples of Registration Forms) or online at http://www.iana.org/assignments/lang-subtags-templates/.
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 Section 3.1 (Format of the IANA Language Subtag Registry)) the modified form MUST also be sent to <ietf-languages@iana.org> at least one week prior to submission to IANA.
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.
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 Section 3.1 (Format of the IANA Language Subtag Registry). The Reviewer MUST also ensure that an appropriate File-Date record is included in the request, to assist IANA when updating the registry (see Section 5.1 (Language Subtag Registry)).
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.
Extended language subtags (type 'extlang'), by definition, are always enclosed by another language. All records of type 'extlang' MUST, therefore, contain a 'Prefix' field at the time of registration. This prefix value can never be altered or removed.
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.
The 'Prefix' field for a given registered variant subtag exists in the IANA registry as a guide to usage. Additional prefixes MAY be added by filing an additional registration form. In that form, the "Any other relevant information:" field MUST indicate that it is the addition of a prefix.
Requests to add a 'Prefix' field 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 '1994' so that the tag "de-1994" represented some German dialect or orthographic form would be rejected. The '1994' subtag represents a particular Slovenian orthography and the additional registration would change or blur the semantic meaning assigned to the subtag. A separate subtag SHOULD be proposed instead.
The 'Description' field MUST contain a description of the tag being registered written or transcribed into the Latin script; it MAY also include a description in a non-Latin script. The 'Description' field is used for identification purposes and doesn't necessarily represent the actual native name of the language or variation or to be in any particular language.
While the 'Description' field itself is not guaranteed to be stable and errata corrections MAY be undertaken from time to time, attempts to provide translations or transcriptions of entries in the registry itself will probably be frowned upon by the community or rejected outright, as changes of this nature have an impact on the provisions in Section 3.4 (Stability of IANA Registry Entries).
When the two-week period has passed, the Language Subtag Reviewer MUST take one of the following actions: