Network Working Group A. Phillips, Ed. Internet-Draft Lab126 Obsoletes: 4646 (if approved) M. Davis, Ed. Intended status: BCP Google Expires: March 21, 2009 September 17, 2008 Tags for Identifying Languages draft-ietf-ltru-4646bis-17 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 21, 2009. Phillips & Davis Expires March 21, 2009 [Page 1] Internet-Draft language-tags September 2008 Abstract This document describes the structure, content, construction, and semantics of language tags for use in cases where it is desirable to indicate the language used in an information object. It also describes how to register values for use in language tags and the creation of user-defined extensions for private interchange. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.1. Formatting of Language Tags . . . . . . . . . . . . . 7 2.2. Language Subtag Sources and Interpretation . . . . . . . . 8 2.2.1. Primary Language Subtag . . . . . . . . . . . . . . . 10 2.2.2. Extended Language Subtags . . . . . . . . . . . . . . 12 2.2.3. Script Subtag . . . . . . . . . . . . . . . . . . . . 13 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 14 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 16 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 17 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 18 2.2.8. Grandfathered and Redundant Registrations . . . . . . 19 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 20 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 22 3.1. Format of the IANA Language Subtag Registry . . . . . . . 22 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 22 3.1.2. Record and Field Definitions . . . . . . . . . . . . . 23 3.1.3. Type Field . . . . . . . . . . . . . . . . . . . . . . 26 3.1.4. Subtag and Tag Fields . . . . . . . . . . . . . . . . 27 3.1.5. Description Field . . . . . . . . . . . . . . . . . . 27 3.1.6. Deprecated Field . . . . . . . . . . . . . . . . . . . 29 3.1.7. Preferred-Value Field . . . . . . . . . . . . . . . . 29 3.1.8. Prefix Field . . . . . . . . . . . . . . . . . . . . . 31 3.1.9. Suppress-Script Field . . . . . . . . . . . . . . . . 32 3.1.10. Macrolanguage Field . . . . . . . . . . . . . . . . . 33 3.1.11. Scope Field . . . . . . . . . . . . . . . . . . . . . 33 3.1.12. Comments Field . . . . . . . . . . . . . . . . . . . . 34 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 35 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 35 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 36 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 42 3.6. Possibilities for Registration . . . . . . . . . . . . . . 46 3.7. Extensions and the Extensions Registry . . . . . . . . . . 49 3.8. Update of the Language Subtag Registry . . . . . . . . . . 52 4. Formation and Processing of Language Tags . . . . . . . . . . 53 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 53 Phillips & Davis Expires March 21, 2009 [Page 2] Internet-Draft language-tags September 2008 4.1.1. Tagging Encompassed Languages . . . . . . . . . . . . 57 4.1.2. Using Extended Language Subtags . . . . . . . . . . . 58 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 60 4.3. Lists of Languages . . . . . . . . . . . . . . . . . . . . 62 4.4. Length Considerations . . . . . . . . . . . . . . . . . . 63 4.4.1. Working with Limited Buffer Sizes . . . . . . . . . . 63 4.4.2. Truncation of Language Tags . . . . . . . . . . . . . 64 4.5. Canonicalization of Language Tags . . . . . . . . . . . . 65 4.6. Considerations for Private Use Subtags . . . . . . . . . . 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 69 5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 69 5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 70 6. Security Considerations . . . . . . . . . . . . . . . . . . . 72 7. Character Set Considerations . . . . . . . . . . . . . . . . . 73 8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 74 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 78 9.1. Normative References . . . . . . . . . . . . . . . . . . . 78 9.2. Informative References . . . . . . . . . . . . . . . . . . 79 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 81 Appendix B. Examples of Language Tags (Informative) . . . . . . . 82 Appendix C. Examples of Registration Forms . . . . . . . . . . . 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 87 Intellectual Property and Copyright Statements . . . . . . . . . . 88 Phillips & Davis Expires March 21, 2009 [Page 3] Internet-Draft language-tags September 2008 1. Introduction Human beings on our planet have, past and present, used a number of languages. There are many reasons why one would want to identify the language used when presenting or requesting information. 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], which replaced [RFC3066] and its predecessor [RFC1766]. For a list of changes in this document, see Section 8. 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]. Phillips & Davis Expires March 21, 2009 [Page 4] Internet-Draft language-tags September 2008 2. The Language Tag 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. 2.1. Syntax 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 [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] and are a fixed list that can never change. The syntax of the language tag in ABNF [RFC5234] 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 Phillips & Davis Expires March 21, 2009 [Page 5] Internet-Draft language-tags September 2008 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" Phillips & Davis Expires March 21, 2009 [Page 6] Internet-Draft language-tags September 2008 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. 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] refers to octets, the language tags described in this document are sequences of characters from the US-ASCII [ISO646] 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] encoding of [Unicode]. 2.1.1. Formatting of Language Tags 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. Phillips & Davis Expires March 21, 2009 [Page 7] Internet-Draft language-tags September 2008 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: o [ISO639-1] recommends that language codes be written in lowercase ('mn' Mongolian). o [ISO15924] recommends that script codes use lowercase with the initial letter capitalized ('Cyrl' Cyrillic). o [ISO3166-1] recommends that country codes be capitalized ('MN' Mongolia). 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'. 2.2. Language Subtag Sources and Interpretation The namespace of language tags and their subtags is administered by the Internet Assigned Numbers Authority (IANA) [RFC2860] according to the rules in Section 5 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: Phillips & Davis Expires March 21, 2009 [Page 8] Internet-Draft language-tags September 2008 o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or "az-Arab-IR". Examples of tags in this document are enclosed in double-quotes ("en-US"). o "Subtag" refers to a specific section of a tag, delimited by hyphen, such as the subtags 'zh', 'Hant', and 'CN' in the tag "zh- Hant-CN". Examples of subtags in this document are enclosed in single quotes ('Hant'). o "Code" refers to values defined in external standards (and which are used as subtags in this document). For example, 'Hant' is an [ISO15924] script code that was used to define the 'Hant' script subtag for use in a language tag. Examples of codes in this document are enclosed in single quotes ('en', 'Hant'). 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: o The single-letter subtag 'x' introduces a sequence of private use subtags. The interpretation of any private use subtags is defined solely by private agreement and is not defined by the rules in this section or in any standard or registry defined in this document. o The single-letter subtag 'i' is used by some grandfathered tags, such as "i-default", where it always appears in the first position and cannot be confused with an extension. o All other single-letter and single-digit subtags are reserved to introduce standardized extension subtag sequences as described in Section 3.7. Phillips & Davis Expires March 21, 2009 [Page 9] Internet-Draft language-tags September 2008 2.2.1. Primary Language Subtag The primary language subtag is the first subtag in a language tag and cannot be omitted, with two exceptions: o The single-character subtag 'x' as the primary subtag indicates that the language tag consists solely of subtags whose meaning is defined by private agreement. For example, in the tag "x-fr-CH", the subtags 'fr' and 'CH' do not represent the French language or the country of Switzerland (or any other value in the IANA registry) unless there is a private agreement in place to do so. See Section 4.6. o The single-character subtag 'i' is used by some grandfathered tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other grandfathered tags have a primary language subtag in their first position.) The following rules apply to the primary language subtag: 1. Two-character primary language subtags were defined in the IANA registry according to the assignments found in the standard "ISO 639-1:2002, Codes for the representation of names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using assignments subsequently made by the ISO 639-1 registration authority (RA) or governing standardization bodies. 2. Three-character primary language subtags in the IANA registry were defined according to the assignments found in one of these additional ISO 639 parts or assignments subsequently made by the relevant ISO 639 registration authorities or governing standardization bodies: A. "ISO 639-2:1998 - Codes for the representation of names of languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2] 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] 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] 3. The subtags in the range 'qaa' through 'qtz' are reserved for private use in language tags. These subtags correspond to codes reserved by ISO 639-2 for private use. These codes MAY be used for non-registered primary language subtags (instead of using Phillips & Davis Expires March 21, 2009 [Page 10] Internet-Draft language-tags September 2008 private use subtags following 'x-'). Please refer to Section 4.6 for more information on private use subtags. 4. Four-character language subtags are reserved for possible future standardization. 5. Any language subtags of 5 to 8 characters in length in the IANA registry were defined via the registration process in Section 3.5 and MAY be used to form the primary language subtag. An example of what such a 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. At the time this document was created, there were no examples of this kind of subtag and future registrations of this type are discouraged: primary languages are strongly RECOMMENDED for registration with ISO 639, and proposals rejected by ISO 639/ RA-JAC will be closely scrutinized before they are registered with IANA. 6. Other values MUST NOT be assigned to the primary subtag except by revision or update of this document. 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. 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. Phillips & Davis Expires March 21, 2009 [Page 11] Internet-Draft language-tags September 2008 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]: "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." 2.2.2. Extended Language Subtags 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: 1. Extended language subtags consist solely of three-letter subtags. All extended language subtag records defined in the registry were defined according to the assignments found in [ISO639-3]. Language collections and groupings, such as defined in [ISO639-5] are specifically excluded from being extended language subtags. 2. Extended language subtag records MUST include exactly one 'Prefix' field indicating an appropriate subtag or sequence of subtags for that extended language subtag. 3. Extended language subtag records MUST include a 'Preferred- Value'. The 'Preferred-Value' and 'Subtag' fields MUST be identical. 4. Although the ABNF production 'extlang' permits up to three extended language tags in the language tag, extended language subtags MUST NOT include another extended language subtag in their Prefix. That is, the second and third extended language subtag positions in a language tag are permanently reserved and tags that include subtags in that position are invalid. Phillips & Davis Expires March 21, 2009 [Page 12] Internet-Draft language-tags September 2008 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"). 2.2.3. Script Subtag 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: 1. Script subtags MUST follow any primary and extended language subtags and MUST precede any other type of subtag. 2. Script subtags consist of four letters and were defined according to [ISO15924]--"Codes for the representation of the names of scripts": alpha-4 script codes, or subsequently assigned by the ISO 15924 registration authority or governing standardization bodies, denoting the script or writing system used in conjunction with this language. Only codes assigned by ISO 15924 will be considered for registration. 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private use in language tags. These subtags correspond to codes reserved by ISO 15924 for private use. These codes MAY be used for non- registered script values. Please refer to Section 4.6 for more information on private use subtags. 4. There MUST be at most one script subtag in a language tag, and the script subtag SHOULD be omitted when it adds no distinguishing value to the tag or when the primary or extended language subtag's record in the subtag registry includes a 'Suppress-Script' field listing the applicable script subtag. For example: "sr-Latn" represents Serbian written using the Latin script. Phillips & Davis Expires March 21, 2009 [Page 13] Internet-Draft language-tags September 2008 2.2.4. Region Subtag 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: 1. Region subtags MUST follow any primary language, extended language, or script subtags and MUST precede any other type of subtag. 2. Two-letter region subtags were defined according to the assignments found in [ISO3166-1] ("Codes for the representation of names of countries and their subdivisions -- Part 1: Country codes") using the list of alpha-2 country codes, or using assignments subsequently made by the ISO 3166-1 maintenance agency or governing standardization bodies. In addition, the codes that are "exceptionally reserved" (as opposed to "assigned") in ISO 3166-1 were also defined in the registry, with the exception of 'UK', which is an exact synonym for the assigned code 'GB'. 3. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are reserved for private use in language tags. These subtags correspond to codes reserved by ISO 3166 for private use. These codes MAY be used for private use region subtags (instead of using a private use subtag sequence). Please refer to Section 4.6 for more information on private use subtags. 4. Three-character region subtags consist solely of digit (number) characters and were defined according to the assignments found in UN Standard Country or Area Codes for Statistical Use [UN_M.49] or assignments subsequently made by the governing standards body. Not all of the UN M.49 codes are defined in the IANA registry. The following rules define which codes are entered into the registry as valid subtags: 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. Phillips & Davis Expires March 21, 2009 [Page 14] Internet-Draft language-tags September 2008 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 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] but not presently registered MAY be entered into the IANA registry via the process described in Section 3.5. 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. 5. The alphanumeric codes in Appendix X of the UN document MUST NOT be entered into the registry and MUST NOT be used to form language tags. (At the time this document was created, these values matched the ISO 3166-1 alpha-2 codes.) 6. There MUST be at most one region subtag in a language tag and the region subtag MAY be omitted, as when it adds no distinguishing value to the tag. 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'). Phillips & Davis Expires March 21, 2009 [Page 15] Internet-Draft language-tags September 2008 "es-419" represents Spanish ('es') appropriate to the UN-defined Latin America and Caribbean region ('419'). 2.2.5. Variant Subtags 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: 1. Variant subtags MUST follow any primary language, extended language, script, or region subtags, and MUST precede any extension or private use subtag sequences. 2. Variant subtags, as a collection, are not associated with any particular external standard. The meaning of variant subtags in the registry is defined in the course of the registration process defined in Section 3.5. Note that any particular variant subtag might be associated with some external standard. However, association with a standard is not required for registration. 3. More than one variant MAY be used to form the language tag. 4. Variant subtags MUST be registered with IANA according to the rules in Section 3.5 of this document before being used to form language tags. In order to distinguish variants from other types of subtags, registrations MUST meet the following length and content restrictions: 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be at least five characters long. 2. Variant subtags that begin with a digit (0-9) MUST be at least four characters long. 5. The same variant subtag MUST NOT be used more than once within a language tag. * For example, the tag "de-DE-1901-1901" is not valid. 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" Phillips & Davis Expires March 21, 2009 [Page 16] Internet-Draft language-tags September 2008 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. 2.2.6. Extension Subtags 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. The following rules apply to extensions: 1. An extension MUST follow at least a primary language subtag. That is, a language tag cannot begin with an extension. Extensions extend language tags, they do not override or replace them. For example, "a-value" is not a well-formed language tag, while "de-a-value" is. Note that extensions cannot be used in tags that are entirely private use (that is, tags starting with "x-"). 2. Extension subtags are separated from the other subtags defined in this document by a single-character subtag (called a "singleton"). The singleton MUST be one allocated to a registration authority via the mechanism described in Section 3.7 and MUST NOT be the letter 'x', which is reserved for private use subtag sequences. 3. Each singleton subtag MUST appear at most one time in each tag (other than as a private use subtag). That is, singleton subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a-ccc" is invalid because the subtag 'a' appears twice. Note that the tag "en-a-bbb-x-a-ccc" is valid because the second appearance of the singleton 'a' is in a private use sequence. Phillips & Davis Expires March 21, 2009 [Page 17] Internet-Draft language-tags September 2008 4. Extension subtags MUST meet whatever requirements are set by the document that defines their singleton prefix and whatever requirements are provided by the maintaining authority. Note that there might not be a registry of these subtags and validating processors are not required to validate extensions. 5. Each extension subtag MUST be from two to eight characters long and consist solely of letters or digits, with each subtag separated by a single '-'. Case distinctions are ignored in extensions (as with any language subtag) and normalized subtags of this type are expected to be in lowercase. 6. Each singleton MUST be followed by at least one extension subtag. For example, the tag "tlh-a-b-foo" is invalid because the first singleton 'a' is followed immediately by another singleton 'b'. 7. Extension subtags MUST follow all primary language, extended language, script, region, and variant subtags in a tag and MUST precede any private-use subtag sequences. 8. All subtags following the singleton and before another singleton are part of the extension. Example: In the tag "fr-a-Latn", the subtag 'Latn' does not represent the script subtag 'Latn' defined in the IANA Language Subtag Registry. Its meaning is defined by the extension 'a'. 9. In the event that more than one extension appears in a single tag, the tag SHOULD be canonicalized as described in Section 4.5. 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" 2.2.7. Private Use Subtags 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: 1. Private use subtags are separated from the other subtags defined in this document by the reserved single-character subtag 'x'. 2. Private use subtags MUST conform to the format and content constraints defined in the ABNF for all subtags, that is, they MUST consist solely of letters and digits and not exceed eight characters in length. Phillips & Davis Expires March 21, 2009 [Page 18] Internet-Draft language-tags September 2008 3. Private use subtags MUST follow all primary language, extended language, script, region, variant, and extension subtags in the tag. Another way of saying this is that all subtags following the singleton 'x' MUST be considered private use. Example: The subtag 'US' in the tag "en-x-US" is a private use subtag. 4. A tag MAY consist entirely of private use subtags. 5. No source is defined for private use subtags. Use of private use subtags is by private agreement only. 6. Private use subtags are NOT RECOMMENDED where alternatives exist or for general interchange. See Section 4.6 for more information on private use subtag choice. For example: The Unicode Consortium defines a set of private use extensions in LDML ([UTS35], 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. 2.2.8. Grandfathered and Redundant Registrations 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 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' Phillips & Davis Expires March 21, 2009 [Page 19] Internet-Draft language-tags September 2008 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'. 2.2.9. Classes of Conformance 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 (Section 2.1). 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: o The tag is well-formed. o The tag is either in the list of grandfathered tags or all of its primary language, extended language, script, region, and variant subtags appear in the IANA language subtag registry as of the particular registry date. o There are no duplicate variant subtags. o There are no duplicate singleton (extension) subtags. 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 (Section 3.7) (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 Phillips & Davis Expires March 21, 2009 [Page 20] Internet-Draft language-tags September 2008 reference [RFC3066]. 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], 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. Phillips & Davis Expires March 21, 2009 [Page 21] Internet-Draft language-tags September 2008 3. Registry Format and Maintenance 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). 3.1. Format of the IANA Language Subtag Registry 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. 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] or [registry-update] do not have separate registration forms (so no forms are archived for these additions). 3.1.1. File Format The registry is a [Unicode] text file, using the UTF-8 [RFC3629] character encoding, and consists of a series of records stored in the record-jar format (described in [record-jar]). 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). Phillips & Davis Expires March 21, 2009 [Page 22] Internet-Draft language-tags September 2008 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]. Although the file format uses the UTF-8 encoding, fields are restricted to the printable characters from the US-ASCII [ISO646] repertoire unless otherwise indicated in the description of a specific field-name (Section 3.1.2). The format of the registry is described by the following ABNF (per [RFC5234]): 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]. For example: "2004-06-28" represents June 28, 2004, in the Gregorian calendar. 3.1.2. Record and Field Definitions 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 Phillips & Davis Expires March 21, 2009 [Page 23] Internet-Draft language-tags September 2008 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: o 'Type' * Type's field-body MUST consist of one of the following strings: "language", "extlang", "script", "region", "variant", "grandfathered", and "redundant", and denotes the type of tag or subtag. o Either 'Subtag' or 'Tag' * Subtag's field-body contains the subtag being defined. This field MUST appear in all records whose 'Type' has one of these values: "language", "extlang", "script", "region", or "variant". * Tag's field-body contains a complete language tag. This field MUST appear in all records whose 'Type' has one of these values: "grandfathered" or "redundant". If the 'Type' is "grandfathered", then the 'Tag' field-body will be one of the tags listed in either the 'regular' or 'irregular' production in found in Section 2.1. o Description * Description's field-body contains a non-normative description of the subtag or tag. Phillips & Davis Expires March 21, 2009 [Page 24] Internet-Draft language-tags September 2008 o Added * Added's field-body contains the date the record was registered or, in the case of grandfathered or redundant tags, the date the corresponding tag was registered under the rules of [RFC1766] or [RFC3066]. Each record MAY also contain the following fields: o Deprecated * Deprecated's field-body contains the date the record was deprecated. In some cases this value is before that of the associated 'Added' field in the registry. o Preferred-Value * Preferred-Value's field body contains a canonical mapping from this record's value to a modern equivalent that is preferred in its place. Depending on the value of the 'Type' field, this value can take different forms: + For fields of type 'language', 'Preferred-Value' contains the primary language subtag that is preferred when forming the language tag. + For fields of type 'script', 'region', or 'variant', 'Preferred-Value' contains the subtag of the same type that is preferred for forming the language tag. + For fields of type 'extlang', 'grandfathered', or 'redundant', 'Preferred-Value' contains an "extended language range" ([RFC4647]) that is preferred for forming the language tag. That is, each of the subtags that appears in the value MUST appear in the replacement tag; additional fields can be included in a language tag as described elsewhere in this document. For example, the replacement for the grandfathered tag "zh-min-nan" (Min Nan Chinese) is "nan", which can be used as the basis for tags such as "nan- Hant" or "nan-TW" (note that the extended language subtag form such as "zh-nan-Hant" or "zh-nan-TW" can also be used). o Prefix * Prefix's field-body contains a "entended language range" (basically, a collection of subtags, see [RFC4647]) which SHOULD be used with this subtag when forming language tag. The Prefix's subtags appear before the subtag. This field MUST Phillips & Davis Expires March 21, 2009 [Page 25] Internet-Draft language-tags September 2008 appear only in records whose 'Type' field-body is either 'extlang' or 'variant'. For example, the variant 'nedis' (Nadiza dialect) has a 'Prefix' of "sl" (Slovenian), meaning that tags such as "sl- nedis" and "sl-IT-nedis" are appropriate, while the tag "is- nedis" (Icelandic, Nadiza dialect) is not. o Suppress-Script * Suppress-Script's field-body contains a script subtag that SHOULD NOT be used to form language tags with the associated primary or extended language subtag. This field MUST appear only in records whose 'Type' field-body is "language" or "extlang". See Section 4.1. o Macrolanguage * Macrolanguage's field-body contains a primary language subtag defined by ISO 639 as the "macrolanguage" that encompasses this language subtag. This field MUST appear only in records whose 'Type' field-body is either "language". o Scope * Scope's field-body contains information about a primary or extended language subtag indicating the type of language code according to ISO 639. The values permitted in this field are "macrolanguage", "collection", "special" and "private-use". This field only appears in records whose 'Type' field-body is either "language" or "extlang". When this field is omitted, the language is an individual language. o Comments * Comments's field-body contains additional information about the subtag, as deemed appropriate for understanding the registry and implementing language tags using the subtag or tag. 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. 3.1.3. Type Field 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); "extlang" (Section 2.2.2); "script" (Section 2.2.3); Phillips & Davis Expires March 21, 2009 [Page 26] Internet-Draft language-tags September 2008 "region" (Section 2.2.4); "variant" (Section 2.2.5); "grandfathered" or "redundant" (Section 2.2.8). 3.1.4. Subtag and Tag Fields 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]. The 'Subtag' field-body MUST follow the casing conventions described in Section 2.1.1. 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. 3.1.5. Description Field 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 (Section 3.4), via subsequent registration. The 'Description' does not replace the content of the Phillips & Davis Expires March 21, 2009 [Page 27] Internet-Draft language-tags September 2008 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 Phillips & Davis Expires March 21, 2009 [Page 28] Internet-Draft language-tags September 2008 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. 3.1.6. Deprecated Field 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 or via the registration process described in Section 3.5. Usually, the addition of a 'Deprecated' field is due to the action of one of the standards bodies, such as ISO 3166, withdrawing a code. 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]. Note that these records have a 'Deprecated' field with an earlier date then the corresponding 'Added' field! 3.1.7. Preferred-Value Field 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). 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: 1. ISO 639 language codes that were later withdrawn in favor of other codes. These values are mostly a historical curiosity. The 'he'/'iw' pairing above is an example of this. 2. Subtags (with types other than language or extlang) taken from codes or values that have been withdrawn in favor of a new code. In particular, this applies to region subtags taken from ISO 3166-1, because sometimes a country will change its name or Phillips & Davis Expires March 21, 2009 [Page 29] Internet-Draft language-tags September 2008 administration in such a way that warrants a new region code. In some cases, countries have reverted to an older name, which might already be encoded. For example, the subtag 'ZR' (Zaire) was replaced by the subtag 'CD' (Democratic Republic of the Congo) when that country's name was changed. 3. Tags or subtags that have become obsolete because the values they represent were later encoded. Many of the grandfathered or redundant tags were later encoded by ISO 639, for example, and fall into this grouping. For example, "i-klingon" was deprecated when the subtag 'tlh' was added. The record for "i-klingon" has a 'Preferred-Value' of 'tlh'. 4. Extended language subtags always have a mapping to their identical primary language subtag. For example, the extended language subtag 'yue' (Cantonese) can be used to form the tag "zh-yue". It has a Preferred-Value mapping to the primary language subtag 'yue', meaning that a tag such as "zh-yue-Hant-HK" can be canonicalized to "yue-Hant-HK". 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. Addition, modification, or Phillips & Davis Expires March 21, 2009 [Page 30] Internet-Draft language-tags September 2008 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]) 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] 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, 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'. 3.1.8. Prefix Field The 'Prefix' field contains an "extended language range" (see: [RFC4647]) 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. Phillips & Davis Expires March 21, 2009 [Page 31] Internet-Draft language-tags September 2008 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. 3.1.9. Suppress-Script Field 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. Phillips & Davis Expires March 21, 2009 [Page 32] Internet-Draft language-tags September 2008 3.1.10. Macrolanguage Field 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. 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. 3.1.11. Scope Field 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: Phillips & Davis Expires March 21, 2009 [Page 33] Internet-Draft language-tags September 2008 o 'macrolanguage' - Indicates a macrolanguage as defined by ISO 639-3 (see above (Section 3.1.10)). A macrolanguage is a cluster of closely-related languages that are sometimes considered to be a single language. o 'collection' - Indicates a subtag that represents a collection of languages, typically related by some type of historical, geographical, or linguistic association. Unlike a macrolanguage, a collection can contain languages that are only loosely related and a collection cannot be used interchangeably with languages that belong to it. o 'special' - Indicates a special language code. These are subtags used for identifying linguistic attributes not particularly associated with a concrete language. These include codes for when the language is undetermined or for non-linguistic content. o 'private-use' - Indicates a code reserved for private use in the underlying standard. Subtags with this scope can be used to indicate a primary language for which no ISO 639 or registered assignment exists. 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'. 3.1.12. Comments Field 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 Phillips & Davis Expires March 21, 2009 [Page 34] Internet-Draft language-tags September 2008 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. 3.2. Language Subtag Reviewer The Language Subtag Reviewer moderates the ietf-languages mailing list, responds to requests for registration, and performs the other registry maintenance duties described in Section 3.3. Only the Language Subtag Reviewer is permitted to request IANA to change, update, or add records to the Language Subtag 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]). The IESG can reverse or overturn the decisions of the Language Subtag Reviewer, provide guidance, or take other appropriate actions. 3.3. Maintenance of the Registry Maintenance of the registry requires that, as codes are assigned or withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language Subtag Reviewer MUST evaluate each change 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. 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. Phillips & Davis Expires March 21, 2009 [Page 35] Internet-Draft language-tags September 2008 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) 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. 3.4. Stability of IANA Registry Entries The stability of entries and their meaning in the registry is critical to the long-term stability of language tags. The rules in this section guarantee that a specific language tag's meaning is stable over time and will not change. These rules specifically deal with how changes to codes (including withdrawal and deprecation of codes) maintained by ISO 639, ISO 15924, ISO 3166, and UN M.49 are reflected in the IANA Language Subtag Registry. Assignments to the IANA Language Subtag Registry MUST follow the following stability rules: 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST NOT be changed and are guaranteed to be stable over time. 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be added, altered, or removed via the registration process. These changes SHOULD be limited to changes necessary to mirror changes in one of the underlying standards (ISO 639, ISO 15924, ISO 3166-1, or UN M.49) and typically alteration or removal of a Preferred-Value is limited specifically to region codes. 3. Values in the 'Description' field MUST NOT be changed in a way that would invalidate any existing tags. The description MAY be broadened somewhat in scope, changed to add information, or adapted to the most common modern usage. For example, countries occasionally change their names; a historical example of this would be "Upper Volta" changing to "Burkina Faso". 4. Values in the field 'Prefix' MAY be added to existing records of type 'variant' via the registration process, provided the 'variant' already has at least one 'Prefix'. A 'Prefix' field SHALL NOT be registered for any 'variant' that has no existing 'Prefix' field. If a prefix is added to a variant record, Phillips & Davis Expires March 21, 2009 [Page 36] Internet-Draft language-tags September 2008 'Comment' fields MAY be used to explain different usages with the various prefixes. 5. Values in the field 'Prefix' in records of type 'variant' MAY also be modified, so long as the modifications broaden the set of prefixes. That is, a prefix MAY be replaced by one of its own prefixes. For example, the prefix "en-US" could be replaced by "en", but not by the prefixes "en-Latn", "fr", or "en-US- boont". If one of those prefix values were needed, it would have to be separately registered. 6. Values in the field 'Prefix' in records of type 'extlang' MUST NOT be added, modified, or removed. 7. The field 'Prefix' MUST NOT be removed from any record in which it appears. This field SHOULD be included in the initial registration of any records of type 'variant' and MUST be included in any records of type 'extlang'. 8. The field 'Comments' MAY be added, changed, modified, or removed via the registration process or any of the processes or considerations described in this section. 9. The field 'Suppress-Script' MAY be added or removed via the registration process. 10. The field 'Macrolanguage' MAY be added or removed via the registration process, but only in response to changes made by ISO 639. The Macrolanguage field appears whenever a language has a corresponding Macrolanguage in ISO 639. That is, the Macrolanguage fields in the registry exactly match those of ISO 639. No other macrolanguage mappings will be considered for registration. 11. The field 'Scope' MAY be added or removed from a primary or extended language subtag after initial registration, and it MAY be modified in order to match any changes made by ISO 639. Changes to the 'Scope' field MUST mirror changes made by ISO 639. Note that primary or extended language subtags whose records do not contain a 'Scope' field (that is, most of them) are individual languages as described in Section 3.1.11. 12. Primary and extended language subtags (other than independently registered values created using the registration process) are created according to the assignments of the various parts of ISO 639, as follows: Phillips & Davis Expires March 21, 2009 [Page 37] Internet-Draft language-tags September 2008 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: 1. 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'. 2. '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. 3. Sign languages SHOULD have an 'extlang' record with a 'Prefix' of 'sgn'. 4. '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. 5. Extended language subtag records MUST include the fields 'Prefix' and 'Preferred-Value' with field-values Phillips & Davis Expires March 21, 2009 [Page 38] Internet-Draft language-tags September 2008 assigned as described in Section 2.2.2. 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. 13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict with existing subtags of the associated type and whose meaning is not the same as an existing subtag of the same type are entered into the IANA registry as new records. 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are withdrawn by their respective maintenance or registration authority remain valid in language tags. A 'Deprecated' field containing the date of withdrawal MUST be added to the record. If a new record of the same type is added that represents a replacement value, then a 'Preferred-Value' field MAY also be added. The registration process MAY be used to add comments about the withdrawal of the code by the respective standard. 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'). 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that conflict with existing subtags of the associated type, including subtags that are deprecated, MUST NOT be entered into the registry. The following additional considerations apply to subtag values that are reassigned: A. For ISO 639 codes, if the newly assigned code's meaning is not represented by a subtag in the IANA registry, the Language Subtag Reviewer, as described in Section 3.5, SHALL prepare a proposal for entering in the IANA registry as soon as practical a registered language subtag as an alternate value for the new code. The form of the registered language subtag will be at the discretion of the Language Subtag Reviewer and MUST conform to other restrictions on language subtags in this document. Phillips & Davis Expires March 21, 2009 [Page 39] Internet-Draft language-tags September 2008 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, 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, 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. Phillips & Davis Expires March 21, 2009 [Page 40] Internet-Draft language-tags September 2008 16. UN M.49 has codes for both countries and areas (such as '276' for Germany) and geographical regions and sub-regions (such as '150' for Europe). UN M.49 country or area codes for which there is no corresponding ISO 3166-1 code SHOULD NOT be registered, except as a surrogate for an ISO 3166-1 code that is blocked from registration by an existing subtag. If such a code becomes necessary, then the registration authority for ISO 3166-1 SHOULD first be petitioned to assign a code to the region. If the petition for a code assignment by ISO 3166-1 is refused or not acted on in a timely manner, the registration process described in Section 3.5 MAY then be used to register the corresponding UN M.49 code. This way, UN M.49 codes remain available as the value of last resort in cases where ISO 3166-1 reassigns a deprecated value in the registry. 17. The redundant and grandfathered entries together form the complete list of tags registered under [RFC3066]. The redundant tags are those previously registered tags that can now be formed using the subtags defined in the registry. The grandfathered entries include those that can never be legal because they are 'irregular' (that is, they do not match the 'langtag' production in Figure 1), are limited by rule (subtags such as 'nyn' and 'min' look like the extlang production, but cannot be registered as extended language subtags), or their subtags are inappropriate for registration. All of the grandfathered tags are listed in either the 'regular' or the 'irregular' productions in the ABNF. Under [RFC4646] it was possible for grandfathered tags to become redundant. However, all of the tags for which this was possible became redundant before this document was produced. So the set of redundant and grandfathered tags is now permanent and immutable: new entries of either type MUST NOT be added and existing entries MUST NOT be removed. The decision-making process about which tags were initially grandfathered and which were made redundant is described in [RFC4645]. Many of the grandfathered tags are deprecated, indeed, they were deprecated even before [RFC4646]. For example, the tag "art- lojban" was deprecated in favor of the primary language subtag 'jbo'. These tags could have been made 'redundant' by registering some of their subtags as 'variants'. The 'variant- like' subtags in the grandfathered registrations SHALL NOT be registered in the future, even with a similar or identical meaning. Phillips & Davis Expires March 21, 2009 [Page 41] Internet-Draft language-tags September 2008 3.5. Registration Procedure for Subtags The procedure given here MUST be used by anyone who wants to use a subtag not currently in the IANA Language Subtag Registry or who wishes to add, modify, update, or remove information in existing records as permitted by this document. 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. Stability provisions are described in Section 3.4. Registration requests are accepted relating to information in the 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value', or 'Suppress-Script' fields in a subtag's record as described in Section 3.4. Changes to all other fields in the IANA registry are NOT permitted. Registering a new subtag or requesting modifications to an existing tag or subtag starts with the requester filling out the registration form reproduced below. Note that each response is not limited in size so that the request can adequately describe the registration. The fields in the "Record Requested" section SHOULD follow the requirements in Section 3.1. 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 Phillips & Davis Expires March 21, 2009 [Page 42] Internet-Draft language-tags September 2008 Examples of completed registration forms can be found in Appendix C. A complete list of approved registration forms is online at http://www.iana.org/assignments/lang-subtags-templates/. The subtag registration form MUST be sent to . Registration requests receive a two-week review period before being approved and submitted to IANA for inclusion in the registry. 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 or to make the 'Description' fields unique for the given record type) the modified form MUST also be sent to 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 . The list can be hosted by IANA or by any third party at the request of IESG. Before forwarding any registration to IANA, the Language Subtag Reviewer MUST ensure that all requirements in this document are met. This includes ensuring that values in the 'Subtag' field match case according to the description in Section 3.1.4 and that 'Description' fields are unique for the given record type as described in Section 3.1.5. 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). 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 encompassed by another language. All records of type 'extlang' MUST, therefore, contain a 'Prefix' field at the time of registration. This Prefix field can never be altered or removed and requests to do so MUST be rejected. Variant subtags are usually registered for use with a particular range of language tags and variant subtags based on the terminology of the language to which they are apply are encouraged. For example, the subtag 'rozaj' (Resian) is intended for use with language tags Phillips & Davis Expires March 21, 2009 [Page 43] Internet-Draft language-tags September 2008 that start with the primary language subtag "sl" (Slovenian), 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 'Prefix' fields 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. Requests to add a 'Prefix' to a variant subtag that has no current 'Prefix' field MUST be rejected. Variants are registered with no prefix because they are potentially useful with many or even all languages. Adding one or more 'Prefix' fields would be potentially harmful to the use of the variant, since it dramatically reduces the scope of the subtag (which is not allowed under the stability rules (Section 3.4), as opposed to broadening the scope of the subtag, which is what the addition of a 'Prefix' normally does. An example of such a "no-prefix" variant is the subtag 'fonipa', which represents the International Phonetic Alphabet, a scheme which can be used to transcribe many languages. The 'Description' fields provided in the request MUST contain at least one description written or transcribed into the Latin script; the request MAY also include additional 'Description' fields in any script or language. The 'Description' field is used for identification purposes and doesn't necessarily represent the actual native name of the language or variation. It also doesn't have to be in any particular language, but SHOULD be both suitable and sufficient to identify the item in the record. The Language Subtag Reviewer will check and edit any proposed 'Description' fields so as to ensure uniqueness and prevent collisions with 'Description' fields in other records of the same type. If this occurs in an independent registration request, the Language Subtag Reviewer MUST resubmit the record to ietf-languages, treating it as a modification of a request due to discussion, as described in Section 3.5, unless the request's Phillips & Davis Expires March 21, 2009 [Page 44] Internet-Draft language-tags September 2008 sole purpose is to introduce a duplicate 'Description' field, in which case the request SHALL be rejected. 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. Soon after the two-week review period has passed, the Language Subtag Reviewer MUST take one of the following actions: o Explicitly accept the request and forward the form containing the record to be inserted or modified to iana@iana.org according to the procedure described in Section 3.3. o Explicitly reject the request because of significant objections raised on the list or due to problems with constraints in this document (which MUST be explicitly cited). o Extend the review period by granting an additional two-week increment to permit further discussion. After each two-week increment, the Language Subtag Reviewer MUST indicate on the list whether the registration has been accepted, rejected, or extended. Note that the Language Subtag Reviewer MAY raise objections on the list if he or she so desires. The important thing is that the objection MUST be made publicly. Sometimes the request needs to be modified as a result of discussion during the review period or due to requirements in this document. The applicant, Language Subtag Reviewer, or others MAY submit a modified version of the completed registration form, which will be considered in lieu of the original request with the explicit approval of the applicant. Such changes do not restart the two-week discussion period, although an application containing the final record submitted to IANA MUST appear on the list at least one week prior to the Language Subtag Reviewer forwarding the record to IANA. The applicant MAY modify a rejected application with more appropriate or additional information and submit it again; this starts a new two- week comment period. Registrations initiated due to the provisions of Section 3.3 or Section 3.4 SHALL NOT be rejected altogether (since they have to ultimately appear in the registry) and SHOULD be completed as quickly as possible. The review process allows list members to comment on the specific information in the form and the record it contains and Phillips & Davis Expires March 21, 2009 [Page 45] Internet-Draft language-tags September 2008 thus help ensure that it is correct and consistent. The Language Subtag Reviewer MAY reject a specific version of the form, but MUST propose a suitable replacement, extending the review period as described above, until the form is in a format worthy of reviewer's approval and meets with rough consensus of the list. Decisions made by the Language Subtag Reviewer MAY be appealed to the IESG [RFC2028] under the same rules as other IETF decisions [RFC2026]. This includes a decision to extend the review period or the failure to announce a decision in a clear and timely manner. The approved records appear in the Language Subtag Registry. The approved registration forms are available online under http://www.iana.org/assignments/lang-subtags-templates/. Updates or changes to existing records follow the same procedure as new registrations. The Language Subtag Reviewer decides whether there is consensus to update the registration following the two week review period; normally, objections by the original registrant will carry extra weight in forming such a consensus. Registrations are permanent and stable. Once registered, subtags will not be removed from the registry and will remain a valid way in which to specify a specific language or variant. Note: The purpose of the "Reference to published description" section in the registration form is to aid in verifying whether a language is registered or what language or language variation a particular subtag refers to. In most cases, reference to an authoritative grammar or dictionary of that language will be useful; in cases where no such work exists, other well-known works describing that language or in that language MAY be appropriate. The Language Subtag Reviewer decides what constitutes "good enough" reference material. This requirement is not intended to exclude particular languages or dialects due to the size of the speaker population or lack of a standardized orthography. Minority languages will be considered equally on their own merits. 3.6. Possibilities for Registration Possibilities for registration of subtags or information about subtags include: o Primary language subtags for languages not listed in ISO 639 that are not variants of any listed or registered language MAY be registered. At the time this document was created, there were no examples of this form of subtag. Before attempting to register a language subtag, there MUST be an attempt to register the language Phillips & Davis Expires March 21, 2009 [Page 46] Internet-Draft language-tags September 2008 with ISO 639. Subtags MUST NOT be registered for languages defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, or that are under consideration by the ISO 639 registration authorities, or that have never been attempted for registration with those authorities. If ISO 639 has previously rejected a language for registration, it is reasonable to assume that there must be additional, very compelling evidence of need before it will be registered as a primary language subtag in the IANA registry (to the extent that it is very unlikely that any subtags will be registered of this type). o Dialect or other divisions or variations within a language, its orthography, writing system, regional or historical usage, transliteration or other transformation, or distinguishing variation MAY be registered as variant subtags. An example is the 'rozaj' subtag (the Resian dialect of Slovenian). o The addition or maintenance of fields (generally of an informational nature) in Tag or Subtag records as described in Section 3.1 and subject to the stability provisions in Section 3.4. This includes Description, Comments, Deprecated and Preferred-Value fields for obsolete or withdrawn codes, or the addition of Suppress-Script or Macrolanguage fields to primary language subtags, as well as other changes permitted by this document, such as the addition of an appropriate Prefix field to a variant subtag. o The addition of records and related field value changes necessary to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and UN M.49 as described in Section 3.4. Subtags proposed for registration that would cause all or part of a grandfathered tag to become redundant but whose meaning conflicts with or alters the meaning of the grandfathered tag MUST be rejected. This document leaves the decision on what subtags or changes to subtags are appropriate (or not) to the registration process described in Section 3.5. Note: four-character primary language subtags are reserved to allow for the possibility of alpha4 codes in some future addition to the ISO 639 family of standards. ISO 639 defines a registration authority for additions to and changes in the list of languages in ISO 639. This agency is: International Information Centre for Terminology (Infoterm) Aichholzgasse 6/12, AT-1120 Phillips & Davis Expires March 21, 2009 [Page 47] Internet-Draft language-tags September 2008 Wien, Austria Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 ISO 639-2 defines a registration authority for additions to and changes in the list of languages in ISO 639-2. This agency is: Library of Congress Network Development and MARC Standards Office Washington, D.C. 20540 USA Phone: +1 202 707 6237 Fax: +1 202 707 0115 URL: http://www.loc.gov/standards/iso639-2 ISO 639-3 defines a registration authority for additions to and changes in the list of languages in ISO 639-3. This agency is: SIL International ISO 639-3 Registrar 7500 W. Camp Wisdom Rd. Dallas, TX 75236 USA Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 Email: iso639-3@sil.org URL: http://www.sil.org/iso639-3 ISO 639-5 defines a registration authority for additions to and changes in the list of languages in ISO 639-5. This agency is the same as for ISO 639-2 and is: Library of Congress Network Development and MARC Standards Office Washington, D.C. 20540 USA Phone: +1 202 707 6237 Fax: +1 202 707 0115 URL: http://www.loc.gov/standards/iso639-5 The maintenance agency for ISO 3166-1 (country codes) is: ISO 3166 Maintenance Agency c/o International Organization for Standardization Case postale 56 CH-1211 Geneva 20 Switzerland Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html The registration authority for ISO 15924 (script codes) is: Unicode Consortium Box 391476 Mountain View, CA 94039-1476, USA URL: http://www.unicode.org/iso15924 Phillips & Davis Expires March 21, 2009 [Page 48] Internet-Draft language-tags September 2008 The Statistics Division of the United Nations Secretariat maintains the Standard Country or Area Codes for Statistical Use and can be reached at: Statistical Services Branch Statistics Division United Nations, Room DC2-1620 New York, NY 10017, USA Fax: +1-212-963-0623 E-mail: statistics@un.org URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 3.7. Extensions and the Extensions Registry Extension subtags are those introduced by single-character subtags ("singletons") other than 'x'. They are reserved for the generation of identifiers that contain a language component and are compatible with applications that understand language tags. The structure and form of extensions are defined by this document so that implementations can be created that are forward compatible with applications that might be created using singletons in the future. In addition, defining a mechanism for maintaining singletons will lend stability to this document by reducing the likely need for future revisions or updates. Single-character subtags are assigned by IANA using the "IETF Consensus" policy defined by [RFC2434]. This policy requires the development of an RFC, which SHALL define the name, purpose, processes, and procedures for maintaining the subtags. The maintaining or registering authority, including name, contact email, discussion list email, and URL location of the registry, MUST be indicated clearly in the RFC. The RFC MUST specify or include each of the following: o The specification MUST reference the specific version or revision of this document that governs its creation and MUST reference this section of this document. o The specification and all subtags defined by the specification MUST follow the ABNF and other rules for the formation of tags and subtags as defined in this document. In particular, it MUST specify that case is not significant and that subtags MUST NOT exceed eight characters in length. o The specification MUST specify a canonical representation. Phillips & Davis Expires March 21, 2009 [Page 49] Internet-Draft language-tags September 2008 o The specification of valid subtags MUST be available over the Internet and at no cost. o The specification MUST be in the public domain or available via a royalty-free license acceptable to the IETF and specified in the RFC. o The specification MUST be versioned, and each version of the specification MUST be numbered, dated, and stable. o The specification MUST be stable. That is, extension subtags, once defined by a specification, MUST NOT be retracted or change in meaning in any substantial way. o The specification MUST include in a separate section the registration form reproduced in this section (below) to be used in registering the extension upon publication as an RFC. o IANA MUST be informed of changes to the contact information and URL for the specification. IANA will maintain a registry of allocated single-character (singleton) subtags. This registry MUST use the record-jar format described by the ABNF in Section 3.1. Upon publication of an extension as an RFC, the maintaining authority defined in the RFC MUST forward this registration form to iesg@ietf.org, who MUST forward the request to iana@iana.org. The maintaining authority of the extension MUST maintain the accuracy of the record by sending an updated full copy of the record to iana@iana.org with the subject line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in these updates. Failure to maintain this record, maintain the corresponding registry, or meet other conditions imposed by this section of this document MAY be appealed to the IESG [RFC2028] under the same rules as other IETF decisions (see [RFC2026]) and MAY result in the authority to maintain the extension being withdrawn or reassigned by the IESG. Phillips & Davis Expires March 21, 2009 [Page 50] Internet-Draft language-tags September 2008 %% Identifier: Description: Comments: Added: RFC: Authority: Contact_Email: Mailing_List: URL: %% Figure 6: Format of Records in the Language Tag Extensions Registry 'Identifier' contains the single-character subtag (singleton) assigned to the extension. The Internet-Draft submitted to define the extension SHOULD specify which letter or digit to use, although the IESG MAY change the assignment when approving the RFC. 'Description' contains the name and description of the extension. 'Comments' is an OPTIONAL field and MAY contain a broader description of the extension. 'Added' contains the date the extension's RFC was published in the "full-date" format specified in [RFC3339]. For example: 2004-06-28 represents June 28, 2004, in the Gregorian calendar. 'RFC' contains the RFC number assigned to the extension. 'Authority' contains the name of the maintaining authority for the extension. 'Contact_Email' contains the email address used to contact the maintaining authority. 'Mailing_List' contains the URL or subscription email address of the mailing list used by the maintaining authority. 'URL' contains the URL of the registry for this extension. The determination of whether an Internet-Draft meets the above conditions and the decision to grant or withhold such authority rests solely with the IESG and is subject to the normal review and appeals process associated with the RFC process. Extension authors are strongly cautioned that many (including most well-formed) processors will be unaware of any special relationships Phillips & Davis Expires March 21, 2009 [Page 51] Internet-Draft language-tags September 2008 or meaning inherent in the order of extension subtags. Extension authors SHOULD avoid subtag relationships or canonicalization mechanisms that interfere with matching or with length restrictions that sometimes exist in common protocols where the extension is used. In particular, applications MAY truncate the subtags in doing matching or in fitting into limited lengths, so it is RECOMMENDED that the most significant information be in the most significant (left-most) subtags and that the specification gracefully handle truncated subtags. When a language tag is to be used in a specific, known, protocol, it is RECOMMENDED that the language tag not contain extensions not supported by that protocol. In addition, note that some protocols MAY impose upper limits on the length of the strings used to store or transport the language tag. 3.8. Update of the Language Subtag Registry Upon adoption of this document the IANA Language Subtag Registry will need an update so that it contains the complete set of subtags valid in a language tag. This collection of subtags, along with a description of the process used to create it, is described by [registry-update]. IANA will publish the updated version of the registry described by this document using the instructions and content of [registry-update]. Once published by IANA, the maintenance procedures, rules, and registration processes described in this document will be available for new registrations or updates. Registrations that are in process under the rules defined in [RFC4646] when this document is adopted MUST be completed under the rules contained in this document. Phillips & Davis Expires March 21, 2009 [Page 52] Internet-Draft language-tags September 2008 4. Formation and Processing of Language Tags This section addresses how to use the information in the registry with the tag syntax to choose, form, and process language tags. 4.1. Choice of Language Tag The guiding principle in forming language tags is to "tag content wisely." Sometimes there is a choice between several possible tags for the same content. The choice of which tag to use depends on the content and application in question and some amount of judgment might be necessary when selecting a tag. Interoperability is best served when the same language tag is used consistently to represent the same language. If an application has requirements that make the rules here inapplicable, then that application risks damaging interoperability. It is strongly RECOMMENDED that users not define their own rules for language tag choice. Standards, protocols, and applications that reference this document normatively but apply different rules to the ones given in this section MUST specify how language tag selection varies from the guidelines given here. To ensu