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Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document obsoletes RFC4646, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (October 31, 2008) is 5655 days in the past. Is this intentional? Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO15924' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO3166-1' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-1' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-2' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-3' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-5' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO646' ** Obsolete normative reference: RFC 2028 (Obsoleted by RFC 9281) ** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226) ** Downref: Normative reference to an Informational RFC: RFC 2860 ** Downref: Normative reference to an Informational RFC: RFC 4645 -- Possible downref: Non-RFC (?) normative reference: ref. 'UAX14' -- Obsolete informational reference (is this intentional?): RFC 1766 (Obsoleted by RFC 3066, RFC 3282) -- Obsolete informational reference (is this intentional?): RFC 3066 (Obsoleted by RFC 4646, RFC 4647) -- Obsolete informational reference (is this intentional?): RFC 4646 (Obsoleted by RFC 5646) Summary: 5 errors (**), 0 flaws (~~), 2 warnings (==), 19 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Phillips, Ed. 3 Internet-Draft Lab126 4 Obsoletes: 4646 (if approved) M. Davis, Ed. 5 Intended status: BCP Google 6 Expires: May 4, 2009 October 31, 2008 8 Tags for Identifying Languages 9 draft-ietf-ltru-4646bis-18 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on May 4, 2009. 36 Abstract 38 This document describes the structure, content, construction, and 39 semantics of language tags for use in cases where it is desirable to 40 indicate the language used in an information object. It also 41 describes how to register values for use in language tags and the 42 creation of user-defined extensions for private interchange. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 47 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 5 48 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 5 49 2.1.1. Formatting of Language Tags . . . . . . . . . . . . . 7 50 2.2. Language Subtag Sources and Interpretation . . . . . . . . 8 51 2.2.1. Primary Language Subtag . . . . . . . . . . . . . . . 10 52 2.2.2. Extended Language Subtags . . . . . . . . . . . . . . 12 53 2.2.3. Script Subtag . . . . . . . . . . . . . . . . . . . . 13 54 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 14 55 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 16 56 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 17 57 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 18 58 2.2.8. Grandfathered and Redundant Registrations . . . . . . 19 59 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 20 60 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 22 61 3.1. Format of the IANA Language Subtag Registry . . . . . . . 22 62 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 22 63 3.1.2. Record and Field Definitions . . . . . . . . . . . . . 23 64 3.1.3. Type Field . . . . . . . . . . . . . . . . . . . . . . 27 65 3.1.4. Subtag and Tag Fields . . . . . . . . . . . . . . . . 27 66 3.1.5. Description Field . . . . . . . . . . . . . . . . . . 27 67 3.1.6. Deprecated Field . . . . . . . . . . . . . . . . . . . 29 68 3.1.7. Preferred-Value Field . . . . . . . . . . . . . . . . 29 69 3.1.8. Prefix Field . . . . . . . . . . . . . . . . . . . . . 31 70 3.1.9. Suppress-Script Field . . . . . . . . . . . . . . . . 32 71 3.1.10. Macrolanguage Field . . . . . . . . . . . . . . . . . 33 72 3.1.11. Scope Field . . . . . . . . . . . . . . . . . . . . . 33 73 3.1.12. Comments Field . . . . . . . . . . . . . . . . . . . . 34 74 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 35 75 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 35 76 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 36 77 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 42 78 3.6. Possibilities for Registration . . . . . . . . . . . . . . 47 79 3.7. Extensions and the Extensions Registry . . . . . . . . . . 49 80 3.8. Update of the Language Subtag Registry . . . . . . . . . . 52 81 4. Formation and Processing of Language Tags . . . . . . . . . . 53 82 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 53 83 4.1.1. Tagging Encompassed Languages . . . . . . . . . . . . 57 84 4.1.2. Using Extended Language Subtags . . . . . . . . . . . 58 85 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 60 86 4.3. Lists of Languages . . . . . . . . . . . . . . . . . . . . 62 87 4.4. Length Considerations . . . . . . . . . . . . . . . . . . 63 88 4.4.1. Working with Limited Buffer Sizes . . . . . . . . . . 63 89 4.4.2. Truncation of Language Tags . . . . . . . . . . . . . 64 90 4.5. Canonicalization of Language Tags . . . . . . . . . . . . 65 91 4.6. Considerations for Private Use Subtags . . . . . . . . . . 67 92 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 69 93 5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 69 94 5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 70 95 6. Security Considerations . . . . . . . . . . . . . . . . . . . 72 96 7. Character Set Considerations . . . . . . . . . . . . . . . . . 73 97 8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 74 98 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 78 99 9.1. Normative References . . . . . . . . . . . . . . . . . . . 78 100 9.2. Informative References . . . . . . . . . . . . . . . . . . 79 101 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 81 102 Appendix B. Examples of Language Tags (Informative) . . . . . . . 82 103 Appendix C. Examples of Registration Forms . . . . . . . . . . . 85 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 87 105 Intellectual Property and Copyright Statements . . . . . . . . . . 88 107 1. Introduction 109 Human beings on our planet have, past and present, used a number of 110 languages. There are many reasons why one would want to identify the 111 language used when presenting or requesting information. 113 The language of an information item or a user's language preferences 114 often need to be identified so that appropriate processing can be 115 applied. For example, the user's language preferences in a Web 116 browser can be used to select Web pages appropriately. Language 117 information can also be used to select among tools (such as 118 dictionaries) to assist in the processing or understanding of content 119 in different languages. Knowledge about the particular language used 120 by some piece of information content might be useful or even required 121 by some types of processing; for example, spell-checking, computer- 122 synthesized speech, Braille transcription, or high-quality print 123 renderings. 125 One means of indicating the language used is by labeling the 126 information content with an identifier or "tag". These tags can also 127 be used to specify the user's preferences when selecting information 128 content, or for labeling additional attributes of content and 129 associated resources. 131 Sometimes language tags are used to indicate additional language 132 attributes of content. For example, indicating specific information 133 about the dialect, writing system, or orthography used in a document 134 or resource may enable the user to obtain information in a form that 135 they can understand, or it can be important in processing or 136 rendering the given content into an appropriate form or style. 138 This document specifies a particular identifier mechanism (the 139 language tag) and a registration function for values to be used to 140 form tags. It also defines a mechanism for private use values and 141 future extension. 143 This document replaces [RFC4646], which replaced [RFC3066] and its 144 predecessor [RFC1766]. For a list of changes in this document, see 145 Section 8. 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 149 document are to be interpreted as described in [RFC2119]. 151 2. The Language Tag 153 Language tags are used to help identify languages, whether spoken, 154 written, signed, or otherwise signaled, for the purpose of 155 communication. This includes constructed and artificial languages, 156 but excludes languages not intended primarily for human 157 communication, such as programming languages. 159 2.1. Syntax 161 A language tag is composed from a sequence of one or more "subtags", 162 each of which refines or narrows the range of language identified by 163 the overall tag. Subtags, in turn, are a sequence of alphanumeric 164 characters (letters and digits), distinguished and separated from 165 other subtags in a tag by a hyphen ("-", ABNF [RFC5234] %x2D). 167 There are different types of subtag, each of which is distinguished 168 by length, position in the tag, and content: each subtag's type can 169 be recognized solely by these features. This makes it possible to 170 extract and assign some semantic information to the subtags, even if 171 the specific subtag values are not recognized. Thus, a language tag 172 processor need not have a list of valid tags or subtags (that is, a 173 copy of some version of the IANA Language Subtag Registry) in order 174 to perform common searching and matching operations. The only 175 exceptions to this ability to infer meaning from subtag structure are 176 the grandfathered tags listed in the productions 'regular' and 177 'irregular' below. These tags were registered under [RFC3066] and 178 are a fixed list that can never change. 180 The syntax of the language tag in ABNF [RFC5234] is: 182 Language-Tag = langtag ; normal language tags 183 / privateuse ; private use tag 184 / grandfathered ; grandfathered tags 186 langtag = language 187 ["-" script] 188 ["-" region] 189 *("-" variant) 190 *("-" extension) 191 ["-" privateuse] 193 language = 2*3ALPHA ; shortest ISO 639 code 194 ["-" extlang] ; sometimes followed by 195 ; extended language subtags 196 / 4ALPHA ; or reserved for future use 197 / 5*8ALPHA ; or registered language subtag 199 extlang = 3ALPHA ; selected ISO 639 codes 200 *2("-" 3ALPHA) ; permanently reserved 202 script = 4ALPHA ; ISO 15924 code 204 region = 2ALPHA ; ISO 3166-1 code 205 / 3DIGIT ; UN M.49 code 207 variant = 5*8alphanum ; registered variants 208 / (DIGIT 3alphanum) 210 extension = singleton 1*("-" (2*8alphanum)) 212 ; Single alphanumerics 213 ; "x" reserved for private use 214 singleton = %x41-57 ; a - w 215 / %x59-5A ; y - z 216 / %x61-77 ; A - W 217 / %x79-7A ; Y - Z 218 / DIGIT ; 0 - 9 220 privateuse = "x" 1*("-" (1*8alphanum)) 222 grandfathered = irregular ; non-redundant tags registered 223 / regular ; during the RFC 3066 era 225 irregular = "en-GB-oed" ; irregular tags do not match 226 / "i-ami" ; the 'langtag' production and 227 / "i-bnn" ; would not otherwise be 228 / "i-default" ; considered 'well-formed' 229 / "i-enochian" ; These tags are all valid, 230 / "i-hak" ; but most are deprecated 231 / "i-klingon" ; in favor of more modern 232 / "i-lux" ; subtags or subtag 233 / "i-mingo" ; combination 234 / "i-navajo" 235 / "i-pwn" 236 / "i-tao" 237 / "i-tay" 238 / "i-tsu" 239 / "sgn-BE-FR" 240 / "sgn-BE-NL" 241 / "sgn-CH-DE" 243 regular = "art-lojban" ; these tags match the 'langtag' 244 / "cel-gaulish" ; production, but their subtags 245 / "no-bok" ; are not extended language 246 / "no-nyn" ; or variant subtags: their meaning 247 / "zh-guoyu" ; is defined by their registration 248 / "zh-hakka" ; and all of these are deprecated 249 / "zh-min" ; in favor of a more modern 250 / "zh-min-nan" ; subtag or sequence of subtags 251 / "zh-xiang" 253 alphanum = (ALPHA / DIGIT) ; letters and numbers 255 Figure 1: Language Tag ABNF 257 For examples of language tags, see Appendix B. 259 All subtags have a maximum length of eight characters and whitespace 260 is not permitted in a language tag. There is a subtlety in the ABNF 261 production 'variant': a variant starting with a digit has a minimum 262 length of four characters, while those starting with a letter have a 263 minimum length of five characters. 265 Although [RFC5234] refers to octets, the language tags described in 266 this document are sequences of characters from the US-ASCII [ISO646] 267 repertoire. Language tags MAY be used in documents and applications 268 that use other encodings, so long as these encompass the relevant 269 part of the US-ASCII repertoire. An example of this would be an XML 270 document that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 272 2.1.1. Formatting of Language Tags 274 At all times, language tags and their subtags, including private-use 275 and extensions, are to be treated as case insensitive: there exist 276 conventions for the capitalization of some of the subtags, but these 277 MUST NOT be taken to carry meaning. 279 Thus, the tag "mn-Cyrl-MN" is not distinct from "MN-cYRL-mn" or "mN- 280 cYrL-Mn" (or any other combination), and each of these variations 281 conveys the same meaning: Mongolian written in the Cyrillic script as 282 used in Mongolia. 284 The ABNF syntax also does not distinguish between upper and 285 lowercase: the uppercase US-ASCII letters in the range 'A' through 286 'Z' are always considered equivalent and mapped directly to their US- 287 ASCII lowercase equivalents in the range 'a' through 'z'. So the tag 288 "I-AMI" is considered equivalent to that value "i-ami" in the 289 'irregular' production. 291 Although case distinctions do not carry meaning in language tags, 292 consistent formatting and presentation of language tags will aid 293 users. The format of subtags in the registry is RECOMMENDED as the 294 form to use in language tags. This format generally corresponds to 295 the common conventions for the various ISO standards from which the 296 subtags are derived. 298 These conventions include: 300 o [ISO639-1] recommends that language codes be written in lowercase 301 ('mn' Mongolian). 303 o [ISO15924] recommends that script codes use lowercase with the 304 initial letter capitalized ('Cyrl' Cyrillic). 306 o [ISO3166-1] recommends that country codes be capitalized ('MN' 307 Mongolia). 309 An implementation can reproduce this format without accessing the 310 registry as follows: All subtags, including extension and private use 311 subtags, use lowercase letters, with two exceptions: two-letter and 312 four-letter subtags that neither appear at the start of the tag nor 313 occur after singletons. Such two-letter subtags are all uppercase 314 (as in the tags "en-CA-x-ca" or "sgn-BE-FR") and four-letter subtags 315 are titlecase (as in the tag "az-Latn-x-latn"). 317 Note: Case folding of ASCII letters in certain locales, unless 318 carefully handled, sometimes produces non-ASCII character values. 319 The Unicode Character Database file "SpecialCasing.txt" defines the 320 specific cases that are known to cause problems with this. In 321 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 322 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 323 Implementers SHOULD specify a locale-neutral casing operation to 324 ensure that case folding of subtags does not produce this value, 325 which is illegal in language tags. For example, if one were to 326 uppercase the region subtag 'in' using Turkish locale rules, the 327 sequence U+0130 U+004E would result instead of the expected 'IN'. 329 2.2. Language Subtag Sources and Interpretation 331 The namespace of language tags and their subtags is administered by 332 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 333 the rules in Section 5 of this document. The Language Subtag 334 Registry maintained by IANA is the source for valid subtags: other 335 standards referenced in this section provide the source material for 336 that registry. 338 Terminology used in this document: 340 o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or 341 "az-Arab-IR". Examples of tags in this document are enclosed in 342 double-quotes ("en-US"). 344 o "Subtag" refers to a specific section of a tag, delimited by 345 hyphen, such as the subtags 'zh', 'Hant', and 'CN' in the tag "zh- 346 Hant-CN". Examples of subtags in this document are enclosed in 347 single quotes ('Hant'). 349 o "Code" refers to values defined in external standards (and which 350 are used as subtags in this document). For example, 'Hant' is an 351 [ISO15924] script code that was used to define the 'Hant' script 352 subtag for use in a language tag. Examples of codes in this 353 document are enclosed in single quotes ('en', 'Hant'). 355 Language tags are designed so that each subtag type has unique length 356 and content restrictions. These make identification of the subtag's 357 type possible, even if the content of the subtag itself is 358 unrecognized. This allows tags to be parsed and processed without 359 reference to the latest version of the underlying standards or the 360 IANA registry and makes the associated exception handling when 361 parsing tags simpler. 363 Some of the subtags in the IANA registry do not come from an 364 underlying standard. These can only appear in specific positions in 365 a tag: they can only occur as primary language subtags or as variant 366 subtags. 368 Sequences of private use and extension subtags MUST occur at the end 369 of the sequence of subtags and MUST NOT be interspersed with subtags 370 defined elsewhere in this document. These sequences are introduced 371 by single-character subtags, which are reserved as follows: 373 o The single-letter subtag 'x' introduces a sequence of private use 374 subtags. The interpretation of any private use subtags is defined 375 solely by private agreement and is not defined by the rules in 376 this section or in any standard or registry defined in this 377 document. 379 o The single-letter subtag 'i' is used by some grandfathered tags, 380 such as "i-default", where it always appears in the first position 381 and cannot be confused with an extension. 383 o All other single-letter and single-digit subtags are reserved to 384 introduce standardized extension subtag sequences as described in 385 Section 3.7. 387 2.2.1. Primary Language Subtag 389 The primary language subtag is the first subtag in a language tag and 390 cannot be omitted, with two exceptions: 392 o The single-character subtag 'x' as the primary subtag indicates 393 that the language tag consists solely of subtags whose meaning is 394 defined by private agreement. For example, in the tag "x-fr-CH", 395 the subtags 'fr' and 'CH' do not represent the French language or 396 the country of Switzerland (or any other value in the IANA 397 registry) unless there is a private agreement in place to do so. 398 See Section 4.6. 400 o The single-character subtag 'i' is used by some grandfathered tags 401 (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 402 grandfathered tags have a primary language subtag in their first 403 position.) 405 The following rules apply to the primary language subtag: 407 1. Two-character primary language subtags were defined in the IANA 408 registry according to the assignments found in the standard "ISO 409 639-1:2002, Codes for the representation of names of languages -- 410 Part 1: Alpha-2 code" [ISO639-1], or using assignments 411 subsequently made by the ISO 639-1 registration authority (RA) or 412 governing standardization bodies. 414 2. Three-character primary language subtags in the IANA registry 415 were defined according to the assignments found in one of these 416 additional ISO 639 parts or assignments subsequently made by the 417 relevant ISO 639 registration authorities or governing 418 standardization bodies: 420 A. "ISO 639-2:1998 - Codes for the representation of names of 421 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2] 423 B. "ISO 639-3:2007 - Codes for the representation of names of 424 languages -- Part 3: Alpha-3 code for comprehensive coverage 425 of languages" [ISO639-3] 427 C. "ISO 639-5:2008 - Codes for the representation of names of 428 languages -- Part 5: Alpha-3 code for language families and 429 groups" [ISO639-5] 431 3. The subtags in the range 'qaa' through 'qtz' are reserved for 432 private use in language tags. These subtags correspond to codes 433 reserved by ISO 639-2 for private use. These codes MAY be used 434 for non-registered primary language subtags (instead of using 435 private use subtags following 'x-'). Please refer to Section 4.6 436 for more information on private use subtags. 438 4. Four-character language subtags are reserved for possible future 439 standardization. 441 5. Any language subtags of 5 to 8 characters in length in the IANA 442 registry were defined via the registration process in Section 3.5 443 and MAY be used to form the primary language subtag. An example 444 of what such a registration might include: one of the 445 grandfathered IANA registrations is "i-enochian". The subtag 446 'enochian' could be registered in the IANA registry as a primary 447 language subtag (assuming that ISO 639 does not register this 448 language first), making tags such as "enochian-AQ" and "enochian- 449 Latn" valid. 451 At the time this document was created, there were no examples of 452 this kind of subtag and future registrations of this type are 453 discouraged: primary languages are strongly RECOMMENDED for 454 registration with ISO 639, and proposals rejected by ISO 639/ 455 RA-JAC will be closely scrutinized before they are registered 456 with IANA. 458 6. Other values MUST NOT be assigned to the primary subtag except by 459 revision or update of this document. 461 When languages have both an ISO 639-1 two-character code and a three 462 character code (assigned by ISO 639-2, ISO 639-3, or ISO 639-5), only 463 the ISO 639-1 two-character code is defined in the IANA registry. 465 When languages that have no ISO 639-1 two-character code and for 466 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 467 (Bibliographic) codes differ, only the Terminology code is defined in 468 the IANA registry. At the time this document was created, all 469 languages that had both kinds of three-character code were also 470 assigned a two-character code; it is expected that future assignments 471 of this nature will not occur. 473 In order to avoid instability in the canonical form of tags, if a 474 two-character code is added to ISO 639-1 for a language for which a 475 three-character code was already included in either ISO 639-2 or ISO 476 639-3, the two-character code MUST NOT be registered. See 477 Section 3.4. 479 For example, if some content were tagged with 'haw' (Hawaiian), which 480 currently has no two-character code, the tag would not need to be 481 changed if ISO 639-1 were to assign a two-character code to the 482 Hawaiian language at a later date. 484 To avoid these problems with versioning and subtag choice (as 485 experienced during the transition between RFC 1766 and RFC 3066), as 486 well as to ensure the canonical nature of subtags defined by this 487 document, the ISO 639 Registration Authority Joint Advisory Committee 488 (ISO 639/RA-JAC) has included the following statement in 489 [iso639.prin]: 491 "A language code already in ISO 639-2 at the point of freezing ISO 492 639-1 shall not later be added to ISO 639-1. This is to ensure 493 consistency in usage over time, since users are directed in 494 Internet applications to employ the alpha-3 code when an alpha-2 495 code for that language is not available." 497 2.2.2. Extended Language Subtags 499 Extended language subtags are used to identify certain specially- 500 selected languages that, for various historical and compatibility 501 reasons, are closely identified with or tagged using an existing 502 primary language subtag. Extended language subtags are always used 503 with their enclosing primary language subtag (indicated with a 504 'Prefix' field in the registry) when used to form the language tag. 505 All languages that have an extended language subtag in the registry 506 also have an identical primary language subtag record in the 507 registry. This primary language subtag is RECOMMENDED for forming 508 the language tag. The following rules apply to the extended language 509 subtags: 511 1. Extended language subtags consist solely of three-letter subtags. 512 All extended language subtag records defined in the registry were 513 defined according to the assignments found in [ISO639-3]. 514 Language collections and groupings, such as defined in [ISO639-5] 515 are specifically excluded from being extended language subtags. 517 2. Extended language subtag records MUST include exactly one 518 'Prefix' field indicating an appropriate subtag or sequence of 519 subtags for that extended language subtag. 521 3. Extended language subtag records MUST include a 'Preferred- 522 Value'. The 'Preferred-Value' and 'Subtag' fields MUST be 523 identical. 525 4. Although the ABNF production 'extlang' permits up to three 526 extended language tags in the language tag, extended language 527 subtags MUST NOT include another extended language subtag in 528 their Prefix. That is, the second and third extended language 529 subtag positions in a language tag are permanently reserved and 530 tags that include subtags in that position are invalid. 532 For example, the macrolanguage Chinese ('zh') encompasses a number of 533 languages. For compatibility reasons, each of these languages has 534 both a primary and extended language subtag in the registry. A few 535 selected examples of these include Gan Chinese ('gan'), Cantonese 536 Chinese ('yue') and Mandarin Chinese ('cmn'). Each is encompassed by 537 the macrolanguage 'zh' (Chinese). Therefore, they each have the 538 prefix "zh" in their registry records. Thus Gan Chinese is 539 represented with tags beginning "zh-gan" or "gan"; Cantonese with 540 tags beginning either "yue" or "zh-yue"; and Mandarin Chinese with 541 "zh-cmn" or "cmn". The language subtag 'zh' can still be used 542 without an extended language subtag to label a resource as some 543 unspecified variety of Chinese, while the primary language subtag 544 ('gan', 'yue', 'cmn') is preferred to using the extended language 545 form ("zh-gan", "zh-yue", "zh-cmn"). 547 2.2.3. Script Subtag 549 Script subtags are used to indicate the script or writing system 550 variations that distinguish the written forms of a language or its 551 dialects. The following rules apply to the script subtags: 553 1. Script subtags MUST follow any primary and extended language 554 subtags and MUST precede any other type of subtag. 556 2. Script subtags consist of four letters and were defined according 557 to [ISO15924]--"Codes for the representation of the names of 558 scripts": alpha-4 script codes, or subsequently assigned by the 559 ISO 15924 registration authority or governing standardization 560 bodies, denoting the script or writing system used in conjunction 561 with this language. Only codes assigned by ISO 15924 will be 562 considered for registration. 564 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 565 use in language tags. These subtags correspond to codes reserved 566 by ISO 15924 for private use. These codes MAY be used for non- 567 registered script values. Please refer to Section 4.6 for more 568 information on private use subtags. 570 4. There MUST be at most one script subtag in a language tag, and 571 the script subtag SHOULD be omitted when it adds no 572 distinguishing value to the tag or when the primary or extended 573 language subtag's record in the subtag registry includes a 574 'Suppress-Script' field listing the applicable script subtag. 576 For example: "sr-Latn" represents Serbian written using the Latin 577 script. 579 2.2.4. Region Subtag 581 Region subtags are used to indicate linguistic variations associated 582 with or appropriate to a specific country, territory, or region. 583 Typically, a region subtag is used to indicate variations such as 584 regional dialects or usage, or region-specific spelling conventions. 585 It can also be used to indicate that content is expressed in a way 586 that is appropriate for use throughout a region, for instance, 587 Spanish content tailored to be useful throughout Latin America. 589 The following rules apply to the region subtags: 591 1. Region subtags MUST follow any primary language, extended 592 language, or script subtags and MUST precede any other type of 593 subtag. 595 2. Two-letter region subtags were defined according to the 596 assignments found in [ISO3166-1] ("Codes for the representation 597 of names of countries and their subdivisions -- Part 1: Country 598 codes") using the list of alpha-2 country codes, or using 599 assignments subsequently made by the ISO 3166-1 maintenance 600 agency or governing standardization bodies. In addition, the 601 codes that are "exceptionally reserved" (as opposed to 602 "assigned") in ISO 3166-1 were also defined in the registry, with 603 the exception of 'UK', which is an exact synonym for the assigned 604 code 'GB'. 606 3. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 607 reserved for private use in language tags. These subtags 608 correspond to codes reserved by ISO 3166 for private use. These 609 codes MAY be used for private use region subtags (instead of 610 using a private use subtag sequence). Please refer to 611 Section 4.6 for more information on private use subtags. 613 4. Three-character region subtags consist solely of digit (number) 614 characters and were defined according to the assignments found in 615 UN Standard Country or Area Codes for Statistical Use [UN_M.49] 616 or assignments subsequently made by the governing standards body. 617 Not all of the UN M.49 codes are defined in the IANA registry. 618 The following rules define which codes are entered into the 619 registry as valid subtags: 621 A. UN numeric codes assigned to 'macro-geographical 622 (continental)' or sub-regions MUST be registered in the 623 registry. These codes are not associated with an assigned 624 ISO 3166-1 alpha-2 code and represent supra-national areas, 625 usually covering more than one nation, state, province, or 626 territory. 628 B. UN numeric codes for 'economic groupings' or 'other 629 groupings' MUST NOT be registered in the IANA registry and 630 MUST NOT be used to form language tags. 632 C. When ISO 3166-1 reassigns a code formerly used for one 633 country or area to another country or area and that code 634 already is present in the registry, the UN numeric code for 635 that country or area MUST be registered in the registry as 636 described in Section 3.4 and MUST be used to form language 637 tags that represent the country or region for which it is 638 defined (rather than the recycled ISO 3166-1 code). 640 D. UN numeric codes for countries or areas for which there is an 641 associated ISO 3166-1 alpha-2 code in the registry MUST NOT 642 be entered into the registry and MUST NOT be used to form 643 language tags. Note that the ISO 3166-based subtag in the 644 registry MUST actually be associated with the UN M.49 code in 645 question. 647 E. UN numeric codes and ISO 3166-1 alpha-2 codes for countries 648 or areas listed as eligible for registration in Section 4 of 649 [RFC4645] but not presently registered MAY be entered into 650 the IANA registry via the process described in Section 3.5. 651 Once registered, these codes MAY be used to form language 652 tags. 654 F. All other UN numeric codes for countries or areas that do not 655 have an associated ISO 3166-1 alpha-2 code MUST NOT be 656 entered into the registry and MUST NOT be used to form 657 language tags. For more information about these codes, see 658 Section 3.4. 660 5. The alphanumeric codes in Appendix X of the UN document MUST NOT 661 be entered into the registry and MUST NOT be used to form 662 language tags. (At the time this document was created, these 663 values matched the ISO 3166-1 alpha-2 codes.) 665 6. There MUST be at most one region subtag in a language tag and the 666 region subtag MAY be omitted, as when it adds no distinguishing 667 value to the tag. 669 For example: 671 "de-AT" represents German ('de') as used in Austria ('AT'). 673 "sr-Latn-RS" represents Serbian ('sr') written using Latin script 674 ('Latn') as used in Serbia ('RS'). 676 "es-419" represents Spanish ('es') appropriate to the UN-defined 677 Latin America and Caribbean region ('419'). 679 2.2.5. Variant Subtags 681 Variant subtags are used to indicate additional, well-recognized 682 variations that define a language or its dialects that are not 683 covered by other available subtags. The following rules apply to the 684 variant subtags: 686 1. Variant subtags MUST follow any primary language, extended 687 language, script, or region subtags, and MUST precede any 688 extension or private use subtag sequences. 690 2. Variant subtags, as a collection, are not associated with any 691 particular external standard. The meaning of variant subtags in 692 the registry is defined in the course of the registration process 693 defined in Section 3.5. Note that any particular variant subtag 694 might be associated with some external standard. However, 695 association with a standard is not required for registration. 697 3. More than one variant MAY be used to form the language tag. 699 4. Variant subtags MUST be registered with IANA according to the 700 rules in Section 3.5 of this document before being used to form 701 language tags. In order to distinguish variants from other types 702 of subtags, registrations MUST meet the following length and 703 content restrictions: 705 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 706 at least five characters long. 708 2. Variant subtags that begin with a digit (0-9) MUST be at 709 least four characters long. 711 5. The same variant subtag MUST NOT be used more than once within a 712 language tag. 714 * For example, the tag "de-DE-1901-1901" is not valid. 716 Variant subtag records in the language subtag registry MAY include 717 one or more 'Prefix' fields. The 'Prefix' indicates a sequence of 718 subtags that would make a suitable prefix (with other subtags, as 719 appropriate) in forming a language tag with the variant. That is, 720 each of the subtags in the prefix SHOULD appear, in order, before the 721 variant. For example, the subtag 'nedis' has a Prefix of "sl", 722 making it suitable for forming language tags such as "sl-nedis" and 723 "sl-IT-nedis", but not suitable for use in a tag such as "zh-nedis" 724 or "it-IT-nedis". 726 Most variants that share a prefix are mutually exclusive. For 727 example, the German orthographic variations '1996' and '1901' SHOULD 728 NOT be used in the same tag, as they represent the dates of different 729 spelling reforms. A variant that can meaningfully be used in 730 combination with another variant SHOULD include a 'Prefix' field in 731 its registry record that lists that other variant. For example, if 732 another German variant 'example' were created that made sense to use 733 with '1996', then 'example' should include two Prefix fields: "de" 734 and "de-1996". 736 For example: 738 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 740 "de-CH-1996" represents German as used in Switzerland and as 741 written using the spelling reform beginning in the year 1996 C.E. 743 2.2.6. Extension Subtags 745 Extensions provide a mechanism for extending language tags for use in 746 various applications. They are intended to identify information 747 which is commonly used in association with languages or language 748 tags, but which is not part of language identification. See 749 Section 3.7. The following rules apply to extensions: 751 1. An extension MUST follow at least a primary language subtag. 752 That is, a language tag cannot begin with an extension. 753 Extensions extend language tags, they do not override or replace 754 them. For example, "a-value" is not a well-formed language tag, 755 while "de-a-value" is. Note that extensions cannot be used in 756 tags that are entirely private use (that is, tags starting with 757 "x-"). 759 2. Extension subtags are separated from the other subtags defined in 760 this document by a single-character subtag (called a 761 "singleton"). The singleton MUST be one allocated to a 762 registration authority via the mechanism described in Section 3.7 763 and MUST NOT be the letter 'x', which is reserved for private use 764 subtag sequences. 766 3. Each singleton subtag MUST appear at most one time in each tag 767 (other than as a private use subtag). That is, singleton subtags 768 MUST NOT be repeated. For example, the tag "en-a-bbb-a-ccc" is 769 invalid because the subtag 'a' appears twice. Note that the tag 770 "en-a-bbb-x-a-ccc" is valid because the second appearance of the 771 singleton 'a' is in a private use sequence. 773 4. Extension subtags MUST meet whatever requirements are set by the 774 document that defines their singleton prefix and whatever 775 requirements are provided by the maintaining authority. Note 776 that there might not be a registry of these subtags and 777 validating processors are not required to validate extensions. 779 5. Each extension subtag MUST be from two to eight characters long 780 and consist solely of letters or digits, with each subtag 781 separated by a single '-'. Case distinctions are ignored in 782 extensions (as with any language subtag) and normalized subtags 783 of this type are expected to be in lowercase. 785 6. Each singleton MUST be followed by at least one extension subtag. 786 For example, the tag "tlh-a-b-foo" is invalid because the first 787 singleton 'a' is followed immediately by another singleton 'b'. 789 7. Extension subtags MUST follow all primary language, extended 790 language, script, region, and variant subtags in a tag and MUST 791 precede any private-use subtag sequences. 793 8. All subtags following the singleton and before another singleton 794 are part of the extension. Example: In the tag "fr-a-Latn", the 795 subtag 'Latn' does not represent the script subtag 'Latn' defined 796 in the IANA Language Subtag Registry. Its meaning is defined by 797 the extension 'a'. 799 9. In the event that more than one extension appears in a single 800 tag, the tag SHOULD be canonicalized as described in Section 4.5. 802 For example, if an extention were defined for the singleton 'r' and 803 it defined the subtags shown, then the following tag would be a valid 804 example: "en-Latn-GB-boont-r-extended-sequence-x-private" 806 2.2.7. Private Use Subtags 808 Private use subtags are used to indicate distinctions in language 809 important in a given context by private agreement. The following 810 rules apply to private use subtags: 812 1. Private use subtags are separated from the other subtags defined 813 in this document by the reserved single-character subtag 'x'. 815 2. Private use subtags MUST conform to the format and content 816 constraints defined in the ABNF for all subtags, that is, they 817 MUST consist solely of letters and digits and not exceed eight 818 characters in length. 820 3. Private use subtags MUST follow all primary language, extended 821 language, script, region, variant, and extension subtags in the 822 tag. Another way of saying this is that all subtags following 823 the singleton 'x' MUST be considered private use. Example: The 824 subtag 'US' in the tag "en-x-US" is a private use subtag. 826 4. A tag MAY consist entirely of private use subtags. 828 5. No source is defined for private use subtags. Use of private use 829 subtags is by private agreement only. 831 6. Private use subtags are NOT RECOMMENDED where alternatives exist 832 or for general interchange. See Section 4.6 for more information 833 on private use subtag choice. 835 For example: The Unicode Consortium defines a set of private use 836 extensions in LDML ([UTS35], Locale Data Markup Language, the Unicode 837 standard for defining locale data) such as in the tag "es-419-x-ldml- 838 collatio-traditio", which indicates Latin American Spanish with 839 traditional order for sorted lists. 841 2.2.8. Grandfathered and Redundant Registrations 843 Prior to RFC 4646, whole language tags were registered according to 844 the rules in RFC 1766 and/or RFC 3066. All of these registered tags 845 remain valid as language tags. 847 Many of these registered tags were made redundant by the advent of 848 either RFC 4646 or this document. A redundant tag is a grandfathered 849 registration whose individual subtags appear with the same semantic 850 meaning in the registry. For example, the tag "zh-Hant" (Traditional 851 Chinese) can now be composed from the subtags 'zh' (Chinese) and 852 'Hant' (Han script traditional variant). These redundant tags are 853 maintained in the registry as records of type "redundant", mostly as 854 a matter of historical curiousity. 856 The remainder of the previously registered tags are "grandfathered". 857 These tags are classified into two groups: 'regular' and 'irregular'. 859 Grandfathered tags that (appear to) match the 'langtag' production in 860 Figure 1 are considered 'regular' grandfathered tags. These tags 861 either contain subtags that do not individually appear in the 862 registry, or their subtags appear but with a different semantic 863 meaning: each tag, in its entirety, represents a language or 864 collection of languages. 866 Grandfathered tags that do not match the 'langtag' production in the 867 ABNF and would otherwise be invalid are considered 'irregular' 868 grandfathered tags. With the exception of "en-GB-oed", which is a 869 variant of "en-GB", each of them, in its entirety, represents a 870 language. 872 Many of the grandfathered tags have been superseded by the subsequent 873 addition of new subtags: each superseded record contains a Preferred- 874 Value field that ought to be used to form language tags representing 875 that value. For example, the tag "art-lojban" is superseded by the 876 primary language subtag 'jbo'. 878 2.2.9. Classes of Conformance 880 Implementations sometimes need to describe their capabilities with 881 regard to the rules and practices described in this document. Tags 882 can be checked or verified in a number of ways, but two particular 883 classes of tag conformance are formally defined here. 885 A tag is considered "well-formed" if it conforms to the ABNF 886 (Section 2.1). Language tags may be well-formed in terms of syntax 887 but not valid in terms of content. However, many operations 888 involving language tags work well without knowing anything about the 889 meaning or validity of the subtags. 891 A tag is considered "valid" if it satisfies these conditions: 893 o The tag is well-formed. 895 o The tag is either in the list of grandfathered tags or all of its 896 primary language, extended language, script, region, and variant 897 subtags appear in the IANA language subtag registry as of the 898 particular registry date. 900 o There are no duplicate variant subtags. 902 o There are no duplicate singleton (extension) subtags. 904 Note that a tag's validity depends on the date of the registry used 905 to validate the tag. A more recent copy of the registry might 906 contain a subtag that an older version does not. 908 A tag is considered "valid" for a given extension (Section 3.7) (as 909 of a particular version, revision, and date) if it meets the criteria 910 for "valid" above and also satisfies this condition: 912 Each subtag used in the extension part of the tag is valid 913 according to the extension. 915 Older specifications or language tag implementations sometimes 916 reference [RFC3066]. A wider array of tags was considered 'well- 917 formed' under that document. Any tags that were valid for use under 918 RFC 3066 are both 'well-formed' and 'valid' under this document's 919 syntax; only invalid or illegal tags were well-formed by the early 920 definition but no longer are. The language tag syntax under RFC 3066 921 was: 923 obs-language-tag = primary-subtag *( "-" subtag ) 924 primary-subtag = 1*8ALPHA 925 subtag = 1*8(ALPHA / DIGIT) 927 Figure 2: RFC 3066 Language Tag Syntax 929 Subtags designated for private use as well as private-use sequences 930 introduced by the 'x' subtag are available for cases in which no 931 assigned subtags are available and registration is not a suitable 932 option. For example, one might use a tag such as "no-QQ", where 'QQ' 933 is one of a range of private-use ISO 3166-1 codes to indicate an 934 otherwise-undefined region. Users MUST NOT assign language tags that 935 use subtags that do not appear in the registry other than in private- 936 use sequences (such the subtag 'personal' in the tag "en-x- 937 personal"). Besides not being 'valid', the user also risks collision 938 with a future possible assignment or registrations. 940 Note well: although the 'Language-Tag' production appearing in this 941 document is functionally equivalent to the one in [RFC4646], it has 942 been changed to prevent certain errors in well-formedness arising 943 from the old 'grandfathered' production. This version of the ABNF is 944 RECOMMENDED as a replacement for the older version. 946 3. Registry Format and Maintenance 948 The IANA Language Subtag Registry ("the registry") contains a 949 comprehensive list of all of the subtags valid in language tags. 950 This allows implementers a straightforward and reliable way to 951 validate language tags. The registry will be maintained so that, 952 except for extension subtags, it is possible to validate all of the 953 subtags that appear in a language tag under the provisions of this 954 document or its revisions or successors. In addition, the meaning of 955 the various subtags will be unambiguous and stable over time. (The 956 meaning of private use subtags, of course, is not defined by the 957 registry.) 959 This section defines the registry along with the maintenance and 960 update procedures associated with it, as well as a registry for 961 extensions to language tags (Section 3.7). 963 3.1. Format of the IANA Language Subtag Registry 965 The IANA Language Subtag Registry is a machine-readable file in the 966 format described in this section, plus copies of the registration 967 forms approved in accordance with the process described in 968 Section 3.5. 970 The existing registration forms for grandfathered and redundant tags 971 taken from RFC 3066 have been maintained as part of the obsolete RFC 972 3066 registry. The subtags added to the registry by either [RFC4645] 973 or [registry-update] do not have separate registration forms (so no 974 forms are archived for these additions). 976 3.1.1. File Format 978 The registry is a [Unicode] text file, using the UTF-8 [RFC3629] 979 character encoding, and consists of a series of records stored in the 980 record-jar format (described in [record-jar]). Each record, in turn, 981 consists of a series of fields that describe the various subtags and 982 tags. 984 Each field can be considered a single, logical line of characters. 985 Each field contains a 'field-name' and a 'field-body'. These are 986 separated by a 'field-separator'. The field-separator is a COLON 987 character (%x3A) plus any surrounding whitespace. Each field is 988 terminated by the newline sequence CRLF. The text in each field MUST 989 be in Unicode Normalization Form C (NFC). 991 A collection of fields forms a 'record'. Records are separated by 992 lines containing only the sequence "%%" (%x25.25). 994 Although fields are logically a single line of text, each line of 995 text in the file format is limited to 72 bytes in length. To 996 accommodate this, the field-body can be split into a multiple-line 997 representation; this is called "folding". Folding is done according 998 to customary conventions for line-wrapping. This is typically on 999 whitespace boundaries, but can occur between other characters when 1000 the value does not include spaces, such as when a language does not 1001 use whitespace between words. In any event, there MUST NOT be breaks 1002 inside a multibyte UTF-8 sequence nor in the middle of a combining 1003 character sequence. For more information, see [UAX14]. 1005 Although the file format uses the UTF-8 encoding, fields are 1006 restricted to the printable characters from the US-ASCII [ISO646] 1007 repertoire unless otherwise indicated in the description of a 1008 specific field-name (Section 3.1.2). 1010 The format of the registry is described by the following ABNF (per 1011 [RFC5234]): 1013 registry = record *("%%" CRLF record) 1014 record = 1*field 1015 field = ( field-name field-sep field-body CRLF ) 1016 field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] 1017 field-sep = *SP ":" *SP 1018 field-body = *([[*SP CRLF] 1*SP] 1*CHARS) 1019 CHARS = (%x21-10FFFF) ; Unicode code points 1021 Figure 3: Registry Format ABNF 1023 The sequence '..' (%x2E.2E) in a field-body denotes a range of 1024 values. Such a range represents all subtags of the same length that 1025 are in alphabetic or numeric order within that range, including the 1026 values explicitly mentioned. For example 'a..c' denotes the values 1027 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 1028 '13'. 1030 All fields whose field-body contains a date value use the "full-date" 1031 format specified in [RFC3339]. For example: "2004-06-28" represents 1032 June 28, 2004, in the Gregorian calendar. 1034 3.1.2. Record and Field Definitions 1036 There are three types of records in the registry: "File-Date", 1037 "Subtag", and "Tag". 1039 The first record in the registry is always the "File-Date" record. 1040 This record occurs only once in the file and contains a single field 1041 whose field-name is "File-Date". The field-body of this record 1042 contains the last modification date of this copy of the registry, 1043 making it possible to compare different versions of the registry. 1044 The registry on the IANA website is the most current. Versions with 1045 an older date than that one are not up-to-date. 1047 File-Date: 2004-06-28 1048 %% 1050 Figure 4: Example of the File-Date Record 1052 Subsequent records contain multiple fields and represent information 1053 about either subtags or tags. Both types of record have identical 1054 structure, except that "Subtag" records contain a field with a field- 1055 name of "Subtag", while, unsurprisingly, "Tag" records contain a 1056 field with a field-name of "Tag". Field-names MUST occur no more 1057 than once per record, with the exception of the 'Description', 1058 'Comments', and sometimes the 'Prefix' field. 1060 Each record MUST contain at least one of each of the following 1061 fields: 1063 o 'Type' 1065 * Type's field-body MUST consist of one of the following strings: 1066 "language", "extlang", "script", "region", "variant", 1067 "grandfathered", and "redundant", and denotes the type of tag 1068 or subtag. 1070 o Either 'Subtag' or 'Tag' 1072 * Subtag's field-body contains the subtag being defined. This 1073 field MUST appear in all records whose 'Type' has one of these 1074 values: "language", "extlang", "script", "region", or 1075 "variant". 1077 * Tag's field-body contains a complete language tag. This field 1078 MUST appear in all records whose 'Type' has one of these 1079 values: "grandfathered" or "redundant". If the 'Type' is 1080 "grandfathered", then the 'Tag' field-body will be one of the 1081 tags listed in either the 'regular' or 'irregular' production 1082 in found in Section 2.1. 1084 o Description 1086 * Description's field-body contains a non-normative description 1087 of the subtag or tag. 1089 o Added 1091 * Added's field-body contains the date the record was registered 1092 or, in the case of grandfathered or redundant tags, the date 1093 the corresponding tag was registered under the rules of 1094 [RFC1766] or [RFC3066]. 1096 Each record MAY also contain the following fields: 1098 o Deprecated 1100 * Deprecated's field-body contains the date the record was 1101 deprecated. In some cases this value is earlier than that of 1102 the 'Added' field in the same record. That is, the date of 1103 deprecation preceded the addition of the record to the 1104 registry. 1106 o Preferred-Value 1108 * Preferred-Value's field body contains a canonical mapping from 1109 this record's value to a modern equivalent that is preferred in 1110 its place. Depending on the value of the 'Type' field, this 1111 value can take different forms: 1113 + For fields of type 'language', 'Preferred-Value' contains 1114 the primary language subtag that is preferred when forming 1115 the language tag. 1117 + For fields of type 'script', 'region', or 'variant', 1118 'Preferred-Value' contains the subtag of the same type that 1119 is preferred for forming the language tag. 1121 + For fields of type 'extlang', 'grandfathered', or 1122 'redundant', 'Preferred-Value' contains an "extended 1123 language range" ([RFC4647]) that is preferred for forming 1124 the language tag. That is, each of the subtags that appears 1125 in the value MUST appear in the replacement tag; additional 1126 fields can be included in a language tag as described 1127 elsewhere in this document. For example, the replacement 1128 for the grandfathered tag "zh-min-nan" (Min Nan Chinese) is 1129 "nan", which can be used as the basis for tags such as "nan- 1130 Hant" or "nan-TW" (note that the extended language subtag 1131 form such as "zh-nan-Hant" or "zh-nan-TW" can also be used). 1133 o Prefix 1135 * Prefix's field-body contains a "entended language range" 1136 (basically, a collection of subtags, see [RFC4647]) which 1137 SHOULD be used with this subtag when forming language tag. The 1138 Prefix's subtags appear before the subtag. This field MUST 1139 appear only in records whose 'Type' field-body is either 1140 'extlang' or 'variant'. 1142 For example, the variant 'nedis' (Nadiza dialect) has a 1143 'Prefix' of "sl" (Slovenian), meaning that tags such as "sl- 1144 nedis" and "sl-IT-nedis" are appropriate, while the tag "is- 1145 nedis" (Icelandic, Nadiza dialect) is not. 1147 o Suppress-Script 1149 * Suppress-Script's field-body contains a script subtag that 1150 SHOULD NOT be used to form language tags with the associated 1151 primary or extended language subtag. This field MUST appear 1152 only in records whose 'Type' field-body is "language" or 1153 "extlang". See Section 4.1. 1155 o Macrolanguage 1157 * Macrolanguage's field-body contains a primary language subtag 1158 defined by ISO 639 as the "macrolanguage" that encompasses this 1159 language subtag. This field MUST appear only in records whose 1160 'Type' field-body is either "language". 1162 o Scope 1164 * Scope's field-body contains information about a primary or 1165 extended language subtag indicating the type of language code 1166 according to ISO 639. The values permitted in this field are 1167 "macrolanguage", "collection", "special" and "private-use". 1168 This field only appears in records whose 'Type' field-body is 1169 either "language" or "extlang". When this field is omitted, 1170 the language is an individual language. 1172 o Comments 1174 * Comments's field-body contains additional information about the 1175 subtag, as deemed appropriate for understanding the registry 1176 and implementing language tags using the subtag or tag. 1178 Future versions of this document might add additional fields to the 1179 registry; implementations SHOULD ignore fields found in the registry 1180 that are not defined in this document. 1182 3.1.3. Type Field 1184 The field 'Type' contains the string identifying the record type it 1185 appears in. Values for the 'Type' field-body are: "language" 1186 (Section 2.2.1); "extlang" (Section 2.2.2); "script" (Section 2.2.3); 1187 "region" (Section 2.2.4); "variant" (Section 2.2.5); "grandfathered" 1188 or "redundant" (Section 2.2.8). 1190 3.1.4. Subtag and Tag Fields 1192 The field 'Subtag' contains the subtag defined in the record. The 1193 field 'Tag' appears in records whose 'Type' is either 'grandfathered' 1194 or 'redundant' and contains a tag registered under [RFC3066]. 1196 The 'Subtag' field-body MUST follow the casing conventions described 1197 in Section 2.1.1. All subtags use lowercase letters in the field- 1198 body, with two exceptions: 1200 Subtags whose 'Type' field is 'script' (in other words, subtags 1201 defined by ISO 15924) MUST use titlecase. 1203 Subtags whose 'Type' field is 'region' (in other words, the non- 1204 numeric region subtags defined by ISO 3166-1) MUST use all 1205 uppercase. 1207 The 'Tag' field-body MUST be formatted according to the rules 1208 described in Section 2.1.1. 1210 3.1.5. Description Field 1212 The field 'Description' contains a description of the tag or subtag 1213 in the record. The 'Description' field MAY appear more than once per 1214 record. The 'Description' field MAY include the full range of 1215 Unicode characters. At least one of the 'Description' fields MUST be 1216 written or transcribed into the Latin script; additional 1217 'Description' fields MAY be in any script or language. 1219 The 'Description' field is used for identification purposes. 1220 Descriptions SHOULD contain all and only that information necessary 1221 to distinguish one subtag from others that it might be confused with. 1222 They are not intended to provide general background information, nor 1223 to provide all possible alternate names or designations. 1224 'Description' fields don't necessarily represent the actual native 1225 name of the item in the record, nor are any of the descriptions 1226 guaranteed to be in any particular language (such as English or 1227 French, for example). 1229 Descriptions in the registry that correspond to ISO 639, ISO 15924, 1230 ISO 3166-1, or UN M.49 codes are intended only to indicate the 1231 meaning of that identifier as defined in the source standard at the 1232 time it was added to the registry or as subsequently modified, within 1233 the bounds of the stability rules (Section 3.4), via subsequent 1234 registration. The 'Description' does not replace the content of the 1235 source standard itself. 'Description' fields are not intended to be 1236 the localized English names for the subtags. Localization or 1237 translation of language tag and subtag descriptions is out of scope 1238 of this document. 1240 For subtags taken from a source standard (such as ISO 639 or ISO 1241 15924), the 'Description' fields in the record are also initially 1242 taken from that source standard. Multiple descriptions in the source 1243 standard are split into separate 'Description' fields. The source 1244 standard's descriptions MAY be edited or modified, either prior to 1245 insertion or via the registration process, and additional or 1246 extraneous descriptions omitted or removed. Each 'Description' field 1247 MUST be unique within the record in which it appears and formatting 1248 variations of the same description SHOULD NOT occur in that specific 1249 record. For example, while the ISO 639-1 code 'fy' has both the 1250 description "Western Frisian" and and the description "Frisian, 1251 Western" in that standard, only one of these descriptions appears in 1252 the registry. 1254 To help ensure that users do not become confused about which subtag 1255 to use, 'Description' fields assigned to a record of any specific 1256 type ('language', 'extlang', 'script', and so on) MUST be unique 1257 within that given record type with the following exception: if a 1258 particular 'Description' field occurs in multiple records of a given 1259 type, then at most one of the records can omit the 'Deprecated' 1260 field; all deprecated records that share a 'Description' MUST have 1261 the same 'Preferred-Value'; and all non-deprecated records MUST be 1262 that 'Preferred-Value'. This means that two records of the same type 1263 that share a 'Description' are also semantically equivalent and no 1264 more than one record with a given 'Description' is preferred for that 1265 meaning. 1267 For example, consider the 'language' subtags 'zza' (Zaza) and 'diq' 1268 (Dimli). It so happens that 'zza' is a macrolanguage enclosing 'diq' 1269 and thus also has a description in ISO 639-3 of "Dimli". This 1270 description was edited to read "Dimli (macrolanguage)" in the 1271 registry record for 'zza' to prevent a collision. 1273 By contrast, the subtags 'he' and 'iw' share a 'Description' value of 1274 "Hebrew"; this is permitted because 'iw' is deprecated and its 1275 'Preferred-Value' is 'he'. 1277 For fields of type 'language', the first 'Description' field 1278 appearing in the Registry corresponds whenever possible to the 1279 Reference Name assigned by ISO 639-3. This helps facilitate cross- 1280 referencing between ISO 639 and the registry. 1282 When creating or updating a record due to the action of one of the 1283 source standards, the Language Subtag Reviewer MAY edit descriptions 1284 to correct irregularities in formatting (such as misspellings, 1285 inappropriate apostrophes or other punctuation, or excessive or 1286 missing spaces) prior to submitting the proposed record to the ietf- 1287 languages list for consideration. 1289 3.1.6. Deprecated Field 1291 The field 'Deprecated' contains the date the record was deprecated 1292 and MAY be added, changed, or removed from any record via the 1293 maintenance process described in Section 3.3 or via the registration 1294 process described in Section 3.5. Usually, the addition of a 1295 'Deprecated' field is due to the action of one of the standards 1296 bodies, such as ISO 3166, withdrawing a code. Although valid in 1297 language tags, subtags and tags with a 'Deprecated' field are 1298 deprecated and validating processors SHOULD NOT generate these 1299 subtags. Note that a record that contains a 'Deprecated' field and 1300 no corresponding 'Preferred-Value' field has no replacement mapping. 1302 In some historical cases, it might not have been possible to 1303 reconstruct the original deprecation date. For these cases, an 1304 approximate date appears in the registry. Some subtags and some 1305 grandfathered or redundant tags were deprecated before the initial 1306 creation of the registry. The exact rules for this appear in Section 1307 2 of [RFC4645]. Note that these records have a 'Deprecated' field 1308 with an earlier date then the corresponding 'Added' field! 1310 3.1.7. Preferred-Value Field 1312 The field 'Preferred-Value' contains a mapping between the record in 1313 which it appears and another tag or subtag (depending on the record's 1314 'Type'). The value in this field is used for canonicalization (see 1315 Section 4.5). In cases where the subtag or tag also has a 1316 'Deprecated' field, then the 'Preferred-Value' is RECOMMENDED as the 1317 best choice to represent the value of this record when selecting a 1318 language tag. 1320 Records containing a Preferred-Value fall into one of these four 1321 groups: 1323 1. ISO 639 language codes that were later withdrawn in favor of 1324 other codes. These values are mostly a historical curiosity. 1325 The 'he'/'iw' pairing above is an example of this. 1327 2. Subtags (with types other than language or extlang) taken from 1328 codes or values that have been withdrawn in favor of a new code. 1329 In particular, this applies to region subtags taken from ISO 1330 3166-1, because sometimes a country will change its name or 1331 administration in such a way that warrants a new region code. In 1332 some cases, countries have reverted to an older name, which might 1333 already be encoded. For example, the subtag 'ZR' (Zaire) was 1334 replaced by the subtag 'CD' (Democratic Republic of the Congo) 1335 when that country's name was changed. 1337 3. Tags or subtags that have become obsolete because the values they 1338 represent were later encoded. Many of the grandfathered or 1339 redundant tags were later encoded by ISO 639, for example, and 1340 fall into this grouping. For example, "i-klingon" was deprecated 1341 when the subtag 'tlh' was added. The record for "i-klingon" has 1342 a 'Preferred-Value' of 'tlh'. 1344 4. Extended language subtags always have a mapping to their 1345 identical primary language subtag. For example, the extended 1346 language subtag 'yue' (Cantonese) can be used to form the tag 1347 "zh-yue". It has a Preferred-Value mapping to the primary 1348 language subtag 'yue', meaning that a tag such as 1349 "zh-yue-Hant-HK" can be canonicalized to "yue-Hant-HK". 1351 Records other than those of type 'extlang' that contain a 'Preferred- 1352 Value' field MUST also have a 'Deprecated' field. This field 1353 contains the date on which the tag or subtag was deprecated in favor 1354 of the preferred value. 1356 For records of type 'extlang', the 'Preferred-Value' field appears 1357 without a corresponding 'Deprecated' field. An implementation MAY 1358 ignore these preferred value mappings, although if it ignores the 1359 mapping, it SHOULD do so consistently. It SHOULD also treat the 1360 Preferred-Value as equivalent to the mapped item. For example, the 1361 tags "zh-yue-Hant-HK" and "yue-Hant-HK" are semantically equivalent 1362 and ought to be treated as if they were the same tag. 1364 Occasionally the deprecated code is preferred in certain contexts. 1365 For example, both "iw" and "he" can be used in the Java programming 1366 language, but "he" is converted on input to "iw", which is thus the 1367 canonical form in Java. 1369 'Preferred-Value' mappings in records of type 'region' sometimes do 1370 not represent exactly the same meaning as the original value. There 1371 are many reasons for a country code to be changed, and the effect 1372 this has on the formation of language tags will depend on the nature 1373 of the change in question. For example, the region subtag 'YD' 1374 (Democratic Yemen) was deprecated in favor of the subtag 'YE' (Yemen) 1375 when those two countries unified in 1990. 1377 A 'Preferred-Value' MAY be added to, changed, or removed from records 1378 according to the rules in Section 3.3. Addition, modification, or 1379 removal of a 'Preferred-Value' field in a record does not imply that 1380 content using the affected subtag needs to be retagged. 1382 The 'Preferred-Value' fields in records of type "grandfathered" and 1383 "redundant" each contain an "extended language range" ([RFC4647]) 1384 that is strongly RECOMMENDED for use in place of the record's value. 1385 In many cases, these mappings were created via deprecation of the 1386 tags during the period before [RFC4646] was adopted. For example, 1387 the tag "no-nyn" was deprecated in favor of the ISO 639-1-defined 1388 language code 'nn'. 1390 The 'Preferred-Value' field in subtag records of type "extlang" also 1391 contains an "extended language range". This allows the subtag to be 1392 deprecated in favor of either a single primary language subtag or a 1393 new language-extlang sequence. 1395 Usually the addition, removal, or change of a Preferred-Value field 1396 for a subtag is done to reflect changes in one of the source 1397 standards. For example, if an ISO 3166-1 region code is deprecated 1398 in favor of another code, that SHOULD result in the addition of a 1399 Preferred-Value field. 1401 Changes to one subtag MAY affect other subtags as well: when 1402 proposing changes to the registry, the Language Subtag Reviewer will 1403 review the registry for such effects and propose the necessary 1404 changes using the process in Section 3.5, although anyone MAY request 1405 such changes. For example: 1407 Suppose that subtag 'XX' has a Preferred-Value of 'YY'. If 'YY' 1408 later changes to have a Preferred-Value of 'ZZ', then the 1409 Preferred-Value for 'XX' MUST also change to be 'ZZ'. 1411 Suppose that a registered language subtag 'dialect' represents a 1412 language not yet available in any part of ISO 639. The later 1413 addition of a corresponding language code in ISO 639 SHOULD result 1414 in the addition of a Preferred-Value for 'dialect'. 1416 3.1.8. Prefix Field 1418 The 'Prefix' field contains an "extended language range" (see: 1419 [RFC4647]) whose subtags are appropriate to use with this subtag: 1420 each of the subtags in one of the subtag's Prefix fields SHOULD 1421 appear before the variant in a valid tag. For example, the variant 1422 subtag '1996' has a 'Prefix' field of "de". This means that tags 1423 starting with the sequence "de-" are appropriate with this subtag, so 1424 "de-Latg-1996" and "de-CH-1996" are both acceptable, while the tag 1425 "fr-1996" is an inappropriate choice. 1427 The field of type 'Prefix' MUST NOT be removed from any record. The 1428 field-body for this type of field MAY be modified, but only if the 1429 modification broadens the meaning of the subtag. That is, the field- 1430 body can be replaced only by a prefix of itself. For example, the 1431 Prefix "be-Latn" (Belarusian, Latin script) could be replaced by the 1432 Prefix "be" (Belarusian) but not by the Prefix "ru-Latn" (Russian, 1433 Latin script). 1435 Records of type 'variant' MAY have more than one field of type 1436 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1437 record via the registration process. Fields of type 'extlang' MUST 1438 have exactly one Prefix field. 1440 The field-body of the 'Prefix' field MUST NOT conflict with any 1441 'Prefix' already registered for a given record. Such a conflict 1442 would occur when no valid tag could be constructed that would contain 1443 the prefix, such as when two subtags each have a 'Prefix' that 1444 contains the other subtag. For example, suppose that the subtag 1445 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' 1446 cannot given the prefix 'avariant', for that would require a tag of 1447 the form "es-avariant-bvariant-avariant", which would not be valid. 1449 3.1.9. Suppress-Script Field 1451 The field 'Suppress-Script' contains a script subtag (whose record 1452 appears in the registry). The field 'Suppress-Script' MUST appear 1453 only in records whose 'Type' field-body is either 'language' or 1454 'extlang'. This field MUST NOT appear more than one time in a 1455 record. 1457 This field indicates a script used to write the overwhelming majority 1458 of documents for the given language. The subtag for such a script 1459 therefore adds no distinguishing information to a language tag and 1460 thus SHOULD NOT be used for most documents in that language. 1461 Omitting the script subtag indicated by this field helps ensure 1462 greater compatibility between the language tags generated according 1463 to the rules in this document and language tags and tag processors or 1464 consumers based on RFC 3066. For example, virtually all Icelandic 1465 documents are written in the Latin script, making the subtag 'Latn' 1466 redundant in the tag "is-Latn". 1468 Many language subtag records do not have a 'Suppress-Script' field. 1469 The lack of a 'Suppress-Script' might indicate that the language is 1470 customarily written in more than one script or that the language is 1471 not customarily written at all. It might also mean that sufficient 1472 information was not available when the record was created and thus 1473 remains a candidate for future registration. 1475 3.1.10. Macrolanguage Field 1477 The field 'Macrolanguage' contains a primary language subtag (whose 1478 record appears in the registry). This field indicates a language 1479 that encompasses this subtag's language according to assignments made 1480 by ISO 639-3. 1482 ISO 639-3 labels some languages in the registry as "macrolanguages". 1483 ISO 639-3 defines the term "Macrolanguage" to mean "clusters of 1484 closely-related language varieties that [...] can be considered 1485 distinct individual languages, yet in certain usage contexts a single 1486 language identity for all is needed". These correspond to codes 1487 registered in ISO 639-2 as individual languages that were found to 1488 correspond to more than one language in ISO 639-3. 1490 A language contained within a macrolanguage is called an "encompassed 1491 language". The record for each encompassed language contains a 1492 'Macrolanguage' field in the registry; the macrolanguages themselves 1493 are not specially marked. Note that some encompassed languages have 1494 ISO 639-1 or ISO 639-2 codes. 1496 The Macrolanguage field can only occur in records of type 'language' 1497 or 'extlang'. Only values assigned by ISO 639-3 will be considered 1498 for inclusion. Macrolanguage fields MAY be added or removed via the 1499 normal registration process whenever ISO 639-3 defines new values or 1500 withdraws old values. Macrolanguages are informational, and MAY be 1501 removed or changed if ISO 639-3 changes the values. For more 1502 information on the use of this field and choosing between 1503 macrolanguage and encompassed language subtags, see Section 4.1.1. 1505 For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' 1506 (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' 1507 (Norwegian). For more information see Section 4.1. 1509 3.1.11. Scope Field 1511 The field 'Scope' contains classification information about a primary 1512 or extended language subtag derived from ISO 639. Most languages 1513 have a scope of 'individual', which means that the language is not a 1514 macrolanguage, collection, special code, or private use. That is, it 1515 is what one would normally consider to be 'a language'. Any primary 1516 or extended language subtag that has no 'Scope' field is an 1517 individual language. 1519 Scope information can sometimes be helpful in selecting language 1520 tags, since it indicates the purpose or "scope" of the code 1521 assignment within ISO 639. The available values are: 1523 o 'macrolanguage' - Indicates a macrolanguage as defined by ISO 1524 639-3 (see above (Section 3.1.10)). A macrolanguage is a cluster 1525 of closely-related languages that are sometimes considered to be a 1526 single language. 1528 o 'collection' - Indicates a subtag that represents a collection of 1529 languages, typically related by some type of historical, 1530 geographical, or linguistic association. Unlike a macrolanguage, 1531 a collection can contain languages that are only loosely related 1532 and a collection cannot be used interchangeably with languages 1533 that belong to it. 1535 o 'special' - Indicates a special language code. These are subtags 1536 used for identifying linguistic attributes not particularly 1537 associated with a concrete language. These include codes for when 1538 the language is undetermined or for non-linguistic content. 1540 o 'private-use' - Indicates a code reserved for private use in the 1541 underlying standard. Subtags with this scope can be used to 1542 indicate a primary language for which no ISO 639 or registered 1543 assignment exists. 1545 The Scope field MAY appear in records of type 'language' or 1546 'extlang'. Note that many of the prefixes for extended language 1547 subtags will have a Scope of 'macrolanguage' (although some will not) 1548 and that many languages that have a Scope of 'macrolanguage' will 1549 have extended language subtags associated with them. 1551 The Scope field MAY be added, modified, or removed via the 1552 registration process, provided the change mirrors changes by ISO 639 1553 to the assignment's classification. Such a change is expected to be 1554 rare. 1556 For example, the primary language subtag 'zh' (Chinese) has a Scope 1557 of 'macrolanguage', while its enclosed language 'nan' (Min Nan 1558 Chinese) has a Scope of 'individual'. The special value 'und' 1559 (Undetermined) has a Scope of 'special'. The ISO 639-5 collection 1560 'gem' (Germanic languages) has a Scope of 'collection'. 1562 3.1.12. Comments Field 1564 The field 'Comments' contains additional information about the record 1565 and MAY appear more than once per record. The field-body MAY include 1566 the full range of Unicode characters and is not restricted to any 1567 particular script. This field MAY be inserted or changed via the 1568 registration process and no guarantee of stability is provided. 1570 The content of this field is not restricted, except by the need to 1571 register the information, the suitability of the request, and by 1572 reasonable practical size limitations. The primary reason for the 1573 'Comments' field is subtag identification: to help distinguish the 1574 subtag from others with which it might be confused as an aid to 1575 usage. Large amounts of information about the use, history, or 1576 general background of a subtag are frowned upon, as these generally 1577 belong in a registration request rather than in the registry. 1579 3.2. Language Subtag Reviewer 1581 The Language Subtag Reviewer moderates the ietf-languages mailing 1582 list, responds to requests for registration, and performs the other 1583 registry maintenance duties described in Section 3.3. Only the 1584 Language Subtag Reviewer is permitted to request IANA to change, 1585 update, or add records to the Language Subtag Registry. The Language 1586 Subtag Reviewer MAY delegate list moderation and other clerical 1587 duties as needed. 1589 The Language Subtag Reviewer is appointed by the IESG for an 1590 indefinite term, subject to removal or replacement at the IESG's 1591 discretion. The IESG will solicit nominees for the position (upon 1592 adoption of this document or upon a vacancy) and then solicit 1593 feedback on the nominees' qualifications. Qualified candidates 1594 should be familiar with BCP 47 and its requirements; be willing to 1595 fairly, responsively, and judiciously administer the registration 1596 process; and be suitably informed about the issues of language 1597 identification so that the reviewer can assess the claims and draw 1598 upon the contributions of language experts and subtag requesters. 1600 The subsequent performance or decisions of the Language Subtag 1601 Reviewer MAY be appealed to the IESG under the same rules as other 1602 IETF decisions (see [RFC2026]). The IESG can reverse or overturn the 1603 decisions of the Language Subtag Reviewer, provide guidance, or take 1604 other appropriate actions. 1606 3.3. Maintenance of the Registry 1608 Maintenance of the registry requires that, as codes are assigned or 1609 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1610 Subtag Reviewer MUST evaluate each change and determine the 1611 appropriate course of action according to the rules in this document. 1612 Such updates follow the registration process described in 1613 Section 3.5. Usually the Language Subtag Reviewer will start the 1614 process for the new or updated record by filling in the registration 1615 form and submitting it. If a change to one of these standards takes 1616 place and the Language Subtag Reviewer does not do this in a timely 1617 manner, then any interested party MAY submit the form. Thereafter 1618 the registration process continues normally. 1620 Note that some registrations affect other subtags--perhaps more than 1621 one--as when a region subtag is being deprecated in favor of a new 1622 value. The Language Subtag Reviewer is responsible for ensuring that 1623 any such changes are properly registered, with each change requiring 1624 its own registration form. 1626 The Language Subtag Reviewer MUST ensure that new subtags meet the 1627 requirements elsewhere in this document (and most especially in 1628 Section 3.4) or submit an appropriate registration form for an 1629 alternate subtag as described in that section. Each individual 1630 subtag affected by a change MUST be sent to the ietf-languages list 1631 with its own registration form and in a separate message. 1633 3.4. Stability of IANA Registry Entries 1635 The stability of entries and their meaning in the registry is 1636 critical to the long-term stability of language tags. The rules in 1637 this section guarantee that a specific language tag's meaning is 1638 stable over time and will not change. 1640 These rules specifically deal with how changes to codes (including 1641 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1642 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1643 Subtag Registry. Assignments to the IANA Language Subtag Registry 1644 MUST follow the following stability rules: 1646 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST 1647 NOT be changed and are guaranteed to be stable over time. 1649 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be 1650 added, altered, or removed via the registration process. These 1651 changes SHOULD be limited to changes necessary to mirror changes 1652 in one of the underlying standards (ISO 639, ISO 15924, ISO 1653 3166-1, or UN M.49) and typically alteration or removal of a 1654 Preferred-Value is limited specifically to region codes. 1656 3. Values in the 'Description' field MUST NOT be changed in a way 1657 that would invalidate any existing tags. The description MAY be 1658 broadened somewhat in scope, changed to add information, or 1659 adapted to the most common modern usage. For example, countries 1660 occasionally change their names; a historical example of this 1661 would be "Upper Volta" changing to "Burkina Faso". 1663 4. Values in the field 'Prefix' MAY be added to existing records of 1664 type 'variant' via the registration process, provided the 1665 'variant' already has at least one 'Prefix'. A 'Prefix' field 1666 SHALL NOT be registered for any 'variant' that has no existing 1667 'Prefix' field. If a prefix is added to a variant record, 1668 'Comment' fields MAY be used to explain different usages with 1669 the various prefixes. 1671 5. Values in the field 'Prefix' in records of type 'variant' MAY 1672 also be modified, so long as the modifications broaden the set 1673 of prefixes. That is, a prefix MAY be replaced by one of its 1674 own prefixes. For example, the prefix "en-US" could be replaced 1675 by "en", but not by the prefixes "en-Latn", "fr", or "en-US- 1676 boont". If one of those prefix values were needed, it would 1677 have to be separately registered. 1679 6. Values in the field 'Prefix' in records of type 'extlang' MUST 1680 NOT be added, modified, or removed. 1682 7. The field 'Prefix' MUST NOT be removed from any record in which 1683 it appears. This field SHOULD be included in the initial 1684 registration of any records of type 'variant' and MUST be 1685 included in any records of type 'extlang'. 1687 8. The field 'Comments' MAY be added, changed, modified, or removed 1688 via the registration process or any of the processes or 1689 considerations described in this section. 1691 9. The field 'Suppress-Script' MAY be added or removed via the 1692 registration process. 1694 10. The field 'Macrolanguage' MAY be added or removed via the 1695 registration process, but only in response to changes made by 1696 ISO 639. The Macrolanguage field appears whenever a language 1697 has a corresponding Macrolanguage in ISO 639. That is, the 1698 Macrolanguage fields in the registry exactly match those of ISO 1699 639. No other macrolanguage mappings will be considered for 1700 registration. 1702 11. The field 'Scope' MAY be added or removed from a primary or 1703 extended language subtag after initial registration, and it MAY 1704 be modified in order to match any changes made by ISO 639. 1705 Changes to the 'Scope' field MUST mirror changes made by ISO 1706 639. Note that primary or extended language subtags whose 1707 records do not contain a 'Scope' field (that is, most of them) 1708 are individual languages as described in Section 3.1.11. 1710 12. Primary and extended language subtags (other than independently 1711 registered values created using the registration process) are 1712 created according to the assignments of the various parts of ISO 1713 639, as follows: 1715 A. Codes assigned by ISO 639-1 that do not conflict with 1716 existing two-letter primary language subtags and which have 1717 no corresponding three-letter primary defined in the 1718 registry are entered into the IANA registry as new records 1719 of type 'language'. Note that languages given an ISO 639-1 1720 code cannot be given extended language subtags, even if 1721 encompassed by a macrolanguage. 1723 B. Codes assigned by ISO 639-3 or ISO 639-5 that do not 1724 conflict with existing three-letter primary language subtags 1725 and which do not have ISO 639-1 codes assigned (or expected 1726 to be assigned) are entered into the IANA registry as new 1727 records of type 'language'. Note that these two standards 1728 now comprise a superset of ISO 639-2 codes. Codes that have 1729 a defined "macrolanguage" mapping at the time of their 1730 registration MUST contain a "Macrolanguage" field. 1732 C. Codes assigned by ISO 639-3 MAY also be considered for an 1733 extended language subtag registration. Note that they MUST 1734 be assigned a primary language subtag record of type 1735 'language' even when an 'extlang' record is proposed. When 1736 considering extended language subtag assignment, these 1737 criteria apply: 1739 1. If a language has a macrolanguage mapping, and that 1740 macrolanguage has other encompassed languages that are 1741 assigned extended language subtags, then the new 1742 language SHOULD have an 'extlang' record assigned to it 1743 as well. For example, any language with a macrolanguage 1744 of 'zh' or 'ar'. 1746 2. 'Extlang' records SHOULD NOT be created for languages if 1747 other languages encompassed by the macrolanguage do not 1748 also include 'extlang' records. For example, if a new 1749 Serbo-Croatian ('sh') language were registered, it would 1750 not get an extlang record because other languages 1751 encompassed such as Serbian ('sr') do not include one in 1752 the registry. 1754 3. Sign languages SHOULD have an 'extlang' record with a 1755 'Prefix' of 'sgn'. 1757 4. 'Extlang' records MUST NOT be created for items already 1758 in the registry. Extended language subtags will only be 1759 considered at the time of initial registration. 1761 5. Extended language subtag records MUST include the fields 1762 'Prefix' and 'Preferred-Value' with field-values 1763 assigned as described in Section 2.2.2. 1765 D. Any other codes assigned by ISO 639-2 that do not conflict 1766 with existing three-letter primary or extended language 1767 subtags and which do not have ISO 639-1 two-letter codes 1768 assigned are entered into the IANA registry as new records 1769 of type 'language'. This type of registration is not 1770 supposed to occur in the future. 1772 13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict 1773 with existing subtags of the associated type and whose meaning 1774 is not the same as an existing subtag of the same type are 1775 entered into the IANA registry as new records. 1777 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are 1778 withdrawn by their respective maintenance or registration 1779 authority remain valid in language tags. A 'Deprecated' field 1780 containing the date of withdrawal MUST be added to the record. 1781 If a new record of the same type is added that represents a 1782 replacement value, then a 'Preferred-Value' field MAY also be 1783 added. The registration process MAY be used to add comments 1784 about the withdrawal of the code by the respective standard. 1786 For example: the region code 'TL' was assigned to the country 1787 'Timor-Leste', replacing the code 'TP' (which was assigned to 1788 'East Timor' when it was under administration by Portugal). 1789 The subtag 'TP' remains valid in language tags, but its 1790 record contains the a 'Preferred-Value' of 'TL' and its field 1791 'Deprecated' contains the date the new code was assigned 1792 ('2004-07-06'). 1794 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that 1795 conflict with existing subtags of the associated type, including 1796 subtags that are deprecated, MUST NOT be entered into the 1797 registry. The following additional considerations apply to 1798 subtag values that are reassigned: 1800 A. For ISO 639 codes, if the newly assigned code's meaning is 1801 not represented by a subtag in the IANA registry, the 1802 Language Subtag Reviewer, as described in Section 3.5, SHALL 1803 prepare a proposal for entering in the IANA registry as soon 1804 as practical a registered language subtag as an alternate 1805 value for the new code. The form of the registered language 1806 subtag will be at the discretion of the Language Subtag 1807 Reviewer and MUST conform to other restrictions on language 1808 subtags in this document. 1810 B. For all subtags whose meaning is derived from an external 1811 standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN 1812 M.49), if a new meaning is assigned to an existing code and 1813 the new meaning broadens the meaning of that code, then the 1814 meaning for the associated subtag MAY be changed to match. 1815 The meaning of a subtag MUST NOT be narrowed, however, as 1816 this can result in an unknown proportion of the existing 1817 uses of a subtag becoming invalid. Note: ISO 639 1818 registration authority (RA) has adopted a similar stability 1819 policy. 1821 C. For ISO 15924 codes, if the newly assigned code's meaning is 1822 not represented by a subtag in the IANA registry, the 1823 Language Subtag Reviewer, as described in Section 3.5, SHALL 1824 prepare a proposal for entering in the IANA registry as soon 1825 as practical a registered variant subtag as an alternate 1826 value for the new code. The form of the registered variant 1827 subtag will be at the discretion of the Language Subtag 1828 Reviewer and MUST conform to other restrictions on variant 1829 subtags in this document. 1831 D. For ISO 3166-1 codes, if the newly assigned code's meaning 1832 is associated with the same UN M.49 code as another 'region' 1833 subtag, then the existing region subtag remains as the 1834 preferred value for that region and no new entry is created. 1835 A comment MAY be added to the existing region subtag 1836 indicating the relationship to the new ISO 3166-1 code. 1838 E. For ISO 3166-1 codes, if the newly assigned code's meaning 1839 is associated with a UN M.49 code that is not represented by 1840 an existing region subtag, then the Language Subtag 1841 Reviewer, as described in Section 3.5, SHALL prepare a 1842 proposal for entering the appropriate UN M.49 country code 1843 as an entry in the IANA registry. 1845 F. For ISO 3166-1 codes, if there is no associated UN numeric 1846 code, then the Language Subtag Reviewer SHALL petition the 1847 UN to create one. If there is no response from the UN 1848 within ninety days of the request being sent, the Language 1849 Subtag Reviewer SHALL prepare a proposal for entering in the 1850 IANA registry as soon as practical a registered variant 1851 subtag as an alternate value for the new code. The form of 1852 the registered variant subtag will be at the discretion of 1853 the Language Subtag Reviewer and MUST conform to other 1854 restrictions on variant subtags in this document. This 1855 situation is very unlikely to ever occur. 1857 16. UN M.49 has codes for both countries and areas (such as '276' 1858 for Germany) and geographical regions and sub-regions (such as 1859 '150' for Europe). UN M.49 country or area codes for which 1860 there is no corresponding ISO 3166-1 code SHOULD NOT be 1861 registered, except as a surrogate for an ISO 3166-1 code that is 1862 blocked from registration by an existing subtag. If such a code 1863 becomes necessary, then the registration authority for ISO 1864 3166-1 SHOULD first be petitioned to assign a code to the 1865 region. If the petition for a code assignment by ISO 3166-1 is 1866 refused or not acted on in a timely manner, the registration 1867 process described in Section 3.5 MAY then be used to register 1868 the corresponding UN M.49 code. This way, UN M.49 codes remain 1869 available as the value of last resort in cases where ISO 3166-1 1870 reassigns a deprecated value in the registry. 1872 17. The redundant and grandfathered entries together form the 1873 complete list of tags registered under [RFC3066]. The redundant 1874 tags are those previously registered tags that can now be formed 1875 using the subtags defined in the registry. The grandfathered 1876 entries include those that can never be legal because they are 1877 'irregular' (that is, they do not match the 'langtag' production 1878 in Figure 1), are limited by rule (subtags such as 'nyn' and 1879 'min' look like the extlang production, but cannot be registered 1880 as extended language subtags), or their subtags are 1881 inappropriate for registration. All of the grandfathered tags 1882 are listed in either the 'regular' or the 'irregular' 1883 productions in the ABNF. Under [RFC4646] it was possible for 1884 grandfathered tags to become redundant. However, all of the 1885 tags for which this was possible became redundant before this 1886 document was produced. So the set of redundant and 1887 grandfathered tags is now permanent and immutable: new entries 1888 of either type MUST NOT be added and existing entries MUST NOT 1889 be removed. The decision-making process about which tags were 1890 initially grandfathered and which were made redundant is 1891 described in [RFC4645]. 1893 Many of the grandfathered tags are deprecated, indeed, they were 1894 deprecated even before [RFC4646]. For example, the tag "art- 1895 lojban" was deprecated in favor of the primary language subtag 1896 'jbo'. These tags could have been made 'redundant' by 1897 registering some of their subtags as 'variants'. The 'variant- 1898 like' subtags in the grandfathered registrations SHALL NOT be 1899 registered in the future, even with a similar or identical 1900 meaning. 1902 3.5. Registration Procedure for Subtags 1904 The procedure given here MUST be used by anyone who wants to use a 1905 subtag not currently in the IANA Language Subtag Registry or who 1906 wishes to add, modify, update, or remove information in existing 1907 records as permitted by this document. 1909 Only subtags of type 'language' and 'variant' will be considered for 1910 independent registration of new subtags. Subtags needed for 1911 stability and subtags necessary to keep the registry synchronized 1912 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1913 defined by this document also use this process, as described in 1914 Section 3.3 and subject to stability provisions as described in 1915 Section 3.4. 1917 Registration requests are accepted relating to information in the 1918 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value', 1919 or 'Suppress-Script' fields in a subtag's record as described in 1920 Section 3.4. Changes to all other fields in the IANA registry are 1921 NOT permitted. 1923 Registering a new subtag or requesting modifications to an existing 1924 tag or subtag starts with the requester filling out the registration 1925 form reproduced below. Note that each response is not limited in 1926 size so that the request can adequately describe the registration. 1927 The fields in the "Record Requested" section SHOULD follow the 1928 requirements in Section 3.1. 1930 LANGUAGE SUBTAG REGISTRATION FORM 1931 1. Name of requester: 1932 2. E-mail address of requester: 1933 3. Record Requested: 1935 Type: 1936 Subtag: 1937 Description: 1938 Prefix: 1939 Preferred-Value: 1940 Deprecated: 1941 Suppress-Script: 1942 Macrolanguage: 1943 Comments: 1945 4. Intended meaning of the subtag: 1946 5. Reference to published description 1947 of the language (book or article): 1948 6. Any other relevant information: 1950 Figure 5: The Language Subtag Registration Form 1952 Examples of completed registration forms can be found in Appendix C. 1953 A complete list of approved registration forms is online at 1954 http://www.iana.org/assignments/lang-subtags-templates/. 1956 The subtag registration form MUST be sent to 1957 . Registration requests receive a two-week 1958 review period before being approved and submitted to IANA for 1959 inclusion in the registry. If modifications are made to the request 1960 during the course of the registration process (such as corrections to 1961 meet the requirements in Section 3.1 or to make the 'Description' 1962 fields unique for the given record type) the modified form MUST also 1963 be sent to at least one week prior to 1964 submission to IANA. 1966 The ietf-languages list is an open list and can be joined by sending 1967 a request to . The list can be 1968 hosted by IANA or by any third party at the request of IESG. 1970 Before forwarding any registration to IANA, the Language Subtag 1971 Reviewer MUST ensure that all requirements in this document are met. 1972 This includes ensuring that values in the 'Subtag' field match case 1973 according to the description in Section 3.1.4 and that 'Description' 1974 fields are unique for the given record type as described in 1975 Section 3.1.5. The Reviewer MUST also ensure that an appropriate 1976 File-Date record is included in the request, to assist IANA when 1977 updating the registry (see Section 5.1). 1979 Some fields in both the registration form as well as the registry 1980 record itself permit the use of non-ASCII characters. Registration 1981 requests SHOULD use the UTF-8 encoding for consistency and clarity. 1982 However, since some mail clients do not support this encoding, other 1983 encodings MAY be used for the registration request. The Language 1984 Subtag Reviewer is responsible for ensuring that the proper Unicode 1985 characters appear in both the archived request form and the registry 1986 record. In the case of a transcription or encoding error by IANA, 1987 the Language Subtag Reviewer will request that the registry be 1988 repaired, providing any necessary information to assist IANA. 1990 Extended language subtags (type 'extlang'), by definition, are always 1991 encompassed by another language. All records of type 'extlang' MUST, 1992 therefore, contain a 'Prefix' field at the time of registration. 1993 This Prefix field can never be altered or removed and requests to do 1994 so MUST be rejected. 1996 Variant subtags are usually registered for use with a particular 1997 range of language tags and variant subtags based on the terminology 1998 of the language to which they are apply are encouraged. For example, 1999 the subtag 'rozaj' (Resian) is intended for use with language tags 2000 that start with the primary language subtag "sl" (Slovenian), since 2001 Resian is a dialect of Slovenian. Thus, the subtag 'rozaj' would be 2002 appropriate in tags such as "sl-Latn-rozaj" or "sl-IT-rozaj". This 2003 information is stored in the 'Prefix' field in the registry. Variant 2004 registration requests SHOULD include at least one 'Prefix' field in 2005 the registration form. 2007 Requests to assign an additional record of a given type with an 2008 existing subtag value MUST be rejected. For example, the variant 2009 subtag 'rozaj' already exists in the registry, so adding a second 2010 record of type 'variant' with the subtag 'rozaj' is prohibited. 2012 The 'Prefix' field for a given registered variant subtag exists in 2013 the IANA registry as a guide to usage. Additional 'Prefix' fields 2014 MAY be added by filing an additional registration form. In that 2015 form, the "Any other relevant information:" field MUST indicate that 2016 it is the addition of a prefix. 2018 Requests to add a 'Prefix' field to a variant subtag that imply a 2019 different semantic meaning SHOULD be rejected. For example, a 2020 request to add the prefix "de" to the subtag '1994' so that the tag 2021 "de-1994" represented some German dialect or orthographic form would 2022 be rejected. The '1994' subtag represents a particular Slovenian 2023 orthography and the additional registration would change or blur the 2024 semantic meaning assigned to the subtag. A separate subtag SHOULD be 2025 proposed instead. 2027 Requests to add a 'Prefix' to a variant subtag that has no current 2028 'Prefix' field MUST be rejected. Variants are registered with no 2029 prefix because they are potentially useful with many or even all 2030 languages. Adding one or more 'Prefix' fields would be potentially 2031 harmful to the use of the variant, since it dramatically reduces the 2032 scope of the subtag (which is not allowed under the stability rules 2033 (Section 3.4), as opposed to broadening the scope of the subtag, 2034 which is what the addition of a 'Prefix' normally does. An example 2035 of such a "no-prefix" variant is the subtag 'fonipa', which 2036 represents the International Phonetic Alphabet, a scheme which can be 2037 used to transcribe many languages. 2039 The 'Description' fields provided in the request MUST contain at 2040 least one description written or transcribed into the Latin script; 2041 the request MAY also include additional 'Description' fields in any 2042 script or language. The 'Description' field is used for 2043 identification purposes and doesn't necessarily represent the actual 2044 native name of the language or variation. It also doesn't have to be 2045 in any particular language, but SHOULD be both suitable and 2046 sufficient to identify the item in the record. The Language Subtag 2047 Reviewer will check and edit any proposed 'Description' fields so as 2048 to ensure uniqueness and prevent collisions with 'Description' fields 2049 in other records of the same type. If this occurs in an independent 2050 registration request, the Language Subtag Reviewer MUST resubmit the 2051 record to ietf-languages, treating it as a modification of a request 2052 due to discussion, as described in Section 3.5, unless the request's 2053 sole purpose is to introduce a duplicate 'Description' field, in 2054 which case the request SHALL be rejected. 2056 While the 'Description' field itself is not guaranteed to be stable 2057 and errata corrections MAY be undertaken from time to time, attempts 2058 to provide translations or transcriptions of entries in the registry 2059 itself will probably be frowned upon by the community or rejected 2060 outright, as changes of this nature have an impact on the provisions 2061 in Section 3.4. 2063 Soon after the two-week review period has passed, the Language Subtag 2064 Reviewer MUST take one of the following actions: 2066 o Explicitly accept the request and forward the form containing the 2067 record to be inserted or modified to iana@iana.org according to 2068 the procedure described in Section 3.3. 2070 o Explicitly reject the request because of significant objections 2071 raised on the list or due to problems with constraints in this 2072 document (which MUST be explicitly cited). 2074 o Extend the review period by granting an additional two-week 2075 increment to permit further discussion. After each two-week 2076 increment, the Language Subtag Reviewer MUST indicate on the list 2077 whether the registration has been accepted, rejected, or extended. 2079 Note that the Language Subtag Reviewer MAY raise objections on the 2080 list if he or she so desires. The important thing is that the 2081 objection MUST be made publicly. 2083 Sometimes the request needs to be modified as a result of discussion 2084 during the review period or due to requirements in this document. 2085 The applicant, Language Subtag Reviewer, or others MAY submit a 2086 modified version of the completed registration form, which will be 2087 considered in lieu of the original request with the explicit approval 2088 of the applicant. Such changes do not restart the two-week 2089 discussion period, although an application containing the final 2090 record submitted to IANA MUST appear on the list at least one week 2091 prior to the Language Subtag Reviewer forwarding the record to IANA. 2092 The applicant MAY modify a rejected application with more appropriate 2093 or additional information and submit it again; this starts a new two- 2094 week comment period. 2096 Registrations initiated due to the provisions of Section 3.3 or 2097 Section 3.4 SHALL NOT be rejected altogether (since they have to 2098 ultimately appear in the registry) and SHOULD be completed as quickly 2099 as possible. The review process allows list members to comment on 2100 the specific information in the form and the record it contains and 2101 thus help ensure that it is correct and consistent. The Language 2102 Subtag Reviewer MAY reject a specific version of the form, but MUST 2103 propose a suitable replacement, extending the review period as 2104 described above, until the form is in a format worthy of reviewer's 2105 approval and meets with rough consensus of the list. 2107 Decisions made by the Language Subtag Reviewer MAY be appealed to the 2108 IESG [RFC2028] under the same rules as other IETF decisions 2109 [RFC2026]. This includes a decision to extend the review period or 2110 the failure to announce a decision in a clear and timely manner. 2112 The approved records appear in the Language Subtag Registry. The 2113 approved registration forms are available online under 2114 http://www.iana.org/assignments/lang-subtags-templates/. 2116 Updates or changes to existing records follow the same procedure as 2117 new registrations. The Language Subtag Reviewer decides whether 2118 there is consensus to update the registration following the two week 2119 review period; normally, objections by the original registrant will 2120 carry extra weight in forming such a consensus. 2122 Registrations are permanent and stable. Once registered, subtags 2123 will not be removed from the registry and will remain a valid way in 2124 which to specify a specific language or variant. 2126 Note: The purpose of the "Reference to published description" section 2127 in the registration form is to aid in verifying whether a language is 2128 registered or what language or language variation a particular subtag 2129 refers to. In most cases, reference to an authoritative grammar or 2130 dictionary of that language will be useful; in cases where no such 2131 work exists, other well-known works describing that language or in 2132 that language MAY be appropriate. The Language Subtag Reviewer 2133 decides what constitutes "good enough" reference material. This 2134 requirement is not intended to exclude particular languages or 2135 dialects due to the size of the speaker population or lack of a 2136 standardized orthography. Minority languages will be considered 2137 equally on their own merits. 2139 3.6. Possibilities for Registration 2141 Possibilities for registration of subtags or information about 2142 subtags include: 2144 o Primary language subtags for languages not listed in ISO 639 that 2145 are not variants of any listed or registered language MAY be 2146 registered. At the time this document was created, there were no 2147 examples of this form of subtag. Before attempting to register a 2148 language subtag, there MUST be an attempt to register the language 2149 with ISO 639. Subtags MUST NOT be registered for languages 2150 defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, 2151 or that are under consideration by the ISO 639 registration 2152 authorities, or that have never been attempted for registration 2153 with those authorities. If ISO 639 has previously rejected a 2154 language for registration, it is reasonable to assume that there 2155 must be additional, very compelling evidence of need before it 2156 will be registered as a primary language subtag in the IANA 2157 registry (to the extent that it is very unlikely that any subtags 2158 will be registered of this type). 2160 o Dialect or other divisions or variations within a language, its 2161 orthography, writing system, regional or historical usage, 2162 transliteration or other transformation, or distinguishing 2163 variation MAY be registered as variant subtags. An example is the 2164 'rozaj' subtag (the Resian dialect of Slovenian). 2166 o The addition or maintenance of fields (generally of an 2167 informational nature) in Tag or Subtag records as described in 2168 Section 3.1 and subject to the stability provisions in 2169 Section 3.4. This includes Description, Comments, Deprecated and 2170 Preferred-Value fields for obsolete or withdrawn codes, or the 2171 addition of Suppress-Script or Macrolanguage fields to primary 2172 language subtags, as well as other changes permitted by this 2173 document, such as the addition of an appropriate Prefix field to a 2174 variant subtag. 2176 o The addition of records and related field value changes necessary 2177 to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and 2178 UN M.49 as described in Section 3.4. 2180 Subtags proposed for registration that would cause all or part of a 2181 grandfathered tag to become redundant but whose meaning conflicts 2182 with or alters the meaning of the grandfathered tag MUST be rejected. 2184 This document leaves the decision on what subtags or changes to 2185 subtags are appropriate (or not) to the registration process 2186 described in Section 3.5. 2188 Note: four-character primary language subtags are reserved to allow 2189 for the possibility of alpha4 codes in some future addition to the 2190 ISO 639 family of standards. 2192 ISO 639 defines a registration authority for additions to and changes 2193 in the list of languages in ISO 639. This agency is: 2195 International Information Centre for Terminology (Infoterm) 2196 Aichholzgasse 6/12, AT-1120 2197 Wien, Austria 2198 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 2200 ISO 639-2 defines a registration authority for additions to and 2201 changes in the list of languages in ISO 639-2. This agency is: 2203 Library of Congress 2204 Network Development and MARC Standards Office 2205 Washington, D.C. 20540 USA 2206 Phone: +1 202 707 6237 Fax: +1 202 707 0115 2207 URL: http://www.loc.gov/standards/iso639-2 2209 ISO 639-3 defines a registration authority for additions to and 2210 changes in the list of languages in ISO 639-3. This agency is: 2212 SIL International 2213 ISO 639-3 Registrar 2214 7500 W. Camp Wisdom Rd. 2215 Dallas, TX 75236 USA 2216 Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 2217 Email: iso639-3@sil.org 2218 URL: http://www.sil.org/iso639-3 2220 ISO 639-5 defines a registration authority for additions to and 2221 changes in the list of languages in ISO 639-5. This agency is the 2222 same as for ISO 639-2 and is: 2224 Library of Congress 2225 Network Development and MARC Standards Office 2226 Washington, D.C. 20540 USA 2227 Phone: +1 202 707 6237 Fax: +1 202 707 0115 2228 URL: http://www.loc.gov/standards/iso639-5 2230 The maintenance agency for ISO 3166-1 (country codes) is: 2232 ISO 3166 Maintenance Agency 2233 c/o International Organization for Standardization 2234 Case postale 56 2235 CH-1211 Geneva 20 Switzerland 2236 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 2237 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 2239 The registration authority for ISO 15924 (script codes) is: 2241 Unicode Consortium 2242 Box 391476 2243 Mountain View, CA 94039-1476, USA 2244 URL: http://www.unicode.org/iso15924 2246 The Statistics Division of the United Nations Secretariat maintains 2247 the Standard Country or Area Codes for Statistical Use and can be 2248 reached at: 2250 Statistical Services Branch 2251 Statistics Division 2252 United Nations, Room DC2-1620 2253 New York, NY 10017, USA 2255 Fax: +1-212-963-0623 2256 E-mail: statistics@un.org 2257 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 2259 3.7. Extensions and the Extensions Registry 2261 Extension subtags are those introduced by single-character subtags 2262 ("singletons") other than 'x'. They are reserved for the generation 2263 of identifiers that contain a language component and are compatible 2264 with applications that understand language tags. 2266 The structure and form of extensions are defined by this document so 2267 that implementations can be created that are forward compatible with 2268 applications that might be created using singletons in the future. 2269 In addition, defining a mechanism for maintaining singletons will 2270 lend stability to this document by reducing the likely need for 2271 future revisions or updates. 2273 Single-character subtags are assigned by IANA using the "IETF 2274 Consensus" policy defined by [RFC2434]. This policy requires the 2275 development of an RFC, which SHALL define the name, purpose, 2276 processes, and procedures for maintaining the subtags. The 2277 maintaining or registering authority, including name, contact email, 2278 discussion list email, and URL location of the registry, MUST be 2279 indicated clearly in the RFC. The RFC MUST specify or include each 2280 of the following: 2282 o The specification MUST reference the specific version or revision 2283 of this document that governs its creation and MUST reference this 2284 section of this document. 2286 o The specification and all subtags defined by the specification 2287 MUST follow the ABNF and other rules for the formation of tags and 2288 subtags as defined in this document. In particular, it MUST 2289 specify that case is not significant and that subtags MUST NOT 2290 exceed eight characters in length. 2292 o The specification MUST specify a canonical representation. 2294 o The specification of valid subtags MUST be available over the 2295 Internet and at no cost. 2297 o The specification MUST be in the public domain or available via a 2298 royalty-free license acceptable to the IETF and specified in the 2299 RFC. 2301 o The specification MUST be versioned, and each version of the 2302 specification MUST be numbered, dated, and stable. 2304 o The specification MUST be stable. That is, extension subtags, 2305 once defined by a specification, MUST NOT be retracted or change 2306 in meaning in any substantial way. 2308 o The specification MUST include in a separate section the 2309 registration form reproduced in this section (below) to be used in 2310 registering the extension upon publication as an RFC. 2312 o IANA MUST be informed of changes to the contact information and 2313 URL for the specification. 2315 IANA will maintain a registry of allocated single-character 2316 (singleton) subtags. This registry MUST use the record-jar format 2317 described by the ABNF in Section 3.1. Upon publication of an 2318 extension as an RFC, the maintaining authority defined in the RFC 2319 MUST forward this registration form to iesg@ietf.org, who MUST 2320 forward the request to iana@iana.org. The maintaining authority of 2321 the extension MUST maintain the accuracy of the record by sending an 2322 updated full copy of the record to iana@iana.org with the subject 2323 line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only 2324 the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY 2325 be modified in these updates. 2327 Failure to maintain this record, maintain the corresponding registry, 2328 or meet other conditions imposed by this section of this document MAY 2329 be appealed to the IESG [RFC2028] under the same rules as other IETF 2330 decisions (see [RFC2026]) and MAY result in the authority to maintain 2331 the extension being withdrawn or reassigned by the IESG. 2333 %% 2334 Identifier: 2335 Description: 2336 Comments: 2337 Added: 2338 RFC: 2339 Authority: 2340 Contact_Email: 2341 Mailing_List: 2342 URL: 2343 %% 2345 Figure 6: Format of Records in the Language Tag Extensions Registry 2347 'Identifier' contains the single-character subtag (singleton) 2348 assigned to the extension. The Internet-Draft submitted to define 2349 the extension SHOULD specify which letter or digit to use, although 2350 the IESG MAY change the assignment when approving the RFC. 2352 'Description' contains the name and description of the extension. 2354 'Comments' is an OPTIONAL field and MAY contain a broader description 2355 of the extension. 2357 'Added' contains the date the extension's RFC was published in the 2358 "full-date" format specified in [RFC3339]. For example: 2004-06-28 2359 represents June 28, 2004, in the Gregorian calendar. 2361 'RFC' contains the RFC number assigned to the extension. 2363 'Authority' contains the name of the maintaining authority for the 2364 extension. 2366 'Contact_Email' contains the email address used to contact the 2367 maintaining authority. 2369 'Mailing_List' contains the URL or subscription email address of the 2370 mailing list used by the maintaining authority. 2372 'URL' contains the URL of the registry for this extension. 2374 The determination of whether an Internet-Draft meets the above 2375 conditions and the decision to grant or withhold such authority rests 2376 solely with the IESG and is subject to the normal review and appeals 2377 process associated with the RFC process. 2379 Extension authors are strongly cautioned that many (including most 2380 well-formed) processors will be unaware of any special relationships 2381 or meaning inherent in the order of extension subtags. Extension 2382 authors SHOULD avoid subtag relationships or canonicalization 2383 mechanisms that interfere with matching or with length restrictions 2384 that sometimes exist in common protocols where the extension is used. 2385 In particular, applications MAY truncate the subtags in doing 2386 matching or in fitting into limited lengths, so it is RECOMMENDED 2387 that the most significant information be in the most significant 2388 (left-most) subtags and that the specification gracefully handle 2389 truncated subtags. 2391 When a language tag is to be used in a specific, known, protocol, it 2392 is RECOMMENDED that the language tag not contain extensions not 2393 supported by that protocol. In addition, note that some protocols 2394 MAY impose upper limits on the length of the strings used to store or 2395 transport the language tag. 2397 3.8. Update of the Language Subtag Registry 2399 Upon adoption of this document the IANA Language Subtag Registry will 2400 need an update so that it contains the complete set of subtags valid 2401 in a language tag. This collection of subtags, along with a 2402 description of the process used to create it, is described by 2403 [registry-update]. IANA will publish the updated version of the 2404 registry described by this document using the instructions and 2405 content of [registry-update]. Once published by IANA, the 2406 maintenance procedures, rules, and registration processes described 2407 in this document will be available for new registrations or updates. 2409 Registrations that are in process under the rules defined in 2410 [RFC4646] when this document is adopted MUST be completed under the 2411 rules contained in this document. 2413 4. Formation and Processing of Language Tags 2415 This section addresses how to use the information in the registry 2416 with the tag syntax to choose, form, and process language tags. 2418 4.1. Choice of Language Tag 2420 The guiding principle in forming language tags is to "tag content 2421 wisely." Sometimes there is a choice between several possible tags 2422 for the same content. The choice of which tag to use depends on the 2423 content and application in question and some amount of judgment might 2424 be necessary when selecting a tag. 2426 Interoperability is best served when the same language tag is used 2427 consistently to represent the same language. If an application has 2428 requirements that make the rules here inapplicable, then that 2429 application risks damaging interoperability. It is strongly 2430 RECOMMENDED that users not define their own rules for language tag 2431 choice. 2433 Standards, protocols, and applications that reference this document 2434 normatively but apply different rules to the ones given in this 2435 section MUST specify how language tag selection varies from the 2436 guidelines given here. 2438 To ensure consistent backward compatibility, this document contains 2439 several provisions to account for potential instability in the 2440 standards used to define the subtags that make up language tags. 2441 These provisions mean that no valid language tag can become invalid, 2442 nor will a language tag have a narrower scope in the future (it may 2443 have a broader scope). The most appropriate language tag for a given 2444 application or content item might evolve over time, but once applied, 2445 the tag itself cannot become invalid or have its meaning wholly 2446 change. 2448 A subtag SHOULD only be used when it adds useful distinguishing 2449 information to the tag. Extraneous subtags interfere with the 2450 meaning, understanding, and processing of language tags. In 2451 particular, users and implementations SHOULD follow the 'Prefix' and 2452 'Suppress-Script' fields in the registry (defined in Section 3.1): 2453 these fields provide guidance on when specific additional subtags 2454 SHOULD be used or avoided in a language tag. 2456 The choice of subtags used to form a language tag SHOULD follow these 2457 guidelines: 2459 1. Use as precise a tag as possible, but no more specific than is 2460 justified. Avoid using subtags that are not important for 2461 distinguishing content in an application. 2463 * For example, 'de' might suffice for tagging an email written 2464 in German, while "de-CH-1996" is probably unnecessarily 2465 precise for such a task. 2467 * Note that some subtag sequences might not represent the 2468 language a casual user might expect, especially if when 2469 relying on the subtag's description in the registry. For 2470 example, the Swiss German (Schweizerdeutsch) language is 2471 represented by "gsw-CH" and not by "de-CH". This latter tag 2472 represents German ('de') as used in Switzerland ('CH'), also 2473 known as Swiss High German (Schweizer Hochdeutsch). Both are 2474 real languages and distinguishing between them could be 2475 important to an application. 2477 2. The script subtag SHOULD NOT be used to form language tags unless 2478 the script adds some distinguishing information to the tag. 2479 Script subtags were first formally defined in BCP 47 by 2480 [RFC4646]. Their use can affect matching and subtag 2481 identification for implementations of previous versions of BCP 47 2482 (i.e. [RFC1766] or [RFC3066]), as these subtags appear between 2483 the primary language and region subtags. Some applications can 2484 benefit from the use of script subtags in language tags, as long 2485 as the use is consistent for a given context. Script subtags are 2486 never appropriate for unwritten content (such as audio 2487 recordings). The field 'Suppress-Script' in the primary or 2488 extended language record in the registry indicates script subtags 2489 that do not add distinguishing information for most applications; 2490 this field defines when users SHOULD NOT include a script subtag 2491 with a particular primary language subtag. 2493 For example, if an implementation selects content using Basic 2494 Filtering [RFC4647] (originally described in Section 2.5 of 2495 [RFC3066]) and the user requested the language range "en-US", 2496 content labeled "en-Latn-US" will not match the request and thus 2497 not be selected. Therefore, it is important to know when script 2498 subtags will customarily be used and when they ought not be used. 2500 For example: 2502 * The subtag 'Latn' should not be used with the primary language 2503 'en' because nearly all English documents are written in the 2504 Latin script and it adds no distinguishing information. 2505 However, if a document were written in English mixing Latin 2506 script with another script such as Braille ('Brai'), then it 2507 might be appropriate to choose to indicate both scripts to aid 2508 in content selection, such as the application of a style 2509 sheet. 2511 * When labeling content that is unwritten (such as a recording 2512 of human speech), the script subtag should not be used, even 2513 if the language is customarily written in several scripts. 2514 Thus the subtitles to a movie might use the tag "uz-Arab" 2515 (Uzbek, Arabic script), but the audio track for the same 2516 language would be tagged simply "uz". (The tag "uz-Zxxx" 2517 could also be used where content is not written, as the subtag 2518 'Zxxx' represents the "Code for unwritten documents".) 2520 3. If a tag or subtag has a 'Preferred-Value' field in its registry 2521 entry, then the value of that field SHOULD be used to form the 2522 language tag in preference to the tag or subtag in which the 2523 preferred value appears. 2525 * For example, use 'jbo' for Lojban in preference to the 2526 grandfathered tag "art-lojban". 2528 4. Use subtags or sequences of subtags for individual languages in 2529 preference to subtags for language collections. A "language 2530 collection" is a group of languages that are descended from a 2531 common ancestor, are spoken in the same geographical area, or are 2532 otherwise related. Certain language collections are assigned 2533 codes by [ISO639-5] (and some of these [ISO639-5] codes are also 2534 defined as collections in [ISO639-2]). These codes are included 2535 as primary language subtags in the registry. Subtags for a 2536 language collection in the registry have a 'Scope' field with a 2537 value of 'collection'. A subtag for a language collection is 2538 always preferred to less-specific alternatives such as 'mul' and 2539 'und' (see below) and a subtag representing a language collection 2540 MAY be used when more specific language information is not 2541 available. However, most users and implementations do not know 2542 there is a relationship between the collection and its individual 2543 languages. In addition, the relationship between the individual 2544 languages in the collection is not well defined; in particular, 2545 the languages are usually not mutually intelligible. Since the 2546 subtags are different, a request for the collection will 2547 typically only produce items tagged with the collection's subtag, 2548 not items tagged with subtags for the individual languages 2549 contained in the collection. 2551 For example: 2553 1. Collections are interpreted inclusively, so the subtag 'gem' 2554 (Germanic langauges) could, but should not, be used with 2555 content that would be better tagged with "en" (English), "de" 2556 (German), or "gsw" (Swiss German, Alemannic). While 'gem' 2557 collects all of these (and other) languages, most 2558 implementations will not match 'gem' to the individual 2559 languages; thus using the subtag will not produce the desired 2560 result. 2562 5. [ISO639-2] has defined several codes included in the subtag 2563 registry that require additional care when choosing language 2564 tags. In most of these cases, where omitting the language tag is 2565 permitted, such omission is preferable to using these codes. 2566 Language tags SHOULD NOT incorporate these subtags as a prefix, 2567 unless the additional information conveys some value to the 2568 application. 2570 * The 'mul' (Multiple) primary language subtag identifies 2571 content in multiple languages. This subtag SHOULD NOT be used 2572 when a list of languages or individual tags for each content 2573 element can be used instead. For example, the 'Content- 2574 Language' header ([RFC3282]) allows a list of languages to be 2575 used, not just a single language tag. 2577 * The 'und' (Undetermined) primary language subtag identifies 2578 linguistic content whose language is not determined. This 2579 subtag SHOULD NOT be used unless a language tag is required 2580 and language information is not available or cannot be 2581 determined. Omitting the language tag (where permitted) is 2582 preferred. The 'und' subtag MAY be useful for protocols that 2583 require a language tag to be provided or where a primary 2584 language subtag is required (such as in "und-Latn"). The 2585 'und' subtag MAY also be useful when matching language tags in 2586 certain situations. 2588 * The 'zxx' (Non-Linguistic, Not Applicable) primary language 2589 subtag identifies content for which a language classification 2590 is inappropriate or does not apply. Some examples might 2591 include instrumental or electronic music; sound recordings 2592 consisting of nonverbal sounds; audiovisual materials with no 2593 narration, dialog, printed titles, or subtitles; machine- 2594 readable data files consisting of machine languages or 2595 character codes; or programming source code. 2597 * The 'mis' (Uncoded) primary language subtag identifies content 2598 whose language is known but which does not currently have a 2599 corresponding subtag. This subtag SHOULD NOT be used. 2600 Because the addition of other codes in the future can render 2601 its application invalid, it is inherently unstable and hence 2602 incompatible with the stability goals of BCP 47. It is always 2603 preferable to use other subtags: either 'und' or (with prior 2604 agreement) private use subtags. 2606 6. Use variant subtags sparingly and in the correct order. Most 2607 variant subtags have one or more 'Prefix' fields in the registry 2608 that express the list of subtags that they are appropriate with. 2609 Variants SHOULD only be used with subtags that appear in one of 2610 these 'Prefix' fields. If a variant lists a second variant in 2611 one of its 'Prefix' fields, the first variant SHOULD appear 2612 directly after the second variant in any language tag where both 2613 occur. General purpose variants (those with no 'Prefix' fields 2614 at all) SHOULD appear after any other variant subtags. Order any 2615 remaining variants by placing the most significant subtag first. 2616 If none of the subtags is more significant or no relationship can 2617 be determined, alphabetize the subtags. Because variants are 2618 very specialized, using many of them together generally makes the 2619 tag so narrow as to override the additional precision gained. 2620 Putting the subtags into another order interferes with 2621 interoperability, as well as the overall interpretation of the 2622 tag. 2624 A. For example, the tag "en-scottish-fonipa" (English, Scottish 2625 dialect, IPA phonetic transcription) is correctly ordered 2626 because 'scottish' has a 'Prefix' of "en", while 'fonipa' has 2627 no 'Prefix' field. 2629 B. For example, the tag "sl-IT-rozaj-biske-1994" is correctly 2630 ordered: 'rozaj' lists "sl" as its sole 'Prefix'; 'biske' 2631 lists "sl-rozaj" as its sole Prefix. The subtag '1994' has 2632 several prefixes, including "sl-rozaj". However, it follows 2633 both 'rozaj' and 'biske' because one of its 'Prefix' fields 2634 is "sl-rozaj-biske". 2636 7. The grandfathered tag "i-default" (Default Language) was 2637 originally registered according to [RFC1766] to meet the needs of 2638 [RFC2277]. It is used to indicate not a specific language, but 2639 rather, it identifies the condition or content used where the 2640 language preferences of the user cannot be established. It 2641 SHOULD NOT be used except as a means of labeling the default 2642 content for applications or protocols that require default 2643 language content to be labeled with that specific tag. It MAY 2644 also be used by an application or protocol to identify when the 2645 default language content is being returned. 2647 4.1.1. Tagging Encompassed Languages 2649 Some primary language records in the registry have a "Macrolanguage" 2650 field (Section 3.1.10) that contains a mapping from each "encompassed 2651 language" to its macrolanguage. The Macrolanguage mapping doesn't 2652 define what the relationship between the encompassed language and its 2653 macrolanguage is, nor does it define how languages encompassed by the 2654 same macrolanguage are related to each other. Two different 2655 languages encompassed by the same macrolanguage may differ from one 2656 another more than say, French and Spanish do. 2658 A few specific macrolanguages, such as Chinese ('zh') and Arabic 2659 ('ar'), are handled differently. See Section 4.1.2. 2661 The more specific encompassed language subtag SHOULD be used to form 2662 the language tag, although either the macrolanguage's primary 2663 language subtag or the encompassed language's subtag MAY be used. 2664 This means, for example, tagging Plains Cree with 'crk' rather than 2665 'cre' (Cree); and so forth. 2667 Each macrolanguage subtag's scope, by definition, includes all of its 2668 encompassed languages. Since the relationship between encompassed 2669 languages varies, users cannot assume that the macrolanguage subtag 2670 means any particular encompassed language nor that any given pair of 2671 encompassed languages are mutually intelligible or otherwise 2672 interchangeable. 2674 Applications MAY use macrolanguage information to improve matching or 2675 language negotiation. For example, the information that 'sr' 2676 (Serbian) and 'hr' (Croatian) share a macrolanguage expresses a 2677 closer relation between those languages than between, say, 'sr' 2678 (Serbian) and 'ma' (Macedonian). However, this relationship is not 2679 guaranteed nor is it exclusive. For example, Romanian ('ro') and 2680 Moldavian ('mo') do not share a macrolanguage, but are far more 2681 closely related to each other than Cantonese ('yue') and Wu ('wuu') , 2682 which do share a macrolanguage. 2684 4.1.2. Using Extended Language Subtags 2686 To accommodate language tag forms used prior to the adoption of this 2687 document, language tags provide a special compatibility mechanism: 2688 the extended language subtag. Selected languages have been provided 2689 with both primary and extended language subtags. These include 2690 macrolanguages, such as Malay ('ms') and Uzbek ('uz'), that have a 2691 specific dominant variety that is generally synonymous with the 2692 macrolanguage. Other languages, such as the Chinese ('zh') and 2693 Arabic ('ar') macrolanguages and the various sign languages ('sgn'), 2694 have traditionally used their primary language subtag, possibly 2695 coupled with various region subtags or as part of a registered 2696 grandfathered tag, to indicate the language. 2698 With the adoption of this document, specific ISO 639-3 subtags became 2699 available to identify the languages contained within these diverse 2700 language families or groupings. This presents a choice of language 2701 tags where previously none existed: 2703 o Each encompassed language's subtag SHOULD be used as the primary 2704 language subtag. For example, a document in Mandarin Chinese 2705 would be tagged "cmn" (the subtag for Mandarin Chinese) in 2706 preference to "zh" (Chinese). 2708 o If compatibility is desired or needed, the encompassed subtag MAY 2709 be used as an extended language subtag. For example, a document 2710 in Mandarin Chinese could be tagged "zh-cmn" instead of either 2711 "cmn" or "zh". 2713 o The macrolanguage or prefixing subtag MAY still be used to form 2714 the tag instead of the more specific encompassed language subtag. 2715 That is, tags such as "zh-HK" or "sgn-RU" are still valid. 2717 Chinese ('zh') provides a useful illustration of this. In the past, 2718 various content has used tags beginning with the 'zh' subtag, with 2719 application specific meaning being associated with region codes, 2720 private-use sequences, or grandfathered registered values. This is 2721 because historically only the macrolanguage subtag 'zh' was available 2722 for forming language tags. However, the languages encompassed by the 2723 Chinese subtag 'zh' are, in the main, not mutually intelligible when 2724 spoken, and the written forms of these languages also show wide 2725 variation in form and usage. 2727 To provide compatibility, Chinese languages encompassed by the 'zh' 2728 subtag are in the registry as both primary language subtags and as 2729 extended language subtags. For example, the ISO 639-3 code for 2730 Cantonese is 'yue'. Content in Cantonese might historically have 2731 used a tag such as "zh-HK" (since Cantonese is commonly spoken in 2732 Hong Kong), although that tag actually means any type of Chinese as 2733 used in Hong Kong. With the availability of ISO 639-3 codes in the 2734 registry, content in Cantonese can be directly tagged using the 'yue' 2735 subtag. The content can use it as a primary language subtag, as in 2736 the tag "yue-HK" (Cantonese, Hong Kong). Or it can use an extended 2737 language subtag with 'zh', as in the tag "zh-yue-Hant" (Chinese, 2738 Cantonese, Traditional script). 2740 As noted above, applications can choose to use the macrolanguage 2741 subtag to form the tag instead of using the more specific encompassed 2742 language subtag. For example, an application with large quantities 2743 of data already using tags with the 'zh' (Chinese) subtag might 2744 continue to use this more general subtag even for new data, even 2745 though the content could be more precisely tagged with 'cmn' 2746 (Mandarin), 'yue' (Cantonese), 'wuu' (Wu), and so on. Similarly, an 2747 application already using tags that start with the 'ar' (Arabic) 2748 subtag might continue to use this more general subtag even for new 2749 data, which could be more precisely be tagged with 'arb' (Standard 2750 Arabic). 2752 In some cases, the encompassed languages had tags registered for them 2753 during the RFC 3066 era. Those grandfathered tags not already 2754 deprecated or rendered redundant were deprecated in the registry upon 2755 adoption of this document. As grandfathered values, they remain 2756 valid for use and some content or applications might use them. As 2757 with other grandfathered tags, since implementations might not be 2758 able to associate the grandfathered tags with the encompassed 2759 language subtag equivalents that are recommended by this document, 2760 implementations are encouraged to canonicalize tags for comparison 2761 purposes. Some examples of this include the tags "zh-hakka" (Hakka) 2762 and "zh-guoyu" (Mandarin or Standard Chinese). 2764 Sign languages share a mode of communication rather than a linguistic 2765 heritage. There are many sign languages which have developed 2766 independently and the subtag 'sgn' indicates only the presence of a 2767 sign language. A number of sign languages also had grandfathered 2768 tags registered for them during the RFC 3066 era. For example, the 2769 grandfathered tag "sgn-US" was registered to represent 'American Sign 2770 Language' specifically, without reference to the United States. This 2771 is still valid, but deprecated: a document in American Sign Language 2772 can be labeled either "ase" or "sgn-ase" (the 'ase' subtag is for the 2773 language called 'American Sign Language'). 2775 4.2. Meaning of the Language Tag 2777 The meaning of a language tag is related to the meaning of the 2778 subtags that it contains. Each subtag, in turn, implies a certain 2779 range of expectations one might have for related content, although it 2780 is not a guarantee. For example, the use of a script subtag such as 2781 'Arab' (Arabic script) does not mean that the content contains only 2782 Arabic characters. It does mean that the language involved is 2783 predominantly in the Arabic script. Thus a language tag and its 2784 subtags can encompass a very wide range of variation and yet remain 2785 appropriate in each particular instance. 2787 Validity of a tag is not the only factor determining its usefulness. 2788 While every valid tag has a meaning, it might not represent any real- 2789 world language usage. This is unavoidable in a system in which 2790 subtags can be combined freely. For example, tags such as 2791 "ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia) or "tlh- 2792 Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA 2793 phonetic transcription) are both valid and unlikely to represent a 2794 useful combination of language attributes. 2796 The meaning of a given tag doesn't depend on the context in which it 2797 appears. The relationship between a tag's meaning and the 2798 information objects to which that tag is applied, however, can vary. 2800 o For a single information object, the associated language tags 2801 might be interpreted as the set of languages that is necessary for 2802 a complete comprehension of the complete object. Example: Plain 2803 text documents. 2805 o For an aggregation of information objects, the associated language 2806 tags could be taken as the set of languages used inside components 2807 of that aggregation. Examples: Document stores and libraries. 2809 o For information objects whose purpose is to provide alternatives, 2810 the associated language tags could be regarded as a hint that the 2811 content is provided in several languages and that one has to 2812 inspect each of the alternatives in order to find its language or 2813 languages. In this case, the presence of multiple tags might not 2814 mean that one needs to be multi-lingual to get complete 2815 understanding of the document. Example: MIME multipart/ 2816 alternative. 2818 o For markup languages, such as HTML and XML, language information 2819 can be added to each part of the document identified by the markup 2820 structure (including the whole document itself). For example, one 2821 could write C'est la vie. inside a German 2822 document; the German-speaking user could then access a French- 2823 German dictionary to find out what the marked section meant. If 2824 the user were listening to that document through a speech 2825 synthesis interface, this formation could be used to signal the 2826 synthesizer to appropriately apply French text-to-speech 2827 pronunciation rules to that span of text, instead of applying the 2828 inappropriate German rules. 2830 o For markup languages and document formats that allow the audience 2831 to be identified, a language tag could indicate the audience(s) 2832 appropriate for that document. For example, the same HTML 2833 document described in the preceding bullet might have an HTTP 2834 header "Content-Language: de" to indicate that the intended 2835 audience audience for the file is German (even though three words 2836 appear and are identified as being in French within it). 2838 o For systems and APIs, language tags form the basis for most 2839 implementations of locale identifiers. For example, see Unicode's 2840 CLDR (Common Locale Data Repository) project. 2842 Language tags are related when they contain a similar sequence of 2843 subtags. For example, if a language tag B contains language tag A as 2844 a prefix, then B is typically "narrower" or "more specific" than A. 2845 Thus, "zh-Hant-TW" is more specific than "zh-Hant". 2847 This relationship is not guaranteed in all cases: specifically, 2848 languages that begin with the same sequence of subtags are NOT 2849 guaranteed to be mutually intelligible, although they might be. For 2850 example, the tag "az" shares a prefix with both "az-Latn" 2851 (Azerbaijani written using the Latin script) and "az-Cyrl" 2852 (Azerbaijani written using the Cyrillic script). A person fluent in 2853 one script might not be able to read the other, even though the 2854 linguistic content (e.g., what would be heard if both texts were read 2855 aloud) might be identical. Content tagged as "az" most probably is 2856 written in just one script and thus might not be intelligible to a 2857 reader familiar with the other script. 2859 Similarly, not all subtags specify an actual distinction in language. 2860 For example, the tags "en-US" and "en-CA" mean, roughly, English with 2861 features generally thought to be characteristic of the United States 2862 and Canada, respectively. They do not imply that a significant 2863 dialectical boundary exists between any arbitrarily selected point in 2864 the United States and any arbitrarily selected point in Canada. 2865 Neither does a particular region subtag imply that linguistic 2866 distinctions do not exist within that region. 2868 4.3. Lists of Languages 2870 In some applications, a single content item might best be associated 2871 with more than one language tag. Examples of such a usage include: 2873 o A language priority list [RFC4647] describing a user's language 2874 preferences. This is a (possibly weighted) list of potentially- 2875 unrelated varieties, expressing a preference, rather than as a 2876 declaration about actual content. 2878 o Content items that contain multiple, distinct varieties. Often 2879 this is used to indicate an appropriate audience for a given 2880 content item when multiple choices might be appropriate. Examples 2881 of this could include: 2883 * Metadata about the appropriate audience for a movie title. For 2884 example, a DVD might label its individual audio tracks 'de' 2885 (German), 'fr' (French), and 'es' (Spanish), but the overall 2886 title would list "de, fr, es" as its overall audience. 2888 * A French/English, English/French dictionary tagged as both "en" 2889 and "fr" to specify that it applies equally to French and 2890 English 2892 * A side-by-side or interlinear translation of a document, as is 2893 commonly done with classical works in Latin or Greek 2895 o Content items that contain a single language but which require 2896 multiple levels of specificity. For example, a library might wish 2897 to classify a particular work as both Norwegian ('no') and as 2898 Nynorsk ('nn') for audiences capable of appreciating the 2899 distinction or needing to select content more narrowly. 2901 4.4. Length Considerations 2903 There is no defined upper limit on the size of language tags. While 2904 historically most language tags have consisted of language and region 2905 subtags with a combined total length of up to six characters, larger 2906 tags have always been both possible and have actually appeared in 2907 use. 2909 Neither the language tag syntax nor other requirements in this 2910 document impose a fixed upper limit on the number of subtags in a 2911 language tag (and thus an upper bound on the size of a tag). The 2912 language tag syntax suggests that, depending on the specific 2913 language, more subtags (and thus a longer tag) are sometimes 2914 necessary to completely identify the language for certain 2915 applications; thus, it is possible to envision long or complex subtag 2916 sequences. 2918 4.4.1. Working with Limited Buffer Sizes 2920 Some applications and protocols are forced to allocate fixed buffer 2921 sizes or otherwise limit the length of a language tag. A conformant 2922 implementation or specification MAY refuse to support the storage of 2923 language tags that exceed a specified length. Any such limitation 2924 SHOULD be clearly documented, and such documentation SHOULD include 2925 what happens to longer tags (for example, whether an error value is 2926 generated or the language tag is truncated). A protocol that allows 2927 tags to be truncated at an arbitrary limit, without giving any 2928 indication of what that limit is, has the potential for causing harm 2929 by changing the meaning of tags in substantial ways. 2931 In practice, most language tags do not require more than a few 2932 subtags and will not approach reasonably sized buffer limitations; 2933 see Section 4.1. 2935 Some specifications or protocols have limits on tag length but do not 2936 have a fixed length limitation. For example, [RFC2231] has no 2937 explicit length limitation: the length available for the language tag 2938 is constrained by the length of other header components (such as the 2939 charset's name) coupled with the 76-character limit in [RFC2047]. 2940 Thus, the "limit" might be 50 or more characters, but it could 2941 potentially be quite small. 2943 The considerations for assigning a buffer limit are: 2945 Implementations SHOULD NOT truncate language tags unless the 2946 meaning of the tag is purposefully being changed, or unless the 2947 tag does not fit into a limited buffer size specified by a 2948 protocol for storage or transmission. 2950 Implementations SHOULD warn the user when a tag is truncated since 2951 truncation changes the semantic meaning of the tag. 2953 Implementations of protocols or specifications that are space 2954 constrained but do not have a fixed limit SHOULD use the longest 2955 possible tag in preference to truncation. 2957 Protocols or specifications that specify limited buffer sizes for 2958 language tags MUST allow for language tags of at least 35 2959 characters. Note that RFC 4646 [RFC4646] recommended a minimum 2960 field size of 42 characters because it included all three elements 2961 of the 'extlang' production. Two of these are now permanently 2962 reserved, so a registered primary language subtag of the maximum 2963 length of eight characters is now longer than the longest 2964 language-extlang combintation. Protocols or specifications that 2965 commonly use extensions or private use subtags might wish to 2966 reserve or recommend a longer "minimum buffer" size. 2968 The following illustration shows how the 35-character recommendation 2969 was derived: 2971 language = 8 ; longest allowed registered value 2972 ; longer than primary+extlang 2973 ; which requires 7 characters 2974 script = 5 ; if not suppressed: see Section 4.1 2975 region = 4 ; UN M.49 numeric region code 2976 ; ISO 3166-1 codes require 3 2977 variant1 = 9 ; needs 'language' as a prefix 2978 variant2 = 9 ; very rare, as it needs 2979 ; 'language-variant1' as a prefix 2981 total = 35 characters 2983 Figure 7: Derivation of the Limit on Tag Length 2985 4.4.2. Truncation of Language Tags 2987 Truncation of a language tag alters the meaning of the tag, and thus 2988 SHOULD be avoided. However, truncation of language tags is sometimes 2989 necessary due to limited buffer sizes. Such truncation MUST NOT 2990 permit a subtag to be chopped off in the middle or the formation of 2991 invalid tags (for example, one ending with the "-" character). 2993 This means that applications or protocols that truncate tags MUST do 2994 so by progressively removing subtags along with their preceding "-" 2995 from the right side of the language tag until the tag is short enough 2996 for the given buffer. If the resulting tag ends with a single- 2997 character subtag, that subtag and its preceding "-" MUST also be 2998 removed. For example: 3000 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 3001 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 3002 2. zh-Latn-CN-variant1-a-extend1 3003 3. zh-Latn-CN-variant1 3004 4. zh-Latn-CN 3005 5. zh-Latn 3006 6. zh 3008 Figure 8: Example of Tag Truncation 3010 4.5. Canonicalization of Language Tags 3012 Since a particular language tag is sometimes used by many processes, 3013 language tags SHOULD always be created or generated in a canonical 3014 form. 3016 A language tag is in canonical form when: 3018 1. The tag is well-formed according the rules in Section 2.1 and 3019 Section 2.2. 3021 2. Redundant or grandfathered tags that have a Preferred-Value 3022 mapping in the IANA registry (see Section 3.1) MUST be replaced 3023 with their mapped value. These items either are deprecated 3024 mappings created before the adoption of this document (such as 3025 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 3026 the result of later registrations or additions to this document 3027 (for example, "zh-hakka" was deprecated in favor of the ISO 639-3 3028 code 'hak' when this document was adopted). These mappings 3029 SHOULD be done before additional processing, since there can be 3030 additional changes to subtag values. These field-body of the 3031 Preferred-Value for grandfathered and redundant tags is an 3032 "extended language range" ([RFC4647]) and might consist of more 3033 than one subtag. 3035 3. Subtags of type 'extlang' SHOULD be mapped to their Preferred- 3036 Value. The field-body of the Preferred-Value for extlangs is an 3037 "extended language range" and typically maps to a primary 3038 language subtag. For example, the subtag sequence "zh-hak" 3039 (Chinese, Hakka) would be replaced with the tag "hak" (Hakka). 3041 4. Other subtags that have a Preferred-Value field in the IANA 3042 registry (see Section 3.1) MUST be replaced with their mapped 3043 value. Most of these are either Region subtags where the country 3044 name or designation has changed or clerical corrections to ISO 3045 639-1. 3047 5. If more than one extension subtag sequence exists, the extension 3048 sequences are ordered into case-insensitive ASCII order by 3049 singleton subtag. 3051 Example: The language tag "en-a-aaa-b-ccc-bbb-x-xyz" is in canonical 3052 form, while "en-b-ccc-bbb-a-aaa-X-xyz" is well-formed and potentially 3053 valid (extensions 'a' and 'b' are not defined as of the publication 3054 of this document) but not in canonical form (the extensions are not 3055 in alphabetical order). 3057 Example: Although the tag "en-BU" (English as used in Burma) 3058 maintains its validity, the language tag "en-BU" is not canonical 3059 because the 'BU' subtag has a canonical mapping to 'MM' (Myanmar). 3061 Canonicalization of language tags does not imply anything about the 3062 use of upper or lowercase letters when processing or comparing 3063 subtags (and as described in Section 2.1). All comparisons MUST be 3064 performed in a case-insensitive manner. 3066 When performing canonicalization of language tags, processors MAY 3067 regularize the case of the subtags (that is, this process is 3068 OPTIONAL), following the case used in the registry (see 3069 Section 2.1.1). 3071 If more than one variant appears within a tag, processors MAY reorder 3072 the variants to obtain better matching behavior or more consistent 3073 presentation. Reordering of the variants SHOULD follow the 3074 recommendations for variant ordering in Section 4.1. 3076 If the field 'Deprecated' appears in a registry record without an 3077 accompanying 'Preferred-Value' field, then that tag or subtag is 3078 deprecated without a replacement. These values are canonical when 3079 they appear in a language tag. However, tags that include these 3080 values SHOULD NOT be selected by users or generated by 3081 implementations. 3083 An extension MUST define any relationships that exist between the 3084 various subtags in the extension and thus MAY define an alternate 3085 canonicalization scheme for the extension's subtags. Extensions MAY 3086 define how the order of the extension's subtags are interpreted. For 3087 example, an extension could define that its subtags are in canonical 3088 order when the subtags are placed into ASCII order: that is, "en-a- 3089 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 3090 define that the order of the subtags influences their semantic 3091 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 3092 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 3093 so that they are tolerant of the typical processes described in 3094 Section 3.7. 3096 4.6. Considerations for Private Use Subtags 3098 Private use subtags, like all other subtags, MUST conform to the 3099 format and content constraints in the ABNF. Private use subtags have 3100 no meaning outside the private agreement between the parties that 3101 intend to use or exchange language tags that employ them. The same 3102 subtags MAY be used with a different meaning under a separate private 3103 agreement. They SHOULD NOT be used where alternatives exist and 3104 SHOULD NOT be used in content or protocols intended for general use. 3106 Private use subtags are simply useless for information exchange 3107 without prior arrangement. The value and semantic meaning of private 3108 use tags and of the subtags used within such a language tag are not 3109 defined by this document. 3111 Private use sequences introduced by the 'x' singleton are completely 3112 opaque to users or implementations outside of the private use 3113 agreement. So, in addition to private use subtag sequences 3114 introduced by the singleton subtag 'x', the Language Subtag Registry 3115 provides private use language, script, and region subtags derived 3116 from the private use codes assigned by the underlying standards. 3117 These subtags are valid for use in forming language tags; they are 3118 RECOMMENDED over the 'x' singleton private use subtag sequences 3119 because they convey more information via their linkage to the 3120 language tag's inherent structure. 3122 For example, the region subtags 'AA', 'ZZ', and in the ranges 3123 'QM'-'QZ' and 'XA'-'XZ' (derived from the ISO 3166-1 private use 3124 codes) can be used to form a language tag. A tag such as 3125 "zh-Hans-XQ" conveys a great deal of public, interchangeable 3126 information about the language material (that it is Chinese in the 3127 simplified Chinese script and is suitable for some geographic region 3128 'XQ'). While the precise geographic region is not known outside of 3129 private agreement, the tag conveys far more information than an 3130 opaque tag such as "x-somelang" or even "zh-Hans-x-xq" (where the 3131 'xq' subtag's meaning is entirely opaque). 3133 However, in some cases content tagged with private use subtags MAY 3134 interact with other systems in a different and possibly unsuitable 3135 manner compared to tags that use opaque, privately defined subtags, 3136 so the choice of the best approach sometimes depends on the 3137 particular domain in question. 3139 5. IANA Considerations 3141 This section deals with the processes and requirements necessary for 3142 IANA to undertake to maintain the subtag and extension registries as 3143 defined by this document and in accordance with the requirements of 3144 [RFC2434]. 3146 The impact on the IANA maintainers of the two registries defined by 3147 this document will be a small increase in the frequency of new 3148 entries or updates. IANA also is required to create a new mailing 3149 list (described below in Section 5.1) to announce registry changes 3150 and updates. 3152 5.1. Language Subtag Registry 3154 Upon adoption of this document, IANA will update the registry using 3155 instructions and content provided in a companion document: 3156 [registry-update]. The criteria and process for selecting the 3157 updated set of records are described in that document. The updated 3158 set of records represents no impact on IANA, since the work to create 3159 it will be performed externally. 3161 Future work on the Language Subtag Registry includes the following 3162 activities: 3164 o Inserting or replacing whole records. These records are 3165 preformatted for IANA by the Language Subtag Reviewer, as 3166 described in Section 3.3. 3168 o Archiving and making publicly available the registration forms. 3170 o Announcing each updated version of the registry on the 3171 "ietf-languages-announcements@iana.org" mailing list. 3173 Each registration form sent to IANA contains a single record for 3174 incorporation into the registry. The form will be sent to 3175 "iana@iana.org" by the Language Subtag Reviewer. It will have a 3176 subject line indicating whether the enclosed form represents an 3177 insertion of a new record (indicated by the word "INSERT" in the 3178 subject line) or a replacement of an existing record (indicated by 3179 the word "MODIFY" in the subject line). At no time can a record be 3180 deleted from the registry. 3182 IANA will extract the record from the form and place the inserted or 3183 modified record into the appropriate section of the language subtag 3184 registry, grouping the records by their 'Type' field. Inserted 3185 records can be placed anywhere in the appropriate section; there is 3186 no guarantee of the order of the records beyond grouping them 3187 together by 'Type'. Modified records overwrite the record they 3188 replace. 3190 Whenever an entry is created or modified in the registry, the 'File- 3191 Date' record at the start of the registry is updated to reflect the 3192 most recent modification date in the [RFC3339] "full-date" format: 3193 included in any request to insert or modify records will be a new 3194 File-Date record indicating the acceptance date of the record. This 3195 record is to be placed first in the registry, replacing the existing 3196 File-Date record. In the event that the File-Date record present in 3197 the registry has a later date than the record being inserted or 3198 modified, then the latest (most recent) record will be preserved. 3199 IANA should attempt to process multiple registration requests in 3200 order according to the File-Date in the form, since one registration 3201 could otherwise cause a more recent change to be overwritten. 3203 The updated registry file MUST use the UTF-8 character encoding and 3204 IANA MUST check the registry file for proper encoding. Non-ASCII 3205 characters can be sent to IANA by attaching the registration form to 3206 the email message or by using various encodings in the mail message 3207 body (UTF-8 is recommended). IANA will verify any unclear or 3208 corrupted characters with the Language Subtag Reviewer prior to 3209 posting the updated registry. 3211 IANA will also archive and make publicly available from 3212 "http://www.iana.org/assignments/lang-subtags-templates/" each 3213 registration form. Note that multiple registrations can pertain to 3214 the same record in the registry. 3216 Developers who are dependent upon the language subtag registry 3217 sometimes would like to be informed of changes in the registry so 3218 that they can update their implementations. When any change is made 3219 to the language subtag registry, IANA will send an announcement 3220 message to "ietf-languages-announcements@iana.org" (a self- 3221 subscribing list that only IANA can post to). 3223 5.2. Extensions Registry 3225 The Language Tag Extensions Registry can contain at most 35 records 3226 and thus changes to this registry are expected to be very infrequent. 3228 Future work by IANA on the Language Tag Extensions Registry is 3229 limited to two cases. First, the IESG MAY request that new records 3230 be inserted into this registry from time to time. These requests 3231 MUST include the record to insert in the exact format described in 3232 Section 3.7. In addition, there MAY be occasional requests from the 3233 maintaining authority for a specific extension to update the contact 3234 information or URLs in the record. These requests MUST include the 3235 complete, updated record. IANA is not responsible for validating the 3236 information provided, only that it is properly formatted. IANA 3237 SHOULD take reasonable steps to ascertain that the request comes from 3238 the maintaining authority named in the record present in the 3239 registry. 3241 6. Security Considerations 3243 Language tags used in content negotiation, like any other information 3244 exchanged on the Internet, might be a source of concern because they 3245 might be used to infer the nationality of the sender, and thus 3246 identify potential targets for surveillance. 3248 This is a special case of the general problem that anything sent is 3249 visible to the receiving party and possibly to third parties as well. 3250 It is useful to be aware that such concerns can exist in some cases. 3252 The evaluation of the exact magnitude of the threat, and any possible 3253 countermeasures, is left to each application protocol (see BCP 72 3254 [RFC3552] for best current practice guidance on security threats and 3255 defenses). 3257 The language tag associated with a particular information item is of 3258 no consequence whatsoever in determining whether that content might 3259 contain possible homographs. The fact that a text is tagged as being 3260 in one language or using a particular script subtag provides no 3261 assurance whatsoever that it does not contain characters from scripts 3262 other than the one(s) associated with or specified by that language 3263 tag. 3265 Since there is no limit to the number of variant, private use, and 3266 extension subtags, and consequently no limit on the possible length 3267 of a tag, implementations need to guard against buffer overflow 3268 attacks. See Section 4.4 for details on language tag truncation, 3269 which can occur as a consequence of defenses against buffer overflow. 3271 Although the specification of valid subtags for an extension (see 3272 Section 3.7) MUST be available over the Internet, implementations 3273 SHOULD NOT mechanically depend on it being always accessible, to 3274 prevent denial-of-service attacks. 3276 7. Character Set Considerations 3278 The syntax in this document requires that language tags use only the 3279 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 3280 character sets, so the composition of language tags should not have 3281 any character set issues. 3283 The rendering of text based on the language tag is not addressed 3284 here. Historically, some processes have relied on the use of 3285 character set/encoding information (or other external information) in 3286 order to infer how a specific string of characters should be 3287 rendered. Notably this applies to language- and culture-specific 3288 variations of Han ideographs as used in Japanese, Chinese, and 3289 Korean, where use of, for example, a Japanese character encoding such 3290 as EUC-JP implies that the text itself is in Japanese. When language 3291 tags are applied to spans of text, rendering engines might be able to 3292 use that information to better select fonts or make other rendering 3293 choices, particularly where languages with distinct writing 3294 traditions use the same characters. 3296 8. Changes from RFC 4646 3298 The main goal for this revision of this document was to incorporate 3299 two new parts of ISO 639 (ISO 639-3 and ISO 639-5) and their 3300 attendant sets of language codes into the IANA Language Subtag 3301 Registry. This permits the identification of many more languages and 3302 language collections than previously supported. 3304 The specific changes in this document to meet these goals are: 3306 o Defines the incorporation of ISO 639-3 and ISO 639-5 codes for use 3307 as primary and extended language subtags. It also permanently 3308 reserves and disallows the use of additional 'extlang' subtags. 3309 The changes necessary to achieve this were: 3311 * Modified the ABNF comments. 3313 * Updated various registration and stability requirements 3314 sections to reference ISO 639-3 and ISO 639-5 in addition to 3315 ISO 639-1 and ISO 639-2. 3317 * Edited the text to eliminate references to extended language 3318 subtags where they are no longer used. 3320 * Explained the change in the section on extended language 3321 subtags. 3323 o Changed the ABNF related to grandfathered tags. The irregular 3324 tags are now listed. Well-formed grandfathered tags are now 3325 described by the 'langtag' production and the 'grandfathered' 3326 production was removed as a result. Also: added description of 3327 both types of grandfathered tags to Section 2.2.8. 3329 o Added the paragraph on "collections" to Section 4.1. 3331 o Changed the capitalization rules for 'Tag' fields in Section 3.1. 3333 o Split section 3.1 up into subsections. 3335 o Modified section 3.5 to allow Suppress-Script fields to be added, 3336 modified, or removed via the registration process. This was an 3337 erratum from RFC 4646. 3339 o Modified examples that used region code 'CS' (formerly Serbia and 3340 Montenegro) to use 'RS' (Serbia) instead. 3342 o Modified the rules for creating and maintaining record 3343 'Description' fields to prevent duplicates, including inverted 3344 duplicates. 3346 o Removed the lengthy description of why RFC 4646 was created from 3347 this section, which also caused the removal of the reference to 3348 XML Schema. 3350 o Modified the text in section 2.1 to place more emphasis on the 3351 fact that language tags are not case sensitive. 3353 o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" 3354 and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the 3355 Suppress-Script on 'Latn' with 'fr'. 3357 o Changed the requirements for well-formedness to make singleton 3358 repetition checking optional (it is required for validity 3359 checking) in Section 2.2.9. 3361 o Changed the text in Section 2.2.9 referring to grandfathered 3362 checking to note that the list is now included in the ABNF. 3364 o Modified and added text to Section 3.2. The job description was 3365 placed first. A note was added making clear that the Language 3366 Subtag Reviewer may delegate various non-critical duties, 3367 including list moderation. Finally, additional text was added to 3368 make the appointment process clear and to clarify that decisions 3369 and performance of the reviewer are appealable. 3371 o Added text to Section 3.5 clarifying that the ietf-languages list 3372 is operated by whomever the IESG appoints. 3374 o Added text to Section 3.1.5 clarifying that the first Description 3375 in a 'language' record matches the corresponding Reference Name 3376 for the language in ISO 639-3. 3378 o Modified Section 2.2.9 to define classes of conformance related to 3379 specific tags (formerly 'well-formed' and 'valid' referred to 3380 implementations). Notes were added about the removal of 'extlang' 3381 from the ABNF provided in RFC 4646, allowing for well-formedness 3382 using this older definition. Reference to RFC 3066 well- 3383 formedness was also added. 3385 o Added text to the end of Section 3.1.2 noting that future versions 3386 of this document might add new field types to the Registry format 3387 and recommending that implementations ignore any unrecognized 3388 fields. 3390 o Added text about what the lack of a Suppress-Script field means in 3391 a record to Section 3.1.9. 3393 o Added text allowing the correction of misspellings and typographic 3394 errors to Section 3.1.5. 3396 o Added text to Section 3.1.8 disallowing Prefix field conflicts 3397 (such as circular prefix references). 3399 o Modified text in Section 3.5 to require the subtag reviewer to 3400 announce his/her decision (or extension) following the two-week 3401 period. Also clarified that any decision or failure to decide can 3402 be appealed. 3404 o Modified text in Section 4.1 to include the (heretofore anecdotal) 3405 guiding principle of tag choice, and clarifying the non-use of 3406 script subtags in non-written applications. Also updated examples 3407 in this section to use Chamic languages as an example of language 3408 collections. 3410 o Prohibited multiple use of the same variant in a tag (i.e. "de- 3411 1901-1901"). Previously this was only a recommendation 3412 ("SHOULD"). 3414 o Removed inappropriate [RFC2119] language from the illustration in 3415 Section 4.4.1. 3417 o Replaced the example of deprecating "zh-guoyu" with "zh- 3418 hakka"->"hak" in Section 4.5, noting that it was this document 3419 that caused the change. 3421 o Replaced the section in Section 4.1 dealing with "mul"/"und" to 3422 include the subtags 'zxx' and 'mis', as well as the tag 3423 "i-default". A normative reference to RFC 2277 was added, along 3424 with an informative reference to MARC21. 3426 o Added text to Section 3.5 clarifying that any modifications of a 3427 registration request must be sent to the ietf-languages list 3428 before submission to IANA. 3430 o Changed the ABNF for the record-jar format from using the LWSP 3431 production to use a folding whitespace production similar to obs- 3432 FWS in [RFC5234]. This effectively prevents unintentional blank 3433 lines inside a field. 3435 o Clarified and revised text in Section 3.3, Section 3.5, and 3436 Section 5.1 to clarify that the Language Subtag Reviewer sends the 3437 complete registration forms to IANA, that IANA extracts the record 3438 from the form, and that the forms must also be archived separately 3439 from the registry. 3441 o Added text to Section 5 requiring IANA to send an announcement to 3442 an ietf-languages-announce list whenever the registry is updated. 3444 o Modification of the registry to use UTF-8 as its character 3445 encoding. This also entails additional instructions to IANA and 3446 the Language Subtag Reviewer in the registration process. 3448 o Modified the rules in Section 2.2.4 so that "exceptionally 3449 reserved" ISO 3166-1 codes other than 'UK' were included into the 3450 registry. In particular, this allows the code 'EU' (European 3451 Union) to be used to form language tags or (more commonly) for 3452 applications that use the registry for region codes to reference 3453 this subtag. 3455 o Modified the IANA considerations section (Section 5) to remove 3456 unnecessary normative [RFC2119] language. 3458 9. References 3460 9.1. Normative References 3462 [ISO15924] 3463 International Organization for Standardization, "ISO 3464 15924:2004. Information and documentation -- Codes for the 3465 representation of names of scripts", January 2004. 3467 [ISO3166-1] 3468 International Organization for Standardization, "ISO 3166- 3469 1:2006. Codes for the representation of names of countries 3470 and their subdivisions -- Part 1: Country codes", 3471 November 2006. 3473 [ISO639-1] 3474 International Organization for Standardization, "ISO 639- 3475 1:2002. Codes for the representation of names of languages 3476 -- Part 1: Alpha-2 code", 2002. 3478 [ISO639-2] 3479 International Organization for Standardization, "ISO 639- 3480 2:1998. Codes for the representation of names of languages 3481 -- Part 2: Alpha-3 code, first edition", 1998. 3483 [ISO639-3] 3484 International Organization for Standardization, "ISO 639- 3485 3:2007. Codes for the representation of names of languages 3486 -- Part 3: Alpha-3 code for comprehensive coverage of 3487 languages", 2007. 3489 [ISO639-5] 3490 International Organization for Standardization, "ISO 639- 3491 5:1998. Codes for the representation of names of languages 3492 -- Part 5: Alpha-3 code for language families and groups", 3493 May 2008. 3495 [ISO646] International Organization for Standardization, "ISO/IEC 3496 646:1991, Information technology -- ISO 7-bit coded 3497 character set for information interchange.", 1991. 3499 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3500 3", BCP 9, RFC 2026, October 1996. 3502 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 3503 the IETF Standards Process", BCP 11, RFC 2028, 3504 October 1996. 3506 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3507 Requirement Levels", BCP 14, RFC 2119, March 1997. 3509 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and 3510 Languages", BCP 18, RFC 2277, January 1998. 3512 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3513 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 3514 October 1998. 3516 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 3517 Understanding Concerning the Technical Work of the 3518 Internet Assigned Numbers Authority", RFC 2860, June 2000. 3520 [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the 3521 Internet: Timestamps", RFC 3339, July 2002. 3523 [RFC4645] Ewell, D., "Initial Language Subtag Registry", RFC 4645, 3524 September 2006. 3526 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 3527 BCP 47, RFC 4647, September 2006. 3529 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 3530 Specifications: ABNF", STD 68, RFC 5234, January 2008. 3532 [UAX14] Freitag, A., "Unicode Standard Annex #14: Line Breaking 3533 Properties", August 2006, 3534 . 3536 [UN_M.49] Statistics Division, United Nations, "Standard Country or 3537 Area Codes for Statistical Use", UN Standard Country or 3538 Area Codes for Statistical Use, Revision 4 (United Nations 3539 publication, Sales No. 98.XVII.9, June 1999. 3541 9.2. Informative References 3543 [RFC1766] Alvestrand, H., "Tags for the Identification of 3544 Languages", RFC 1766, March 1995. 3546 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 3547 Part Three: Message Header Extensions for Non-ASCII Text", 3548 RFC 2047, November 1996. 3550 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 3551 Word Extensions: 3552 Character Sets, Languages, and Continuations", RFC 2231, 3553 November 1997. 3555 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 3556 10646", RFC 2781, February 2000. 3558 [RFC3066] Alvestrand, H., "Tags for the Identification of 3559 Languages", RFC 3066, January 2001. 3561 [RFC3282] Alvestrand, H., "Content Language Headers", RFC 3282, 3562 May 2002. 3564 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 3565 Text on Security Considerations", BCP 72, RFC 3552, 3566 July 2003. 3568 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 3569 10646", STD 63, RFC 3629, November 2003. 3571 [RFC4646] Phillips, A. and M. Davis, "Tags for Identifying 3572 Languages", BCP 47, RFC 4646, September 2006. 3574 [UTS35] Davis, M., "Unicode Technical Standard #35: Locale Data 3575 Markup Language (LDML)", December 2007, 3576 . 3578 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 3579 Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. 3580 ISBN 0-321-49081-0)", January 2007. 3582 [iso639.prin] 3583 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 3584 Committee: Working principles for ISO 639 maintenance", 3585 March 2000, 3586 . 3589 [record-jar] 3590 Raymond, E., "The Art of Unix Programming", 2003, 3591 . 3593 [registry-update] 3594 Ewell, D., Ed., "Update to the Language Subtag Registry", 3595 September 2006, . 3598 Appendix A. Acknowledgements 3600 Any list of contributors is bound to be incomplete; please regard the 3601 following as only a selection from the group of people who have 3602 contributed to make this document what it is today. 3604 The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the 3605 precursors of this document, made enormous contributions directly or 3606 indirectly to this document and are generally responsible for the 3607 success of language tags. 3609 The following people contributed to this document: 3611 Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, 3612 Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion 3613 Gunn, Kent Karlsson, Chris Newman, Randy Presuhn, Stephen Silver, 3614 Shawn Steel, and many, many others. 3616 Very special thanks must go to Harald Tveit Alvestrand, who 3617 originated RFCs 1766 and 3066, and without whom this document would 3618 not have been possible. 3620 Special thanks go to Michael Everson, who served as the Language Tag 3621 Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as 3622 the Language Subtag Reviewer since the adoption of RFC 4646. 3624 Special thanks also to Doug Ewell, for his production of the first 3625 complete subtag registry, his work to support and maintain new 3626 registrations, and his careful editorship of both RFC 4645 and 3627 [registry-update]. 3629 Appendix B. Examples of Language Tags (Informative) 3631 Simple language subtag: 3633 de (German) 3635 fr (French) 3637 ja (Japanese) 3639 i-enochian (example of a grandfathered tag) 3641 Language subtag plus Script subtag: 3643 zh-Hant (Chinese written using the Traditional Chinese script) 3645 zh-Hans (Chinese written using the Simplified Chinese script) 3647 sr-Cyrl (Serbian written using the Cyrillic script) 3649 sr-Latn (Serbian written using the Latin script) 3651 Extended language subtags and their primary language subtag 3652 counterparts: 3654 zh-cmn-Hans-CN (Chinese, Mandarin, Simplified script, as used in 3655 China) 3657 cmn-Hans-CN (Mandarin Chinese, Simplified script, as used in 3658 China) 3660 zh-yue-HK (Chinese, Cantonese, as used in Hong Kong SAR) 3662 yue-HK (Cantonese Chinese, as used in Hong Kong SAR) 3664 Language-Script-Region: 3666 zh-Hans-CN (Chinese written using the Simplified script as used in 3667 mainland China) 3669 sr-Latn-RS (Serbian written using the Latin script as used in 3670 Serbia) 3672 Language-Variant: 3674 sl-rozaj (Resian dialect of Slovenian) 3675 sl-rozaj-biske (San Giorgio dialect of Resian dialect of 3676 Slovenian) 3678 sl-nedis (Nadiza dialect of Slovenian) 3680 Language-Region-Variant: 3682 de-CH-1901 (German as used in Switzerland using the 1901 variant 3683 [orthography]) 3685 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 3687 Language-Script-Region-Variant: 3689 hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as 3690 used in Italy) 3692 Language-Region: 3694 de-DE (German for Germany) 3696 en-US (English as used in the United States) 3698 es-419 (Spanish appropriate for the Latin America and Caribbean 3699 region using the UN region code) 3701 Private use subtags: 3703 de-CH-x-phonebk 3705 az-Arab-x-AZE-derbend 3707 Private use registry values: 3709 x-whatever (private use using the singleton 'x') 3711 qaa-Qaaa-QM-x-southern (all private tags) 3713 de-Qaaa (German, with a private script) 3715 sr-Latn-QM (Serbian, Latin-script, private region) 3717 sr-Qaaa-RS (Serbian, private script, for Serbia) 3719 Tags that use extensions (examples ONLY: extensions MUST be defined 3720 by revision or update to this document or by RFC): 3722 en-US-u-islamcal 3724 zh-CN-a-myext-x-private 3726 en-a-myext-b-another 3728 Some Invalid Tags: 3730 de-419-DE (two region tags) 3732 a-DE (use of a single-character subtag in primary position; note 3733 that there are a few grandfathered tags that start with "i-" that 3734 are valid) 3736 ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter 3737 prefix) 3739 Appendix C. Examples of Registration Forms 3740 LANGUAGE SUBTAG REGISTRATION FORM 3741 1. Name of requester: Han Steenwijk 3742 2. E-mail address of requester: han.steenwijk @ unipd.it 3743 3. Record Requested: 3745 Type: variant 3746 Subtag: biske 3747 Description: The San Giorgio dialect of Resian 3748 Description: The Bila dialect of Resian 3749 Prefix: sl-rozaj 3750 Comments: The dialect of San Giorgio/Bila is one of the 3751 four major local dialects of Resian 3753 4. Intended meaning of the subtag: The local variety of Resian as 3754 spoken in San Giorgio/Bila 3756 5. Reference to published description of the language (book or 3757 article): 3758 -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich 3759 govorov, Varsava - Peterburg: Vende - Kozancikov, 1875. 3761 LANGUAGE SUBTAG REGISTRATION FORM 3762 1. Name of requester: Jaska Zedlik 3763 2. E-mail address of requester: jz53 @ zedlik.com 3764 3. Record Requested: 3766 Type: variant 3767 Subtag: tarask 3768 Description: Belarusian in Taraskievica orthography 3769 Prefix: be 3770 Comments: The subtag represents Branislau Taraskievic's Belarusian 3771 orthography as published in "Bielaruski klasycny pravapis" by Juras 3772 Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka 3773 (Vilnia-Miensk 2005). 3775 4. Intended meaning of the subtag: 3777 The subtag is intended to represent the Belarusian orthography as 3778 published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk 3779 Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005). 3781 5. Reference to published description of the language (book or article): 3783 Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd. 3784 "Bielaruskaha kamitetu", 1929, 5th edition. 3786 Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier. 3787 Bielaruski klasycny pravapis. Vilnia-Miensk, 2005. 3789 6. Any other relevant information: 3791 Belarusian in Taraskievica orthography became widely used, especially in 3792 Belarusian-speaking Internet segment, but besides this some books and 3793 newspapers are also printed using this orthography of Belarusian. 3795 Authors' Addresses 3797 Addison Phillips (editor) 3798 Lab126 3800 Email: addison@inter-locale.com 3801 URI: http://www.inter-locale.com 3803 Mark Davis (editor) 3804 Google 3806 Email: mark.davis@google.com 3808 Full Copyright Statement 3810 Copyright (C) The IETF Trust (2008). 3812 This document is subject to the rights, licenses and restrictions 3813 contained in BCP 78, and except as set forth therein, the authors 3814 retain all their rights. 3816 This document and the information contained herein are provided on an 3817 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 3818 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 3819 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 3820 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 3821 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 3822 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 3824 Intellectual Property 3826 The IETF takes no position regarding the validity or scope of any 3827 Intellectual Property Rights or other rights that might be claimed to 3828 pertain to the implementation or use of the technology described in 3829 this document or the extent to which any license under such rights 3830 might or might not be available; nor does it represent that it has 3831 made any independent effort to identify any such rights. Information 3832 on the procedures with respect to rights in RFC documents can be 3833 found in BCP 78 and BCP 79. 3835 Copies of IPR disclosures made to the IETF Secretariat and any 3836 assurances of licenses to be made available, or the result of an 3837 attempt made to obtain a general license or permission for the use of 3838 such proprietary rights by implementers or users of this 3839 specification can be obtained from the IETF on-line IPR repository at 3840 http://www.ietf.org/ipr. 3842 The IETF invites any interested party to bring to its attention any 3843 copyrights, patents or patent applications, or other proprietary 3844 rights that may cover technology that may be required to implement 3845 this standard. Please address the information to the IETF at 3846 ietf-ipr@ietf.org.