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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: June 5, 2009 December 2, 2008 8 Tags for Identifying Languages 9 draft-ietf-ltru-4646bis-19 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 June 5, 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 1. Introduction 46 Human beings on our planet have, past and present, used a number of 47 languages. There are many reasons why one would want to identify the 48 language used when presenting or requesting information. 50 The language of an information item or a user's language preferences 51 often need to be identified so that appropriate processing can be 52 applied. For example, the user's language preferences in a Web 53 browser can be used to select Web pages appropriately. Language 54 information can also be used to select among tools (such as 55 dictionaries) to assist in the processing or understanding of content 56 in different languages. Knowledge about the particular language used 57 by some piece of information content might be useful or even required 58 by some types of processing; for example, spell-checking, computer- 59 synthesized speech, Braille transcription, or high-quality print 60 renderings. 62 One means of indicating the language used is by labeling the 63 information content with an identifier or "tag". These tags can also 64 be used to specify the user's preferences when selecting information 65 content, or for labeling additional attributes of content and 66 associated resources. 68 Sometimes language tags are used to indicate additional language 69 attributes of content. For example, indicating specific information 70 about the dialect, writing system, or orthography used in a document 71 or resource may enable the user to obtain information in a form that 72 they can understand, or it can be important in processing or 73 rendering the given content into an appropriate form or style. 75 This document specifies a particular identifier mechanism (the 76 language tag) and a registration function for values to be used to 77 form tags. It also defines a mechanism for private use values and 78 future extension. 80 This document replaces [RFC4646], which replaced [RFC3066] and its 81 predecessor [RFC1766]. For a list of changes in this document, see 82 Section 8. 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in [RFC2119]. 88 2. The Language Tag 90 Language tags are used to help identify languages, whether spoken, 91 written, signed, or otherwise signaled, for the purpose of 92 communication. This includes constructed and artificial languages, 93 but excludes languages not intended primarily for human 94 communication, such as programming languages. 96 2.1. Syntax 98 A language tag is composed from a sequence of one or more "subtags", 99 each of which refines or narrows the range of language identified by 100 the overall tag. Subtags, in turn, are a sequence of alphanumeric 101 characters (letters and digits), distinguished and separated from 102 other subtags in a tag by a hyphen ("-", ABNF [RFC5234] %x2D). 104 There are different types of subtag, each of which is distinguished 105 by length, position in the tag, and content: each subtag's type can 106 be recognized solely by these features. This makes it possible to 107 extract and assign some semantic information to the subtags, even if 108 the specific subtag values are not recognized. Thus, a language tag 109 processor need not have a list of valid tags or subtags (that is, a 110 copy of some version of the IANA Language Subtag Registry) in order 111 to perform common searching and matching operations. The only 112 exceptions to this ability to infer meaning from subtag structure are 113 the grandfathered tags listed in the productions 'regular' and 114 'irregular' below. These tags were registered under [RFC3066] and 115 are a fixed list that can never change. 117 The syntax of the language tag in ABNF [RFC5234] is: 119 Language-Tag = langtag ; normal language tags 120 / privateuse ; private use tag 121 / grandfathered ; grandfathered tags 123 langtag = language 124 ["-" script] 125 ["-" region] 126 *("-" variant) 127 *("-" extension) 128 ["-" privateuse] 130 language = 2*3ALPHA ; shortest ISO 639 code 131 ["-" extlang] ; sometimes followed by 132 ; extended language subtags 133 / 4ALPHA ; or reserved for future use 134 / 5*8ALPHA ; or registered language subtag 136 extlang = 3ALPHA ; selected ISO 639 codes 137 *2("-" 3ALPHA) ; permanently reserved 139 script = 4ALPHA ; ISO 15924 code 141 region = 2ALPHA ; ISO 3166-1 code 142 / 3DIGIT ; UN M.49 code 144 variant = 5*8alphanum ; registered variants 145 / (DIGIT 3alphanum) 147 extension = singleton 1*("-" (2*8alphanum)) 149 ; Single alphanumerics 150 ; "x" reserved for private use 151 singleton = DIGIT ; 0 - 9 152 / %x41-57 ; A - W 153 / %x59-5A ; Y - Z 154 / %x61-77 ; a - w 155 / %x79-7A ; y - z 157 privateuse = "x" 1*("-" (1*8alphanum)) 159 grandfathered = irregular ; non-redundant tags registered 160 / regular ; during the RFC 3066 era 162 irregular = "en-GB-oed" ; irregular tags do not match 163 / "i-ami" ; the 'langtag' production and 164 / "i-bnn" ; would not otherwise be 165 / "i-default" ; considered 'well-formed' 166 / "i-enochian" ; These tags are all valid, 167 / "i-hak" ; but most are deprecated 168 / "i-klingon" ; in favor of more modern 169 / "i-lux" ; subtags or subtag 170 / "i-mingo" ; combination 171 / "i-navajo" 172 / "i-pwn" 173 / "i-tao" 174 / "i-tay" 175 / "i-tsu" 176 / "sgn-BE-FR" 177 / "sgn-BE-NL" 178 / "sgn-CH-DE" 180 regular = "art-lojban" ; these tags match the 'langtag' 181 / "cel-gaulish" ; production, but their subtags 182 / "no-bok" ; are not extended language 183 / "no-nyn" ; or variant subtags: their meaning 184 / "zh-guoyu" ; is defined by their registration 185 / "zh-hakka" ; and all of these are deprecated 186 / "zh-min" ; in favor of a more modern 187 / "zh-min-nan" ; subtag or sequence of subtags 188 / "zh-xiang" 190 alphanum = (ALPHA / DIGIT) ; letters and numbers 192 Figure 1: Language Tag ABNF 194 For examples of language tags, see Appendix B. 196 All subtags have a maximum length of eight characters and whitespace 197 is not permitted in a language tag. There is a subtlety in the ABNF 198 production 'variant': a variant starting with a digit has a minimum 199 length of four characters, while those starting with a letter have a 200 minimum length of five characters. 202 Although [RFC5234] refers to octets, the language tags described in 203 this document are sequences of characters from the US-ASCII [ISO646] 204 repertoire. Language tags MAY be used in documents and applications 205 that use other encodings, so long as these encompass the relevant 206 part of the US-ASCII repertoire. An example of this would be an XML 207 document that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 209 2.1.1. Formatting of Language Tags 211 At all times, language tags and their subtags, including private-use 212 and extensions, are to be treated as case insensitive: there exist 213 conventions for the capitalization of some of the subtags, but these 214 MUST NOT be taken to carry meaning. 216 Thus, the tag "mn-Cyrl-MN" is not distinct from "MN-cYRL-mn" or "mN- 217 cYrL-Mn" (or any other combination), and each of these variations 218 conveys the same meaning: Mongolian written in the Cyrillic script as 219 used in Mongolia. 221 The ABNF syntax also does not distinguish between upper and 222 lowercase: the uppercase US-ASCII letters in the range 'A' through 223 'Z' are always considered equivalent and mapped directly to their US- 224 ASCII lowercase equivalents in the range 'a' through 'z'. So the tag 225 "I-AMI" is considered equivalent to that value "i-ami" in the 226 'irregular' production. 228 Although case distinctions do not carry meaning in language tags, 229 consistent formatting and presentation of language tags will aid 230 users. The format of subtags in the registry is RECOMMENDED as the 231 form to use in language tags. This format generally corresponds to 232 the common conventions for the various ISO standards from which the 233 subtags are derived. 235 These conventions include: 237 o [ISO639-1] recommends that language codes be written in lowercase 238 ('mn' Mongolian). 240 o [ISO15924] recommends that script codes use lowercase with the 241 initial letter capitalized ('Cyrl' Cyrillic). 243 o [ISO3166-1] recommends that country codes be capitalized ('MN' 244 Mongolia). 246 An implementation can reproduce this format without accessing the 247 registry as follows: All subtags, including extension and private use 248 subtags, use lowercase letters, with two exceptions: two-letter and 249 four-letter subtags that neither appear at the start of the tag nor 250 occur after singletons. Such two-letter subtags are all uppercase 251 (as in the tags "en-CA-x-ca" or "sgn-BE-FR") and four-letter subtags 252 are titlecase (as in the tag "az-Latn-x-latn"). 254 Note: Case folding of ASCII letters in certain locales, unless 255 carefully handled, sometimes produces non-ASCII character values. 256 The Unicode Character Database file "SpecialCasing.txt" defines the 257 specific cases that are known to cause problems with this. In 258 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 259 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 260 Implementers SHOULD specify a locale-neutral casing operation to 261 ensure that case folding of subtags does not produce this value, 262 which is illegal in language tags. For example, if one were to 263 uppercase the region subtag 'in' using Turkish locale rules, the 264 sequence U+0130 U+004E would result instead of the expected 'IN'. 266 2.2. Language Subtag Sources and Interpretation 268 The namespace of language tags and their subtags is administered by 269 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 270 the rules in Section 5 of this document. The Language Subtag 271 Registry maintained by IANA is the source for valid subtags: other 272 standards referenced in this section provide the source material for 273 that registry. 275 Terminology used in this document: 277 o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or 278 "az-Arab-IR". Examples of tags in this document are enclosed in 279 double-quotes ("en-US"). 281 o "Subtag" refers to a specific section of a tag, delimited by 282 hyphen, such as the subtags 'zh', 'Hant', and 'CN' in the tag "zh- 283 Hant-CN". Examples of subtags in this document are enclosed in 284 single quotes ('Hant'). 286 o "Code" refers to values defined in external standards (and which 287 are used as subtags in this document). For example, 'Hant' is an 288 [ISO15924] script code that was used to define the 'Hant' script 289 subtag for use in a language tag. Examples of codes in this 290 document are enclosed in single quotes ('en', 'Hant'). 292 Language tags are designed so that each subtag type has unique length 293 and content restrictions. These make identification of the subtag's 294 type possible, even if the content of the subtag itself is 295 unrecognized. This allows tags to be parsed and processed without 296 reference to the latest version of the underlying standards or the 297 IANA registry and makes the associated exception handling when 298 parsing tags simpler. 300 Some of the subtags in the IANA registry do not come from an 301 underlying standard. These can only appear in specific positions in 302 a tag: they can only occur as primary language subtags or as variant 303 subtags. 305 Sequences of private use and extension subtags MUST occur at the end 306 of the sequence of subtags and MUST NOT be interspersed with subtags 307 defined elsewhere in this document. These sequences are introduced 308 by single-character subtags, which are reserved as follows: 310 o The single-letter subtag 'x' introduces a sequence of private use 311 subtags. The interpretation of any private use subtags is defined 312 solely by private agreement and is not defined by the rules in 313 this section or in any standard or registry defined in this 314 document. 316 o The single-letter subtag 'i' is used by some grandfathered tags, 317 such as "i-default", where it always appears in the first position 318 and cannot be confused with an extension. 320 o All other single-letter and single-digit subtags are reserved to 321 introduce standardized extension subtag sequences as described in 322 Section 3.7. 324 2.2.1. Primary Language Subtag 326 The primary language subtag is the first subtag in a language tag and 327 cannot be omitted, with two exceptions: 329 o The single-character subtag 'x' as the primary subtag indicates 330 that the language tag consists solely of subtags whose meaning is 331 defined by private agreement. For example, in the tag "x-fr-CH", 332 the subtags 'fr' and 'CH' do not represent the French language or 333 the country of Switzerland (or any other value in the IANA 334 registry) unless there is a private agreement in place to do so. 335 See Section 4.6. 337 o The single-character subtag 'i' is used by some grandfathered tags 338 (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 339 grandfathered tags have a primary language subtag in their first 340 position.) 342 The following rules apply to the primary language subtag: 344 1. Two-character primary language subtags were defined in the IANA 345 registry according to the assignments found in the standard "ISO 346 639-1:2002, Codes for the representation of names of languages -- 347 Part 1: Alpha-2 code" [ISO639-1], or using assignments 348 subsequently made by the ISO 639-1 registration authority (RA) or 349 governing standardization bodies. 351 2. Three-character primary language subtags in the IANA registry 352 were defined according to the assignments found in one of these 353 additional ISO 639 parts or assignments subsequently made by the 354 relevant ISO 639 registration authorities or governing 355 standardization bodies: 357 A. "ISO 639-2:1998 - Codes for the representation of names of 358 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2] 360 B. "ISO 639-3:2007 - Codes for the representation of names of 361 languages -- Part 3: Alpha-3 code for comprehensive coverage 362 of languages" [ISO639-3] 364 C. "ISO 639-5:2008 - Codes for the representation of names of 365 languages -- Part 5: Alpha-3 code for language families and 366 groups" [ISO639-5] 368 3. The subtags in the range 'qaa' through 'qtz' are reserved for 369 private use in language tags. These subtags correspond to codes 370 reserved by ISO 639-2 for private use. These codes MAY be used 371 for non-registered primary language subtags (instead of using 372 private use subtags following 'x-'). Please refer to Section 4.6 373 for more information on private use subtags. 375 4. Four-character language subtags are reserved for possible future 376 standardization. 378 5. Any language subtags of 5 to 8 characters in length in the IANA 379 registry were defined via the registration process in Section 3.5 380 and MAY be used to form the primary language subtag. An example 381 of what such a registration might include: one of the 382 grandfathered IANA registrations is "i-enochian". The subtag 383 'enochian' could be registered in the IANA registry as a primary 384 language subtag (assuming that ISO 639 does not register this 385 language first), making tags such as "enochian-AQ" and "enochian- 386 Latn" valid. 388 At the time this document was created, there were no examples of 389 this kind of subtag and future registrations of this type are 390 discouraged: primary languages are strongly RECOMMENDED for 391 registration with ISO 639, and proposals rejected by ISO 639/ 392 RA-JAC will be closely scrutinized before they are registered 393 with IANA. 395 6. Other values MUST NOT be assigned to the primary subtag except by 396 revision or update of this document. 398 When languages have both an ISO 639-1 two-character code and a three 399 character code (assigned by ISO 639-2, ISO 639-3, or ISO 639-5), only 400 the ISO 639-1 two-character code is defined in the IANA registry. 402 When languages that have no ISO 639-1 two-character code and for 403 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 404 (Bibliographic) codes differ, only the Terminology code is defined in 405 the IANA registry. At the time this document was created, all 406 languages that had both kinds of three-character code were also 407 assigned a two-character code; it is expected that future assignments 408 of this nature will not occur. 410 In order to avoid instability in the canonical form of tags, if a 411 two-character code is added to ISO 639-1 for a language for which a 412 three-character code was already included in either ISO 639-2 or ISO 413 639-3, the two-character code MUST NOT be registered. See 414 Section 3.4. 416 For example, if some content were tagged with 'haw' (Hawaiian), which 417 currently has no two-character code, the tag would not need to be 418 changed if ISO 639-1 were to assign a two-character code to the 419 Hawaiian language at a later date. 421 To avoid these problems with versioning and subtag choice (as 422 experienced during the transition between RFC 1766 and RFC 3066), as 423 well as to ensure the canonical nature of subtags defined by this 424 document, the ISO 639 Registration Authority Joint Advisory Committee 425 (ISO 639/RA-JAC) has included the following statement in 426 [iso639.prin]: 428 "A language code already in ISO 639-2 at the point of freezing ISO 429 639-1 shall not later be added to ISO 639-1. This is to ensure 430 consistency in usage over time, since users are directed in 431 Internet applications to employ the alpha-3 code when an alpha-2 432 code for that language is not available." 434 2.2.2. Extended Language Subtags 436 Extended language subtags are used to identify certain specially- 437 selected languages that, for various historical and compatibility 438 reasons, are closely identified with or tagged using an existing 439 primary language subtag. Extended language subtags are always used 440 with their enclosing primary language subtag (indicated with a 441 'Prefix' field in the registry) when used to form the language tag. 442 All languages that have an extended language subtag in the registry 443 also have an identical primary language subtag record in the 444 registry. This primary language subtag is RECOMMENDED for forming 445 the language tag. The following rules apply to the extended language 446 subtags: 448 1. Extended language subtags consist solely of three-letter subtags. 449 All extended language subtag records defined in the registry were 450 defined according to the assignments found in [ISO639-3]. 451 Language collections and groupings, such as defined in [ISO639-5] 452 are specifically excluded from being extended language subtags. 454 2. Extended language subtag records MUST include exactly one 455 'Prefix' field indicating an appropriate subtag or sequence of 456 subtags for that extended language subtag. 458 3. Extended language subtag records MUST include a 'Preferred- 459 Value'. The 'Preferred-Value' and 'Subtag' fields MUST be 460 identical. 462 4. Although the ABNF production 'extlang' permits up to three 463 extended language tags in the language tag, extended language 464 subtags MUST NOT include another extended language subtag in 465 their Prefix. That is, the second and third extended language 466 subtag positions in a language tag are permanently reserved and 467 tags that include subtags in that position are invalid. 469 For example, the macrolanguage Chinese ('zh') encompasses a number of 470 languages. For compatibility reasons, each of these languages has 471 both a primary and extended language subtag in the registry. A few 472 selected examples of these include Gan Chinese ('gan'), Cantonese 473 Chinese ('yue') and Mandarin Chinese ('cmn'). Each is encompassed by 474 the macrolanguage 'zh' (Chinese). Therefore, they each have the 475 prefix "zh" in their registry records. Thus Gan Chinese is 476 represented with tags beginning "zh-gan" or "gan"; Cantonese with 477 tags beginning either "yue" or "zh-yue"; and Mandarin Chinese with 478 "zh-cmn" or "cmn". The language subtag 'zh' can still be used 479 without an extended language subtag to label a resource as some 480 unspecified variety of Chinese, while the primary language subtag 481 ('gan', 'yue', 'cmn') is preferred to using the extended language 482 form ("zh-gan", "zh-yue", "zh-cmn"). 484 2.2.3. Script Subtag 486 Script subtags are used to indicate the script or writing system 487 variations that distinguish the written forms of a language or its 488 dialects. The following rules apply to the script subtags: 490 1. Script subtags MUST follow any primary and extended language 491 subtags and MUST precede any other type of subtag. 493 2. Script subtags consist of four letters and were defined according 494 to [ISO15924]--"Codes for the representation of the names of 495 scripts": alpha-4 script codes, or subsequently assigned by the 496 ISO 15924 registration authority or governing standardization 497 bodies, denoting the script or writing system used in conjunction 498 with this language. Only codes assigned by ISO 15924 will be 499 considered for registration. 501 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 502 use in language tags. These subtags correspond to codes reserved 503 by ISO 15924 for private use. These codes MAY be used for non- 504 registered script values. Please refer to Section 4.6 for more 505 information on private use subtags. 507 4. There MUST be at most one script subtag in a language tag, and 508 the script subtag SHOULD be omitted when it adds no 509 distinguishing value to the tag or when the primary or extended 510 language subtag's record in the subtag registry includes a 511 'Suppress-Script' field listing the applicable script subtag. 513 For example: "sr-Latn" represents Serbian written using the Latin 514 script. 516 2.2.4. Region Subtag 518 Region subtags are used to indicate linguistic variations associated 519 with or appropriate to a specific country, territory, or region. 520 Typically, a region subtag is used to indicate variations such as 521 regional dialects or usage, or region-specific spelling conventions. 522 It can also be used to indicate that content is expressed in a way 523 that is appropriate for use throughout a region, for instance, 524 Spanish content tailored to be useful throughout Latin America. 526 The following rules apply to the region subtags: 528 1. Region subtags MUST follow any primary language, extended 529 language, or script subtags and MUST precede any other type of 530 subtag. 532 2. Two-letter region subtags were defined according to the 533 assignments found in [ISO3166-1] ("Codes for the representation 534 of names of countries and their subdivisions -- Part 1: Country 535 codes") using the list of alpha-2 country codes, or using 536 assignments subsequently made by the ISO 3166-1 maintenance 537 agency or governing standardization bodies. In addition, the 538 codes that are "exceptionally reserved" (as opposed to 539 "assigned") in ISO 3166-1 were also defined in the registry, with 540 the exception of 'UK', which is an exact synonym for the assigned 541 code 'GB'. 543 3. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 544 reserved for private use in language tags. These subtags 545 correspond to codes reserved by ISO 3166 for private use. These 546 codes MAY be used for private use region subtags (instead of 547 using a private use subtag sequence). Please refer to 548 Section 4.6 for more information on private use subtags. 550 4. Three-character region subtags consist solely of digit (number) 551 characters and were defined according to the assignments found in 552 UN Standard Country or Area Codes for Statistical Use [UN_M.49] 553 or assignments subsequently made by the governing standards body. 554 Not all of the UN M.49 codes are defined in the IANA registry. 555 The following rules define which codes are entered into the 556 registry as valid subtags: 558 A. UN numeric codes assigned to 'macro-geographical 559 (continental)' or sub-regions MUST be registered in the 560 registry. These codes are not associated with an assigned 561 ISO 3166-1 alpha-2 code and represent supra-national areas, 562 usually covering more than one nation, state, province, or 563 territory. 565 B. UN numeric codes for 'economic groupings' or 'other 566 groupings' MUST NOT be registered in the IANA registry and 567 MUST NOT be used to form language tags. 569 C. When ISO 3166-1 reassigns a code formerly used for one 570 country or area to another country or area and that code 571 already is present in the registry, the UN numeric code for 572 that country or area MUST be registered in the registry as 573 described in Section 3.4 and MUST be used to form language 574 tags that represent the country or region for which it is 575 defined (rather than the recycled ISO 3166-1 code). 577 D. UN numeric codes for countries or areas for which there is an 578 associated ISO 3166-1 alpha-2 code in the registry MUST NOT 579 be entered into the registry and MUST NOT be used to form 580 language tags. Note that the ISO 3166-based subtag in the 581 registry MUST actually be associated with the UN M.49 code in 582 question. 584 E. UN numeric codes and ISO 3166-1 alpha-2 codes for countries 585 or areas listed as eligible for registration in Section 4 of 586 [RFC4645] but not presently registered MAY be entered into 587 the IANA registry via the process described in Section 3.5. 588 Once registered, these codes MAY be used to form language 589 tags. 591 F. All other UN numeric codes for countries or areas that do not 592 have an associated ISO 3166-1 alpha-2 code MUST NOT be 593 entered into the registry and MUST NOT be used to form 594 language tags. For more information about these codes, see 595 Section 3.4. 597 5. The alphanumeric codes in Appendix X of the UN document MUST NOT 598 be entered into the registry and MUST NOT be used to form 599 language tags. (At the time this document was created, these 600 values matched the ISO 3166-1 alpha-2 codes.) 602 6. There MUST be at most one region subtag in a language tag and the 603 region subtag MAY be omitted, as when it adds no distinguishing 604 value to the tag. 606 For example: 608 "de-AT" represents German ('de') as used in Austria ('AT'). 610 "sr-Latn-RS" represents Serbian ('sr') written using Latin script 611 ('Latn') as used in Serbia ('RS'). 613 "es-419" represents Spanish ('es') appropriate to the UN-defined 614 Latin America and Caribbean region ('419'). 616 2.2.5. Variant Subtags 618 Variant subtags are used to indicate additional, well-recognized 619 variations that define a language or its dialects that are not 620 covered by other available subtags. The following rules apply to the 621 variant subtags: 623 1. Variant subtags MUST follow any primary language, extended 624 language, script, or region subtags, and MUST precede any 625 extension or private use subtag sequences. 627 2. Variant subtags, as a collection, are not associated with any 628 particular external standard. The meaning of variant subtags in 629 the registry is defined in the course of the registration process 630 defined in Section 3.5. Note that any particular variant subtag 631 might be associated with some external standard. However, 632 association with a standard is not required for registration. 634 3. More than one variant MAY be used to form the language tag. 636 4. Variant subtags MUST be registered with IANA according to the 637 rules in Section 3.5 of this document before being used to form 638 language tags. In order to distinguish variants from other types 639 of subtags, registrations MUST meet the following length and 640 content restrictions: 642 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 643 at least five characters long. 645 2. Variant subtags that begin with a digit (0-9) MUST be at 646 least four characters long. 648 5. The same variant subtag MUST NOT be used more than once within a 649 language tag. 651 * For example, the tag "de-DE-1901-1901" is not valid. 653 Variant subtag records in the language subtag registry MAY include 654 one or more 'Prefix' fields. The 'Prefix' indicates a sequence of 655 subtags that would make a suitable prefix (with other subtags, as 656 appropriate) in forming a language tag with the variant. That is, 657 each of the subtags in the prefix SHOULD appear, in order, before the 658 variant. For example, the subtag 'nedis' has a Prefix of "sl", 659 making it suitable for forming language tags such as "sl-nedis" and 660 "sl-IT-nedis", but not suitable for use in a tag such as "zh-nedis" 661 or "it-IT-nedis". 663 Most variants that share a prefix are mutually exclusive. For 664 example, the German orthographic variations '1996' and '1901' SHOULD 665 NOT be used in the same tag, as they represent the dates of different 666 spelling reforms. A variant that can meaningfully be used in 667 combination with another variant SHOULD include a 'Prefix' field in 668 its registry record that lists that other variant. For example, if 669 another German variant 'example' were created that made sense to use 670 with '1996', then 'example' should include two Prefix fields: "de" 671 and "de-1996". 673 For example: 675 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 677 "de-CH-1996" represents German as used in Switzerland and as 678 written using the spelling reform beginning in the year 1996 C.E. 680 2.2.6. Extension Subtags 682 Extensions provide a mechanism for extending language tags for use in 683 various applications. They are intended to identify information 684 which is commonly used in association with languages or language 685 tags, but which is not part of language identification. See 686 Section 3.7. The following rules apply to extensions: 688 1. An extension MUST follow at least a primary language subtag. 689 That is, a language tag cannot begin with an extension. 690 Extensions extend language tags, they do not override or replace 691 them. For example, "a-value" is not a well-formed language tag, 692 while "de-a-value" is. Note that extensions cannot be used in 693 tags that are entirely private use (that is, tags starting with 694 "x-"). 696 2. Extension subtags are separated from the other subtags defined in 697 this document by a single-character subtag (called a 698 "singleton"). The singleton MUST be one allocated to a 699 registration authority via the mechanism described in Section 3.7 700 and MUST NOT be the letter 'x', which is reserved for private use 701 subtag sequences. 703 3. Each singleton subtag MUST appear at most one time in each tag 704 (other than as a private use subtag). That is, singleton subtags 705 MUST NOT be repeated. For example, the tag "en-a-bbb-a-ccc" is 706 invalid because the subtag 'a' appears twice. Note that the tag 707 "en-a-bbb-x-a-ccc" is valid because the second appearance of the 708 singleton 'a' is in a private use sequence. 710 4. Extension subtags MUST meet whatever requirements are set by the 711 document that defines their singleton prefix and whatever 712 requirements are provided by the maintaining authority. Note 713 that there might not be a registry of these subtags and 714 validating processors are not required to validate extensions. 716 5. Each extension subtag MUST be from two to eight characters long 717 and consist solely of letters or digits, with each subtag 718 separated by a single '-'. Case distinctions are ignored in 719 extensions (as with any language subtag) and normalized subtags 720 of this type are expected to be in lowercase. 722 6. Each singleton MUST be followed by at least one extension subtag. 723 For example, the tag "tlh-a-b-foo" is invalid because the first 724 singleton 'a' is followed immediately by another singleton 'b'. 726 7. Extension subtags MUST follow all primary language, extended 727 language, script, region, and variant subtags in a tag and MUST 728 precede any private-use subtag sequences. 730 8. All subtags following the singleton and before another singleton 731 are part of the extension. Example: In the tag "fr-a-Latn", the 732 subtag 'Latn' does not represent the script subtag 'Latn' defined 733 in the IANA Language Subtag Registry. Its meaning is defined by 734 the extension 'a'. 736 9. In the event that more than one extension appears in a single 737 tag, the tag SHOULD be canonicalized as described in Section 4.5, 738 by ordering the various extension sequences into case-insensitive 739 ASCII order. 741 For example, if an extention were defined for the singleton 'r' and 742 it defined the subtags shown, then the following tag would be a valid 743 example: "en-Latn-GB-boont-r-extended-sequence-x-private" 745 2.2.7. Private Use Subtags 747 Private use subtags are used to indicate distinctions in language 748 important in a given context by private agreement. The following 749 rules apply to private use subtags: 751 1. Private use subtags are separated from the other subtags defined 752 in this document by the reserved single-character subtag 'x'. 754 2. Private use subtags MUST conform to the format and content 755 constraints defined in the ABNF for all subtags, that is, they 756 MUST consist solely of letters and digits and not exceed eight 757 characters in length. 759 3. Private use subtags MUST follow all primary language, extended 760 language, script, region, variant, and extension subtags in the 761 tag. Another way of saying this is that all subtags following 762 the singleton 'x' MUST be considered private use. Example: The 763 subtag 'US' in the tag "en-x-US" is a private use subtag. 765 4. A tag MAY consist entirely of private use subtags. 767 5. No source is defined for private use subtags. Use of private use 768 subtags is by private agreement only. 770 6. Private use subtags are NOT RECOMMENDED where alternatives exist 771 or for general interchange. See Section 4.6 for more information 772 on private use subtag choice. 774 For example, suppose a group of scholars are studying some texts in 775 medieval Greek. They might agree to use some collection of private- 776 use subtags to identify different styles of writing in the texts. 777 For example, they might use 'el-x-koine' for documents in the 778 "common" style while using 'el-x-attic' for other documents that 779 mimic the Attic style. These subtags would not be recognized by 780 outside processes or systems, but might be useful in categorizing 781 various texts for study by those in the group. 783 2.2.8. Grandfathered and Redundant Registrations 785 Prior to RFC 4646, whole language tags were registered according to 786 the rules in RFC 1766 and/or RFC 3066. All of these registered tags 787 remain valid as language tags. 789 Many of these registered tags were made redundant by the advent of 790 either RFC 4646 or this document. A redundant tag is a grandfathered 791 registration whose individual subtags appear with the same semantic 792 meaning in the registry. For example, the tag "zh-Hant" (Traditional 793 Chinese) can now be composed from the subtags 'zh' (Chinese) and 794 'Hant' (Han script traditional variant). These redundant tags are 795 maintained in the registry as records of type "redundant", mostly as 796 a matter of historical curiousity. 798 The remainder of the previously registered tags are "grandfathered". 799 These tags are classified into two groups: 'regular' and 'irregular'. 801 Grandfathered tags that (appear to) match the 'langtag' production in 802 Figure 1 are considered 'regular' grandfathered tags. These tags 803 either contain subtags that do not individually appear in the 804 registry, or their subtags appear but with a different semantic 805 meaning: each tag, in its entirety, represents a language or 806 collection of languages. 808 Grandfathered tags that do not match the 'langtag' production in the 809 ABNF and would otherwise be invalid are considered 'irregular' 810 grandfathered tags. With the exception of "en-GB-oed", which is a 811 variant of "en-GB", each of them, in its entirety, represents a 812 language. 814 Many of the grandfathered tags have been superseded by the subsequent 815 addition of new subtags: each superseded record contains a Preferred- 816 Value field that ought to be used to form language tags representing 817 that value. For example, the tag "art-lojban" is superseded by the 818 primary language subtag 'jbo'. 820 2.2.9. Classes of Conformance 822 Implementations sometimes need to describe their capabilities with 823 regard to the rules and practices described in this document. Tags 824 can be checked or verified in a number of ways, but two particular 825 classes of tag conformance are formally defined here. 827 A tag is considered "well-formed" if it conforms to the ABNF 828 (Section 2.1). Language tags may be well-formed in terms of syntax 829 but not valid in terms of content. However, many operations 830 involving language tags work well without knowing anything about the 831 meaning or validity of the subtags. 833 A tag is considered "valid" if it satisfies these conditions: 835 o The tag is well-formed. 837 o The tag is either in the list of grandfathered tags or all of its 838 primary language, extended language, script, region, and variant 839 subtags appear in the IANA language subtag registry as of the 840 particular registry date. 842 o There are no duplicate variant subtags. 844 o There are no duplicate singleton (extension) subtags. 846 Note that a tag's validity depends on the date of the registry used 847 to validate the tag. A more recent copy of the registry might 848 contain a subtag that an older version does not. 850 A tag is considered "valid" for a given extension (Section 3.7) (as 851 of a particular version, revision, and date) if it meets the criteria 852 for "valid" above and also satisfies this condition: 854 Each subtag used in the extension part of the tag is valid 855 according to the extension. 857 Older specifications or language tag implementations sometimes 858 reference [RFC3066]. A wider array of tags was considered 'well- 859 formed' under that document. Any tags that were valid for use under 860 RFC 3066 are both 'well-formed' and 'valid' under this document's 861 syntax; only invalid or illegal tags were well-formed by the early 862 definition but no longer are. The language tag syntax under RFC 3066 863 was: 865 obs-language-tag = primary-subtag *( "-" subtag ) 866 primary-subtag = 1*8ALPHA 867 subtag = 1*8(ALPHA / DIGIT) 869 Figure 2: RFC 3066 Language Tag Syntax 871 Subtags designated for private use as well as private-use sequences 872 introduced by the 'x' subtag are available for cases in which no 873 assigned subtags are available and registration is not a suitable 874 option. For example, one might use a tag such as "no-QQ", where 'QQ' 875 is one of a range of private-use ISO 3166-1 codes to indicate an 876 otherwise-undefined region. Users MUST NOT assign language tags that 877 use subtags that do not appear in the registry other than in private- 878 use sequences (such the subtag 'personal' in the tag "en-x- 879 personal"). Besides not being 'valid', the user also risks collision 880 with a future possible assignment or registrations. 882 Note well: although the 'Language-Tag' production appearing in this 883 document is functionally equivalent to the one in [RFC4646], it has 884 been changed to prevent certain errors in well-formedness arising 885 from the old 'grandfathered' production. This version of the ABNF is 886 RECOMMENDED as a replacement for the older version. 888 3. Registry Format and Maintenance 890 The IANA Language Subtag Registry ("the registry") contains a 891 comprehensive list of all of the subtags valid in language tags. 892 This allows implementers a straightforward and reliable way to 893 validate language tags. The registry will be maintained so that, 894 except for extension subtags, it is possible to validate all of the 895 subtags that appear in a language tag under the provisions of this 896 document or its revisions or successors. In addition, the meaning of 897 the various subtags will be unambiguous and stable over time. (The 898 meaning of private use subtags, of course, is not defined by the 899 registry.) 901 This section defines the registry along with the maintenance and 902 update procedures associated with it, as well as a registry for 903 extensions to language tags (Section 3.7). 905 3.1. Format of the IANA Language Subtag Registry 907 The IANA Language Subtag Registry is a machine-readable file in the 908 format described in this section, plus copies of the registration 909 forms approved in accordance with the process described in 910 Section 3.5. 912 The existing registration forms for grandfathered and redundant tags 913 taken from RFC 3066 have been maintained as part of the obsolete RFC 914 3066 registry. The subtags added to the registry by either [RFC4645] 915 or [draft-4645bis] do not have separate registration forms (so no 916 forms are archived for these additions). 918 3.1.1. File Format 920 The registry is a [Unicode] text file, using the UTF-8 [RFC3629] 921 character encoding, and consists of a series of records stored in a 922 format based on "record-jar" (described in [record-jar]). Each 923 record, in turn, consists of a series of fields that describe the 924 various subtags and tags. 926 Each field can be considered a single, logical line of characters. 927 Each field contains a 'field-name' and a 'field-body'. These are 928 separated by a 'field-separator'. The field-separator is a COLON 929 character (%x3A) plus any surrounding whitespace. Each field is 930 terminated by the newline sequence CRLF. The text in each field MUST 931 be in Unicode Normalization Form C (NFC). 933 A collection of fields forms a 'record'. Records are separated by 934 lines containing only the sequence "%%" (%x25.25). 936 Although fields are logically a single line of text, each line of 937 text in the file format is limited to 72 bytes in length. To 938 accommodate this, the field-body can be split into a multiple-line 939 representation; this is called "folding". Folding is done according 940 to customary conventions for line-wrapping. This is typically on 941 whitespace boundaries, but can occur between other characters when 942 the value does not include spaces, such as when a language does not 943 use whitespace between words. In any event, there MUST NOT be breaks 944 inside a multibyte UTF-8 sequence nor in the middle of a combining 945 character sequence. For more information, see [UAX14]. 947 Although the file format uses the UTF-8 encoding, fields are 948 restricted to the printable characters from the US-ASCII [ISO646] 949 repertoire unless otherwise indicated in the description of a 950 specific field-name (Section 3.1.2). 952 The format of the registry is described by the following ABNF (per 953 [RFC5234]): 955 registry = record *("%%" CRLF record) 956 record = 1*field 957 field = ( field-name field-sep field-body CRLF ) 958 field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] 959 field-sep = *SP ":" *SP 960 field-body = *([[*SP CRLF] 1*SP] 1*CHARS) 961 CHARS = (%x21-10FFFF) ; Unicode code points 963 Figure 3: Registry Format ABNF 965 The sequence '..' (%x2E.2E) in a field-body denotes a range of 966 values. Such a range represents all subtags of the same length that 967 are in alphabetic or numeric order within that range, including the 968 values explicitly mentioned. For example 'a..c' denotes the values 969 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 970 '13'. 972 All fields whose field-body contains a date value use the "full-date" 973 format specified in [RFC3339]. For example: "2004-06-28" represents 974 June 28, 2004, in the Gregorian calendar. 976 3.1.2. Record and Field Definitions 978 There are three types of records in the registry: "File-Date", 979 "Subtag", and "Tag". 981 The first record in the registry is always the "File-Date" record. 982 This record occurs only once in the file and contains a single field 983 whose field-name is "File-Date". The field-body of this record 984 contains the last modification date of this copy of the registry, 985 making it possible to compare different versions of the registry. 986 The registry on the IANA website is the most current. Versions with 987 an older date than that one are not up-to-date. 989 File-Date: 2004-06-28 990 %% 992 Figure 4: Example of the File-Date Record 994 Subsequent records contain multiple fields and represent information 995 about either subtags or tags. Both types of record have identical 996 structure, except that "Subtag" records contain a field with a field- 997 name of "Subtag", while, unsurprisingly, "Tag" records contain a 998 field with a field-name of "Tag". Field-names MUST occur no more 999 than once per record, with the exception of the 'Description', 1000 'Comments', and sometimes the 'Prefix' field. 1002 Each record MUST contain at least one of each of the following 1003 fields: 1005 o 'Type' 1007 * Type's field-body MUST consist of one of the following strings: 1008 "language", "extlang", "script", "region", "variant", 1009 "grandfathered", and "redundant", and denotes the type of tag 1010 or subtag. 1012 o Either 'Subtag' or 'Tag' 1014 * Subtag's field-body contains the subtag being defined. This 1015 field MUST appear in all records whose 'Type' has one of these 1016 values: "language", "extlang", "script", "region", or 1017 "variant". 1019 * Tag's field-body contains a complete language tag. This field 1020 MUST appear in all records whose 'Type' has one of these 1021 values: "grandfathered" or "redundant". If the 'Type' is 1022 "grandfathered", then the 'Tag' field-body will be one of the 1023 tags listed in either the 'regular' or 'irregular' production 1024 in found in Section 2.1. 1026 o Description 1028 * Description's field-body contains a non-normative description 1029 of the subtag or tag. 1031 o Added 1033 * Added's field-body contains the date the record was registered 1034 or, in the case of grandfathered or redundant tags, the date 1035 the corresponding tag was registered under the rules of 1036 [RFC1766] or [RFC3066]. 1038 Each record MAY also contain the following fields: 1040 o Deprecated 1042 * Deprecated's field-body contains the date the record was 1043 deprecated. In some cases this value is earlier than that of 1044 the 'Added' field in the same record. That is, the date of 1045 deprecation preceded the addition of the record to the 1046 registry. 1048 o Preferred-Value 1050 * Preferred-Value's field body contains a canonical mapping from 1051 this record's value to a modern equivalent that is preferred in 1052 its place. Depending on the value of the 'Type' field, this 1053 value can take different forms: 1055 + For fields of type 'language', 'Preferred-Value' contains 1056 the primary language subtag that is preferred when forming 1057 the language tag. 1059 + For fields of type 'script', 'region', or 'variant', 1060 'Preferred-Value' contains the subtag of the same type that 1061 is preferred for forming the language tag. 1063 + For fields of type 'extlang', 'grandfathered', or 1064 'redundant', 'Preferred-Value' contains an "extended 1065 language range" ([RFC4647]) that is preferred for forming 1066 the language tag. That is, each of the subtags that appears 1067 in the value MUST appear in the replacement tag; additional 1068 fields can be included in a language tag as described 1069 elsewhere in this document. For example, the replacement 1070 for the grandfathered tag "zh-min-nan" (Min Nan Chinese) is 1071 "nan", which can be used as the basis for tags such as "nan- 1072 Hant" or "nan-TW" (note that the extended language subtag 1073 form such as "zh-nan-Hant" or "zh-nan-TW" can also be used). 1075 o Prefix 1077 * Prefix's field-body contains an "extended language range" 1078 (basically, a collection of subtags, see [RFC4647]) which 1079 SHOULD be used with this subtag when forming the language tag. 1080 The subtags in the prefix MUST appear before the subtag in 1081 Prefix's record. The Prefix MUST NOT include the wildcard '*'. 1082 This field MUST appear only in records whose 'Type' field-body 1083 is either 'extlang' or 'variant'. 1085 For example, the variant 'nedis' (Nadiza dialect) has a 1086 'Prefix' of "sl" (Slovenian), meaning that tags such as "sl- 1087 nedis" and "sl-IT-nedis" are appropriate, while the tag "is- 1088 nedis" (Icelandic, Nadiza dialect) is not. 1090 o Suppress-Script 1092 * Suppress-Script's field-body contains a script subtag that 1093 SHOULD NOT be used to form language tags with the associated 1094 primary or extended language subtag. This field MUST appear 1095 only in records whose 'Type' field-body is "language" or 1096 "extlang". See Section 4.1. 1098 o Macrolanguage 1100 * Macrolanguage's field-body contains a primary language subtag 1101 defined by ISO 639 as the "macrolanguage" that encompasses this 1102 language subtag. This field MUST appear only in records whose 1103 'Type' field-body is either "language" or "extlang". 1105 o Scope 1107 * Scope's field-body contains information about a primary or 1108 extended language subtag indicating the type of language code 1109 according to ISO 639. The values permitted in this field are 1110 "macrolanguage", "collection", "special" and "private-use". 1111 This field only appears in records whose 'Type' field-body is 1112 either "language" or "extlang". When this field is omitted, 1113 the language is an individual language. 1115 o Comments 1117 * Comments's field-body contains additional information about the 1118 subtag, as deemed appropriate for understanding the registry 1119 and implementing language tags using the subtag or tag. 1121 Future versions of this document might add additional fields to the 1122 registry; implementations SHOULD ignore fields found in the registry 1123 that are not defined in this document. 1125 3.1.3. Type Field 1127 The field 'Type' contains the string identifying the record type it 1128 appears in. Values for the 'Type' field-body are: "language" 1129 (Section 2.2.1); "extlang" (Section 2.2.2); "script" (Section 2.2.3); 1130 "region" (Section 2.2.4); "variant" (Section 2.2.5); "grandfathered" 1131 or "redundant" (Section 2.2.8). 1133 3.1.4. Subtag and Tag Fields 1135 The field 'Subtag' contains the subtag defined in the record. The 1136 field 'Tag' appears in records whose 'Type' is either 'grandfathered' 1137 or 'redundant' and contains a tag registered under [RFC3066]. 1139 The 'Subtag' field-body MUST follow the casing conventions described 1140 in Section 2.1.1. All subtags use lowercase letters in the field- 1141 body, with two exceptions: 1143 Subtags whose 'Type' field is 'script' (in other words, subtags 1144 defined by ISO 15924) MUST use titlecase. 1146 Subtags whose 'Type' field is 'region' (in other words, the non- 1147 numeric region subtags defined by ISO 3166-1) MUST use all 1148 uppercase. 1150 The 'Tag' field-body MUST be formatted according to the rules 1151 described in Section 2.1.1. 1153 3.1.5. Description Field 1155 The field 'Description' contains a description of the tag or subtag 1156 in the record. The 'Description' field MAY appear more than once per 1157 record. The 'Description' field MAY include the full range of 1158 Unicode characters. At least one of the 'Description' fields MUST be 1159 written or transcribed into the Latin script; additional 1160 'Description' fields MAY be in any script or language. 1162 The 'Description' field is used for identification purposes. 1163 Descriptions SHOULD contain all and only that information necessary 1164 to distinguish one subtag from others that it might be confused with. 1165 They are not intended to provide general background information, nor 1166 to provide all possible alternate names or designations. 1167 'Description' fields don't necessarily represent the actual native 1168 name of the item in the record, nor are any of the descriptions 1169 guaranteed to be in any particular language (such as English or 1170 French, for example). 1172 Descriptions in the registry that correspond to ISO 639, ISO 15924, 1173 ISO 3166-1, or UN M.49 codes are intended only to indicate the 1174 meaning of that identifier as defined in the source standard at the 1175 time it was added to the registry or as subsequently modified, within 1176 the bounds of the stability rules (Section 3.4), via subsequent 1177 registration. The 'Description' does not replace the content of the 1178 source standard itself. 'Description' fields are not intended to be 1179 the localized English names for the subtags. Localization or 1180 translation of language tag and subtag descriptions is out of scope 1181 of this document. 1183 For subtags taken from a source standard (such as ISO 639 or ISO 1184 15924), the 'Description' fields in the record are also initially 1185 taken from that source standard. Multiple descriptions in the source 1186 standard are split into separate 'Description' fields. The source 1187 standard's descriptions MAY be edited or modified, either prior to 1188 insertion or via the registration process, and additional or 1189 extraneous descriptions omitted or removed. Each 'Description' field 1190 MUST be unique within the record in which it appears and formatting 1191 variations of the same description SHOULD NOT occur in that specific 1192 record. For example, while the ISO 639-1 code 'fy' has both the 1193 description "Western Frisian" and and the description "Frisian, 1194 Western" in that standard, only one of these descriptions appears in 1195 the registry. 1197 To help ensure that users do not become confused about which subtag 1198 to use, 'Description' fields assigned to a record of any specific 1199 type ('language', 'extlang', 'script', and so on) MUST be unique 1200 within that given record type with the following exception: if a 1201 particular 'Description' field occurs in multiple records of a given 1202 type, then at most one of the records can omit the 'Deprecated' 1203 field; all deprecated records that share a 'Description' MUST have 1204 the same 'Preferred-Value'; and all non-deprecated records MUST be 1205 that 'Preferred-Value'. This means that two records of the same type 1206 that share a 'Description' are also semantically equivalent and no 1207 more than one record with a given 'Description' is preferred for that 1208 meaning. 1210 For example, consider the 'language' subtags 'zza' (Zaza) and 'diq' 1211 (Dimli). It so happens that 'zza' is a macrolanguage enclosing 'diq' 1212 and thus also has a description in ISO 639-3 of "Dimli". This 1213 description was edited to read "Dimli (macrolanguage)" in the 1214 registry record for 'zza' to prevent a collision. 1216 By contrast, the subtags 'he' and 'iw' share a 'Description' value of 1217 "Hebrew"; this is permitted because 'iw' is deprecated and its 1218 'Preferred-Value' is 'he'. 1220 For fields of type 'language', the first 'Description' field 1221 appearing in the Registry corresponds whenever possible to the 1222 Reference Name assigned by ISO 639-3. This helps facilitate cross- 1223 referencing between ISO 639 and the registry. 1225 When creating or updating a record due to the action of one of the 1226 source standards, the Language Subtag Reviewer MAY edit descriptions 1227 to correct irregularities in formatting (such as misspellings, 1228 inappropriate apostrophes or other punctuation, or excessive or 1229 missing spaces) prior to submitting the proposed record to the 1230 ietf-languages@iana.org list for consideration. 1232 3.1.6. Deprecated Field 1234 The field 'Deprecated' contains the date the record was deprecated 1235 and MAY be added, changed, or removed from any record via the 1236 maintenance process described in Section 3.3 or via the registration 1237 process described in Section 3.5. Usually, the addition of a 1238 'Deprecated' field is due to the action of one of the standards 1239 bodies, such as ISO 3166, withdrawing a code. Although valid in 1240 language tags, subtags and tags with a 'Deprecated' field are 1241 deprecated and validating processors SHOULD NOT generate these 1242 subtags. Note that a record that contains a 'Deprecated' field and 1243 no corresponding 'Preferred-Value' field has no replacement mapping. 1245 In some historical cases, it might not have been possible to 1246 reconstruct the original deprecation date. For these cases, an 1247 approximate date appears in the registry. Some subtags and some 1248 grandfathered or redundant tags were deprecated before the initial 1249 creation of the registry. The exact rules for this appear in Section 1250 2 of [RFC4645]. Note that these records have a 'Deprecated' field 1251 with an earlier date then the corresponding 'Added' field! 1253 3.1.7. Preferred-Value Field 1255 The field 'Preferred-Value' contains a mapping between the record in 1256 which it appears and another tag or subtag (depending on the record's 1257 'Type'). The value in this field is used for canonicalization (see 1258 Section 4.5). In cases where the subtag or tag also has a 1259 'Deprecated' field, then the 'Preferred-Value' is RECOMMENDED as the 1260 best choice to represent the value of this record when selecting a 1261 language tag. 1263 Records containing a Preferred-Value fall into one of these four 1264 groups: 1266 1. ISO 639 language codes that were later withdrawn in favor of 1267 other codes. These values are mostly a historical curiosity. 1268 The 'he'/'iw' pairing above is an example of this. 1270 2. Subtags (with types other than language or extlang) taken from 1271 codes or values that have been withdrawn in favor of a new code. 1272 In particular, this applies to region subtags taken from ISO 1273 3166-1, because sometimes a country will change its name or 1274 administration in such a way that warrants a new region code. In 1275 some cases, countries have reverted to an older name, which might 1276 already be encoded. For example, the subtag 'ZR' (Zaire) was 1277 replaced by the subtag 'CD' (Democratic Republic of the Congo) 1278 when that country's name was changed. 1280 3. Tags or subtags that have become obsolete because the values they 1281 represent were later encoded. Many of the grandfathered or 1282 redundant tags were later encoded by ISO 639, for example, and 1283 fall into this grouping. For example, "i-klingon" was deprecated 1284 when the subtag 'tlh' was added. The record for "i-klingon" has 1285 a 'Preferred-Value' of 'tlh'. 1287 4. Extended language subtags always have a mapping to their 1288 identical primary language subtag. For example, the extended 1289 language subtag 'yue' (Cantonese) can be used to form the tag 1290 "zh-yue". It has a Preferred-Value mapping to the primary 1291 language subtag 'yue', meaning that a tag such as 1292 "zh-yue-Hant-HK" can be canonicalized to "yue-Hant-HK". 1294 Records other than those of type 'extlang' that contain a 'Preferred- 1295 Value' field MUST also have a 'Deprecated' field. This field 1296 contains the date on which the tag or subtag was deprecated in favor 1297 of the preferred value. 1299 For records of type 'extlang', the 'Preferred-Value' field appears 1300 without a corresponding 'Deprecated' field. An implementation MAY 1301 ignore these preferred value mappings, although if it ignores the 1302 mapping, it SHOULD do so consistently. It SHOULD also treat the 1303 Preferred-Value as equivalent to the mapped item. For example, the 1304 tags "zh-yue-Hant-HK" and "yue-Hant-HK" are semantically equivalent 1305 and ought to be treated as if they were the same tag. 1307 Occasionally the deprecated code is preferred in certain contexts. 1308 For example, both "iw" and "he" can be used in the Java programming 1309 language, but "he" is converted on input to "iw", which is thus the 1310 canonical form in Java. 1312 'Preferred-Value' mappings in records of type 'region' sometimes do 1313 not represent exactly the same meaning as the original value. There 1314 are many reasons for a country code to be changed, and the effect 1315 this has on the formation of language tags will depend on the nature 1316 of the change in question. For example, the region subtag 'YD' 1317 (Democratic Yemen) was deprecated in favor of the subtag 'YE' (Yemen) 1318 when those two countries unified in 1990. 1320 A 'Preferred-Value' MAY be added to, changed, or removed from records 1321 according to the rules in Section 3.3. Addition, modification, or 1322 removal of a 'Preferred-Value' field in a record does not imply that 1323 content using the affected subtag needs to be retagged. 1325 The 'Preferred-Value' fields in records of type "grandfathered" and 1326 "redundant" each contain an "extended language range" ([RFC4647]) 1327 that is strongly RECOMMENDED for use in place of the record's value. 1328 In many cases, these mappings were created via deprecation of the 1329 tags during the period before [RFC4646] was adopted. For example, 1330 the tag "no-nyn" was deprecated in favor of the ISO 639-1-defined 1331 language code 'nn'. 1333 The 'Preferred-Value' field in subtag records of type "extlang" also 1334 contains an "extended language range". This allows the subtag to be 1335 deprecated in favor of either a single primary language subtag or a 1336 new language-extlang sequence. 1338 Usually the addition, removal, or change of a Preferred-Value field 1339 for a subtag is done to reflect changes in one of the source 1340 standards. For example, if an ISO 3166-1 region code is deprecated 1341 in favor of another code, that SHOULD result in the addition of a 1342 Preferred-Value field. 1344 Changes to one subtag MAY affect other subtags as well: when 1345 proposing changes to the registry, the Language Subtag Reviewer will 1346 review the registry for such effects and propose the necessary 1347 changes using the process in Section 3.5, although anyone MAY request 1348 such changes. For example: 1350 Suppose that subtag 'XX' has a Preferred-Value of 'YY'. If 'YY' 1351 later changes to have a Preferred-Value of 'ZZ', then the 1352 Preferred-Value for 'XX' MUST also change to be 'ZZ'. 1354 Suppose that a registered language subtag 'dialect' represents a 1355 language not yet available in any part of ISO 639. The later 1356 addition of a corresponding language code in ISO 639 SHOULD result 1357 in the addition of a Preferred-Value for 'dialect'. 1359 3.1.8. Prefix Field 1361 The 'Prefix' field contains an "extended language range" (see: 1362 [RFC4647]) whose subtags are appropriate to use with this subtag: 1363 each of the subtags in one of the subtag's Prefix fields SHOULD 1364 appear before the variant in a valid tag. For example, the variant 1365 subtag '1996' has a 'Prefix' field of "de". This means that tags 1366 starting with the sequence "de-" are appropriate with this subtag, so 1367 "de-Latf-1996" and "de-CH-1996" are both acceptable, while the tag 1368 "fr-1996" is an inappropriate choice. 1370 The field of type 'Prefix' MUST NOT be removed from any record. The 1371 field-body for this type of field MAY be modified, but only if the 1372 modification broadens the meaning of the subtag. That is, the field- 1373 body can be replaced only by a prefix of itself. For example, the 1374 Prefix "be-Latn" (Belarusian, Latin script) could be replaced by the 1375 Prefix "be" (Belarusian) but not by the Prefix "ru-Latn" (Russian, 1376 Latin script). 1378 Records of type 'variant' MAY have more than one field of type 1379 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1380 record via the registration process. Fields of type 'extlang' MUST 1381 have exactly one Prefix field. 1383 The field-body of the 'Prefix' field MUST NOT conflict with any 1384 'Prefix' already registered for a given record. Such a conflict 1385 would occur when no valid tag could be constructed that would contain 1386 the prefix, such as when two subtags each have a 'Prefix' that 1387 contains the other subtag. For example, suppose that the subtag 1388 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' 1389 cannot given the prefix 'avariant', for that would require a tag of 1390 the form "es-avariant-bvariant-avariant", which would not be valid. 1392 3.1.9. Suppress-Script Field 1394 The field 'Suppress-Script' contains a script subtag (whose record 1395 appears in the registry). The field 'Suppress-Script' MUST appear 1396 only in records whose 'Type' field-body is either 'language' or 1397 'extlang'. This field MUST NOT appear more than one time in a 1398 record. 1400 This field indicates a script used to write the overwhelming majority 1401 of documents for the given language. The subtag for such a script 1402 therefore adds no distinguishing information to a language tag and 1403 thus SHOULD NOT be used for most documents in that language. 1404 Omitting the script subtag indicated by this field helps ensure 1405 greater compatibility between the language tags generated according 1406 to the rules in this document and language tags and tag processors or 1407 consumers based on RFC 3066. For example, virtually all Icelandic 1408 documents are written in the Latin script, making the subtag 'Latn' 1409 redundant in the tag "is-Latn". 1411 Many language subtag records do not have a 'Suppress-Script' field. 1412 The lack of a 'Suppress-Script' might indicate that the language is 1413 customarily written in more than one script or that the language is 1414 not customarily written at all. It might also mean that sufficient 1415 information was not available when the record was created and thus 1416 remains a candidate for future registration. 1418 3.1.10. Macrolanguage Field 1420 The field 'Macrolanguage' contains a primary language subtag (whose 1421 record appears in the registry). This field indicates a language 1422 that encompasses this subtag's language according to assignments made 1423 by ISO 639-3. 1425 ISO 639-3 labels some languages in the registry as "macrolanguages". 1426 ISO 639-3 defines the term "Macrolanguage" to mean "clusters of 1427 closely-related language varieties that [...] can be considered 1428 distinct individual languages, yet in certain usage contexts a single 1429 language identity for all is needed". These correspond to codes 1430 registered in ISO 639-2 as individual languages that were found to 1431 correspond to more than one language in ISO 639-3. 1433 A language contained within a macrolanguage is called an "encompassed 1434 language". The record for each encompassed language contains a 1435 'Macrolanguage' field in the registry; the macrolanguages themselves 1436 are not specially marked. Note that some encompassed languages have 1437 ISO 639-1 or ISO 639-2 codes. 1439 The Macrolanguage field can only occur in records of type 'language' 1440 or 'extlang'. Only values assigned by ISO 639-3 will be considered 1441 for inclusion. Macrolanguage fields MAY be added or removed via the 1442 normal registration process whenever ISO 639-3 defines new values or 1443 withdraws old values. Macrolanguages are informational, and MAY be 1444 removed or changed if ISO 639-3 changes the values. For more 1445 information on the use of this field and choosing between 1446 macrolanguage and encompassed language subtags, see Section 4.1.1. 1448 For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' 1449 (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' 1450 (Norwegian). For more information see Section 4.1. 1452 3.1.11. Scope Field 1454 The field 'Scope' contains classification information about a primary 1455 or extended language subtag derived from ISO 639. Most languages 1456 have a scope of 'individual', which means that the language is not a 1457 macrolanguage, collection, special code, or private use. That is, it 1458 is what one would normally consider to be 'a language'. Any primary 1459 or extended language subtag that has no 'Scope' field is an 1460 individual language. 1462 Scope information can sometimes be helpful in selecting language 1463 tags, since it indicates the purpose or "scope" of the code 1464 assignment within ISO 639. The available values are: 1466 o 'macrolanguage' - Indicates a macrolanguage as defined by ISO 1467 639-3 (see above (Section 3.1.10)). A macrolanguage is a cluster 1468 of closely-related languages that are sometimes considered to be a 1469 single language. 1471 o 'collection' - Indicates a subtag that represents a collection of 1472 languages, typically related by some type of historical, 1473 geographical, or linguistic association. Unlike a macrolanguage, 1474 a collection can contain languages that are only loosely related 1475 and a collection cannot be used interchangeably with languages 1476 that belong to it. 1478 o 'special' - Indicates a special language code. These are subtags 1479 used for identifying linguistic attributes not particularly 1480 associated with a concrete language. These include codes for when 1481 the language is undetermined or for non-linguistic content. 1483 o 'private-use' - Indicates a code reserved for private use in the 1484 underlying standard. Subtags with this scope can be used to 1485 indicate a primary language for which no ISO 639 or registered 1486 assignment exists. 1488 The Scope field MAY appear in records of type 'language' or 1489 'extlang'. Note that many of the prefixes for extended language 1490 subtags will have a Scope of 'macrolanguage' (although some will not) 1491 and that many languages that have a Scope of 'macrolanguage' will 1492 have extended language subtags associated with them. 1494 The Scope field MAY be added, modified, or removed via the 1495 registration process, provided the change mirrors changes by ISO 639 1496 to the assignment's classification. Such a change is expected to be 1497 rare. 1499 For example, the primary language subtag 'zh' (Chinese) has a Scope 1500 of 'macrolanguage', while its enclosed language 'nan' (Min Nan 1501 Chinese) has a Scope of 'individual'. The special value 'und' 1502 (Undetermined) has a Scope of 'special'. The ISO 639-5 collection 1503 'gem' (Germanic languages) has a Scope of 'collection'. 1505 3.1.12. Comments Field 1507 The field 'Comments' contains additional information about the record 1508 and MAY appear more than once per record. The field-body MAY include 1509 the full range of Unicode characters and is not restricted to any 1510 particular script. This field MAY be inserted or changed via the 1511 registration process and no guarantee of stability is provided. 1513 The content of this field is not restricted, except by the need to 1514 register the information, the suitability of the request, and by 1515 reasonable practical size limitations. The primary reason for the 1516 'Comments' field is subtag identification: to help distinguish the 1517 subtag from others with which it might be confused as an aid to 1518 usage. Large amounts of information about the use, history, or 1519 general background of a subtag are frowned upon, as these generally 1520 belong in a registration request rather than in the registry. 1522 3.2. Language Subtag Reviewer 1524 The Language Subtag Reviewer moderates the ietf-languages@iana.org 1525 mailing list, responds to requests for registration, and performs the 1526 other registry maintenance duties described in Section 3.3. Only the 1527 Language Subtag Reviewer is permitted to request IANA to change, 1528 update, or add records to the Language Subtag Registry. The Language 1529 Subtag Reviewer MAY delegate list moderation and other clerical 1530 duties as needed. 1532 The Language Subtag Reviewer is appointed by the IESG for an 1533 indefinite term, subject to removal or replacement at the IESG's 1534 discretion. The IESG will solicit nominees for the position (upon 1535 adoption of this document or upon a vacancy) and then solicit 1536 feedback on the nominees' qualifications. Qualified candidates 1537 should be familiar with BCP 47 and its requirements; be willing to 1538 fairly, responsively, and judiciously administer the registration 1539 process; and be suitably informed about the issues of language 1540 identification so that the reviewer can assess the claims and draw 1541 upon the contributions of language experts and subtag requesters. 1543 The subsequent performance or decisions of the Language Subtag 1544 Reviewer MAY be appealed to the IESG under the same rules as other 1545 IETF decisions (see [RFC2026]). The IESG can reverse or overturn the 1546 decisions of the Language Subtag Reviewer, provide guidance, or take 1547 other appropriate actions. 1549 3.3. Maintenance of the Registry 1551 Maintenance of the registry requires that, as codes are assigned or 1552 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1553 Subtag Reviewer MUST evaluate each change and determine the 1554 appropriate course of action according to the rules in this document. 1555 Such updates follow the registration process described in 1556 Section 3.5. Usually the Language Subtag Reviewer will start the 1557 process for the new or updated record by filling in the registration 1558 form and submitting it. If a change to one of these standards takes 1559 place and the Language Subtag Reviewer does not do this in a timely 1560 manner, then any interested party MAY submit the form. Thereafter 1561 the registration process continues normally. 1563 Note that some registrations affect other subtags--perhaps more than 1564 one--as when a region subtag is being deprecated in favor of a new 1565 value. The Language Subtag Reviewer is responsible for ensuring that 1566 any such changes are properly registered, with each change requiring 1567 its own registration form. 1569 The Language Subtag Reviewer MUST ensure that new subtags meet the 1570 requirements elsewhere in this document (and most especially in 1571 Section 3.4) or submit an appropriate registration form for an 1572 alternate subtag as described in that section. Each individual 1573 subtag affected by a change MUST be sent to the 1574 ietf-languages@iana.org list with its own registration form and in a 1575 separate message. 1577 3.4. Stability of IANA Registry Entries 1579 The stability of entries and their meaning in the registry is 1580 critical to the long-term stability of language tags. The rules in 1581 this section guarantee that a specific language tag's meaning is 1582 stable over time and will not change. 1584 These rules specifically deal with how changes to codes (including 1585 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1586 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1587 Subtag Registry. Assignments to the IANA Language Subtag Registry 1588 MUST follow the following stability rules: 1590 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST 1591 NOT be changed and are guaranteed to be stable over time. 1593 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be 1594 added, altered, or removed via the registration process. These 1595 changes SHOULD be limited to changes necessary to mirror changes 1596 in one of the underlying standards (ISO 639, ISO 15924, ISO 1597 3166-1, or UN M.49) and typically alteration or removal of a 1598 Preferred-Value is limited specifically to region codes. 1600 3. Values in the 'Description' field MUST NOT be changed in a way 1601 that would invalidate any existing tags. The description MAY be 1602 broadened somewhat in scope, changed to add information, or 1603 adapted to the most common modern usage. For example, countries 1604 occasionally change their names; a historical example of this 1605 would be "Upper Volta" changing to "Burkina Faso". 1607 4. Values in the field 'Prefix' MAY be added to existing records of 1608 type 'variant' via the registration process, provided the 1609 'variant' already has at least one 'Prefix'. A 'Prefix' field 1610 SHALL NOT be registered for any 'variant' that has no existing 1611 'Prefix' field. If a prefix is added to a variant record, 1612 'Comment' fields MAY be used to explain different usages with 1613 the various prefixes. 1615 5. Values in the field 'Prefix' in records of type 'variant' MAY 1616 also be modified, so long as the modifications broaden the set 1617 of prefixes. That is, a prefix MAY be replaced by one of its 1618 own prefixes. For example, the prefix "en-US" could be replaced 1619 by "en", but not by the prefixes "en-Latn", "fr", or "en-US- 1620 boont". If one of those prefix values were needed, it would 1621 have to be separately registered. 1623 6. Values in the field 'Prefix' in records of type 'extlang' MUST 1624 NOT be added, modified, or removed. 1626 7. The field 'Prefix' MUST NOT be removed from any record in which 1627 it appears. This field SHOULD be included in the initial 1628 registration of any records of type 'variant' and MUST be 1629 included in any records of type 'extlang'. 1631 8. The field 'Comments' MAY be added, changed, modified, or removed 1632 via the registration process or any of the processes or 1633 considerations described in this section. 1635 9. The field 'Suppress-Script' MAY be added or removed via the 1636 registration process. 1638 10. The field 'Macrolanguage' MAY be added or removed via the 1639 registration process, but only in response to changes made by 1640 ISO 639. The Macrolanguage field appears whenever a language 1641 has a corresponding Macrolanguage in ISO 639. That is, the 1642 Macrolanguage fields in the registry exactly match those of ISO 1643 639. No other macrolanguage mappings will be considered for 1644 registration. 1646 11. The field 'Scope' MAY be added or removed from a primary or 1647 extended language subtag after initial registration, and it MAY 1648 be modified in order to match any changes made by ISO 639. 1649 Changes to the 'Scope' field MUST mirror changes made by ISO 1650 639. Note that primary or extended language subtags whose 1651 records do not contain a 'Scope' field (that is, most of them) 1652 are individual languages as described in Section 3.1.11. 1654 12. Primary and extended language subtags (other than independently 1655 registered values created using the registration process) are 1656 created according to the assignments of the various parts of ISO 1657 639, as follows: 1659 A. Codes assigned by ISO 639-1 that do not conflict with 1660 existing two-letter primary language subtags and which have 1661 no corresponding three-letter primary defined in the 1662 registry are entered into the IANA registry as new records 1663 of type 'language'. Note that languages given an ISO 639-1 1664 code cannot be given extended language subtags, even if 1665 encompassed by a macrolanguage. 1667 B. Codes assigned by ISO 639-3 or ISO 639-5 that do not 1668 conflict with existing three-letter primary language subtags 1669 and which do not have ISO 639-1 codes assigned (or expected 1670 to be assigned) are entered into the IANA registry as new 1671 records of type 'language'. Note that these two standards 1672 now comprise a superset of ISO 639-2 codes. Codes that have 1673 a defined "macrolanguage" mapping at the time of their 1674 registration MUST contain a "Macrolanguage" field. 1676 C. Codes assigned by ISO 639-3 MAY also be considered for an 1677 extended language subtag registration. Note that they MUST 1678 be assigned a primary language subtag record of type 1679 'language' even when an 'extlang' record is proposed. When 1680 considering extended language subtag assignment, these 1681 criteria apply: 1683 1. If a language has a macrolanguage mapping, and that 1684 macrolanguage has other encompassed languages that are 1685 assigned extended language subtags, then the new 1686 language SHOULD have an 'extlang' record assigned to it 1687 as well. For example, any language with a macrolanguage 1688 of 'zh' or 'ar' would be assigned an 'extlang' record. 1690 2. 'Extlang' records SHOULD NOT be created for languages if 1691 other languages encompassed by the macrolanguage do not 1692 also include 'extlang' records. For example, if a new 1693 Serbo-Croatian ('sh') language were registered, it would 1694 not get an extlang record because other languages 1695 encompassed such as Serbian ('sr') do not include one in 1696 the registry. 1698 3. Sign languages SHOULD have an 'extlang' record with a 1699 'Prefix' of 'sgn'. 1701 4. 'Extlang' records MUST NOT be created for items already 1702 in the registry. Extended language subtags will only be 1703 considered at the time of initial registration. 1705 5. Extended language subtag records MUST include the fields 1706 'Prefix' and 'Preferred-Value' with field-values 1707 assigned as described in Section 2.2.2. 1709 D. Any other codes assigned by ISO 639-2 that do not conflict 1710 with existing three-letter primary or extended language 1711 subtags and which do not have ISO 639-1 two-letter codes 1712 assigned are entered into the IANA registry as new records 1713 of type 'language'. This type of registration is not 1714 supposed to occur in the future. 1716 13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict 1717 with existing subtags of the associated type and whose meaning 1718 is not the same as an existing subtag of the same type are 1719 entered into the IANA registry as new records. 1721 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are 1722 withdrawn by their respective maintenance or registration 1723 authority remain valid in language tags. A 'Deprecated' field 1724 containing the date of withdrawal MUST be added to the record. 1725 If a new record of the same type is added that represents a 1726 replacement value, then a 'Preferred-Value' field MAY also be 1727 added. The registration process MAY be used to add comments 1728 about the withdrawal of the code by the respective standard. 1730 For example: the region code 'TL' was assigned to the country 1731 'Timor-Leste', replacing the code 'TP' (which was assigned to 1732 'East Timor' when it was under administration by Portugal). 1733 The subtag 'TP' remains valid in language tags, but its 1734 record contains the 'Preferred-Value' of 'TL' and its field 1735 'Deprecated' contains the date the new code was assigned 1736 ('2004-07-06'). 1738 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that 1739 conflict with existing subtags of the associated type, including 1740 subtags that are deprecated, MUST NOT be entered into the 1741 registry. The following additional considerations apply to 1742 subtag values that are reassigned: 1744 A. For ISO 639 codes, if the newly assigned code's meaning is 1745 not represented by a subtag in the IANA registry, the 1746 Language Subtag Reviewer, as described in Section 3.5, SHALL 1747 prepare a proposal for entering in the IANA registry as soon 1748 as practical a registered language subtag as an alternate 1749 value for the new code. The form of the registered language 1750 subtag will be at the discretion of the Language Subtag 1751 Reviewer and MUST conform to other restrictions on language 1752 subtags in this document. 1754 B. For all subtags whose meaning is derived from an external 1755 standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN 1756 M.49), if a new meaning is assigned to an existing code and 1757 the new meaning broadens the meaning of that code, then the 1758 meaning for the associated subtag MAY be changed to match. 1759 The meaning of a subtag MUST NOT be narrowed, however, as 1760 this can result in an unknown proportion of the existing 1761 uses of a subtag becoming invalid. Note: ISO 639 1762 registration authority (RA) has adopted a similar stability 1763 policy. 1765 C. For ISO 15924 codes, if the newly assigned code's meaning is 1766 not represented by a subtag in the IANA registry, the 1767 Language Subtag Reviewer, as described in Section 3.5, SHALL 1768 prepare a proposal for entering in the IANA registry as soon 1769 as practical a registered variant subtag as an alternate 1770 value for the new code. The form of the registered variant 1771 subtag will be at the discretion of the Language Subtag 1772 Reviewer and MUST conform to other restrictions on variant 1773 subtags in this document. 1775 D. For ISO 3166-1 codes, if the newly assigned code's meaning 1776 is associated with the same UN M.49 code as another 'region' 1777 subtag, then the existing region subtag remains as the 1778 preferred value for that region and no new entry is created. 1779 A comment MAY be added to the existing region subtag 1780 indicating the relationship to the new ISO 3166-1 code. 1782 E. For ISO 3166-1 codes, if the newly assigned code's meaning 1783 is associated with a UN M.49 code that is not represented by 1784 an existing region subtag, then the Language Subtag 1785 Reviewer, as described in Section 3.5, SHALL prepare a 1786 proposal for entering the appropriate UN M.49 country code 1787 as an entry in the IANA registry. 1789 F. For ISO 3166-1 codes, if there is no associated UN numeric 1790 code, then the Language Subtag Reviewer SHALL petition the 1791 UN to create one. If there is no response from the UN 1792 within ninety days of the request being sent, the Language 1793 Subtag Reviewer SHALL prepare a proposal for entering in the 1794 IANA registry as soon as practical a registered variant 1795 subtag as an alternate value for the new code. The form of 1796 the registered variant subtag will be at the discretion of 1797 the Language Subtag Reviewer and MUST conform to other 1798 restrictions on variant subtags in this document. This 1799 situation is very unlikely to ever occur. 1801 16. UN M.49 has codes for both countries and areas (such as '276' 1802 for Germany) and geographical regions and sub-regions (such as 1803 '150' for Europe). UN M.49 country or area codes for which 1804 there is no corresponding ISO 3166-1 code SHOULD NOT be 1805 registered, except as a surrogate for an ISO 3166-1 code that is 1806 blocked from registration by an existing subtag. If such a code 1807 becomes necessary, then the registration authority for ISO 1808 3166-1 SHOULD first be petitioned to assign a code to the 1809 region. If the petition for a code assignment by ISO 3166-1 is 1810 refused or not acted on in a timely manner, the registration 1811 process described in Section 3.5 MAY then be used to register 1812 the corresponding UN M.49 code. This way, UN M.49 codes remain 1813 available as the value of last resort in cases where ISO 3166-1 1814 reassigns a deprecated value in the registry. 1816 17. The redundant and grandfathered entries together form the 1817 complete list of tags registered under [RFC3066]. The redundant 1818 tags are those previously registered tags that can now be formed 1819 using the subtags defined in the registry. The grandfathered 1820 entries include those that can never be legal because they are 1821 'irregular' (that is, they do not match the 'langtag' production 1822 in Figure 1), are limited by rule (subtags such as 'nyn' and 1823 'min' look like the extlang production, but cannot be registered 1824 as extended language subtags), or their subtags are 1825 inappropriate for registration. All of the grandfathered tags 1826 are listed in either the 'regular' or the 'irregular' 1827 productions in the ABNF. Under [RFC4646] it was possible for 1828 grandfathered tags to become redundant. However, all of the 1829 tags for which this was possible became redundant before this 1830 document was produced. So the set of redundant and 1831 grandfathered tags is now permanent and immutable: new entries 1832 of either type MUST NOT be added and existing entries MUST NOT 1833 be removed. The decision-making process about which tags were 1834 initially grandfathered and which were made redundant is 1835 described in [RFC4645]. 1837 Many of the grandfathered tags are deprecated, indeed, they were 1838 deprecated even before [RFC4646]. For example, the tag "art- 1839 lojban" was deprecated in favor of the primary language subtag 1840 'jbo'. These tags could have been made 'redundant' by 1841 registering some of their subtags as 'variants'. The 'variant- 1842 like' subtags in the grandfathered registrations SHALL NOT be 1843 registered in the future, even with a similar or identical 1844 meaning. 1846 3.5. Registration Procedure for Subtags 1848 The procedure given here MUST be used by anyone who wants to use a 1849 subtag not currently in the IANA Language Subtag Registry or who 1850 wishes to add, modify, update, or remove information in existing 1851 records as permitted by this document. 1853 Only subtags of type 'language' and 'variant' will be considered for 1854 independent registration of new subtags. Subtags needed for 1855 stability and subtags necessary to keep the registry synchronized 1856 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1857 defined by this document also use this process, as described in 1858 Section 3.3 and subject to stability provisions as described in 1859 Section 3.4. 1861 Registration requests are accepted relating to information in the 1862 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value', 1863 or 'Suppress-Script' fields in a subtag's record as described in 1864 Section 3.4. Changes to all other fields in the IANA registry are 1865 NOT permitted. 1867 Registering a new subtag or requesting modifications to an existing 1868 tag or subtag starts with the requester filling out the registration 1869 form reproduced below. Note that each response is not limited in 1870 size so that the request can adequately describe the registration. 1871 The fields in the "Record Requested" section SHOULD follow the 1872 requirements in Section 3.1. 1874 LANGUAGE SUBTAG REGISTRATION FORM 1875 1. Name of requester: 1876 2. E-mail address of requester: 1877 3. Record Requested: 1879 Type: 1880 Subtag: 1881 Description: 1882 Prefix: 1883 Preferred-Value: 1884 Deprecated: 1885 Suppress-Script: 1886 Macrolanguage: 1887 Comments: 1889 4. Intended meaning of the subtag: 1890 5. Reference to published description 1891 of the language (book or article): 1892 6. Any other relevant information: 1894 Figure 5: The Language Subtag Registration Form 1896 Examples of completed registration forms can be found in Appendix C. 1897 A complete list of approved registration forms is online at 1898 http://www.iana.org/assignments/lang-subtags-templates/. 1900 The subtag registration form MUST be sent to 1901 . Registration requests receive a two-week 1902 review period before being approved and submitted to IANA for 1903 inclusion in the registry. If modifications are made to the request 1904 during the course of the registration process (such as corrections to 1905 meet the requirements in Section 3.1 or to make the 'Description' 1906 fields unique for the given record type) the modified form MUST also 1907 be sent to at least one week prior to 1908 submission to IANA. 1910 The ietf-languages list is an open list and can be joined by sending 1911 a request to . The list can be 1912 hosted by IANA or by any third party at the request of IESG. 1914 Before forwarding any registration to IANA, the Language Subtag 1915 Reviewer MUST ensure that all requirements in this document are met. 1916 This includes ensuring that values in the 'Subtag' field match case 1917 according to the description in Section 3.1.4 and that 'Description' 1918 fields are unique for the given record type as described in 1919 Section 3.1.5. The Reviewer MUST also ensure that an appropriate 1920 File-Date record is included in the request, to assist IANA when 1921 updating the registry (see Section 5.1). 1923 Some fields in both the registration form as well as the registry 1924 record itself permit the use of non-ASCII characters. Registration 1925 requests SHOULD use the UTF-8 encoding for consistency and clarity. 1926 However, since some mail clients do not support this encoding, other 1927 encodings MAY be used for the registration request. The Language 1928 Subtag Reviewer is responsible for ensuring that the proper Unicode 1929 characters appear in both the archived request form and the registry 1930 record. In the case of a transcription or encoding error by IANA, 1931 the Language Subtag Reviewer will request that the registry be 1932 repaired, providing any necessary information to assist IANA. 1934 Extended language subtags (type 'extlang'), by definition, are always 1935 encompassed by another language. All records of type 'extlang' MUST, 1936 therefore, contain a 'Prefix' field at the time of registration. 1937 This Prefix field can never be altered or removed and requests to do 1938 so MUST be rejected. 1940 Variant subtags are usually registered for use with a particular 1941 range of language tags and variant subtags based on the terminology 1942 of the language to which they are apply are encouraged. For example, 1943 the subtag 'rozaj' (Resian) is intended for use with language tags 1944 that start with the primary language subtag "sl" (Slovenian), since 1945 Resian is a dialect of Slovenian. Thus, the subtag 'rozaj' would be 1946 appropriate in tags such as "sl-Latn-rozaj" or "sl-IT-rozaj". This 1947 information is stored in the 'Prefix' field in the registry. Variant 1948 registration requests SHOULD include at least one 'Prefix' field in 1949 the registration form. 1951 Requests to assign an additional record of a given type with an 1952 existing subtag value MUST be rejected. For example, the variant 1953 subtag 'rozaj' already exists in the registry, so adding a second 1954 record of type 'variant' with the subtag 'rozaj' is prohibited. 1956 The 'Prefix' field for a given registered variant subtag exists in 1957 the IANA registry as a guide to usage. Additional 'Prefix' fields 1958 MAY be added by filing an additional registration form. In that 1959 form, the "Any other relevant information:" field MUST indicate that 1960 it is the addition of a prefix. 1962 Requests to add a 'Prefix' field to a variant subtag that imply a 1963 different semantic meaning SHOULD be rejected. For example, a 1964 request to add the prefix "de" to the subtag '1994' so that the tag 1965 "de-1994" represented some German dialect or orthographic form would 1966 be rejected. The '1994' subtag represents a particular Slovenian 1967 orthography and the additional registration would change or blur the 1968 semantic meaning assigned to the subtag. A separate subtag SHOULD be 1969 proposed instead. 1971 Requests to add a 'Prefix' to a variant subtag that has no current 1972 'Prefix' field MUST be rejected. Variants are registered with no 1973 prefix because they are potentially useful with many or even all 1974 languages. Adding one or more 'Prefix' fields would be potentially 1975 harmful to the use of the variant, since it dramatically reduces the 1976 scope of the subtag (which is not allowed under the stability rules 1977 (Section 3.4), as opposed to broadening the scope of the subtag, 1978 which is what the addition of a 'Prefix' normally does. An example 1979 of such a "no-prefix" variant is the subtag 'fonipa', which 1980 represents the International Phonetic Alphabet, a scheme which can be 1981 used to transcribe many languages. 1983 The 'Description' fields provided in the request MUST contain at 1984 least one description written or transcribed into the Latin script; 1985 the request MAY also include additional 'Description' fields in any 1986 script or language. The 'Description' field is used for 1987 identification purposes and doesn't necessarily represent the actual 1988 native name of the language or variation. It also doesn't have to be 1989 in any particular language, but SHOULD be both suitable and 1990 sufficient to identify the item in the record. The Language Subtag 1991 Reviewer will check and edit any proposed 'Description' fields so as 1992 to ensure uniqueness and prevent collisions with 'Description' fields 1993 in other records of the same type. If this occurs in an independent 1994 registration request, the Language Subtag Reviewer MUST resubmit the 1995 record to ietf-languages@iana.org, treating it as a modification of a 1996 request due to discussion, as described in Section 3.5, unless the 1997 request's sole purpose is to introduce a duplicate 'Description' 1998 field, in which case the request SHALL be rejected. 2000 While the 'Description' field itself is not guaranteed to be stable 2001 and errata corrections MAY be undertaken from time to time, attempts 2002 to provide translations or transcriptions of entries in the registry 2003 itself will probably be frowned upon by the community or rejected 2004 outright, as changes of this nature have an impact on the provisions 2005 in Section 3.4. 2007 Soon after the two-week review period has passed, the Language Subtag 2008 Reviewer MUST take one of the following actions: 2010 o Explicitly accept the request and forward the form containing the 2011 record to be inserted or modified to iana@iana.org according to 2012 the procedure described in Section 3.3. 2014 o Explicitly reject the request because of significant objections 2015 raised on the list or due to problems with constraints in this 2016 document (which MUST be explicitly cited). 2018 o Extend the review period by granting an additional two-week 2019 increment to permit further discussion. After each two-week 2020 increment, the Language Subtag Reviewer MUST indicate on the list 2021 whether the registration has been accepted, rejected, or extended. 2023 Note that the Language Subtag Reviewer MAY raise objections on the 2024 list if he or she so desires. The important thing is that the 2025 objection MUST be made publicly. 2027 Sometimes the request needs to be modified as a result of discussion 2028 during the review period or due to requirements in this document. 2029 The applicant, Language Subtag Reviewer, or others MAY submit a 2030 modified version of the completed registration form, which will be 2031 considered in lieu of the original request with the explicit approval 2032 of the applicant. Such changes do not restart the two-week 2033 discussion period, although an application containing the final 2034 record submitted to IANA MUST appear on the list at least one week 2035 prior to the Language Subtag Reviewer forwarding the record to IANA. 2036 The applicant MAY modify a rejected application with more appropriate 2037 or additional information and submit it again; this starts a new two- 2038 week comment period. 2040 Registrations initiated due to the provisions of Section 3.3 or 2041 Section 3.4 SHALL NOT be rejected altogether (since they have to 2042 ultimately appear in the registry) and SHOULD be completed as quickly 2043 as possible. The review process allows list members to comment on 2044 the specific information in the form and the record it contains and 2045 thus help ensure that it is correct and consistent. The Language 2046 Subtag Reviewer MAY reject a specific version of the form, but MUST 2047 propose a suitable replacement, extending the review period as 2048 described above, until the form is in a format worthy of reviewer's 2049 approval and meets with rough consensus of the list. 2051 Decisions made by the Language Subtag Reviewer MAY be appealed to the 2052 IESG [RFC2028] under the same rules as other IETF decisions 2053 [RFC2026]. This includes a decision to extend the review period or 2054 the failure to announce a decision in a clear and timely manner. 2056 The approved records appear in the Language Subtag Registry. The 2057 approved registration forms are available online under 2058 http://www.iana.org/assignments/lang-subtags-templates/. 2060 Updates or changes to existing records follow the same procedure as 2061 new registrations. The Language Subtag Reviewer decides whether 2062 there is consensus to update the registration following the two week 2063 review period; normally, objections by the original registrant will 2064 carry extra weight in forming such a consensus. 2066 Registrations are permanent and stable. Once registered, subtags 2067 will not be removed from the registry and will remain a valid way in 2068 which to specify a specific language or variant. 2070 Note: The purpose of the "Reference to published description" section 2071 in the registration form is to aid in verifying whether a language is 2072 registered or what language or language variation a particular subtag 2073 refers to. In most cases, reference to an authoritative grammar or 2074 dictionary of that language will be useful; in cases where no such 2075 work exists, other well-known works describing that language or in 2076 that language MAY be appropriate. The Language Subtag Reviewer 2077 decides what constitutes "good enough" reference material. This 2078 requirement is not intended to exclude particular languages or 2079 dialects due to the size of the speaker population or lack of a 2080 standardized orthography. Minority languages will be considered 2081 equally on their own merits. 2083 3.6. Possibilities for Registration 2085 Possibilities for registration of subtags or information about 2086 subtags include: 2088 o Primary language subtags for languages not listed in ISO 639 that 2089 are not variants of any listed or registered language MAY be 2090 registered. At the time this document was created, there were no 2091 examples of this form of subtag. Before attempting to register a 2092 language subtag, there MUST be an attempt to register the language 2093 with ISO 639. Subtags MUST NOT be registered for languages 2094 defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, 2095 or that are under consideration by the ISO 639 registration 2096 authorities, or that have never been attempted for registration 2097 with those authorities. If ISO 639 has previously rejected a 2098 language for registration, it is reasonable to assume that there 2099 must be additional, very compelling evidence of need before it 2100 will be registered as a primary language subtag in the IANA 2101 registry (to the extent that it is very unlikely that any subtags 2102 will be registered of this type). 2104 o Dialect or other divisions or variations within a language, its 2105 orthography, writing system, regional or historical usage, 2106 transliteration or other transformation, or distinguishing 2107 variation MAY be registered as variant subtags. An example is the 2108 'rozaj' subtag (the Resian dialect of Slovenian). 2110 o The addition or maintenance of fields (generally of an 2111 informational nature) in Tag or Subtag records as described in 2112 Section 3.1 and subject to the stability provisions in 2113 Section 3.4. This includes Description, Comments, Deprecated and 2114 Preferred-Value fields for obsolete or withdrawn codes, or the 2115 addition of Suppress-Script or Macrolanguage fields to primary 2116 language subtags, as well as other changes permitted by this 2117 document, such as the addition of an appropriate Prefix field to a 2118 variant subtag. 2120 o The addition of records and related field value changes necessary 2121 to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and 2122 UN M.49 as described in Section 3.4. 2124 Subtags proposed for registration that would cause all or part of a 2125 grandfathered tag to become redundant but whose meaning conflicts 2126 with or alters the meaning of the grandfathered tag MUST be rejected. 2128 This document leaves the decision on what subtags or changes to 2129 subtags are appropriate (or not) to the registration process 2130 described in Section 3.5. 2132 Note: four-character primary language subtags are reserved to allow 2133 for the possibility of alpha4 codes in some future addition to the 2134 ISO 639 family of standards. 2136 ISO 639 defines a registration authority for additions to and changes 2137 in the list of languages in ISO 639. This agency is: 2139 International Information Centre for Terminology (Infoterm) 2140 Aichholzgasse 6/12, AT-1120 2141 Wien, Austria 2142 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 2144 ISO 639-2 defines a registration authority for additions to and 2145 changes in the list of languages in ISO 639-2. This agency is: 2147 Library of Congress 2148 Network Development and MARC Standards Office 2149 Washington, D.C. 20540 USA 2150 Phone: +1 202 707 6237 Fax: +1 202 707 0115 2151 URL: http://www.loc.gov/standards/iso639-2 2153 ISO 639-3 defines a registration authority for additions to and 2154 changes in the list of languages in ISO 639-3. This agency is: 2156 SIL International 2157 ISO 639-3 Registrar 2158 7500 W. Camp Wisdom Rd. 2159 Dallas, TX 75236 USA 2160 Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 2161 Email: iso639-3@sil.org 2162 URL: http://www.sil.org/iso639-3 2164 ISO 639-5 defines a registration authority for additions to and 2165 changes in the list of languages in ISO 639-5. This agency is the 2166 same as for ISO 639-2 and is: 2168 Library of Congress 2169 Network Development and MARC Standards Office 2170 Washington, D.C. 20540 USA 2171 Phone: +1 202 707 6237 Fax: +1 202 707 0115 2172 URL: http://www.loc.gov/standards/iso639-5 2174 The maintenance agency for ISO 3166-1 (country codes) is: 2176 ISO 3166 Maintenance Agency 2177 c/o International Organization for Standardization 2178 Case postale 56 2179 CH-1211 Geneva 20 Switzerland 2180 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 2181 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 2183 The registration authority for ISO 15924 (script codes) is: 2185 Unicode Consortium 2186 Box 391476 2187 Mountain View, CA 94039-1476, USA 2188 URL: http://www.unicode.org/iso15924 2190 The Statistics Division of the United Nations Secretariat maintains 2191 the Standard Country or Area Codes for Statistical Use and can be 2192 reached at: 2194 Statistical Services Branch 2195 Statistics Division 2196 United Nations, Room DC2-1620 2197 New York, NY 10017, USA 2199 Fax: +1-212-963-0623 2200 E-mail: statistics@un.org 2201 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 2203 3.7. Extensions and the Extensions Registry 2205 Extension subtags are those introduced by single-character subtags 2206 ("singletons") other than 'x'. They are reserved for the generation 2207 of identifiers that contain a language component and are compatible 2208 with applications that understand language tags. 2210 The structure and form of extensions are defined by this document so 2211 that implementations can be created that are forward compatible with 2212 applications that might be created using singletons in the future. 2213 In addition, defining a mechanism for maintaining singletons will 2214 lend stability to this document by reducing the likely need for 2215 future revisions or updates. 2217 Single-character subtags are assigned by IANA using the "IETF 2218 Consensus" policy defined by [RFC2434]. This policy requires the 2219 development of an RFC, which SHALL define the name, purpose, 2220 processes, and procedures for maintaining the subtags. The 2221 maintaining or registering authority, including name, contact email, 2222 discussion list email, and URL location of the registry, MUST be 2223 indicated clearly in the RFC. The RFC MUST specify or include each 2224 of the following: 2226 o The specification MUST reference the specific version or revision 2227 of this document that governs its creation and MUST reference this 2228 section of this document. 2230 o The specification and all subtags defined by the specification 2231 MUST follow the ABNF and other rules for the formation of tags and 2232 subtags as defined in this document. In particular, it MUST 2233 specify that case is not significant and that subtags MUST NOT 2234 exceed eight characters in length. 2236 o The specification MUST specify a canonical representation. 2238 o The specification of valid subtags MUST be available over the 2239 Internet and at no cost. 2241 o The specification MUST be in the public domain or available via a 2242 royalty-free license acceptable to the IETF and specified in the 2243 RFC. 2245 o The specification MUST be versioned, and each version of the 2246 specification MUST be numbered, dated, and stable. 2248 o The specification MUST be stable. That is, extension subtags, 2249 once defined by a specification, MUST NOT be retracted or change 2250 in meaning in any substantial way. 2252 o The specification MUST include in a separate section the 2253 registration form reproduced in this section (below) to be used in 2254 registering the extension upon publication as an RFC. 2256 o IANA MUST be informed of changes to the contact information and 2257 URL for the specification. 2259 IANA will maintain a registry of allocated single-character 2260 (singleton) subtags. This registry MUST use the record-jar format 2261 described by the ABNF in Section 3.1. Upon publication of an 2262 extension as an RFC, the maintaining authority defined in the RFC 2263 MUST forward this registration form to iesg@ietf.org, who MUST 2264 forward the request to iana@iana.org. The maintaining authority of 2265 the extension MUST maintain the accuracy of the record by sending an 2266 updated full copy of the record to iana@iana.org with the subject 2267 line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only 2268 the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY 2269 be modified in these updates. 2271 Failure to maintain this record, maintain the corresponding registry, 2272 or meet other conditions imposed by this section of this document MAY 2273 be appealed to the IESG [RFC2028] under the same rules as other IETF 2274 decisions (see [RFC2026]) and MAY result in the authority to maintain 2275 the extension being withdrawn or reassigned by the IESG. 2277 %% 2278 Identifier: 2279 Description: 2280 Comments: 2281 Added: 2282 RFC: 2283 Authority: 2284 Contact_Email: 2285 Mailing_List: 2286 URL: 2287 %% 2289 Figure 6: Format of Records in the Language Tag Extensions Registry 2291 'Identifier' contains the single-character subtag (singleton) 2292 assigned to the extension. The Internet-Draft submitted to define 2293 the extension SHOULD specify which letter or digit to use, although 2294 the IESG MAY change the assignment when approving the RFC. 2296 'Description' contains the name and description of the extension. 2298 'Comments' is an OPTIONAL field and MAY contain a broader description 2299 of the extension. 2301 'Added' contains the date the extension's RFC was published in the 2302 "full-date" format specified in [RFC3339]. For example: 2004-06-28 2303 represents June 28, 2004, in the Gregorian calendar. 2305 'RFC' contains the RFC number assigned to the extension. 2307 'Authority' contains the name of the maintaining authority for the 2308 extension. 2310 'Contact_Email' contains the email address used to contact the 2311 maintaining authority. 2313 'Mailing_List' contains the URL or subscription email address of the 2314 mailing list used by the maintaining authority. 2316 'URL' contains the URL of the registry for this extension. 2318 The determination of whether an Internet-Draft meets the above 2319 conditions and the decision to grant or withhold such authority rests 2320 solely with the IESG and is subject to the normal review and appeals 2321 process associated with the RFC process. 2323 Extension authors are strongly cautioned that many (including most 2324 well-formed) processors will be unaware of any special relationships 2325 or meaning inherent in the order of extension subtags. Extension 2326 authors SHOULD avoid subtag relationships or canonicalization 2327 mechanisms that interfere with matching or with length restrictions 2328 that sometimes exist in common protocols where the extension is used. 2329 In particular, applications MAY truncate the subtags in doing 2330 matching or in fitting into limited lengths, so it is RECOMMENDED 2331 that the most significant information be in the most significant 2332 (left-most) subtags and that the specification gracefully handle 2333 truncated subtags. 2335 When a language tag is to be used in a specific, known, protocol, it 2336 is RECOMMENDED that the language tag not contain extensions not 2337 supported by that protocol. In addition, note that some protocols 2338 MAY impose upper limits on the length of the strings used to store or 2339 transport the language tag. 2341 3.8. Update of the Language Subtag Registry 2343 Upon adoption of this document the IANA Language Subtag Registry will 2344 need an update so that it contains the complete set of subtags valid 2345 in a language tag. This collection of subtags, along with a 2346 description of the process used to create it, is described by 2347 [draft-4645bis]. IANA will publish the updated version of the 2348 registry described by this document using the instructions and 2349 content of [draft-4645bis]. Once published by IANA, the maintenance 2350 procedures, rules, and registration processes described in this 2351 document will be available for new registrations or updates. 2353 Registrations that are in process under the rules defined in 2354 [RFC4646] when this document is adopted MUST be completed under the 2355 rules contained in this document. 2357 4. Formation and Processing of Language Tags 2359 This section addresses how to use the information in the registry 2360 with the tag syntax to choose, form, and process language tags. 2362 4.1. Choice of Language Tag 2364 The guiding principle in forming language tags is to "tag content 2365 wisely." Sometimes there is a choice between several possible tags 2366 for the same content. The choice of which tag to use depends on the 2367 content and application in question and some amount of judgment might 2368 be necessary when selecting a tag. 2370 Interoperability is best served when the same language tag is used 2371 consistently to represent the same language. If an application has 2372 requirements that make the rules here inapplicable, then that 2373 application risks damaging interoperability. It is strongly 2374 RECOMMENDED that users not define their own rules for language tag 2375 choice. 2377 Standards, protocols, and applications that reference this document 2378 normatively but apply different rules to the ones given in this 2379 section MUST specify how language tag selection varies from the 2380 guidelines given here. 2382 To ensure consistent backward compatibility, this document contains 2383 several provisions to account for potential instability in the 2384 standards used to define the subtags that make up language tags. 2385 These provisions mean that no valid language tag can become invalid, 2386 nor will a language tag have a narrower scope in the future (it may 2387 have a broader scope). The most appropriate language tag for a given 2388 application or content item might evolve over time, but once applied, 2389 the tag itself cannot become invalid or have its meaning wholly 2390 change. 2392 A subtag SHOULD only be used when it adds useful distinguishing 2393 information to the tag. Extraneous subtags interfere with the 2394 meaning, understanding, and processing of language tags. In 2395 particular, users and implementations SHOULD follow the 'Prefix' and 2396 'Suppress-Script' fields in the registry (defined in Section 3.1): 2397 these fields provide guidance on when specific additional subtags 2398 SHOULD be used or avoided in a language tag. 2400 The choice of subtags used to form a language tag SHOULD follow these 2401 guidelines: 2403 1. Use as precise a tag as possible, but no more specific than is 2404 justified. Avoid using subtags that are not important for 2405 distinguishing content in an application. 2407 * For example, 'de' might suffice for tagging an email written 2408 in German, while "de-CH-1996" is probably unnecessarily 2409 precise for such a task. 2411 * Note that some subtag sequences might not represent the 2412 language a casual user might expect, especially if when 2413 relying on the subtag's description in the registry. For 2414 example, the Swiss German (Schweizerdeutsch) language is 2415 represented by "gsw-CH" and not by "de-CH". This latter tag 2416 represents German ('de') as used in Switzerland ('CH'), also 2417 known as Swiss High German (Schweizer Hochdeutsch). Both are 2418 real languages and distinguishing between them could be 2419 important to an application. 2421 2. The script subtag SHOULD NOT be used to form language tags unless 2422 the script adds some distinguishing information to the tag. 2423 Script subtags were first formally defined in BCP 47 by 2424 [RFC4646]. Their use can affect matching and subtag 2425 identification for implementations of previous versions of BCP 47 2426 (i.e. [RFC1766] or [RFC3066]), as these subtags appear between 2427 the primary language and region subtags. Some applications can 2428 benefit from the use of script subtags in language tags, as long 2429 as the use is consistent for a given context. Script subtags are 2430 never appropriate for unwritten content (such as audio 2431 recordings). The field 'Suppress-Script' in the primary or 2432 extended language record in the registry indicates script subtags 2433 that do not add distinguishing information for most applications; 2434 this field defines when users SHOULD NOT include a script subtag 2435 with a particular primary language subtag. 2437 For example, if an implementation selects content using Basic 2438 Filtering [RFC4647] (originally described in Section 2.5 of 2439 [RFC3066]) and the user requested the language range "en-US", 2440 content labeled "en-Latn-US" will not match the request and thus 2441 not be selected. Therefore, it is important to know when script 2442 subtags will customarily be used and when they ought not be used. 2444 For example: 2446 * The subtag 'Latn' should not be used with the primary language 2447 'en' because nearly all English documents are written in the 2448 Latin script and it adds no distinguishing information. 2449 However, if a document were written in English mixing Latin 2450 script with another script such as Braille ('Brai'), then it 2451 might be appropriate to choose to indicate both scripts to aid 2452 in content selection, such as the application of a style 2453 sheet. 2455 * When labeling content that is unwritten (such as a recording 2456 of human speech), the script subtag should not be used, even 2457 if the language is customarily written in several scripts. 2458 Thus the subtitles to a movie might use the tag "uz-Arab" 2459 (Uzbek, Arabic script), but the audio track for the same 2460 language would be tagged simply "uz". (The tag "uz-Zxxx" 2461 could also be used where content is not written, as the subtag 2462 'Zxxx' represents the "Code for unwritten documents".) 2464 3. If a tag or subtag has a 'Preferred-Value' field in its registry 2465 entry, then the value of that field SHOULD be used to form the 2466 language tag in preference to the tag or subtag in which the 2467 preferred value appears. 2469 * For example, use 'jbo' for Lojban in preference to the 2470 grandfathered tag "art-lojban". 2472 4. Use subtags or sequences of subtags for individual languages in 2473 preference to subtags for language collections. A "language 2474 collection" is a group of languages that are descended from a 2475 common ancestor, are spoken in the same geographical area, or are 2476 otherwise related. Certain language collections are assigned 2477 codes by [ISO639-5] (and some of these [ISO639-5] codes are also 2478 defined as collections in [ISO639-2]). These codes are included 2479 as primary language subtags in the registry. Subtags for a 2480 language collection in the registry have a 'Scope' field with a 2481 value of 'collection'. A subtag for a language collection is 2482 always preferred to less-specific alternatives such as 'mul' and 2483 'und' (see below) and a subtag representing a language collection 2484 MAY be used when more specific language information is not 2485 available. However, most users and implementations do not know 2486 there is a relationship between the collection and its individual 2487 languages. In addition, the relationship between the individual 2488 languages in the collection is not well defined; in particular, 2489 the languages are usually not mutually intelligible. Since the 2490 subtags are different, a request for the collection will 2491 typically only produce items tagged with the collection's subtag, 2492 not items tagged with subtags for the individual languages 2493 contained in the collection. 2495 For example: 2497 1. Collections are interpreted inclusively, so the subtag 'gem' 2498 (Germanic langauges) could, but SHOULD NOT, be used with 2499 content that would be better tagged with "en" (English), "de" 2500 (German), or "gsw" (Swiss German, Alemannic). While 'gem' 2501 collects all of these (and other) languages, most 2502 implementations will not match 'gem' to the individual 2503 languages; thus using the subtag will not produce the desired 2504 result. 2506 5. [ISO639-2] has defined several codes included in the subtag 2507 registry that require additional care when choosing language 2508 tags. In most of these cases, where omitting the language tag is 2509 permitted, such omission is preferable to using these codes. 2510 Language tags SHOULD NOT incorporate these subtags as a prefix, 2511 unless the additional information conveys some value to the 2512 application. 2514 * The 'mul' (Multiple) primary language subtag identifies 2515 content in multiple languages. This subtag SHOULD NOT be used 2516 when a list of languages or individual tags for each content 2517 element can be used instead. For example, the 'Content- 2518 Language' header ([RFC3282]) allows a list of languages to be 2519 used, not just a single language tag. 2521 * The 'und' (Undetermined) primary language subtag identifies 2522 linguistic content whose language is not determined. This 2523 subtag SHOULD NOT be used unless a language tag is required 2524 and language information is not available or cannot be 2525 determined. Omitting the language tag (where permitted) is 2526 preferred. The 'und' subtag might be useful for protocols 2527 that require a language tag to be provided or where a primary 2528 language subtag is required (such as in "und-Latn"). The 2529 'und' subtag MAY also be useful when matching language tags in 2530 certain situations. 2532 * The 'zxx' (Non-Linguistic, Not Applicable) primary language 2533 subtag identifies content for which a language classification 2534 is inappropriate or does not apply. Some examples might 2535 include instrumental or electronic music; sound recordings 2536 consisting of nonverbal sounds; audiovisual materials with no 2537 narration, dialog, printed titles, or subtitles; machine- 2538 readable data files consisting of machine languages or 2539 character codes; or programming source code. 2541 * The 'mis' (Uncoded) primary language subtag identifies content 2542 whose language is known but which does not currently have a 2543 corresponding subtag. This subtag SHOULD NOT be used. 2544 Because the addition of other codes in the future can render 2545 its application invalid, it is inherently unstable and hence 2546 incompatible with the stability goals of BCP 47. It is always 2547 preferable to use other subtags: either 'und' or (with prior 2548 agreement) private use subtags. 2550 6. Use variant subtags sparingly and in the correct order. Most 2551 variant subtags have one or more 'Prefix' fields in the registry 2552 that express the list of subtags that they are appropriate with. 2553 Variants SHOULD only be used with subtags that appear in one of 2554 these 'Prefix' fields. If a variant lists a second variant in 2555 one of its 'Prefix' fields, the first variant SHOULD appear 2556 directly after the second variant in any language tag where both 2557 occur. General purpose variants (those with no 'Prefix' fields 2558 at all) SHOULD appear after any other variant subtags. Order any 2559 remaining variants by placing the most significant subtag first. 2560 If none of the subtags is more significant or no relationship can 2561 be determined, alphabetize the subtags. Because variants are 2562 very specialized, using many of them together generally makes the 2563 tag so narrow as to override the additional precision gained. 2564 Putting the subtags into another order interferes with 2565 interoperability, as well as the overall interpretation of the 2566 tag. 2568 A. For example, the tag "en-scottish-fonipa" (English, Scottish 2569 dialect, IPA phonetic transcription) is correctly ordered 2570 because 'scottish' has a 'Prefix' of "en", while 'fonipa' has 2571 no 'Prefix' field. 2573 B. For example, the tag "sl-IT-rozaj-biske-1994" is correctly 2574 ordered: 'rozaj' lists "sl" as its sole 'Prefix'; 'biske' 2575 lists "sl-rozaj" as its sole Prefix. The subtag '1994' has 2576 several prefixes, including "sl-rozaj". However, it follows 2577 both 'rozaj' and 'biske' because one of its 'Prefix' fields 2578 is "sl-rozaj-biske". 2580 7. The grandfathered tag "i-default" (Default Language) was 2581 originally registered according to [RFC1766] to meet the needs of 2582 [RFC2277]. It is used to indicate not a specific language, but 2583 rather, it identifies the condition or content used where the 2584 language preferences of the user cannot be established. It 2585 SHOULD NOT be used except as a means of labeling the default 2586 content for applications or protocols that require default 2587 language content to be labeled with that specific tag. It MAY 2588 also be used by an application or protocol to identify when the 2589 default language content is being returned. 2591 4.1.1. Tagging Encompassed Languages 2593 Some primary language records in the registry have a "Macrolanguage" 2594 field (Section 3.1.10) that contains a mapping from each "encompassed 2595 language" to its macrolanguage. The Macrolanguage mapping doesn't 2596 define what the relationship between the encompassed language and its 2597 macrolanguage is, nor does it define how languages encompassed by the 2598 same macrolanguage are related to each other. Two different 2599 languages encompassed by the same macrolanguage may differ from one 2600 another more than say, French and Spanish do. 2602 A few specific macrolanguages, such as Chinese ('zh') and Arabic 2603 ('ar'), are handled differently. See Section 4.1.2. 2605 The more specific encompassed language subtag SHOULD be used to form 2606 the language tag, although either the macrolanguage's primary 2607 language subtag or the encompassed language's subtag MAY be used. 2608 This means, for example, tagging Plains Cree with 'crk' rather than 2609 'cre' (Cree); and so forth. 2611 Each macrolanguage subtag's scope, by definition, includes all of its 2612 encompassed languages. Since the relationship between encompassed 2613 languages varies, users cannot assume that the macrolanguage subtag 2614 means any particular encompassed language nor that any given pair of 2615 encompassed languages are mutually intelligible or otherwise 2616 interchangeable. 2618 Applications MAY use macrolanguage information to improve matching or 2619 language negotiation. For example, the information that 'sr' 2620 (Serbian) and 'hr' (Croatian) share a macrolanguage expresses a 2621 closer relation between those languages than between, say, 'sr' 2622 (Serbian) and 'ma' (Macedonian). However, this relationship is not 2623 guaranteed nor is it exclusive. For example, Romanian ('ro') and 2624 Moldavian ('mo') do not share a macrolanguage, but are far more 2625 closely related to each other than Cantonese ('yue') and Wu ('wuu') , 2626 which do share a macrolanguage. 2628 4.1.2. Using Extended Language Subtags 2630 To accommodate language tag forms used prior to the adoption of this 2631 document, language tags provide a special compatibility mechanism: 2632 the extended language subtag. Selected languages have been provided 2633 with both primary and extended language subtags. These include 2634 macrolanguages, such as Malay ('ms') and Uzbek ('uz'), that have a 2635 specific dominant variety that is generally synonymous with the 2636 macrolanguage. Other languages, such as the Chinese ('zh') and 2637 Arabic ('ar') macrolanguages and the various sign languages ('sgn'), 2638 have traditionally used their primary language subtag, possibly 2639 coupled with various region subtags or as part of a registered 2640 grandfathered tag, to indicate the language. 2642 With the adoption of this document, specific ISO 639-3 subtags became 2643 available to identify the languages contained within these diverse 2644 language families or groupings. This presents a choice of language 2645 tags where previously none existed: 2647 o Each encompassed language's subtag SHOULD be used as the primary 2648 language subtag. For example, a document in Mandarin Chinese 2649 would be tagged "cmn" (the subtag for Mandarin Chinese) in 2650 preference to "zh" (Chinese). 2652 o If compatibility is desired or needed, the encompassed subtag MAY 2653 be used as an extended language subtag. For example, a document 2654 in Mandarin Chinese could be tagged "zh-cmn" instead of either 2655 "cmn" or "zh". 2657 o The macrolanguage or prefixing subtag MAY still be used to form 2658 the tag instead of the more specific encompassed language subtag. 2659 That is, tags such as "zh-HK" or "sgn-RU" are still valid. 2661 Chinese ('zh') provides a useful illustration of this. In the past, 2662 various content has used tags beginning with the 'zh' subtag, with 2663 application specific meaning being associated with region codes, 2664 private-use sequences, or grandfathered registered values. This is 2665 because historically only the macrolanguage subtag 'zh' was available 2666 for forming language tags. However, the languages encompassed by the 2667 Chinese subtag 'zh' are, in the main, not mutually intelligible when 2668 spoken, and the written forms of these languages also show wide 2669 variation in form and usage. 2671 To provide compatibility, Chinese languages encompassed by the 'zh' 2672 subtag are in the registry as both primary language subtags and as 2673 extended language subtags. For example, the ISO 639-3 code for 2674 Cantonese is 'yue'. Content in Cantonese might historically have 2675 used a tag such as "zh-HK" (since Cantonese is commonly spoken in 2676 Hong Kong), although that tag actually means any type of Chinese as 2677 used in Hong Kong. With the availability of ISO 639-3 codes in the 2678 registry, content in Cantonese can be directly tagged using the 'yue' 2679 subtag. The content can use it as a primary language subtag, as in 2680 the tag "yue-HK" (Cantonese, Hong Kong). Or it can use an extended 2681 language subtag with 'zh', as in the tag "zh-yue-Hant" (Chinese, 2682 Cantonese, Traditional script). 2684 As noted above, applications can choose to use the macrolanguage 2685 subtag to form the tag instead of using the more specific encompassed 2686 language subtag. For example, an application with large quantities 2687 of data already using tags with the 'zh' (Chinese) subtag might 2688 continue to use this more general subtag even for new data, even 2689 though the content could be more precisely tagged with 'cmn' 2690 (Mandarin), 'yue' (Cantonese), 'wuu' (Wu), and so on. Similarly, an 2691 application already using tags that start with the 'ar' (Arabic) 2692 subtag might continue to use this more general subtag even for new 2693 data, which could be more precisely be tagged with 'arb' (Standard 2694 Arabic). 2696 In some cases, the encompassed languages had tags registered for them 2697 during the RFC 3066 era. Those grandfathered tags not already 2698 deprecated or rendered redundant were deprecated in the registry upon 2699 adoption of this document. As grandfathered values, they remain 2700 valid for use and some content or applications might use them. As 2701 with other grandfathered tags, since implementations might not be 2702 able to associate the grandfathered tags with the encompassed 2703 language subtag equivalents that are recommended by this document, 2704 implementations are encouraged to canonicalize tags for comparison 2705 purposes. Some examples of this include the tags "zh-hakka" (Hakka) 2706 and "zh-guoyu" (Mandarin or Standard Chinese). 2708 Sign languages share a mode of communication rather than a linguistic 2709 heritage. There are many sign languages which have developed 2710 independently and the subtag 'sgn' indicates only the presence of a 2711 sign language. A number of sign languages also had grandfathered 2712 tags registered for them during the RFC 3066 era. For example, the 2713 grandfathered tag "sgn-US" was registered to represent 'American Sign 2714 Language' specifically, without reference to the United States. This 2715 is still valid, but deprecated: a document in American Sign Language 2716 can be labeled either "ase" or "sgn-ase" (the 'ase' subtag is for the 2717 language called 'American Sign Language'). 2719 4.2. Meaning of the Language Tag 2721 The meaning of a language tag is related to the meaning of the 2722 subtags that it contains. Each subtag, in turn, implies a certain 2723 range of expectations one might have for related content, although it 2724 is not a guarantee. For example, the use of a script subtag such as 2725 'Arab' (Arabic script) does not mean that the content contains only 2726 Arabic characters. It does mean that the language involved is 2727 predominantly in the Arabic script. Thus a language tag and its 2728 subtags can encompass a very wide range of variation and yet remain 2729 appropriate in each particular instance. 2731 Validity of a tag is not the only factor determining its usefulness. 2732 While every valid tag has a meaning, it might not represent any real- 2733 world language usage. This is unavoidable in a system in which 2734 subtags can be combined freely. For example, tags such as 2735 "ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia) or "tlh- 2736 Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA 2737 phonetic transcription) are both valid and unlikely to represent a 2738 useful combination of language attributes. 2740 The meaning of a given tag doesn't depend on the context in which it 2741 appears. The relationship between a tag's meaning and the 2742 information objects to which that tag is applied, however, can vary. 2744 o For a single information object, the associated language tags 2745 might be interpreted as the set of languages that is necessary for 2746 a complete comprehension of the complete object. Example: Plain 2747 text documents. 2749 o For an aggregation of information objects, the associated language 2750 tags could be taken as the set of languages used inside components 2751 of that aggregation. Examples: Document stores and libraries. 2753 o For information objects whose purpose is to provide alternatives, 2754 the associated language tags could be regarded as a hint that the 2755 content is provided in several languages and that one has to 2756 inspect each of the alternatives in order to find its language or 2757 languages. In this case, the presence of multiple tags might not 2758 mean that one needs to be multi-lingual to get complete 2759 understanding of the document. Example: MIME multipart/ 2760 alternative. 2762 o For markup languages, such as HTML and XML, language information 2763 can be added to each part of the document identified by the markup 2764 structure (including the whole document itself). For example, one 2765 could write C'est la vie. inside a German 2766 document; the German-speaking user could then access a French- 2767 German dictionary to find out what the marked section meant. If 2768 the user were listening to that document through a speech 2769 synthesis interface, this formation could be used to signal the 2770 synthesizer to appropriately apply French text-to-speech 2771 pronunciation rules to that span of text, instead of applying the 2772 inappropriate German rules. 2774 o For markup languages and document formats that allow the audience 2775 to be identified, a language tag could indicate the audience(s) 2776 appropriate for that document. For example, the same HTML 2777 document described in the preceding bullet might have an HTTP 2778 header "Content-Language: de" to indicate that the intended 2779 audience audience for the file is German (even though three words 2780 appear and are identified as being in French within it). 2782 o For systems and APIs, language tags form the basis for most 2783 implementations of locale identifiers. For example, see Unicode's 2784 CLDR (Common Locale Data Repository) (see: UTS #35 [UTS35]) 2785 project. 2787 Language tags are related when they contain a similar sequence of 2788 subtags. For example, if a language tag B contains language tag A as 2789 a prefix, then B is typically "narrower" or "more specific" than A. 2790 Thus, "zh-Hant-TW" is more specific than "zh-Hant". 2792 This relationship is not guaranteed in all cases: specifically, 2793 languages that begin with the same sequence of subtags are NOT 2794 guaranteed to be mutually intelligible, although they might be. For 2795 example, the tag "az" shares a prefix with both "az-Latn" 2796 (Azerbaijani written using the Latin script) and "az-Cyrl" 2797 (Azerbaijani written using the Cyrillic script). A person fluent in 2798 one script might not be able to read the other, even though the 2799 linguistic content (e.g., what would be heard if both texts were read 2800 aloud) might be identical. Content tagged as "az" most probably is 2801 written in just one script and thus might not be intelligible to a 2802 reader familiar with the other script. 2804 Similarly, not all subtags specify an actual distinction in language. 2805 For example, the tags "en-US" and "en-CA" mean, roughly, English with 2806 features generally thought to be characteristic of the United States 2807 and Canada, respectively. They do not imply that a significant 2808 dialectical boundary exists between any arbitrarily selected point in 2809 the United States and any arbitrarily selected point in Canada. 2810 Neither does a particular region subtag imply that linguistic 2811 distinctions do not exist within that region. 2813 4.3. Lists of Languages 2815 In some applications, a single content item might best be associated 2816 with more than one language tag. Examples of such a usage include: 2818 o A language priority list [RFC4647] describing a user's language 2819 preferences. This is a (possibly weighted) list of potentially- 2820 unrelated varieties, expressing a preference, rather than as a 2821 declaration about actual content. 2823 o Content items that contain multiple, distinct varieties. Often 2824 this is used to indicate an appropriate audience for a given 2825 content item when multiple choices might be appropriate. Examples 2826 of this could include: 2828 * Metadata about the appropriate audience for a movie title. For 2829 example, a DVD might label its individual audio tracks 'de' 2830 (German), 'fr' (French), and 'es' (Spanish), but the overall 2831 title would list "de, fr, es" as its overall audience. 2833 * A French/English, English/French dictionary tagged as both "en" 2834 and "fr" to specify that it applies equally to French and 2835 English 2837 * A side-by-side or interlinear translation of a document, as is 2838 commonly done with classical works in Latin or Greek 2840 o Content items that contain a single language but which require 2841 multiple levels of specificity. For example, a library might wish 2842 to classify a particular work as both Norwegian ('no') and as 2843 Nynorsk ('nn') for audiences capable of appreciating the 2844 distinction or needing to select content more narrowly. 2846 4.4. Length Considerations 2848 There is no defined upper limit on the size of language tags. While 2849 historically most language tags have consisted of language and region 2850 subtags with a combined total length of up to six characters, larger 2851 tags have always been both possible and have actually appeared in 2852 use. 2854 Neither the language tag syntax nor other requirements in this 2855 document impose a fixed upper limit on the number of subtags in a 2856 language tag (and thus an upper bound on the size of a tag). The 2857 language tag syntax suggests that, depending on the specific 2858 language, more subtags (and thus a longer tag) are sometimes 2859 necessary to completely identify the language for certain 2860 applications; thus, it is possible to envision long or complex subtag 2861 sequences. 2863 4.4.1. Working with Limited Buffer Sizes 2865 Some applications and protocols are forced to allocate fixed buffer 2866 sizes or otherwise limit the length of a language tag. A conformant 2867 implementation or specification MAY refuse to support the storage of 2868 language tags that exceed a specified length. Any such limitation 2869 SHOULD be clearly documented, and such documentation SHOULD include 2870 what happens to longer tags (for example, whether an error value is 2871 generated or the language tag is truncated). A protocol that allows 2872 tags to be truncated at an arbitrary limit, without giving any 2873 indication of what that limit is, has the potential for causing harm 2874 by changing the meaning of tags in substantial ways. 2876 In practice, most language tags do not require more than a few 2877 subtags and will not approach reasonably sized buffer limitations; 2878 see Section 4.1. 2880 Some specifications or protocols have limits on tag length but do not 2881 have a fixed length limitation. For example, [RFC2231] has no 2882 explicit length limitation: the length available for the language tag 2883 is constrained by the length of other header components (such as the 2884 charset's name) coupled with the 76-character limit in [RFC2047]. 2885 Thus, the "limit" might be 50 or more characters, but it could 2886 potentially be quite small. 2888 The considerations for assigning a buffer limit are: 2890 Implementations SHOULD NOT truncate language tags unless the 2891 meaning of the tag is purposefully being changed, or unless the 2892 tag does not fit into a limited buffer size specified by a 2893 protocol for storage or transmission. 2895 Implementations SHOULD warn the user when a tag is truncated since 2896 truncation changes the semantic meaning of the tag. 2898 Implementations of protocols or specifications that are space 2899 constrained but do not have a fixed limit SHOULD use the longest 2900 possible tag in preference to truncation. 2902 Protocols or specifications that specify limited buffer sizes for 2903 language tags MUST allow for language tags of at least 35 2904 characters. Note that RFC 4646 [RFC4646] recommended a minimum 2905 field size of 42 characters because it included all three elements 2906 of the 'extlang' production. Two of these are now permanently 2907 reserved, so a registered primary language subtag of the maximum 2908 length of eight characters is now longer than the longest 2909 language-extlang combintation. Protocols or specifications that 2910 commonly use extensions or private use subtags might wish to 2911 reserve or recommend a longer "minimum buffer" size. 2913 The following illustration shows how the 35-character recommendation 2914 was derived: 2916 language = 8 ; longest allowed registered value 2917 ; longer than primary+extlang 2918 ; which requires 7 characters 2919 script = 5 ; if not suppressed: see Section 4.1 2920 region = 4 ; UN M.49 numeric region code 2921 ; ISO 3166-1 codes require 3 2922 variant1 = 9 ; needs 'language' as a prefix 2923 variant2 = 9 ; very rare, as it needs 2924 ; 'language-variant1' as a prefix 2926 total = 35 characters 2928 Figure 7: Derivation of the Limit on Tag Length 2930 4.4.2. Truncation of Language Tags 2932 Truncation of a language tag alters the meaning of the tag, and thus 2933 SHOULD be avoided. However, truncation of language tags is sometimes 2934 necessary due to limited buffer sizes. Such truncation MUST NOT 2935 permit a subtag to be chopped off in the middle or the formation of 2936 invalid tags (for example, one ending with the "-" character). 2938 This means that applications or protocols that truncate tags MUST do 2939 so by progressively removing subtags along with their preceding "-" 2940 from the right side of the language tag until the tag is short enough 2941 for the given buffer. If the resulting tag ends with a single- 2942 character subtag, that subtag and its preceding "-" MUST also be 2943 removed. For example: 2945 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 2946 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 2947 2. zh-Latn-CN-variant1-a-extend1 2948 3. zh-Latn-CN-variant1 2949 4. zh-Latn-CN 2950 5. zh-Latn 2951 6. zh 2953 Figure 8: Example of Tag Truncation 2955 4.5. Canonicalization of Language Tags 2957 Since a particular language tag is sometimes used by many processes, 2958 language tags SHOULD always be created or generated in a canonical 2959 form. 2961 A language tag is in canonical form when: 2963 1. The tag is well-formed according the rules in Section 2.1 and 2964 Section 2.2. 2966 2. Redundant or grandfathered tags that have a Preferred-Value 2967 mapping in the IANA registry (see Section 3.1) MUST be replaced 2968 with their mapped value. These items either are deprecated 2969 mappings created before the adoption of this document (such as 2970 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 2971 the result of later registrations or additions to this document 2972 (for example, "zh-hakka" was deprecated in favor of the ISO 639-3 2973 code 'hak' when this document was adopted). These mappings 2974 SHOULD be done before additional processing, since there can be 2975 additional changes to subtag values. These field-body of the 2976 Preferred-Value for grandfathered and redundant tags is an 2977 "extended language range" ([RFC4647]) and might consist of more 2978 than one subtag. 2980 3. Subtags of type 'extlang' SHOULD be mapped to their Preferred- 2981 Value. The field-body of the Preferred-Value for extlangs is an 2982 "extended language range" and typically maps to a primary 2983 language subtag. For example, the subtag sequence "zh-hak" 2984 (Chinese, Hakka) would be replaced with the tag "hak" (Hakka). 2986 4. Other subtags that have a Preferred-Value field in the IANA 2987 registry (see Section 3.1) MUST be replaced with their mapped 2988 value. Most of these are either Region subtags where the country 2989 name or designation has changed or clerical corrections to ISO 2990 639-1. 2992 5. If more than one extension subtag sequence exists, the extension 2993 sequences are ordered into case-insensitive ASCII order by 2994 singleton subtag (that is, the subtag sequence '-a-babble' comes 2995 before '-b-warble'). 2997 Example: The language tag "en-a-aaa-b-ccc-bbb-x-xyz" is in canonical 2998 form, while "en-b-ccc-bbb-a-aaa-X-xyz" is well-formed and potentially 2999 valid (extensions 'a' and 'b' are not defined as of the publication 3000 of this document) but not in canonical form (the extensions are not 3001 in alphabetical order). 3003 Example: Although the tag "en-BU" (English as used in Burma) 3004 maintains its validity, the language tag "en-BU" is not canonical 3005 because the 'BU' subtag has a canonical mapping to 'MM' (Myanmar). 3007 Canonicalization of language tags does not imply anything about the 3008 use of upper or lowercase letters when processing or comparing 3009 subtags (and as described in Section 2.1). All comparisons MUST be 3010 performed in a case-insensitive manner. 3012 When performing canonicalization of language tags, processors MAY 3013 regularize the case of the subtags (that is, this process is 3014 OPTIONAL), following the case used in the registry (see 3015 Section 2.1.1). 3017 If more than one variant appears within a tag, processors MAY reorder 3018 the variants to obtain better matching behavior or more consistent 3019 presentation. Reordering of the variants SHOULD follow the 3020 recommendations for variant ordering in Section 4.1. 3022 If the field 'Deprecated' appears in a registry record without an 3023 accompanying 'Preferred-Value' field, then that tag or subtag is 3024 deprecated without a replacement. These values are canonical when 3025 they appear in a language tag. However, tags that include these 3026 values SHOULD NOT be selected by users or generated by 3027 implementations. 3029 An extension MUST define any relationships that exist between the 3030 various subtags in the extension and thus MAY define an alternate 3031 canonicalization scheme for the extension's subtags. Extensions MAY 3032 define how the order of the extension's subtags are interpreted. For 3033 example, an extension could define that its subtags are in canonical 3034 order when the subtags are placed into ASCII order: that is, "en-a- 3035 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 3036 define that the order of the subtags influences their semantic 3037 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 3038 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 3039 so that they are tolerant of the typical processes described in 3040 Section 3.7. 3042 4.6. Considerations for Private Use Subtags 3044 Private use subtags, like all other subtags, MUST conform to the 3045 format and content constraints in the ABNF. Private use subtags have 3046 no meaning outside the private agreement between the parties that 3047 intend to use or exchange language tags that employ them. The same 3048 subtags MAY be used with a different meaning under a separate private 3049 agreement. They SHOULD NOT be used where alternatives exist and 3050 SHOULD NOT be used in content or protocols intended for general use. 3052 Private use subtags are simply useless for information exchange 3053 without prior arrangement. The value and semantic meaning of private 3054 use tags and of the subtags used within such a language tag are not 3055 defined by this document. 3057 Private use sequences introduced by the 'x' singleton are completely 3058 opaque to users or implementations outside of the private use 3059 agreement. So, in addition to private use subtag sequences 3060 introduced by the singleton subtag 'x', the Language Subtag Registry 3061 provides private use language, script, and region subtags derived 3062 from the private use codes assigned by the underlying standards. 3063 These subtags are valid for use in forming language tags; they are 3064 RECOMMENDED over the 'x' singleton private use subtag sequences 3065 because they convey more information via their linkage to the 3066 language tag's inherent structure. 3068 For example, the region subtags 'AA', 'ZZ', and in the ranges 3069 'QM'-'QZ' and 'XA'-'XZ' (derived from the ISO 3166-1 private use 3070 codes) can be used to form a language tag. A tag such as 3071 "zh-Hans-XQ" conveys a great deal of public, interchangeable 3072 information about the language material (that it is Chinese in the 3073 simplified Chinese script and is suitable for some geographic region 3074 'XQ'). While the precise geographic region is not known outside of 3075 private agreement, the tag conveys far more information than an 3076 opaque tag such as "x-somelang" or even "zh-Hans-x-xq" (where the 3077 'xq' subtag's meaning is entirely opaque). 3079 However, in some cases content tagged with private use subtags MAY 3080 interact with other systems in a different and possibly unsuitable 3081 manner compared to tags that use opaque, privately defined subtags, 3082 so the choice of the best approach sometimes depends on the 3083 particular domain in question. 3085 5. IANA Considerations 3087 This section deals with the processes and requirements necessary for 3088 IANA to undertake to maintain the subtag and extension registries as 3089 defined by this document and in accordance with the requirements of 3090 [RFC2434]. 3092 The impact on the IANA maintainers of the two registries defined by 3093 this document will be a small increase in the frequency of new 3094 entries or updates. IANA also is required to create a new mailing 3095 list (described below in Section 5.1) to announce registry changes 3096 and updates. 3098 5.1. Language Subtag Registry 3100 Upon adoption of this document, IANA will update the registry using 3101 instructions and content provided in a companion document: 3102 [draft-4645bis]. The criteria and process for selecting the updated 3103 set of records are described in that document. The updated set of 3104 records represents no impact on IANA, since the work to create it 3105 will be performed externally. 3107 Future work on the Language Subtag Registry includes the following 3108 activities: 3110 o Inserting or replacing whole records. These records are 3111 preformatted for IANA by the Language Subtag Reviewer, as 3112 described in Section 3.3. 3114 o Archiving and making publicly available the registration forms. 3116 o Announcing each updated version of the registry on the 3117 "ietf-languages-announcements@iana.org" mailing list. 3119 Each registration form sent to IANA contains a single record for 3120 incorporation into the registry. The form will be sent to 3121 "iana@iana.org" by the Language Subtag Reviewer. It will have a 3122 subject line indicating whether the enclosed form represents an 3123 insertion of a new record (indicated by the word "INSERT" in the 3124 subject line) or a replacement of an existing record (indicated by 3125 the word "MODIFY" in the subject line). At no time can a record be 3126 deleted from the registry. 3128 IANA will extract the record from the form and place the inserted or 3129 modified record into the appropriate section of the language subtag 3130 registry, grouping the records by their 'Type' field. Inserted 3131 records can be placed anywhere in the appropriate section; there is 3132 no guarantee of the order of the records beyond grouping them 3133 together by 'Type'. Modified records overwrite the record they 3134 replace. 3136 Whenever an entry is created or modified in the registry, the 'File- 3137 Date' record at the start of the registry is updated to reflect the 3138 most recent modification date in the [RFC3339] "full-date" format: 3139 included in any request to insert or modify records will be a new 3140 File-Date record indicating the acceptance date of the record. This 3141 record is to be placed first in the registry, replacing the existing 3142 File-Date record. In the event that the File-Date record present in 3143 the registry has a later date than the record being inserted or 3144 modified, then the latest (most recent) record will be preserved. 3145 IANA should attempt to process multiple registration requests in 3146 order according to the File-Date in the form, since one registration 3147 could otherwise cause a more recent change to be overwritten. 3149 The updated registry file MUST use the UTF-8 character encoding and 3150 IANA MUST check the registry file for proper encoding. Non-ASCII 3151 characters can be sent to IANA by attaching the registration form to 3152 the email message or by using various encodings in the mail message 3153 body (UTF-8 is recommended). IANA will verify any unclear or 3154 corrupted characters with the Language Subtag Reviewer prior to 3155 posting the updated registry. 3157 IANA will also archive and make publicly available from 3158 "http://www.iana.org/assignments/lang-subtags-templates/" each 3159 registration form. Note that multiple registrations can pertain to 3160 the same record in the registry. 3162 Developers who are dependent upon the language subtag registry 3163 sometimes would like to be informed of changes in the registry so 3164 that they can update their implementations. When any change is made 3165 to the language subtag registry, IANA will send an announcement 3166 message to "ietf-languages-announcements@iana.org" (a self- 3167 subscribing list that only IANA can post to). 3169 5.2. Extensions Registry 3171 The Language Tag Extensions Registry can contain at most 35 records 3172 and thus changes to this registry are expected to be very infrequent. 3174 Future work by IANA on the Language Tag Extensions Registry is 3175 limited to two cases. First, the IESG MAY request that new records 3176 be inserted into this registry from time to time. These requests 3177 MUST include the record to insert in the exact format described in 3178 Section 3.7. In addition, there MAY be occasional requests from the 3179 maintaining authority for a specific extension to update the contact 3180 information or URLs in the record. These requests MUST include the 3181 complete, updated record. IANA is not responsible for validating the 3182 information provided, only that it is properly formatted. IANA 3183 SHOULD take reasonable steps to ascertain that the request comes from 3184 the maintaining authority named in the record present in the 3185 registry. 3187 6. Security Considerations 3189 Language tags used in content negotiation, like any other information 3190 exchanged on the Internet, might be a source of concern because they 3191 might be used to infer the nationality of the sender, and thus 3192 identify potential targets for surveillance. 3194 This is a special case of the general problem that anything sent is 3195 visible to the receiving party and possibly to third parties as well. 3196 It is useful to be aware that such concerns can exist in some cases. 3198 The evaluation of the exact magnitude of the threat, and any possible 3199 countermeasures, is left to each application protocol (see BCP 72 3200 [RFC3552] for best current practice guidance on security threats and 3201 defenses). 3203 The language tag associated with a particular information item is of 3204 no consequence whatsoever in determining whether that content might 3205 contain possible homographs. The fact that a text is tagged as being 3206 in one language or using a particular script subtag provides no 3207 assurance whatsoever that it does not contain characters from scripts 3208 other than the one(s) associated with or specified by that language 3209 tag. 3211 Since there is no limit to the number of variant, private use, and 3212 extension subtags, and consequently no limit on the possible length 3213 of a tag, implementations need to guard against buffer overflow 3214 attacks. See Section 4.4 for details on language tag truncation, 3215 which can occur as a consequence of defenses against buffer overflow. 3217 Although the specification of valid subtags for an extension (see 3218 Section 3.7) MUST be available over the Internet, implementations 3219 SHOULD NOT mechanically depend on it being always accessible, to 3220 prevent denial-of-service attacks. 3222 7. Character Set Considerations 3224 The syntax in this document requires that language tags use only the 3225 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 3226 character sets, so the composition of language tags shouldn't have 3227 any character set issues. 3229 The rendering of text based on the language tag is not addressed 3230 here. Historically, some processes have relied on the use of 3231 character set/encoding information (or other external information) in 3232 order to infer how a specific string of characters should be 3233 rendered. Notably this applies to language- and culture-specific 3234 variations of Han ideographs as used in Japanese, Chinese, and 3235 Korean, where use of, for example, a Japanese character encoding such 3236 as EUC-JP implies that the text itself is in Japanese. When language 3237 tags are applied to spans of text, rendering engines might be able to 3238 use that information to better select fonts or make other rendering 3239 choices, particularly where languages with distinct writing 3240 traditions use the same characters. 3242 8. Changes from RFC 4646 3244 The main goal for this revision of this document was to incorporate 3245 two new parts of ISO 639 (ISO 639-3 and ISO 639-5) and their 3246 attendant sets of language codes into the IANA Language Subtag 3247 Registry. This permits the identification of many more languages and 3248 language collections than previously supported. 3250 The specific changes in this document to meet these goals are: 3252 o Defines the incorporation of ISO 639-3 and ISO 639-5 codes for use 3253 as primary and extended language subtags. It also permanently 3254 reserves and disallows the use of additional 'extlang' subtags. 3255 The changes necessary to achieve this were: 3257 * Modified the ABNF comments. 3259 * Updated various registration and stability requirements 3260 sections to reference ISO 639-3 and ISO 639-5 in addition to 3261 ISO 639-1 and ISO 639-2. 3263 * Edited the text to eliminate references to extended language 3264 subtags where they are no longer used. 3266 * Explained the change in the section on extended language 3267 subtags. 3269 o Changed the ABNF related to grandfathered tags. The irregular 3270 tags are now listed. Well-formed grandfathered tags are now 3271 described by the 'langtag' production and the 'grandfathered' 3272 production was removed as a result. Also: added description of 3273 both types of grandfathered tags to Section 2.2.8. 3275 o Added the paragraph on "collections" to Section 4.1. 3277 o Changed the capitalization rules for 'Tag' fields in Section 3.1. 3279 o Split section 3.1 up into subsections. 3281 o Modified section 3.5 to allow Suppress-Script fields to be added, 3282 modified, or removed via the registration process. This was an 3283 erratum from RFC 4646. 3285 o Modified examples that used region code 'CS' (formerly Serbia and 3286 Montenegro) to use 'RS' (Serbia) instead. 3288 o Modified the rules for creating and maintaining record 3289 'Description' fields to prevent duplicates, including inverted 3290 duplicates. 3292 o Removed the lengthy description of why RFC 4646 was created from 3293 this section, which also caused the removal of the reference to 3294 XML Schema. 3296 o Modified the text in section 2.1 to place more emphasis on the 3297 fact that language tags are not case sensitive. 3299 o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" 3300 and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the 3301 Suppress-Script on 'Latn' with 'fr'. 3303 o Changed the requirements for well-formedness to make singleton 3304 repetition checking optional (it is required for validity 3305 checking) in Section 2.2.9. 3307 o Changed the text in Section 2.2.9 referring to grandfathered 3308 checking to note that the list is now included in the ABNF. 3310 o Modified and added text to Section 3.2. The job description was 3311 placed first. A note was added making clear that the Language 3312 Subtag Reviewer may delegate various non-critical duties, 3313 including list moderation. Finally, additional text was added to 3314 make the appointment process clear and to clarify that decisions 3315 and performance of the reviewer are appealable. 3317 o Added text to Section 3.5 clarifying that the 3318 ietf-languages@iana.org list is operated by whomever the IESG 3319 appoints. 3321 o Added text to Section 3.1.5 clarifying that the first Description 3322 in a 'language' record matches the corresponding Reference Name 3323 for the language in ISO 639-3. 3325 o Modified Section 2.2.9 to define classes of conformance related to 3326 specific tags (formerly 'well-formed' and 'valid' referred to 3327 implementations). Notes were added about the removal of 'extlang' 3328 from the ABNF provided in RFC 4646, allowing for well-formedness 3329 using this older definition. Reference to RFC 3066 well- 3330 formedness was also added. 3332 o Added text to the end of Section 3.1.2 noting that future versions 3333 of this document might add new field types to the Registry format 3334 and recommending that implementations ignore any unrecognized 3335 fields. 3337 o Added text about what the lack of a Suppress-Script field means in 3338 a record to Section 3.1.9. 3340 o Added text allowing the correction of misspellings and typographic 3341 errors to Section 3.1.5. 3343 o Added text to Section 3.1.8 disallowing Prefix field conflicts 3344 (such as circular prefix references). 3346 o Modified text in Section 3.5 to require the subtag reviewer to 3347 announce his/her decision (or extension) following the two-week 3348 period. Also clarified that any decision or failure to decide can 3349 be appealed. 3351 o Modified text in Section 4.1 to include the (heretofore anecdotal) 3352 guiding principle of tag choice, and clarifying the non-use of 3353 script subtags in non-written applications. Also updated examples 3354 in this section to use Chamic languages as an example of language 3355 collections. 3357 o Prohibited multiple use of the same variant in a tag (i.e. "de- 3358 1901-1901"). Previously this was only a recommendation 3359 ("SHOULD"). 3361 o Removed inappropriate [RFC2119] language from the illustration in 3362 Section 4.4.1. 3364 o Replaced the example of deprecating "zh-guoyu" with "zh- 3365 hakka"->"hak" in Section 4.5, noting that it was this document 3366 that caused the change. 3368 o Replaced the section in Section 4.1 dealing with "mul"/"und" to 3369 include the subtags 'zxx' and 'mis', as well as the tag 3370 "i-default". A normative reference to RFC 2277 was added, along 3371 with an informative reference to MARC21. 3373 o Added text to Section 3.5 clarifying that any modifications of a 3374 registration request must be sent to the ietf-languages@iana.org 3375 list before submission to IANA. 3377 o Changed the ABNF for the record-jar format from using the LWSP 3378 production to use a folding whitespace production similar to obs- 3379 FWS in [RFC5234]. This effectively prevents unintentional blank 3380 lines inside a field. 3382 o Clarified and revised text in Section 3.3, Section 3.5, and 3383 Section 5.1 to clarify that the Language Subtag Reviewer sends the 3384 complete registration forms to IANA, that IANA extracts the record 3385 from the form, and that the forms must also be archived separately 3386 from the registry. 3388 o Added text to Section 5 requiring IANA to send an announcement to 3389 an ietf-languages-announce list whenever the registry is updated. 3391 o Modification of the registry to use UTF-8 as its character 3392 encoding. This also entails additional instructions to IANA and 3393 the Language Subtag Reviewer in the registration process. 3395 o Modified the rules in Section 2.2.4 so that "exceptionally 3396 reserved" ISO 3166-1 codes other than 'UK' were included into the 3397 registry. In particular, this allows the code 'EU' (European 3398 Union) to be used to form language tags or (more commonly) for 3399 applications that use the registry for region codes to reference 3400 this subtag. 3402 o Modified the IANA considerations section (Section 5) to remove 3403 unnecessary normative [RFC2119] language. 3405 9. References 3407 9.1. Normative References 3409 [ISO639-1] 3410 International Organization for Standardization, "ISO 639- 3411 1:2002. Codes for the representation of names of languages 3412 -- Part 1: Alpha-2 code", 2002. 3414 [ISO639-2] 3415 International Organization for Standardization, "ISO 639- 3416 2:1998. Codes for the representation of names of languages 3417 -- Part 2: Alpha-3 code, first edition", 1998. 3419 [ISO639-3] 3420 International Organization for Standardization, "ISO 639- 3421 3:2007. Codes for the representation of names of languages 3422 -- Part 3: Alpha-3 code for comprehensive coverage of 3423 languages", 2007. 3425 [ISO639-5] 3426 International Organization for Standardization, "ISO 639- 3427 5:1998. Codes for the representation of names of languages 3428 -- Part 5: Alpha-3 code for language families and groups", 3429 May 2008. 3431 [ISO15924] 3432 International Organization for Standardization, "ISO 3433 15924:2004. Information and documentation -- Codes for the 3434 representation of names of scripts", January 2004. 3436 [ISO3166-1] 3437 International Organization for Standardization, "ISO 3166- 3438 1:2006. Codes for the representation of names of countries 3439 and their subdivisions -- Part 1: Country codes", 3440 November 2006. 3442 [UN_M.49] Statistics Division, United Nations, "Standard Country or 3443 Area Codes for Statistical Use", Revision 4 (United 3444 Nations publication, Sales No. 98.XVII.9, June 1999. 3446 [UAX14] Freitag, A., "Unicode Standard Annex #14: Line Breaking 3447 Properties", August 2006, 3448 . 3450 [ISO646] International Organization for Standardization, "ISO/IEC 3451 646:1991, Information technology -- ISO 7-bit coded 3452 character set for information interchange.", 1991. 3454 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3455 3", BCP 9, RFC 2026, October 1996. 3457 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 3458 the IETF Standards Process", BCP 11, RFC 2028, 3459 October 1996. 3461 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3462 Requirement Levels", BCP 14, RFC 2119, March 1997. 3464 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and 3465 Languages", BCP 18, RFC 2277, January 1998. 3467 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3468 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 3469 October 1998. 3471 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 3472 Understanding Concerning the Technical Work of the 3473 Internet Assigned Numbers Authority", RFC 2860, June 2000. 3475 [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the 3476 Internet: Timestamps", RFC 3339, July 2002. 3478 [RFC4645] Ewell, D., "Initial Language Subtag Registry", RFC 4645, 3479 September 2006. 3481 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 3482 BCP 47, RFC 4647, September 2006. 3484 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 3485 Specifications: ABNF", STD 68, RFC 5234, January 2008. 3487 9.2. Informative References 3489 [draft-4645bis] 3490 Ewell, D., Ed., "Update to the Language Subtag Registry", 3491 November 2008, . 3494 [iso639.prin] 3495 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 3496 Committee: Working principles for ISO 639 maintenance", 3497 March 2000, 3498 . 3501 [record-jar] 3502 Raymond, E., "The Art of Unix Programming", 2003, 3503 . 3505 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 3506 Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. 3507 ISBN 0-321-49081-0)", January 2007. 3509 [UTS35] Davis, M., "Unicode Technical Standard #35: Locale Data 3510 Markup Language (LDML)", December 2007, 3511 . 3513 [RFC1766] Alvestrand, H., "Tags for the Identification of 3514 Languages", RFC 1766, March 1995. 3516 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 3517 Part Three: Message Header Extensions for Non-ASCII Text", 3518 RFC 2047, November 1996. 3520 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 3521 Word Extensions: 3522 Character Sets, Languages, and Continuations", RFC 2231, 3523 November 1997. 3525 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 3526 10646", RFC 2781, February 2000. 3528 [RFC3066] Alvestrand, H., "Tags for the Identification of 3529 Languages", RFC 3066, January 2001. 3531 [RFC3282] Alvestrand, H., "Content Language Headers", RFC 3282, 3532 May 2002. 3534 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 3535 Text on Security Considerations", BCP 72, RFC 3552, 3536 July 2003. 3538 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 3539 10646", STD 63, RFC 3629, November 2003. 3541 [RFC4646] Phillips, A. and M. Davis, "Tags for Identifying 3542 Languages", BCP 47, RFC 4646, September 2006. 3544 Appendix A. Acknowledgements 3546 Any list of contributors is bound to be incomplete; please regard the 3547 following as only a selection from the group of people who have 3548 contributed to make this document what it is today. 3550 The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the 3551 precursors of this document, made enormous contributions directly or 3552 indirectly to this document and are generally responsible for the 3553 success of language tags. 3555 The following people contributed to this document: 3557 Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, 3558 Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion 3559 Gunn, Alfred Hoenes, Kent Karlsson, Chris Newman, Randy Presuhn, 3560 Stephen Silver, Shawn Steele, and many, many others. 3562 Very special thanks must go to Harald Tveit Alvestrand, who 3563 originated RFCs 1766 and 3066, and without whom this document would 3564 not have been possible. 3566 Special thanks go to Michael Everson, who served as the Language Tag 3567 Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as 3568 the Language Subtag Reviewer since the adoption of RFC 4646. 3570 Special thanks also to Doug Ewell, for his production of the first 3571 complete subtag registry, his work to support and maintain new 3572 registrations, and his careful editorship of both RFC 4645 and 3573 [draft-4645bis]. 3575 Appendix B. Examples of Language Tags (Informative) 3577 Simple language subtag: 3579 de (German) 3581 fr (French) 3583 ja (Japanese) 3585 i-enochian (example of a grandfathered tag) 3587 Language subtag plus Script subtag: 3589 zh-Hant (Chinese written using the Traditional Chinese script) 3591 zh-Hans (Chinese written using the Simplified Chinese script) 3593 sr-Cyrl (Serbian written using the Cyrillic script) 3595 sr-Latn (Serbian written using the Latin script) 3597 Extended language subtags and their primary language subtag 3598 counterparts: 3600 zh-cmn-Hans-CN (Chinese, Mandarin, Simplified script, as used in 3601 China) 3603 cmn-Hans-CN (Mandarin Chinese, Simplified script, as used in 3604 China) 3606 zh-yue-HK (Chinese, Cantonese, as used in Hong Kong SAR) 3608 yue-HK (Cantonese Chinese, as used in Hong Kong SAR) 3610 Language-Script-Region: 3612 zh-Hans-CN (Chinese written using the Simplified script as used in 3613 mainland China) 3615 sr-Latn-RS (Serbian written using the Latin script as used in 3616 Serbia) 3618 Language-Variant: 3620 sl-rozaj (Resian dialect of Slovenian) 3621 sl-rozaj-biske (San Giorgio dialect of Resian dialect of 3622 Slovenian) 3624 sl-nedis (Nadiza dialect of Slovenian) 3626 Language-Region-Variant: 3628 de-CH-1901 (German as used in Switzerland using the 1901 variant 3629 [orthography]) 3631 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 3633 Language-Script-Region-Variant: 3635 hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as 3636 used in Italy) 3638 Language-Region: 3640 de-DE (German for Germany) 3642 en-US (English as used in the United States) 3644 es-419 (Spanish appropriate for the Latin America and Caribbean 3645 region using the UN region code) 3647 Private use subtags: 3649 de-CH-x-phonebk 3651 az-Arab-x-AZE-derbend 3653 Private use registry values: 3655 x-whatever (private use using the singleton 'x') 3657 qaa-Qaaa-QM-x-southern (all private tags) 3659 de-Qaaa (German, with a private script) 3661 sr-Latn-QM (Serbian, Latin-script, private region) 3663 sr-Qaaa-RS (Serbian, private script, for Serbia) 3665 Tags that use extensions (examples ONLY: extensions MUST be defined 3666 by revision or update to this document or by RFC): 3668 en-US-u-islamcal 3670 zh-CN-a-myext-x-private 3672 en-a-myext-b-another 3674 Some Invalid Tags: 3676 de-419-DE (two region tags) 3678 a-DE (use of a single-character subtag in primary position; note 3679 that there are a few grandfathered tags that start with "i-" that 3680 are valid) 3682 ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter 3683 prefix) 3685 Appendix C. Examples of Registration Forms 3686 LANGUAGE SUBTAG REGISTRATION FORM 3687 1. Name of requester: Han Steenwijk 3688 2. E-mail address of requester: han.steenwijk @ unipd.it 3689 3. Record Requested: 3691 Type: variant 3692 Subtag: biske 3693 Description: The San Giorgio dialect of Resian 3694 Description: The Bila dialect of Resian 3695 Prefix: sl-rozaj 3696 Comments: The dialect of San Giorgio/Bila is one of the 3697 four major local dialects of Resian 3699 4. Intended meaning of the subtag: The local variety of Resian as 3700 spoken in San Giorgio/Bila 3702 5. Reference to published description of the language (book or 3703 article): 3704 -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich 3705 govorov, Varsava - Peterburg: Vende - Kozancikov, 1875. 3707 LANGUAGE SUBTAG REGISTRATION FORM 3708 1. Name of requester: Jaska Zedlik 3709 2. E-mail address of requester: jz53 @ zedlik.com 3710 3. Record Requested: 3712 Type: variant 3713 Subtag: tarask 3714 Description: Belarusian in Taraskievica orthography 3715 Prefix: be 3716 Comments: The subtag represents Branislau Taraskievic's Belarusian 3717 orthography as published in "Bielaruski klasycny pravapis" by Juras 3718 Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka 3719 (Vilnia-Miensk 2005). 3721 4. Intended meaning of the subtag: 3723 The subtag is intended to represent the Belarusian orthography as 3724 published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk 3725 Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005). 3727 5. Reference to published description of the language (book or article): 3729 Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd. 3730 "Bielaruskaha kamitetu", 1929, 5th edition. 3732 Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier. 3733 Bielaruski klasycny pravapis. Vilnia-Miensk, 2005. 3735 6. Any other relevant information: 3737 Belarusian in Taraskievica orthography became widely used, especially in 3738 Belarusian-speaking Internet segment, but besides this some books and 3739 newspapers are also printed using this orthography of Belarusian. 3741 Authors' Addresses 3743 Addison Phillips (editor) 3744 Lab126 3746 Email: addison@inter-locale.com 3747 URI: http://www.inter-locale.com 3749 Mark Davis (editor) 3750 Google 3752 Email: mark.davis@google.com 3754 Full Copyright Statement 3756 Copyright (C) The IETF Trust (2008). 3758 This document is subject to the rights, licenses and restrictions 3759 contained in BCP 78, and except as set forth therein, the authors 3760 retain all their rights. 3762 This document and the information contained herein are provided on an 3763 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 3764 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 3765 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 3766 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 3767 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 3768 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 3770 Intellectual Property 3772 The IETF takes no position regarding the validity or scope of any 3773 Intellectual Property Rights or other rights that might be claimed to 3774 pertain to the implementation or use of the technology described in 3775 this document or the extent to which any license under such rights 3776 might or might not be available; nor does it represent that it has 3777 made any independent effort to identify any such rights. Information 3778 on the procedures with respect to rights in RFC documents can be 3779 found in BCP 78 and BCP 79. 3781 Copies of IPR disclosures made to the IETF Secretariat and any 3782 assurances of licenses to be made available, or the result of an 3783 attempt made to obtain a general license or permission for the use of 3784 such proprietary rights by implementers or users of this 3785 specification can be obtained from the IETF on-line IPR repository at 3786 http://www.ietf.org/ipr. 3788 The IETF invites any interested party to bring to its attention any 3789 copyrights, patents or patent applications, or other proprietary 3790 rights that may cover technology that may be required to implement 3791 this standard. Please address the information to the IETF at 3792 ietf-ipr@ietf.org.