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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 Quest Software 4 Expires: December 4, 2005 M. Davis, Ed. 5 IBM 6 June 02, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-03 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 December 4, 2005. 36 Copyright Notice 38 Copyright (C) The Internet Society (2005). 40 Abstract 42 This document describes the structure, content, construction, and 43 semantics of language tags for use in cases where it is desirable to 44 indicate the language used in an information object. It also 45 describes how to register values for use in language tags and the 46 creation of user defined extensions for private interchange. This 47 document obsoletes RFC 3066 (which replaced RFC 1766). 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4 53 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 2.1.1 Length Considerations . . . . . . . . . . . . . . . . 6 55 2.2 Language Subtag Sources and Interpretation . . . . . . . . 7 56 2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 9 57 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 11 58 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 11 59 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 12 60 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 13 61 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 14 62 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 15 63 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 16 64 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 16 65 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 18 66 3.1 Format of the IANA Language Subtag Registry . . . . . . . 18 67 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 23 68 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 24 69 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 27 70 3.5 Possibilities for Registration . . . . . . . . . . . . . . 30 71 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 32 72 3.7 Initialization of the Registry . . . . . . . . . . . . . . 35 73 4. Formation and Processing of Language Tags . . . . . . . . . . 38 74 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 38 75 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 40 76 4.3 Canonicalization of Language Tags . . . . . . . . . . . . 41 77 4.4 Considerations for Private Use Subtags . . . . . . . . . . 43 78 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 45 80 7. Character Set Considerations . . . . . . . . . . . . . . . . . 46 81 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 47 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51 83 9.1 Normative References . . . . . . . . . . . . . . . . . . . 51 84 9.2 Informative References . . . . . . . . . . . . . . . . . . 52 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 53 86 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54 87 B. Examples of Language Tags (Informative) . . . . . . . . . . . 55 88 C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 58 89 Intellectual Property and Copyright Statements . . . . . . . . 62 91 1. Introduction 93 Human beings on our planet have, past and present, used a number of 94 languages. There are many reasons why one would want to identify the 95 language used when presenting or requesting information. 97 Information about a user's language preferences commonly needs to be 98 identified so that appropriate processing can be applied. For 99 example, the user's language preferences in a browser can be used to 100 select web pages appropriately. A choice of language preference can 101 also be used to select among tools (such as dictionaries) to assist 102 in the processing or understanding of content in different languages. 104 In addition, knowledge about the particular language used by some 105 piece of information content may be useful or even required by some 106 types of information processing; for example spell-checking, 107 computer-synthesized speech, Braille transcription, or high-quality 108 print renderings. 110 One means of indicating the language used is by labeling the 111 information content with a language identifier. These identifiers 112 can also be used to specify user preferences when selecting 113 information content, or for labeling additional attributes of content 114 and associated resources. 116 These identifiers can also be used to indicate additional attributes 117 of content that are closely related to the language. In particular, 118 it is often necessary to indicate specific information about the 119 dialect, writing system, or orthography used in a document or 120 resource, as these attributes may be important for the user to obtain 121 information in a form that they can understand, or important in 122 selecting appropriate processing resources for the given content. 124 This document specifies an identifier mechanism and a registration 125 function for values to be used with that identifier mechanism. It 126 also defines a mechanism for private use values and future extension. 128 This document replaces RFC 3066, which replaced RFC 1766. For a list 129 of changes in this document, see Section 8. 131 The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 133 document are to be interpreted as described in RFC 2119 [10]. 135 2. The Language Tag 137 2.1 Syntax 139 The language tag is composed of one or more parts: A primary language 140 subtag and a (possibly empty) series of subsequent subtags. Subtags 141 are distinguished by their length, position in the subtag sequence, 142 and content, so that each type of subtag can be recognized solely by 143 these features. This makes it possible to construct a parser that 144 can extract and assign some semantic information to the subtags, even 145 if specific subtag values are not recognized. Thus a parser need not 146 have an up-to-date copy of the registered subtag values to perform 147 most searching and matching operations. 149 The syntax of this tag in ABNF [7] is: 151 Language-Tag = (lang 152 *3("-" extlang) 153 ["-" script] 154 ["-" region] 155 *("-" variant) 156 *("-" extension) 157 ["-" privateuse]) 158 / privateuse ; private-use tag 159 / grandfathered ; grandfathered registrations 161 lang = 2*4ALPHA ; shortest ISO 639 code 162 / registered-lang 163 extlang = 3ALPHA ; reserved for future use 164 script = 4ALPHA ; ISO 15924 code 165 region = 2ALPHA ; ISO 3166 code 166 / 3DIGIT ; UN country number 167 variant = 5*8alphanum ; registered variants 168 / ( DIGIT 3alphanum ) 169 extension = singleton 1*("-" (2*8alphanum)) 170 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 171 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 172 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 173 ; Single letters: x/X is reserved for private use 174 registered-lang = 4*8ALPHA ; registered language subtag 175 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 176 ; grandfathered registration 177 ; Note: i is the only singleton 178 ; that starts a grandfathered tag 179 alphanum = (ALPHA / DIGIT) ; letters and numbers 181 Figure 1: Language Tag ABNF 183 The character "-" is HYPHEN-MINUS (ABNF: %x2D). All subtags have a 184 maximum length of eight characters. Note that there is a subtlety in 185 the ABNF for 'variant': variants starting with a digit may be only 186 four characters long, while those starting with a letter must be at 187 least five characters long. 189 Whitespace is not permitted in a language tag. For examples of 190 language tags, see Appendix B. 192 Note that although [7] refers to octets, the language tags described 193 in this document are sequences of characters from the US-ASCII 194 repertoire. Language tags may be used in documents and applications 195 that use other encodings, so long as these encompass the US-ASCII 196 repertoire. An example of this would be an XML document that uses 197 the UTF-16LE [12] encoding of Unicode [20]. 199 The tags and their subtags, including private-use and extensions, are 200 to be treated as case insensitive: there exist conventions for the 201 capitalization of some of the subtags, but these should not be taken 202 to carry meaning. 204 For example: 206 o [ISO 639] [1] recommends that language codes be written in lower 207 case ('mn' Mongolian). 209 o [ISO 3166] [4] recommends that country codes be capitalized ('MN' 210 Mongolia). 212 o [ISO 15924] [3] recommends that script codes use lower case with 213 the initial letter capitalized ('Cyrl' Cyrillic). 215 However, in the tags defined by this document, the uppercase US-ASCII 216 letters in the range 'A' through 'Z' are considered equivalent and 217 mapped directly to their US-ASCII lowercase equivalents in the range 218 'a' through 'z'. Thus the tag "mn-Cyrl-MN" is not distinct from "MN- 219 cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these 220 variations conveys the same meaning: Mongolian written in the 221 Cyrillic script as used in Mongolia. 223 2.1.1 Length Considerations 225 Although neither the ABNF nor other guidelines in this document 226 provide a fixed upper limit on the number of subtags in a Language 227 Tag (and thus the upper bound on the size of a tag) and it is 228 possible to envision quite long and complex subtag sequences, in 229 practice these are rare because additional granularity in tags seldom 230 adds useful distinguishing information and because longer, more 231 granular tags interefere with the meaning, understanding, and 232 processing of language tags. 234 A conformant implementation MAY refuse to support the storage of 235 language tags which exceed a specified length. For an example, see 236 [RFC 2231] [22]. Any such limitation SHOULD be clearly documented, 237 and such documentation SHOULD include the disposition of any longer 238 tags (for example, whether an error value is generated or the 239 language tag is truncated). If truncation is permitted it MUST NOT 240 permit a subtag to be divided. Implementations that restrict storage 241 should consider removing extensions before processing. A protocol 242 that allows tags to be truncated at an arbitrary limit, without 243 giving any indication of what that limit is, has the potential for 244 causing harm by changing the meaning of tags in substantial ways. 246 In particular, variant subtags SHOULD be used only with their 247 recommended prefix. In practice, this limits most tags to a sequence 248 of four subtags, and thus a maximum length of 26 characters 249 (excluding any extensions or private use sequences). This is because 250 subtags are limited to a length of eight characters and the extlang, 251 script, and region subtags are limited to even fewer characters. See 252 Section 4.1 for more information on selecting the most appropriate 253 Language Tag. 255 Longer tags are possible. The longest tags (excluding extensions) 256 could have a length of up to 62 characters, as shown below. 257 Implementations MUST be able to handle tags of this length without 258 truncation. Support for tags of up to 64 characters is RECOMMENDED. 259 Implementations MAY support longer tags. 261 Here is how the 62-character length of the longest practical tag 262 (excluding extensions) is derived: 264 language = 3 265 extlang1 = 4 266 extlang2 = 4 (unlikely: needs prefix="language-extlang1") 267 extlang3 = 4 (extremely unlikely) 268 script = 5 269 region = 4 (UN M.49) 270 variant1 = 9 271 variant2 = 9 (unlikely: needs prefix="language-variant1") 272 private use 1 = 11 ("-x-" + subtag) 273 private use 2 = 9 274 total = 62 characters 276 Figure 2: Derviation of the Longest Tag 278 2.2 Language Subtag Sources and Interpretation 280 The namespace of language tags and their subtags is administered by 281 the Internet Assigned Numbers Authority (IANA) [13] according to the 282 rules in Section 5 of this document. The registry maintained by IANA 283 is the source for valid subtags: other standards referenced in this 284 section provide the source material for that registry. 286 Terminology in this section: 288 o Tag or tags refers to a complete language tag, such as 289 "fr-Latn-CA". Examples of tags in this document are enclosed in 290 double-quotes ("en-US"). 292 o Subtag refers to a specific section of a tag, delimited by hyphen, 293 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 294 this document are enclosed in single quotes ('Latn'). 296 o Code or codes refers to values defined in external standards (and 297 which are used as subtags in this document). For example, 'Latn' 298 is an [ISO 15924] [3] script code which was used to define the 299 'Latn' script subtag for use in a language tag. Examples of codes 300 in this document are enclosed in single quotes ('en', 'Latn'). 302 The definitions in this section apply to the various subtags within 303 the language tags defined by this document, excepting those 304 "grandfathered" tags defined in Section 2.2.8. 306 Language tags are designed so that each subtag type has unique length 307 and content restrictions. These make identification of the subtag's 308 type possible, even if the content of the subtag itself is 309 unrecognized. This allows tags to be parsed and processed without 310 reference to the latest version of the underlying standards or the 311 IANA registry and makes the associated exception handling when 312 parsing tags simpler. 314 Subtags in the IANA registry that do not come from an underlying 315 standard can only appear in specific positions in a tag. 316 Specifically, they can only occur as primary language subtags or as 317 variant subtags. 319 Note that sequences of private-use and extension subtags MUST occur 320 at the end of the sequence of subtags and MUST NOT be interspersed 321 with subtags defined elsewhere in this document. 323 Single letter and digit subtags are reserved for current or future 324 use. These include the following current uses: 326 o The single letter subtag 'x' is reserved to introduce a sequence 327 of private-use subtags. The interpretation of any private-use 328 subtags is defined solely by private agreement and is not defined 329 by the rules in this section or in any standard or registry 330 defined in this document. 332 o All other single letter subtags are reserved to introduce 333 standardized extension subtag sequences as described in 334 Section 3.6. 336 The single letter subtag 'i' is used by some grandfathered tags, such 337 as "i-enochian", where it always appears in the first position and 338 cannot be confused with an extension. 340 2.2.1 Primary Language Subtag 342 The primary language subtag is the first subtag in a language tag 343 (with the exception of private-use and certain grandfathered tags) 344 and cannot be omitted. The following rules apply to the primary 345 language subtag: 347 1. All two character language subtags were defined in the IANA 348 registry according to the assignments found in the standard ISO 349 639 Part 1, "ISO 639-1:2002, Codes for the representation of 350 names of languages -- Part 1: Alpha-2 code" [ISO 639-1] [1], or 351 using assignments subsequently made by the ISO 639 Part 1 352 maintenance agency or governing standardization bodies. 354 2. All three character language subtags were defined in the IANA 355 registry according to the assignments found in ISO 639 Part 2, 356 "ISO 639-2:1998 - Codes for the representation of names of 357 languages -- Part 2: Alpha-3 code - edition 1" [ISO 639-2] [2], 358 or assignments subsequently made by the ISO 639 Part 2 359 maintenance agency or governing standardization bodies. 361 3. The subtags in the range 'qaa' through 'qtz' are reserved for 362 private use in language tags. These subtags correspond to codes 363 reserved by ISO 639-2 for private use. These codes MAY be used 364 for non-registered primary-language subtags (instead of using 365 private-use subtags following 'x-'). Please refer to Section 4.4 366 for more information on private use subtags. 368 4. All four character language subtags are reserved for possible 369 future standardization. 371 5. All language subtags of 5 to 8 characters in length in the IANA 372 registry were defined via the registration process in Section 3.4 373 and MAY be used to form the primary language subtag. At the time 374 this document was created, there were no examples of this kind of 375 subtag and future registrations of this type will be discouraged: 376 primary languages are strongly RECOMMENDED for registration with 377 ISO 639 and proposals rejected by ISO 639/RA will be closely 378 scrutinized before they are registered with IANA. 380 6. The single character subtag 'x' as the primary subtag indicates 381 that the language tag consists solely of subtags whose meaning is 382 defined by private agreement. For example, in the tag "x-fr-CH", 383 the subtags 'fr' and 'CH' should not be taken to represent the 384 French language or the country of Switzerland (or any other value 385 in the IANA registry) unless there is a private agreement in 386 place to do so. See Section 4.4. 388 7. The single character subtag 'i' is used by some grandfathered 389 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 390 grandfathered tags have a primary language subtag in their first 391 position) 393 8. Other values MUST NOT be assigned to the primary subtag except by 394 revision or update of this document. 396 Note: For languages that have both an ISO 639-1 two character code 397 and an ISO 639-2 three character code, only the ISO 639-1 two 398 character code is defined in the IANA registry. 400 Note: For languages that have no ISO 639-1 two character code and for 401 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 402 (Bibliographic) codes differ, only the Terminology code is defined in 403 the IANA registry. At the time this document was created, all 404 languages that had both kinds of three character code were also 405 assigned a two character code; it is not expected that future 406 assignments of this nature will occur. 408 Note: To avoid problems with versioning and subtag choice as 409 experienced during the transition between RFC 1766 and RFC 3066, as 410 well as the canonical nature of subtags defined by this document, the 411 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 412 RA-JAC) has included the following statement in [16]: 414 "A language code already in ISO 639-2 at the point of freezing ISO 415 639-1 shall not later be added to ISO 639-1. This is to ensure 416 consistency in usage over time, since users are directed in Internet 417 applications to employ the alpha-3 code when an alpha-2 code for that 418 language is not available." 420 In order to avoid instability of the canonical form of tags, if a two 421 character code is added to ISO 639-1 for a language for which a three 422 character code was already included in ISO 639-2, the two character 423 code will not be added as a subtag in the registry. See Section 3.3. 425 For example, if some content were tagged with 'haw' (Hawaiian), which 426 currently has no two character code, the tag would not be invalidated 427 if ISO 639-1 were to assign a two character code to the Hawaiian 428 language at a later date. 430 For example, one of the grandfathered IANA registrations is 431 "i-enochian". The subtag 'enochian' could be registered in the IANA 432 registry as a primary language subtag (assuming that ISO 639 does not 433 register this language first), making tags such as "enochian-AQ" and 434 "enochian-Latn" valid. 436 2.2.2 Extended Language Subtags 438 The following rules apply to the extended language subtags: 440 1. Three letter subtags immediately following the primary subtag are 441 reserved for future standardization, anticipating work that is 442 currently under way on ISO 639. 444 2. Extended language subtags MUST follow the primary subtag and 445 precede any other subtags. 447 3. There MAY be up to three extended language subtags. 449 4. Extended language subtags will not be registered except by 450 revision of this document. 452 5. Extended language subtags MUST NOT be used to form language tags 453 except by revision of this document. 455 Extended language subtag records, once they appear in the registry, 456 MUST include exactly one 'Prefix' field indicating an appropriate 457 language subtag or sequence of subtags that MUST always appear as a 458 prefix to the extended language subtag. 460 Example: In a future revision or update of this document, the tag 461 "zh-gan" (registered under RFC 3066) might become a valid non- 462 grandfathered (that is, redundant) tag in which the subtag 'gan' 463 might represent the Chinese dialect 'Gan'. 465 2.2.3 Script Subtag 467 The following rules apply to the script subtags: 469 1. All four character subtags were defined according to ISO 15924 470 [3]--"Codes for the representation of the names of scripts": 471 alpha-4 script codes, or subsequently assigned by the ISO 15924 472 maintenance agency or governing standardization bodies, denoting 473 the script or writing system used in conjunction with this 474 language. 476 2. Script subtags MUST immediately follow the primary language 477 subtag and all extended language subtags and MUST occur before 478 any other type of subtag described below. 480 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 481 use in language tags. These subtags correspond to codes reserved 482 by ISO 15924 for private use. These codes MAY be used for non- 483 registered script values. Please refer to Section 4.4 for more 484 information on private-use subtags. 486 4. Script subtags cannot be registered using the process in 487 Section 3.4 of this document. Variant subtags may be considered 488 for registration for that purpose. 490 Example: "de-Latn" represents German written using the Latin script. 492 2.2.4 Region Subtag 494 The following rules apply to the region subtags: 496 1. The region subtag defines language variations used in a specific 497 region, geographic, or political area. Region subtags MUST 498 follow any language, extended language, or script subtags and 499 MUST precede all other subtags. 501 2. All two character subtags following the primary subtag were 502 defined in the IANA registry according to the assignments found 503 in ISO 3166 [4]--"Codes for the representation of names of 504 countries and their subdivisions - Part 1: Country 505 codes"--alpha-2 country codes or assignments subsequently made by 506 the ISO 3166 maintenance agency or governing standardization 507 bodies. 509 3. All three character codes consisting of digit (numeric) 510 characters were defined in the IANA registry according to the 511 assignments found in UN Standard Country or Area Codes for 512 Statistical Use [5] or assignments subsequently made by the 513 governing standards body. Note that not all of the UN M.49 codes 514 are defined in the IANA registry: 516 A. UN numeric codes assigned to 'macro-geographical 517 (continental)' or sub-regions not associated with an assigned 518 ISO 3166 alpha-2 code _are_ defined. 520 B. UN numeric codes for 'economic groupings' or 'other 521 groupings' are _not_ defined in the IANA registry and MUST 522 NOT be used to form language tags. 524 C. UN numeric codes for countries with ambiguous ISO 3166 525 alpha-2 codes as defined in Section 3.3 are defined in the 526 registry and are canonical for the given country or region 527 defined. 529 D. The alphanumeric codes in Appendix X of the UN document are 530 _not_ defined and MUST NOT be used to form language tags. 531 (At the time this document was created these values match the 532 ISO 3166 alpha-2 codes.) 534 4. There may be at most one region subtag in a language tag. 536 5. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 537 reserved for private use in language tags. These subtags 538 correspond to codes reserved by ISO 3166 for private use. These 539 codes MAY be used for private use region subtags (instead of 540 using a private-use subtag sequence). Please refer to 541 Section 4.4 for more information on private use subtags. 543 "de-CH" represents German ('de') as used in Switzerland ('CH'). 545 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 546 ('Latn') as used in Serbia and Montenegro ('CS'). 548 "es-419" represents Spanish ('es') as used in the UN-defined Latin 549 America and Caribbean region ('419'). 551 2.2.5 Variant Subtags 553 The following rules apply to the variant subtags: 555 1. Variant subtags are not associated with any external standard. 556 Variant subtags and their meanings are defined by the 557 registration process defined in Section 3.4. 559 2. Variant subtags MUST follow all of the other defined subtags, but 560 precede any extension or private-use subtag sequences. 562 3. More than one variant MAY be used to form the language tag. 564 4. Variant subtags MUST be registered with IANA according to the 565 rules in Section 3.4 of this document before being used to form 566 language tags. In order to distinguish variants from other types 567 of subtags, registrations must meet the following length and 568 content restrictions: 570 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 571 at least five characters long. 573 2. Variant subtags that begin with a digit (0-9) MUST be at 574 least four characters long. 576 Variant subtag records in the language subtag registry may include 577 one or more 'Prefix' fields, which indicates the language tag or tags 578 that would make a suitable prefix (with other subtags, as 579 appropriate) in forming a language tag with the variant. For 580 example, the subtag 'scouse' has a Prefix of "en", making it suitable 581 to form language tags such as "en-scouse" and "en-GB-scouse", but not 582 suitable for use in a tag such as "zh-scouse" or "it-GB-scouse". 584 "en-scouse" represents the Scouse dialect of English. 586 "de-CH-1996" represents German as used in Switzerland and as written 587 using the spelling reform beginning in the year 1996 C.E. 589 Most variants that share a prefix are mutually exclusive. For 590 example, the German orthographic variantions '1996' and '1901' should 591 not be used in the same tag, as they represent the dates of different 592 spelling reforms. A variant that may be used in combination with 593 another variant should include a 'Prefix' field in its registry 594 record that lists that other variant. For example, if another German 595 variant 'example' were created that made sense to use with '1996', 596 then 'example' should include two Prefix fields: "de" and "de-1996". 598 2.2.6 Extension Subtags 600 The following rules apply to extensions: 602 1. Extension subtags are separated from the other subtags defined 603 in this document by a single-letter subtag ("singleton"). The 604 singleton MUST be one allocated to a registration authority via 605 the mechanism described in Section 3.6 and cannot be the letter 606 'x', which is reserved for private-use subtag sequences. 608 2. Note: Private-use subtag sequences starting with the singleton 609 subtag 'x' are described below. 611 3. An extension MUST follow at least a primary language subtag. 612 That is, a language tag cannot begin with an extension. 613 Extensions extend language tags, they do not override or replace 614 them. For example, "a-value" is not a well-formed language tag, 615 while "de-a-value" is. 617 4. Each singleton subtag MUST appear at most one time in each tag 618 (other than as a private-use subtag). That is, singleton 619 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 620 ccc" is invalid because the subtag 'a' appears twice. Note that 621 the tag "en-a-bbb-x-a-ccc" is valid because the second 622 appearance of the singleton 'a' is in a private use sequence. 624 5. Extension subtags MUST meet all of the requirements for the 625 content and format of subtags defined in this document. 627 6. Extension subtags MUST meet whatever requirements are set by the 628 document that defines their singleton prefix and whatever 629 requirements are provided by the maintaining authority. 631 7. Each extension subtag MUST be from two to eight characters long 632 and consist solely of letters or digits, with each subtag 633 separated by a single '-'. 635 8. Each singleton MUST be followed by at least one extension 636 subtag. For example, the tag "tlh-a-b-foo" is invalid because 637 the first singleton 'a' is followed immediately by another 638 singleton 'b'. 640 9. Extension subtags MUST follow all language, extended language, 641 script, region and variant subtags in a tag. 643 10. All subtags following the singleton and before another singleton 644 are part of the extension. Example: In the tag "fr-a-Latn", the 645 subtag 'Latn' does not represent the script subtag 'Latn' 646 defined in the IANA Language Subtag Registry. Its meaning is 647 defined by the extension 'a'. 649 11. In the event that more than one extension appears in a single 650 tag, the tag SHOULD be canonicalized as described in 651 Section 4.3. 653 For example, if the prefix singleton 'r' and the shown subtags were 654 defined, then the following tag would be a valid example: "en-Latn- 655 GB-boont-r-extended-sequence-x-private" 657 2.2.7 Private Use Subtags 659 The following rules apply to private-use subtags: 661 1. Private-use subtags are separated from the other subtags defined 662 in this document by the reserved single-character subtag 'x'. 664 2. Private-use subtags MUST follow all language, extended language, 665 script, region, variant, and extension subtags in the tag. 666 Another way of saying this is that all subtags following the 667 singleton 'x' MUST be considered private use. Example: The 668 subtag 'US' in the tag "en-x-US" is a private use subtag. 670 3. A tag MAY consist entirely of private-use subtags. 672 4. No source is defined for private use subtags. Use of private use 673 subtags is by private agreement only. 675 For example: Users who wished to utilize SIL Ethnologue for 676 identification might agree to exchange tags such as "az-Arab-x-AZE- 677 derbend". This example contains two private-use subtags. The first 678 is 'AZE' and the second is 'derbend'. 680 2.2.8 Pre-Existing RFC 3066 Registrations 682 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 683 maintain their validity. IANA will maintain these tags in the 684 registry under either the "grandfathered" or "redundant" type. For 685 more information see Section 3.7. 687 It is important to note that all language tags formed under the 688 guidelines in this document were either legal, well-formed tags or 689 could have been registered under RFC 3066. 691 2.2.9 Classes of Conformance 693 Implementations may wish to express their level of conformance with 694 the rules and practices described in this document. There are 695 generally two classes of conforming implementations: "well-formed" 696 processors and "validating" processors. Claims of conformance SHOULD 697 explicitly reference one of these definitions. 699 An implementation that claims to check for well-formed language tags 700 MUST: 702 o Check that the tag and all of its subtags, including extension and 703 private-use subtags, conform to the ABNF or that the tag is on the 704 list of grandfathered tags. 706 o Check that singleton subtags that identify extensions do not 707 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 708 formed. 710 Well-formed processors are strongly encouraged to implement the 711 canonicalization rules contained in Section 4.3. 713 An implementation that claims to be validating MUST: 715 o Check that the tag is well-formed. 717 o Specify the particular registry date for which the implementation 718 performs validation of subtags. 720 o Check that either the tag is a grandfathered tag, or that all 721 language, script, region, and variant subtags consist of valid 722 codes for use in language tags according to the IANA registry as 723 of the particular date specified by the implementation. 725 o Specify which, if any, extension RFCs as defined in Section 3.6 726 are supported, including version, revision, and date. 728 o For any such extensions supported, check that all subtags used in 729 that extension are valid. 731 o For variant and extended language subtags, if the registry 732 contains one or more 'Prefix' fields for that subtag, check that 733 the tag matches at least one prefix. The tag matches if all the 734 subtags in the 'Prefix' also appear in the tag. For example, the 735 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 736 the 'es' language subtag and 'CO' region subtag appear in the tag. 738 3. Registry Format and Maintenance 740 This section defines the Language Subtag Registry and the maintenance 741 and update procedures associated with it. 743 The language subtag registry will be maintained so that, except for 744 extension subtags, it is possible to validate all of the subtags that 745 appear in a language tag under the provisions of this document or its 746 revisions or successors. In addition, the meaning of the various 747 subtags will be unambiguous and stable over time. (The meaning of 748 private-use subtags, of course, is not defined by the IANA registry.) 750 The registry defined under this document contains a comprehensive 751 list of all of the subtags valid in language tags. This allows 752 implementers a straightforward and reliable way to validate language 753 tags. 755 3.1 Format of the IANA Language Subtag Registry 757 The IANA Language Subtag Registry ("the registry") will consist of a 758 text file that is machine readable in the format described in this 759 section, plus copies of the registration forms approved by the 760 Language Subtag Reviewer in accordance with the process described in 761 Section 3.4. With the exception of the registration forms for 762 grandfathered and redundant tags, no registration records will be 763 maintained for the initial set of subtags. 765 The registry will be in a modified record-jar format text file [17]. 766 Lines are limited to 72 characters, including all whitespace. 768 Records are separated by lines containing only the sequence "%%" 769 (%x25.25). 771 Each field can be viewed as a single, logical line of ASCII 772 characters, comprising a field-name and a field-body separated by a 773 COLON character (%x3A). For convenience, the field-body portion of 774 this conceptual entity can be split into a multiple-line 775 representation; this is called "folding". The format of the registry 776 is described by the following ABNF (per [7]): 778 registry = record *("%%" CRLF record) 779 record = 1*( field-name *SP ":" *SP field-body CRLF ) 780 field-name = *(ALPHA / DIGIT / "-") 781 field-body = *(ASCCHAR/LWSP) 782 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 783 UNICHAR = "&#x" 2*6HEXDIG ";" 785 The sequence '..' (%x2E.2E) in a field-body denotes a range of 786 values. Such a range represents all subtags of the same length that 787 are alphabetically within that range, including the values explicitly 788 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 790 Characters from outside the US-ASCII repertoire, as well as the 791 AMPERSAND character ("&", %x26) when it occurs in a field-body are 792 represented by a "Numeric Character Reference" using hexadecimal 793 notation in the style used by XML 1.0 [18] (see 794 ). This consists of the 795 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 796 of the character's code point in ISO/IEC 10646 [6] followed by a 797 closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would 798 be represented by the sequence "€". Note that the hexadecimal 799 notation may have between two and six digits. 801 All fields whose field-body contains a date value use the "full-date" 802 format specified in RFC 3339 [14]. For example: "2004-06-28" 803 represents June 28, 2004 in the Gregorian calendar. 805 The first record in the file contains the single field whose field- 806 name is "File-Date". The field-body of this record contains the last 807 modification date of this copy of the registry, making it possible to 808 compare different versions of the registry. The registry on the IANA 809 website is the most current. Versions with an older date than that 810 one are not up-to-date. 812 File-Date: 2004-06-28 813 %% 815 Subsequent records represent subtags in the registry. Each of the 816 fields in each record MUST occur no more than once, unless otherwise 817 noted below. Each record MUST contain the following fields: 819 o 'Type' 821 * Type's field-value MUST consist of one of the following 822 strings: "language", "extlang", "script", "region", "variant", 823 "grandfathered", and "redundant" and denotes the type of tag or 824 subtag. 826 o Either 'Subtag' or 'Tag' 828 * Subtag's field-value contains the subtag being defined. This 829 field MUST only appear in records of whose Type has one of 830 these values: "language", "extlang", "script", "region", or 831 "variant". 833 * Tag's field-value contains a complete language tag. This field 834 MUST only appear in records whose Type has one of these values: 835 "grandfathered" or "redundant". 837 o Description 839 * Description's field-value contains a non-normative description 840 of the subtag or tag. 842 o Added 844 * Added's field-value contains the date the record was added to 845 the registry. 847 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 848 subtag or tag, with two exceptions. Subtags whose 'Type' field is 849 'script' (in other words, subtags defined by ISO 15924) MUST use 850 titlecase. Subtags whose 'Type' field is 'region' (in other words, 851 subtags defined by ISO 3166) MUST use uppercase. These exceptions 852 mirror the use of case in the underlying standards. 854 The field 'Description' MAY appear more than one time. At least one 855 of the 'Description' fields must contain a description of the tag 856 being registered written or transcribed into the Latin script; the 857 same or additional fields may also include a description in a non- 858 Latin script. The 'Description' field is used for identification 859 purposes and should not be taken to represent the actual native name 860 of the language or variation or to be in any particular language. 861 Most descriptions are taken directly from source standards such as 862 ISO 639 or ISO 3166. 864 Note: Descriptions in registry entries that correspond to ISO 639, 865 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 866 the meaning of that identifier as defined in the source standard at 867 the time it was added to the registry. The description does not 868 replace the content of the source standard itself. The descriptions 869 are not intended to be the English localized names for the subtags. 870 Localization or translation of language tag and subtag descriptions 871 is out of scope of this document. 873 Each record MAY also contain the following fields: 875 o Preferred-Value 877 * For fields of type 'language', 'extlang', 'script', 'region', 878 and 'variant', 'Preferred-Value' contains a subtag of the same 879 'Type' which is preferred for forming the language tag. 881 * For fields of type 'grandfathered' and 'redundant', a canonical 882 mapping to a complete language tag. 884 o Deprecated 886 * Deprecated's field-value contains the date the record was 887 deprecated. 889 o Prefix 891 * Prefix's field-value contains a language tag with which this 892 subtag may be used to form a new language tag, perhaps with 893 other subtags as well. This field MUST only appear in records 894 whose 'Type' field-value is 'variant' or 'extlang'. For 895 example, the 'Prefix' for the variant 'scouse' is 'en', meaning 896 that the tags "en-scouse" and "en-GB-scouse" might be 897 appropriate while the tag "is-scouse" is not. 899 o Comments 901 * Comments contains additional information about the subtag, as 902 deemed appropriate for understanding the registry and 903 implementing language tags using the subtag or tag. 905 o Suppress-Script 907 * Suppress-Script contains a script subtag that SHOULD NOT be 908 used to form language tags with the associated primary language 909 subtag. This field MUST only appear in records whose 'Type' 910 field-value is 'language'. See Section 4.1. 912 The field 'Deprecated' MAY be added to any record via the maintenance 913 process described in Section 3.2 or via the registration process 914 described in Section 3.4. Usually the addition of a 'Deprecated' 915 field is due to the action of one of the standards bodies, such as 916 ISO 3166, withdrawing a code. In some historical cases it may not 917 have been possible to reconstruct the original deprecation date. 918 For these cases, an approximate date appears in the registry. 919 Although valid in language tags, subtags and tags with a 'Deprecated' 920 field are deprecated and validating processors SHOULD NOT generate 921 these subtags. Note that a record that contains a 'Deprecated' field 922 and no corresponding 'Preferred-Value' field has no replacement 923 mapping. 925 Thie field 'Preferred-Value' contains a mapping between the record in 926 which it appears and a tag or subtag which should be preferred when 927 selected language tags. These values form three groups: 929 ISO 639 language codes which were later withdrawn in favor of 930 other codes. These values are mostly a historical curiosity. 932 ISO 3166 region codes which have been withdrawn in favor of a new 933 code. This sometimes happens when a country changes its name or 934 administration in such a way that warrents a new region code. 936 Tags grandfathered from RFC 3066. In many cases these tags have 937 become obsolete because the values they represent were later 938 encoded by ISO 639. 940 Records that contain a 'Preferred-Value' field MUST also have a 941 'Deprecated' field. This field contains a date of deprecation. Thus 942 a language tag processor can use the registry to construct the valid, 943 non-deprecated set of subtags for a given date. In addition, for any 944 given tag, a processor can construct the set of valid language tags 945 that correspond to that tag for all dates up to the date of the 946 registry. The ability to do these mappings may be beneficial to 947 applications that are matching, selecting, for filtering content 948 based on its language tags. 950 It should be noted that 'Preferred-Value' mappings in records of type 951 'region' may not represent exactly the same meaning as the original 952 value. There are many reasons that a country code may be changed and 953 the effect this has on the formation of language tags may depend on 954 the nature of the change in question. 956 In particular, the 'Preferred-Value' field does not imply that 957 content formerly tagged with one tag should be retagged. 959 The field 'Preferred-Value' MUST NOT be modified once created in the 960 registry. The field MAY be added to records of type "grandfathered" 961 and "region" according to the rules in Section 3.2. Otherwise the 962 field MUST NOT be added to any record already in the registry. 964 The 'Preferred-Value' field in records of type "grandfathered" and 965 "redundant" contains whole language tags that are strongly 966 RECOMMENDED for use in place of the record's value. In many cases 967 the mappings were created by deprecation of the tags during the 968 period before this document was adopted. For example, the tag "no- 969 nyn" was deprecated in favor of the ISO 639-1 defined language code 970 'nn'. 972 Records of type 'variant' MAY have more than one field of type 973 'Prefix'. Additional fields of this type MAY be added to a 'variant' 974 record via the registration process. 976 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 978 The field-value of the 'Prefix' field consists of a language tag 979 whose subtags are appropriate to use with this subtag. For example, 980 the variant subtag 'scouse' has a recommended prefix of "en". This 981 means that tags starting with the prefix "en-" are most appropriate 982 with this subtag, so "en-Latn-scouse" and "en-GB-scouse" are both 983 acceptable, while the tag "fr-scouse" is an inappropriate choice. 985 The field of type 'Prefix' MUST NOT be removed from any record. The 986 field-value for this type of field MUST NOT be modified. 988 The field 'Comments' MAY appear more than once per record. This 989 field MAY be inserted or changed via the registration process and no 990 guarantee of stability is provided. The content of this field is not 991 restricted, except by the need to register the information, the 992 suitability of the request, and by reasonable practical size 993 limitations. Long screeds about a particular subtag are frowned 994 upon. 996 The field 'Suppress-Script' MUST only appear in records whose 'Type' 997 field-value is 'language'. This field may appear at most one time in 998 a record. This field indicates a script used to write the 999 overwhelming majority of documents for the given language and which 1000 therefore adds no distinguishing information to a language tag. It 1001 helps ensure greater compatibility between the language tags 1002 generated according to the rules in this document and language tags 1003 and tag processors or consumers based on RFC 3066. For example, 1004 virtually all Icelandic documents are written in the Latin script, 1005 making the subtag 'Latn' redundant in the tag "is-Latn". 1007 For examples of registry entries and their format, see Appendix C. 1009 3.2 Maintenance of the Registry 1011 Maintenance of the registry requires that as codes are assigned or 1012 withdrawn by ISO 639, ISO 15924, and ISO 3166, the Language Subtag 1013 Reviewer will evaluate each change, determine whether it conflicts 1014 with existing registry entries, and submit the information to IANA 1015 for inclusion in the registry. If an change takes place and the 1016 Language Subtag Reviewer does not do this in a timely manner, then 1017 any interested party may use the procedure in Section 3.4 to register 1018 the appropriate update. 1020 Note: The redundant and grandfathered entries together are the 1021 complete list of tags registered under RFC 3066 [23]. The redundant 1022 tags are those that can now be formed using the subtags defined in 1023 the registry together with the rules of Section 2.2. The 1024 grandfathered entries are those that can never be legal under those 1025 same provisions. 1027 The set of redundant and grandfathered tags is permanent and stable: 1028 no new entries will be added and none of the entries will be removed. 1029 Records of type 'grandfathered' may have their type converted to 1030 'redundant': see Section 3.7 for more information. 1032 RFC 3066 tags that were deprecated prior to the adoption of this 1033 document are part of the list of grandfathered tags and their 1034 component subtags were not included as registered variants (although 1035 they remain eligible for registration). For example, the tag "art- 1036 lojban" was deprecated in favor of the language subtag 'jbo'. 1038 The Language Subtag Reviewer MUST ensure that new subtags meet the 1039 requirements in Section 4.1 or submit an appropriate alternate subtag 1040 as described in that section. If a change or addition to the 1041 registry is required, the Language Subtag Reviewer will prepare the 1042 complete record, including all fields, and forward it to IANA for 1043 insertion into the registry. If this represents a new subtag, then 1044 the message will indicate that this represents an INSERTION of a 1045 record. If this represents a change to an existing subtag, then the 1046 message must indicate that this represents a MODIFICATION, as shown 1047 in the following example: 1049 LANGUAGE SUBTAG MODIFICATION 1050 File-Date: 2005-01-02 1051 %% 1052 Type: variant 1053 Subtag: nedis 1054 Description: Natisone dialect 1055 Description: Nadiza dialect 1056 Added: 2003-10-09 1057 Prefix: sl 1058 Comments: This is a comment shown 1059 as an example. 1060 %% 1062 Figure 5 1064 Whenever an entry is created or modified in the registry, the 'File- 1065 Date' record at the start of the registry is updated to reflect the 1066 most recent modification date in the RFC 3339 [14] "full-date" 1067 format. 1069 Values in the 'Subtag' field must be lowercase except as provided for 1070 in Section 3.1. 1072 3.3 Stability of IANA Registry Entries 1074 The stability of entries and their meaning in the registry is 1075 critical to the long term stability of language tags. The rules in 1076 this section guarantee that a specific language tag's meaning is 1077 stable over time and will not change. 1079 These rules specifically deal with how changes to codes (including 1080 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1081 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1082 Subtag Registry. Assignments to the IANA Language Subtag Registry 1083 MUST follow the following stability rules: 1085 o Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1086 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1087 guaranteed to be stable over time. 1089 o Values in the 'Description' field MUST NOT be changed in a way 1090 that would invalidate previously-existing tags. They may be 1091 broadened somewhat in scope, changed to add information, or 1092 adapted to the most common modern usage. For example, countries 1093 occasionally change their official names: an historical example of 1094 this would be "Upper Volta" changing to "Burkina Faso". 1096 o Values in the field 'Prefix' MAY be added to records of type 1097 'variant' via the registration process. 1099 o Values in the field 'Prefix' MAY be modified, so long as the 1100 modifications broaden the set of recommended prefixes. That is, a 1101 recommended prefix MAY be replaced by one of its own prefixes. 1102 For example, the prefix "en-US" could be replaced by "en", but not 1103 by the ranges "en-Latn", "fr", or "en-US-boont". 1105 o Values in the field 'Prefix' MUST NOT be removed. 1107 o The field 'Comments' MAY be added, changed, modified, or removed 1108 via the registration process or any of the processes or 1109 considerations described in this section. 1111 o The field 'Suppress-Script' MAY be added or removed via the 1112 registration process. 1114 o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1115 conflict with existing subtags of the associated type and whose 1116 meaning is not the same as an existing subtag of the same type are 1117 entered into the IANA registry as new records and their value is 1118 canonical for the meaning assigned to them. 1120 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1121 withdrawn by their respective maintenance or registration 1122 authority remain valid in language tags. A 'Deprecated' field 1123 containing the date of withdrawl is added to the record. If a new 1124 record of the same type is added that represents a replacement 1125 value, then a 'Preferred-Value' field may also be added. The 1126 registration process MAY be used to add comments about the 1127 withdrawal of the code by the respective standard. 1129 * The region code 'TL' was assigned to the country 'Timor-Leste', 1130 replacing the code 'TP' (which was assigned to 'East Timor' 1131 when it was under administration by Portugal). The subtag 'TP' 1132 remains valid in language tags, but its record contains the a 1133 'Preferred-Value' of 'TL' and its field 'Deprecated' contains 1134 the date the new code was assigned ('2004-07-06'). 1136 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1137 with existing subtags of the associated type, including subtags 1138 that are deprecated, MUST NOT be entered into the registry. The 1139 following additional considerations apply: 1141 * For ISO 639 codes, if the newly assigned code's meaning is not 1142 represented by a subtag in the IANA registry, the Language 1143 Subtag Reviewer, as described in Section 3.4, shall prepare a 1144 proposal for entering in the IANA registry as soon as practical 1145 a registered language subtag as an alternate value for the new 1146 code. The form of the registered language subtag will be at 1147 the discretion of the Language Subtag Reviewer and must conform 1148 to other restrictions on language subtags in this document. 1150 * For all subtags whose meaning is derived from an external 1151 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if a 1152 new meaning is assigned to an existing code and the new meaning 1153 broadens the meaning of that code, then the meaning for the 1154 associated subtag MAY be changed to match. The meaning of a 1155 subtag MUST NOT be narrowed, however, as this can result in an 1156 unknown proportion of the existing uses of a subtag becoming 1157 invalid. Note: ISO 639 MA/RA has adopted a similar stability 1158 policy. 1160 * For ISO 15924 codes, if the newly assigned code's meaning is 1161 not represented by a subtag in the IANA registry, the Language 1162 Subtag Reviewer, as described in Section 3.4, shall prepare a 1163 proposal for entering in the IANA registry as soon as practical 1164 a registered variant subtag as an alternate value for the new 1165 code. The form of the registered variant subtag will be at the 1166 discretion of the Language Subtag Reviewer and must conform to 1167 other restrictions on variant subtags in this document. 1169 * For ISO 3166 codes, if the newly assigned code's meaning is 1170 associated with the same UN M.49 code as another 'region' 1171 subtag, then the existing region subtag remains as the 1172 preferred value for that region and no new entry is created. A 1173 comment MAY be added to the existing region subtag indicating 1174 the relationship to the new ISO 3166 code. 1176 * For ISO 3166 codes, if the newly assigned code's meaning is 1177 associated with a UN M.49 code that is not represented by an 1178 existing region subtag, then then the Language Subtag Reviewer, 1179 as described in Section 3.4, shall prepare a proposal for 1180 entering the appropriate numeric UN country code as an entry in 1181 the IANA registry. 1183 * For ISO 3166 codes, if there is no associated UN numeric code, 1184 then the Language Subtag Reviewer SHALL petition the UN to 1185 create one. If there is no response from the UN within ninety 1186 days of the request being sent, the Language Subtag Reviewer 1187 shall prepare a proposal for entering in the IANA registry as 1188 soon as practical a registered variant subtag as an alternate 1189 value for the new code. The form of the registered variant 1190 subtag will be at the discretion of the Language Subtag 1191 Reviewer and must conform to other restrictions on variant 1192 subtags in this document. This situation is very unlikely to 1193 ever occur. 1195 o Stability provisions apply to grandfathered tags with this 1196 exception: should all of the subtags in a grandfathered tag become 1197 valid subtags in the IANA registry, then the field 'Type' in that 1198 record is changed from 'grandfathered' to 'redundant'. Note that 1199 this will not affect language tags that match the grandfathered 1200 tag, since these tags will now match valid generative subtag 1201 sequences. For example, if the subtag 'gan' in the language tag 1202 "zh-gan" were to be registered as an extended language subtag, 1203 then the grandfathered tag "zh-gan" would be deprecated (but 1204 existing content or implementations that use "zh-gan" would remain 1205 valid). 1207 3.4 Registration Procedure for Subtags 1209 The procedure given here MUST be used by anyone who wants to use a 1210 subtag not currently in the IANA Language Subtag Registry. 1212 Only subtags of type 'language' and 'variant' will be considered for 1213 independent registration of new subtags. Handling of subtags 1214 required for stability and subtags required to keep the registry 1215 synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within 1216 the limits defined by this document are described in Section 3.2. 1217 Stability provisions are described in Section 3.3. 1219 This procedure MAY also be used to register or alter the information 1220 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1221 in a subtag's record as described in Figure 8. Changes to all other 1222 fields in the IANA registry are NOT permitted. 1224 Registering a new subtag or requesting modifications to an existing 1225 tag or subtag starts with the requster filling out the registration 1226 form reproduced below. Note that each response is not limited in 1227 size and should take the room necessary to adequately describe the 1228 registration. The fields in the "Record Requested" section SHOULD 1229 follow the requirements in Section 3.1. 1231 LANGUAGE SUBTAG REGISTRATION FORM 1232 1. Name of requester: 1233 2. E-mail address of requester: 1234 3. Record Requested: 1236 Type: 1237 Subtag: 1238 Description: 1239 Prefix: 1240 Preferred-Value: 1241 Deprecated: 1242 Suppress-Script: 1243 Comments: 1245 4. Intended meaning of the subtag: 1246 5. Reference to published description 1247 of the language (book or article): 1248 6. Any other relevant information: 1250 Figure 6 1252 The subtag registration form MUST be sent to 1253 for a two week review period before it can 1254 be submitted to IANA. (This is an open list. Requests to be added 1255 should be sent to .) 1257 Variant and extlang subtags are always registered for use with a 1258 particular range of language tags. For example, the subtag 'scouse' 1259 is intended for use with language tags that start with the primary 1260 language subtag "en", since Scouse is a dialect of English. Thus the 1261 subtag 'scouse' could be included in tags such as "en-Latn-scouse" or 1262 "en-GB-scouse". This information is stored in the "Prefix" field in 1263 the registry. Variant registration requests are REQUIRED to include 1264 at least one "Prefix" field in the registration form. 1266 The 'Prefix' field for a given registered subtag will be maintained 1267 in the IANA registry as a guide to usage. Additional prefixes MAY be 1268 added by filing an additional registration form. In that form, the 1269 "Any other relevant information:" field should indicate that it is 1270 the addition of a prefix. 1272 Requests to add a prefix to a variant subtag that imply a different 1273 semantic meaning will probably be rejected. For example, a request 1274 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1275 nedis" represented some German dialect would be rejected. The 1276 'nedis' subtag represents a particular Slovenian dialect and the 1277 additional registration would change the semantic meaning assigned to 1278 the subtag. A separate subtag should be proposed instead. 1280 The 'Description' field must contain a description of the tag being 1281 registered written or transcribed into the Latin script; it may also 1282 include a description in a non-Latin script. Non-ASCII characters 1283 must be escaped using the syntax described in Section 3.1. The 1284 'Description' field is used for identification purposes and should 1285 not be taken to represent the actual native name of the language or 1286 variation or to be in any particular language. 1288 While the 'Description' field itself is not guaranteed to be stable 1289 and errata corrections may be undertaken from time to time, attempts 1290 to provide translations or transcriptions of entries in the registry 1291 itself will probably be frowned upon by the community or rejected 1292 outright, as changes of this nature may impact the provisions in 1293 Section 3.3. 1295 The Language Subtag Reviewer is responsible for responding to 1296 requests for the registration of subtags through the registration 1297 process and is appointed by the IESG. 1299 When the two week period has passed the Language Subtag Reviewer 1300 either forwards the record to be inserted or modified to 1301 iana@iana.org according to the procedure described in Section 3.2, or 1302 rejects the request because of significant objections raised on the 1303 list or due to problems with constraints in this document (which 1304 should be explicitly cited). The reviewer may also extend the review 1305 period in two week increments to permit further discussion. The 1306 reviewer must indicate on the list whether the registration has been 1307 accepted, rejected, or extended following each two week period. 1309 Note that the reviewer can raise objections on the list if he or she 1310 so desires. The important thing is that the objection must be made 1311 publicly. 1313 The applicant is free to modify a rejected application with 1314 additional information and submit it again; this restarts the two 1315 week comment period. 1317 Decisions made by the reviewer may be appealed to the IESG [RFC 2028] 1318 [9] under the same rules as other IETF decisions [RFC 2026] [8]. 1320 All approved registration forms are available online in the directory 1321 http://www.iana.org/numbers.html under "languages". 1323 Updates or changes to existing records, including previous 1324 registrations, follow the same procedure as new registrations. The 1325 Language Subtag Reviewer decides whether there is consensus to update 1326 the registration following the two week review period; normally 1327 objections by the original registrant will carry extra weight in 1328 forming such a consensus. 1330 Registrations are permanent and stable. Once registered, subtags 1331 will not be removed from the registry and will remain a valid way in 1332 which to specify a specific language or variant. 1334 Note: The purpose of the "Description" in the registration form is 1335 intended as an aid to people trying to verify whether a language is 1336 registered or what language or language variation a particular subtag 1337 refers to. In most cases, reference to an authoritative grammar or 1338 dictionary of that language will be useful; in cases where no such 1339 work exists, other well known works describing that language or in 1340 that language may be appropriate. The subtag reviewer decides what 1341 constitutes "good enough" reference material. This requirement is 1342 not intended to exclude particular languages or dialects due to the 1343 size of the speaker population or lack of a standardized orthography. 1344 Minority languages will be considered equally on their own merits. 1346 3.5 Possibilities for Registration 1348 Possibilities for registration of subtags or information about 1349 subtags include: 1351 o Primary language subtags for languages not listed in ISO 639 that 1352 are not variants of any listed or registered language can be 1353 registered. At the time this document was created there were no 1354 examples of this form of subtag. Before attempting to register a 1355 language subtag, there MUST be an attempt to register the language 1356 with ISO 639. No language subtags will be registered for codes 1357 that exist in ISO 639-1 or ISO 639-2, which are under 1358 consideration by the ISO 639 maintenance or registration 1359 authorities, or which have never been attempted for registration 1360 with those authorities. If ISO 639 has previously rejected a 1361 language for registration, it is reasonable to assume that there 1362 must be additional very compelling evidence of need before it will 1363 be registered in the IANA registry (to the extent that it is very 1364 unlikely that any subtags will be registered of this type). 1366 o Dialect or other divisions or variations within a language, its 1367 orthography, writing system, regional or historical usage, 1368 transliteration or other transformation, or distinguishing 1369 variation may be registered as variant subtags. An example is the 1370 'scouse' subtag (the Scouse dialect of English). 1372 o The addition or maintenance of fields (generally of an 1373 informational nature) in Tag or Subtag records as described in 1374 Section 3.1 and subject to the stability provisions in 1375 Section 3.3. This includes descriptions; comments; deprecation 1376 and preferred values for obsolete or withdrawn codes; or the 1377 addition of script or extlang information to primary language 1378 subtags. 1380 This document leaves the decision on what subtags or changes to 1381 subtags are appropriate (or not) to the registration process 1382 described in Section 3.4. 1384 Note: four character primary language subtags are reserved to allow 1385 for the possibility of alpha4 codes in some future addition to the 1386 ISO 639 family of standards. 1388 ISO 639 defines a maintenance agency for additions to and changes in 1389 the list of languages in ISO 639. This agency is: 1391 International Information Centre for Terminology (Infoterm) 1392 Aichholzgasse 6/12, AT-1120 1393 Wien, Austria 1394 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1396 ISO 639-2 defines a maintenance agency for additions to and changes 1397 in the list of languages in ISO 639-2. This agency is: 1399 Library of Congress 1400 Network Development and MARC Standards Office 1401 Washington, D.C. 20540 USA 1402 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1403 URL: http://www.loc.gov/standards/iso639 1405 The maintenance agency for ISO 3166 (country codes) is: 1407 ISO 3166 Maintenance Agency 1408 c/o International Organization for Standardization 1409 Case postale 56 1410 CH-1211 Geneva 20 Switzerland 1411 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1412 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1414 The registration authority for ISO 15924 (script codes) is: 1416 Unicode Consortium Box 391476 1417 Mountain View, CA 94039-1476, USA 1418 URL: http://www.unicode.org/iso15924 1420 The Statistics Division of the United Nations Secretariat maintains 1421 the Standard Country or Area Codes for Statistical Use and can be 1422 reached at: 1424 Statistical Services Branch 1425 Statistics Division 1426 United Nations, Room DC2-1620 1427 New York, NY 10017, USA 1429 Fax: +1-212-963-0623 1430 E-mail: statistics@un.org 1431 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1433 3.6 Extensions and Extensions Namespace 1435 Extension subtags are those introduced by single-letter subtags other 1436 than 'x'. They are reserved for the generation of identifiers which 1437 contain a language component, and are compatible with applications 1438 that understand language tags. For example, they might be used to 1439 define locale identifiers, which are generally based on language. 1441 The structure and form of extensions are defined by this document so 1442 that implementations can be created that are forward compatible with 1443 applications that may be created using single-letter subtags in the 1444 future. In addition, defining a mechanism for maintaining single- 1445 letter subtags will lend to the stability of this document by 1446 reducing the likely need for future revisions or updates. 1448 Allocation of a single-letter subtag shall take the form of an RFC 1449 defining the name, purpose, processes, and procedures for maintaining 1450 the subtags. The maintaining or registering authority, including 1451 name, contact email, discussion list email, and URL location of the 1452 registry must be indicated clearly in the RFC. The RFC MUST specify 1453 or include each of the following: 1455 o The specification MUST reference the specific version or revision 1456 of this document that governs its creation and MUST reference this 1457 section of this document. 1459 o The specification and all subtags defined by the specification 1460 MUST follow the ABNF and other rules for the formation of tags and 1461 subtags as defined in this document. In particular it MUST 1462 specify that case is not significant and that subtags MUST NOT 1463 exceed eight characters in length. 1465 o The specification MUST specify a canonical representation. 1467 o The specification of valid subtags MUST be available over the 1468 Internet and at no cost. 1470 o The specification MUST be in the public domain or available via a 1471 royalty-free license acceptable to the IETF and specified in the 1472 RFC. 1474 o The specification MUST be versioned and each version of the 1475 specification MUST be numbered, dated, and stable. 1477 o The specification MUST be stable. That is, extension subtags, 1478 once defined by a specification, MUST NOT be retracted or change 1479 in meaning in any substantial way. 1481 o The specification MUST include in a separate section the 1482 registration form reproduced in this section (below) to be used in 1483 registering the extension upon publication as an RFC. 1485 o IANA MUST be informed of changes to the contact information and 1486 URL for the specification. 1488 o Modified the latin-script requirement on the 'Description' field 1489 so that "at least one Description field" must contain a Latin 1490 transcription. (A.Phillips) 1492 IANA will maintain a registry of allocated single-letter (singleton) 1493 subtags. This registry will use the record-jar format described by 1494 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1495 the maintaining authority defined in the RFC must forward this 1496 registration form to iesg@ietf.org, who will forward the request to 1497 iana@iana.org. The maintaining authority of the extension MUST 1498 maintain the accuracy of the record by sending an updated full copy 1499 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1500 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1501 'Contact_Email', 'Mailing_List', and 'URL' fields may be modified in 1502 these updates. 1504 Failure to maintain this record, the corresponding registry, or meet 1505 other conditions imposed by this section of this document may be 1506 appealed to the IESG [RFC 2028] [9] under the same rules as other 1507 IETF decisions (see [8]) and may result in the authority to maintain 1508 the extension being withdrawn or reassigned by the IESG. 1509 %% 1510 Identifier: 1511 Description: 1512 Comments: 1513 Added: 1514 RFC: 1515 Authority: 1516 Contact_Email: 1517 Mailing_List: 1518 URL: 1519 %% 1521 Figure 7: Format of Records in the Language Tag Extensions Registry 1523 'Identifier' contains the single letter subtag (singleton) assigned 1524 to the extension. The Internet-Draft submitted to define the 1525 extension should specific which letter to use, although the IESG may 1526 change the assignment when approving the RFC. 1528 'Description' contains the name and description of the extension. 1530 'Comments' is an optional field and may contain a broader description 1531 of the extension. 1533 'Added' contains the date the RFC was published in the "full-date" 1534 format specified in RFC 3339 [14]. For example: 2004-06-28 1535 represents June 28, 2004, in the Gregorian calendar. 1537 'RFC' contains the RFC number assigned to the extension. 1539 'Authority' contains the name of the maintaining authority for the 1540 extension. 1542 'Contact_Email' contains the email address used to contact the 1543 maintaining authority. 1545 'Mailing_List' contains the URL or subscription email address of the 1546 mailing list used by the maintaining authority. 1548 'URL' contains the URL of the registry for this extension. 1550 The determination of whether an Internet-Draft meets the above 1551 conditions and the decision to grant or withhold such authority rests 1552 solely with the IESG, and is subject to the normal review and appeals 1553 process associated with the RFC process. 1555 Extension authors are strongly cautioned that many (including most 1556 well-formed) processors will be unaware of any special relationships 1557 or meaning inherent in the order of extension subtags. Extension 1558 authors SHOULD avoid subtag relationships or canonicalization 1559 mechanisms that interfere with matching or with length restrictions 1560 that may exist in common protocols where the extension is used. In 1561 particular, applications may truncate the subtags in doing matching 1562 or in fitting into limited lengths, so it is RECOMMENDED that the 1563 most significant information be in the most significant (left-most) 1564 subtags, and that the specification gracefully handle truncated 1565 subtags. 1567 When a language tag is to be used in a specific, known, protocol, it 1568 is RECOMMENDED that that the language tag not contain extensions not 1569 supported by that protocol. In addition, it should be noted that 1570 some protocols may impose upper limits on the length of the strings 1571 used to store or transport the language tag. 1573 3.7 Initialization of the Registry 1575 Upon publication of this document as a BCP, the Language Subtag 1576 Registry must be created and populated with the initial set of 1577 subtags. This includes converting the entries from the existing IANA 1578 language tag registry defined by RFC 3066 to the new format. This 1579 section defines the process for defining the new registry and 1580 performing the conversion of the old registry. 1582 The impact on the IANA maintainers of the registry of this conversion 1583 will be a small increase in the frequency of new entries. The 1584 initial set of records represents no impact on IANA, since the work 1585 to create it will be performed externally (as defined in this 1586 section). Future work will be limited to inserting or replacing 1587 whole records preformatted for IANA by the Language Subtag Reviewer. 1589 The initial registry will be created by the LTRU working group. 1590 Using the instructions in this document, the working group will 1591 prepare an Informational RFC by creating a series of Internet-Drafts 1592 containing the prototype registry according to the rules in Sections 1593 4.2.2 and 4.2.3 and subject to IESG review as described in Section 1594 6.1.1 of RFC 2026 [8]. 1596 When the Internet-Draft containing the prototype registry has been 1597 approved by the IESG for publication as an RFC, the document will be 1598 forwarded to IANA, which will post the contents of the new registry 1599 on-line. 1601 Tags in the RFC 3066 registry that are not deprecated that consist 1602 entirely of subtags that are valid under this document and which have 1603 the correct form and format for tags defined by this document are 1604 superseded by this document. Such tags are placed in records of type 1605 'redundant' in the registry. For example, "zh-Hant" is now defined 1606 by this document. 1608 All other tags in the RFC 3066 registry that are deprecated will be 1609 maintained as grandfathered entries. The record for the 1610 grandfathered entry will contain a 'Deprecated' field with the most 1611 appropriate date that can be determined for when the record was 1612 deprecated. The 'Comments' field will contain the reason for the 1613 deprecation. The 'Preferred-Value' field will contain the tag that 1614 replaces the value. For example, the tag "art-lojban" is deprecated 1615 and will be placed in the grandfathered section. It's 'Deprecated' 1616 field will contain the deprecation date (in this case "2003-09-02") 1617 and the 'Preferred-Value' field the value "jbo". 1619 Tags that are not deprecated and which contain subtags which are 1620 consistent with registration under the guidelines in this document 1621 will not automatically have a new subtag registration created for 1622 each eligible subtag. Interrested parties may use the registration 1623 process in Section 3.4 to register these subtags. If all of the 1624 subtags in the original tag become fully defined by the resulting 1625 registrations, then the original tag is superseded by this document. 1626 Such tags will have their record changed from type 'grandfathered' to 1627 type 'redundant' in the registry. For example, the subtag 'boont' 1628 could be registered, resulting in the change of the grandfathered tag 1629 "en-boont" to type redundant in the registry. 1631 Tags that contain one or more subtags that do not match the valid 1632 registration pattern and which are not otherwise defined by this 1633 document will have records of type 'grandfathered' created in the 1634 registry. These records cannot become type 'redundant', but may have 1635 a 'Deprecated' and 'Prefered-Value' field added to them if a subtag 1636 assignment or combination of assignments renders the tag obsolete. 1638 There will be a reasonable period in which the community may comment 1639 on the proposed list entries, which SHALL be no less than four weeks 1640 in length. At the completion of this period, the chair(s) will 1641 notify iana@iana.org and the ltru and ietf-languages mail lists that 1642 the task is complete and forward the necessary materials to IANA for 1643 publication. 1645 Registrations that are in process under the rules defined in RFC 3066 1646 MAY be completed under the former rules, at the discretion of the 1647 language tag reviewer. Any new registrations submitted after the 1648 request for conversion of the registry MUST be rejected. 1650 All existing RFC 3066 language tag registrations will be maintained 1651 in perpetuity. 1653 Users of tags that are grandfathered should consider registering 1654 appropriate subtags in the IANA subtag registry (but are not required 1655 to). 1657 UN numeric codes assigned to 'macro-geographical (continental)' or 1658 sub-regions not associated with an assigned ISO 3166 alpha-2 code are 1659 defined in the IANA registry and are valid for use in language tags. 1660 These codes MUST be added to the initial version of the registry. 1661 The UN numeric codes for 'economic groupings' or 'other groupings', 1662 and the alphanumeric codes in Appendix X of the UN document MUST NOT 1663 be added to the registry. 1665 When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49 1666 codes, the following criteria SHALL be applied to the inclusion, 1667 preferred value, and deprecation of codes: 1669 For each standard, the date of the standard referenced in RFC 1766 is 1670 selected as the starting date. Codes that were valid on that date in 1671 the selected standard are added to the registry. Codes that were 1672 previously assigned by but which were vacated or withdrawn before 1673 that date are not added to the registry. For each successive change 1674 to the standard, any additional assignments are added to the 1675 registry. Values that are withdrawn are marked as deprecated, but 1676 not removed. Changes in meaning or assignment of a subtag are 1677 permitted during this process (for example, the ISO 3166 code 'CS' 1678 was originally assigned to 'Czechoslovakia' and is now assigned to 1679 'Serbia and Montenegro'). This continues up to the date that this 1680 document was adopted. The resulting set of records is added to the 1681 registry. Future changes or additions to this portion of the 1682 registry are governed by the provisions of this document. 1684 4. Formation and Processing of Language Tags 1686 This section addresses how to use the registry with the language tag 1687 format to choose, form and process language tags. 1689 4.1 Choice of Language Tag 1691 One may occasionally be faced with several possible tags for the same 1692 body of text. 1694 Interoperability is best served when all users use the same language 1695 tag in order to represent the same language. If an application has 1696 requirements that make the rules here inapplicable, then that 1697 application risks damaging interoperability. It is strongly 1698 RECOMMENDED that users not define their own rules for language tag 1699 choice. 1701 Of particular note, many applications can benefit from the use of 1702 script subtags in language tags, as long as the use is consistent for 1703 a given context. Script subtags were not formally defined in RFC 1704 3066 and their use may affect matching and subtag identification by 1705 implementations of RFC 3066, as these subtags appear between the 1706 primary language and region subtags. For example, if a user requests 1707 content in an implementation of Section 2.5 of RFC 3066 [23] using 1708 the language range "en-US", content labeled "en-Latn-US" will not 1709 match the request. Therefore it is important to know when script 1710 subtags will customarily be used and when they should not be used. 1711 In the registry, the Suppress-Script field helps ensure greater 1712 compatibility between the language tags generated according to the 1713 rules in this document and language tags and tag processors or 1714 consumers based on RFC 3066 by defining when users should generally 1715 not include a script subtag with a particular primary language 1716 subtag. 1718 Extended language subtags (type 'extlang' in the registry, see 1719 Section 3.1) also appear between the primary language and region 1720 subtags and are reserved for future standardization. Applications 1721 may benefit from their judicious use in forming language tags in the 1722 future and similar recommendations are expected to apply to their use 1723 as apply to script subtags. 1725 Standards, protocols and applications that reference this document 1726 normatively but apply different rules to the ones given in this 1727 section MUST specify how the procedure varies from the one given 1728 here. 1730 The choice of subtags used to form a language tag should be guided by 1731 the following rules: 1733 1. Use as precise a tag as possible, but no more specific than is 1734 justified. Avoid using subtags that are not important for 1735 distinguishing content in an application. 1737 * For example, 'de' might suffice for tagging an email written 1738 in German, while "de-CH-1996" is probably unnecessarily 1739 precise for such a task. 1741 2. The script subtag SHOULD NOT be used to form language tags unless 1742 the script adds some distinguishing information to the tag. The 1743 field 'Suppress-Script' in the primary language record in the 1744 registry indicates which script subtags do not add distinguishing 1745 information for most applications. 1747 * For example, the subtag 'Latn' should not be used with the 1748 primary language 'en' because nearly all English documents are 1749 written in the Latin script and it adds no distinguishing 1750 information. However, if a document were written in English 1751 mixing Latin script with another script such as Braille 1752 ('Brai'), then it may be appropriate to choose to indicate 1753 both scripts to aid in content selection, such as the 1754 application of a stylesheet. 1756 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1757 entry, then the value of that field SHOULD be used to form the 1758 language tag in preference to the tag or subtag in which the 1759 preferred value appears. 1761 * For example, use 'he' for Hebrew in preference to 'iw'. 1763 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1764 used to label content, even if the language is unknown. Omitting 1765 the language tag altogether is preferred to using a tag with a 1766 primary language subtag of 'und'. The 'und' subtag may be useful 1767 for protocols that require a language tag to be provided. The 1768 'und' subtag may also be useful when matching language tags in 1769 certain situations. 1771 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1772 whenever the protocol allows the separate tags for multiple 1773 languages, as is the case for the Content-Language header in 1774 HTTP. The 'mul' subtag conveys little useful information: 1775 content in multiple languages should individually tag the 1776 languages where they appear or otherwise indicate the actual 1777 language in preference to the 'mul' subtag. 1779 6. The same variant subtag SHOULD NOT be used more than once within 1780 a language tag. 1782 * For example, do not use "en-GB-scouse-scouse". 1784 To ensure consistent backward compatibility, this document contains 1785 several provisions to account for potential instability in the 1786 standards used to define the subtags that make up language tags. 1787 These provisions mean that no language tag created under the rules in 1788 this document will become obsolete. 1790 4.2 Meaning of the Language Tag 1792 The language tag always defines a language as spoken (or written, 1793 signed or otherwise signaled) by human beings for communication of 1794 information to other human beings. Computer languages such as 1795 programming languages are explicitly excluded. 1797 If a language tag B contains language tag A as a prefix, then B is 1798 typically "narrower" or "more specific" than A. For example, "zh- 1799 Hant-TW" is more specific than "zh-Hant". 1801 This relationship is not guaranteed in all cases: specifically, 1802 languages that begin with the same sequence of subtags are NOT 1803 guaranteed to be mutually intelligible, although they may be. For 1804 example, the tag "az" shares a prefix with both "az-Latn" 1805 (Azerbaijani written using the Latin script) and "az-Cyrl" 1806 (Azerbaijani written using the Cyrillic script). A person fluent in 1807 one script may not be able to read the other, even though the text 1808 might be identical. Content tagged as "az" most probably is written 1809 in just one script and thus might not be intelligible to a reader 1810 familiar with the other script. 1812 The relationship between the tag and the information it relates to is 1813 defined by the standard describing the context in which it appears. 1814 Accordingly, this section can only give possible examples of its 1815 usage. 1817 o For a single information object, the associated language tags 1818 might be interpreted as the set of languages that is required for 1819 a complete comprehension of the complete object. Example: Plain 1820 text documents. 1822 o For an aggregation of information objects, the associated language 1823 tags could be taken as the set of languages used inside components 1824 of that aggregation. Examples: Document stores and libraries. 1826 o For information objects whose purpose is to provide alternatives, 1827 the associated language tags could be regarded as a hint that the 1828 content is provided in several languages, and that one has to 1829 inspect each of the alternatives in order to find its language or 1830 languages. In this case, the presence of multiple tags might not 1831 mean that one needs to be multi-lingual to get complete 1832 understanding of the document. Example: MIME multipart/ 1833 alternative. 1835 o In markup languages, such as HTML and XML, language information 1836 can be added to each part of the document identified by the markup 1837 structure (including the whole document itself). For example, one 1838 could write C'est la vie. inside a 1839 Norwegian document; the Norwegian-speaking user could then access 1840 a French-Norwegian dictionary to find out what the marked section 1841 meant. If the user were listening to that document through a 1842 speech synthesis interface, this formation could be used to signal 1843 the synthesizer to appropriately apply French text-to-speech 1844 pronunciation rules to that span of text, instead of applying the 1845 inappropriate Norwegian rules. 1847 4.3 Canonicalization of Language Tags 1849 Since a particular language tag may be used in many processes, 1850 language tags SHOULD always be created or generated in a canonical 1851 form. 1853 A language tag is in canonical form when: 1855 1. The tag is well-formed according the rules in Section 2.1 and 1856 Section 2.2. 1858 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1859 the IANA registry (see Section 3.1) SHOULD be replaced with their 1860 mapped value. 1862 3. Redundant or grandfathered tags that have a Preferred-Value 1863 mapping in the IANA registry (see Section 3.1) MUST be replaced 1864 with their mapped value. These items are either deprecated 1865 mappings created before the adoption of this document (such as 1866 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1867 the result of later registrations or additions to this document 1868 (for example, "zh-guoyu" might be mapped to a language-extlang 1869 combination such as "zh-cmn" by some future update of this 1870 document). 1872 4. Other subtags that have a Preferred-Value mapping in the IANA 1873 registry (see Section 3.1) MUST be replaced with their mapped 1874 value. These items consist entirely of clerical corrections to 1875 ISO 639-1 in which the deprecated subtags have been maintained 1876 for compatibility purposes. 1878 5. If more than one extension subtag sequence exists, the extension 1879 sequences are ordered into case-insensitive ASCII order by 1880 singleton subtag. 1882 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1883 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1884 canonical form. 1886 Example: The language tag "en-NH" (English as used in the New 1887 Hebrides) is not canonical because the 'NH' subtag has a canonical 1888 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1889 validity. 1891 Canonicalization of language tags does not imply anything about the 1892 use of upper or lowercase letters when processing or comparing 1893 subtags (and as described in Section 2.1). All comparisons MUST be 1894 performed in a case-insensitive manner. 1896 When performing canonicalization of language tags, processors MAY 1897 optionally regularize the case of the subtags, following the case 1898 used in the registry. Note that this corresponds to the following 1899 casing rules: uppercase all non-initial two-letter subtags; titlecase 1900 all non-initial four-letter subtags; lowercase everything else. 1902 Note: Case folding of ASCII letters in certain locales, unless 1903 carefully handled, may produce non-ASCII character values. The 1904 Unicode Character Database file "SpecialCasing.txt" defines the 1905 specific cases that are known to cause problems with this. In 1906 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1907 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1908 Implementers should specify a locale-neutral casing operation to 1909 ensure that case folding of subtags does not produce this value, 1910 which is illegal in language tags. For example, if one were to 1911 uppercase the region subtag 'in' using Turkish locale rules, the 1912 sequence U+0130 U+004E would result instead of the expected 'IN'. 1914 Note: if the field 'Deprecated' appears in a registry record without 1915 an accompanying 'Preferred-Value' field, then that tag or subtag is 1916 deprecated without a replacement. Validating processors SHOULD NOT 1917 generate tags that include these values, although the values are 1918 canonical when they appear in a language tag. 1920 An extension MUST define any relationships that may exist between the 1921 various subtags in the extension and thus MAY define an alternate 1922 canonicalization scheme for the extension's subtags. Extensions MAY 1923 define how the order of the extension's subtags are interpreted. For 1924 example, an extension could define that its subtags are in canonical 1925 order when the subtags are placed into ASCII order: that is, "en-a- 1926 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1927 define that the order of the subtags influences their semantic 1928 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1929 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1930 so that they are tolerant of the typical processes described in 1931 Section 3.6. 1933 4.4 Considerations for Private Use Subtags 1935 Private-use subtags require private agreement between the parties 1936 that intend to use or exchange language tags that use them and great 1937 caution should be used in employing them in content or protocols 1938 intended for general use. Private-use subtags are simply useless for 1939 information exchange without prior arrangement. 1941 The value and semantic meaning of private-use tags and of the subtags 1942 used within such a language tag are not defined by this document. 1944 The use of subtags defined in the IANA registry as having a specific 1945 private use meaning convey more information that a purely private use 1946 tag prefixed by the singleton subtag 'x'. For applications this 1947 additional information may be useful. 1949 For example, the region subtags 'AA', 'ZZ' and in the ranges 1950 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) may 1951 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 1952 great deal of public, interchangeable information about the language 1953 material (that it is Chinese in the simplified Chinese script and is 1954 suitable for some geographic region 'XQ'). While the precise 1955 geographic region is not known outside of private agreement, the tag 1956 conveys far more information than an opaque tag such as "x-someLang", 1957 which contains no information about the language subtag or script 1958 subtag outside of the private agreement. 1960 However, in some cases content tagged with private use subtags may 1961 interact with other systems in a different and possibly unsuitable 1962 manner compared to tags that use opaque, privately defined subtags, 1963 so the choice of the best approach may depend on the particular 1964 domain in question. 1966 5. IANA Considerations 1968 This section deals with the processes and requirements necessary for 1969 IANA to undertake to maintain the rsubtag and extension registries as 1970 defined by this document and in accordance with the requirements of 1971 RFC 2434 [11]. 1973 The impact on the IANA maintainers of the two registries defined by 1974 this document will be a small increase in the frequency of new 1975 entries or updates. 1977 Upon adoption of this document, the process described in Section 3.7 1978 will be used to generate the initial Language Subtag Registry. The 1979 initial set of records represents no impact on IANA, since the work 1980 to create it will be performed externally (as defined in that 1981 section). The new registry will be listed under "Language Tags" at 1982 . The existing directory of 1983 registration forms and RFC 3066 registrations will be relabeled as 1984 "Language Tags (Obsolete)" and maintained (but not added to or 1985 modified). 1987 Future work on the Language Subtag Registry will be limited to 1988 inserting or replacing whole records preformatted for IANA by the 1989 Language Subtag Reviewer as described in Section 3.2 of this 1990 document. Each record will be sent to iana@iana.org with a subject 1991 line indicating whether the enclosed record is an insertion (of a new 1992 record) or a replacment of an existing record which has a Type and 1993 Subtag (or Tag) field that exactly matches the record sent. Records 1994 cannot be deleted from the registry. 1996 The Language Tag Extensions registry will also be generated and sent 1997 to IANA as described in Section 3.6. This registry may contain at 1998 most 35 records and thus changes to this registry are expected to be 1999 very infrequent. 2001 Future work by IANA on the Language Tag Extensions Registry is 2002 limited to two cases. First, the IESG may request that new records 2003 be inserted into this registry from time to time. These requests 2004 will include the record to insert in the exact format described in 2005 Section 3.6. In addition, there may be occasional requests from the 2006 maintaining authority for a specific extension to update the contact 2007 information or URLs in the record. These requests MUST include the 2008 complete, updated record. IANA is not responsible for validating the 2009 information provided, only that it is properly formatted. It should 2010 reasonably be seen to come from the maintaining authority named in 2011 the record present in the registry. 2013 6. Security Considerations 2015 Language tags used in content negotiation, like any other information 2016 exchanged on the Internet, may be a source of concern because they 2017 may be used to infer the nationality of the sender, and thus identify 2018 potential targets for surveillance. 2020 This is a special case of the general problem that anything sent is 2021 visible to the receiving party and possibly to third parties as well. 2022 It is useful to be aware that such concerns can exist in some cases. 2024 The evaluation of the exact magnitude of the threat, and any possible 2025 countermeasures, is left to each application protocol (see BCP 72, 2026 RFC 3552 [15] for best current practice guidance on security threats 2027 and defenses). 2029 Since there is no limit to the number of variant, private use, and 2030 extension subtags, and consequently no limit on the possible length 2031 of a tag, implementations need to guard against buffer overflow 2032 attacks. See section Section 2.1.1 for details on language tag 2033 truncation, which can occur as a consequence of defenses against 2034 buffer overflow. 2036 Although the specification of valid subtags for an extension (see: 2037 Section 3.6) MUST be available over the Internet, implementations 2038 SHOULD NOT mechanically depend on it being always accessible, to 2039 prevent denial-of-service attacks. 2041 7. Character Set Considerations 2043 The syntax in this document requires that language tags use only the 2044 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2045 character sets, so the composition of language tags should not have 2046 any character set issues. 2048 Rendering of characters based on the content of a language tag is not 2049 addressed in this memo. Historically, some languages have relied on 2050 the use of specific character sets or other information in order to 2051 infer how a specific character should be rendered (notably this 2052 applies to language and culture specific variations of Han ideographs 2053 as used in Japanese, Chinese, and Korean). When language tags are 2054 applied to spans of text, rendering engines may use that information 2055 in deciding which font to use in the absence of other information, 2056 particularly where languages with distinct writing traditions use the 2057 same characters. 2059 8. Changes from RFC 3066 2061 The main goals for this revision of language tags were the following: 2063 *Compatibility.* All valid RFC 3066 language tags (including those 2064 in the IANA registry) remain valid in this specification. Thus 2065 there is complete backward compatibility of this specification with 2066 existing content. In addition, this document defines language tags 2067 in such as way as to ensure future compatibility, and processors 2068 based solely on the RFC 3066 ABNF (such as those described in XML 2069 Schema version 1.0 [19]) will be able to process tags described by 2070 this document. 2072 *Stability.* Because of the changes in underlying ISO standards, a 2073 valid RFC 3066 language tag may become invalid (or have its meaning 2074 change) at a later date. With so much of the world's computing 2075 infrastructure dependent on language tags, this is simply 2076 unacceptable: it invalidates content that may have an extensive 2077 shelf-life. In this specification, once a language tag is valid, it 2078 remains valid forever. Previously, there was no way to determine 2079 when two tags were equivalent. This specification provides a stable 2080 mechanism for doing so, through the use of canonical forms. These 2081 are also stable, so that implementations can depend on the use of 2082 canonical forms to assess equivalency. 2084 *Validity.* The structure of language tags defined by this document 2085 makes it possible to determine if a particular tag is well-formed 2086 without regard for the actual content or "meaning" of the tag as a 2087 whole. This is important because the registry and underlying 2088 standards change over time. In addition, it must be possible to 2089 determine if a tag is valid (or not) for a given point in time in 2090 order to provide reproducible, testable results. This process must 2091 not be error-prone; otherwise even intelligent people will generate 2092 implementations that give different results. This specification 2093 provides for that by having a single data file, with specific 2094 versioning information, so that the validity of language tags at any 2095 point in time can be precisely determined (instead of interpolating 2096 values from many separate sources). 2098 *Extensibility.* It is important to be able to differentiate between 2099 written forms of language -- for many implementations this is more 2100 important than distinguishing between spoken variants of a language. 2101 Languages are written in a wide variety of different scripts, so this 2102 document provides for the generative use of ISO 15924 script codes. 2103 Like the generative use of ISO language and country codes in RFC 2104 3066, this allows combinations to be produced without resorting to 2105 the registration process. The addition of UN codes provides for the 2106 generation of language tags with regional scope, which is also 2107 required for information technology. 2109 The recast of the registry from containing whole language tags to 2110 subtags is a key part of this. An important feature of RFC 3066 was 2111 that it allowed generative use of subtags. This allows people to 2112 meaningfully use generated tags, without the delays in registering 2113 whole tags, and the burden on the registry of having to supply all of 2114 the combinations that people may find useful. 2116 Because of the widespread use of language tags, it is potentially 2117 disruptive to have periodic revisions of the core specification, 2118 despite demonstrated need. The extension mechanism provides for a 2119 way for independent RFCs to define extensions to language tags. 2120 These extensions have a very constrained, well-defined structure to 2121 prevent extensions from interfering with implementations of language 2122 tags defined in this document. The document also anticipates 2123 features of ISO 639-3 with the addition of the extended language 2124 subtags, as well as the possibility of other ISO 639 parts becoming 2125 useful for the formation of language tags in the future. The use and 2126 definition of private use tags has also been modified, to allow 2127 people to move as much information as possible out of private use 2128 tags, and into the regular structure. The goal is to dramatically 2129 reduce the need to produce a revision of this document in the future. 2131 The specific changes in this document to meet these goals are: 2133 o Defines the ABNF and rules for subtags so that the category of all 2134 subtags can be determined without reference to the registry. 2136 o Adds the concept of well-formed vs. validating processors, 2137 defining the rules by which an implementation can claim to be one 2138 or the other. 2140 o Replaces the IANA language tag registry with a language subtag 2141 registry that provides a complete list of valid subtags in the 2142 IANA registry. This allows for robust implementation and ease of 2143 maintenance. The language subtag registry becomes the canonical 2144 source for forming language tags. 2146 o Provides a process that guarantees stability of language tags, by 2147 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2148 the event that they register a previously used value for a new 2149 purpose. 2151 o Allows ISO 15924 script code subtags and allows them to be used 2152 generatively. Defines a method for indicating in the registry 2153 when script subtags are necessary for a given language tag. 2155 o Adds the concept of a variant subtag and allows variants to be 2156 used generatively. 2158 o Adds the ability to use a class of UN M.49 tags for supra- 2159 national regions and to resolve conflicts in the assignment of ISO 2160 3166 codes. 2162 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2163 as the mechanism for creating private-use language, script, and 2164 region subtags respectively. 2166 o Adds a well-defined extension mechanism. 2168 o Defines an extended language subtag, possibly for use with certain 2169 anticipated features of ISO 639-3. 2171 Ed Note: The following items are provided for the convenience of 2172 reviewers and will be removed from the final document. 2174 Changes between draft-ietf-ltru-registry-02 and this version are: 2176 o Modified the title and some of the front matter of Section 3.7 2177 from "Conversion of the RFC 3066 Language Tag Registry" 2178 (A.Phillips) 2180 o Modified the rules for registry creation so that no variant 2181 registrations are created ab initio. (#922) (J.Cowan) 2183 o Modified the document to replace 'Canonical' with 'Preferred- 2184 Value' and to implement the various design changes necessary to 2185 deal with canonicalization. (#954) (F.Ellermann, A.Phillips, et 2186 al) 2188 o Corrected the ABNF so that 'lang' is defined as 2*4ALPHA (J.Cowan) 2190 o Changed the requirement in Section 2.1.1 on truncation of tags 2191 from MUST to SHOULD and added a sentence about the harm this may 2192 cause. (F.Ellermann, D.Ewell) 2194 o Changed "MUST be very compelling" to "must (etc.)" in Section 3.5. 2195 (R.Presuhn) 2197 o Changed "STRONGLY RECOMMENDED" to "strongly RECOMMENDED" 2198 (R.Presuhn) 2200 o Added sentences pertaining to the File-Date record to Section 3.1. 2201 (#941) (R.Presuhn) 2203 o Changed the process by which the prototype registry is created 2204 from a mere document to an Informational RFC. (#838, #835) (??) 2206 o Changed the Security Considerations (Section 6) and Length 2207 Considerations (Section 2.1.1) sections to address potential 2208 buffer overflow attacks and suggest a lower limit on buffer length 2209 allocation (#944)(#965) (R.Presuhn, I.McDonald) 2211 o Clarified a sentence in Security Considerations (Section 6) to 2212 make clear that it refers to extensions and not the language 2213 subtag registry. (#965) (I.McDonald) 2215 o Added the limitation in the ABNF on the number of extlang subtags 2216 (limited to three) (#965) (R.Presuhn, A.Phillips) 2218 o Added notes to extlang and variant explaining that they should be 2219 used with their Recommended-Prefixes. (A.Phillips) 2221 o Changed the name of the 'Recommended-Prefix' field to 'Prefix' and 2222 the requirements for validating processors to require the prefix 2223 with variants and extlangs. (#1018) (J.Cowan, F.Ellerman) 2225 o Added notes about when variants may be used together and the 2226 relationship of the 'Prefix' field to this in Section 2.2.5 2227 (A.Phillips) 2229 o Specified that 'Prefix' fields may be added only to 'variant' 2230 subtag records and not to 'extlang' records. (J.Cowan) 2232 9. References 2234 9.1 Normative References 2236 [1] International Organization for Standardization, "ISO 639- 2237 1:2002, Codes for the representation of names of languages -- 2238 Part 1: Alpha-2 code", ISO Standard 639, 2002. 2240 [2] International Organization for Standardization, "ISO 639-2:1998 2241 - Codes for the representation of names of languages -- Part 2: 2242 Alpha-3 code - edition 1", August 1988. 2244 [3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2245 representation of names of scripts", January 2004. 2247 [4] International Organization for Standardization, "Codes for the 2248 representation of names of countries, 3rd edition", 2249 ISO Standard 3166, August 1988. 2251 [5] Statistical Division, United Nations, "Standard Country or Area 2252 Codes for Statistical Use", UN Standard Country or Area Codes 2253 for Statistical Use, Revision 4 (United Nations publication, 2254 Sales No. 98.XVII.9, June 1999. 2256 [6] International Organization for Standardization, "ISO/IEC 10646- 2257 1:2000. Information technology -- Universal Multiple-Octet 2258 Coded Character Set (UCS) -- Part 1: Architecture and Basic 2259 Multilingual Plane and ISO/IEC 10646-2:2001. Information 2260 technology -- Universal Multiple-Octet Coded Character Set 2261 (UCS) -- Part 2: Supplementary Planes, as, from time to time, 2262 amended, replaced by a new edition or expanded by the addition 2263 of new parts", 2000. 2265 [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2266 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 (work 2267 in progress), March 2005. 2269 [8] Bradner, S., "The Internet Standards Process -- Revision 3", 2270 BCP 9, RFC 2026, October 1996. 2272 [9] Hovey, R. and S. Bradner, "The Organizations Involved in the 2273 IETF Standards Process", BCP 11, RFC 2028, October 1996. 2275 [10] Bradner, S., "Key words for use in RFCs to Indicate Requirement 2276 Levels", BCP 14, RFC 2119, March 1997. 2278 [11] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 2279 Considerations Section in RFCs", BCP 26, RFC 2434, 2280 October 1998. 2282 [12] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 10646", 2283 RFC 2781, February 2000. 2285 [13] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2286 Understanding Concerning the Technical Work of the Internet 2287 Assigned Numbers Authority", RFC 2860, June 2000. 2289 [14] Klyne, G. and C. Newman, "Date and Time on the Internet: 2290 Timestamps", RFC 3339, July 2002. 2292 [15] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on 2293 Security Considerations", BCP 72, RFC 3552, July 2003. 2295 9.2 Informative References 2297 [16] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2298 Committee: Working principles for ISO 639 maintenance", 2299 March 2000, 2300 . 2302 [17] Raymond, E., "The Art of Unix Programming", 2003. 2304 [18] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2305 02 2004. 2307 [19] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2308 Datatypes Second Edition", 10 2004, < 2309 http://www.w3.org/TR/xmlschema-2/>. 2311 [20] Unicode Consortium, "The Unicode Consortium. The Unicode 2312 Standard, Version 4.1.0, defined by: The Unicode Standard, 2313 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2314 18578-1), as amended by Unicode 4.0.1 2315 (http://www.unicode.org/versions/Unicode4.0.1) and by Unicode 2316 4.1.0 (http://www.unicode.org/versions/Unicode4.1.0).", 2317 March 2005. 2319 [21] Alvestrand, H., "Tags for the Identification of Languages", 2320 RFC 1766, March 1995. 2322 [22] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word 2323 Extensions: Character Sets, Languages, and Continuations", 2324 RFC 2231, November 1997. 2326 [23] Alvestrand, H., "Tags for the Identification of Languages", 2327 BCP 47, RFC 3066, January 2001. 2329 Authors' Addresses 2331 Addison Phillips (editor) 2332 Quest Software 2334 Email: addison.phillips@quest.com 2336 Mark Davis (editor) 2337 IBM 2339 Email: mark.davis@us.ibm.com 2341 Appendix A. Acknowledgements 2343 Any list of contributors is bound to be incomplete; please regard the 2344 following as only a selection from the group of people who have 2345 contributed to make this document what it is today. 2347 The contributors to RFC 3066 and RFC 1766, the precursors of this 2348 document, made enormous contributions directly or indirectly to this 2349 document and are generally responsible for the success of language 2350 tags. 2352 The following people (in alphabetical order) contributed to this 2353 document or to RFCs 1766 and 3066: 2355 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2356 Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco 2357 Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable, 2358 John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank 2359 Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk- 2360 Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold, 2361 Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent 2362 Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald, 2363 Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George 2364 Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto 2365 Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois 2366 Yergeau and many, many others. 2368 Very special thanks must go to Harald Tveit Alvestrand, who 2369 originated RFCs 1766 and 3066, and without whom this document would 2370 not have been possible. Special thanks must go to Michael Everson, 2371 who has served as language tag reviewer for almost the complete 2372 period since the publication of RFC 1766. Special thanks to Doug 2373 Ewell, for his production of the first complete subtag registry, and 2374 his work in producing a test parser for verifying language tags. 2376 Appendix B. Examples of Language Tags (Informative) 2378 Simple language subtag: 2380 de (German) 2382 fr (French) 2384 ja (Japanese) 2386 i-enochian (example of a grandfathered tag) 2388 Language subtag plus Script subtag: 2390 zh-Hant (Chinese written using the Traditional Chinese script) 2392 zh-Hans (Chinese written using the Simplified Chinese script) 2394 sr-Cyrl (Serbian written using the Cyrillic script) 2396 sr-Latn (Serbian written using the Latin script) 2398 Language-Script-Region: 2400 zh-Hans-CN (Chinese written using the Simlified script as used in 2401 mainland China) 2403 sr-Latn-CS (Serbian written using the Latin script as used in 2404 Serbia and Montenegro) 2406 Language-Variant: 2408 en-boont (Boontling dialect of English) 2410 en-scouse (Scouse dialect of English) 2412 Language-Region-Variant: 2414 en-GB-scouse (Scouse dialect of English as used in the UK) 2416 Language-Script-Region-Variant: 2418 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2419 Latin script as used in Italy. Note that this tag is not 2420 recommended because subtag 'sl' has a Suppress-Script value of 2421 'Latn') 2423 Language-Region: 2425 de-DE (German for Germany) 2427 en-US (English as used in the United States) 2429 es-419 (Spanish for Latin America and Caribbean region using the 2430 UN region code) 2432 Private-use subtags: 2434 de-CH-x-phonebk 2436 az-Arab-x-AZE-derbend 2438 Extended language subtags (examples ONLY: extended languages must be 2439 defined by revision or update to this document): 2441 zh-min 2443 zh-min-nan-Hant-CN 2445 Private-use registry values: 2447 x-whatever (private use using the singleton 'x') 2449 qaa-Qaaa-QM-x-southern (all private tags) 2451 de-Qaaa (German, with a private script) 2453 sr-Latn-QM (Serbian, Latin-script, private region) 2455 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2457 Tags that use extensions (examples ONLY: extensions must be defined 2458 by revision or update to this document or by RFC): 2460 en-US-u-islamCal 2462 zh-CN-a-myExt-x-private 2464 en-a-myExt-b-another 2466 Some Invalid Tags: 2468 de-419-DE (two region tags) 2469 a-DE (use of a single character subtag in primary position; note 2470 that there are a few grandfathered tags that start with "i-" that 2471 are valid) 2473 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2474 prefix) 2476 Appendix C. Example Registry 2478 Example Registry 2480 File-Date: 2005-04-18 2481 %% 2482 Type: language 2483 Subtag: aa 2484 Description: Afar 2485 Added: 2004-07-06 2486 %% 2487 Type: language 2488 Subtag: ab 2489 Description: Abkhazian 2490 Added: 2004-07-06 2491 %% 2492 Type: language 2493 Subtag: ae 2494 Description: Avestan 2495 Added: 2004-07-06 2496 %% 2497 Type: language 2498 Subtag: ar 2499 Description: Arabic 2500 Added: 2004-07-06 2501 Suppress-Script: Arab 2502 Comment: Arabic text is usually written in Arabic script 2503 %% 2504 Type: language 2505 Subtag: qaa..qtz 2506 Description: PRIVATE USE 2507 Added: 2004-08-01 2508 Comment: Use private use codes in preference 2509 to the x- singleton for primary language 2510 Comment: This is an example of two comments. 2511 %% 2512 Type: script 2513 Subtag: Arab 2514 Description: Arabic 2515 Added: 2004-07-06 2516 %% 2517 Type: script 2518 Subtag: Armn 2519 Description: Armenian 2520 Added: 2004-07-06 2521 %% 2522 Type: script 2523 Subtag: Bali 2524 Description: Balinese 2525 Added: 2004-07-06 2526 %% 2527 Type: script 2528 Subtag: Batk 2529 Description: Batak 2530 Added: 2004-07-06 2531 %% 2532 Type: region 2533 Subtag: AA 2534 Description: PRIVATE USE 2535 Added: 2004-08-01 2536 %% 2537 Type: region 2538 Subtag: AD 2539 Description: Andorra 2540 Added: 2004-07-06 2541 %% 2542 Type: region 2543 Subtag: AE 2544 Description: United Arab Emirates 2545 Added: 2004-07-06 2546 %% 2547 Type: region 2548 Subtag: AX 2549 Description: Åland Islands 2550 Added: 2004-07-06 2551 Comments: The description shows a Unicode escape 2552 for the letter A-ring. 2553 %% 2554 Type: region 2555 Subtag: 001 2556 Description: World 2557 Added: 2004-07-06 2558 %% 2559 Type: region 2560 Subtag: 002 2561 Description: Africa 2562 Added: 2004-07-06 2563 %% 2564 Type: region 2565 Subtag: 003 2566 Description: North America 2567 Added: 2004-07-06 2568 %% 2569 Type: variant 2570 Subtag: 1901 2571 Description: Traditional German 2572 orthography 2573 Added: 2004-09-09 2574 Prefix: de 2575 Comment: 2576 %% 2577 Type: variant 2578 Subtag: 1996 2579 Description: German orthography of 1996 2580 Added: 2004-09-09 2581 Prefix: de 2582 %% 2583 Type: variant 2584 Subtag: boont 2585 Description: Boontling 2586 Added: 2003-02-14 2587 Prefix: en 2588 %% 2589 Type: variant 2590 Subtag: gaulish 2591 Description: Gaulish 2592 Added: 2001-05-25 2593 Prefix: cel 2594 %% 2595 Type: grandfathered 2596 Tag: art-lojban 2597 Description: Lojban 2598 Added: 2001-11-11 2599 Canonical: jbo 2600 Deprecated: 2003-09-02 2601 %% 2602 Type: grandfathered 2603 Tag: en-GB-oed 2604 Description: English, Oxford English Dictionary spelling 2605 Added: 2003-07-09 2606 %% 2607 Type: grandfathered 2608 Tag: i-ami 2609 Description: 'Amis 2610 Added: 1999-05-25 2611 %% 2612 Type: grandfathered 2613 Tag: i-bnn 2614 Description: Bunun 2615 Added: 1999-05-25 2616 %% 2617 Type: redundant 2618 Tag: az-Arab 2619 Description: Azerbaijani in Arabic script 2620 Added: 2003-05-30 2621 %% 2622 Type: redundant 2623 Tag: az-Cyrl 2624 Description: Azerbaijani in Cyrillic script 2625 Added: 2003-05-30 2626 %% 2628 Figure 8: Example of the Registry Format 2630 Intellectual Property Statement 2632 The IETF takes no position regarding the validity or scope of any 2633 Intellectual Property Rights or other rights that might be claimed to 2634 pertain to the implementation or use of the technology described in 2635 this document or the extent to which any license under such rights 2636 might or might not be available; nor does it represent that it has 2637 made any independent effort to identify any such rights. Information 2638 on the procedures with respect to rights in RFC documents can be 2639 found in BCP 78 and BCP 79. 2641 Copies of IPR disclosures made to the IETF Secretariat and any 2642 assurances of licenses to be made available, or the result of an 2643 attempt made to obtain a general license or permission for the use of 2644 such proprietary rights by implementers or users of this 2645 specification can be obtained from the IETF on-line IPR repository at 2646 http://www.ietf.org/ipr. 2648 The IETF invites any interested party to bring to its attention any 2649 copyrights, patents or patent applications, or other proprietary 2650 rights that may cover technology that may be required to implement 2651 this standard. Please address the information to the IETF at 2652 ietf-ipr@ietf.org. 2654 Disclaimer of Validity 2656 This document and the information contained herein are provided on an 2657 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2658 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2659 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2660 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2661 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2662 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2664 Copyright Statement 2666 Copyright (C) The Internet Society (2005). This document is subject 2667 to the rights, licenses and restrictions contained in BCP 78, and 2668 except as set forth therein, the authors retain all their rights. 2670 Acknowledgment 2672 Funding for the RFC Editor function is currently provided by the 2673 Internet Society.