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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: October 28, 2005 M. Davis, Ed. 5 IBM 6 April 26, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-01 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 October 28, 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 . . . . . . . . . . . . . . . 8 57 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 10 58 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 10 59 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 11 60 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 12 61 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 13 62 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 14 63 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 15 64 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 15 65 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 17 66 3.1 Format of the IANA Language Subtag Registry . . . . . . . 17 67 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 21 68 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 22 69 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 25 70 3.5 Possibilities for Registration . . . . . . . . . . . . . . 29 71 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 30 72 3.7 Conversion of the RFC 3066 Language Tag Registry . . . . . 33 73 4. Formation and Processing of Language Tags . . . . . . . . . . 36 74 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 36 75 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 38 76 4.3 Canonicalization of Language Tags . . . . . . . . . . . . 39 77 4.4 Considerations for Private Use Subtags . . . . . . . . . . 40 78 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 43 80 7. Character Set Considerations . . . . . . . . . . . . . . . . . 44 81 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 45 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 50 83 9.1 Normative References . . . . . . . . . . . . . . . . . . . 50 84 9.2 Informative References . . . . . . . . . . . . . . . . . . 51 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 52 86 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53 87 B. Examples of Language Tags (Informative) . . . . . . . . . . . 54 88 C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 57 89 Intellectual Property and Copyright Statements . . . . . . . . 61 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 *("-" extlang) 153 ["-" script] 154 ["-" region] 155 *("-" variant) 156 *("-" extension) 157 ["-" privateuse]) 158 / privateuse ; private-use tag 159 / grandfathered ; grandfathered registrations 161 lang = 2*3ALPHA ; 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 In particular, variant subtags SHOULD be used only with their 235 recommended prefix. In practice, this limits most tags to a sequence 236 of four subtags, and thus a maximum length of 26 characters 237 (excluding any extensions or private use sequences). This is because 238 subtags are limited to a length of eight characters and the extlang, 239 script, and region subtags are limited to even fewer characters. See 240 Section 4.1 for more information on selecting the most appropriate 241 Language Tag. 243 A conformant implementation MAY refuse to support the storage of 244 language tags which exceed a specified length. For an example, see 246 [RFC 2231] [22]. Any such limitation MUST be clearly documented, and 247 such documentation SHOULD include the disposition of any longer tags 248 (for example, whether an error value is generated or the language tag 249 is truncated). If truncation is permitted it SHOULD NOT permit a 250 subtag to be divided. 252 2.2 Language Subtag Sources and Interpretation 254 The namespace of language tags and their subtags is administered by 255 the Internet Assigned Numbers Authority (IANA) [13] according to the 256 rules in Section 5 of this document. The registry maintained by IANA 257 is the source for valid subtags: other standards referenced in this 258 section provide the source material for that registry. 260 Terminology in this section: 262 o Tag or tags refers to a complete language tag, such as 263 "fr-Latn-CA". Examples of tags in this document are enclosed in 264 double-quotes ("en-US"). 266 o Subtag refers to a specific section of a tag, delimited by hyphen, 267 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 268 this document are enclosed in single quotes ('Latn'). 270 o Code or codes refers to values defined in external standards (and 271 which are used as subtags in this document). For example, 'Latn' 272 is an [ISO 15924] [3] script code which was used to define the 273 'Latn' script subtag for use in a language tag. Examples of codes 274 in this document are enclosed in single quotes ('en', 'Latn'). 276 The definitions in this section apply to the various subtags within 277 the language tags defined by this document, excepting those 278 "grandfathered" tags defined in Section 2.2.8. 280 Language tags are designed so that each subtag type has unique length 281 and content restrictions. These make identification of the subtag's 282 type possible, even if the content of the subtag itself is 283 unrecognized. This allows tags to be parsed and processed without 284 reference to the latest version of the underlying standards or the 285 IANA registry and makes the associated exception handling when 286 parsing tags simpler. 288 Subtags in the IANA registry that do not come from an underlying 289 standard can only appear in specific positions in a tag. 290 Specifically, they can only occur as primary language subtags or as 291 variant subtags. 293 Note that sequences of private-use and extension subtags MUST occur 294 at the end of the sequence of subtags and MUST NOT be interspersed 295 with subtags defined elsewhere in this document. 297 Single letter and digit subtags are reserved for current or future 298 use. These include the following current uses: 300 o The single letter subtag 'x' is reserved to introduce a sequence 301 of private-use subtags. The interpretation of any private-use 302 subtags is defined solely by private agreement and is not defined 303 by the rules in this section or in any standard or registry 304 defined in this document. 306 o All other single letter subtags are reserved to introduce 307 standardized extension subtag sequences as described in 308 Section 3.6. 310 The single letter subtag 'i' is used by some grandfathered tags, such 311 as "i-enochian", where it always appears in the first position and 312 cannot be confused with an extension. 314 2.2.1 Primary Language Subtag 316 The primary language subtag is the first subtag in a language tag 317 (with the exception of private-use and certain grandfathered tags) 318 and cannot be omitted. The following rules apply to the primary 319 language subtag: 321 1. All two character language subtags were defined in the IANA 322 registry according to the assignments found in the standard ISO 323 639 Part 1, "ISO 639-1:2002, Codes for the representation of 324 names of languages -- Part 1: Alpha-2 code" [ISO 639-1] [1], or 325 using assignments subsequently made by the ISO 639 Part 1 326 maintenance agency or governing standardization bodies. 328 2. All three character language subtags were defined in the IANA 329 registry according to the assignments found in ISO 639 Part 2, 330 "ISO 639-2:1998 - Codes for the representation of names of 331 languages -- Part 2: Alpha-3 code - edition 1" [ISO 639-2] [2], 332 or assignments subsequently made by the ISO 639 Part 2 333 maintenance agency or governing standardization bodies. 335 3. The subtags in the range 'qaa' through 'qtz' are reserved for 336 private use in language tags. These subtags correspond to codes 337 reserved by ISO 639-2 for private use. These codes MAY be used 338 for non-registered primary-language subtags (instead of using 339 private-use subtags following 'x-'). Please refer to Section 4.4 340 for more information on private use subtags. 342 4. All four character language subtags are reserved for possible 343 future standardization. 345 5. All language subtags of 5 to 8 characters in length in the IANA 346 registry were defined via the registration process in Section 3.4 347 and MAY be used to form the primary language subtag. At the time 348 this document was created, there were no examples of this kind of 349 subtag and future registrations of this type will be discouraged: 350 primary languages are STRONGLY RECOMMENDED for registration with 351 ISO 639 and proposals rejected by ISO 639/RA will be closely 352 scrutinized before they are registered with IANA. 354 6. The single character subtag 'x' as the primary subtag indicates 355 that the language tag consists solely of subtags whose meaning is 356 defined by private agreement. For example, in the tag "x-fr-CH", 357 the subtags 'fr' and 'CH' should not be taken to represent the 358 French language or the country of Switzerland (or any other value 359 in the IANA registry) unless there is a private agreement in 360 place to do so. See Section 4.4. 362 7. The single character subtag 'i' is used by some grandfathered 363 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 364 grandfathered tags have a primary language subtag in their first 365 position) 367 8. Other values MUST NOT be assigned to the primary subtag except by 368 revision or update of this document. 370 Note: For languages that have both an ISO 639-1 two character code 371 and an ISO 639-2 three character code, only the ISO 639-1 two 372 character code is defined in the IANA registry. 374 Note: For languages that have no ISO 639-1 two character code and for 375 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 376 (Bibliographic) codes differ, only the Terminology code is defined in 377 the IANA registry. At the time this document was created, all 378 languages that had both kinds of three character code were also 379 assigned a two character code; it is not expected that future 380 assignments of this nature will occur. 382 Note: To avoid problems with versioning and subtag choice as 383 experienced during the transition between RFC 1766 and RFC 3066, as 384 well as the canonical nature of subtags defined by this document, the 385 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 386 RA-JAC) has included the following statement in [16]: 388 "A language code already in ISO 639-2 at the point of freezing ISO 389 639-1 shall not later be added to ISO 639-1. This is to ensure 390 consistency in usage over time, since users are directed in Internet 391 applications to employ the alpha-3 code when an alpha-2 code for that 392 language is not available." 394 In order to avoid instability of the canonical form of tags, if a two 395 character code is added to ISO 639-1 for a language for which a three 396 character code was already included in ISO 639-2, the two character 397 code will not be added as a subtag in the registry. See Section 3.3. 399 For example, if some content were tagged with 'haw' (Hawaiian), which 400 currently has no two character code, the tag would not be invalidated 401 if ISO 639-1 were to assign a two character code to the Hawaiian 402 language at a later date. 404 For example, one of the grandfathered IANA registrations is 405 "i-enochian". The subtag 'enochian' could be registered in the IANA 406 registry as a primary language subtag (assuming that ISO 639 does not 407 register this language first), making tags such as "enochian-AQ" and 408 "enochian-Latn" valid. 410 2.2.2 Extended Language Subtags 412 The following rules apply to the extended language subtags: 414 1. Three letter subtags immediately following the primary subtag are 415 reserved for future standardization, anticipating work that is 416 currently under way on ISO 639. 418 2. Extended language subtags MUST follow the primary subtag and 419 precede any other subtags. 421 3. There MAY be any additional number of extended language subtags. 423 4. Extended language subtags will not be registered except by 424 revision of this document. 426 5. Extended language subtags MUST NOT be used to form language tags 427 except by revision of this document. 429 Example: In a future revision or update of this document, the tag 430 "zh-gan" (registered under RFC 3066) might become a valid non- 431 grandfathered (that is, redundant) tag in which the subtag 'gan' 432 might represent the Chinese dialect 'Gan'. 434 2.2.3 Script Subtag 436 The following rules apply to the script subtags: 438 1. All four character subtags were defined according to ISO 15924 439 [3]--"Codes for the representation of the names of scripts": 440 alpha-4 script codes, or subsequently assigned by the ISO 15924 441 maintenance agency or governing standardization bodies, denoting 442 the script or writing system used in conjunction with this 443 language. 445 2. Script subtags MUST immediately follow the primary language 446 subtag and all extended language subtags and MUST occur before 447 any other type of subtag described below. 449 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 450 use in language tags. These subtags correspond to codes reserved 451 by ISO 15924 for private use. These codes MAY be used for non- 452 registered script values. Please refer to Section 4.4 for more 453 information on private-use subtags. 455 4. Script subtags cannot be registered using the process in 456 Section 3.4 of this document. Variant subtags may be considered 457 for registration for that purpose. 459 Example: "de-Latn" represents German written using the Latin script. 461 2.2.4 Region Subtag 463 The following rules apply to the region subtags: 465 1. The region subtag defines language variations used in a specific 466 region, geographic, or political area. Region subtags MUST 467 follow any language, extended language, or script subtags and 468 MUST precede all other subtags. 470 2. All two character subtags following the primary subtag were 471 defined in the IANA registry according to the assignments found 472 in ISO 3166 [4]--"Codes for the representation of names of 473 countries and their subdivisions - Part 1: Country 474 codes"--alpha-2 country codes or assignments subsequently made by 475 the ISO 3166 maintenance agency or governing standardization 476 bodies. 478 3. All three character codes consisting of digit (numeric) 479 characters were defined in the IANA registry according to the 480 assignments found in UN Standard Country or Area Codes for 481 Statistical Use [5] or assignments subsequently made by the 482 governing standards body. Note that not all of the UN M.49 codes 483 are defined in the IANA registry: 485 A. UN numeric codes assigned to 'macro-geographical 486 (continental)' or sub-regions not associated with an assigned 487 ISO 3166 alpha-2 code _are_ defined. 489 B. UN numeric codes for 'economic groupings' or 'other 490 groupings' are _not_ defined in the IANA registry and MUST 491 NOT be used to form language tags. 493 C. UN numeric codes for countries with ambiguous ISO 3166 494 alpha-2 codes as defined in Section 3.3 are defined in the 495 registry and are canonical for the given country or region 496 defined. 498 D. The alphanumeric codes in Appendix X of the UN document are 499 _not_ defined and MUST NOT be used to form language tags. 500 (At the time this document was created these values match the 501 ISO 3166 alpha-2 codes.) 503 4. There may be at most one region subtag in a language tag. 505 5. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 506 reserved for private use in language tags. These subtags 507 correspond to codes reserved by ISO 3166 for private use. These 508 codes MAY be used for private use region subtags (instead of 509 using a private-use subtag sequence). Please refer to 510 Section 4.4 for more information on private use subtags. 512 "de-CH" represents German ('de') as used in Switzerland ('CH'). 514 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 515 ('Latn') as used in Serbia and Montenegro ('CS'). 517 "es-419" represents Spanish ('es') as used in the UN-defined Latin 518 America and Caribbean region ('419'). 520 2.2.5 Variant Subtags 522 The following rules apply to the variant subtags: 524 1. Variant subtags are not associated with any external standard. 525 Variant subtags and their meanings are defined by the 526 registration process defined in Section 3.4. 528 2. Variant subtags MUST follow all of the other defined subtags, but 529 precede any extension or private-use subtag sequences. 531 3. More than one variant MAY be used to form the language tag. 533 4. Variant subtags MUST be registered with IANA according to the 534 rules in Section 3.4 of this document before being used to form 535 language tags. In order to distinguish variants from other types 536 of subtags, registrations must meet the following length and 537 content restrictions: 539 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 540 at least five characters long. 542 2. Variant subtags that begin with a digit (0-9) MUST be at 543 least four characters long. 545 "en-scouse" represents the Scouse dialect of English. 547 "de-CH-1996" represents German as used in Switzerland and as written 548 using the spelling reform beginning in the year 1996 C.E. 550 2.2.6 Extension Subtags 552 The following rules apply to extensions: 554 1. Extension subtags are separated from the other subtags defined 555 in this document by a single-letter subtag ("singleton"). The 556 singleton MUST be one allocated to a registration authority via 557 the mechanism described in Section 3.6 and cannot be the letter 558 'x', which is reserved for private-use subtag sequences. 560 2. Note: Private-use subtag sequences starting with the singleton 561 subtag 'x' are described below. 563 3. An extension MUST follow at least a primary language subtag. 564 That is, a language tag cannot begin with an extension. 565 Extensions extend language tags, they do not override or replace 566 them. For example, "a-value" is not a well-formed language tag, 567 while "de-a-value" is. 569 4. Each singleton subtag MUST appear at most one time in each tag 570 (other than as a private-use subtag). That is, singleton 571 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 572 ccc" is invalid because the subtag 'a' appears twice. Note that 573 the tag "en-a-bbb-x-a-ccc" is valid because the second 574 appearance of the singleton 'a' is in a private use sequence. 576 5. Extension subtags MUST meet all of the requirements for the 577 content and format of subtags defined in this document. 579 6. Extension subtags MUST meet whatever requirements are set by the 580 document that defines their singleton prefix and whatever 581 requirements are provided by the maintaining authority. 583 7. Each extension subtag MUST be from two to eight characters long 584 and consist solely of letters or digits, with each subtag 585 separated by a single '-'. 587 8. Each singleton MUST be followed by at least one extension 588 subtag. For example, the tag "tlh-a-b-foo" is invalid because 589 the first singleton 'a' is followed immediately by another 590 singleton 'b'. 592 9. Extension subtags MUST follow all language, extended language, 593 script, region and variant subtags in a tag. 595 10. All subtags following the singleton and before another singleton 596 are part of the extension. Example: In the tag "fr-a-Latn", the 597 subtag 'Latn' does not represent the script subtag 'Latn' 598 defined in the IANA Language Subtag Registry. Its meaning is 599 defined by the extension 'a'. 601 11. In the event that more than one extension appears in a single 602 tag, the tag SHOULD be canonicalized as described in 603 Section 4.3. 605 For example, if the prefix singleton 'r' and the shown subtags were 606 defined, then the following tag would be a valid example: "en-Latn- 607 GB-boont-r-extended-sequence-x-private" 609 2.2.7 Private Use Subtags 611 The following rules apply to private-use subtags: 613 1. Private-use subtags are separated from the other subtags defined 614 in this document by the reserved single-character subtag 'x'. 616 2. Private-use subtags MUST follow all language, extended language, 617 script, region, variant, and extension subtags in the tag. 618 Another way of saying this is that all subtags following the 619 singleton 'x' MUST be considered private use. Example: The 620 subtag 'US' in the tag "en-x-US" is a private use subtag. 622 3. A tag MAY consist entirely of private-use subtags. 624 4. No source is defined for private use subtags. Use of private use 625 subtags is by private agreement only. 627 For example: Users who wished to utilize SIL Ethnologue for 628 identification might agree to exchange tags such as "az-Arab-x-AZE- 629 derbend". This example contains two private-use subtags. The first 630 is 'AZE' and the second is 'derbend'. 632 2.2.8 Pre-Existing RFC 3066 Registrations 634 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 635 maintain their validity. IANA will maintain these tags in the 636 registry under either the "grandfathered" or "redundant" type. For 637 more information see Section 3.7. 639 It is important to note that all language tags formed under the 640 guidelines in this document were either legal, well-formed tags or 641 could have been registered under RFC 3066. 643 2.2.9 Classes of Conformance 645 Implementations may wish to express their level of conformance with 646 the rules and practices described in this document. There are 647 generally two classes of conforming implementations: "well-formed" 648 processors and "validating" processors. Claims of conformance SHOULD 649 explicitly reference one of these definitions. 651 An implementation that claims to check for well-formed language tags 652 MUST: 654 o Check that the tag and all of its subtags, including extension and 655 private-use subtags, conform to the ABNF or that the tag is on the 656 list of grandfathered tags. 658 o Check that singleton subtags that identify extensions do not 659 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 660 formed. 662 Well-formed processors are strongly encouraged to implement the 663 canonicalization rules contained in Section 4.3. 665 An implementation that claims to be validating MUST: 667 o Check that the tag is well-formed. 669 o Specify the particular registry date for which the implementation 670 performs validation of subtags. 672 o Check that either the tag is a grandfathered tag, or that all 673 language, script, region, and variant subtags consist of valid 674 codes for use in language tags according to the IANA registry as 675 of the particular date specified by the implementation. 677 o Specify which, if any, extension RFCs as defined in Section 3.6 678 are supported, including version, revision, and date. 680 o For any such extensions supported, check that all subtags used in 681 that extension are valid. 683 o If the processor generates tags, it MUST do so in canonical form, 684 including any supported extensions, as defined in Section 4.3. 686 3. Registry Format and Maintenance 688 This section defines the Language Subtag Registry and the maintenance 689 and update procedures associated with it. 691 The language subtag registry will be maintained so that, except for 692 extension subtags, it is possible to validate all of the subtags that 693 appear in a language tag under the provisions of this document or its 694 revisions or successors. In addition, the meaning of the various 695 subtags will be unambiguous and stable over time. (The meaning of 696 private-use subtags, of course, is not defined by the IANA registry.) 698 The registry defined under this document contains a comprehensive 699 list of all of the subtags valid in language tags. This allows 700 implementers a straightforward and reliable way to validate language 701 tags. 703 3.1 Format of the IANA Language Subtag Registry 705 The IANA Language Subtag Registry ("the registry") will consist of a 706 text file that is machine readable in the format described in this 707 section, plus copies of the registration forms approved by the 708 Language Subtag Reviewer in accordance with the process described in 709 Section 3.4. With the exception of the registration forms for 710 grandfathered and redundant tags, no registration records will be 711 maintained for the initial set of subtags. 713 The registry will be in a modified record-jar format text file [17]. 714 Lines are limited to 72 characters, including all whitespace. 716 Records are separated by lines containing only the sequence "%%" 717 (%x25.25). 719 Each field can be viewed as a single, logical line of ASCII 720 characters, comprising a field-name and a field-body separated by a 721 COLON character (%x3A). For convenience, the field-body portion of 722 this conceptual entity can be split into a multiple-line 723 representation; this is called "folding". The format of the registry 724 is described by the following ABNF (per [7]): 726 registry = record *("%%" CRLF record) 727 record = 1*( field-name *SP ":" *SP field-body CRLF ) 728 field-name = *(ALPHA/NUM/"-") 729 field-body = *(ASCCHAR/LWSP) 730 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 731 UNICHAR = "&#x" 2*6HEXDIG ";" 733 The sequence '..' (%x2E.2E) in a field-body denotes a range of 734 values. Such a range represents all subtags of the same length that 735 are alphabetically within that range, including the values explicitly 736 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 738 Characters from outside the US-ASCII repertoire, as well as the 739 AMPERSAND character ("&", %x26) when it occurs in a field-body are 740 represented by a "Numeric Character Reference" using hexadecimal 741 notation in the style used by XML 1.0 [18] (see 742 ). This consists of the 743 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 744 of the character's code point in ISO/IEC 10646 [6] followed by a 745 closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would 746 be represented by the sequence "€". Note that the hexadecimal 747 notation may have between two and six digits. 749 All fields whose field-body contains a date value use the "full-date" 750 format specified in RFC 3339 [14]. For example: "2004-06-28" 751 represents June 28, 2004 in the Gregorian calendar. 753 The first record in the file contains the single field whose field- 754 name is "File-Date" and whose field-body contains the last 755 modification date of the registry: 757 File-Date: 2004-06-28 758 %% 760 Subsequent records represent subtags in the registry. Each of the 761 fields in each record MUST occur no more than once, unless otherwise 762 noted below. Each record MUST contain the following fields: 764 o 'Type' 766 * Type's field-value MUST consist of one of the following 767 strings: "language", "extlang", "script", "region", "variant", 768 "grandfathered", and "redundant" and denotes the type of tag or 769 subtag. 771 o Either 'Subtag' or 'Tag' 773 * Subtag's field-value contains the subtag being defined. This 774 field MUST only appear in records of whose Type has one of 775 these values: "language", "extlang", "script", "region", or 776 "variant". 778 * Tag's field-value contains a complete language tag. This field 779 MUST only appear in records whose Type has one of these values: 780 "grandfathered" or "redundant". 782 o Description 784 * Description's field-value contains a non-normative description 785 of the subtag or tag. 787 o Added 789 * Added's field-value contains the date the record was added to 790 the registry. 792 The field 'Description' MAY appear more than one time. The 793 'Description' field must contain a description of the tag being 794 registered written or transcribed into the Latin script; it may also 795 include a description in a non-Latin script. The 'Description' field 796 is used for identification purposes and should not be taken to 797 represent the actual native name of the language or variation or to 798 be in any particular language. Most descriptions are taken directly 799 from source standards such as ISO 639 or ISO 3166. 801 Note: Descriptions in registry entries that correspond to ISO 639, 802 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 803 the meaning of that identifier as defined in the source standard at 804 the time it was added to the registry. The description does not 805 replace the content of the source standard itself. The descriptions 806 are not intended to be the English localized names for the subtags. 807 Localization or translation of language tag and subtag descriptions 808 is out of scope of this document. 810 Each record MAY also contain the following fields: 812 o Canonical 814 * For fields of type 'language', 'extlang', 'script', 'region', 815 and 'variant', a canonical mapping of this record to a subtag 816 record of the same 'Type'. 818 * For fields of type 'grandfathered' and 'redundant', a canonical 819 mapping to a complete language tag. 821 o Deprecated 823 * Deprecated's field-value contains the date the record was 824 deprecated. 826 o Recommended-Prefix 828 * Recommended-Prefix's field-value contains a language tag with 829 which this subtag may be used to form a new language tag, 830 perhaps with other subtags as well. This field MUST only 831 appear in records whose 'Type' field-value is 'variant' or 832 'extlang'. For example, the 'Recommended-Prefix' for the 833 variant 'scouse' is 'en', meaning that the tags "en-scouse" and 834 "en-GB-scouse" might be appropriate while the tag "is-scouse" 835 is not. 837 o Comments 839 * Comments contains additional information about the subtag, as 840 deemed appropriate for understanding the registry and 841 implementing language tags using the subtag or tag. 843 o Suppress-Script 845 * Suppress-Script contains a script subtag that SHOULD NOT be 846 used to form language tags with the associated primary language 847 subtag. This field MUST only appear in records whose 'Type' 848 field-value is 'language'. See Section 4.1. 850 The field 'Canonical' SHALL NOT be added to any record already in the 851 registry. The field 'Canonical' SHALL NOT be modified except for 852 records of type "grandfathered": therefore a subtag whose record 853 contains no canonical mapping when the record is created is a 854 canonical form and will remain so. 856 The 'Canonical' field in records of type "grandfathered" and 857 "redundant" contains whole language tags that are STRONGLY 858 RECOMMENDED for use in place of the record's value. In many cases 859 the mappings were created by deprecation of the tags during the 860 period before this document was adopted. For example, the tag "no- 861 nyn" was deprecated in favor of the ISO 639-1 defined language code 862 'nn'. 864 Note that a record that has a 'Canonical' field MUST have a 865 'Deprecated' field also (although the converse is not true). 867 The field 'Deprecated' MAY be added to any record via the maintenance 868 process described in Section 3.2 or via the registration process 869 described in Section 3.4. Usually the addition of a 'Deprecated' 870 field is due to the action of one of the standards bodies, such as 871 ISO 3166, withdrawing a code. In some historical cases it may not 872 have been possible to reconstruct the original deprecation date. 873 For these cases, an approximate date appears in the registry. 874 Although valid in language tags, subtags and tags with a 'Deprecated' 875 field are deprecated and validating processors SHOULD NOT generate 876 these subtags. Note that a record that contains a 'Deprecated' field 877 and no corresponding 'Canonical' field has no replacement mapping. 879 The field 'Recommended-Prefix' MAY appear more than once per record. 880 Additional fields of this type MAY be added to a record via the 881 registration process. The field-value of of this field consists of a 882 language tag that is RECOMMENDED for use as a prefix for this subtag. 883 For example, the variant subtag 'scouse' has a recommended prefix of 884 "en". This means that tags starting with the prefix "en-" are most 885 appropriate with this subtag, so "en-Latn-scouse" and "en-GB-scouse" 886 are both acceptable, while the tag "fr-scouse" is probably an 887 inappropriate choice. 889 The field of type Recommended-Prefix MUST NOT be removed from any 890 record. The field-value for this type of field MUST NOT be modified. 892 The field 'Comments' MAY appear more than once per record. This 893 field MAY be inserted or changed via the registration process and no 894 guarantee of stability is provided. The content of this field is not 895 restricted, except by the need to register the information, the 896 suitability of the request, and by reasonable practical size 897 limitations. Long screeds about a particular subtag are frowned 898 upon. 900 The field 'Suppress-Script' MUST only appear in records whose 'Type' 901 field-value is 'language'. This field may appear at most one time in 902 a record. This field indicates a script used to write the 903 overwhelming majority of documents for the given language and which 904 therefore adds no distinguishing information to a language tag. For 905 example, virtually all Icelandic documents are written in the Latin 906 script, making the subtag 'Latn' redundant in the tag "is-Latn". 908 For examples of registry entries and their format, see Appendix C. 910 3.2 Maintenance of the Registry 912 Maintenance of the registry requires that as new codes are assigned 913 by ISO 639, ISO 15924, and ISO 3166, the Language Subtag Reviewer 914 will evaluate each assignment, determine whether it conflicts with 915 existing registry entries, and submit the information to IANA for 916 inclusion in the registry. If an assignment takes place and the 917 Language Subtag Reviewer does not do this in a timely manner, then 918 any interested party may use the procedure in Section 3.4 to register 919 the appropriate update. 921 Note: The redundant and grandfathered entries together are the 922 complete list of tags registered under RFC 3066 [23]. The redundant 923 tags are those that can now be formed using the subtags defined in 924 the registry together with the rules of Section 2.2. The 925 grandfathered entries are those that can never be legal under those 926 same provisions. The items in both lists are permanent and stable, 927 although grandfathered items may be deprecated over time. Refer to 928 Section 3.7 for more information. 930 RFC 3066 tags that were deprecated prior to the adoption of this 931 document are part of the list of grandfathered tags and their 932 component subtags were not included as registered variants (although 933 they remain eligible for registration). For example, the tag "art- 934 lojban" was deprecated in favor of the language subtag 'jbo'. 936 The Language Subtag Reviewer MUST ensure that new subtags meet the 937 requirements in Section 4.1 or submit an appropriate alternate subtag 938 as described in that section. If a change or addition to the 939 registry is required, the Language Subtag Reviewer will prepare the 940 complete record, including all fields, and forward it to IANA for 941 insertion into the registry. If this represents a new subtag, then 942 the message will indicate that this represents an INSERTION of a 943 record. If this represents a change to an existing subtag, then the 944 message must indicate that this represents a MODIFICATION, as shown 945 in the following example: 947 LANGUAGE SUBTAG MODIFICATION 948 File-Date: 2005-01-02 949 %% 950 Type: variant 951 Subtag: nedis 952 Description: Natisone dialect 953 Description: Nadiza dialect 954 Added: 2003-10-09 955 Recommended-Prefix: sl 956 Comments: This is a comment shown 957 as an example. 958 %% 960 Figure 4 962 Whenever an entry is created or modified in the registry, the 'File- 963 Date' record at the start of the registry is updated to reflect the 964 most recent modification date in the RFC 3339 [14] "full-date" 965 format. 967 3.3 Stability of IANA Registry Entries 969 The stability of entries and their meaning in the registry is 970 critical to the long term stability of language tags. The rules in 971 this section guarantee that a specific language tag's meaning is 972 stable over time and will not change and that the choice of language 973 tag for specific content is also stable over time. 975 These rules specifically deal with how changes to codes (including 976 withdrawal and deprecation of codes) maintained by ISO 639, ISO 977 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 978 Subtag Registry. Assignments to the IANA Language Subtag Registry 979 MUST follow the following stability rules: 981 o Values in the fields 'Type', 'Subtag', 'Tag', 'Added' and 982 'Canonical' MUST NOT be changed and are guaranteed to be stable 983 over time. 985 o Values in the 'Description' field MUST NOT be changed in a way 986 that would invalidate previously-existing tags. They may be 987 broadened somewhat in scope, changed to add information, or 988 adapted to the most common modern usage. For example, countries 989 occasionally change their official names: an historical example of 990 this would be "Upper Volta" changing to "Burkina Faso". 992 o Values in the field 'Recommended-Prefix' MAY be added via the 993 registration process. 995 o Values in the field 'Recommended-Prefix' MAY be modified, so long 996 as the modifications broaden the set of recommended prefixes. 997 That is, a recommended prefix MAY be replaced by one of its own 998 prefixes. For example, the prefix "en-US" could be replaced by 999 "en", but not by the ranges "en-Latn", "fr", or "en-US-boont". 1001 o Values in the field 'Recommended-Prefix' MUST NOT be removed. 1003 o The field 'Comments' MAY be added, changed, modified, or removed 1004 via the registration process or any of the processes or 1005 considerations described in this section. 1007 o The field 'Suppress-Script' MAY be added or removed via the 1008 registration process. 1010 o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1011 conflict with existing subtags of the associated type and whose 1012 meaning is not the same as an existing subtag of the same type are 1013 entered into the IANA registry as new records and their value is 1014 canonical for the meaning assigned to them. 1016 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1017 withdrawn by their respective maintenance or registration 1018 authority remain valid in language tags. The registration process 1019 MAY be used to add a note indicating the withdrawal of the code by 1020 the respective standard. 1022 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that do not 1023 conflict with existing subtags of the associated type but which 1024 represent the same meaning as an existing subtag of that type are 1025 entered into the IANA registry as new records. The field 1026 'canonical value' for that record MUST contain the existing subtag 1027 of the same meaning 1029 Example If ISO 3166 were to assign the code 'IM' to represent the 1030 value "Isle of Man" (represented in the IANA registry by the UN 1031 M.49 code '833'), '833' remains the canonical subtag and 'IM' 1032 would be assigned '833' as a canonical value. This prevents 1033 tags that are in canonical form from becoming non-canonical. 1035 Example If the tag 'enochian' were registered as a primary 1036 language subtag and ISO 639 subsequently assigned an alpha-3 1037 code to the same language, the new ISO 639 code would be 1038 entered into the IANA registry as a subtag with a canonical 1039 mapping to 'enochian'. The new ISO code can be used, but it is 1040 not canonical. 1042 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1043 with existing subtags of the associated type MUST NOT be entered 1044 into the registry. The following additional considerations apply: 1046 * For ISO 639 codes, if the newly assigned code's meaning is not 1047 represented by a subtag in the IANA registry, the Language 1048 Subtag Reviewer, as described in Section 3.4, shall prepare a 1049 proposal for entering in the IANA registry as soon as practical 1050 a registered language subtag as an alternate value for the new 1051 code. The form of the registered language subtag will be at 1052 the discretion of the Language Subtag Reviewer and must conform 1053 to other restrictions on language subtags in this document. 1055 * For all subtags whose meaning is derived from an external 1056 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if a 1057 new meaning is assigned to an existing code and the new meaning 1058 broadens the meaning of that code, then the meaning for the 1059 associated subtag MAY be changed to match. The meaning of a 1060 subtag MUST NOT be narrowed, however, as this can result in an 1061 unknown proportion of the existing uses of a subtag becoming 1062 invalid. Note: ISO 639 MA/RA has adopted a similar stability 1063 policy. 1065 * For ISO 15924 codes, if the newly assigned code's meaning is 1066 not represented by a subtag in the IANA registry, the Language 1067 Subtag Reviewer, as described in Section 3.4, shall prepare a 1068 proposal for entering in the IANA registry as soon as practical 1069 a registered variant subtag as an alternate value for the new 1070 code. The form of the registered variant subtag will be at the 1071 discretion of the Language Subtag Reviewer and must conform to 1072 other restrictions on variant subtags in this document. 1074 * For ISO 3166 codes, if the newly assigned code's meaning is 1075 associated with the same UN M.49 code as another 'region' 1076 subtag, then the existing region subtag remains as the 1077 canonical entry for that region and no new entry is created. A 1078 comment MAY be added to the existing region subtag indicating 1079 the relationship to the new ISO 3166 code. 1081 * For ISO 3166 codes, if the newly assigned code's meaning is 1082 associated with a UN M.49 code that is not represented by an 1083 existing region subtag, then then the Language Subtag Reviewer, 1084 as described in Section 3.4, shall prepare a proposal for 1085 entering the appropriate numeric UN country code as an entry in 1086 the IANA registry. 1088 * For ISO 3166 codes, if there is no associated UN numeric code, 1089 then the Language Subtag Reviewer SHALL petition the UN to 1090 create one. If there is no response from the UN within ninety 1091 days of the request being sent, the Language Subtag Reviewer 1092 shall prepare a proposal for entering in the IANA registry as 1093 soon as practical a registered variant subtag as an alternate 1094 value for the new code. The form of the registered variant 1095 subtag will be at the discretion of the Language Subtag 1096 Reviewer and must conform to other restrictions on variant 1097 subtags in this document. This situation is very unlikely to 1098 ever occur. 1100 o Stability provisions apply to grandfathered tags with this 1101 exception: should all of the subtags in a grandfathered tag become 1102 valid subtags in the IANA registry, then the grandfathered tag 1103 MUST be marked as redundant. Note that this will not affect 1104 language tags that match the grandfathered tag, since these tags 1105 will now match valid generative subtag sequences. For example, if 1106 the subtag 'gan' in the language tag "zh-gan" were to be 1107 registered as an extended language subtag, then the grandfathered 1108 tag "zh-gan" would be deprecated (but existing content or 1109 implementations that use "zh-gan" would remain valid). 1111 3.4 Registration Procedure for Subtags 1113 The procedure given here MUST be used by anyone who wants to use a 1114 subtag not currently in the IANA Language Subtag Registry. 1116 Only subtags of type 'language' and 'variant' will be considered for 1117 independent registration of new subtags. Handling of subtags 1118 required for stability and subtags required to keep the registry 1119 synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within 1120 the limits defined by this document are described in Section 3.2. 1121 Stability provisions are described in Section 3.3. 1123 This procedure MAY also be used to register or alter the information 1124 for the "Description", "Comments", "Deprecated", or "Recommended- 1125 Prefix" fields in a subtag's record as described in Figure 7. 1126 Changes to all other fields in the IANA registry are NOT permitted. 1128 Registering a new subtag or requesting modifications to an existing 1129 tag or subtag starts with the requster filling out the registration 1130 form reproduced below. Note that each response is not limited in 1131 size and should take the room necessary to adequately describe the 1132 registration. The fields in the "Record Requested" section SHOULD 1133 follow the requirements in Section 3.1. 1135 LANGUAGE SUBTAG REGISTRATION FORM 1136 1. Name of requester: 1137 2. E-mail address of requester: 1138 3. Record Requested: 1140 Type: 1141 Subtag: 1142 Description: 1143 Recommended-Prefix: 1144 Canonical: 1145 Deprecated: 1146 Suppress-Script: 1147 Comments: 1149 4. Intended meaning of the subtag: 1150 5. Reference to published description 1151 of the language (book or article): 1152 6. Any other relevant information: 1154 Figure 5 1156 The subtag registration form MUST be sent to 1157 for a two week review period before it can 1158 be submitted to IANA. (This is an open list. Requests to be added 1159 should be sent to .) 1161 Variant subtags are generally registered for use with a particular 1162 range of language tags. For example, the subtag 'scouse' is intended 1163 for use with language tags that start with the primary language 1164 subtag "en", since Scouse is a dialect of English. Thus the subtag 1165 'scouse' could be included in tags such as "en-Latn-scouse" or "en- 1166 GB-scouse". This information is stored in the "Recommended-Prefix" 1167 field in the registry. Variant registration requests are REQUIRED to 1168 include at least one "Recommended-Prefix" field in the registration 1169 form. 1171 Any subtag MAY be incorporated into a variety of language tags, 1172 according to the rules of Section 2.1, including tags that do not 1173 match any of the recommended prefixes of the registered subtag. 1174 (Note that this is probably a poor choice.) This makes validation 1175 simpler and thus more uniform across implementations, and does not 1176 require the registration of a separate subtag for the same purpose 1177 and meaning but a different recommended prefix. 1179 The recommended prefixes for a given registered subtag will be 1180 maintained in the IANA registry as a guide to usage. If it is 1181 necessary to add an additional prefix to that list for an existing 1182 language tag, that can be done by filing an additional registration 1183 form. In that form, the "Any other relevant information:" field 1184 should indicate that it is the addition of an additional recommended 1185 prefix. 1187 Requests to add a recommended prefix to a subtag that imply a 1188 different semantic meaning will probably be rejected. For example, a 1189 request to add the prefix "de" to the subtag 'nedis' so that the tag 1190 "de-nedis" represented some German dialect would be rejected. The 1191 'nedis' subtag represents a particular Slovenian dialect and the 1192 additional registration would change the semantic meaning assigned to 1193 the subtag. A separate subtag should be proposed instead. 1195 The 'Description' field must contain a description of the tag being 1196 registered written or transcribed into the Latin script; it may also 1197 include a description in a non-Latin script. Non-ASCII characters 1198 must be escaped using the syntax described in Section 3.1. The 1199 'Description' field is used for identification purposes and should 1200 not be taken to represent the actual native name of the language or 1201 variation or to be in any particular language. 1203 While the 'Description' field itself is not guaranteed to be stable 1204 and errata corrections may be undertaken from time to time, attempts 1205 to provide translations or transcriptions of entries in the registry 1206 itself will probably be frowned upon by the community or rejected 1207 outright, as changes of this nature may impact the provisions in 1208 Section 3.3. 1210 The Language Subtag Reviewer is responsible for responding to 1211 requests for the registration of subtags through the registration 1212 process and is appointed by the IESG. 1214 When the two week period has passed the Language Subtag Reviewer 1215 either forwards the record to be inserted or modified to 1216 iana@iana.org according to the procedure described in Section 3.2, or 1217 rejects the request because of significant objections raised on the 1218 list or due to problems with constraints in this document (which 1219 should be explicitly cited). The reviewer may also extend the review 1220 period in two week increments to permit further discussion. The 1221 reviewer must indicate on the list whether the registration has been 1222 accepted, rejected, or extended following each two week period. 1224 Note that the reviewer can raise objections on the list if he or she 1225 so desires. The important thing is that the objection must be made 1226 publicly. 1228 The applicant is free to modify a rejected application with 1229 additional information and submit it again; this restarts the two 1230 week comment period. 1232 Decisions made by the reviewer may be appealed to the IESG [RFC 2028] 1233 [9] under the same rules as other IETF decisions [RFC 2026] [8]. 1235 All approved registration forms are available online in the directory 1236 http://www.iana.org/numbers.html under "languages". 1238 Updates or changes to existing records, including previous 1239 registrations, follow the same procedure as new registrations. The 1240 Language Subtag Reviewer decides whether there is consensus to update 1241 the registration following the two week review period; normally 1242 objections by the original registrant will carry extra weight in 1243 forming such a consensus. 1245 Registrations are permanent and stable. Once registered, subtags 1246 will not be removed from the registry and will remain the canonical 1247 method of referring to a specific language or variant. This 1248 provision does not apply to grandfathered tags, which may become 1249 deprecated due to registration of subtags. For example, the tag 1250 "i-navajo" is deprecated in favor of the ISO 639-1 based subtag 'nv'. 1252 Note: The purpose of the "published description" in the registration 1253 form is intended as an aid to people trying to verify whether a 1254 language is registered or what language or language variation a 1255 particular subtag refers to. In most cases, reference to an 1256 authoritative grammar or dictionary of that language will be useful; 1257 in cases where no such work exists, other well known works describing 1258 that language or in that language may be appropriate. The subtag 1259 reviewer decides what constitutes "good enough" reference material. 1260 This requirement is not intended to exclude particular languages or 1261 dialects due to the size of the speaker population or lack of a 1262 standardized orthography. Minority languages will be considered 1263 equally on their own merits. 1265 3.5 Possibilities for Registration 1267 Possibilities for registration of subtags or information about 1268 subtags include: 1270 o Primary language subtags for languages not listed in ISO 639 that 1271 are not variants of any listed or registered language can be 1272 registered. At the time this document was created there were no 1273 examples of this form of subtag. Before attempting to register a 1274 language subtag, there MUST be an attempt to register the language 1275 with ISO 639. No language subtags will be registered for codes 1276 that exist in ISO 639-1 or ISO 639-2, which are under 1277 consideration by the ISO 639 maintenance or registration 1278 authorities, or which have never been attempted for registration 1279 with those authorities. If ISO 639 has previously rejected a 1280 language for registration, it is reasonable to assume that there 1281 MUST be additional very compelling evidence of need before it will 1282 be registered in the IANA registry (to the extent that it is very 1283 unlikely that any subtags will be registered of this type). 1285 o Dialect or other divisions or variations within a language, its 1286 orthography, writing system, regional or historical usage, 1287 transliteration or other transformation, or distinguishing 1288 variation may be registered as variant subtags. An example is the 1289 'scouse' subtag (the Scouse dialect of English). 1291 o The addition or maintenance of fields (generally of an 1292 informational nature) in Tag or Subtag records as described in 1293 Section 3.1 and subject to the stability provisions in 1294 Section 3.3. This includes descriptions, recommended prefixes, 1295 comments, deprecation of obsolete items, or the addition of script 1296 or extlang information to primary language subtags. 1298 This document leaves the decision on what subtags or changes to 1299 subtags are appropriate (or not) to the registration process 1300 described in Section 3.4. 1302 Note: four character primary language subtags are reserved to allow 1303 for the possibility of alpha4 codes in some future addition to the 1304 ISO 639 family of standards. 1306 ISO 639 defines a maintenance agency for additions to and changes in 1307 the list of languages in ISO 639. This agency is: 1309 International Information Centre for Terminology (Infoterm) 1310 Aichholzgasse 6/12, AT-1120 1311 Wien, Austria 1312 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1314 ISO 639-2 defines a maintenance agency for additions to and changes 1315 in the list of languages in ISO 639-2. This agency is: 1317 Library of Congress 1318 Network Development and MARC Standards Office 1319 Washington, D.C. 20540 USA 1320 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1321 URL: http://www.loc.gov/standards/iso639 1323 The maintenance agency for ISO 3166 (country codes) is: 1325 ISO 3166 Maintenance Agency 1326 c/o International Organization for Standardization 1327 Case postale 56 1328 CH-1211 Geneva 20 Switzerland 1329 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1330 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1332 The registration authority for ISO 15924 (script codes) is: 1334 Unicode Consortium Box 391476 1335 Mountain View, CA 94039-1476, USA 1336 URL: http://www.unicode.org/iso15924 1338 The Statistics Division of the United Nations Secretariat maintains 1339 the Standard Country or Area Codes for Statistical Use and can be 1340 reached at: 1342 Statistical Services Branch 1343 Statistics Division 1344 United Nations, Room DC2-1620 1345 New York, NY 10017, USA 1347 Fax: +1-212-963-0623 1348 E-mail: statistics@un.org 1349 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1351 3.6 Extensions and Extensions Namespace 1353 Extension subtags are those introduced by single-letter subtags other 1354 than 'x-'. They are reserved for the generation of identifiers which 1355 contain a language component, and are compatible with applications 1356 understand language tags. For example, they might be used to define 1357 locale identifiers, which are generally based on language. 1359 The structure and form of extensions are defined by this document so 1360 that implementations can be created that are forward compatible with 1361 applications that may be created using single-letter subtags in the 1362 future. In addition, defining a mechanism for maintaining single- 1363 letter subtags will lend to the stability of this document by 1364 reducing the likely need for future revisions or updates. 1366 Allocation of a single-letter subtag shall take the form of an RFC 1367 defining the name, purpose, processes, and procedures for maintaining 1368 the subtags. The maintaining or registering authority, including 1369 name, contact email, discussion list email, and URL location of the 1370 registry must be indicated clearly in the RFC. The RFC MUST specify 1371 or include each of the following: 1373 o The specification MUST reference the specific version or revision 1374 of this document that governs its creation and MUST reference this 1375 section of this document. 1377 o The specification and all subtags defined by the specification 1378 MUST follow the ABNF and other rules for the formation of tags and 1379 subtags as defined in this document. In particular it MUST 1380 specify that case is not significant and that subtags MUST NOT 1381 exceed eight characters in length. 1383 o The specification MUST specify a canonical representation. 1385 o The specification of valid subtags MUST be available over the 1386 Internet and at no cost. 1388 o The specification MUST be in the public domain or available via a 1389 royalty-free license acceptable to the IETF and specified in the 1390 RFC. 1392 o The specification MUST be versioned and each version of the 1393 specification MUST be numbered, dated, and stable. 1395 o The specification MUST be stable. That is, extension subtags, 1396 once defined by a specification, MUST NOT be retracted or change 1397 in meaning in any substantial way. 1399 o The specification MUST include in a separate section the 1400 registration form reproduced in this section (below) to be used in 1401 registering the extension upon publication as an RFC. 1403 o IANA MUST be informed of changes to the contact information and 1404 URL for the specification. 1406 IANA will maintain a registry of allocated single-letter (singleton) 1407 subtags. This registry will use the record-jar format described by 1408 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1409 the maintaining authority defined in the RFC must forward this 1410 registration form to iesg@ietf.org, who will forward the request to 1411 iana@iana.org. The maintaining authority of the extension MUST 1412 maintain the accuracy of the record by sending an updated full copy 1413 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1414 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1415 'Contact_Email', 'Mailing_List', and 'URL' fields may be modified in 1416 these updates. 1418 Failure to maintain this record, the corresponding registry, or meet 1419 other conditions imposed by this section of this document may be 1420 appealed to the IESG [RFC 2028] [9] under the same rules as other 1421 IETF decisions (see [8]) and may result in the authority to maintain 1422 the extension being withdrawn or reassigned by the IESG. 1423 %% 1424 Identifier: 1425 Description: 1426 Comments: 1427 Added: 1428 RFC: 1429 Authority: 1430 Contact_Email: 1431 Mailing_List: 1432 URL: 1433 %% 1435 Figure 6: Format of Records in the Language Tag Extensions Registry 1437 'Identifier' contains the single letter subtag (singleton) assigned 1438 to the extension. The Internet-Draft submitted to define the 1439 extension should specific which letter to use, although the IESG may 1440 change the assignment when approving the RFC. 1442 'Description' contains the name and description of the extension. 1444 'Comments' is an optional field and may contain a broader description 1445 of the extension. 1447 'Added' contains the date the RFC was published in the "full-date" 1448 format specified in RFC 3339 [14]. For example: 2004-06-28 1449 represents June 28, 2004, in the Gregorian calendar. 1451 'RFC' contains the RFC number assigned to the extension. 1453 'Authority' contains the name of the maintaining authority for the 1454 extension. 1456 'Contact_Email' contains the email address used to contact the 1457 maintaining authority. 1459 'Mailing_List' contains the URL or subscription email address of the 1460 mailing list used by the maintaining authority. 1462 'URL' contains the URL of the registry for this extension. 1464 The determination of whether an Internet-Draft meets the above 1465 conditions and the decision to grant or withhold such authority rests 1466 solely with the IESG, and is subject to the normal review and appeals 1467 process associated with the RFC process. 1469 Extension authors are strongly cautioned that many (including most 1470 well-formed) processors will be unaware of any special relationships 1471 or meaning inherent in the order of extension subtags. Extension 1472 authors SHOULD avoid subtag relationships or canonicalization 1473 mechanisms that interfere with matching or with length restrictions 1474 that may exist in common protocols where the extension is used. In 1475 particular, applications may truncate the subtags in doing matching 1476 or in fitting into limited lengths, so it is RECOMMENDED that the 1477 most significant information be in the most significant (left-most) 1478 subtags, and that the specification gracefully handle truncated 1479 subtags. 1481 When a language tag is to be used in a specific, known, protocol, it 1482 is RECOMMENDED that that the language tag not contain extensions not 1483 supported by that protocol. In addition, it should be noted that 1484 some protocols may impose upper limits on the length of the strings 1485 used to store or transport the language tag. 1487 3.7 Conversion of the RFC 3066 Language Tag Registry 1489 Upon publication of this document as a BCP, the existing IANA 1490 language tag registry must be converted into the new subtag registry. 1491 This section defines the process for performing this conversion. 1493 The impact on the IANA maintainers of the registry of this conversion 1494 will be a small increase in the frequency of new entries. The 1495 initial set of records represents no impact on IANA, since the work 1496 to create it will be performed externally (as defined in this 1497 section). Future work will be limited to inserting or replacing 1498 whole records preformatted for IANA by the Language Subtag Reviewer. 1500 When this document is published, an email will be sent by the 1501 chair(s) of the LTRU working group to the LTRU and ietf-languages 1502 mail lists advising of the impending conversion of the registry. In 1503 that notice, the chair(s) will provide a URL whose referred content 1504 is the proposed IANA Language Subtag Registry following conversion. 1505 There will be a Last Call period of not less than four weeks for 1506 comments and corrections to be discussed on the 1507 ietf-languages@iana.org mail list. Changes as a result of comments 1508 will not restart the Last Call period. At the end of the period, the 1509 chair(s) will forward the URL to IANA, which will post the new 1510 registry on-line. 1512 Tags that are currently deprecated will be maintained as 1513 grandfathered entries. The record for the grandfathered entry will 1514 contain a 'Deprecated' field with the most appropriate date that can 1515 be determined for when the record was deprecated. The 'Comments' 1516 field will contain the reason for the deprecation. The 'Canonical' 1517 field will contain the tag that replaces the value. For example, the 1518 tag "art-lojban" is deprecated and will be placed in the 1519 grandfathered section. It's 'Deprecated' field will contain the 1520 deprecation date and 'Canonical' field the value "jbo". 1522 Tags that are not deprecated that consist entirely of subtags that 1523 are valid under this document and which have the correct form and 1524 format for tags defined by this document are superseded by this 1525 document. Such tags are placed in records of type 'redundant' in the 1526 registry. For example, "zh-Hant" is now defined by this document. 1528 Tags that are not deprecated and which contain subtags which are 1529 consistent with registration under the guidelines in this document 1530 will have a new subtag registration created for each eligible subtag. 1531 If all of the subtags in the original tag are fully defined by the 1532 resulting registrations or by this document, then the original tag is 1533 superseded by this document. Such tags are placed in the 'redundant' 1534 section of the registry. For example, "en-boont" will result in a 1535 new subtag 'boont' and the RFC 3066 registered tag "en-boont" placed 1536 in the redundant section of the registry. 1538 Tags that contain one or more subtags that do not match the valid 1539 registration pattern and which are not otherwise defined by this 1540 document will have records of type 'grandfathered' created in the 1541 registry. 1543 There will be a reasonable period in which the community may comment 1544 on the proposed list entries, which SHALL be no less than four weeks 1545 in length. At the completion of this period, the chair(s) will 1546 notify iana@iana.org and the ltru and ietf-languages mail lists that 1547 the task is complete and forward the necessary materials to IANA for 1548 publication. 1550 Registrations that are in process under the rules defined in RFC 3066 1551 MAY be completed under the former rules, at the discretion of the 1552 language tag reviewer. Any new registrations submitted after the 1553 request for conversion of the registry MUST be rejected. 1555 All existing RFC 3066 language tag registrations will be maintained 1556 in perpetuity. 1558 Users of tags that are grandfathered should consider registering 1559 appropriate subtags in the IANA subtag registry (but are not required 1560 to). 1562 Where two subtags have the same meaning, the priority of which to 1563 make canonical SHALL be the following: 1565 o As of the date of acceptance of this document as a BCP, if a code 1566 exists in the associated ISO standard and it is not deprecated or 1567 withdrawn as of that date, then it has priority. 1569 o Otherwise, the earlier-registered tag in the associated ISO 1570 standard has priority. 1572 UN numeric codes assigned to 'macro-geographical (continental)' or 1573 sub-regions not associated with an assigned ISO 3166 alpha-2 code are 1574 defined in the IANA registry and are valid for use in language tags. 1575 These codes MUST be added to the initial version of the registry. 1576 The UN numeric codes for 'economic groupings' or 'other groupings', 1577 and the alphanumeric codes in Appendix X of the UN document MUST NOT 1578 be added to the registry. 1580 When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49 1581 codes, the following criteria SHALL be applied to the inclusion, 1582 canonical mapping, and deprecation of codes: 1584 For each standard, the date of the standard referenced in RFC 1766 is 1585 selected as the starting date. Codes that were valid on that date in 1586 the selected standard are added to the registry. Codes that were 1587 previously assigned by were vacated or withdrawn before that date are 1588 not added to the registry. For each successive change to the 1589 standard, any additional assignments are added to the registry. 1590 Values that are withdrawn are marked as deprecated, but not removed. 1591 Changes in meaning or assignment of a subtag are permitted during 1592 this process (cf. 'CS'). This continues up to the date that this 1593 document was adopted. The resulting set of records is added to the 1594 registry. Future changes or additions to this portion of the 1595 registry are governed by the provisions of this document. 1597 4. Formation and Processing of Language Tags 1599 This section addresses how to use the registry with the language tag 1600 format to choose, form and process language tags. 1602 4.1 Choice of Language Tag 1604 One may occasionally be faced with several possible tags for the same 1605 body of text. 1607 Interoperability is best served when all users use the same language 1608 tag in order to represent the same language. If an application has 1609 requirements that make the rules here inapplicable, then that 1610 application risks damaging interoperability. It is strongly 1611 RECOMMENDED that users not define their own rules for language tag 1612 choice. 1614 Of particular note, many applications can benefit from the use of 1615 script subtags in language tags, as long as the use is consistent for 1616 a given context. Script subtags were not formally defined in RFC 1617 3066 and their use may affect matching and subtag identification by 1618 implementations of RFC 3066, as these subtags appear between the 1619 primary language and region subtags. For example, if a user requests 1620 content in an implementation of Section 2.5 of RFC 3066 [23] using 1621 the language range "en-US", content labeled "en-Latn-US" will not 1622 match the request. Therefore it is important to know when script 1623 subtags will customarily be used and when they should not be used. 1625 Extended language subtags (type 'extlang' in the registry, see 1626 Section 3.1) also appear between the primary language and region 1627 subtags and are reserved for future standardization. Applications 1628 may benefit from their judicious use in forming language tags in the 1629 future and similar recommendations are expected to apply to their use 1630 as apply to script subtags. 1632 Standards, protocols and applications that reference this document 1633 normatively but apply different rules to the ones given in this 1634 section MUST specify how the procedure varies from the one given 1635 here. 1637 The choice of subtags used to form a language tag should be guided by 1638 the following rules: 1640 1. Use as precise a tag as possible, but no more specific than is 1641 justified. Avoid using subtags that are not important for 1642 distinguishing content in an application. 1644 * For example, 'de' might suffice for tagging an email written 1645 in German, while "de-CH-1996" is probably unnecessarily 1646 precise for such a task. 1648 2. The script subtag SHOULD NOT be used to form language tags unless 1649 the script adds some distinguishing information to the tag. The 1650 field 'Suppress-Script' in the primary language record in the 1651 registry indicates which script subtags do not add distinguishing 1652 information for most applications. 1654 * For example, the subtag 'Latn' should not be used with the 1655 primary language 'en' because nearly all English documents are 1656 written in the Latin script and it adds no distinguishing 1657 information. However, if a document were written in English 1658 mixing Latin script with another script such as Braille 1659 ('Brai'), then it may be appropriate to choose to indicate 1660 both scripts to aid in content selection, such as the 1661 application of a stylesheet. 1663 3. If a subtag has a 'Canonical' field in its registry entry, the 1664 canonical subtag SHOULD be used to form the language tag in 1665 preference to any of its aliases. 1667 * For example, use 'he' for Hebrew in preference to 'iw'. 1669 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1670 used to label content, even if the language is unknown. Omitting 1671 the language tag altogether is preferred to using a tag with a 1672 primary language subtag of 'und'. The 'und' subtag may be useful 1673 for protocols that require a language tag to be provided. The 1674 'und' subtag may also be useful when matching language tags in 1675 certain situations. 1677 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1678 whenever the protocol allows the separate tags for multiple 1679 languages, as is the case for the Content-Language header in 1680 HTTP. The 'mul' subtag conveys little useful information: 1681 content in multiple languages should individually tag the 1682 languages where they appear or otherwise indicate the actual 1683 language in preference to the 'mul' subtag. 1685 6. The same variant subtag SHOULD NOT be used more than once within 1686 a language tag. 1688 * For example, do not use "en-GB-scouse-scouse". 1690 To ensure consistent backward compatibility, this document contains 1691 several provisions to account for potential instability in the 1692 standards used to define the subtags that make up language tags. 1693 These provisions mean that no language tag created under the rules in 1694 this document will become obsolete. In addition, tags that are in 1695 canonical form will always be in canonical form. 1697 4.2 Meaning of the Language Tag 1699 The language tag always defines a language as spoken (or written, 1700 signed or otherwise signaled) by human beings for communication of 1701 information to other human beings. Computer languages such as 1702 programming languages are explicitly excluded. 1704 If a language tag B contains language tag A as a prefix, then B is 1705 typically "narrower" or "more specific" than A. For example, "zh- 1706 Hant-TW" is more specific than "zh-Hant". 1708 This relationship is not guaranteed in all cases: specifically, 1709 languages that begin with the same sequence of subtags are NOT 1710 guaranteed to be mutually intelligible, although they may be. For 1711 example, the tag "az" shares a prefix with both "az-Latn" 1712 (Azerbaijani written using the Latin script) and "az-Cyrl" 1713 (Azerbaijani written using the Cyrillic script). A person fluent in 1714 one script may not be able to read the other, even though the text 1715 might be identical. Content tagged as "az" most probably is written 1716 in just one script and thus might not be intelligible to a reader 1717 familiar with the other script. 1719 The relationship between the tag and the information it relates to is 1720 defined by the standard describing the context in which it appears. 1721 Accordingly, this section can only give possible examples of its 1722 usage. 1724 o For a single information object, the associated language tags 1725 might be interpreted as the set of languages that is required for 1726 a complete comprehension of the complete object. Example: Plain 1727 text documents. 1729 o For an aggregation of information objects, the associated language 1730 tags could be taken as the set of languages used inside components 1731 of that aggregation. Examples: Document stores and libraries. 1733 o For information objects whose purpose is to provide alternatives, 1734 the associated language tags could be regarded as a hint that the 1735 content is provided in several languages, and that one has to 1736 inspect each of the alternatives in order to find its language or 1737 languages. In this case, the presence of multiple tags might not 1738 mean that one needs to be multi-lingual to get complete 1739 understanding of the document. Example: MIME multipart/ 1740 alternative. 1742 o In markup languages, such as HTML and XML, language information 1743 can be added to each part of the document identified by the markup 1744 structure (including the whole document itself). For example, one 1745 could write C'est la vie. inside a 1746 Norwegian document; the Norwegian-speaking user could then access 1747 a French-Norwegian dictionary to find out what the marked section 1748 meant. If the user were listening to that document through a 1749 speech synthesis interface, this formation could be used to signal 1750 the synthesizer to appropriately apply French text-to-speech 1751 pronunciation rules to that span of text, instead of applying the 1752 inappropriate Norwegian rules. 1754 4.3 Canonicalization of Language Tags 1756 Since a particular language tag may be used in many processes, 1757 language tags SHOULD always be created or generated in a canonical 1758 form. 1760 A language tag is in canonical form when: 1762 1. The tag is well-formed according the rules in Section 2.1 and 1763 Section 2.2. 1765 2. None of the subtags in the language tag has a canonical_value 1766 mapping in the IANA registry (see Section 3.1). Subtags with a 1767 canonical_value mapping MUST be replaced with their mapping in 1768 order to canonicalize the tag. 1770 3. If more than one extension subtag sequence exists, the extension 1771 sequences are ordered into case-insensitive ASCII order by 1772 singleton subtag. 1774 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1775 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1776 canonical form. 1778 Example: The language tag "en-NH" (English as used in the New 1779 Hebrides) is not canonical because the 'NH' subtag has a canonical 1780 mapping to 'VU' (Vanuatu). 1782 Note: Canonicalization of language tags does not imply anything about 1783 the use of upper or lowercase letter in subtags as described in 1784 Section 2.1. All comparisons MUST be performed in a case-insensitive 1785 manner. 1787 Note: if the field 'Deprecated' appears in a registry record without 1788 an accompanying 'Canonical' field, then that tag or subtag is 1789 deprecated without a replacement. Validating processors SHOULD NOT 1790 generate tags that include these values, although the values are 1791 canonical when they appear in a language tag. 1793 An extension MUST define any relationships that may exist between the 1794 various subtags in the extension and thus MAY define an alternate 1795 canonicalization scheme for the extension's subtags. Extensions MAY 1796 define how the order of the extension's subtags are interpreted. For 1797 example, an extension could define that its subtags are in canonical 1798 order when the subtags are placed into ASCII order: that is, "en-a- 1799 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1800 define that the order of the subtags influences their semantic 1801 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1802 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1803 so that they are tolerant of the typical processes described in 1804 Section 3.6. 1806 4.4 Considerations for Private Use Subtags 1808 Private-use subtags require private agreement between the parties 1809 that intend to use or exchange language tags that use them and great 1810 caution should be used in employing them in content or protocols 1811 intended for general use. Private-use subtags are simply useless for 1812 information exchange without prior arrangement. 1814 The value and semantic meaning of private-use tags and of the subtags 1815 used within such a language tag are not defined by this document. 1817 The use of subtags defined in the IANA registry as having a specific 1818 private use meaning convey more information that a purely private use 1819 tag prefixed by the singleton subtag 'x'. For applications this 1820 additional information may be useful. 1822 For example, the region subtags 'AA', 'ZZ' and in the ranges 1823 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) may 1824 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 1825 great deal of public, interchangeable information about the language 1826 material (that it is Chinese in the simplified Chinese script and is 1827 suitable for some geographic region 'XQ'). While the precise 1828 geographic region is not known outside of private agreement, the tag 1829 conveys far more information than an opaque tag such as "x-someLang", 1830 which contains no information about the language subtag or script 1831 subtag outside of the private agreement. 1833 However, in some cases content tagged with private use subtags may 1834 interact with other systems in a different and possibly unsuitable 1835 manner compared to tags that use opaque, privately defined subtags, 1836 so the choice of the best approach may depend on the particular 1837 domain in question. 1839 5. IANA Considerations 1841 This section deals with the processes and requirements necessary for 1842 IANA to undertake to maintain the rsubtag and extension registries as 1843 defined by this document and in accordance with the requirements of 1844 RFC 2434 [11]. 1846 The impact on the IANA maintainers of the two registries defined by 1847 this document will be a small increase in the frequency of new 1848 entries or updates. 1850 Upon adoption of this document, the process described in Section 3.7 1851 will be used to generate the initial Language Subtag Registry. The 1852 initial set of records represents no impact on IANA, since the work 1853 to create it will be performed externally (as defined in that 1854 section). The new registry will be listed under "Language Tags" at 1855 . The existing directory of 1856 registration forms and RFC 3066 registrations will be relabeled as 1857 "Language Tags (Obsolete)" and maintained (but not added to or 1858 modified). 1860 Future work on the Language Subtag Registry will be limited to 1861 inserting or replacing whole records preformatted for IANA by the 1862 Language Subtag Reviewer as described in Section 3.2 of this 1863 document. Each record will be sent to iana@iana.org with a subject 1864 line indicating whether the enclosed record is an insertion (of a new 1865 record) or a replacment of an existing record which has a Type and 1866 Subtag (or Tag) field that exactly matches the record sent. Records 1867 cannot be deleted from the registry. 1869 The Language Tag Extensions registry will also be generated and sent 1870 to IANA as described in Section 3.6. This registry may contain at 1871 most 25 records and thus changes to this registry are expected to be 1872 very infrequent. 1874 Future work by IANA on the Language Tag Extensions Registry is 1875 limited to two cases. First, the IESG may request that new records 1876 be inserted into this registry from time to time. These requests 1877 will include the record to insert in the exact format described in 1878 Section 3.6. In addition, there may be occasional requests from the 1879 maintaining authority for a specific extension to update the contact 1880 information or URLs in the record. These requests MUST include the 1881 complete, updated record. IANA is not responsible for validating the 1882 information provided, only that it is properly formatted. It should 1883 reasonably be seen to come from the maintaining authority named in 1884 the record present in the registry. 1886 6. Security Considerations 1888 The only security issue that has been raised with language tags since 1889 the publication of RFC 1766 [21], which stated that "Security issues 1890 are believed to be irrelevant to this memo", is a concern with 1891 language identifiers used in content negotiation - that they may be 1892 used to infer the nationality of the sender, and thus identify 1893 potential targets for surveillance. 1895 This is a special case of the general problem that anything sent is 1896 visible to the receiving party and possibly to third parties as well. 1897 It is useful to be aware that such concerns can exist in some cases. 1899 The evaluation of the exact magnitude of the threat, and any possible 1900 countermeasures, is left to each application protocol (see BCP 72, 1901 RFC 3552 [15] for best current practice guidance on security threats 1902 and defenses). 1904 Although the specification of valid subtags for an extension MUST be 1905 available over the Internet, implementations SHOULD NOT mechanically 1906 depend on it being always accessible, to prevent denial-of-service 1907 attacks. 1909 7. Character Set Considerations 1911 The syntax in this document requires that language tags use only the 1912 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 1913 character sets, so the composition of language tags should not have 1914 any character set issues. 1916 Rendering of characters based on the content of a language tag is not 1917 addressed in this memo. Historically, some languages have relied on 1918 the use of specific character sets or other information in order to 1919 infer how a specific character should be rendered (notably this 1920 applies to language and culture specific variations of Han ideographs 1921 as used in Japanese, Chinese, and Korean). When language tags are 1922 applied to spans of text, rendering engines may use that information 1923 in deciding which font to use in the absence of other information, 1924 particularly where languages with distinct writing traditions use the 1925 same characters. 1927 8. Changes from RFC 3066 1929 The main goals for this revision of language tags were the following: 1931 *Compatibility.* All valid RFC 3066 language tags (including those 1932 in the IANA registry) remain valid in this specification. Thus 1933 there is complete backward compatibility of this specification with 1934 existing content. In addition, this document defines language tags 1935 in such as way as to ensure future compatibility, and processors 1936 based solely on the RFC 3066 ABNF (such as those described in XML 1937 Schema version 1.0 [19]) will be able to process tags described by 1938 this document. 1940 *Stability.* Because of the changes in underlying ISO standards, a 1941 valid RFC 3066 language tag may become invalid (or have its meaning 1942 change) at a later date. With so much of the world's computing 1943 infrastructure dependent on language tags, this is simply 1944 unacceptable: it invalidates content that may have an extensive 1945 shelf-life. In this specification, once a language tag is valid, it 1946 remains valid forever. Previously, there was no way to determine 1947 when two tags were equivalent. This specification provides a stable 1948 mechanism for doing so, through the use of canonical forms. These 1949 are also stable, so that implementations can depend on the use of 1950 canonical forms to assess equivalency. 1952 *Validity.* The structure of language tags defined by this document 1953 makes it possible to determine if a particular tag is well-formed 1954 without regard for the actual content or "meaning" of the tag as a 1955 whole. This is important because the registry and underlying 1956 standards change over time. In addition, it must be possible to 1957 determine if a tag is valid (or not) for a given point in time in 1958 order to provide reproducible, testable results. This process must 1959 not be error-prone; otherwise even intelligent people will generate 1960 implementations that give different results. This specification 1961 provides for that by having a single data file, with specific 1962 versioning information, so that the validity of language tags at any 1963 point in time can be precisely determined (instead of interpolating 1964 values from many separate sources). 1966 *Extensibility.* It is important to be able to differentiate between 1967 written forms of language -- for many implementations this is more 1968 important than distinguishing between spoken variants of a language. 1969 Languages are written in a wide variety of different scripts, so this 1970 document provides for the generative use of ISO 15924 script codes. 1971 Like the generative use of ISO language and country codes in RFC 1972 3066, this allows combinations to be produced without resorting to 1973 the registration process. The addition of UN codes provides for the 1974 generation of language tags with regional scope, which is also 1975 required for information technology. 1977 The recast of the registry from containing whole language tags to 1978 subtags is a key part of this. An important feature of RFC 3066 was 1979 that it allowed generative use of subtags. This allows people to 1980 meaningfully use generated tags, without the delays in registering 1981 whole tags, and the burden on the registry of having to supply all of 1982 the combinations that people may find useful. 1984 Because of the widespread use of language tags, it is potentially 1985 disruptive to have periodic revisions of the core specification, 1986 despite demonstrated need. The extension mechanism provides for a 1987 way for independent RFCs to define extensions to language tags. 1988 These extensions have a very constrained, well-defined structure to 1989 prevent extensions from interfering with implementations of language 1990 tags defined in this document. The document also anticipates 1991 features of ISO 639-3 with the addition of the extended language 1992 subtags, as well as the possibility of other ISO 639 parts becoming 1993 useful for the formation of language tags in the future. The use and 1994 definition of private use tags has also been modified, to allow 1995 people to move as much information as possible out of private use 1996 tags, and into the regular structure. The goal is to dramatically 1997 reduce the need to produce a revision of this document in the future. 1999 The specific changes in this document to meet these goals are: 2001 o Defines the ABNF and rules for subtags so that the category of all 2002 subtags can be determined without reference to the registry. 2004 o Adds the concept of well-formed vs. validating processors, 2005 defining the rules by which an implementation can claim to be one 2006 or the other. 2008 o Replaces the IANA language tag registry with a language subtag 2009 registry that provides a complete list of valid subtags in the 2010 IANA registry. This allows for robust implementation and ease of 2011 maintenance. The language subtag registry becomes the canonical 2012 source for forming language tags. 2014 o Provides a process that guarantees stability of language tags, by 2015 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2016 the event that they register a previously used value for a new 2017 purpose. 2019 o Allows ISO 15924 script code subtags and allows them to be used 2020 generatively. Adds the concept of a variant subtag and allows 2021 variants to be used generatively. Adds the ability to use a class 2022 of UN tags as regions. 2024 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2025 as the mechanism for creating private-use language, script, and 2026 region subtags respectively. 2028 o Adds a well-defined extension mechanism. 2030 o Defines an extended language subtag, possibly for use with certain 2031 anticipated features of ISO 639-3. 2033 Ed Note: The following items are provided for the convenience of 2034 reviewers and will be removed from the final document. 2036 Changes between draft-ietf-ltru-registry-00 and this version are: 2038 o Updated the ABNF for singleton to make it conform to RFC 2234 and 2039 pass the Fenner parser (F.Ellermann) 2041 o Split the references into informative and normative lists. 2042 Eliminated dead references carried forward from previous versions 2043 of this document. (A.Phillips) 2045 o Added a reference to RFC 3552 (BCP 72) to the Security 2046 Considerations section (I.McDonald) 2048 o Modified the first sentence in Section 2.1.1 from "on the number 2049 of size of subtags in a Language Tag" to be proper English and 2050 convey more meaning. (A.Phillips) 2052 o Various examples that used the variant 'boont' were changes to use 2053 the variant 'scouse' instead. (J.Cowan) 2055 o Added an additional example ("en-a-bbb-x-a-ccc") to the extension/ 2056 singleton rules in Section 2.2.6 to illustrate that singletons can 2057 recur in private use sequences (A.Phillips) 2059 o Modified the sentence describing the possibilities for variant 2060 registration (see Section 3.5) to include transliterations and 2061 other transformations per discussion on the list. (M.T. Carrasco 2062 Benitez) 2064 o Converted the format of the registry to record-jar format. This 2065 subtantially replaces section 3.1 (R.Presuhn) 2067 o Subtantially revised the rules for registry creation to reflect 2068 the Date A/B boundaries on adopting ISO 3166 codes (J.Cowan) 2070 o Modified the registration process section and form to deal with 2071 both new additions and revisions of records, as well as making 2072 life easier on the Subtag Reviewer by matching the fields to the 2073 registry format. (A.Phillips) 2075 o Changed the reference to RFC 2234 to RFC 2234bis (recently 2076 adopted). (S.Hollenbeck) 2078 o Modifications to make this document conformant with RFC 3978 2079 (recently adopted). (R.Presuhn) 2081 o Added an informative reference to XML Schema 1.0 Part 2: Second 2082 Edition in this section. (J.Morfin) 2084 o Expanded the jargon-ish 'extlang' to "extended language" in this 2085 section. (J.Morfin) 2087 o Corrected an egregious error in the ABNF (%x6A -> %x5A in one of 2088 the ranges) (A.Phillips) 2090 o Split Maintenance of the Registry from Format of the Registry 2091 (A.Phillips) 2093 o Revision of section Section 3.4 to make it consistent with the new 2094 section Section 3.2. (A.Phillips) 2096 o Separated IANA Considerations section from the registry definition 2097 and registration procedures. () 2099 o Added additional choice information dealing with scripts and 2100 extlangs. These items were also moved to a new section following 2101 the registry format because of interdependence. 2103 o Updated the IANA Considerations section. 2105 o Added appeal and maintenance requirements to the extensions 2106 Section 3.6 section. (A.Phillips) 2108 o Added an additional bullet point to Section 3.5 enumerating the 2109 changes that can be registered to a record (previously we only 2110 listed the options for new subtags). (A.Phillips) 2112 o Added the phrase ", as well as the possibility of other ISO 639 2113 parts becoming useful for the formation of language tags in the 2114 future" to this section in anticipation of revising the ABNF to 2115 allow for the possibility of ISO 639-6 being used in language tags 2116 in a future revision of this document. (D.Garside) 2118 o Added the concept of 'Suppress-Script' to Section 4.1, as well as 2119 to the registry format in Section 3.1, Section 3.3 and 2120 Section 3.2. (many) 2122 o Added text requiring the I-D that defines an extension to choose a 2123 letter (and allowing the IESG to change it if necessary). 2124 (D.Ewell?) 2126 o Removed the ABNF notes from the text about case insensitivity 2127 (F.Ellermann) 2129 o Removed the second, rather repetitive reference to Appendix B in 2130 Section 2.1 (A.Phillips) 2132 o Fixed missing whitesapce in Section 2.1 (F.Ellermann) 2134 o Changed "empty" to "omitted" in Section 2.2.1 (F.Ellermann) 2136 o Changed the intro to Section 2.2.1 and otherwise tugged at that 2137 section to deal with i-* grandfathered items. (F.Ellermann) 2139 o Reserved alpha4 language subtags for future standardization. 2140 (D.Garside) 2142 o Incorporate changes to be consistent with RFC 3978, including the 2143 new xml2rfc processor. Note that this has an effect on the ABNF, 2144 since some of the comments were too wide previously (comments were 2145 revised to fit the 72 character maximum). (S.Hollenbeck) 2147 o Remove the Latin-1 restriction on the 'Description' field. 2148 Provide guidance for registration of content, including a 2149 requirement for at least one representation in the Latin script. 2150 (F.Ellermann, A.Phillips) 2152 o Make the variant subtlety less so. (F.Ellermann) 2154 o Various 'you' removals and cleanup (M.Davis) 2156 o Inserted additional non-normative caveat about the 'MUL' subtag 2157 (A.Phillips) 2159 o Various editorial edits (J.Cowan) 2161 o Use normative language when giving permission to not store long 2162 language tags in Section 2.1.1. (J.Cowan) 2164 9. References 2166 9.1 Normative References 2168 [1] International Organization for Standardization, "ISO 639- 2169 1:2002, Codes for the representation of names of languages -- 2170 Part 1: Alpha-2 code", ISO Standard 639, 2002. 2172 [2] International Organization for Standardization, "ISO 639-2:1998 2173 - Codes for the representation of names of languages -- Part 2: 2174 Alpha-3 code - edition 1", August 1988. 2176 [3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2177 representation of names of scripts", January 2004. 2179 [4] International Organization for Standardization, "Codes for the 2180 representation of names of countries, 3rd edition", 2181 ISO Standard 3166, August 1988. 2183 [5] Statistical Division, United Nations, "Standard Country or Area 2184 Codes for Statistical Use", UN Standard Country or Area Codes 2185 for Statistical Use, Revision 4 (United Nations publication, 2186 Sales No. 98.XVII.9, June 1999. 2188 [6] International Organization for Standardization, "ISO/IEC 10646- 2189 1:2000. Information technology -- Universal Multiple-Octet 2190 Coded Character Set (UCS) -- Part 1: Architecture and Basic 2191 Multilingual Plane and ISO/IEC 10646-2:2001. Information 2192 technology -- Universal Multiple-Octet Coded Character Set 2193 (UCS) -- Part 2: Supplementary Planes, as, from time to time, 2194 amended, replaced by a new edition or expanded by the addition 2195 of new parts", 2000. 2197 [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2198 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 (work 2199 in progress), March 2005. 2201 [8] Bradner, S., "The Internet Standards Process -- Revision 3", 2202 BCP 9, RFC 2026, October 1996. 2204 [9] Hovey, R. and S. Bradner, "The Organizations Involved in the 2205 IETF Standards Process", BCP 11, RFC 2028, October 1996. 2207 [10] Bradner, S., "Key words for use in RFCs to Indicate Requirement 2208 Levels", BCP 14, RFC 2119, March 1997. 2210 [11] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 2211 Considerations Section in RFCs", BCP 26, RFC 2434, 2212 October 1998. 2214 [12] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 10646", 2215 RFC 2781, February 2000. 2217 [13] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2218 Understanding Concerning the Technical Work of the Internet 2219 Assigned Numbers Authority", RFC 2860, June 2000. 2221 [14] Klyne, G. and C. Newman, "Date and Time on the Internet: 2222 Timestamps", RFC 3339, July 2002. 2224 [15] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on 2225 Security Considerations", BCP 72, RFC 3552, July 2003. 2227 9.2 Informative References 2229 [16] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2230 Committee: Working principles for ISO 639 maintenance", 2231 March 2000, 2232 . 2234 [17] Raymond, E., "The Art of Unix Programming", 2003. 2236 [18] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2237 02 2004. 2239 [19] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2240 Datatypes Second Edition", 10 2004, < 2241 http://www.w3.org/TR/xmlschema-2/>. 2243 [20] Unicode Consortium, "The Unicode Consortium. The Unicode 2244 Standard, Version 4.1.0, defined by: The Unicode Standard, 2245 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2246 18578-1), as amended by Unicode 4.0.1 2247 (http://www.unicode.org/versions/Unicode4.0.1) and by Unicode 2248 4.1.0 (http://www.unicode.org/versions/Unicode4.1.0).", 2249 March 2005. 2251 [21] Alvestrand, H., "Tags for the Identification of Languages", 2252 RFC 1766, March 1995. 2254 [22] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word 2255 Extensions: Character Sets, Languages, and Continuations", 2256 RFC 2231, November 1997. 2258 [23] Alvestrand, H., "Tags for the Identification of Languages", 2259 BCP 47, RFC 3066, January 2001. 2261 Authors' Addresses 2263 Addison Phillips (editor) 2264 Quest Software 2266 Email: addison.phillips@quest.com 2268 Mark Davis (editor) 2269 IBM 2271 Email: mark.davis@us.ibm.com 2273 Appendix A. Acknowledgements 2275 Any list of contributors is bound to be incomplete; please regard the 2276 following as only a selection from the group of people who have 2277 contributed to make this document what it is today. 2279 The contributors to RFC 3066 and RFC 1766, the precursors of this 2280 document, made enormous contributions directly or indirectly to this 2281 document and are generally responsible for the success of language 2282 tags. 2284 The following people (in alphabetical order) contributed to this 2285 document or to RFCs 1766 and 3066: 2287 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2288 Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco 2289 Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable, 2290 John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank 2291 Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk- 2292 Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold, 2293 Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent 2294 Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald, 2295 Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George 2296 Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto 2297 Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois 2298 Yergeau and many, many others. 2300 Very special thanks must go to Harald Tveit Alvestrand, who 2301 originated RFCs 1766 and 3066, and without whom this document would 2302 not have been possible. Special thanks must go to Michael Everson, 2303 who has served as language tag reviewer for almost the complete 2304 period since the publication of RFC 1766. Special thanks to Doug 2305 Ewell, for his production of the first complete subtag registry, and 2306 his work in producing a test parser for verifying language tags. 2308 Appendix B. Examples of Language Tags (Informative) 2310 Simple language subtag: 2312 de (German) 2314 fr (French) 2316 ja (Japanese) 2318 i-enochian (example of a grandfathered tag) 2320 Language subtag plus Script subtag: 2322 zh-Hant (Chinese written using the Traditional Chinese script) 2324 zh-Hans (Chinese written using the Simplified Chinese script) 2326 sr-Cyrl (Serbian written using the Cyrillic script) 2328 sr-Latn (Serbian written using the Latin script) 2330 Language-Script-Region: 2332 zh-Hans-CN (Chinese written using the Simlified script as used in 2333 mainland China) 2335 sr-Latn-CS (Serbian written using the Latin script as used in 2336 Serbia and Montenegro) 2338 Language-Variant: 2340 en-boont (Boontling dialect of English) 2342 en-scouse (Scouse dialect of English) 2344 Language-Region-Variant: 2346 en-GB-scouse (Scouse dialect of English as used in the UK) 2348 Language-Script-Region-Variant: 2350 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2351 Latin script as used in Italy. Note that this tag is not 2352 recommended because subtag 'sl' has a Suppress-Script value of 2353 'Latn') 2355 Language-Region: 2357 de-DE (German for Germany) 2359 en-US (English as used in the United States) 2361 es-419 (Spanish for Latin America and Caribbean region using the 2362 UN region code) 2364 Private-use subtags: 2366 de-CH-x-phonebk 2368 az-Arab-x-AZE-derbend 2370 Extended language subtags (examples ONLY: extended languages must be 2371 defined by revision or update to this document): 2373 zh-min 2375 zh-min-nan-Hant-CN 2377 Private-use registry values: 2379 x-whatever (private use using the singleton 'x') 2381 qaa-Qaaa-QM-x-southern (all private tags) 2383 de-Qaaa (German, with a private script) 2385 sr-Latn-QM (Serbian, Latin-script, private region) 2387 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2389 Tags that use extensions (examples ONLY: extensions must be defined 2390 by revision or update to this document or by RFC): 2392 en-US-u-islamCal 2394 zh-CN-a-myExt-x-private 2396 en-a-myExt-b-another 2398 Some Invalid Tags: 2400 de-419-DE (two region tags) 2401 a-DE (use of a single character subtag in primary position; note 2402 that there are a few grandfathered tags that start with "i-" that 2403 are valid) 2405 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2406 prefix) 2408 Appendix C. Example Registry 2410 Example Registry 2412 File-Date: 2005-04-18 2413 %% 2414 Type: language 2415 Subtag: aa 2416 Description: Afar 2417 Added: 2004-07-06 2418 %% 2419 Type: language 2420 Subtag: ab 2421 Description: Abkhazian 2422 Added: 2004-07-06 2423 %% 2424 Type: language 2425 Subtag: ae 2426 Description: Avestan 2427 Added: 2004-07-06 2428 %% 2429 Type: language 2430 Subtag: ar 2431 Description: Arabic 2432 Added: 2004-07-06 2433 Suppress-Script: Arab 2434 Comment: Arabic text is usually written in Arabic script 2435 %% 2436 Type: language 2437 Subtag: qaa..qtz 2438 Description: PRIVATE USE 2439 Added: 2004-08-01 2440 Comment: Use private use codes in preference 2441 to the x- singleton for primary language 2442 Comment: This is an example of two comments. 2443 %% 2444 Type: script 2445 Subtag: Arab 2446 Description: Arabic 2447 Added: 2004-07-06 2448 %% 2449 Type: script 2450 Subtag: Armn 2451 Description: Armenian 2452 Added: 2004-07-06 2453 %% 2454 Type: script 2455 Subtag: Bali 2456 Description: Balinese 2457 Added: 2004-07-06 2458 %% 2459 Type: script 2460 Subtag: Batk 2461 Description: Batak 2462 Added: 2004-07-06 2463 %% 2464 Type: region 2465 Subtag: AA 2466 Description: PRIVATE USE 2467 Added: 2004-08-01 2468 %% 2469 Type: region 2470 Subtag: AD 2471 Description: Andorra 2472 Added: 2004-07-06 2473 %% 2474 Type: region 2475 Subtag: AE 2476 Description: United Arab Emirates 2477 Added: 2004-07-06 2478 %% 2479 Type: region 2480 Subtag: AX 2481 Description: Åland Islands 2482 Added: 2004-07-06 2483 Comments: The description shows a Unicode escape 2484 for the letter A-ring. 2485 %% 2486 Type: region 2487 Subtag: 001 2488 Description: World 2489 Added: 2004-07-06 2490 %% 2491 Type: region 2492 Subtag: 002 2493 Description: Africa 2494 Added: 2004-07-06 2495 %% 2496 Type: region 2497 Subtag: 003 2498 Description: North America 2499 Added: 2004-07-06 2500 %% 2501 Type: variant 2502 Subtag: 1901 2503 Description: Traditional German 2504 orthography 2505 Added: 2004-09-09 2506 Recommended-Prefix: de 2507 Comment: 2508 %% 2509 Type: variant 2510 Subtag: 1996 2511 Description: German orthography of 1996 2512 Added: 2004-09-09 2513 Recommended-Prefix: de 2514 %% 2515 Type: variant 2516 Subtag: boont 2517 Description: Boontling 2518 Added: 2003-02-14 2519 Recommended-Prefix: en 2520 %% 2521 Type: variant 2522 Subtag: gaulish 2523 Description: Gaulish 2524 Added: 2001-05-25 2525 Recommended-Prefix: cel 2526 %% 2527 Type: grandfathered 2528 Tag: art-lojban 2529 Description: Lojban 2530 Added: 2001-11-11 2531 Canonical: jbo 2532 Deprecated: 2003-09-02 2533 %% 2534 Type: grandfathered 2535 Tag: en-GB-oed 2536 Description: English, Oxford English Dictionary spelling 2537 Added: 2003-07-09 2538 %% 2539 Type: grandfathered 2540 Tag: i-ami 2541 Description: 'Amis 2542 Added: 1999-05-25 2543 %% 2544 Type: grandfathered 2545 Tag: i-bnn 2546 Description: Bunun 2547 Added: 1999-05-25 2548 %% 2549 Type: redundant 2550 Tag: az-Arab 2551 Description: Azerbaijani in Arabic script 2552 Added: 2003-05-30 2553 %% 2554 Type: redundant 2555 Tag: az-Cyrl 2556 Description: Azerbaijani in Cyrillic script 2557 Added: 2003-05-30 2558 %% 2560 Figure 7: Example of the Registry Format 2562 Intellectual Property Statement 2564 The IETF takes no position regarding the validity or scope of any 2565 Intellectual Property Rights or other rights that might be claimed to 2566 pertain to the implementation or use of the technology described in 2567 this document or the extent to which any license under such rights 2568 might or might not be available; nor does it represent that it has 2569 made any independent effort to identify any such rights. 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