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Found 'MAY NOT' in this paragraph: Note that 'Preferred-Value' mappings in records of type 'region' MAY NOT represent exactly the same meaning as the original value. There are many reasons for a country code to be changed and the effect this has on the formation of language tags will depend on the nature of the change in question. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (June 15, 2005) is 6888 days in the past. Is this intentional? 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'1' -- Possible downref: Non-RFC (?) normative reference: ref. '2' -- Possible downref: Non-RFC (?) normative reference: ref. '3' -- Possible downref: Non-RFC (?) normative reference: ref. '4' -- Possible downref: Non-RFC (?) normative reference: ref. '5' -- Possible downref: Non-RFC (?) normative reference: ref. '6' ** Obsolete normative reference: RFC 2028 (ref. '9') (Obsoleted by RFC 9281) ** Obsolete normative reference: RFC 2434 (ref. '12') (Obsoleted by RFC 5226) ** Downref: Normative reference to an Informational RFC: RFC 2781 (ref. '13') ** Downref: Normative reference to an Informational RFC: RFC 2860 (ref. '14') -- Obsolete informational reference (is this intentional?): RFC 1766 (ref. '22') (Obsoleted by RFC 3066, RFC 3282) -- Obsolete informational reference (is this intentional?): RFC 3066 (ref. '24') (Obsoleted by RFC 4646, RFC 4647) Summary: 7 errors (**), 0 flaws (~~), 12 warnings (==), 26 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Phillips, Ed. 3 Internet-Draft Quest Software 4 Expires: December 17, 2005 M. Davis, Ed. 5 IBM 6 June 15, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-05 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on December 17, 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 . . . . . . . . 8 56 2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 9 57 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 11 58 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 12 59 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 13 60 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 14 61 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 15 62 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 17 63 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 17 64 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 17 65 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 19 66 3.1 Format of the IANA Language Subtag Registry . . . . . . . 19 67 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 24 68 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 25 69 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 29 70 3.5 Possibilities for Registration . . . . . . . . . . . . . . 32 71 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 33 72 3.7 Initialization of the Registry . . . . . . . . . . . . . . 36 73 4. Formation and Processing of Language Tags . . . . . . . . . . 39 74 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 39 75 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 41 76 4.3 Canonicalization of Language Tags . . . . . . . . . . . . 42 77 4.4 Considerations for Private Use Subtags . . . . . . . . . . 44 78 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 46 80 7. Character Set Considerations . . . . . . . . . . . . . . . . . 47 81 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 48 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51 83 9.1 Normative References . . . . . . . . . . . . . . . . . . . 51 84 9.2 Informative References . . . . . . . . . . . . . . . . . . 52 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 53 86 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54 87 B. Examples of Language Tags (Informative) . . . . . . . . . . . 55 88 C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 58 89 Intellectual Property and Copyright Statements . . . . . . . . 62 91 1. Introduction 93 Human beings on our planet have, past and present, used a number of 94 languages. There are many reasons why one would want to identify the 95 language used when presenting or requesting information. 97 Information about a user's language preferences commonly needs to be 98 identified so that appropriate processing can be applied. For 99 example, the user's language preferences in a browser can be used to 100 select web pages appropriately. A choice of language preference can 101 also be used to select among tools (such as dictionaries) to assist 102 in the processing or understanding of content in different languages. 104 In addition, knowledge about the particular language used by some 105 piece of information content might 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 [11]. 135 2. The Language Tag 137 2.1 Syntax 139 The language tag is composed of one or more parts: A primary language 140 subtag and a (possibly empty) series of subsequent subtags. Subtags 141 are distinguished by their length, position in the subtag sequence, 142 and content, so that each type of subtag can be recognized solely by 143 these features. This makes it possible to construct a parser that 144 can extract and assign some semantic information to the subtags, even 145 if specific subtag values are not recognized. Thus a parser need not 146 have an up-to-date copy of the registered subtag values to perform 147 most searching and matching operations. 149 The syntax of this tag in ABNF [7] is: 151 Language-Tag = (lang 152 *3("-" extlang) 153 ["-" script] 154 ["-" region] 155 *("-" variant) 156 *("-" extension) 157 ["-" privateuse]) 158 / privateuse ; private-use tag 159 / grandfathered ; grandfathered registrations 161 lang = 2*4ALPHA ; shortest ISO 639 code 162 / registered-lang 163 extlang = 3ALPHA ; reserved for future use 164 script = 4ALPHA ; ISO 15924 code 165 region = 2ALPHA ; ISO 3166 code 166 / 3DIGIT ; UN country number 167 variant = 5*8alphanum ; registered variants 168 / ( DIGIT 3alphanum ) 169 extension = singleton 1*("-" (2*8alphanum)) 170 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 171 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 172 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 173 ; Single letters: x/X is reserved for private use 174 registered-lang = 4*8ALPHA ; registered language subtag 175 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 176 ; grandfathered registration 177 ; Note: i is the only singleton 178 ; that starts a grandfathered tag 179 alphanum = (ALPHA / DIGIT) ; letters and numbers 181 Figure 1: Language Tag ABNF 183 The character "-" is HYPHEN-MINUS (ABNF: %x2D). All subtags have a 184 maximum length of eight characters. Note that there is a subtlety in 185 the ABNF for 'variant': variants starting with a digit MAY be four 186 characters long, while those starting with a letter MUST be at least 187 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 [13] encoding of Unicode [21]. 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 MUST not be taken to 202 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 RFC 3066 [24] did not provide an upper limit on the size of language 226 tags. While RFC 3066 did define the semantics of particular subtags 227 in such a way that most language tags consisted of language and 228 region subtags with a combined total length of up to six characters, 229 larger registered tags were not only possible but were actually 230 registered. 232 Neither this document nor the syntax in the ANBF imposes a fixed 233 upper limit on the number of subtags in a language tag (and thus an 234 upper bound on the size of a tag). The syntax in this document 235 suggests that, depending on the specific language, more subtags (and 236 thus characters) are sometimes necessary to form a complete tag; thus 237 it is possible to envision long or complex subtag sequences. 239 Some applications and protocols are forced to allocate fixed buffer 240 sizes or otherwise limit the length of a language tag in a particular 241 application. A conformant implementation or specification MAY refuse 242 to support the storage of language tags which exceed a specified 243 length. Any such limitation SHOULD be clearly documented, and such 244 documentation SHOULD include the disposition of any longer tags (for 245 example, whether an error value is generated or the language tag is 246 truncated). 248 In practice, most tags do not require additional subtags or 249 substantially more characters. Additional subtags sometimes add 250 useful distinguishing information, but extraneous subtags interfere 251 with the meaning, understanding, and processing of language tags. 252 Since language tags MAY be truncated by an application or protocol 253 that limits tag sizes, when choosing language tags users and 254 applications SHOULD avoid adding subtags that add no distinguishing 255 value. In particular, users and implementations SHOULD follow the 256 'Prefix' and 'Suppress-Script' fields in the registry (defined in 257 Section 3.1): these fields provide guidance on when specific 258 additional subtags SHOULD (and SHOULD NOT) be used in a language tag. 259 (For more information on selecting subtags, see Section 4.1.) 261 Implementations MUST support a limit of at least 33 characters. This 262 limit includes at least one subtag of each non-extension, non-private 263 use type. When choosing a buffer limit, a length of at least 42 264 characters is strongly RECOMMENDED. 266 If truncation is permitted it MUST NOT permit a subtag to be divided 267 or the formation of invalid tags (for example, one ending with the 268 "-" character). A protocol that allows tags to be truncated at an 269 arbitrary limit, without giving any indication of what that limit is, 270 has the potential for causing harm by changing the meaning of tags in 271 substantial ways. 273 Some specifications are space constrained but do not have a fixed 274 length limitation. For example, see [RFC 2231] [23]. This protocol 275 has no explicit length limitation: the length of the language tag in 276 this document is limited by the length of other header components 277 (such as the charset's name) coupled with the 76 character limit in 278 [RFC 2047] [10]. Thus the "limit" might be 50 or more characters, 279 but it could potentially be quite small. In these cases, 280 implementations SHOULD use the longest possible language tag. 281 Warning the user of truncation, if necessary, is RECOMMENDED, as 282 truncation can change the semantic meaning of the tag. 284 The following illustration shows how the 42-character recommendation 285 was derived. The combination of language and extended language 286 subtags was chosen for future compatibility. At up to 11 characters, 287 this combination is longer than the longest possible language subtag 288 (8 characters): 290 language = 3 (ISO 639-2; ISO 639-1 requires 2) 291 extlang1 = 4 (each subsequent subtag includes '-') 292 extlang2 = 4 (unlikely: needs prefix="language-extlang1") 293 extlang3 = 4 (extremely unlikely) 294 script = 5 (if not suppressed: see Section 4.1) 295 region = 4 (UN M.49; ISO 3166 requires 3) 296 variant1 = 9 (MUST have language as a prefix) 297 variant2 = 9 (MUST have language-variant1 as a prefix) 299 total = 42 characters 301 Figure 2: Derivation of the Limit on Tag Length 303 Applications or protocols which have to truncate a tag MUST do so by 304 progressively removing subtags along with their preceding "-" from 305 the right side of the language tag until the tag is short enough for 306 the given buffer. If the resulting tag ends with a single-character 307 subtag, that subtag and its preceding "-" MUST also be removed. For 308 example: 310 Tag to truncate: zh-Hant-CN-variant1-a-extend1-x-wadegile-private1 311 1. zh-Hant-CN-variant1-a-extend1-x-wadegile 312 2. zh-Hant-CN-variant1-a-extend1 313 3. zh-Hant-CN-variant1 314 4. zh-Hant-CN 315 5. zh-Hant 316 6. zh 318 Figure 3: Example of Tag Truncation 320 2.2 Language Subtag Sources and Interpretation 322 The namespace of language tags and their subtags is administered by 323 the Internet Assigned Numbers Authority (IANA) [14] according to the 324 rules in Section 5 of this document. The registry maintained by IANA 325 is the source for valid subtags: other standards referenced in this 326 section provide the source material for that registry. 328 Terminology in this section: 330 o Tag or tags refers to a complete language tag, such as 331 "fr-Latn-CA". Examples of tags in this document are enclosed in 332 double-quotes ("en-US"). 334 o Subtag refers to a specific section of a tag, delimited by hyphen, 335 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 336 this document are enclosed in single quotes ('Latn'). 338 o Code or codes refers to values defined in external standards (and 339 which are used as subtags in this document). For example, 'Latn' 340 is an [ISO 15924] [3] script code which was used to define the 341 'Latn' script subtag for use in a language tag. Examples of codes 342 in this document are enclosed in single quotes ('en', 'Latn'). 344 The definitions in this section apply to the various subtags within 345 the language tags defined by this document, excepting those 346 "grandfathered" tags defined in Section 2.2.8. 348 Language tags are designed so that each subtag type has unique length 349 and content restrictions. These make identification of the subtag's 350 type possible, even if the content of the subtag itself is 351 unrecognized. This allows tags to be parsed and processed without 352 reference to the latest version of the underlying standards or the 353 IANA registry and makes the associated exception handling when 354 parsing tags simpler. 356 Subtags in the IANA registry that do not come from an underlying 357 standard can only appear in specific positions in a tag. 358 Specifically, they can only occur as primary language subtags or as 359 variant subtags. 361 Note that sequences of private-use and extension subtags MUST occur 362 at the end of the sequence of subtags and MUST NOT be interspersed 363 with subtags defined elsewhere in this document. 365 Single letter and digit subtags are reserved for current or future 366 use. These include the following current uses: 368 o The single letter subtag 'x' is reserved to introduce a sequence 369 of private-use subtags. The interpretation of any private-use 370 subtags is defined solely by private agreement and is not defined 371 by the rules in this section or in any standard or registry 372 defined in this document. 374 o All other single letter subtags are reserved to introduce 375 standardized extension subtag sequences as described in 376 Section 3.6. 378 The single letter subtag 'i' is used by some grandfathered tags, such 379 as "i-enochian", where it always appears in the first position and 380 cannot be confused with an extension. 382 2.2.1 Primary Language Subtag 384 The primary language subtag is the first subtag in a language tag 385 (with the exception of private-use and certain grandfathered tags) 386 and cannot be omitted. The following rules apply to the primary 387 language subtag: 389 1. All two character language subtags were defined in the IANA 390 registry according to the assignments found in the standard ISO 391 639 Part 1, "ISO 639-1:2002, Codes for the representation of 392 names of languages -- Part 1: Alpha-2 code" [ISO 639-1] [1], or 393 using assignments subsequently made by the ISO 639 Part 1 394 maintenance agency or governing standardization bodies. 396 2. All three character language subtags were defined in the IANA 397 registry according to the assignments found in ISO 639 Part 2, 398 "ISO 639-2:1998 - Codes for the representation of names of 399 languages -- Part 2: Alpha-3 code - edition 1" [ISO 639-2] [2], 400 or assignments subsequently made by the ISO 639 Part 2 401 maintenance agency or governing standardization bodies. 403 3. The subtags in the range 'qaa' through 'qtz' are reserved for 404 private use in language tags. These subtags correspond to codes 405 reserved by ISO 639-2 for private use. These codes MAY be used 406 for non-registered primary-language subtags (instead of using 407 private-use subtags following 'x-'). Please refer to Section 4.4 408 for more information on private use subtags. 410 4. All four character language subtags are reserved for possible 411 future standardization. 413 5. All language subtags of 5 to 8 characters in length in the IANA 414 registry were defined via the registration process in Section 3.4 415 and MAY be used to form the primary language subtag. At the time 416 this document was created, there were no examples of this kind of 417 subtag and future registrations of this type will be discouraged: 418 primary languages are strongly RECOMMENDED for registration with 419 ISO 639 and proposals rejected by ISO 639/RA will be closely 420 scrutinized before they are registered with IANA. 422 6. The single character subtag 'x' as the primary subtag indicates 423 that the language tag consists solely of subtags whose meaning is 424 defined by private agreement. For example, in the tag "x-fr-CH", 425 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 426 French language or the country of Switzerland (or any other value 427 in the IANA registry) unless there is a private agreement in 428 place to do so. See Section 4.4. 430 7. The single character subtag 'i' is used by some grandfathered 431 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 432 grandfathered tags have a primary language subtag in their first 433 position) 435 8. Other values MUST NOT be assigned to the primary subtag except by 436 revision or update of this document. 438 Note: For languages that have both an ISO 639-1 two character code 439 and an ISO 639-2 three character code, only the ISO 639-1 two 440 character code is defined in the IANA registry. 442 Note: For languages that have no ISO 639-1 two character code and for 443 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 444 (Bibliographic) codes differ, only the Terminology code is defined in 445 the IANA registry. At the time this document was created, all 446 languages that had both kinds of three character code were also 447 assigned a two character code; it is not expected that future 448 assignments of this nature will occur. 450 Note: To avoid problems with versioning and subtag choice as 451 experienced during the transition between RFC 1766 and RFC 3066, as 452 well as the canonical nature of subtags defined by this document, the 453 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 454 RA-JAC) has included the following statement in [17]: 456 "A language code already in ISO 639-2 at the point of freezing ISO 457 639-1 shall not later be added to ISO 639-1. This is to ensure 458 consistency in usage over time, since users are directed in Internet 459 applications to employ the alpha-3 code when an alpha-2 code for that 460 language is not available." 462 In order to avoid instability of the canonical form of tags, if a two 463 character code is added to ISO 639-1 for a language for which a three 464 character code was already included in ISO 639-2, the two character 465 code will not be added as a subtag in the registry. See Section 3.3. 467 For example, if some content were tagged with 'haw' (Hawaiian), which 468 currently has no two character code, the tag would not be invalidated 469 if ISO 639-1 were to assign a two character code to the Hawaiian 470 language at a later date. 472 For example, one of the grandfathered IANA registrations is 473 "i-enochian". The subtag 'enochian' could be registered in the IANA 474 registry as a primary language subtag (assuming that ISO 639 does not 475 register this language first), making tags such as "enochian-AQ" and 476 "enochian-Latn" valid. 478 2.2.2 Extended Language Subtags 480 The following rules apply to the extended language subtags: 482 1. Three letter subtags immediately following the primary subtag are 483 reserved for future standardization, anticipating work that is 484 currently under way on ISO 639. 486 2. Extended language subtags MUST follow the primary subtag and 487 precede any other subtags. 489 3. There MAY be up to three extended language subtags. 491 4. Extended language subtags will not be registered except by 492 revision of this document. 494 5. Extended language subtags MUST NOT be used to form language tags 495 except by revision of this document. 497 Extended language subtag records, once they appear in the registry, 498 MUST include exactly one 'Prefix' field indicating an appropriate 499 language subtag or sequence of subtags that MUST always appear as a 500 prefix to the extended language subtag. 502 Example: In a future revision or update of this document, the tag 503 "zh-gan" (registered under RFC 3066) might become a valid non- 504 grandfathered (that is, redundant) tag in which the subtag 'gan' 505 might represent the Chinese dialect 'Gan'. 507 2.2.3 Script Subtag 509 The following rules apply to the script subtags: 511 1. All four character subtags were defined according to ISO 15924 512 [3]--"Codes for the representation of the names of scripts": 513 alpha-4 script codes, or subsequently assigned by the ISO 15924 514 maintenance agency or governing standardization bodies, denoting 515 the script or writing system used in conjunction with this 516 language. 518 2. Script subtags MUST immediately follow the primary language 519 subtag and all extended language subtags and MUST occur before 520 any other type of subtag described below. 522 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 523 use in language tags. These subtags correspond to codes reserved 524 by ISO 15924 for private use. These codes MAY be used for non- 525 registered script values. Please refer to Section 4.4 for more 526 information on private-use subtags. 528 4. Script subtags cannot be registered using the process in 529 Section 3.4 of this document. Variant subtags MAY be considered 530 for registration for that purpose. 532 5. There MUST be at most one script subtag in a language tag and the 533 script subtag SHOULD be omitted when it adds no distinguishing 534 value to the tag or when the primary language subtag's record 535 includes a Supress-Script field listing the applicable script 536 subtag. 538 Example: "sr-Latn" represents Serbian written using the Latin script. 540 2.2.4 Region Subtag 542 The following rules apply to the region subtags: 544 1. The region subtag defines language variations used in a specific 545 region, geographic, or political area. Region subtags MUST 546 follow any language, extended language, or script subtags and 547 MUST precede all other subtags. 549 2. All two character subtags following the primary subtag were 550 defined in the IANA registry according to the assignments found 551 in ISO 3166 [4]--"Codes for the representation of names of 552 countries and their subdivisions - Part 1: Country 553 codes"--alpha-2 country codes or assignments subsequently made by 554 the ISO 3166 maintenance agency or governing standardization 555 bodies. 557 3. All three character subtags consisting of digit (numeric) 558 characters following the primary subtag were defined in the IANA 559 registry according to the assignments found in UN Standard 560 Country or Area Codes for Statistical Use [5] (UN M.49) or 561 assignments subsequently made by the governing standards body. 562 Note that not all of the UN M.49 codes are defined in the IANA 563 registry. The following rules define which codes are entered 564 into the registry as valid subtags: 566 A. UN numeric codes assigned to 'macro-geographical 567 (continental)' or sub-regions MUST be registered in the 568 registry. These codes are not associated with an assigned 569 ISO 3166 alpha-2 code and represent supra-national areas, 570 usually covering more than one nation, state, province, or 571 territory. 573 B. UN numeric codes for 'economic groupings' or 'other 574 groupings' MUST NOT be registered in the IANA registry and 575 MUST NOT be used to form language tags. 577 C. UN numeric codes for countries or areas with ambiguous ISO 578 3166 alpha-2 codes, when entered into the registry, MUST be 579 defined according to the rules in Section 3.3 and MUST be 580 used to form language tags that represent the country or 581 region for which they are defined. 583 D. UN numeric codes for countries or areas for which there is an 584 associated ISO 3166 alpha-2 code in the registry MUST NOT be 585 entered into the registry and MUST NOT be used to form 586 language tags. Note that the ISO 3166-based subtag in the 587 registry MUST actually be associated with the UN M.49 code in 588 question. 590 E. All other UN numeric codes for countries or areas which do 591 not have an associated ISO 3166 alpha-2 code MUST NOT be 592 entered into the registry and MUST NOT be used to form 593 language tags. For more information about these codes, see 594 Section 3.3. 596 4. Note: The alphanumeric codes in Appendix X of the UN document 597 MUST NOT be entered into the registry and MUST NOT be used to 598 form language tags. (At the time this document was created these 599 values match the ISO 3166 alpha-2 codes.) 601 5. There MUST be at most one region subtag in a language tag and the 602 region subtag MAY be omitted, as when it adds no distinguishing 603 value to the tag. 605 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 606 reserved for private use in language tags. These subtags 607 correspond to codes reserved by ISO 3166 for private use. These 608 codes MAY be used for private use region subtags (instead of 609 using a private-use subtag sequence). Please refer to 610 Section 4.4 for more information on private use subtags. 612 "de-CH" represents German ('de') as used in Switzerland ('CH'). 614 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 615 ('Latn') as used in Serbia and Montenegro ('CS'). 617 "es-419" represents Spanish ('es') as used in the UN-defined Latin 618 America and Caribbean region ('419'). 620 2.2.5 Variant Subtags 622 The following rules apply to the variant subtags: 624 1. Variant subtags are not associated with any external standard. 625 Variant subtags and their meanings are defined by the 626 registration process defined in Section 3.4. 628 2. Variant subtags MUST follow all of the other defined subtags, but 629 precede any extension or private-use subtag sequences. 631 3. More than one variant MAY be used to form the language tag. 633 4. Variant subtags MUST be registered with IANA according to the 634 rules in Section 3.4 of this document before being used to form 635 language tags. In order to distinguish variants from other types 636 of subtags, registrations MUST meet the following length and 637 content restrictions: 639 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 640 at least five characters long. 642 2. Variant subtags that begin with a digit (0-9) MUST be at 643 least four characters long. 645 Variant subtag records in the language subtag registry MAY include 646 one or more 'Prefix' fields, which indicates the language tag or tags 647 that would make a suitable prefix (with other subtags, as 648 appropriate) in forming a language tag with the variant. For 649 example, the subtag 'scouse' has a Prefix of "en", making it suitable 650 to form language tags such as "en-scouse" and "en-GB-scouse", but not 651 suitable for use in a tag such as "zh-scouse" or "it-GB-scouse". 653 "en-scouse" represents the Scouse dialect of English. 655 "de-CH-1996" represents German as used in Switzerland and as written 656 using the spelling reform beginning in the year 1996 C.E. 658 Most variants that share a prefix are mutually exclusive. For 659 example, the German orthographic variations '1996' and '1901' SHOULD 660 NOT be used in the same tag, as they represent the dates of different 661 spelling reforms. A variant that can meaningfully be used in 662 combination with another variant SHOULD include a 'Prefix' field in 663 its registry record that lists that other variant. For example, if 664 another German variant 'example' were created that made sense to use 665 with '1996', then 'example' should include two Prefix fields: "de" 666 and "de-1996". 668 2.2.6 Extension Subtags 670 The following rules apply to extensions: 672 1. Extension subtags are separated from the other subtags defined 673 in this document by a single-letter subtag ("singleton"). The 674 singleton MUST be one allocated to a registration authority via 675 the mechanism described in Section 3.6 and cannot be the letter 676 'x', which is reserved for private-use subtag sequences. 678 2. Note: Private-use subtag sequences starting with the singleton 679 subtag 'x' are described below. 681 3. An extension MUST follow at least a primary language subtag. 682 That is, a language tag cannot begin with an extension. 683 Extensions extend language tags, they do not override or replace 684 them. For example, "a-value" is not a well-formed language tag, 685 while "de-a-value" is. 687 4. Each singleton subtag MUST appear at most one time in each tag 688 (other than as a private-use subtag). That is, singleton 689 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 690 ccc" is invalid because the subtag 'a' appears twice. Note that 691 the tag "en-a-bbb-x-a-ccc" is valid because the second 692 appearance of the singleton 'a' is in a private use sequence. 694 5. Extension subtags MUST meet all of the requirements for the 695 content and format of subtags defined in this document. 697 6. Extension subtags MUST meet whatever requirements are set by the 698 document that defines their singleton prefix and whatever 699 requirements are provided by the maintaining authority. 701 7. Each extension subtag MUST be from two to eight characters long 702 and consist solely of letters or digits, with each subtag 703 separated by a single '-'. 705 8. Each singleton MUST be followed by at least one extension 706 subtag. For example, the tag "tlh-a-b-foo" is invalid because 707 the first singleton 'a' is followed immediately by another 708 singleton 'b'. 710 9. Extension subtags MUST follow all language, extended language, 711 script, region and variant subtags in a tag. 713 10. All subtags following the singleton and before another singleton 714 are part of the extension. Example: In the tag "fr-a-Latn", the 715 subtag 'Latn' does not represent the script subtag 'Latn' 716 defined in the IANA Language Subtag Registry. Its meaning is 717 defined by the extension 'a'. 719 11. In the event that more than one extension appears in a single 720 tag, the tag SHOULD be canonicalized as described in 721 Section 4.3. 723 For example, if the prefix singleton 'r' and the shown subtags were 724 defined, then the following tag would be a valid example: "en-Latn- 725 GB-boont-r-extended-sequence-x-private" 727 2.2.7 Private Use Subtags 729 The following rules apply to private-use subtags: 731 1. Private-use subtags are separated from the other subtags defined 732 in this document by the reserved single-character subtag 'x'. 734 2. Private-use subtags MUST follow all language, extended language, 735 script, region, variant, and extension subtags in the tag. 736 Another way of saying this is that all subtags following the 737 singleton 'x' MUST be considered private use. Example: The 738 subtag 'US' in the tag "en-x-US" is a private use subtag. 740 3. A tag MAY consist entirely of private-use subtags. 742 4. No source is defined for private use subtags. Use of private use 743 subtags is by private agreement only. 745 For example: Users who wished to utilize SIL Ethnologue for 746 identification might agree to exchange tags such as "az-Arab-x-AZE- 747 derbend". This example contains two private-use subtags. The first 748 is 'AZE' and the second is 'derbend'. 750 2.2.8 Pre-Existing RFC 3066 Registrations 752 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 753 maintain their validity. IANA will maintain these tags in the 754 registry under either the "grandfathered" or "redundant" type. For 755 more information see Section 3.7. 757 It is important to note that all language tags formed under the 758 guidelines in this document were either legal, well-formed tags or 759 could have been registered under RFC 3066. 761 2.2.9 Classes of Conformance 763 Implementations sometimes need to describe their capabilities with 764 regard to the rules and practices described in this document. There 765 are two classes of conforming implementations described by this 766 document: "well-formed" processors and "validating" processors. 768 Claims of conformance SHOULD explicitly reference one of these 769 definitions. 771 An implementation that claims to check for well-formed language tags 772 MUST: 774 o Check that the tag and all of its subtags, including extension and 775 private-use subtags, conform to the ABNF or that the tag is on the 776 list of grandfathered tags. 778 o Check that singleton subtags that identify extensions do not 779 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 780 formed. 782 Well-formed processors are strongly encouraged to implement the 783 canonicalization rules contained in Section 4.3. 785 An implementation that claims to be validating MUST: 787 o Check that the tag is well-formed. 789 o Specify the particular registry date for which the implementation 790 performs validation of subtags. 792 o Check that either the tag is a grandfathered tag, or that all 793 language, script, region, and variant subtags consist of valid 794 codes for use in language tags according to the IANA registry as 795 of the particular date specified by the implementation. 797 o Specify which, if any, extension RFCs as defined in Section 3.6 798 are supported, including version, revision, and date. 800 o For any such extensions supported, check that all subtags used in 801 that extension are valid. 803 o For variant and extended language subtags, if the registry 804 contains one or more 'Prefix' fields for that subtag, check that 805 the tag matches at least one prefix. The tag matches if all the 806 subtags in the 'Prefix' also appear in the tag. For example, the 807 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 808 the 'es' language subtag and 'CO' region subtag appear in the tag. 810 3. Registry Format and Maintenance 812 This section defines the Language Subtag Registry and the maintenance 813 and update procedures associated with it. 815 The language subtag registry will be maintained so that, except for 816 extension subtags, it is possible to validate all of the subtags that 817 appear in a language tag under the provisions of this document or its 818 revisions or successors. In addition, the meaning of the various 819 subtags will be unambiguous and stable over time. (The meaning of 820 private-use subtags, of course, is not defined by the IANA registry.) 822 The registry defined under this document contains a comprehensive 823 list of all of the subtags valid in language tags. This allows 824 implementers a straightforward and reliable way to validate language 825 tags. 827 3.1 Format of the IANA Language Subtag Registry 829 The IANA Language Subtag Registry ("the registry") will consist of a 830 text file that is machine readable in the format described in this 831 section, plus copies of the registration forms approved by the 832 Language Subtag Reviewer in accordance with the process described in 833 Section 3.4. With the exception of the registration forms for 834 grandfathered and redundant tags, no registration records will be 835 maintained for the initial set of subtags. 837 The registry will be in a modified record-jar format text file [18]. 838 Lines are limited to 72 characters, including all whitespace. 840 Records are separated by lines containing only the sequence "%%" 841 (%x25.25). 843 Each field can be viewed as a single, logical line of ASCII 844 characters, comprising a field-name and a field-body separated by a 845 COLON character (%x3A). For convenience, the field-body portion of 846 this conceptual entity can be split into a multiple-line 847 representation; this is called "folding". The format of the registry 848 is described by the following ABNF (per [7]): 850 registry = record *("%%" CRLF record) 851 record = 1*( field-name *SP ":" *SP field-body CRLF ) 852 field-name = *(ALPHA / DIGIT / "-") 853 field-body = *(ASCCHAR/LWSP) 854 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 855 UNICHAR = "&#x" 2*6HEXDIG ";" 857 The sequence '..' (%x2E.2E) in a field-body denotes a range of 858 values. Such a range represents all subtags of the same length that 859 are alphabetically within that range, including the values explicitly 860 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 862 Characters from outside the US-ASCII repertoire, as well as the 863 AMPERSAND character ("&", %x26) when it occurs in a field-body are 864 represented by a "Numeric Character Reference" using hexadecimal 865 notation in the style used by XML 1.0 [19] (see 866 ). This consists of the 867 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 868 of the character's code point in ISO/IEC 10646 [6] followed by a 869 closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would 870 be represented by the sequence "€". Note that the hexadecimal 871 notation MAY have between two and six digits. 873 All fields whose field-body contains a date value use the "full-date" 874 format specified in RFC 3339 [15]. For example: "2004-06-28" 875 represents June 28, 2004 in the Gregorian calendar. 877 The first record in the file contains the single field whose field- 878 name is "File-Date". The field-body of this record contains the last 879 modification date of this copy of the registry, making it possible to 880 compare different versions of the registry. The registry on the IANA 881 website is the most current. Versions with an older date than that 882 one are not up-to-date. 884 File-Date: 2004-06-28 885 %% 887 Subsequent records represent subtags in the registry. Each of the 888 fields in each record MUST occur no more than once, unless otherwise 889 noted below. Each record MUST contain the following fields: 891 o 'Type' 893 * Type's field-value MUST consist of one of the following 894 strings: "language", "extlang", "script", "region", "variant", 895 "grandfathered", and "redundant" and denotes the type of tag or 896 subtag. 898 o Either 'Subtag' or 'Tag' 900 * Subtag's field-value contains the subtag being defined. This 901 field MUST only appear in records of whose Type has one of 902 these values: "language", "extlang", "script", "region", or 903 "variant". 905 * Tag's field-value contains a complete language tag. This field 906 MUST only appear in records whose Type has one of these values: 907 "grandfathered" or "redundant". 909 o Description 911 * Description's field-value contains a non-normative description 912 of the subtag or tag. 914 o Added 916 * Added's field-value contains the date the record was added to 917 the registry. 919 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 920 subtag or tag, with two exceptions. Subtags whose 'Type' field is 921 'script' (in other words, subtags defined by ISO 15924) MUST use 922 titlecase. Subtags whose 'Type' field is 'region' (in other words, 923 subtags defined by ISO 3166) MUST use uppercase. These exceptions 924 mirror the use of case in the underlying standards. 926 The field 'Description' MAY appear more than one time. At least one 927 of the 'Description' fields MUST contain a description of the tag 928 being registered written or transcribed into the Latin script; the 929 same or additional fields MAY also include a description in a non- 930 Latin script. The 'Description' field is used for identification 931 purposes and SHOULD NOT be taken to represent the actual native name 932 of the language or variation or to be in any particular language. 933 Most descriptions are taken directly from source standards such as 934 ISO 639 or ISO 3166. 936 Note: Descriptions in registry entries that correspond to ISO 639, 937 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 938 the meaning of that identifier as defined in the source standard at 939 the time it was added to the registry. The description does not 940 replace the content of the source standard itself. The descriptions 941 are not intended to be the English localized names for the subtags. 942 Localization or translation of language tag and subtag descriptions 943 is out of scope of this document. 945 Each record MAY also contain the following fields: 947 o Preferred-Value 949 * For fields of type 'language', 'extlang', 'script', 'region', 950 and 'variant', 'Preferred-Value' contains a subtag of the same 951 'Type' which is preferred for forming the language tag. 953 * For fields of type 'grandfathered' and 'redundant', a canonical 954 mapping to a complete language tag. 956 o Deprecated 958 * Deprecated's field-value contains the date the record was 959 deprecated. 961 o Prefix 963 * Prefix's field-value contains a language tag with which this 964 subtag MAY be used to form a new language tag, perhaps with 965 other subtags as well. This field MUST only appear in records 966 whose 'Type' field-value is 'variant' or 'extlang'. For 967 example, the 'Prefix' for the variant 'scouse' is 'en', meaning 968 that the tags "en-scouse" and "en-GB-scouse" might be 969 appropriate while the tag "is-scouse" is not. 971 o Comments 973 * Comments contains additional information about the subtag, as 974 deemed appropriate for understanding the registry and 975 implementing language tags using the subtag or tag. 977 o Suppress-Script 979 * Suppress-Script contains a script subtag that SHOULD NOT be 980 used to form language tags with the associated primary language 981 subtag. This field MUST only appear in records whose 'Type' 982 field-value is 'language'. See Section 4.1. 984 The field 'Deprecated' MAY be added to any record via the maintenance 985 process described in Section 3.2 or via the registration process 986 described in Section 3.4. Usually the addition of a 'Deprecated' 987 field is due to the action of one of the standards bodies, such as 988 ISO 3166, withdrawing a code. In some historical cases it might not 989 have been possible to reconstruct the original deprecation date. 990 For these cases, an approximate date appears in the registry. 991 Although valid in language tags, subtags and tags with a 'Deprecated' 992 field are deprecated and validating processors SHOULD NOT generate 993 these subtags. Note that a record that contains a 'Deprecated' field 994 and no corresponding 'Preferred-Value' field has no replacement 995 mapping. 997 Thie field 'Preferred-Value' contains a mapping between the record in 998 which it appears and a tag or subtag which SHOULD be preferred when 999 selected language tags. These values form three groups: 1001 ISO 639 language codes which were later withdrawn in favor of 1002 other codes. These values are mostly a historical curiosity. 1004 ISO 3166 region codes which have been withdrawn in favor of a new 1005 code. This sometimes happens when a country changes its name or 1006 administration in such a way that warrants a new region code. 1008 Tags grandfathered from RFC 3066. In many cases these tags have 1009 become obsolete because the values they represent were later 1010 encoded by ISO 639. 1012 Records that contain a 'Preferred-Value' field MUST also have a 1013 'Deprecated' field. This field contains a date of deprecation. Thus 1014 a language tag processor can use the registry to construct the valid, 1015 non-deprecated set of subtags for a given date. In addition, for any 1016 given tag, a processor can construct the set of valid language tags 1017 that correspond to that tag for all dates up to the date of the 1018 registry. The ability to do these mappings MAY be beneficial to 1019 applications that are matching, selecting, for filtering content 1020 based on its language tags. 1022 Note that 'Preferred-Value' mappings in records of type 'region' MAY 1023 NOT represent exactly the same meaning as the original value. There 1024 are many reasons for a country code to be changed and the effect this 1025 has on the formation of language tags will depend on the nature of 1026 the change in question. 1028 In particular, the 'Preferred-Value' field does not imply retagging 1029 content that uses the affected subtag. 1031 The field 'Preferred-Value' MUST NOT be modified once created in the 1032 registry. The field MAY be added to records of type "grandfathered" 1033 and "region" according to the rules in Section 3.2. Otherwise the 1034 field MUST NOT be added to any record already in the registry. 1036 The 'Preferred-Value' field in records of type "grandfathered" and 1037 "redundant" contains whole language tags that are strongly 1038 RECOMMENDED for use in place of the record's value. In many cases 1039 the mappings were created by deprecation of the tags during the 1040 period before this document was adopted. For example, the tag "no- 1041 nyn" was deprecated in favor of the ISO 639-1 defined language code 1042 'nn'. 1044 Records of type 'variant' MAY have more than one field of type 1045 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1046 record via the registration process. 1048 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 1050 The field-value of the 'Prefix' field consists of a language tag 1051 whose subtags are appropriate to use with this subtag. For example, 1052 the variant subtag 'scouse' has a Prefix field of "en". This means 1053 that tags starting with the sequence "en-" are most appropriate with 1054 this subtag, so "en-Latn-scouse" and "en-GB-scouse" are both 1055 acceptable, while the tag "fr-scouse" is an inappropriate choice. 1057 The field of type 'Prefix' MUST NOT be removed from any record. The 1058 field-value for this type of field MUST NOT be modified. 1060 The field 'Comments' MAY appear more than once per record. This 1061 field MAY be inserted or changed via the registration process and no 1062 guarantee of stability is provided. The content of this field is not 1063 restricted, except by the need to register the information, the 1064 suitability of the request, and by reasonable practical size 1065 limitations. Long screeds about a particular subtag are frowned 1066 upon. 1068 The field 'Suppress-Script' MUST only appear in records whose 'Type' 1069 field-value is 'language'. This field MAY appear at most one time in 1070 a record. This field indicates a script used to write the 1071 overwhelming majority of documents for the given language and which 1072 therefore adds no distinguishing information to a language tag. It 1073 helps ensure greater compatibility between the language tags 1074 generated according to the rules in this document and language tags 1075 and tag processors or consumers based on RFC 3066. For example, 1076 virtually all Icelandic documents are written in the Latin script, 1077 making the subtag 'Latn' redundant in the tag "is-Latn". 1079 For examples of registry entries and their format, see Appendix C. 1081 3.2 Maintenance of the Registry 1083 Maintenance of the registry requires that as codes are assigned or 1084 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1085 Subtag Reviewer will evaluate each change, determine whether it 1086 conflicts with existing registry entries, and submit the information 1087 to IANA for inclusion in the registry. If an change takes place and 1088 the Language Subtag Reviewer does not do this in a timely manner, 1089 then any interested party MAY use the procedure in Section 3.4 to 1090 register the appropriate update. 1092 Note: The redundant and grandfathered entries together are the 1093 complete list of tags registered under RFC 3066 [24]. The redundant 1094 tags are those that can now be formed using the subtags defined in 1095 the registry together with the rules of Section 2.2. The 1096 grandfathered entries are those that can never be legal under those 1097 same provisions. 1099 The set of redundant and grandfathered tags is permanent and stable: 1100 no new entries will be added and none of the entries will be removed. 1101 Records of type 'grandfathered' MAY have their type converted to 1102 'redundant': see Section 3.7 for more information. 1104 RFC 3066 tags that were deprecated prior to the adoption of this 1105 document are part of the list of grandfathered tags and their 1106 component subtags were not included as registered variants (although 1107 they remain eligible for registration). For example, the tag "art- 1108 lojban" was deprecated in favor of the language subtag 'jbo'. 1110 The Language Subtag Reviewer MUST ensure that new subtags meet the 1111 requirements in Section 4.1 or submit an appropriate alternate subtag 1112 as described in that section. If a change or addition to the 1113 registry is needed, the Language Subtag Reviewer will prepare the 1114 complete record, including all fields, and forward it to IANA for 1115 insertion into the registry. If this represents a new subtag, then 1116 the message will indicate that this represents an INSERTION of a 1117 record. If this represents a change to an existing subtag, then the 1118 message MUST indicate that this represents a MODIFICATION, as shown 1119 in the following example: 1121 LANGUAGE SUBTAG MODIFICATION 1122 File-Date: 2005-01-02 1123 %% 1124 Type: variant 1125 Subtag: nedis 1126 Description: Natisone dialect 1127 Description: Nadiza dialect 1128 Added: 2003-10-09 1129 Prefix: sl 1130 Comments: This is a comment shown 1131 as an example. 1132 %% 1134 Figure 6 1136 Whenever an entry is created or modified in the registry, the 'File- 1137 Date' record at the start of the registry is updated to reflect the 1138 most recent modification date in the RFC 3339 [15] "full-date" 1139 format. 1141 Values in the 'Subtag' field MUST be lowercase except as provided for 1142 in Section 3.1. 1144 3.3 Stability of IANA Registry Entries 1146 The stability of entries and their meaning in the registry is 1147 critical to the long term stability of language tags. The rules in 1148 this section guarantee that a specific language tag's meaning is 1149 stable over time and will not change. 1151 These rules specifically deal with how changes to codes (including 1152 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1153 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1154 Subtag Registry. Assignments to the IANA Language Subtag Registry 1155 MUST follow the following stability rules: 1157 o Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1158 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1159 guaranteed to be stable over time. 1161 o Values in the 'Description' field MUST NOT be changed in a way 1162 that would invalidate previously-existing tags. They MAY be 1163 broadened somewhat in scope, changed to add information, or 1164 adapted to the most common modern usage. For example, countries 1165 occasionally change their official names: an historical example of 1166 this would be "Upper Volta" changing to "Burkina Faso". 1168 o Values in the field 'Prefix' MAY be added to records of type 1169 'variant' via the registration process. 1171 o Values in the field 'Prefix' MAY be modified, so long as the 1172 modifications broaden the set of prefixes. That is, a prefix MAY 1173 be replaced by one of its own prefixes. For example, the prefix 1174 "en-US" could be replaced by "en", but not by the prefixes "en- 1175 Latn", "fr", or "en-US-boont". If one of those prefixes were 1176 needed, a new Prefix SHOULD be registered. 1178 o Values in the field 'Prefix' MUST NOT be removed. 1180 o The field 'Comments' MAY be added, changed, modified, or removed 1181 via the registration process or any of the processes or 1182 considerations described in this section. 1184 o The field 'Suppress-Script' MAY be added or removed via the 1185 registration process. 1187 o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1188 conflict with existing subtags of the associated type and whose 1189 meaning is not the same as an existing subtag of the same type are 1190 entered into the IANA registry as new records. 1192 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1193 withdrawn by their respective maintenance or registration 1194 authority remain valid in language tags. A 'Deprecated' field 1195 containing the date of withdrawal is added to the record. If a 1196 new record of the same type is added that represents a replacement 1197 value, then a 'Preferred-Value' field MAY also be added. The 1198 registration process MAY be used to add comments about the 1199 withdrawal of the code by the respective standard. 1201 * The region code 'TL' was assigned to the country 'Timor-Leste', 1202 replacing the code 'TP' (which was assigned to 'East Timor' 1203 when it was under administration by Portugal). The subtag 'TP' 1204 remains valid in language tags, but its record contains the a 1205 'Preferred-Value' of 'TL' and its field 'Deprecated' contains 1206 the date the new code was assigned ('2004-07-06'). 1208 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1209 with existing subtags of the associated type, including subtags 1210 that are deprecated, MUST NOT be entered into the registry. The 1211 following additional considerations apply to subtag values that 1212 are reassigned: 1214 * For ISO 639 codes, if the newly assigned code's meaning is not 1215 represented by a subtag in the IANA registry, the Language 1216 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1217 proposal for entering in the IANA registry as soon as practical 1218 a registered language subtag as an alternate value for the new 1219 code. The form of the registered language subtag will be at 1220 the discretion of the Language Subtag Reviewer and MUST conform 1221 to other restrictions on language subtags in this document. 1223 * For all subtags whose meaning is derived from an external 1224 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if a 1225 new meaning is assigned to an existing code and the new meaning 1226 broadens the meaning of that code, then the meaning for the 1227 associated subtag MAY be changed to match. The meaning of a 1228 subtag MUST NOT be narrowed, however, as this can result in an 1229 unknown proportion of the existing uses of a subtag becoming 1230 invalid. Note: ISO 639 MA/RA has adopted a similar stability 1231 policy. 1233 * For ISO 15924 codes, if the newly assigned code's meaning is 1234 not represented by a subtag in the IANA registry, the Language 1235 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1236 proposal for entering in the IANA registry as soon as practical 1237 a registered variant subtag as an alternate value for the new 1238 code. The form of the registered variant subtag will be at the 1239 discretion of the Language Subtag Reviewer and MUST conform to 1240 other restrictions on variant subtags in this document. 1242 * For ISO 3166 codes, if the newly assigned code's meaning is 1243 associated with the same UN M.49 code as another 'region' 1244 subtag, then the existing region subtag remains as the 1245 preferred value for that region and no new entry is created. A 1246 comment MAY be added to the existing region subtag indicating 1247 the relationship to the new ISO 3166 code. 1249 * For ISO 3166 codes, if the newly assigned code's meaning is 1250 associated with a UN M.49 code that is not represented by an 1251 existing region subtag, then the Language Subtag Reviewer, as 1252 described in Section 3.4, SHALL prepare a proposal for entering 1253 the appropriate UN M.49 country code as an entry in the IANA 1254 registry. 1256 * Codes assigned by UN M.49 to countries or areas (as opposed to 1257 geographical regions and sub-regions) for which there is no 1258 corresponding ISO 3166 code MUST NOT be registered, except 1259 under the previous provision. If it is necessary to identify a 1260 region for which only a UN M.49 code exists in language tags, 1261 then the registration authority for ISO 3166 SHOULD be 1262 petitioned to assign a code, which can then be registered for 1263 use in language tags. At the time this document was written, 1264 there were only four such codes: 830 (Channel Islands), 831 1265 (Guernsey), 832 (Jersey), and 833 (Isle of Man). This rule 1266 exists so that UN M.49 codes remain available as the value of 1267 last resort in cases where ISO 3166 reassigns a deprecated 1268 value in the registry. 1270 * For ISO 3166 codes, if there is no associated UN numeric code, 1271 then the Language Subtag Reviewer SHALL petition the UN to 1272 create one. If there is no response from the UN within ninety 1273 days of the request being sent, the Language Subtag Reviewer 1274 SHALL prepare a proposal for entering in the IANA registry as 1275 soon as practical a registered variant subtag as an alternate 1276 value for the new code. The form of the registered variant 1277 subtag will be at the discretion of the Language Subtag 1278 Reviewer and MUST conform to other restrictions on variant 1279 subtags in this document. This situation is very unlikely to 1280 ever occur. 1282 o Stability provisions apply to grandfathered tags with this 1283 exception: should all of the subtags in a grandfathered tag become 1284 valid subtags in the IANA registry, then the field 'Type' in that 1285 record is changed from 'grandfathered' to 'redundant'. Note that 1286 this will not affect language tags that match the grandfathered 1287 tag, since these tags will now match valid generative subtag 1288 sequences. For example, if the subtag 'gan' in the language tag 1289 "zh-gan" were to be registered as an extended language subtag, 1290 then the grandfathered tag "zh-gan" would be deprecated (but 1291 existing content or implementations that use "zh-gan" would remain 1292 valid). 1294 3.4 Registration Procedure for Subtags 1296 The procedure given here MUST be used by anyone who wants to use a 1297 subtag not currently in the IANA Language Subtag Registry. 1299 Only subtags of type 'language' and 'variant' will be considered for 1300 independent registration of new subtags. Handling of subtags needed 1301 for stability and subtags necessary to keep the registry synchronized 1302 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1303 defined by this document are described in Section 3.2. Stability 1304 provisions are described in Section 3.3. 1306 This procedure MAY also be used to register or alter the information 1307 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1308 in a subtag's record as described in Figure 9. Changes to all other 1309 fields in the IANA registry are NOT permitted. 1311 Registering a new subtag or requesting modifications to an existing 1312 tag or subtag starts with the requester filling out the registration 1313 form reproduced below. Note that each response is not limited in 1314 size so that the request can adequately describe the registration. 1315 The fields in the "Record Requested" section SHOULD follow the 1316 requirements in Section 3.1. 1318 LANGUAGE SUBTAG REGISTRATION FORM 1319 1. Name of requester: 1320 2. E-mail address of requester: 1321 3. Record Requested: 1323 Type: 1324 Subtag: 1325 Description: 1326 Prefix: 1327 Preferred-Value: 1328 Deprecated: 1329 Suppress-Script: 1330 Comments: 1332 4. Intended meaning of the subtag: 1333 5. Reference to published description 1334 of the language (book or article): 1335 6. Any other relevant information: 1337 Figure 7 1339 The subtag registration form MUST be sent to 1340 for a two week review period before it can 1341 be submitted to IANA. (This is an open list and can be joined by 1342 sending a request to .) 1344 Variant and extlang subtags are always registered for use with a 1345 particular range of language tags. For example, the subtag 'scouse' 1346 is intended for use with language tags that start with the primary 1347 language subtag "en", since Scouse is a dialect of English. Thus the 1348 subtag 'scouse' could be included in tags such as "en-Latn-scouse" or 1349 "en-GB-scouse". This information is stored in the "Prefix" field in 1350 the registry. Variant registration requests are REQUIRED to include 1351 at least one "Prefix" field in the registration form. 1353 The 'Prefix' field for a given registered subtag will be maintained 1354 in the IANA registry as a guide to usage. Additional prefixes MAY be 1355 added by filing an additional registration form. In that form, the 1356 "Any other relevant information:" field MUST indicate that it is the 1357 addition of a prefix. 1359 Requests to add a prefix to a variant subtag that imply a different 1360 semantic meaning will probably be rejected. For example, a request 1361 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1362 nedis" represented some German dialect would be rejected. The 1363 'nedis' subtag represents a particular Slovenian dialect and the 1364 additional registration would change the semantic meaning assigned to 1365 the subtag. A separate subtag SHOULD be proposed instead. 1367 The 'Description' field MUST contain a description of the tag being 1368 registered written or transcribed into the Latin script; it MAY also 1369 include a description in a non-Latin script. Non-ASCII characters 1370 MUST be escaped using the syntax described in Section 3.1. The 1371 'Description' field is used for identification purposes and doesn't 1372 necessarily represent the actual native name of the language or 1373 variation or to be in any particular language. 1375 While the 'Description' field itself is not guaranteed to be stable 1376 and errata corrections MAY be undertaken from time to time, attempts 1377 to provide translations or transcriptions of entries in the registry 1378 itself will probably be frowned upon by the community or rejected 1379 outright, as changes of this nature have an impact on the provisions 1380 in Section 3.3. 1382 The Language Subtag Reviewer is responsible for responding to 1383 requests for the registration of subtags through the registration 1384 process and is appointed by the IESG. 1386 When the two week period has passed the Language Subtag Reviewer 1387 either forwards the record to be inserted or modified to 1388 iana@iana.org according to the procedure described in Section 3.2, or 1389 rejects the request because of significant objections raised on the 1390 list or due to problems with constraints in this document (which MUST 1391 be explicitly cited). The reviewer MAY also extend the review period 1392 in two week increments to permit further discussion. The reviewer 1393 MUST indicate on the list whether the registration has been accepted, 1394 rejected, or extended following each two week period. 1396 Note that the reviewer can raise objections on the list if he or she 1397 so desires. The important thing is that the objection MUST be made 1398 publicly. 1400 The applicant is free to modify a rejected application with 1401 additional information and submit it again; this restarts the two 1402 week comment period. 1404 Decisions made by the reviewer MAY be appealed to the IESG [RFC 2028] 1405 [9] under the same rules as other IETF decisions [RFC 2026] [8]. 1407 All approved registration forms are available online in the directory 1408 http://www.iana.org/numbers.html under "languages". 1410 Updates or changes to existing records, including previous 1411 registrations, follow the same procedure as new registrations. The 1412 Language Subtag Reviewer decides whether there is consensus to update 1413 the registration following the two week review period; normally 1414 objections by the original registrant will carry extra weight in 1415 forming such a consensus. 1417 Registrations are permanent and stable. Once registered, subtags 1418 will not be removed from the registry and will remain a valid way in 1419 which to specify a specific language or variant. 1421 Note: The purpose of the "Description" in the registration form is 1422 intended as an aid to people trying to verify whether a language is 1423 registered or what language or language variation a particular subtag 1424 refers to. In most cases, reference to an authoritative grammar or 1425 dictionary of that language will be useful; in cases where no such 1426 work exists, other well known works describing that language or in 1427 that language MAY be appropriate. The subtag reviewer decides what 1428 constitutes "good enough" reference material. This requirement is 1429 not intended to exclude particular languages or dialects due to the 1430 size of the speaker population or lack of a standardized orthography. 1431 Minority languages will be considered equally on their own merits. 1433 3.5 Possibilities for Registration 1435 Possibilities for registration of subtags or information about 1436 subtags include: 1438 o Primary language subtags for languages not listed in ISO 639 that 1439 are not variants of any listed or registered language can be 1440 registered. At the time this document was created there were no 1441 examples of this form of subtag. Before attempting to register a 1442 language subtag, there MUST be an attempt to register the language 1443 with ISO 639. No language subtags will be registered for codes 1444 that exist in ISO 639-1 or ISO 639-2, which are under 1445 consideration by the ISO 639 maintenance or registration 1446 authorities, or which have never been attempted for registration 1447 with those authorities. If ISO 639 has previously rejected a 1448 language for registration, it is reasonable to assume that there 1449 must be additional very compelling evidence of need before it will 1450 be registered in the IANA registry (to the extent that it is very 1451 unlikely that any subtags will be registered of this type). 1453 o Dialect or other divisions or variations within a language, its 1454 orthography, writing system, regional or historical usage, 1455 transliteration or other transformation, or distinguishing 1456 variation MAY be registered as variant subtags. An example is the 1457 'scouse' subtag (the Scouse dialect of English). 1459 o The addition or maintenance of fields (generally of an 1460 informational nature) in Tag or Subtag records as described in 1461 Section 3.1 and subject to the stability provisions in 1462 Section 3.3. This includes descriptions; comments; deprecation 1463 and preferred values for obsolete or withdrawn codes; or the 1464 addition of script or extlang information to primary language 1465 subtags. 1467 o The addition of records and related field value changes necessary 1468 to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and 1469 UN M.49 as described in Section 3.3. 1471 This document leaves the decision on what subtags or changes to 1472 subtags are appropriate (or not) to the registration process 1473 described in Section 3.4. 1475 Note: four character primary language subtags are reserved to allow 1476 for the possibility of alpha4 codes in some future addition to the 1477 ISO 639 family of standards. 1479 ISO 639 defines a maintenance agency for additions to and changes in 1480 the list of languages in ISO 639. This agency is: 1482 International Information Centre for Terminology (Infoterm) 1483 Aichholzgasse 6/12, AT-1120 1484 Wien, Austria 1485 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1487 ISO 639-2 defines a maintenance agency for additions to and changes 1488 in the list of languages in ISO 639-2. This agency is: 1490 Library of Congress 1491 Network Development and MARC Standards Office 1492 Washington, D.C. 20540 USA 1493 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1494 URL: http://www.loc.gov/standards/iso639 1496 The maintenance agency for ISO 3166 (country codes) is: 1498 ISO 3166 Maintenance Agency 1499 c/o International Organization for Standardization 1500 Case postale 56 1501 CH-1211 Geneva 20 Switzerland 1502 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1503 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1505 The registration authority for ISO 15924 (script codes) is: 1507 Unicode Consortium Box 391476 1508 Mountain View, CA 94039-1476, USA 1509 URL: http://www.unicode.org/iso15924 1511 The Statistics Division of the United Nations Secretariat maintains 1512 the Standard Country or Area Codes for Statistical Use and can be 1513 reached at: 1515 Statistical Services Branch 1516 Statistics Division 1517 United Nations, Room DC2-1620 1518 New York, NY 10017, USA 1520 Fax: +1-212-963-0623 1521 E-mail: statistics@un.org 1522 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1524 3.6 Extensions and Extensions Namespace 1526 Extension subtags are those introduced by single-letter subtags other 1527 than 'x'. They are reserved for the generation of identifiers which 1528 contain a language component, and are compatible with applications 1529 that understand language tags. For example, they might be used to 1530 define locale identifiers, which are generally based on language. 1532 The structure and form of extensions are defined by this document so 1533 that implementations can be created that are forward compatible with 1534 applications that might be created using single-letter subtags in the 1535 future. In addition, defining a mechanism for maintaining single- 1536 letter subtags will lend to the stability of this document by 1537 reducing the likely need for future revisions or updates. 1539 Allocation of a single-letter subtag SHALL take the form of an RFC 1540 defining the name, purpose, processes, and procedures for maintaining 1541 the subtags. The maintaining or registering authority, including 1542 name, contact email, discussion list email, and URL location of the 1543 registry MUST be indicated clearly in the RFC. The RFC MUST specify 1544 or include each of the following: 1546 o The specification MUST reference the specific version or revision 1547 of this document that governs its creation and MUST reference this 1548 section of this document. 1550 o The specification and all subtags defined by the specification 1551 MUST follow the ABNF and other rules for the formation of tags and 1552 subtags as defined in this document. In particular it MUST 1553 specify that case is not significant and that subtags MUST NOT 1554 exceed eight characters in length. 1556 o The specification MUST specify a canonical representation. 1558 o The specification of valid subtags MUST be available over the 1559 Internet and at no cost. 1561 o The specification MUST be in the public domain or available via a 1562 royalty-free license acceptable to the IETF and specified in the 1563 RFC. 1565 o The specification MUST be versioned and each version of the 1566 specification MUST be numbered, dated, and stable. 1568 o The specification MUST be stable. That is, extension subtags, 1569 once defined by a specification, MUST NOT be retracted or change 1570 in meaning in any substantial way. 1572 o The specification MUST include in a separate section the 1573 registration form reproduced in this section (below) to be used in 1574 registering the extension upon publication as an RFC. 1576 o IANA MUST be informed of changes to the contact information and 1577 URL for the specification. 1579 IANA will maintain a registry of allocated single-letter (singleton) 1580 subtags. This registry will use the record-jar format described by 1581 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1582 the maintaining authority defined in the RFC MUST forward this 1583 registration form to iesg@ietf.org, who will forward the request to 1584 iana@iana.org. The maintaining authority of the extension MUST 1585 maintain the accuracy of the record by sending an updated full copy 1586 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1587 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1588 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in 1589 these updates. 1591 Failure to maintain this record, the corresponding registry, or meet 1592 other conditions imposed by this section of this document MAY be 1593 appealed to the IESG [RFC 2028] [9] under the same rules as other 1594 IETF decisions (see [8]) and MAY result in the authority to maintain 1595 the extension being withdrawn or reassigned by the IESG. 1596 %% 1597 Identifier: 1598 Description: 1599 Comments: 1600 Added: 1601 RFC: 1602 Authority: 1603 Contact_Email: 1604 Mailing_List: 1605 URL: 1606 %% 1608 Figure 8: Format of Records in the Language Tag Extensions Registry 1610 'Identifier' contains the single letter subtag (singleton) assigned 1611 to the extension. The Internet-Draft submitted to define the 1612 extension SHOULD specify which letter to use, although the IESG MAY 1613 change the assignment when approving the RFC. 1615 'Description' contains the name and description of the extension. 1617 'Comments' is an OPTIONAL field and MAY contain a broader description 1618 of the extension. 1620 'Added' contains the date the RFC was published in the "full-date" 1621 format specified in RFC 3339 [15]. For example: 2004-06-28 1622 represents June 28, 2004, in the Gregorian calendar. 1624 'RFC' contains the RFC number assigned to the extension. 1626 'Authority' contains the name of the maintaining authority for the 1627 extension. 1629 'Contact_Email' contains the email address used to contact the 1630 maintaining authority. 1632 'Mailing_List' contains the URL or subscription email address of the 1633 mailing list used by the maintaining authority. 1635 'URL' contains the URL of the registry for this extension. 1637 The determination of whether an Internet-Draft meets the above 1638 conditions and the decision to grant or withhold such authority rests 1639 solely with the IESG, and is subject to the normal review and appeals 1640 process associated with the RFC process. 1642 Extension authors are strongly cautioned that many (including most 1643 well-formed) processors will be unaware of any special relationships 1644 or meaning inherent in the order of extension subtags. Extension 1645 authors SHOULD avoid subtag relationships or canonicalization 1646 mechanisms that interfere with matching or with length restrictions 1647 that sometimes exist in common protocols where the extension is used. 1648 In particular, applications MAY truncate the subtags in doing 1649 matching or in fitting into limited lengths, so it is RECOMMENDED 1650 that the most significant information be in the most significant 1651 (left-most) subtags, and that the specification gracefully handle 1652 truncated subtags. 1654 When a language tag is to be used in a specific, known, protocol, it 1655 is RECOMMENDED that that the language tag not contain extensions not 1656 supported by that protocol. In addition, note that some protocols 1657 MAY impose upper limits on the length of the strings used to store or 1658 transport the language tag. 1660 3.7 Initialization of the Registry 1662 Upon publication of this document as a BCP, the Language Subtag 1663 Registry MUST be created and populated with the initial set of 1664 subtags. This includes converting the entries from the existing IANA 1665 language tag registry defined by RFC 3066 to the new format. This 1666 section defines the process for defining the new registry and 1667 performing the conversion of the old registry. 1669 The impact on the IANA maintainers of the registry of this conversion 1670 will be a small increase in the frequency of new entries. The 1671 initial set of records represents no impact on IANA, since the work 1672 to create it will be performed externally (as defined in this 1673 section). Future work will be limited to inserting or replacing 1674 whole records preformatted for IANA by the Language Subtag Reviewer. 1676 The initial registry will be created by the LTRU working group. 1677 Using the instructions in this document, the working group will 1678 prepare an Informational RFC by creating a series of Internet-Drafts 1679 containing the prototype registry according to the rules in Sections 1680 4.2.2 and 4.2.3 and subject to IESG review as described in Section 1681 6.1.1 of RFC 2026 [8]. 1683 When the Internet-Draft containing the prototype registry has been 1684 approved by the IESG for publication as an RFC, the document will be 1685 forwarded to IANA, which will post the contents of the new registry 1686 on-line. 1688 Tags in the RFC 3066 registry that are not deprecated that consist 1689 entirely of subtags that are valid under this document and which have 1690 the correct form and format for tags defined by this document are 1691 superseded by this document. Such tags are placed in records of type 1692 'redundant' in the registry. For example, "zh-Hant" is now defined 1693 by this document. 1695 All other tags in the RFC 3066 registry that are deprecated will be 1696 maintained as grandfathered entries. The record for the 1697 grandfathered entry will contain a 'Deprecated' field with the most 1698 appropriate date that can be determined for when the record was 1699 deprecated. The 'Comments' field will contain the reason for the 1700 deprecation. The 'Preferred-Value' field will contain the tag that 1701 replaces the value. For example, the tag "art-lojban" is deprecated 1702 and will be placed in the grandfathered section. It's 'Deprecated' 1703 field will contain the deprecation date (in this case "2003-09-02") 1704 and the 'Preferred-Value' field the value "jbo". 1706 Tags that are not deprecated and which contain subtags which are 1707 consistent with registration under the guidelines in this document 1708 will not automatically have a new subtag registration created for 1709 each eligible subtag. Interested parties MAY use the registration 1710 process in Section 3.4 to register these subtags. If all of the 1711 subtags in the original tag become fully defined by the resulting 1712 registrations, then the original tag is superseded by this document. 1713 Such tags will have their record changed from type 'grandfathered' to 1714 type 'redundant' in the registry. For example, the subtag 'boont' 1715 could be registered, resulting in the change of the grandfathered tag 1716 "en-boont" to type redundant in the registry. 1718 Tags that contain one or more subtags that do not match the valid 1719 registration pattern and which are not otherwise defined by this 1720 document will have records of type 'grandfathered' created in the 1721 registry. These records cannot become type 'redundant', but MAY have 1722 a 'Deprecated' and 'Preferred-Value' field added to them if a subtag 1723 assignment or combination of assignments renders the tag obsolete. 1725 There MUST be a reasonable period in which the community can comment 1726 on the proposed list entries, which SHALL be no less than four weeks 1727 in length. At the completion of this period, the chair(s) will 1728 notify iana@iana.org and the ltru and ietf-languages mail lists that 1729 the task is complete and forward the necessary materials to IANA for 1730 publication. 1732 Registrations that are in process under the rules defined in RFC 3066 1733 MAY be completed under the former rules, at the discretion of the 1734 language tag reviewer. Any new registrations submitted after the 1735 request for conversion of the registry MUST be rejected. 1737 All existing RFC 3066 language tag registrations will be maintained 1738 in perpetuity. 1740 Users of tags that are grandfathered SHOULD consider registering 1741 appropriate subtags in the IANA subtag registry (but are NOT REQUIRED 1742 to). 1744 UN numeric codes assigned to 'macro-geographical (continental)' MUST 1745 be defined in the IANA registry and made valid for use in language 1746 tags. These codes MUST be added to the initial version of the 1747 registry. The UN numeric codes for 'economic groupings' or 'other 1748 groupings', and the alphanumeric codes in Appendix X of the UN 1749 document MUST NOT be added to the registry. The UN numeric codes for 1750 countries or areas not associated with an assigned ISO 3166 alpha-2 1751 code MUST NOT be added to the initial version of the registry. These 1752 values MAY be registered by individuals using the process defined in 1753 Section 3.4 and according to the rules in Section 3.3. 1755 When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49 1756 codes, the following criteria SHALL be applied to the inclusion, 1757 preferred value, and deprecation of codes: 1759 For each standard, the date of the standard referenced in RFC 1766 is 1760 selected as the starting date. Codes that were valid on that date in 1761 the selected standard are added to the registry. Codes that were 1762 previously assigned by but which were vacated or withdrawn before 1763 that date are not added to the registry. For each successive change 1764 to the standard, any additional assignments are added to the 1765 registry. Values that are withdrawn are marked as deprecated, but 1766 not removed. Changes in meaning or assignment of a subtag are 1767 permitted during this process (for example, the ISO 3166 code 'CS' 1768 was originally assigned to 'Czechoslovakia' and is now assigned to 1769 'Serbia and Montenegro'). This continues up to the date that this 1770 document was adopted. The resulting set of records is added to the 1771 registry. Future changes or additions to this portion of the 1772 registry are governed by the provisions of this document. 1774 4. Formation and Processing of Language Tags 1776 This section addresses how to use the registry with the language tag 1777 format to choose, form and process language tags. 1779 4.1 Choice of Language Tag 1781 One is sometimes faced with the choice between several possible tags 1782 for the same body of text. 1784 Interoperability is best served when all users use the same language 1785 tag in order to represent the same language. If an application has 1786 requirements that make the rules here inapplicable, then that 1787 application risks damaging interoperability. It is strongly 1788 RECOMMENDED that users not define their own rules for language tag 1789 choice. 1791 Of particular note, many applications can benefit from the use of 1792 script subtags in language tags, as long as the use is consistent for 1793 a given context. Script subtags were not formally defined in RFC 1794 3066 and their use can affect matching and subtag identification by 1795 implementations of RFC 3066, as these subtags appear between the 1796 primary language and region subtags. For example, if a user requests 1797 content in an implementation of Section 2.5 of RFC 3066 [24] using 1798 the language range "en-US", content labeled "en-Latn-US" will not 1799 match the request. Therefore it is important to know when script 1800 subtags will customarily be used and when they ought not be used. In 1801 the registry, the Suppress-Script field helps ensure greater 1802 compatibility between the language tags generated according to the 1803 rules in this document and language tags and tag processors or 1804 consumers based on RFC 3066 by defining when users SHOULD NOT include 1805 a script subtag with a particular primary language subtag. 1807 Extended language subtags (type 'extlang' in the registry, see 1808 Section 3.1) also appear between the primary language and region 1809 subtags and are reserved for future standardization. Applications 1810 might benefit from their judicious use in forming language tags in 1811 the future. Similar recommendations are expected to apply to their 1812 use as apply to script subtags. 1814 Standards, protocols and applications that reference this document 1815 normatively but apply different rules to the ones given in this 1816 section MUST specify how the procedure varies from the one given 1817 here. 1819 The choice of subtags used to form a language tag SHOULD be guided by 1820 the following rules: 1822 1. Use as precise a tag as possible, but no more specific than is 1823 justified. Avoid using subtags that are not important for 1824 distinguishing content in an application. 1826 * For example, 'de' might suffice for tagging an email written 1827 in German, while "de-CH-1996" is probably unnecessarily 1828 precise for such a task. 1830 2. The script subtag SHOULD NOT be used to form language tags unless 1831 the script adds some distinguishing information to the tag. The 1832 field 'Suppress-Script' in the primary language record in the 1833 registry indicates which script subtags do not add distinguishing 1834 information for most applications. 1836 * For example, the subtag 'Latn' should not be used with the 1837 primary language 'en' because nearly all English documents are 1838 written in the Latin script and it adds no distinguishing 1839 information. However, if a document were written in English 1840 mixing Latin script with another script such as Braille 1841 ('Brai'), then it might be appropriate to choose to indicate 1842 both scripts to aid in content selection, such as the 1843 application of a stylesheet. 1845 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1846 entry, then the value of that field SHOULD be used to form the 1847 language tag in preference to the tag or subtag in which the 1848 preferred value appears. 1850 * For example, use 'he' for Hebrew in preference to 'iw'. 1852 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1853 used to label content, even if the language is unknown. Omitting 1854 the language tag altogether is preferred to using a tag with a 1855 primary language subtag of 'und'. The 'und' subtag MAY be useful 1856 for protocols that require a language tag to be provided. The 1857 'und' subtag MAY also be useful when matching language tags in 1858 certain situations. 1860 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1861 whenever the protocol allows the separate tags for multiple 1862 languages, as is the case for the Content-Language header in 1863 HTTP. The 'mul' subtag conveys little useful information: 1864 content in multiple languages SHOULD individually tag the 1865 languages where they appear or otherwise indicate the actual 1866 language in preference to the 'mul' subtag. 1868 6. The same variant subtag SHOULD NOT be used more than once within 1869 a language tag. 1871 * For example, do not use "en-GB-scouse-scouse". 1873 To ensure consistent backward compatibility, this document contains 1874 several provisions to account for potential instability in the 1875 standards used to define the subtags that make up language tags. 1876 These provisions mean that no language tag created under the rules in 1877 this document will become obsolete. 1879 4.2 Meaning of the Language Tag 1881 The language tag always defines a language as spoken (or written, 1882 signed or otherwise signaled) by human beings for communication of 1883 information to other human beings. Computer languages such as 1884 programming languages are explicitly excluded. 1886 If a language tag B contains language tag A as a prefix, then B is 1887 typically "narrower" or "more specific" than A. For example, "zh- 1888 Hant-TW" is more specific than "zh-Hant". 1890 This relationship is not guaranteed in all cases: specifically, 1891 languages that begin with the same sequence of subtags are NOT 1892 guaranteed to be mutually intelligible, although they might be. For 1893 example, the tag "az" shares a prefix with both "az-Latn" 1894 (Azerbaijani written using the Latin script) and "az-Cyrl" 1895 (Azerbaijani written using the Cyrillic script). A person fluent in 1896 one script might not be able to read the other, even though the text 1897 might be identical. Content tagged as "az" most probably is written 1898 in just one script and thus might not be intelligible to a reader 1899 familiar with the other script. 1901 The relationship between the tag and the information it relates to is 1902 defined by the standard describing the context in which it appears. 1903 Accordingly, this section can only give possible examples of its 1904 usage. 1906 o For a single information object, the associated language tags 1907 might be interpreted as the set of languages that is necessary for 1908 a complete comprehension of the complete object. Example: Plain 1909 text documents. 1911 o For an aggregation of information objects, the associated language 1912 tags could be taken as the set of languages used inside components 1913 of that aggregation. Examples: Document stores and libraries. 1915 o For information objects whose purpose is to provide alternatives, 1916 the associated language tags could be regarded as a hint that the 1917 content is provided in several languages, and that one has to 1918 inspect each of the alternatives in order to find its language or 1919 languages. In this case, the presence of multiple tags might not 1920 mean that one needs to be multi-lingual to get complete 1921 understanding of the document. Example: MIME multipart/ 1922 alternative. 1924 o In markup languages, such as HTML and XML, language information 1925 can be added to each part of the document identified by the markup 1926 structure (including the whole document itself). For example, one 1927 could write C'est la vie. inside a 1928 Norwegian document; the Norwegian-speaking user could then access 1929 a French-Norwegian dictionary to find out what the marked section 1930 meant. If the user were listening to that document through a 1931 speech synthesis interface, this formation could be used to signal 1932 the synthesizer to appropriately apply French text-to-speech 1933 pronunciation rules to that span of text, instead of applying the 1934 inappropriate Norwegian rules. 1936 4.3 Canonicalization of Language Tags 1938 Since a particular language tag is sometimes used by many processes, 1939 language tags SHOULD always be created or generated in a canonical 1940 form. 1942 A language tag is in canonical form when: 1944 1. The tag is well-formed according the rules in Section 2.1 and 1945 Section 2.2. 1947 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1948 the IANA registry (see Section 3.1) SHOULD be replaced with their 1949 mapped value. 1951 3. Redundant or grandfathered tags that have a Preferred-Value 1952 mapping in the IANA registry (see Section 3.1) MUST be replaced 1953 with their mapped value. These items are either deprecated 1954 mappings created before the adoption of this document (such as 1955 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1956 the result of later registrations or additions to this document 1957 (for example, "zh-guoyu" might be mapped to a language-extlang 1958 combination such as "zh-cmn" by some future update of this 1959 document). 1961 4. Other subtags that have a Preferred-Value mapping in the IANA 1962 registry (see Section 3.1) MUST be replaced with their mapped 1963 value. These items consist entirely of clerical corrections to 1964 ISO 639-1 in which the deprecated subtags have been maintained 1965 for compatibility purposes. 1967 5. If more than one extension subtag sequence exists, the extension 1968 sequences are ordered into case-insensitive ASCII order by 1969 singleton subtag. 1971 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1972 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1973 canonical form. 1975 Example: The language tag "en-NH" (English as used in the New 1976 Hebrides) is not canonical because the 'NH' subtag has a canonical 1977 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1978 validity. 1980 Canonicalization of language tags does not imply anything about the 1981 use of upper or lowercase letters when processing or comparing 1982 subtags (and as described in Section 2.1). All comparisons MUST be 1983 performed in a case-insensitive manner. 1985 When performing canonicalization of language tags, processors MAY 1986 regularize the case of the subtags (that is, this process is 1987 OPTIONAL), following the case used in the registry. Note that this 1988 corresponds to the following casing rules: uppercase all non-initial 1989 two-letter subtags; titlecase all non-initial four-letter subtags; 1990 lowercase everything else. 1992 Note: Case folding of ASCII letters in certain locales, unless 1993 carefully handled, sometimes produces non-ASCII character values. 1994 The Unicode Character Database file "SpecialCasing.txt" defines the 1995 specific cases that are known to cause problems with this. In 1996 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1997 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1998 Implementers SHOULD specify a locale-neutral casing operation to 1999 ensure that case folding of subtags does not produce this value, 2000 which is illegal in language tags. For example, if one were to 2001 uppercase the region subtag 'in' using Turkish locale rules, the 2002 sequence U+0130 U+004E would result instead of the expected 'IN'. 2004 Note: if the field 'Deprecated' appears in a registry record without 2005 an accompanying 'Preferred-Value' field, then that tag or subtag is 2006 deprecated without a replacement. Validating processors SHOULD NOT 2007 generate tags that include these values, although the values are 2008 canonical when they appear in a language tag. 2010 An extension MUST define any relationships that exist between the 2011 various subtags in the extension and thus MAY define an alternate 2012 canonicalization scheme for the extension's subtags. Extensions MAY 2013 define how the order of the extension's subtags are interpreted. For 2014 example, an extension could define that its subtags are in canonical 2015 order when the subtags are placed into ASCII order: that is, "en-a- 2016 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 2017 define that the order of the subtags influences their semantic 2018 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 2019 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 2020 so that they are tolerant of the typical processes described in 2021 Section 3.6. 2023 4.4 Considerations for Private Use Subtags 2025 Private-use subtags require private agreement between the parties 2026 that intend to use or exchange language tags that use them and great 2027 caution SHOULD be used in employing them in content or protocols 2028 intended for general use. Private-use subtags are simply useless for 2029 information exchange without prior arrangement. 2031 The value and semantic meaning of private-use tags and of the subtags 2032 used within such a language tag are not defined by this document. 2034 The use of subtags defined in the IANA registry as having a specific 2035 private use meaning convey more information that a purely private use 2036 tag prefixed by the singleton subtag 'x'. For applications this 2037 additional information MAY be useful. 2039 For example, the region subtags 'AA', 'ZZ' and in the ranges 2040 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 2041 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 2042 great deal of public, interchangeable information about the language 2043 material (that it is Chinese in the simplified Chinese script and is 2044 suitable for some geographic region 'XQ'). While the precise 2045 geographic region is not known outside of private agreement, the tag 2046 conveys far more information than an opaque tag such as "x-someLang", 2047 which contains no information about the language subtag or script 2048 subtag outside of the private agreement. 2050 However, in some cases content tagged with private use subtags MAY 2051 interact with other systems in a different and possibly unsuitable 2052 manner compared to tags that use opaque, privately defined subtags, 2053 so the choice of the best approach sometimes depends on the 2054 particular domain in question. 2056 5. IANA Considerations 2058 This section deals with the processes and requirements necessary for 2059 IANA to undertake to maintain the subtag and extension registries as 2060 defined by this document and in accordance with the requirements of 2061 RFC 2434 [12]. 2063 The impact on the IANA maintainers of the two registries defined by 2064 this document will be a small increase in the frequency of new 2065 entries or updates. 2067 Upon adoption of this document, the process described in Section 3.7 2068 will be used to generate the initial Language Subtag Registry. The 2069 initial set of records represents no impact on IANA, since the work 2070 to create it will be performed externally (as defined in that 2071 section). The new registry will be listed under "Language Tags" at 2072 . The existing directory of 2073 registration forms and RFC 3066 registrations will be relabeled as 2074 "Language Tags (Obsolete)" and maintained (but not added to or 2075 modified). 2077 Future work on the Language Subtag Registry will be limited to 2078 inserting or replacing whole records preformatted for IANA by the 2079 Language Subtag Reviewer as described in Section 3.2 of this 2080 document. Each record will be sent to iana@iana.org with a subject 2081 line indicating whether the enclosed record is an insertion (of a new 2082 record) or a replacement of an existing record which has a Type and 2083 Subtag (or Tag) field that exactly matches the record sent. Records 2084 cannot be deleted from the registry. 2086 The Language Tag Extensions registry will also be generated and sent 2087 to IANA as described in Section 3.6. This registry can contain at 2088 most 35 records and thus changes to this registry are expected to be 2089 very infrequent. 2091 Future work by IANA on the Language Tag Extensions Registry is 2092 limited to two cases. First, the IESG MAY request that new records 2093 be inserted into this registry from time to time. These requests 2094 will include the record to insert in the exact format described in 2095 Section 3.6. In addition, there MAY be occasional requests from the 2096 maintaining authority for a specific extension to update the contact 2097 information or URLs in the record. These requests MUST include the 2098 complete, updated record. IANA is not responsible for validating the 2099 information provided, only that it is properly formatted. It should 2100 reasonably be seen to come from the maintaining authority named in 2101 the record present in the registry. 2103 6. Security Considerations 2105 Language tags used in content negotiation, like any other information 2106 exchanged on the Internet, might be a source of concern because they 2107 might be used to infer the nationality of the sender, and thus 2108 identify potential targets for surveillance. 2110 This is a special case of the general problem that anything sent is 2111 visible to the receiving party and possibly to third parties as well. 2112 It is useful to be aware that such concerns can exist in some cases. 2114 The evaluation of the exact magnitude of the threat, and any possible 2115 countermeasures, is left to each application protocol (see BCP 72, 2116 RFC 3552 [16] for best current practice guidance on security threats 2117 and defenses). 2119 The language tag associated with a particular information item is of 2120 no consequence whatsoever in determining whether that content might 2121 contain possible homographs. The fact that a text is tagged as being 2122 in one language or using a particular script subtag provides no 2123 assurance whatsoever that it does not contain characters from scripts 2124 other than the one(s) associated with or specified by that language 2125 tag. 2127 Since there is no limit to the number of variant, private use, and 2128 extension subtags, and consequently no limit on the possible length 2129 of a tag, implementations need to guard against buffer overflow 2130 attacks. See Section 2.1.1 for details on language tag truncation, 2131 which can occur as a consequence of defenses against buffer overflow. 2133 Although the specification of valid subtags for an extension (see: 2134 Section 3.6) MUST be available over the Internet, implementations 2135 SHOULD NOT mechanically depend on it being always accessible, to 2136 prevent denial-of-service attacks. 2138 7. Character Set Considerations 2140 The syntax in this document requires that language tags use only the 2141 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2142 character sets, so the composition of language tags should not have 2143 any character set issues. 2145 Rendering of characters based on the content of a language tag is not 2146 addressed in this memo. Historically, some languages have relied on 2147 the use of specific character sets or other information in order to 2148 infer how a specific character should be rendered (notably this 2149 applies to language and culture specific variations of Han ideographs 2150 as used in Japanese, Chinese, and Korean). When language tags are 2151 applied to spans of text, rendering engines can use that information 2152 in deciding which font to use in the absence of other information, 2153 particularly where languages with distinct writing traditions use the 2154 same characters. 2156 8. Changes from RFC 3066 2158 The main goals for this revision of language tags were the following: 2160 *Compatibility.* All valid RFC 3066 language tags (including those 2161 in the IANA registry) remain valid in this specification. Thus 2162 there is complete backward compatibility of this specification with 2163 existing content. In addition, this document defines language tags 2164 in such as way as to ensure future compatibility, and processors 2165 based solely on the RFC 3066 ABNF (such as those described in XML 2166 Schema version 1.0 [20]) will be able to process tags described by 2167 this document. 2169 *Stability.* Because of the changes in underlying ISO standards, a 2170 valid RFC 3066 language tag may become invalid (or have its meaning 2171 change) at a later date. With so much of the world's computing 2172 infrastructure dependent on language tags, this is simply 2173 unacceptable: it invalidates content that may have an extensive 2174 shelf-life. In this specification, once a language tag is valid, it 2175 remains valid forever. Previously, there was no way to determine 2176 when two tags were equivalent. This specification provides a stable 2177 mechanism for doing so, through the use of canonical forms. These 2178 are also stable, so that implementations can depend on the use of 2179 canonical forms to assess equivalency. 2181 *Validity.* The structure of language tags defined by this document 2182 makes it possible to determine if a particular tag is well-formed 2183 without regard for the actual content or "meaning" of the tag as a 2184 whole. This is important because the registry and underlying 2185 standards change over time. In addition, it must be possible to 2186 determine if a tag is valid (or not) for a given point in time in 2187 order to provide reproducible, testable results. This process must 2188 not be error-prone; otherwise even intelligent people will generate 2189 implementations that give different results. This specification 2190 provides for that by having a single data file, with specific 2191 versioning information, so that the validity of language tags at any 2192 point in time can be precisely determined (instead of interpolating 2193 values from many separate sources). 2195 *Extensibility.* It is important to be able to differentiate between 2196 written forms of language -- for many implementations this is more 2197 important than distinguishing between spoken variants of a language. 2198 Languages are written in a wide variety of different scripts, so this 2199 document provides for the generative use of ISO 15924 script codes. 2200 Like the generative use of ISO language and country codes in RFC 2201 3066, this allows combinations to be produced without resorting to 2202 the registration process. The addition of UN codes provides for the 2203 generation of language tags with regional scope, which is also 2204 required for information technology. 2206 The recast of the registry from containing whole language tags to 2207 subtags is a key part of this. An important feature of RFC 3066 was 2208 that it allowed generative use of subtags. This allows people to 2209 meaningfully use generated tags, without the delays in registering 2210 whole tags, and the burden on the registry of having to supply all of 2211 the combinations that people may find useful. 2213 Because of the widespread use of language tags, it is potentially 2214 disruptive to have periodic revisions of the core specification, 2215 despite demonstrated need. The extension mechanism provides for a 2216 way for independent RFCs to define extensions to language tags. 2217 These extensions have a very constrained, well-defined structure to 2218 prevent extensions from interfering with implementations of language 2219 tags defined in this document. The document also anticipates 2220 features of ISO 639-3 with the addition of the extended language 2221 subtags, as well as the possibility of other ISO 639 parts becoming 2222 useful for the formation of language tags in the future. The use and 2223 definition of private use tags has also been modified, to allow 2224 people to move as much information as possible out of private use 2225 tags, and into the regular structure. The goal is to dramatically 2226 reduce the need to produce a revision of this document in the future. 2228 The specific changes in this document to meet these goals are: 2230 o Defines the ABNF and rules for subtags so that the category of all 2231 subtags can be determined without reference to the registry. 2233 o Adds the concept of well-formed vs. validating processors, 2234 defining the rules by which an implementation can claim to be one 2235 or the other. 2237 o Replaces the IANA language tag registry with a language subtag 2238 registry that provides a complete list of valid subtags in the 2239 IANA registry. This allows for robust implementation and ease of 2240 maintenance. The language subtag registry becomes the canonical 2241 source for forming language tags. 2243 o Provides a process that guarantees stability of language tags, by 2244 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2245 the event that they register a previously used value for a new 2246 purpose. 2248 o Allows ISO 15924 script code subtags and allows them to be used 2249 generatively. Defines a method for indicating in the registry 2250 when script subtags are necessary for a given language tag. 2252 o Adds the concept of a variant subtag and allows variants to be 2253 used generatively. 2255 o Adds the ability to use a class of UN M.49 tags for supra- 2256 national regions and to resolve conflicts in the assignment of ISO 2257 3166 codes. 2259 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2260 as the mechanism for creating private-use language, script, and 2261 region subtags respectively. 2263 o Adds a well-defined extension mechanism. 2265 o Defines an extended language subtag, possibly for use with certain 2266 anticipated features of ISO 639-3. 2268 Ed Note: The following items are provided for the convenience of 2269 reviewers and will be removed from the final document. 2271 Changes between draft-ietf-ltru-registry-04 and this version are: 2273 o Changes to Section 2.1.1. Incorporated Frank Ellermann's text 2274 about RFC 2231 and modified some conformance criteria. (#944) 2276 o Changed Section 2.2.4 and added UN M.49 to the list of standards 2277 monitored for changes in Section 3.4, plus added some additional 2278 squirms to Section 3.3 to ensure that ISO-3166-less UN M.49 codes 2279 are not registered automagically but may be registered by 2280 individuals given inaction on the part of ISO 3166 for 180 days. 2281 Also made the assignments of UN M.49 codes in Section 2.2.4 2282 normative (MUST instead of 'are'). Finally, the initial rules 2283 were modified to reflect the foregoing in Section 3.7. (#1026) 2284 (D.Ewell, P.Constable, A.Phillips) 2286 o Added text to Section 3.5 allowing new entries and other changes 2287 per the rules in Section 3.3 (A.Phillips) 2289 o Added text to Section 2.2.4 and Section 3.3 forbidding the 2290 registration of UN M.49 country or area codes not assigned an ISO 2291 3166 code. (#1026) (A.Phillips) 2293 o Harmonized the rules pertaining to position and number of script 2294 and region subtags (basically now they say that they MUST occur 2295 only once and MAY be omitted) (A.Phillips) 2297 o Added the homograph paragraph to Section 6. (#967)(R.Presuhn) 2299 9. References 2301 9.1 Normative References 2303 [1] International Organization for Standardization, "ISO 639- 2304 1:2002, Codes for the representation of names of languages -- 2305 Part 1: Alpha-2 code", ISO Standard 639, 2002. 2307 [2] International Organization for Standardization, "ISO 639-2:1998 2308 - Codes for the representation of names of languages -- Part 2: 2309 Alpha-3 code - edition 1", August 1988. 2311 [3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2312 representation of names of scripts", January 2004. 2314 [4] International Organization for Standardization, "Codes for the 2315 representation of names of countries, 3rd edition", 2316 ISO Standard 3166, August 1988. 2318 [5] Statistical Division, United Nations, "Standard Country or Area 2319 Codes for Statistical Use", UN Standard Country or Area Codes 2320 for Statistical Use, Revision 4 (United Nations publication, 2321 Sales No. 98.XVII.9, June 1999. 2323 [6] International Organization for Standardization, "ISO/IEC 10646- 2324 1:2000. Information technology -- Universal Multiple-Octet 2325 Coded Character Set (UCS) -- Part 1: Architecture and Basic 2326 Multilingual Plane and ISO/IEC 10646-2:2001. Information 2327 technology -- Universal Multiple-Octet Coded Character Set 2328 (UCS) -- Part 2: Supplementary Planes, as, from time to time, 2329 amended, replaced by a new edition or expanded by the addition 2330 of new parts", 2000. 2332 [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2333 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 (work 2334 in progress), March 2005. 2336 [8] Bradner, S., "The Internet Standards Process -- Revision 3", 2337 BCP 9, RFC 2026, October 1996. 2339 [9] Hovey, R. and S. Bradner, "The Organizations Involved in the 2340 IETF Standards Process", BCP 11, RFC 2028, October 1996. 2342 [10] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part 2343 Three: Message Header Extensions for Non-ASCII Text", RFC 2047, 2344 November 1996. 2346 [11] Bradner, S., "Key words for use in RFCs to Indicate Requirement 2347 Levels", BCP 14, RFC 2119, March 1997. 2349 [12] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 2350 Considerations Section in RFCs", BCP 26, RFC 2434, 2351 October 1998. 2353 [13] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 10646", 2354 RFC 2781, February 2000. 2356 [14] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2357 Understanding Concerning the Technical Work of the Internet 2358 Assigned Numbers Authority", RFC 2860, June 2000. 2360 [15] Klyne, G. and C. Newman, "Date and Time on the Internet: 2361 Timestamps", RFC 3339, July 2002. 2363 [16] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on 2364 Security Considerations", BCP 72, RFC 3552, July 2003. 2366 9.2 Informative References 2368 [17] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2369 Committee: Working principles for ISO 639 maintenance", 2370 March 2000, 2371 . 2373 [18] Raymond, E., "The Art of Unix Programming", 2003. 2375 [19] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2376 02 2004. 2378 [20] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2379 Datatypes Second Edition", 10 2004, < 2380 http://www.w3.org/TR/xmlschema-2/>. 2382 [21] Unicode Consortium, "The Unicode Consortium. The Unicode 2383 Standard, Version 4.1.0, defined by: The Unicode Standard, 2384 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2385 18578-1), as amended by Unicode 4.0.1 2386 (http://www.unicode.org/versions/Unicode4.0.1) and by Unicode 2387 4.1.0 (http://www.unicode.org/versions/Unicode4.1.0).", 2388 March 2005. 2390 [22] Alvestrand, H., "Tags for the Identification of Languages", 2391 RFC 1766, March 1995. 2393 [23] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word 2394 Extensions: Character Sets, Languages, and Continuations", 2395 RFC 2231, November 1997. 2397 [24] Alvestrand, H., "Tags for the Identification of Languages", 2398 BCP 47, RFC 3066, January 2001. 2400 Authors' Addresses 2402 Addison Phillips (editor) 2403 Quest Software 2405 Email: addison.phillips@quest.com 2407 Mark Davis (editor) 2408 IBM 2410 Email: mark.davis@us.ibm.com 2412 Appendix A. Acknowledgements 2414 Any list of contributors is bound to be incomplete; please regard the 2415 following as only a selection from the group of people who have 2416 contributed to make this document what it is today. 2418 The contributors to RFC 3066 and RFC 1766, the precursors of this 2419 document, made enormous contributions directly or indirectly to this 2420 document and are generally responsible for the success of language 2421 tags. 2423 The following people (in alphabetical order) contributed to this 2424 document or to RFCs 1766 and 3066: 2426 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2427 Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco 2428 Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable, 2429 John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank 2430 Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk- 2431 Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold, 2432 Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent 2433 Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald, 2434 Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George 2435 Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto 2436 Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois 2437 Yergeau and many, many others. 2439 Very special thanks must go to Harald Tveit Alvestrand, who 2440 originated RFCs 1766 and 3066, and without whom this document would 2441 not have been possible. Special thanks must go to Michael Everson, 2442 who has served as language tag reviewer for almost the complete 2443 period since the publication of RFC 1766. Special thanks to Doug 2444 Ewell, for his production of the first complete subtag registry, and 2445 his work in producing a test parser for verifying language tags. 2447 Appendix B. Examples of Language Tags (Informative) 2449 Simple language subtag: 2451 de (German) 2453 fr (French) 2455 ja (Japanese) 2457 i-enochian (example of a grandfathered tag) 2459 Language subtag plus Script subtag: 2461 zh-Hant (Chinese written using the Traditional Chinese script) 2463 zh-Hans (Chinese written using the Simplified Chinese script) 2465 sr-Cyrl (Serbian written using the Cyrillic script) 2467 sr-Latn (Serbian written using the Latin script) 2469 Language-Script-Region: 2471 zh-Hans-CN (Chinese written using the Simplified script as used in 2472 mainland China) 2474 sr-Latn-CS (Serbian written using the Latin script as used in 2475 Serbia and Montenegro) 2477 Language-Variant: 2479 en-boont (Boontling dialect of English) 2481 en-scouse (Scouse dialect of English) 2483 Language-Region-Variant: 2485 en-GB-scouse (Scouse dialect of English as used in the UK) 2487 Language-Script-Region-Variant: 2489 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2490 Latin script as used in Italy. Note that this tag is NOT 2491 RECOMMENDED because subtag 'sl' has a Suppress-Script value of 2492 'Latn') 2494 Language-Region: 2496 de-DE (German for Germany) 2498 en-US (English as used in the United States) 2500 es-419 (Spanish for Latin America and Caribbean region using the 2501 UN region code) 2503 Private-use subtags: 2505 de-CH-x-phonebk 2507 az-Arab-x-AZE-derbend 2509 Extended language subtags (examples ONLY: extended languages MUST be 2510 defined by revision or update to this document): 2512 zh-min 2514 zh-min-nan-Hant-CN 2516 Private-use registry values: 2518 x-whatever (private use using the singleton 'x') 2520 qaa-Qaaa-QM-x-southern (all private tags) 2522 de-Qaaa (German, with a private script) 2524 sr-Latn-QM (Serbian, Latin-script, private region) 2526 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2528 Tags that use extensions (examples ONLY: extensions MUST be defined 2529 by revision or update to this document or by RFC): 2531 en-US-u-islamCal 2533 zh-CN-a-myExt-x-private 2535 en-a-myExt-b-another 2537 Some Invalid Tags: 2539 de-419-DE (two region tags) 2540 a-DE (use of a single character subtag in primary position; note 2541 that there are a few grandfathered tags that start with "i-" that 2542 are valid) 2544 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2545 prefix) 2547 Appendix C. Example Registry 2549 Example Registry 2551 File-Date: 2005-04-18 2552 %% 2553 Type: language 2554 Subtag: aa 2555 Description: Afar 2556 Added: 2004-07-06 2557 %% 2558 Type: language 2559 Subtag: ab 2560 Description: Abkhazian 2561 Added: 2004-07-06 2562 %% 2563 Type: language 2564 Subtag: ae 2565 Description: Avestan 2566 Added: 2004-07-06 2567 %% 2568 Type: language 2569 Subtag: ar 2570 Description: Arabic 2571 Added: 2004-07-06 2572 Suppress-Script: Arab 2573 Comment: Arabic text is usually written in Arabic script 2574 %% 2575 Type: language 2576 Subtag: qaa..qtz 2577 Description: PRIVATE USE 2578 Added: 2004-08-01 2579 Comment: Use private use codes in preference 2580 to the x- singleton for primary language 2581 Comment: This is an example of two comments. 2582 %% 2583 Type: script 2584 Subtag: Arab 2585 Description: Arabic 2586 Added: 2004-07-06 2587 %% 2588 Type: script 2589 Subtag: Armn 2590 Description: Armenian 2591 Added: 2004-07-06 2592 %% 2593 Type: script 2594 Subtag: Bali 2595 Description: Balinese 2596 Added: 2004-07-06 2597 %% 2598 Type: script 2599 Subtag: Batk 2600 Description: Batak 2601 Added: 2004-07-06 2602 %% 2603 Type: region 2604 Subtag: AA 2605 Description: PRIVATE USE 2606 Added: 2004-08-01 2607 %% 2608 Type: region 2609 Subtag: AD 2610 Description: Andorra 2611 Added: 2004-07-06 2612 %% 2613 Type: region 2614 Subtag: AE 2615 Description: United Arab Emirates 2616 Added: 2004-07-06 2617 %% 2618 Type: region 2619 Subtag: AX 2620 Description: Åland Islands 2621 Added: 2004-07-06 2622 Comments: The description shows a Unicode escape 2623 for the letter A-ring. 2624 %% 2625 Type: region 2626 Subtag: 001 2627 Description: World 2628 Added: 2004-07-06 2629 %% 2630 Type: region 2631 Subtag: 002 2632 Description: Africa 2633 Added: 2004-07-06 2634 %% 2635 Type: region 2636 Subtag: 003 2637 Description: North America 2638 Added: 2004-07-06 2639 %% 2640 Type: variant 2641 Subtag: 1901 2642 Description: Traditional German 2643 orthography 2644 Added: 2004-09-09 2645 Prefix: de 2646 Comment: 2647 %% 2648 Type: variant 2649 Subtag: 1996 2650 Description: German orthography of 1996 2651 Added: 2004-09-09 2652 Prefix: de 2653 %% 2654 Type: variant 2655 Subtag: boont 2656 Description: Boontling 2657 Added: 2003-02-14 2658 Prefix: en 2659 %% 2660 Type: variant 2661 Subtag: gaulish 2662 Description: Gaulish 2663 Added: 2001-05-25 2664 Prefix: cel 2665 %% 2666 Type: grandfathered 2667 Tag: art-lojban 2668 Description: Lojban 2669 Added: 2001-11-11 2670 Canonical: jbo 2671 Deprecated: 2003-09-02 2672 %% 2673 Type: grandfathered 2674 Tag: en-GB-oed 2675 Description: English, Oxford English Dictionary spelling 2676 Added: 2003-07-09 2677 %% 2678 Type: grandfathered 2679 Tag: i-ami 2680 Description: 'Amis 2681 Added: 1999-05-25 2682 %% 2683 Type: grandfathered 2684 Tag: i-bnn 2685 Description: Bunun 2686 Added: 1999-05-25 2687 %% 2688 Type: redundant 2689 Tag: az-Arab 2690 Description: Azerbaijani in Arabic script 2691 Added: 2003-05-30 2692 %% 2693 Type: redundant 2694 Tag: az-Cyrl 2695 Description: Azerbaijani in Cyrillic script 2696 Added: 2003-05-30 2697 %% 2699 Figure 9: Example of the Registry Format 2701 Intellectual Property Statement 2703 The IETF takes no position regarding the validity or scope of any 2704 Intellectual Property Rights or other rights that might be claimed to 2705 pertain to the implementation or use of the technology described in 2706 this document or the extent to which any license under such rights 2707 might or might not be available; nor does it represent that it has 2708 made any independent effort to identify any such rights. 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