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If it is intended as a requirements expression, it should be rewritten using one of the combinations defined in RFC 2119; otherwise it should not be all-uppercase. == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: The tags and their subtags, including private-use and extensions, are to be treated as case insensitive: there exist conventions for the capitalization of some of the subtags, but these MUST not be taken to carry meaning. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). 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 03, 2005) is 6902 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. '11') (Obsoleted by RFC 5226) ** Downref: Normative reference to an Informational RFC: RFC 2781 (ref. '12') ** Downref: Normative reference to an Informational RFC: RFC 2860 (ref. '13') ** Obsolete normative reference: RFC 2822 (ref. '14') (Obsoleted by RFC 5322) -- 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: 8 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 5, 2005 M. Davis, Ed. 5 IBM 6 June 03, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-04 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 5, 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 . . . . . . . . . . . . . . . . . 16 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 . . . . . . . . . . . . 28 70 3.5 Possibilities for Registration . . . . . . . . . . . . . . 31 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 . . . . . . . . . . . . . . . . . . . . . . . . . . 52 83 9.1 Normative References . . . . . . . . . . . . . . . . . . . 52 84 9.2 Informative References . . . . . . . . . . . . . . . . . . 53 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 54 86 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 55 87 B. Examples of Language Tags (Informative) . . . . . . . . . . . 56 88 C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 59 89 Intellectual Property and Copyright Statements . . . . . . . . 63 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 [10]. 135 2. The Language Tag 137 2.1 Syntax 139 The language tag is composed of one or more parts: A primary language 140 subtag and a (possibly empty) series of subsequent subtags. Subtags 141 are distinguished by their length, position in the subtag sequence, 142 and content, so that each type of subtag can be recognized solely by 143 these features. This makes it possible to construct a parser that 144 can extract and assign some semantic information to the subtags, even 145 if specific subtag values are not recognized. Thus a parser need not 146 have an up-to-date copy of the registered subtag values to perform 147 most searching and matching operations. 149 The syntax of this tag in ABNF [7] is: 151 Language-Tag = (lang 152 *3("-" extlang) 153 ["-" script] 154 ["-" region] 155 *("-" variant) 156 *("-" extension) 157 ["-" privateuse]) 158 / privateuse ; private-use tag 159 / grandfathered ; grandfathered registrations 161 lang = 2*4ALPHA ; shortest ISO 639 code 162 / registered-lang 163 extlang = 3ALPHA ; reserved for future use 164 script = 4ALPHA ; ISO 15924 code 165 region = 2ALPHA ; ISO 3166 code 166 / 3DIGIT ; UN country number 167 variant = 5*8alphanum ; registered variants 168 / ( DIGIT 3alphanum ) 169 extension = singleton 1*("-" (2*8alphanum)) 170 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 171 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 172 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 173 ; Single letters: x/X is reserved for private use 174 registered-lang = 4*8ALPHA ; registered language subtag 175 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 176 ; grandfathered registration 177 ; Note: i is the only singleton 178 ; that starts a grandfathered tag 179 alphanum = (ALPHA / DIGIT) ; letters and numbers 181 Figure 1: Language Tag ABNF 183 The character "-" is HYPHEN-MINUS (ABNF: %x2D). All subtags have a 184 maximum length of eight characters. Note that there is a subtlety in 185 the ABNF for 'variant': variants starting with a digit MAY be 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 [12] 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 much 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 language tag's length is 276 limited by the length of other header components (such as the 277 charset's name) coupled with the 78 character limit in [RFC 2822] 278 [14]. Thus the "limit" might be 60 or more characters, but it could 279 potentially be quite small. In these cases, implementations SHOULD 280 use the longest possible language tag. Warning the user of 281 truncation, if necessary, is RECOMMENDED, as truncation can change 282 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) [13] 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 Example: "de-Latn" represents German written using the Latin script. 534 2.2.4 Region Subtag 536 The following rules apply to the region subtags: 538 1. The region subtag defines language variations used in a specific 539 region, geographic, or political area. Region subtags MUST 540 follow any language, extended language, or script subtags and 541 MUST precede all other subtags. 543 2. All two character subtags following the primary subtag were 544 defined in the IANA registry according to the assignments found 545 in ISO 3166 [4]--"Codes for the representation of names of 546 countries and their subdivisions - Part 1: Country 547 codes"--alpha-2 country codes or assignments subsequently made by 548 the ISO 3166 maintenance agency or governing standardization 549 bodies. 551 3. All three character codes consisting of digit (numeric) 552 characters were defined in the IANA registry according to the 553 assignments found in UN Standard Country or Area Codes for 554 Statistical Use [5] or assignments subsequently made by the 555 governing standards body. Note that not all of the UN M.49 codes 556 are defined in the IANA registry: 558 A. UN numeric codes assigned to 'macro-geographical 559 (continental)' or sub-regions not associated with an assigned 560 ISO 3166 alpha-2 code _are_ defined. 562 B. UN numeric codes for 'economic groupings' or 'other 563 groupings' are _not_ defined in the IANA registry and MUST 564 NOT be used to form language tags. 566 C. UN numeric codes for countries with ambiguous ISO 3166 567 alpha-2 codes as defined in Section 3.3 are defined in the 568 registry and are canonical for the given country or region 569 defined. 571 D. The alphanumeric codes in Appendix X of the UN document are 572 _not_ defined and MUST NOT be used to form language tags. 573 (At the time this document was created these values match the 574 ISO 3166 alpha-2 codes.) 576 4. There MUST be at most one region subtag in a language tag. 578 5. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 579 reserved for private use in language tags. These subtags 580 correspond to codes reserved by ISO 3166 for private use. These 581 codes MAY be used for private use region subtags (instead of 582 using a private-use subtag sequence). Please refer to 583 Section 4.4 for more information on private use subtags. 585 "de-CH" represents German ('de') as used in Switzerland ('CH'). 587 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 588 ('Latn') as used in Serbia and Montenegro ('CS'). 590 "es-419" represents Spanish ('es') as used in the UN-defined Latin 591 America and Caribbean region ('419'). 593 2.2.5 Variant Subtags 595 The following rules apply to the variant subtags: 597 1. Variant subtags are not associated with any external standard. 598 Variant subtags and their meanings are defined by the 599 registration process defined in Section 3.4. 601 2. Variant subtags MUST follow all of the other defined subtags, but 602 precede any extension or private-use subtag sequences. 604 3. More than one variant MAY be used to form the language tag. 606 4. Variant subtags MUST be registered with IANA according to the 607 rules in Section 3.4 of this document before being used to form 608 language tags. In order to distinguish variants from other types 609 of subtags, registrations MUST meet the following length and 610 content restrictions: 612 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 613 at least five characters long. 615 2. Variant subtags that begin with a digit (0-9) MUST be at 616 least four characters long. 618 Variant subtag records in the language subtag registry MAY include 619 one or more 'Prefix' fields, which indicates the language tag or tags 620 that would make a suitable prefix (with other subtags, as 621 appropriate) in forming a language tag with the variant. For 622 example, the subtag 'scouse' has a Prefix of "en", making it suitable 623 to form language tags such as "en-scouse" and "en-GB-scouse", but not 624 suitable for use in a tag such as "zh-scouse" or "it-GB-scouse". 626 "en-scouse" represents the Scouse dialect of English. 628 "de-CH-1996" represents German as used in Switzerland and as written 629 using the spelling reform beginning in the year 1996 C.E. 631 Most variants that share a prefix are mutually exclusive. For 632 example, the German orthographic variantions '1996' and '1901' SHOULD 633 NOT be used in the same tag, as they represent the dates of different 634 spelling reforms. A variant that can meaningfully be used in 635 combination with another variant SHOULD include a 'Prefix' field in 636 its registry record that lists that other variant. For example, if 637 another German variant 'example' were created that made sense to use 638 with '1996', then 'example' should include two Prefix fields: "de" 639 and "de-1996". 641 2.2.6 Extension Subtags 643 The following rules apply to extensions: 645 1. Extension subtags are separated from the other subtags defined 646 in this document by a single-letter subtag ("singleton"). The 647 singleton MUST be one allocated to a registration authority via 648 the mechanism described in Section 3.6 and cannot be the letter 649 'x', which is reserved for private-use subtag sequences. 651 2. Note: Private-use subtag sequences starting with the singleton 652 subtag 'x' are described below. 654 3. An extension MUST follow at least a primary language subtag. 655 That is, a language tag cannot begin with an extension. 656 Extensions extend language tags, they do not override or replace 657 them. For example, "a-value" is not a well-formed language tag, 658 while "de-a-value" is. 660 4. Each singleton subtag MUST appear at most one time in each tag 661 (other than as a private-use subtag). That is, singleton 662 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 663 ccc" is invalid because the subtag 'a' appears twice. Note that 664 the tag "en-a-bbb-x-a-ccc" is valid because the second 665 appearance of the singleton 'a' is in a private use sequence. 667 5. Extension subtags MUST meet all of the requirements for the 668 content and format of subtags defined in this document. 670 6. Extension subtags MUST meet whatever requirements are set by the 671 document that defines their singleton prefix and whatever 672 requirements are provided by the maintaining authority. 674 7. Each extension subtag MUST be from two to eight characters long 675 and consist solely of letters or digits, with each subtag 676 separated by a single '-'. 678 8. Each singleton MUST be followed by at least one extension 679 subtag. For example, the tag "tlh-a-b-foo" is invalid because 680 the first singleton 'a' is followed immediately by another 681 singleton 'b'. 683 9. Extension subtags MUST follow all language, extended language, 684 script, region and variant subtags in a tag. 686 10. All subtags following the singleton and before another singleton 687 are part of the extension. Example: In the tag "fr-a-Latn", the 688 subtag 'Latn' does not represent the script subtag 'Latn' 689 defined in the IANA Language Subtag Registry. Its meaning is 690 defined by the extension 'a'. 692 11. In the event that more than one extension appears in a single 693 tag, the tag SHOULD be canonicalized as described in 694 Section 4.3. 696 For example, if the prefix singleton 'r' and the shown subtags were 697 defined, then the following tag would be a valid example: "en-Latn- 698 GB-boont-r-extended-sequence-x-private" 700 2.2.7 Private Use Subtags 702 The following rules apply to private-use subtags: 704 1. Private-use subtags are separated from the other subtags defined 705 in this document by the reserved single-character subtag 'x'. 707 2. Private-use subtags MUST follow all language, extended language, 708 script, region, variant, and extension subtags in the tag. 709 Another way of saying this is that all subtags following the 710 singleton 'x' MUST be considered private use. Example: The 711 subtag 'US' in the tag "en-x-US" is a private use subtag. 713 3. A tag MAY consist entirely of private-use subtags. 715 4. No source is defined for private use subtags. Use of private use 716 subtags is by private agreement only. 718 For example: Users who wished to utilize SIL Ethnologue for 719 identification might agree to exchange tags such as "az-Arab-x-AZE- 720 derbend". This example contains two private-use subtags. The first 721 is 'AZE' and the second is 'derbend'. 723 2.2.8 Pre-Existing RFC 3066 Registrations 725 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 726 maintain their validity. IANA will maintain these tags in the 727 registry under either the "grandfathered" or "redundant" type. For 728 more information see Section 3.7. 730 It is important to note that all language tags formed under the 731 guidelines in this document were either legal, well-formed tags or 732 could have been registered under RFC 3066. 734 2.2.9 Classes of Conformance 736 Implementations sometimes need to describe their capabilities with 737 regard to the rules and practices described in this document. There 738 are two classes of conforming implementations described by this 739 document: "well-formed" processors and "validating" processors. 740 Claims of conformance SHOULD explicitly reference one of these 741 definitions. 743 An implementation that claims to check for well-formed language tags 744 MUST: 746 o Check that the tag and all of its subtags, including extension and 747 private-use subtags, conform to the ABNF or that the tag is on the 748 list of grandfathered tags. 750 o Check that singleton subtags that identify extensions do not 751 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 752 formed. 754 Well-formed processors are strongly encouraged to implement the 755 canonicalization rules contained in Section 4.3. 757 An implementation that claims to be validating MUST: 759 o Check that the tag is well-formed. 761 o Specify the particular registry date for which the implementation 762 performs validation of subtags. 764 o Check that either the tag is a grandfathered tag, or that all 765 language, script, region, and variant subtags consist of valid 766 codes for use in language tags according to the IANA registry as 767 of the particular date specified by the implementation. 769 o Specify which, if any, extension RFCs as defined in Section 3.6 770 are supported, including version, revision, and date. 772 o For any such extensions supported, check that all subtags used in 773 that extension are valid. 775 o For variant and extended language subtags, if the registry 776 contains one or more 'Prefix' fields for that subtag, check that 777 the tag matches at least one prefix. The tag matches if all the 778 subtags in the 'Prefix' also appear in the tag. For example, the 779 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 780 the 'es' language subtag and 'CO' region subtag appear in the tag. 782 3. Registry Format and Maintenance 784 This section defines the Language Subtag Registry and the maintenance 785 and update procedures associated with it. 787 The language subtag registry will be maintained so that, except for 788 extension subtags, it is possible to validate all of the subtags that 789 appear in a language tag under the provisions of this document or its 790 revisions or successors. In addition, the meaning of the various 791 subtags will be unambiguous and stable over time. (The meaning of 792 private-use subtags, of course, is not defined by the IANA registry.) 794 The registry defined under this document contains a comprehensive 795 list of all of the subtags valid in language tags. This allows 796 implementers a straightforward and reliable way to validate language 797 tags. 799 3.1 Format of the IANA Language Subtag Registry 801 The IANA Language Subtag Registry ("the registry") will consist of a 802 text file that is machine readable in the format described in this 803 section, plus copies of the registration forms approved by the 804 Language Subtag Reviewer in accordance with the process described in 805 Section 3.4. With the exception of the registration forms for 806 grandfathered and redundant tags, no registration records will be 807 maintained for the initial set of subtags. 809 The registry will be in a modified record-jar format text file [18]. 810 Lines are limited to 72 characters, including all whitespace. 812 Records are separated by lines containing only the sequence "%%" 813 (%x25.25). 815 Each field can be viewed as a single, logical line of ASCII 816 characters, comprising a field-name and a field-body separated by a 817 COLON character (%x3A). For convenience, the field-body portion of 818 this conceptual entity can be split into a multiple-line 819 representation; this is called "folding". The format of the registry 820 is described by the following ABNF (per [7]): 822 registry = record *("%%" CRLF record) 823 record = 1*( field-name *SP ":" *SP field-body CRLF ) 824 field-name = *(ALPHA / DIGIT / "-") 825 field-body = *(ASCCHAR/LWSP) 826 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 827 UNICHAR = "&#x" 2*6HEXDIG ";" 829 The sequence '..' (%x2E.2E) in a field-body denotes a range of 830 values. Such a range represents all subtags of the same length that 831 are alphabetically within that range, including the values explicitly 832 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 834 Characters from outside the US-ASCII repertoire, as well as the 835 AMPERSAND character ("&", %x26) when it occurs in a field-body are 836 represented by a "Numeric Character Reference" using hexadecimal 837 notation in the style used by XML 1.0 [19] (see 838 ). This consists of the 839 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 840 of the character's code point in ISO/IEC 10646 [6] followed by a 841 closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would 842 be represented by the sequence "€". Note that the hexadecimal 843 notation MAY have between two and six digits. 845 All fields whose field-body contains a date value use the "full-date" 846 format specified in RFC 3339 [15]. For example: "2004-06-28" 847 represents June 28, 2004 in the Gregorian calendar. 849 The first record in the file contains the single field whose field- 850 name is "File-Date". The field-body of this record contains the last 851 modification date of this copy of the registry, making it possible to 852 compare different versions of the registry. The registry on the IANA 853 website is the most current. Versions with an older date than that 854 one are not up-to-date. 856 File-Date: 2004-06-28 857 %% 859 Subsequent records represent subtags in the registry. Each of the 860 fields in each record MUST occur no more than once, unless otherwise 861 noted below. Each record MUST contain the following fields: 863 o 'Type' 865 * Type's field-value MUST consist of one of the following 866 strings: "language", "extlang", "script", "region", "variant", 867 "grandfathered", and "redundant" and denotes the type of tag or 868 subtag. 870 o Either 'Subtag' or 'Tag' 872 * Subtag's field-value contains the subtag being defined. This 873 field MUST only appear in records of whose Type has one of 874 these values: "language", "extlang", "script", "region", or 875 "variant". 877 * Tag's field-value contains a complete language tag. This field 878 MUST only appear in records whose Type has one of these values: 879 "grandfathered" or "redundant". 881 o Description 883 * Description's field-value contains a non-normative description 884 of the subtag or tag. 886 o Added 888 * Added's field-value contains the date the record was added to 889 the registry. 891 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 892 subtag or tag, with two exceptions. Subtags whose 'Type' field is 893 'script' (in other words, subtags defined by ISO 15924) MUST use 894 titlecase. Subtags whose 'Type' field is 'region' (in other words, 895 subtags defined by ISO 3166) MUST use uppercase. These exceptions 896 mirror the use of case in the underlying standards. 898 The field 'Description' MAY appear more than one time. At least one 899 of the 'Description' fields MUST contain a description of the tag 900 being registered written or transcribed into the Latin script; the 901 same or additional fields MAY also include a description in a non- 902 Latin script. The 'Description' field is used for identification 903 purposes and SHOULD NOT be taken to represent the actual native name 904 of the language or variation or to be in any particular language. 905 Most descriptions are taken directly from source standards such as 906 ISO 639 or ISO 3166. 908 Note: Descriptions in registry entries that correspond to ISO 639, 909 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 910 the meaning of that identifier as defined in the source standard at 911 the time it was added to the registry. The description does not 912 replace the content of the source standard itself. The descriptions 913 are not intended to be the English localized names for the subtags. 914 Localization or translation of language tag and subtag descriptions 915 is out of scope of this document. 917 Each record MAY also contain the following fields: 919 o Preferred-Value 921 * For fields of type 'language', 'extlang', 'script', 'region', 922 and 'variant', 'Preferred-Value' contains a subtag of the same 923 'Type' which is preferred for forming the language tag. 925 * For fields of type 'grandfathered' and 'redundant', a canonical 926 mapping to a complete language tag. 928 o Deprecated 930 * Deprecated's field-value contains the date the record was 931 deprecated. 933 o Prefix 935 * Prefix's field-value contains a language tag with which this 936 subtag MAY be used to form a new language tag, perhaps with 937 other subtags as well. This field MUST only appear in records 938 whose 'Type' field-value is 'variant' or 'extlang'. For 939 example, the 'Prefix' for the variant 'scouse' is 'en', meaning 940 that the tags "en-scouse" and "en-GB-scouse" might be 941 appropriate while the tag "is-scouse" is not. 943 o Comments 945 * Comments contains additional information about the subtag, as 946 deemed appropriate for understanding the registry and 947 implementing language tags using the subtag or tag. 949 o Suppress-Script 951 * Suppress-Script contains a script subtag that SHOULD NOT be 952 used to form language tags with the associated primary language 953 subtag. This field MUST only appear in records whose 'Type' 954 field-value is 'language'. See Section 4.1. 956 The field 'Deprecated' MAY be added to any record via the maintenance 957 process described in Section 3.2 or via the registration process 958 described in Section 3.4. Usually the addition of a 'Deprecated' 959 field is due to the action of one of the standards bodies, such as 960 ISO 3166, withdrawing a code. In some historical cases it might not 961 have been possible to reconstruct the original deprecation date. 962 For these cases, an approximate date appears in the registry. 963 Although valid in language tags, subtags and tags with a 'Deprecated' 964 field are deprecated and validating processors SHOULD NOT generate 965 these subtags. Note that a record that contains a 'Deprecated' field 966 and no corresponding 'Preferred-Value' field has no replacement 967 mapping. 969 Thie field 'Preferred-Value' contains a mapping between the record in 970 which it appears and a tag or subtag which SHOULD be preferred when 971 selected language tags. These values form three groups: 973 ISO 639 language codes which were later withdrawn in favor of 974 other codes. These values are mostly a historical curiosity. 976 ISO 3166 region codes which have been withdrawn in favor of a new 977 code. This sometimes happens when a country changes its name or 978 administration in such a way that warrents a new region code. 980 Tags grandfathered from RFC 3066. In many cases these tags have 981 become obsolete because the values they represent were later 982 encoded by ISO 639. 984 Records that contain a 'Preferred-Value' field MUST also have a 985 'Deprecated' field. This field contains a date of deprecation. Thus 986 a language tag processor can use the registry to construct the valid, 987 non-deprecated set of subtags for a given date. In addition, for any 988 given tag, a processor can construct the set of valid language tags 989 that correspond to that tag for all dates up to the date of the 990 registry. The ability to do these mappings MAY be beneficial to 991 applications that are matching, selecting, for filtering content 992 based on its language tags. 994 Note that 'Preferred-Value' mappings in records of type 'region' MAY 995 NOT represent exactly the same meaning as the original value. There 996 are many reasons for a country code to be changed and the effect this 997 has on the formation of language tags will depend on the nature of 998 the change in question. 1000 In particular, the 'Preferred-Value' field does not imply retagging 1001 content that uses the affected subtag. 1003 The field 'Preferred-Value' MUST NOT be modified once created in the 1004 registry. The field MAY be added to records of type "grandfathered" 1005 and "region" according to the rules in Section 3.2. Otherwise the 1006 field MUST NOT be added to any record already in the registry. 1008 The 'Preferred-Value' field in records of type "grandfathered" and 1009 "redundant" contains whole language tags that are strongly 1010 RECOMMENDED for use in place of the record's value. In many cases 1011 the mappings were created by deprecation of the tags during the 1012 period before this document was adopted. For example, the tag "no- 1013 nyn" was deprecated in favor of the ISO 639-1 defined language code 1014 'nn'. 1016 Records of type 'variant' MAY have more than one field of type 1017 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1018 record via the registration process. 1020 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 1022 The field-value of the 'Prefix' field consists of a language tag 1023 whose subtags are appropriate to use with this subtag. For example, 1024 the variant subtag 'scouse' has a Prefix field of "en". This means 1025 that tags starting with the sequence "en-" are most appropriate with 1026 this subtag, so "en-Latn-scouse" and "en-GB-scouse" are both 1027 acceptable, while the tag "fr-scouse" is an inappropriate choice. 1029 The field of type 'Prefix' MUST NOT be removed from any record. The 1030 field-value for this type of field MUST NOT be modified. 1032 The field 'Comments' MAY appear more than once per record. This 1033 field MAY be inserted or changed via the registration process and no 1034 guarantee of stability is provided. The content of this field is not 1035 restricted, except by the need to register the information, the 1036 suitability of the request, and by reasonable practical size 1037 limitations. Long screeds about a particular subtag are frowned 1038 upon. 1040 The field 'Suppress-Script' MUST only appear in records whose 'Type' 1041 field-value is 'language'. This field MAY appear at most one time in 1042 a record. This field indicates a script used to write the 1043 overwhelming majority of documents for the given language and which 1044 therefore adds no distinguishing information to a language tag. It 1045 helps ensure greater compatibility between the language tags 1046 generated according to the rules in this document and language tags 1047 and tag processors or consumers based on RFC 3066. For example, 1048 virtually all Icelandic documents are written in the Latin script, 1049 making the subtag 'Latn' redundant in the tag "is-Latn". 1051 For examples of registry entries and their format, see Appendix C. 1053 3.2 Maintenance of the Registry 1055 Maintenance of the registry requires that as codes are assigned or 1056 withdrawn by ISO 639, ISO 15924, and ISO 3166, the Language Subtag 1057 Reviewer will evaluate each change, determine whether it conflicts 1058 with existing registry entries, and submit the information to IANA 1059 for inclusion in the registry. If an change takes place and the 1060 Language Subtag Reviewer does not do this in a timely manner, then 1061 any interested party MAY use the procedure in Section 3.4 to register 1062 the appropriate update. 1064 Note: The redundant and grandfathered entries together are the 1065 complete list of tags registered under RFC 3066 [24]. The redundant 1066 tags are those that can now be formed using the subtags defined in 1067 the registry together with the rules of Section 2.2. The 1068 grandfathered entries are those that can never be legal under those 1069 same provisions. 1071 The set of redundant and grandfathered tags is permanent and stable: 1072 no new entries will be added and none of the entries will be removed. 1073 Records of type 'grandfathered' MAY have their type converted to 1074 'redundant': see Section 3.7 for more information. 1076 RFC 3066 tags that were deprecated prior to the adoption of this 1077 document are part of the list of grandfathered tags and their 1078 component subtags were not included as registered variants (although 1079 they remain eligible for registration). For example, the tag "art- 1080 lojban" was deprecated in favor of the language subtag 'jbo'. 1082 The Language Subtag Reviewer MUST ensure that new subtags meet the 1083 requirements in Section 4.1 or submit an appropriate alternate subtag 1084 as described in that section. If a change or addition to the 1085 registry is needed, the Language Subtag Reviewer will prepare the 1086 complete record, including all fields, and forward it to IANA for 1087 insertion into the registry. If this represents a new subtag, then 1088 the message will indicate that this represents an INSERTION of a 1089 record. If this represents a change to an existing subtag, then the 1090 message MUST indicate that this represents a MODIFICATION, as shown 1091 in the following example: 1093 LANGUAGE SUBTAG MODIFICATION 1094 File-Date: 2005-01-02 1095 %% 1096 Type: variant 1097 Subtag: nedis 1098 Description: Natisone dialect 1099 Description: Nadiza dialect 1100 Added: 2003-10-09 1101 Prefix: sl 1102 Comments: This is a comment shown 1103 as an example. 1104 %% 1106 Figure 6 1108 Whenever an entry is created or modified in the registry, the 'File- 1109 Date' record at the start of the registry is updated to reflect the 1110 most recent modification date in the RFC 3339 [15] "full-date" 1111 format. 1113 Values in the 'Subtag' field MUST be lowercase except as provided for 1114 in Section 3.1. 1116 3.3 Stability of IANA Registry Entries 1118 The stability of entries and their meaning in the registry is 1119 critical to the long term stability of language tags. The rules in 1120 this section guarantee that a specific language tag's meaning is 1121 stable over time and will not change. 1123 These rules specifically deal with how changes to codes (including 1124 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1125 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1126 Subtag Registry. Assignments to the IANA Language Subtag Registry 1127 MUST follow the following stability rules: 1129 o Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1130 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1131 guaranteed to be stable over time. 1133 o Values in the 'Description' field MUST NOT be changed in a way 1134 that would invalidate previously-existing tags. They MAY be 1135 broadened somewhat in scope, changed to add information, or 1136 adapted to the most common modern usage. For example, countries 1137 occasionally change their official names: an historical example of 1138 this would be "Upper Volta" changing to "Burkina Faso". 1140 o Values in the field 'Prefix' MAY be added to records of type 1141 'variant' via the registration process. 1143 o Values in the field 'Prefix' MAY be modified, so long as the 1144 modifications broaden the set of prefixes. That is, a prefix MAY 1145 be replaced by one of its own prefixes. For example, the prefix 1146 "en-US" could be replaced by "en", but not by the prefixes "en- 1147 Latn", "fr", or "en-US-boont". If one of those prefixes were 1148 needed, a new Prefix SHOULD be registered. 1150 o Values in the field 'Prefix' MUST NOT be removed. 1152 o The field 'Comments' MAY be added, changed, modified, or removed 1153 via the registration process or any of the processes or 1154 considerations described in this section. 1156 o The field 'Suppress-Script' MAY be added or removed via the 1157 registration process. 1159 o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1160 conflict with existing subtags of the associated type and whose 1161 meaning is not the same as an existing subtag of the same type are 1162 entered into the IANA registry as new records and their value is 1163 canonical for the meaning assigned to them. 1165 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1166 withdrawn by their respective maintenance or registration 1167 authority remain valid in language tags. A 'Deprecated' field 1168 containing the date of withdrawl is added to the record. If a new 1169 record of the same type is added that represents a replacement 1170 value, then a 'Preferred-Value' field MAY also be added. The 1171 registration process MAY be used to add comments about the 1172 withdrawal of the code by the respective standard. 1174 * The region code 'TL' was assigned to the country 'Timor-Leste', 1175 replacing the code 'TP' (which was assigned to 'East Timor' 1176 when it was under administration by Portugal). The subtag 'TP' 1177 remains valid in language tags, but its record contains the a 1178 'Preferred-Value' of 'TL' and its field 'Deprecated' contains 1179 the date the new code was assigned ('2004-07-06'). 1181 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1182 with existing subtags of the associated type, including subtags 1183 that are deprecated, MUST NOT be entered into the registry. The 1184 following additional considerations apply: 1186 * For ISO 639 codes, if the newly assigned code's meaning is not 1187 represented by a subtag in the IANA registry, the Language 1188 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1189 proposal for entering in the IANA registry as soon as practical 1190 a registered language subtag as an alternate value for the new 1191 code. The form of the registered language subtag will be at 1192 the discretion of the Language Subtag Reviewer and MUST conform 1193 to other restrictions on language subtags in this document. 1195 * For all subtags whose meaning is derived from an external 1196 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if a 1197 new meaning is assigned to an existing code and the new meaning 1198 broadens the meaning of that code, then the meaning for the 1199 associated subtag MAY be changed to match. The meaning of a 1200 subtag MUST NOT be narrowed, however, as this can result in an 1201 unknown proportion of the existing uses of a subtag becoming 1202 invalid. Note: ISO 639 MA/RA has adopted a similar stability 1203 policy. 1205 * For ISO 15924 codes, if the newly assigned code's meaning is 1206 not represented by a subtag in the IANA registry, the Language 1207 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1208 proposal for entering in the IANA registry as soon as practical 1209 a registered variant subtag as an alternate value for the new 1210 code. The form of the registered variant subtag will be at the 1211 discretion of the Language Subtag Reviewer and MUST conform to 1212 other restrictions on variant subtags in this document. 1214 * For ISO 3166 codes, if the newly assigned code's meaning is 1215 associated with the same UN M.49 code as another 'region' 1216 subtag, then the existing region subtag remains as the 1217 preferred value for that region and no new entry is created. A 1218 comment MAY be added to the existing region subtag indicating 1219 the relationship to the new ISO 3166 code. 1221 * For ISO 3166 codes, if the newly assigned code's meaning is 1222 associated with a UN M.49 code that is not represented by an 1223 existing region subtag, then then the Language Subtag Reviewer, 1224 as described in Section 3.4, SHALL prepare a proposal for 1225 entering the appropriate numeric UN country code as an entry in 1226 the IANA registry. 1228 * For ISO 3166 codes, if there is no associated UN numeric code, 1229 then the Language Subtag Reviewer SHALL petition the UN to 1230 create one. If there is no response from the UN within ninety 1231 days of the request being sent, the Language Subtag Reviewer 1232 SHALL prepare a proposal for entering in the IANA registry as 1233 soon as practical a registered variant subtag as an alternate 1234 value for the new code. The form of the registered variant 1235 subtag will be at the discretion of the Language Subtag 1236 Reviewer and MUST conform to other restrictions on variant 1237 subtags in this document. This situation is very unlikely to 1238 ever occur. 1240 o Stability provisions apply to grandfathered tags with this 1241 exception: should all of the subtags in a grandfathered tag become 1242 valid subtags in the IANA registry, then the field 'Type' in that 1243 record is changed from 'grandfathered' to 'redundant'. Note that 1244 this will not affect language tags that match the grandfathered 1245 tag, since these tags will now match valid generative subtag 1246 sequences. For example, if the subtag 'gan' in the language tag 1247 "zh-gan" were to be registered as an extended language subtag, 1248 then the grandfathered tag "zh-gan" would be deprecated (but 1249 existing content or implementations that use "zh-gan" would remain 1250 valid). 1252 3.4 Registration Procedure for Subtags 1254 The procedure given here MUST be used by anyone who wants to use a 1255 subtag not currently in the IANA Language Subtag Registry. 1257 Only subtags of type 'language' and 'variant' will be considered for 1258 independent registration of new subtags. Handling of subtags needed 1259 for stability and subtags necessary to keep the registry synchronized 1260 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1261 defined by this document are described in Section 3.2. Stability 1262 provisions are described in Section 3.3. 1264 This procedure MAY also be used to register or alter the information 1265 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1266 in a subtag's record as described in Figure 9. Changes to all other 1267 fields in the IANA registry are NOT permitted. 1269 Registering a new subtag or requesting modifications to an existing 1270 tag or subtag starts with the requster filling out the registration 1271 form reproduced below. Note that each response is not limited in 1272 size so that the request can adequately describe the registration. 1273 The fields in the "Record Requested" section SHOULD follow the 1274 requirements in Section 3.1. 1276 LANGUAGE SUBTAG REGISTRATION FORM 1277 1. Name of requester: 1278 2. E-mail address of requester: 1279 3. Record Requested: 1281 Type: 1282 Subtag: 1283 Description: 1284 Prefix: 1285 Preferred-Value: 1286 Deprecated: 1287 Suppress-Script: 1288 Comments: 1290 4. Intended meaning of the subtag: 1291 5. Reference to published description 1292 of the language (book or article): 1293 6. Any other relevant information: 1295 Figure 7 1297 The subtag registration form MUST be sent to 1298 for a two week review period before it can 1299 be submitted to IANA. (This is an open list and can be joined by 1300 sending a request to .) 1302 Variant and extlang subtags are always registered for use with a 1303 particular range of language tags. For example, the subtag 'scouse' 1304 is intended for use with language tags that start with the primary 1305 language subtag "en", since Scouse is a dialect of English. Thus the 1306 subtag 'scouse' could be included in tags such as "en-Latn-scouse" or 1307 "en-GB-scouse". This information is stored in the "Prefix" field in 1308 the registry. Variant registration requests are REQUIRED to include 1309 at least one "Prefix" field in the registration form. 1311 The 'Prefix' field for a given registered subtag will be maintained 1312 in the IANA registry as a guide to usage. Additional prefixes MAY be 1313 added by filing an additional registration form. In that form, the 1314 "Any other relevant information:" field MUST indicate that it is the 1315 addition of a prefix. 1317 Requests to add a prefix to a variant subtag that imply a different 1318 semantic meaning will probably be rejected. For example, a request 1319 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1320 nedis" represented some German dialect would be rejected. The 1321 'nedis' subtag represents a particular Slovenian dialect and the 1322 additional registration would change the semantic meaning assigned to 1323 the subtag. A separate subtag SHOULD be proposed instead. 1325 The 'Description' field MUST contain a description of the tag being 1326 registered written or transcribed into the Latin script; it MAY also 1327 include a description in a non-Latin script. Non-ASCII characters 1328 MUST be escaped using the syntax described in Section 3.1. The 1329 'Description' field is used for identification purposes and doesn't 1330 necessarily represent the actual native name of the language or 1331 variation or to be in any particular language. 1333 While the 'Description' field itself is not guaranteed to be stable 1334 and errata corrections MAY be undertaken from time to time, attempts 1335 to provide translations or transcriptions of entries in the registry 1336 itself will probably be frowned upon by the community or rejected 1337 outright, as changes of this nature have an impact on the provisions 1338 in Section 3.3. 1340 The Language Subtag Reviewer is responsible for responding to 1341 requests for the registration of subtags through the registration 1342 process and is appointed by the IESG. 1344 When the two week period has passed the Language Subtag Reviewer 1345 either forwards the record to be inserted or modified to 1346 iana@iana.org according to the procedure described in Section 3.2, or 1347 rejects the request because of significant objections raised on the 1348 list or due to problems with constraints in this document (which MUST 1349 be explicitly cited). The reviewer MAY also extend the review period 1350 in two week increments to permit further discussion. The reviewer 1351 MUST indicate on the list whether the registration has been accepted, 1352 rejected, or extended following each two week period. 1354 Note that the reviewer can raise objections on the list if he or she 1355 so desires. The important thing is that the objection MUST be made 1356 publicly. 1358 The applicant is free to modify a rejected application with 1359 additional information and submit it again; this restarts the two 1360 week comment period. 1362 Decisions made by the reviewer MAY be appealed to the IESG [RFC 2028] 1363 [9] under the same rules as other IETF decisions [RFC 2026] [8]. 1365 All approved registration forms are available online in the directory 1366 http://www.iana.org/numbers.html under "languages". 1368 Updates or changes to existing records, including previous 1369 registrations, follow the same procedure as new registrations. The 1370 Language Subtag Reviewer decides whether there is consensus to update 1371 the registration following the two week review period; normally 1372 objections by the original registrant will carry extra weight in 1373 forming such a consensus. 1375 Registrations are permanent and stable. Once registered, subtags 1376 will not be removed from the registry and will remain a valid way in 1377 which to specify a specific language or variant. 1379 Note: The purpose of the "Description" in the registration form is 1380 intended as an aid to people trying to verify whether a language is 1381 registered or what language or language variation a particular subtag 1382 refers to. In most cases, reference to an authoritative grammar or 1383 dictionary of that language will be useful; in cases where no such 1384 work exists, other well known works describing that language or in 1385 that language MAY be appropriate. The subtag reviewer decides what 1386 constitutes "good enough" reference material. This requirement is 1387 not intended to exclude particular languages or dialects due to the 1388 size of the speaker population or lack of a standardized orthography. 1389 Minority languages will be considered equally on their own merits. 1391 3.5 Possibilities for Registration 1393 Possibilities for registration of subtags or information about 1394 subtags include: 1396 o Primary language subtags for languages not listed in ISO 639 that 1397 are not variants of any listed or registered language can be 1398 registered. At the time this document was created there were no 1399 examples of this form of subtag. Before attempting to register a 1400 language subtag, there MUST be an attempt to register the language 1401 with ISO 639. No language subtags will be registered for codes 1402 that exist in ISO 639-1 or ISO 639-2, which are under 1403 consideration by the ISO 639 maintenance or registration 1404 authorities, or which have never been attempted for registration 1405 with those authorities. If ISO 639 has previously rejected a 1406 language for registration, it is reasonable to assume that there 1407 must be additional very compelling evidence of need before it will 1408 be registered in the IANA registry (to the extent that it is very 1409 unlikely that any subtags will be registered of this type). 1411 o Dialect or other divisions or variations within a language, its 1412 orthography, writing system, regional or historical usage, 1413 transliteration or other transformation, or distinguishing 1414 variation MAY be registered as variant subtags. An example is the 1415 'scouse' subtag (the Scouse dialect of English). 1417 o The addition or maintenance of fields (generally of an 1418 informational nature) in Tag or Subtag records as described in 1419 Section 3.1 and subject to the stability provisions in 1420 Section 3.3. This includes descriptions; comments; deprecation 1421 and preferred values for obsolete or withdrawn codes; or the 1422 addition of script or extlang information to primary language 1423 subtags. 1425 This document leaves the decision on what subtags or changes to 1426 subtags are appropriate (or not) to the registration process 1427 described in Section 3.4. 1429 Note: four character primary language subtags are reserved to allow 1430 for the possibility of alpha4 codes in some future addition to the 1431 ISO 639 family of standards. 1433 ISO 639 defines a maintenance agency for additions to and changes in 1434 the list of languages in ISO 639. This agency is: 1436 International Information Centre for Terminology (Infoterm) 1437 Aichholzgasse 6/12, AT-1120 1438 Wien, Austria 1439 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1441 ISO 639-2 defines a maintenance agency for additions to and changes 1442 in the list of languages in ISO 639-2. This agency is: 1444 Library of Congress 1445 Network Development and MARC Standards Office 1446 Washington, D.C. 20540 USA 1447 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1448 URL: http://www.loc.gov/standards/iso639 1450 The maintenance agency for ISO 3166 (country codes) is: 1452 ISO 3166 Maintenance Agency 1453 c/o International Organization for Standardization 1454 Case postale 56 1455 CH-1211 Geneva 20 Switzerland 1456 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1457 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1459 The registration authority for ISO 15924 (script codes) is: 1461 Unicode Consortium Box 391476 1462 Mountain View, CA 94039-1476, USA 1463 URL: http://www.unicode.org/iso15924 1465 The Statistics Division of the United Nations Secretariat maintains 1466 the Standard Country or Area Codes for Statistical Use and can be 1467 reached at: 1469 Statistical Services Branch 1470 Statistics Division 1471 United Nations, Room DC2-1620 1472 New York, NY 10017, USA 1474 Fax: +1-212-963-0623 1475 E-mail: statistics@un.org 1476 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1478 3.6 Extensions and Extensions Namespace 1480 Extension subtags are those introduced by single-letter subtags other 1481 than 'x'. They are reserved for the generation of identifiers which 1482 contain a language component, and are compatible with applications 1483 that understand language tags. For example, they might be used to 1484 define locale identifiers, which are generally based on language. 1486 The structure and form of extensions are defined by this document so 1487 that implementations can be created that are forward compatible with 1488 applications that might be created using single-letter subtags in the 1489 future. In addition, defining a mechanism for maintaining single- 1490 letter subtags will lend to the stability of this document by 1491 reducing the likely need for future revisions or updates. 1493 Allocation of a single-letter subtag SHALL take the form of an RFC 1494 defining the name, purpose, processes, and procedures for maintaining 1495 the subtags. The maintaining or registering authority, including 1496 name, contact email, discussion list email, and URL location of the 1497 registry MUST be indicated clearly in the RFC. The RFC MUST specify 1498 or include each of the following: 1500 o The specification MUST reference the specific version or revision 1501 of this document that governs its creation and MUST reference this 1502 section of this document. 1504 o The specification and all subtags defined by the specification 1505 MUST follow the ABNF and other rules for the formation of tags and 1506 subtags as defined in this document. In particular it MUST 1507 specify that case is not significant and that subtags MUST NOT 1508 exceed eight characters in length. 1510 o The specification MUST specify a canonical representation. 1512 o The specification of valid subtags MUST be available over the 1513 Internet and at no cost. 1515 o The specification MUST be in the public domain or available via a 1516 royalty-free license acceptable to the IETF and specified in the 1517 RFC. 1519 o The specification MUST be versioned and each version of the 1520 specification MUST be numbered, dated, and stable. 1522 o The specification MUST be stable. That is, extension subtags, 1523 once defined by a specification, MUST NOT be retracted or change 1524 in meaning in any substantial way. 1526 o The specification MUST include in a separate section the 1527 registration form reproduced in this section (below) to be used in 1528 registering the extension upon publication as an RFC. 1530 o IANA MUST be informed of changes to the contact information and 1531 URL for the specification. 1533 IANA will maintain a registry of allocated single-letter (singleton) 1534 subtags. This registry will use the record-jar format described by 1535 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1536 the maintaining authority defined in the RFC MUST forward this 1537 registration form to iesg@ietf.org, who will forward the request to 1538 iana@iana.org. The maintaining authority of the extension MUST 1539 maintain the accuracy of the record by sending an updated full copy 1540 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1541 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1542 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in 1543 these updates. 1545 Failure to maintain this record, the corresponding registry, or meet 1546 other conditions imposed by this section of this document MAY be 1547 appealed to the IESG [RFC 2028] [9] under the same rules as other 1548 IETF decisions (see [8]) and MAY result in the authority to maintain 1549 the extension being withdrawn or reassigned by the IESG. 1551 %% 1552 Identifier: 1553 Description: 1554 Comments: 1555 Added: 1556 RFC: 1557 Authority: 1558 Contact_Email: 1559 Mailing_List: 1560 URL: 1561 %% 1563 Figure 8: Format of Records in the Language Tag Extensions Registry 1565 'Identifier' contains the single letter subtag (singleton) assigned 1566 to the extension. The Internet-Draft submitted to define the 1567 extension SHOULD specify which letter to use, although the IESG MAY 1568 change the assignment when approving the RFC. 1570 'Description' contains the name and description of the extension. 1572 'Comments' is an OPTIONAL field and MAY contain a broader description 1573 of the extension. 1575 'Added' contains the date the RFC was published in the "full-date" 1576 format specified in RFC 3339 [15]. For example: 2004-06-28 1577 represents June 28, 2004, in the Gregorian calendar. 1579 'RFC' contains the RFC number assigned to the extension. 1581 'Authority' contains the name of the maintaining authority for the 1582 extension. 1584 'Contact_Email' contains the email address used to contact the 1585 maintaining authority. 1587 'Mailing_List' contains the URL or subscription email address of the 1588 mailing list used by the maintaining authority. 1590 'URL' contains the URL of the registry for this extension. 1592 The determination of whether an Internet-Draft meets the above 1593 conditions and the decision to grant or withhold such authority rests 1594 solely with the IESG, and is subject to the normal review and appeals 1595 process associated with the RFC process. 1597 Extension authors are strongly cautioned that many (including most 1598 well-formed) processors will be unaware of any special relationships 1599 or meaning inherent in the order of extension subtags. Extension 1600 authors SHOULD avoid subtag relationships or canonicalization 1601 mechanisms that interfere with matching or with length restrictions 1602 that sometimes exist in common protocols where the extension is used. 1603 In particular, applications MAY truncate the subtags in doing 1604 matching or in fitting into limited lengths, so it is RECOMMENDED 1605 that the most significant information be in the most significant 1606 (left-most) subtags, and that the specification gracefully handle 1607 truncated subtags. 1609 When a language tag is to be used in a specific, known, protocol, it 1610 is RECOMMENDED that that the language tag not contain extensions not 1611 supported by that protocol. In addition, note that some protocols 1612 MAY impose upper limits on the length of the strings used to store or 1613 transport the language tag. 1615 3.7 Initialization of the Registry 1617 Upon publication of this document as a BCP, the Language Subtag 1618 Registry MUST be created and populated with the initial set of 1619 subtags. This includes converting the entries from the existing IANA 1620 language tag registry defined by RFC 3066 to the new format. This 1621 section defines the process for defining the new registry and 1622 performing the conversion of the old registry. 1624 The impact on the IANA maintainers of the registry of this conversion 1625 will be a small increase in the frequency of new entries. The 1626 initial set of records represents no impact on IANA, since the work 1627 to create it will be performed externally (as defined in this 1628 section). Future work will be limited to inserting or replacing 1629 whole records preformatted for IANA by the Language Subtag Reviewer. 1631 The initial registry will be created by the LTRU working group. 1632 Using the instructions in this document, the working group will 1633 prepare an Informational RFC by creating a series of Internet-Drafts 1634 containing the prototype registry according to the rules in Sections 1635 4.2.2 and 4.2.3 and subject to IESG review as described in Section 1636 6.1.1 of RFC 2026 [8]. 1638 When the Internet-Draft containing the prototype registry has been 1639 approved by the IESG for publication as an RFC, the document will be 1640 forwarded to IANA, which will post the contents of the new registry 1641 on-line. 1643 Tags in the RFC 3066 registry that are not deprecated that consist 1644 entirely of subtags that are valid under this document and which have 1645 the correct form and format for tags defined by this document are 1646 superseded by this document. Such tags are placed in records of type 1647 'redundant' in the registry. For example, "zh-Hant" is now defined 1648 by this document. 1650 All other tags in the RFC 3066 registry that are deprecated will be 1651 maintained as grandfathered entries. The record for the 1652 grandfathered entry will contain a 'Deprecated' field with the most 1653 appropriate date that can be determined for when the record was 1654 deprecated. The 'Comments' field will contain the reason for the 1655 deprecation. The 'Preferred-Value' field will contain the tag that 1656 replaces the value. For example, the tag "art-lojban" is deprecated 1657 and will be placed in the grandfathered section. It's 'Deprecated' 1658 field will contain the deprecation date (in this case "2003-09-02") 1659 and the 'Preferred-Value' field the value "jbo". 1661 Tags that are not deprecated and which contain subtags which are 1662 consistent with registration under the guidelines in this document 1663 will not automatically have a new subtag registration created for 1664 each eligible subtag. Interrested parties MAY use the registration 1665 process in Section 3.4 to register these subtags. If all of the 1666 subtags in the original tag become fully defined by the resulting 1667 registrations, then the original tag is superseded by this document. 1668 Such tags will have their record changed from type 'grandfathered' to 1669 type 'redundant' in the registry. For example, the subtag 'boont' 1670 could be registered, resulting in the change of the grandfathered tag 1671 "en-boont" to type redundant in the registry. 1673 Tags that contain one or more subtags that do not match the valid 1674 registration pattern and which are not otherwise defined by this 1675 document will have records of type 'grandfathered' created in the 1676 registry. These records cannot become type 'redundant', but MAY have 1677 a 'Deprecated' and 'Prefered-Value' field added to them if a subtag 1678 assignment or combination of assignments renders the tag obsolete. 1680 There MUST be a reasonable period in which the community can comment 1681 on the proposed list entries, which SHALL be no less than four weeks 1682 in length. At the completion of this period, the chair(s) will 1683 notify iana@iana.org and the ltru and ietf-languages mail lists that 1684 the task is complete and forward the necessary materials to IANA for 1685 publication. 1687 Registrations that are in process under the rules defined in RFC 3066 1688 MAY be completed under the former rules, at the discretion of the 1689 language tag reviewer. Any new registrations submitted after the 1690 request for conversion of the registry MUST be rejected. 1692 All existing RFC 3066 language tag registrations will be maintained 1693 in perpetuity. 1695 Users of tags that are grandfathered SHOULD consider registering 1696 appropriate subtags in the IANA subtag registry (but are NOT REQUIRED 1697 to). 1699 UN numeric codes assigned to 'macro-geographical (continental)' or 1700 sub-regions not associated with an assigned ISO 3166 alpha-2 code are 1701 defined in the IANA registry and are valid for use in language tags. 1702 These codes MUST be added to the initial version of the registry. 1703 The UN numeric codes for 'economic groupings' or 'other groupings', 1704 and the alphanumeric codes in Appendix X of the UN document MUST NOT 1705 be added to the registry. 1707 When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49 1708 codes, the following criteria SHALL be applied to the inclusion, 1709 preferred value, and deprecation of codes: 1711 For each standard, the date of the standard referenced in RFC 1766 is 1712 selected as the starting date. Codes that were valid on that date in 1713 the selected standard are added to the registry. Codes that were 1714 previously assigned by but which were vacated or withdrawn before 1715 that date are not added to the registry. For each successive change 1716 to the standard, any additional assignments are added to the 1717 registry. Values that are withdrawn are marked as deprecated, but 1718 not removed. Changes in meaning or assignment of a subtag are 1719 permitted during this process (for example, the ISO 3166 code 'CS' 1720 was originally assigned to 'Czechoslovakia' and is now assigned to 1721 'Serbia and Montenegro'). This continues up to the date that this 1722 document was adopted. The resulting set of records is added to the 1723 registry. Future changes or additions to this portion of the 1724 registry are governed by the provisions of this document. 1726 4. Formation and Processing of Language Tags 1728 This section addresses how to use the registry with the language tag 1729 format to choose, form and process language tags. 1731 4.1 Choice of Language Tag 1733 One is sometimes faced with the choice between several possible tags 1734 for the same body of text. 1736 Interoperability is best served when all users use the same language 1737 tag in order to represent the same language. If an application has 1738 requirements that make the rules here inapplicable, then that 1739 application risks damaging interoperability. It is strongly 1740 RECOMMENDED that users not define their own rules for language tag 1741 choice. 1743 Of particular note, many applications can benefit from the use of 1744 script subtags in language tags, as long as the use is consistent for 1745 a given context. Script subtags were not formally defined in RFC 1746 3066 and their use can affect matching and subtag identification by 1747 implementations of RFC 3066, as these subtags appear between the 1748 primary language and region subtags. For example, if a user requests 1749 content in an implementation of Section 2.5 of RFC 3066 [24] using 1750 the language range "en-US", content labeled "en-Latn-US" will not 1751 match the request. Therefore it is important to know when script 1752 subtags will customarily be used and when they ought not be used. In 1753 the registry, the Suppress-Script field helps ensure greater 1754 compatibility between the language tags generated according to the 1755 rules in this document and language tags and tag processors or 1756 consumers based on RFC 3066 by defining when users SHOULD NOT include 1757 a script subtag with a particular primary language subtag. 1759 Extended language subtags (type 'extlang' in the registry, see 1760 Section 3.1) also appear between the primary language and region 1761 subtags and are reserved for future standardization. Applications 1762 might benefit from their judicious use in forming language tags in 1763 the future. Similar recommendations are expected to apply to their 1764 use as apply to script subtags. 1766 Standards, protocols and applications that reference this document 1767 normatively but apply different rules to the ones given in this 1768 section MUST specify how the procedure varies from the one given 1769 here. 1771 The choice of subtags used to form a language tag SHOULD be guided by 1772 the following rules: 1774 1. Use as precise a tag as possible, but no more specific than is 1775 justified. Avoid using subtags that are not important for 1776 distinguishing content in an application. 1778 * For example, 'de' might suffice for tagging an email written 1779 in German, while "de-CH-1996" is probably unnecessarily 1780 precise for such a task. 1782 2. The script subtag SHOULD NOT be used to form language tags unless 1783 the script adds some distinguishing information to the tag. The 1784 field 'Suppress-Script' in the primary language record in the 1785 registry indicates which script subtags do not add distinguishing 1786 information for most applications. 1788 * For example, the subtag 'Latn' should not be used with the 1789 primary language 'en' because nearly all English documents are 1790 written in the Latin script and it adds no distinguishing 1791 information. However, if a document were written in English 1792 mixing Latin script with another script such as Braille 1793 ('Brai'), then it might be appropriate to choose to indicate 1794 both scripts to aid in content selection, such as the 1795 application of a stylesheet. 1797 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1798 entry, then the value of that field SHOULD be used to form the 1799 language tag in preference to the tag or subtag in which the 1800 preferred value appears. 1802 * For example, use 'he' for Hebrew in preference to 'iw'. 1804 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1805 used to label content, even if the language is unknown. Omitting 1806 the language tag altogether is preferred to using a tag with a 1807 primary language subtag of 'und'. The 'und' subtag MAY be useful 1808 for protocols that require a language tag to be provided. The 1809 'und' subtag MAY also be useful when matching language tags in 1810 certain situations. 1812 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1813 whenever the protocol allows the separate tags for multiple 1814 languages, as is the case for the Content-Language header in 1815 HTTP. The 'mul' subtag conveys little useful information: 1816 content in multiple languages SHOULD individually tag the 1817 languages where they appear or otherwise indicate the actual 1818 language in preference to the 'mul' subtag. 1820 6. The same variant subtag SHOULD NOT be used more than once within 1821 a language tag. 1823 * For example, do not use "en-GB-scouse-scouse". 1825 To ensure consistent backward compatibility, this document contains 1826 several provisions to account for potential instability in the 1827 standards used to define the subtags that make up language tags. 1828 These provisions mean that no language tag created under the rules in 1829 this document will become obsolete. 1831 4.2 Meaning of the Language Tag 1833 The language tag always defines a language as spoken (or written, 1834 signed or otherwise signaled) by human beings for communication of 1835 information to other human beings. Computer languages such as 1836 programming languages are explicitly excluded. 1838 If a language tag B contains language tag A as a prefix, then B is 1839 typically "narrower" or "more specific" than A. For example, "zh- 1840 Hant-TW" is more specific than "zh-Hant". 1842 This relationship is not guaranteed in all cases: specifically, 1843 languages that begin with the same sequence of subtags are NOT 1844 guaranteed to be mutually intelligible, although they might be. For 1845 example, the tag "az" shares a prefix with both "az-Latn" 1846 (Azerbaijani written using the Latin script) and "az-Cyrl" 1847 (Azerbaijani written using the Cyrillic script). A person fluent in 1848 one script might not be able to read the other, even though the text 1849 might be identical. Content tagged as "az" most probably is written 1850 in just one script and thus might not be intelligible to a reader 1851 familiar with the other script. 1853 The relationship between the tag and the information it relates to is 1854 defined by the standard describing the context in which it appears. 1855 Accordingly, this section can only give possible examples of its 1856 usage. 1858 o For a single information object, the associated language tags 1859 might be interpreted as the set of languages that is necessary for 1860 a complete comprehension of the complete object. Example: Plain 1861 text documents. 1863 o For an aggregation of information objects, the associated language 1864 tags could be taken as the set of languages used inside components 1865 of that aggregation. Examples: Document stores and libraries. 1867 o For information objects whose purpose is to provide alternatives, 1868 the associated language tags could be regarded as a hint that the 1869 content is provided in several languages, and that one has to 1870 inspect each of the alternatives in order to find its language or 1871 languages. In this case, the presence of multiple tags might not 1872 mean that one needs to be multi-lingual to get complete 1873 understanding of the document. Example: MIME multipart/ 1874 alternative. 1876 o In markup languages, such as HTML and XML, language information 1877 can be added to each part of the document identified by the markup 1878 structure (including the whole document itself). For example, one 1879 could write C'est la vie. inside a 1880 Norwegian document; the Norwegian-speaking user could then access 1881 a French-Norwegian dictionary to find out what the marked section 1882 meant. If the user were listening to that document through a 1883 speech synthesis interface, this formation could be used to signal 1884 the synthesizer to appropriately apply French text-to-speech 1885 pronunciation rules to that span of text, instead of applying the 1886 inappropriate Norwegian rules. 1888 4.3 Canonicalization of Language Tags 1890 Since a particular language tag is sometimes used by many processes, 1891 language tags SHOULD always be created or generated in a canonical 1892 form. 1894 A language tag is in canonical form when: 1896 1. The tag is well-formed according the rules in Section 2.1 and 1897 Section 2.2. 1899 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1900 the IANA registry (see Section 3.1) SHOULD be replaced with their 1901 mapped value. 1903 3. Redundant or grandfathered tags that have a Preferred-Value 1904 mapping in the IANA registry (see Section 3.1) MUST be replaced 1905 with their mapped value. These items are either deprecated 1906 mappings created before the adoption of this document (such as 1907 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1908 the result of later registrations or additions to this document 1909 (for example, "zh-guoyu" might be mapped to a language-extlang 1910 combination such as "zh-cmn" by some future update of this 1911 document). 1913 4. Other subtags that have a Preferred-Value mapping in the IANA 1914 registry (see Section 3.1) MUST be replaced with their mapped 1915 value. These items consist entirely of clerical corrections to 1916 ISO 639-1 in which the deprecated subtags have been maintained 1917 for compatibility purposes. 1919 5. If more than one extension subtag sequence exists, the extension 1920 sequences are ordered into case-insensitive ASCII order by 1921 singleton subtag. 1923 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1924 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1925 canonical form. 1927 Example: The language tag "en-NH" (English as used in the New 1928 Hebrides) is not canonical because the 'NH' subtag has a canonical 1929 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1930 validity. 1932 Canonicalization of language tags does not imply anything about the 1933 use of upper or lowercase letters when processing or comparing 1934 subtags (and as described in Section 2.1). All comparisons MUST be 1935 performed in a case-insensitive manner. 1937 When performing canonicalization of language tags, processors MAY 1938 regularize the case of the subtags (that is, this process is 1939 OPTIONAL), following the case used in the registry. Note that this 1940 corresponds to the following casing rules: uppercase all non-initial 1941 two-letter subtags; titlecase all non-initial four-letter subtags; 1942 lowercase everything else. 1944 Note: Case folding of ASCII letters in certain locales, unless 1945 carefully handled, sometimes produces non-ASCII character values. 1946 The Unicode Character Database file "SpecialCasing.txt" defines the 1947 specific cases that are known to cause problems with this. In 1948 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1949 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1950 Implementers SHOULD specify a locale-neutral casing operation to 1951 ensure that case folding of subtags does not produce this value, 1952 which is illegal in language tags. For example, if one were to 1953 uppercase the region subtag 'in' using Turkish locale rules, the 1954 sequence U+0130 U+004E would result instead of the expected 'IN'. 1956 Note: if the field 'Deprecated' appears in a registry record without 1957 an accompanying 'Preferred-Value' field, then that tag or subtag is 1958 deprecated without a replacement. Validating processors SHOULD NOT 1959 generate tags that include these values, although the values are 1960 canonical when they appear in a language tag. 1962 An extension MUST define any relationships that exist between the 1963 various subtags in the extension and thus MAY define an alternate 1964 canonicalization scheme for the extension's subtags. Extensions MAY 1965 define how the order of the extension's subtags are interpreted. For 1966 example, an extension could define that its subtags are in canonical 1967 order when the subtags are placed into ASCII order: that is, "en-a- 1968 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1969 define that the order of the subtags influences their semantic 1970 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1971 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1972 so that they are tolerant of the typical processes described in 1973 Section 3.6. 1975 4.4 Considerations for Private Use Subtags 1977 Private-use subtags require private agreement between the parties 1978 that intend to use or exchange language tags that use them and great 1979 caution SHOULD be used in employing them in content or protocols 1980 intended for general use. Private-use subtags are simply useless for 1981 information exchange without prior arrangement. 1983 The value and semantic meaning of private-use tags and of the subtags 1984 used within such a language tag are not defined by this document. 1986 The use of subtags defined in the IANA registry as having a specific 1987 private use meaning convey more information that a purely private use 1988 tag prefixed by the singleton subtag 'x'. For applications this 1989 additional information MAY be useful. 1991 For example, the region subtags 'AA', 'ZZ' and in the ranges 1992 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 1993 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 1994 great deal of public, interchangeable information about the language 1995 material (that it is Chinese in the simplified Chinese script and is 1996 suitable for some geographic region 'XQ'). While the precise 1997 geographic region is not known outside of private agreement, the tag 1998 conveys far more information than an opaque tag such as "x-someLang", 1999 which contains no information about the language subtag or script 2000 subtag outside of the private agreement. 2002 However, in some cases content tagged with private use subtags MAY 2003 interact with other systems in a different and possibly unsuitable 2004 manner compared to tags that use opaque, privately defined subtags, 2005 so the choice of the best approach sometimes depends on the 2006 particular domain in question. 2008 5. IANA Considerations 2010 This section deals with the processes and requirements necessary for 2011 IANA to undertake to maintain the rsubtag and extension registries as 2012 defined by this document and in accordance with the requirements of 2013 RFC 2434 [11]. 2015 The impact on the IANA maintainers of the two registries defined by 2016 this document will be a small increase in the frequency of new 2017 entries or updates. 2019 Upon adoption of this document, the process described in Section 3.7 2020 will be used to generate the initial Language Subtag Registry. The 2021 initial set of records represents no impact on IANA, since the work 2022 to create it will be performed externally (as defined in that 2023 section). The new registry will be listed under "Language Tags" at 2024 . The existing directory of 2025 registration forms and RFC 3066 registrations will be relabeled as 2026 "Language Tags (Obsolete)" and maintained (but not added to or 2027 modified). 2029 Future work on the Language Subtag Registry will be limited to 2030 inserting or replacing whole records preformatted for IANA by the 2031 Language Subtag Reviewer as described in Section 3.2 of this 2032 document. Each record will be sent to iana@iana.org with a subject 2033 line indicating whether the enclosed record is an insertion (of a new 2034 record) or a replacment of an existing record which has a Type and 2035 Subtag (or Tag) field that exactly matches the record sent. Records 2036 cannot be deleted from the registry. 2038 The Language Tag Extensions registry will also be generated and sent 2039 to IANA as described in Section 3.6. This registry can contain at 2040 most 35 records and thus changes to this registry are expected to be 2041 very infrequent. 2043 Future work by IANA on the Language Tag Extensions Registry is 2044 limited to two cases. First, the IESG MAY request that new records 2045 be inserted into this registry from time to time. These requests 2046 will include the record to insert in the exact format described in 2047 Section 3.6. In addition, there MAY be occasional requests from the 2048 maintaining authority for a specific extension to update the contact 2049 information or URLs in the record. These requests MUST include the 2050 complete, updated record. IANA is not responsible for validating the 2051 information provided, only that it is properly formatted. It should 2052 reasonably be seen to come from the maintaining authority named in 2053 the record present in the registry. 2055 6. Security Considerations 2057 Language tags used in content negotiation, like any other information 2058 exchanged on the Internet, might be a source of concern because they 2059 might be used to infer the nationality of the sender, and thus 2060 identify potential targets for surveillance. 2062 This is a special case of the general problem that anything sent is 2063 visible to the receiving party and possibly to third parties as well. 2064 It is useful to be aware that such concerns can exist in some cases. 2066 The evaluation of the exact magnitude of the threat, and any possible 2067 countermeasures, is left to each application protocol (see BCP 72, 2068 RFC 3552 [16] for best current practice guidance on security threats 2069 and defenses). 2071 Since there is no limit to the number of variant, private use, and 2072 extension subtags, and consequently no limit on the possible length 2073 of a tag, implementations need to guard against buffer overflow 2074 attacks. See section Section 2.1.1 for details on language tag 2075 truncation, which can occur as a consequence of defenses against 2076 buffer overflow. 2078 Although the specification of valid subtags for an extension (see: 2079 Section 3.6) MUST be available over the Internet, implementations 2080 SHOULD NOT mechanically depend on it being always accessible, to 2081 prevent denial-of-service attacks. 2083 7. Character Set Considerations 2085 The syntax in this document requires that language tags use only the 2086 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2087 character sets, so the composition of language tags should not have 2088 any character set issues. 2090 Rendering of characters based on the content of a language tag is not 2091 addressed in this memo. Historically, some languages have relied on 2092 the use of specific character sets or other information in order to 2093 infer how a specific character should be rendered (notably this 2094 applies to language and culture specific variations of Han ideographs 2095 as used in Japanese, Chinese, and Korean). When language tags are 2096 applied to spans of text, rendering engines can use that information 2097 in deciding which font to use in the absence of other information, 2098 particularly where languages with distinct writing traditions use the 2099 same characters. 2101 8. Changes from RFC 3066 2103 The main goals for this revision of language tags were the following: 2105 *Compatibility.* All valid RFC 3066 language tags (including those 2106 in the IANA registry) remain valid in this specification. Thus 2107 there is complete backward compatibility of this specification with 2108 existing content. In addition, this document defines language tags 2109 in such as way as to ensure future compatibility, and processors 2110 based solely on the RFC 3066 ABNF (such as those described in XML 2111 Schema version 1.0 [20]) will be able to process tags described by 2112 this document. 2114 *Stability.* Because of the changes in underlying ISO standards, a 2115 valid RFC 3066 language tag may become invalid (or have its meaning 2116 change) at a later date. With so much of the world's computing 2117 infrastructure dependent on language tags, this is simply 2118 unacceptable: it invalidates content that may have an extensive 2119 shelf-life. In this specification, once a language tag is valid, it 2120 remains valid forever. Previously, there was no way to determine 2121 when two tags were equivalent. This specification provides a stable 2122 mechanism for doing so, through the use of canonical forms. These 2123 are also stable, so that implementations can depend on the use of 2124 canonical forms to assess equivalency. 2126 *Validity.* The structure of language tags defined by this document 2127 makes it possible to determine if a particular tag is well-formed 2128 without regard for the actual content or "meaning" of the tag as a 2129 whole. This is important because the registry and underlying 2130 standards change over time. In addition, it must be possible to 2131 determine if a tag is valid (or not) for a given point in time in 2132 order to provide reproducible, testable results. This process must 2133 not be error-prone; otherwise even intelligent people will generate 2134 implementations that give different results. This specification 2135 provides for that by having a single data file, with specific 2136 versioning information, so that the validity of language tags at any 2137 point in time can be precisely determined (instead of interpolating 2138 values from many separate sources). 2140 *Extensibility.* It is important to be able to differentiate between 2141 written forms of language -- for many implementations this is more 2142 important than distinguishing between spoken variants of a language. 2143 Languages are written in a wide variety of different scripts, so this 2144 document provides for the generative use of ISO 15924 script codes. 2145 Like the generative use of ISO language and country codes in RFC 2146 3066, this allows combinations to be produced without resorting to 2147 the registration process. The addition of UN codes provides for the 2148 generation of language tags with regional scope, which is also 2149 required for information technology. 2151 The recast of the registry from containing whole language tags to 2152 subtags is a key part of this. An important feature of RFC 3066 was 2153 that it allowed generative use of subtags. This allows people to 2154 meaningfully use generated tags, without the delays in registering 2155 whole tags, and the burden on the registry of having to supply all of 2156 the combinations that people may find useful. 2158 Because of the widespread use of language tags, it is potentially 2159 disruptive to have periodic revisions of the core specification, 2160 despite demonstrated need. The extension mechanism provides for a 2161 way for independent RFCs to define extensions to language tags. 2162 These extensions have a very constrained, well-defined structure to 2163 prevent extensions from interfering with implementations of language 2164 tags defined in this document. The document also anticipates 2165 features of ISO 639-3 with the addition of the extended language 2166 subtags, as well as the possibility of other ISO 639 parts becoming 2167 useful for the formation of language tags in the future. The use and 2168 definition of private use tags has also been modified, to allow 2169 people to move as much information as possible out of private use 2170 tags, and into the regular structure. The goal is to dramatically 2171 reduce the need to produce a revision of this document in the future. 2173 The specific changes in this document to meet these goals are: 2175 o Defines the ABNF and rules for subtags so that the category of all 2176 subtags can be determined without reference to the registry. 2178 o Adds the concept of well-formed vs. validating processors, 2179 defining the rules by which an implementation can claim to be one 2180 or the other. 2182 o Replaces the IANA language tag registry with a language subtag 2183 registry that provides a complete list of valid subtags in the 2184 IANA registry. This allows for robust implementation and ease of 2185 maintenance. The language subtag registry becomes the canonical 2186 source for forming language tags. 2188 o Provides a process that guarantees stability of language tags, by 2189 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2190 the event that they register a previously used value for a new 2191 purpose. 2193 o Allows ISO 15924 script code subtags and allows them to be used 2194 generatively. Defines a method for indicating in the registry 2195 when script subtags are necessary for a given language tag. 2197 o Adds the concept of a variant subtag and allows variants to be 2198 used generatively. 2200 o Adds the ability to use a class of UN M.49 tags for supra- 2201 national regions and to resolve conflicts in the assignment of ISO 2202 3166 codes. 2204 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2205 as the mechanism for creating private-use language, script, and 2206 region subtags respectively. 2208 o Adds a well-defined extension mechanism. 2210 o Defines an extended language subtag, possibly for use with certain 2211 anticipated features of ISO 639-3. 2213 Ed Note: The following items are provided for the convenience of 2214 reviewers and will be removed from the final document. 2216 Changes between draft-ietf-ltru-registry-02 and this version are: 2218 o Modified the title and some of the front matter of Section 3.7 2219 from "Conversion of the RFC 3066 Language Tag Registry" 2220 (A.Phillips) 2222 o Modified the rules for registry creation so that no variant 2223 registrations are created ab initio. (#922) (J.Cowan) 2225 o Modified the document to replace 'Canonical' with 'Preferred- 2226 Value' and to implement the various design changes necessary to 2227 deal with canonicalization. (#954) (F.Ellermann, A.Phillips, et 2228 al) 2230 o Corrected the ABNF so that 'lang' is defined as 2*4ALPHA (J.Cowan) 2232 o Changed the requirement in Section 2.1.1 on truncation of tags 2233 from MUST to SHOULD and added a sentence about the harm this may 2234 cause. (F.Ellermann, D.Ewell) 2236 o Changed "MUST be very compelling" to "must (etc.)" in Section 3.5. 2237 (R.Presuhn) 2239 o Changed "STRONGLY RECOMMENDED" to "strongly RECOMMENDED" 2240 (R.Presuhn) 2242 o Added sentences pertaining to the File-Date record to Section 3.1. 2243 (#941) (R.Presuhn) 2245 o Changed the process by which the prototype registry is created 2246 from a mere document to an Informational RFC. (#838, #835) (??) 2248 o Changed the Security Considerations (Section 6) and Length 2249 Considerations (Section 2.1.1) sections to address potential 2250 buffer overflow attacks and suggest a lower limit on buffer length 2251 allocation (#944)(#965) (R.Presuhn, I.McDonald) 2253 o Clarified a sentence in Security Considerations (Section 6) to 2254 make clear that it refers to extensions and not the language 2255 subtag registry. (#965) (I.McDonald) 2257 o Added the limitation in the ABNF on the number of extlang subtags 2258 (limited to three) (#965) (R.Presuhn, A.Phillips) 2260 o Added notes to extlang and variant explaining that they should be 2261 used with their Recommended-Prefixes. (A.Phillips) 2263 o Changed the name of the 'Recommended-Prefix' field to 'Prefix' and 2264 the requirements for validating processors to require the prefix 2265 with variants and extlangs. (#1018) (J.Cowan, F.Ellerman) 2267 o Added notes about when variants may be used together and the 2268 relationship of the 'Prefix' field to this in Section 2.2.5 2269 (A.Phillips) 2271 o Specified that 'Prefix' fields may be added only to 'variant' 2272 subtag records and not to 'extlang' records. (J.Cowan) 2274 o Converted lowercase RFC 2119 words to their RFC 2119 normative 2275 equivalent. A few exceptions remain (where the words functioned 2276 in a non-normative fashion). (I.McDonald) 2278 o Rewrote Section 2.1.1 so that it deals with a canonical minimum 2279 maximum length, etc. (#944) 2281 9. References 2283 9.1 Normative References 2285 [1] International Organization for Standardization, "ISO 639- 2286 1:2002, Codes for the representation of names of languages -- 2287 Part 1: Alpha-2 code", ISO Standard 639, 2002. 2289 [2] International Organization for Standardization, "ISO 639-2:1998 2290 - Codes for the representation of names of languages -- Part 2: 2291 Alpha-3 code - edition 1", August 1988. 2293 [3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2294 representation of names of scripts", January 2004. 2296 [4] International Organization for Standardization, "Codes for the 2297 representation of names of countries, 3rd edition", 2298 ISO Standard 3166, August 1988. 2300 [5] Statistical Division, United Nations, "Standard Country or Area 2301 Codes for Statistical Use", UN Standard Country or Area Codes 2302 for Statistical Use, Revision 4 (United Nations publication, 2303 Sales No. 98.XVII.9, June 1999. 2305 [6] International Organization for Standardization, "ISO/IEC 10646- 2306 1:2000. Information technology -- Universal Multiple-Octet 2307 Coded Character Set (UCS) -- Part 1: Architecture and Basic 2308 Multilingual Plane and ISO/IEC 10646-2:2001. Information 2309 technology -- Universal Multiple-Octet Coded Character Set 2310 (UCS) -- Part 2: Supplementary Planes, as, from time to time, 2311 amended, replaced by a new edition or expanded by the addition 2312 of new parts", 2000. 2314 [7] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2315 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 (work 2316 in progress), March 2005. 2318 [8] Bradner, S., "The Internet Standards Process -- Revision 3", 2319 BCP 9, RFC 2026, October 1996. 2321 [9] Hovey, R. and S. Bradner, "The Organizations Involved in the 2322 IETF Standards Process", BCP 11, RFC 2028, October 1996. 2324 [10] Bradner, S., "Key words for use in RFCs to Indicate Requirement 2325 Levels", BCP 14, RFC 2119, March 1997. 2327 [11] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA 2328 Considerations Section in RFCs", BCP 26, RFC 2434, 2329 October 1998. 2331 [12] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 10646", 2332 RFC 2781, February 2000. 2334 [13] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2335 Understanding Concerning the Technical Work of the Internet 2336 Assigned Numbers Authority", RFC 2860, June 2000. 2338 [14] Resnick, P., "Internet Message Format", RFC 2822, April 2001. 2340 [15] Klyne, G. and C. Newman, "Date and Time on the Internet: 2341 Timestamps", RFC 3339, July 2002. 2343 [16] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on 2344 Security Considerations", BCP 72, RFC 3552, July 2003. 2346 9.2 Informative References 2348 [17] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2349 Committee: Working principles for ISO 639 maintenance", 2350 March 2000, 2351 . 2353 [18] Raymond, E., "The Art of Unix Programming", 2003. 2355 [19] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2356 02 2004. 2358 [20] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2359 Datatypes Second Edition", 10 2004, < 2360 http://www.w3.org/TR/xmlschema-2/>. 2362 [21] Unicode Consortium, "The Unicode Consortium. The Unicode 2363 Standard, Version 4.1.0, defined by: The Unicode Standard, 2364 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2365 18578-1), as amended by Unicode 4.0.1 2366 (http://www.unicode.org/versions/Unicode4.0.1) and by Unicode 2367 4.1.0 (http://www.unicode.org/versions/Unicode4.1.0).", 2368 March 2005. 2370 [22] Alvestrand, H., "Tags for the Identification of Languages", 2371 RFC 1766, March 1995. 2373 [23] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word 2374 Extensions: Character Sets, Languages, and Continuations", 2375 RFC 2231, November 1997. 2377 [24] Alvestrand, H., "Tags for the Identification of Languages", 2378 BCP 47, RFC 3066, January 2001. 2380 Authors' Addresses 2382 Addison Phillips (editor) 2383 Quest Software 2385 Email: addison.phillips@quest.com 2387 Mark Davis (editor) 2388 IBM 2390 Email: mark.davis@us.ibm.com 2392 Appendix A. Acknowledgements 2394 Any list of contributors is bound to be incomplete; please regard the 2395 following as only a selection from the group of people who have 2396 contributed to make this document what it is today. 2398 The contributors to RFC 3066 and RFC 1766, the precursors of this 2399 document, made enormous contributions directly or indirectly to this 2400 document and are generally responsible for the success of language 2401 tags. 2403 The following people (in alphabetical order) contributed to this 2404 document or to RFCs 1766 and 3066: 2406 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2407 Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco 2408 Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable, 2409 John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank 2410 Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk- 2411 Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold, 2412 Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent 2413 Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald, 2414 Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George 2415 Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto 2416 Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois 2417 Yergeau and many, many others. 2419 Very special thanks must go to Harald Tveit Alvestrand, who 2420 originated RFCs 1766 and 3066, and without whom this document would 2421 not have been possible. Special thanks must go to Michael Everson, 2422 who has served as language tag reviewer for almost the complete 2423 period since the publication of RFC 1766. Special thanks to Doug 2424 Ewell, for his production of the first complete subtag registry, and 2425 his work in producing a test parser for verifying language tags. 2427 Appendix B. Examples of Language Tags (Informative) 2429 Simple language subtag: 2431 de (German) 2433 fr (French) 2435 ja (Japanese) 2437 i-enochian (example of a grandfathered tag) 2439 Language subtag plus Script subtag: 2441 zh-Hant (Chinese written using the Traditional Chinese script) 2443 zh-Hans (Chinese written using the Simplified Chinese script) 2445 sr-Cyrl (Serbian written using the Cyrillic script) 2447 sr-Latn (Serbian written using the Latin script) 2449 Language-Script-Region: 2451 zh-Hans-CN (Chinese written using the Simlified script as used in 2452 mainland China) 2454 sr-Latn-CS (Serbian written using the Latin script as used in 2455 Serbia and Montenegro) 2457 Language-Variant: 2459 en-boont (Boontling dialect of English) 2461 en-scouse (Scouse dialect of English) 2463 Language-Region-Variant: 2465 en-GB-scouse (Scouse dialect of English as used in the UK) 2467 Language-Script-Region-Variant: 2469 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2470 Latin script as used in Italy. Note that this tag is NOT 2471 RECOMMENDED because subtag 'sl' has a Suppress-Script value of 2472 'Latn') 2474 Language-Region: 2476 de-DE (German for Germany) 2478 en-US (English as used in the United States) 2480 es-419 (Spanish for Latin America and Caribbean region using the 2481 UN region code) 2483 Private-use subtags: 2485 de-CH-x-phonebk 2487 az-Arab-x-AZE-derbend 2489 Extended language subtags (examples ONLY: extended languages MUST be 2490 defined by revision or update to this document): 2492 zh-min 2494 zh-min-nan-Hant-CN 2496 Private-use registry values: 2498 x-whatever (private use using the singleton 'x') 2500 qaa-Qaaa-QM-x-southern (all private tags) 2502 de-Qaaa (German, with a private script) 2504 sr-Latn-QM (Serbian, Latin-script, private region) 2506 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2508 Tags that use extensions (examples ONLY: extensions MUST be defined 2509 by revision or update to this document or by RFC): 2511 en-US-u-islamCal 2513 zh-CN-a-myExt-x-private 2515 en-a-myExt-b-another 2517 Some Invalid Tags: 2519 de-419-DE (two region tags) 2520 a-DE (use of a single character subtag in primary position; note 2521 that there are a few grandfathered tags that start with "i-" that 2522 are valid) 2524 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2525 prefix) 2527 Appendix C. Example Registry 2529 Example Registry 2531 File-Date: 2005-04-18 2532 %% 2533 Type: language 2534 Subtag: aa 2535 Description: Afar 2536 Added: 2004-07-06 2537 %% 2538 Type: language 2539 Subtag: ab 2540 Description: Abkhazian 2541 Added: 2004-07-06 2542 %% 2543 Type: language 2544 Subtag: ae 2545 Description: Avestan 2546 Added: 2004-07-06 2547 %% 2548 Type: language 2549 Subtag: ar 2550 Description: Arabic 2551 Added: 2004-07-06 2552 Suppress-Script: Arab 2553 Comment: Arabic text is usually written in Arabic script 2554 %% 2555 Type: language 2556 Subtag: qaa..qtz 2557 Description: PRIVATE USE 2558 Added: 2004-08-01 2559 Comment: Use private use codes in preference 2560 to the x- singleton for primary language 2561 Comment: This is an example of two comments. 2562 %% 2563 Type: script 2564 Subtag: Arab 2565 Description: Arabic 2566 Added: 2004-07-06 2567 %% 2568 Type: script 2569 Subtag: Armn 2570 Description: Armenian 2571 Added: 2004-07-06 2572 %% 2573 Type: script 2574 Subtag: Bali 2575 Description: Balinese 2576 Added: 2004-07-06 2577 %% 2578 Type: script 2579 Subtag: Batk 2580 Description: Batak 2581 Added: 2004-07-06 2582 %% 2583 Type: region 2584 Subtag: AA 2585 Description: PRIVATE USE 2586 Added: 2004-08-01 2587 %% 2588 Type: region 2589 Subtag: AD 2590 Description: Andorra 2591 Added: 2004-07-06 2592 %% 2593 Type: region 2594 Subtag: AE 2595 Description: United Arab Emirates 2596 Added: 2004-07-06 2597 %% 2598 Type: region 2599 Subtag: AX 2600 Description: Åland Islands 2601 Added: 2004-07-06 2602 Comments: The description shows a Unicode escape 2603 for the letter A-ring. 2604 %% 2605 Type: region 2606 Subtag: 001 2607 Description: World 2608 Added: 2004-07-06 2609 %% 2610 Type: region 2611 Subtag: 002 2612 Description: Africa 2613 Added: 2004-07-06 2614 %% 2615 Type: region 2616 Subtag: 003 2617 Description: North America 2618 Added: 2004-07-06 2619 %% 2620 Type: variant 2621 Subtag: 1901 2622 Description: Traditional German 2623 orthography 2624 Added: 2004-09-09 2625 Prefix: de 2626 Comment: 2627 %% 2628 Type: variant 2629 Subtag: 1996 2630 Description: German orthography of 1996 2631 Added: 2004-09-09 2632 Prefix: de 2633 %% 2634 Type: variant 2635 Subtag: boont 2636 Description: Boontling 2637 Added: 2003-02-14 2638 Prefix: en 2639 %% 2640 Type: variant 2641 Subtag: gaulish 2642 Description: Gaulish 2643 Added: 2001-05-25 2644 Prefix: cel 2645 %% 2646 Type: grandfathered 2647 Tag: art-lojban 2648 Description: Lojban 2649 Added: 2001-11-11 2650 Canonical: jbo 2651 Deprecated: 2003-09-02 2652 %% 2653 Type: grandfathered 2654 Tag: en-GB-oed 2655 Description: English, Oxford English Dictionary spelling 2656 Added: 2003-07-09 2657 %% 2658 Type: grandfathered 2659 Tag: i-ami 2660 Description: 'Amis 2661 Added: 1999-05-25 2662 %% 2663 Type: grandfathered 2664 Tag: i-bnn 2665 Description: Bunun 2666 Added: 1999-05-25 2667 %% 2668 Type: redundant 2669 Tag: az-Arab 2670 Description: Azerbaijani in Arabic script 2671 Added: 2003-05-30 2672 %% 2673 Type: redundant 2674 Tag: az-Cyrl 2675 Description: Azerbaijani in Cyrillic script 2676 Added: 2003-05-30 2677 %% 2679 Figure 9: Example of the Registry Format 2681 Intellectual Property Statement 2683 The IETF takes no position regarding the validity or scope of any 2684 Intellectual Property Rights or other rights that might be claimed to 2685 pertain to the implementation or use of the technology described in 2686 this document or the extent to which any license under such rights 2687 might or might not be available; nor does it represent that it has 2688 made any independent effort to identify any such rights. 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Please address the information to the IETF at 2703 ietf-ipr@ietf.org. 2705 Disclaimer of Validity 2707 This document and the information contained herein are provided on an 2708 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2709 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2710 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2711 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2712 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2713 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2715 Copyright Statement 2717 Copyright (C) The Internet Society (2005). This document is subject 2718 to the rights, licenses and restrictions contained in BCP 78, and 2719 except as set forth therein, the authors retain all their rights. 2721 Acknowledgment 2723 Funding for the RFC Editor function is currently provided by the 2724 Internet Society.