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Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document obsoletes RFC4646, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. -- 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 9, 2008) is 5799 days in the past. Is this intentional? Checking references for intended status: Best Current Practice ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO15924' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO3166-1' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-1' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-2' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-3' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO639-5' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO646' ** Obsolete normative reference: RFC 2028 (Obsoleted by RFC 9281) ** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226) ** Downref: Normative reference to an Informational RFC: RFC 2860 ** Downref: Normative reference to an Informational RFC: RFC 4645 -- Possible downref: Non-RFC (?) normative reference: ref. 'UAX14' -- Obsolete informational reference (is this intentional?): RFC 1766 (Obsoleted by RFC 3066, RFC 3282) -- Obsolete informational reference (is this intentional?): RFC 3066 (Obsoleted by RFC 4646, RFC 4647) -- Obsolete informational reference (is this intentional?): RFC 4646 (Obsoleted by RFC 5646) Summary: 5 errors (**), 0 flaws (~~), 2 warnings (==), 19 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 Lab126 4 Obsoletes: 4646 (if approved) M. Davis, Ed. 5 Intended status: BCP Google 6 Expires: December 11, 2008 June 9, 2008 8 Tags for Identifying Languages 9 draft-ietf-ltru-4646bis-15 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 11, 2008. 36 Abstract 38 This document describes the structure, content, construction, and 39 semantics of language tags for use in cases where it is desirable to 40 indicate the language used in an information object. It also 41 describes how to register values for use in language tags and the 42 creation of user-defined extensions for private interchange. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 47 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 5 48 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 5 49 2.2. Language Subtag Sources and Interpretation . . . . . . . . 8 50 2.2.1. Primary Language Subtag . . . . . . . . . . . . . . . 9 51 2.2.2. Extended Language Subtags . . . . . . . . . . . . . . 11 52 2.2.3. Script Subtag . . . . . . . . . . . . . . . . . . . . 12 53 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 13 54 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 15 55 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 16 56 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 18 57 2.2.8. Grandfathered Registrations . . . . . . . . . . . . . 18 58 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 19 59 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 21 60 3.1. Format of the IANA Language Subtag Registry . . . . . . . 21 61 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 21 62 3.1.2. Record Definitions . . . . . . . . . . . . . . . . . . 22 63 3.1.3. Subtag and Tag Fields . . . . . . . . . . . . . . . . 25 64 3.1.4. Description Field . . . . . . . . . . . . . . . . . . 25 65 3.1.5. Deprecated Field . . . . . . . . . . . . . . . . . . . 27 66 3.1.6. Preferred-Value Field . . . . . . . . . . . . . . . . 27 67 3.1.7. Prefix Field . . . . . . . . . . . . . . . . . . . . . 29 68 3.1.8. Suppress-Script Field . . . . . . . . . . . . . . . . 29 69 3.1.9. Macrolanguage Field . . . . . . . . . . . . . . . . . 30 70 3.1.10. Scope Field . . . . . . . . . . . . . . . . . . . . . 30 71 3.1.11. Comments Field . . . . . . . . . . . . . . . . . . . . 31 72 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 32 73 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 32 74 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 33 75 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 38 76 3.6. Possibilities for Registration . . . . . . . . . . . . . . 42 77 3.7. Extensions and the Extensions Registry . . . . . . . . . . 45 78 3.8. Update of the Language Subtag Registry . . . . . . . . . . 48 79 4. Formation and Processing of Language Tags . . . . . . . . . . 49 80 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 49 81 4.1.1. Tagging Encompassed Languages . . . . . . . . . . . . 53 82 4.1.2. Using Extended Language Subtags . . . . . . . . . . . 53 84 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 55 85 4.3. Lists of Languages . . . . . . . . . . . . . . . . . . . . 57 86 4.4. Length Considerations . . . . . . . . . . . . . . . . . . 58 87 4.4.1. Working with Limited Buffer Sizes . . . . . . . . . . 58 88 4.4.2. Truncation of Language Tags . . . . . . . . . . . . . 59 89 4.5. Canonicalization of Language Tags . . . . . . . . . . . . 60 90 4.6. Considerations for Private Use Subtags . . . . . . . . . . 62 91 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 63 92 5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 63 93 5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 64 94 6. Security Considerations . . . . . . . . . . . . . . . . . . . 66 95 7. Character Set Considerations . . . . . . . . . . . . . . . . . 67 96 8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 68 97 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 72 98 9.1. Normative References . . . . . . . . . . . . . . . . . . . 72 99 9.2. Informative References . . . . . . . . . . . . . . . . . . 73 100 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 75 101 Appendix B. Examples of Language Tags (Informative) . . . . . . . 76 102 Appendix C. Examples of Registration Forms . . . . . . . . . . . 79 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 81 104 Intellectual Property and Copyright Statements . . . . . . . . . . 82 106 1. Introduction 108 Human beings on our planet have, past and present, used a number of 109 languages. There are many reasons why one would want to identify the 110 language used when presenting or requesting information. 112 A user's language preferences often need to be identified so that 113 appropriate processing can be applied. For example, the user's 114 language preferences in a Web browser can be used to select Web pages 115 appropriately. Language preferences can also be used to select among 116 tools (such as dictionaries) to assist in the processing or 117 understanding of content in different languages. 119 In addition, knowledge about the particular language used by some 120 piece of information content might be useful or even required by some 121 types of processing; for example, spell-checking, computer- 122 synthesized speech, Braille transcription, or high-quality print 123 renderings. 125 One means of indicating the language used is by labeling the 126 information content with an identifier or "tag". These tags can be 127 used to specify user preferences when selecting information content, 128 or for labeling additional attributes of content and associated 129 resources. 131 Tags can also be used to indicate additional language attributes of 132 content. For example, indicating specific information about the 133 dialect, writing system, or orthography used in a document or 134 resource may enable the user to obtain information in a form that 135 they can understand, or it can be important in processing or 136 rendering the given content into an appropriate form or style. 138 This document specifies a particular identifier mechanism (the 139 language tag) and a registration function for values to be used to 140 form tags. It also defines a mechanism for private use values and 141 future extension. 143 This document replaces [RFC4646], which replaced [RFC3066] and its 144 predecessor [RFC1766]. For a list of changes in this document, see 145 Section 8. 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 149 document are to be interpreted as described in [RFC2119]. 151 2. The Language Tag 153 Language tags are used to help identify languages, whether spoken, 154 written, signed, or otherwise signaled, for the purpose of 155 communication. This includes constructed and artificial languages, 156 but excludes languages not intended primarily for human 157 communication, such as programming languages. 159 2.1. Syntax 161 The language tag is composed of one or more parts, known as 162 "subtags". Each subtag consists of a sequence of alphanumeric 163 characters. Subtags are distinguished and separated from one another 164 by a hyphen ("-", ABNF [RFC5234] %x2D). Usually a language tag 165 contains a "primary language" subtag, followed by a (possibly empty) 166 series of subsequent subtags, each of which refines or narrows the 167 range of languages identified by the overall tag. 169 Most subtags are distinguished by length, position in the tag, and 170 content: subtags can be recognized solely by these features. This 171 makes it possible to construct a parser that can extract and assign 172 some semantic information to the subtags, even if the specific subtag 173 values are not recognized. Thus, a parser need not have a list of 174 valid tags or subtags (that is, a copy of some version of the IANA 175 Language Subtag Registry) in order to perform common searching and 176 matching operations. The grandfathered tags registered under RFC 177 3066 [RFC3066], a fixed list that can never change, are the only 178 exception to this ability to infer meaning from subtag structure. 180 The syntax of the language tag in ABNF [RFC5234] is: 182 Language-Tag = langtag 183 / privateuse ; private use tag 184 / irregular ; tags grandfathered by rule 186 langtag = (language 187 ["-" script] 188 ["-" region] 189 *("-" variant) 190 *("-" extension) 191 ["-" privateuse]) 193 language = 2*3ALPHA ; shortest ISO 639 code 194 [extlang] ; sometimes followed by 195 ; extended language subtags 196 / 4ALPHA ; reserved for future use 197 / 5*8ALPHA ; registered language subtag 199 extlang = "-" 3ALPHA ; selected ISO 639 codes 200 *2[ "-" 3ALPHA] ; permanently reserved 202 script = 4ALPHA ; ISO 15924 code 204 region = 2ALPHA ; ISO 3166-1 code 205 / 3DIGIT ; UN M.49 code 207 variant = 5*8alphanum ; registered variants 208 / (DIGIT 3alphanum) 210 extension = singleton 1*("-" (2*8alphanum)) 212 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 213 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 214 ; Single alphanumerics 215 ; "x" is reserved for private use 217 privateuse = "x" 1*("-" (1*8alphanum)) 219 irregular = "en-GB-oed" / "i-ami" / "i-bnn" / "i-default" 220 / "i-enochian" / "i-hak" / "i-klingon" / "i-lux" 221 / "i-mingo" / "i-navajo" / "i-pwn" / "i-tao" 222 / "i-tay" / "i-tsu" / "sgn-BE-FR" / "sgn-BE-NL" 223 / "sgn-CH-DE" 225 alphanum = (ALPHA / DIGIT) ; letters and numbers 227 Figure 1: Language Tag ABNF 229 All subtags have a maximum length of eight characters and whitespace 230 is not permitted in a language tag. There is a subtlety in the ABNF 231 production 'variant': variants starting with a digit MAY be four 232 characters long, while those starting with a letter MUST be at least 233 five characters long. For examples of language tags, see Appendix B. 235 Note Well: the ABNF syntax does not distinguish between upper and 236 lowercase. The appearance of upper and lowercase letters in the 237 various ABNF productions above do not affect how implementations 238 interpret tags. That is, the tag "I-AMI" matches the item "i-ami" in 239 the 'irregular' production. At all times, the tags and their 240 subtags, including private use and extensions, are to be treated as 241 case insensitive: there exist conventions for the capitalization of 242 some of the subtags, but these MUST NOT be taken to carry meaning. 244 For example: 246 o [ISO639-1] recommends that language codes be written in lowercase 247 ('mn' Mongolian). 249 o [ISO3166-1] recommends that country codes be capitalized ('MN' 250 Mongolia). 252 o [ISO15924] recommends that script codes use lowercase with the 253 initial letter capitalized ('Cyrl' Cyrillic). 255 However, in the tags defined by this document, the uppercase US-ASCII 256 letters in the range 'A' through 'Z' are considered equivalent and 257 mapped directly to their US-ASCII lowercase equivalents in the range 258 'a' through 'z'. Thus, the tag "mn-Cyrl-MN" is not distinct from 259 "MN-cYRL-mn" or "mN-cYrL-Mn" (or any other combination), and each of 260 these variations conveys the same meaning: Mongolian written in the 261 Cyrillic script as used in Mongolia. 263 Although case distinctions do not carry meaning in language tags, 264 consistent formatting and presentation of the tags will aid users. 265 The format of the tags and subtags in the registry is RECOMMENDED. 266 In this format, all subtags, including all those following singletons 267 (that is, in extension or private-use sequences) are in lowercase. 268 The exceptions to this are: all other non-initial two-letter subtags 269 are uppercase and all other non-initial four-letter subtags are 270 titlecase. 272 Note that although [RFC5234] refers to octets, the language tags 273 described in this document are sequences of characters from the US- 274 ASCII [ISO646] repertoire. Language tags MAY be used in documents 275 and applications that use other encodings, so long as these encompass 276 the relevant part of the US-ASCII repertoire. An example of this 277 would be an XML document that uses the UTF-16LE [RFC2781] encoding of 279 [Unicode]. 281 2.2. Language Subtag Sources and Interpretation 283 The namespace of language tags and their subtags is administered by 284 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 285 the rules in Section 5 of this document. The Language Subtag 286 Registry maintained by IANA is the source for valid subtags: other 287 standards referenced in this section provide the source material for 288 that registry. 290 Terminology used in this document: 292 o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or 293 "az-Arab-IR". Examples of tags in this document are enclosed in 294 double-quotes ("en-US"). 296 o "Subtag" refers to a specific section of a tag, delimited by 297 hyphen, such as the subtag 'Hant' in "zh-Hant-CN". Examples of 298 subtags in this document are enclosed in single quotes ('Hant'). 300 o "Code" refers to values defined in external standards (and which 301 are used as subtags in this document). For example, 'Hant' is an 302 [ISO15924] script code that was used to define the 'Hant' script 303 subtag for use in a language tag. Examples of codes in this 304 document are enclosed in single quotes ('en', 'Hant'). 306 The definitions in this section apply to the various subtags within 307 the language tags defined by this document, excepting those 308 "grandfathered" tags defined in Section 2.2.8. 310 Language tags are designed so that each subtag type has unique length 311 and content restrictions. These make identification of the subtag's 312 type possible, even if the content of the subtag itself is 313 unrecognized. This allows tags to be parsed and processed without 314 reference to the latest version of the underlying standards or the 315 IANA registry and makes the associated exception handling when 316 parsing tags simpler. 318 Subtags in the IANA registry that do not come from an underlying 319 standard can only appear in specific positions in a tag. 320 Specifically, they can only occur as primary language subtags or as 321 variant subtags. 323 Note that sequences of private use and extension subtags MUST occur 324 at the end of the sequence of subtags and MUST NOT be interspersed 325 with subtags defined elsewhere in this document. 327 Single-letter and single-digit subtags are reserved for current or 328 future use. These include the following current uses: 330 o The single-letter subtag 'x' is reserved to introduce a sequence 331 of private use subtags. The interpretation of any private use 332 subtags is defined solely by private agreement and is not defined 333 by the rules in this section or in any standard or registry 334 defined in this document. 336 o All other single-letter subtags are reserved to introduce 337 standardized extension subtag sequences as described in 338 Section 3.7. 340 o The single-letter subtag 'i' is used by some grandfathered tags, 341 such as "i-default", where it always appears in the first position 342 and cannot be confused with an extension. 344 2.2.1. Primary Language Subtag 346 The primary language subtag is the first subtag in a language tag 347 (with the exception of private use and certain grandfathered tags) 348 and cannot be omitted. The following rules apply to the primary 349 language subtag: 351 1. All two-character primary language subtags were defined in the 352 IANA registry according to the assignments found in the standard 353 "ISO 639-1:2002, Codes for the representation of names of 354 languages -- Part 1: Alpha-2 code" [ISO639-1], or using 355 assignments subsequently made by the ISO 639-1 registration 356 authority (RA) or governing standardization bodies. 358 2. All three-character primary language subtags in the IANA registry 359 were defined according to the assignments found in one of these 360 additional ISO 639 parts or assignments subsequently made by the 361 relevant ISO 639 registration authorities or governing 362 standardization bodies: 364 A. "ISO 639-2:1998 - Codes for the representation of names of 365 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2] 367 B. "ISO 639-3:2007 - Codes for the representation of names of 368 languages -- Part 3: Alpha-3 code for comprehensive coverage 369 of languages" [ISO639-3] 371 C. "ISO 639-5:2008 - Codes for the representation of names of 372 languages -- Part 5: Alpha-3 code for language families and 373 groups" [ISO639-5] 375 3. The subtags in the range 'qaa' through 'qtz' are reserved for 376 private use in language tags. These subtags correspond to codes 377 reserved by ISO 639-2 for private use. These codes MAY be used 378 for non-registered primary language subtags (instead of using 379 private use subtags following 'x-'). Please refer to Section 4.6 380 for more information on private use subtags. 382 4. All four-character language subtags are reserved for possible 383 future standardization. 385 5. All language subtags of 5 to 8 characters in length in the IANA 386 registry were defined via the registration process in Section 3.5 387 and MAY be used to form the primary language subtag. At the time 388 this document was created, there were no examples of this kind of 389 subtag and future registrations of this type will be discouraged: 390 primary languages are strongly RECOMMENDED for registration with 391 ISO 639, and proposals rejected by ISO 639/RA-JAC will be closely 392 scrutinized before they are registered with IANA. 394 6. The single-character subtag 'x' as the primary subtag indicates 395 that the language tag consists solely of subtags whose meaning is 396 defined by private agreement. For example, in the tag "x-fr-CH", 397 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 398 French language or the country of Switzerland (or any other value 399 in the IANA registry) unless there is a private agreement in 400 place to do so. See Section 4.6. 402 7. The single-character subtag 'i' is used by some grandfathered 403 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 404 grandfathered tags have a primary language subtag in their first 405 position.) 407 8. Other values MUST NOT be assigned to the primary subtag except by 408 revision or update of this document. 410 Note: For languages that have both an ISO 639-1 two-character code 411 and a three character code (assigned by ISO 639-2, ISO 639-3, or ISO 412 639-5), only the ISO 639-1 two-character code is defined in the IANA 413 registry. 415 Note: For languages that have no ISO 639-1 two-character code and for 416 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 417 (Bibliographic) codes differ, only the Terminology code is defined in 418 the IANA registry. At the time this document was created, all 419 languages that had both kinds of three-character code were also 420 assigned a two-character code; it is expected that future assignments 421 of this nature will not occur. 423 Note: To avoid problems with versioning and subtag choice as 424 experienced during the transition between RFC 1766 and RFC 3066, as 425 well as the canonical nature of subtags defined by this document, the 426 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 427 RA-JAC) has included the following statement in [iso639.prin]: 429 "A language code already in ISO 639-2 at the point of freezing ISO 430 639-1 shall not later be added to ISO 639-1. This is to ensure 431 consistency in usage over time, since users are directed in 432 Internet applications to employ the alpha-3 code when an alpha-2 433 code for that language is not available." 435 In order to avoid instability in the canonical form of tags, if a 436 two-character code is added to ISO 639-1 for a language for which a 437 three-character code was already included in either ISO 639-2 or ISO 438 639-3, the two-character code MUST NOT be registered. See 439 Section 3.4. 441 For example, if some content were tagged with 'haw' (Hawaiian), which 442 currently has no two-character code, the tag would not be invalidated 443 if ISO 639-1 were to assign a two-character code to the Hawaiian 444 language at a later date. 446 Note: An example of independent primary language subtag registration 447 might include: one of the grandfathered IANA registrations is 448 "i-enochian". The subtag 'enochian' could be registered in the IANA 449 registry as a primary language subtag (assuming that ISO 639 does not 450 register this language first), making tags such as "enochian-AQ" and 451 "enochian-Latn" valid. 453 2.2.2. Extended Language Subtags 455 Extended language subtags are used to identify certain specially- 456 selected languages that, for various historical reasons, are closely 457 identified with an existing primary language subtag. Extended 458 language subtags are always used with their enclosing primary 459 language subtag (indicated with a 'Prefix' field in the registry) 460 when used to form the language tag. All languages that have an 461 extended language subtag in the registry also have an identical 462 primary language subtag record in the registry. This primary 463 language subtag is RECOMMENDED for forming the language tag. The 464 following rules apply to the extended language subtags: 466 1. Extended language subtags consist solely of three-letter subtags. 467 All extended language subtag records defined in the registry were 468 defined in the IANA registry according to the assignments found 469 in [ISO639-3]. Language collections and groupings, such as 470 defined in [ISO639-5] are specifically excluded from being 471 extended language subtags. 473 2. Extended language subtag records MUST include exactly one 474 'Prefix' field indicating an appropriate subtag or sequence of 475 subtags for that extended language subtag. 477 3. Extended language subtag records MUST include a 'Preferred-Value' 478 and 'Deprecated' field. The 'Preferred-Value' and 'Subtag' 479 fields MUST be identical. 481 4. Although the ABNF production 'extlang' permits up to three 482 extended language tags in the language tag, extended language 483 subtags MUST NOT include another extended language subtag in 484 their Prefix. That is, the second and third extended language 485 subtag positions in a language tag are permanently reserved and 486 tags that include subtags in that position are invalid. 488 For example, the macrolanguage Chinese ('zh') encompasses a number of 489 languages. For compatibility reasons, each of these languages has 490 both a primary and extended language subtag in the registry. Some 491 examples of these include Gan Chinese ('gan'), Cantonese Chinese 492 ('yue') and Mandarin Chinese ('cmn'). Each is encompassed by the 493 macrolanguage 'zh' (Chinese). Therefore, they each have the prefix 494 "zh" in their registry records. Thus Gan Chinese is represented with 495 tags beginning "zh-gan" or "gan"; Cantonese with tags beginning 496 either "yue" or "zh-yue"; and Mandarin Chinese with "zh-cmn" or 497 "cmn". The language subtag 'zh' can still be used without an 498 extended language subtag to label a resource as some unspecified 499 variety of Chinese, while the primary language subtag ('gan', 'yue', 500 'cmn') is preferred to using the extended language form ("zh-gan", 501 "zh-yue", "zh-cmn"). 503 2.2.3. Script Subtag 505 Script subtags are used to indicate the script or writing system 506 variations that distinguish the written forms of a language or its 507 dialects. The following rules apply to the script subtags: 509 1. Script subtags MUST follow the primary language subtag and MUST 510 precede any other type of subtag. 512 2. All four-character subtags were defined according to 513 [ISO15924]--"Codes for the representation of the names of 514 scripts": alpha-4 script codes, or subsequently assigned by the 515 ISO 15924 registration authority or governing standardization 516 bodies, denoting the script or writing system used in conjunction 517 with this language. 519 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 520 use in language tags. These subtags correspond to codes reserved 521 by ISO 15924 for private use. These codes MAY be used for non- 522 registered script values. Please refer to Section 4.6 for more 523 information on private use subtags. 525 4. Script subtags MUST NOT be registered using the process in 526 Section 3.5 of this document. Variant subtags MAY be considered 527 for registration for that purpose. 529 5. There MUST be at most one script subtag in a language tag, and 530 the script subtag SHOULD be omitted when it adds no 531 distinguishing value to the tag or when the primary language 532 subtag's record includes a Suppress-Script field listing the 533 applicable script subtag. 535 Example: "sr-Latn" represents Serbian written using the Latin script. 537 2.2.4. Region Subtag 539 Region subtags are used to indicate linguistic variations associated 540 with or appropriate to a specific country, territory, or region. 541 Typically, a region subtag is used to indicate regional dialects or 542 usage, or region-specific spelling conventions. A region subtag can 543 also be used to indicate that content is expressed in a way that is 544 appropriate for use throughout a region, for instance, Spanish 545 content tailored to be useful throughout Latin America. 547 The following rules apply to the region subtags: 549 1. Region subtags MUST follow any language or script subtags and 550 MUST precede any other type of subtag. 552 2. All two-character subtags following the primary subtag were 553 defined in the IANA registry according to the assignments found 554 in [ISO3166-1] ("Codes for the representation of names of 555 countries and their subdivisions -- Part 1: Country codes") using 556 the list of alpha-2 country codes, or using assignments 557 subsequently made by the ISO 3166-1 maintenance agency or 558 governing standardization bodies. In addition, the codes that 559 are "exceptionally reserved" (as opposed to "assigned") in ISO 560 3166-1 were also defined in the registry, with the exception of 561 'UK', which is an exact synonym for the assigned code 'GB'. 563 3. All three-character subtags consisting of digit (numeric) 564 characters following the primary subtag were defined in the IANA 565 registry according to the assignments found in UN Standard 566 Country or Area Codes for Statistical Use [UN_M.49] or 567 assignments subsequently made by the governing standards body. 568 Note that not all of the UN M.49 codes are defined in the IANA 569 registry. The following rules define which codes are entered 570 into the registry as valid subtags: 572 A. UN numeric codes assigned to 'macro-geographical 573 (continental)' or sub-regions MUST be registered in the 574 registry. These codes are not associated with an assigned 575 ISO 3166-1 alpha-2 code and represent supra-national areas, 576 usually covering more than one nation, state, province, or 577 territory. 579 B. UN numeric codes for 'economic groupings' or 'other 580 groupings' MUST NOT be registered in the IANA registry and 581 MUST NOT be used to form language tags. 583 C. When ISO 3166-1 reassigns a code formerly used for one 584 country or area to another country or area and that code 585 already is present in the registry, the UN numeric code for 586 that country or area MUST be registered in the registry as 587 described in Section 3.4 and MUST be used to form language 588 tags that represent the country or region for which it is 589 defined (rather than the recycled ISO 3166-1 code). 591 D. UN numeric codes for countries or areas for which there is an 592 associated ISO 3166-1 alpha-2 code in the registry MUST NOT 593 be entered into the registry and MUST NOT be used to form 594 language tags. Note that the ISO 3166-based subtag in the 595 registry MUST actually be associated with the UN M.49 code in 596 question. 598 E. UN numeric codes and ISO 3166-1 alpha-2 codes for countries 599 or areas listed as eligible for registration in [RFC4645] but 600 not presently registered MAY be entered into the IANA 601 registry via the process described in Section 3.5. Once 602 registered, these codes MAY be used to form language tags. 604 F. All other UN numeric codes for countries or areas that do not 605 have an associated ISO 3166-1 alpha-2 code MUST NOT be 606 entered into the registry and MUST NOT be used to form 607 language tags. For more information about these codes, see 608 Section 3.4. 610 4. Note: The alphanumeric codes in Appendix X of the UN document 611 MUST NOT be entered into the registry and MUST NOT be used to 612 form language tags. (At the time this document was created, 613 these values matched the ISO 3166-1 alpha-2 codes.) 615 5. There MUST be at most one region subtag in a language tag and the 616 region subtag MAY be omitted, as when it adds no distinguishing 617 value to the tag. 619 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 620 reserved for private use in language tags. These subtags 621 correspond to codes reserved by ISO 3166 for private use. These 622 codes MAY be used for private use region subtags (instead of 623 using a private use subtag sequence). Please refer to 624 Section 4.6 for more information on private use subtags. 626 "de-AT" represents German ('de') as used in Austria ('AT'). 628 "sr-Latn-RS" represents Serbian ('sr') written using Latin script 629 ('Latn') as used in Serbia ('RS'). 631 "es-419" represents Spanish ('es') appropriate to the UN-defined 632 Latin America and Caribbean region ('419'). 634 2.2.5. Variant Subtags 636 Variant subtags are used to indicate additional, well-recognized 637 variations that define a language or its dialects that are not 638 covered by other available subtags. The following rules apply to the 639 variant subtags: 641 1. Variant subtags MUST follow any language, script, or region 642 subtags, but MUST precede any extension or private use subtag 643 sequences. 645 2. Variant subtags, as a collection, are not associated with any 646 particular external standard. The meaning of variant subtags in 647 the registry is defined in the course of the registration process 648 defined in Section 3.5. Note that any particular variant subtag 649 might be associated with some external standard. However, 650 association with a standard is not required for registration. 652 3. More than one variant MAY be used to form the language tag. 654 4. Variant subtags MUST be registered with IANA according to the 655 rules in Section 3.5 of this document before being used to form 656 language tags. In order to distinguish variants from other types 657 of subtags, registrations MUST meet the following length and 658 content restrictions: 660 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 661 at least five characters long. 663 2. Variant subtags that begin with a digit (0-9) MUST be at 664 least four characters long. 666 5. The same variant subtag MUST NOT be used more than once within a 667 language tag. 669 * For example, the tag "de-DE-1901-1901" is not valid. 671 Variant subtag records in the language subtag registry MAY include 672 one or more 'Prefix' fields. The 'Prefix' indicates a sequence of 673 subtags that would make a suitable prefix (with other subtags, as 674 appropriate) in forming a language tag with the variant. That is, 675 each of the subtags in the prefix SHOULD appear, in order, before the 676 variant. For example, the subtag 'nedis' has a Prefix of "sl", 677 making it suitable for forming language tags such as "sl-nedis" and 678 "sl-IT-nedis", but not suitable for use in a tag such as "zh-nedis" 679 or "it-IT-nedis". 681 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 683 "de-CH-1996" represents German as used in Switzerland and as written 684 using the spelling reform beginning in the year 1996 C.E. 686 Most variants that share a prefix are mutually exclusive. For 687 example, the German orthographic variations '1996' and '1901' SHOULD 688 NOT be used in the same tag, as they represent the dates of different 689 spelling reforms. A variant that can meaningfully be used in 690 combination with another variant SHOULD include a 'Prefix' field in 691 its registry record that lists that other variant. For example, if 692 another German variant 'example' were created that made sense to use 693 with '1996', then 'example' should include two Prefix fields: "de" 694 and "de-1996". 696 2.2.6. Extension Subtags 698 Extensions provide a mechanism for extending language tags for use in 699 various applications. They are intended to identify information 700 which is commonly used in association with languages or language 701 tags, but which is not part of language identification. See 702 Section 3.7. The following rules apply to extensions: 704 1. An extension MUST follow at least a primary language subtag. 705 That is, a language tag cannot begin with an extension. 706 Extensions extend language tags, they do not override or replace 707 them. For example, "a-value" is not a well-formed language tag, 708 while "de-a-value" is. 710 2. Extension subtags are separated from the other subtags defined 711 in this document by a single-character subtag ("singleton"). 712 The singleton MUST be one allocated to a registration authority 713 via the mechanism described in Section 3.7 and MUST NOT be the 714 letter 'x', which is reserved for private use subtag sequences. 716 3. Note: Private use subtag sequences starting with the singleton 717 subtag 'x' are described in Section 2.2.7 below. 719 4. Each singleton subtag MUST appear at most one time in each tag 720 (other than as a private use subtag). That is, singleton 721 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 722 ccc" is invalid because the subtag 'a' appears twice. Note that 723 the tag "en-a-bbb-x-a-ccc" is valid because the second 724 appearance of the singleton 'a' is in a private use sequence. 726 5. Extension subtags MUST meet all of the requirements for the 727 content and format of subtags defined in this document. 729 6. Extension subtags MUST meet whatever requirements are set by the 730 document that defines their singleton prefix and whatever 731 requirements are provided by the maintaining authority. 733 7. Each extension subtag MUST be from two to eight characters long 734 and consist solely of letters or digits, with each subtag 735 separated by a single '-'. 737 8. Each singleton MUST be followed by at least one extension 738 subtag. For example, the tag "tlh-a-b-foo" is invalid because 739 the first singleton 'a' is followed immediately by another 740 singleton 'b'. 742 9. Extension subtags MUST follow all language, script, region, and 743 variant subtags in a tag. 745 10. All subtags following the singleton and before another singleton 746 are part of the extension. Example: In the tag "fr-a-Latn", the 747 subtag 'Latn' does not represent the script subtag 'Latn' 748 defined in the IANA Language Subtag Registry. Its meaning is 749 defined by the extension 'a'. 751 11. In the event that more than one extension appears in a single 752 tag, the tag SHOULD be canonicalized as described in 753 Section 4.5. 755 For example, if the prefix singleton 'r' and the shown subtags were 756 defined, then the following tag would be a valid example: "en-Latn- 757 GB-boont-r-extended-sequence-x-private" 759 2.2.7. Private Use Subtags 761 Private use subtags are used to indicate distinctions in language 762 important in a given context by private agreement. The following 763 rules apply to private use subtags: 765 1. Private use subtags are separated from the other subtags defined 766 in this document by the reserved single-character subtag 'x'. 768 2. Private use subtags MUST conform to the format and content 769 constraints defined in the ABNF for all subtags. 771 3. Private use subtags MUST follow all language, script, region, 772 variant, and extension subtags in the tag. Another way of saying 773 this is that all subtags following the singleton 'x' MUST be 774 considered private use. Example: The subtag 'US' in the tag "en- 775 x-US" is a private use subtag. 777 4. A tag MAY consist entirely of private use subtags. 779 5. No source is defined for private use subtags. Use of private use 780 subtags is by private agreement only. 782 6. Private use subtags are NOT RECOMMENDED where alternatives exist 783 or for general interchange. See Section 4.6 for more information 784 on private use subtag choice. 786 For example: The Unicode Consortium defines a set of private use 787 extensions in LDML ([UTS35], Locale Data Markup Language, the Unicode 788 standard for defining locale data) such as in the tag "es-419-x-ldml- 789 collatio-traditio", which indicates Latin American Spanish with 790 traditional order for sorted lists. 792 2.2.8. Grandfathered Registrations 794 Prior to RFC 4646, whole language tags were registered according to 795 the rules in RFC 1766 and/or RFC 3066. These registered tags 796 maintain their validity. Of those tags, those that were made 797 obsolete or redundant by the advent of RFC 4646, by this document, or 798 by subsequent registration of subtags are maintained in the registry 799 in records as "redundant" records. Those tags that do not match the 800 'langtag' production in the ABNF in this document or that contain 801 subtags that do not individually appear in the registry are 802 maintained in the registry in records of the "grandfathered" type. 804 Grandfathered tags contain one or more subtags that are not defined 805 in the Language Subtag Registry (see Section 3). Redundant tags 806 consist entirely of subtags defined above and whose independent 807 registration was superseded by [RFC4646]. For more information see 808 Section 3.8. 810 Some grandfathered tags are "regular" in that they match the 811 'langtag' production in Figure 1. In some cases, these tags could 812 become redundant if their (currently unregistered) subtags were to be 813 registered (as variants, for example). In other cases, although the 814 subtags match the language tag pattern, the meaning assigned to the 815 various subtags is prohibited by rules elsewhere in this document. 816 Those tags can never become redundant. 818 The remaining grandfathered tags are "irregular" and do not match the 819 'langtag' production. These are listed in the 'irregular' production 820 in Figure 1. These grandfathered tags can never become redundant. 821 Many of these tags have been superseded by other registrations: their 822 record contains a Preferred-Value field that really ought to be used 823 to form language tags representing that value. 825 2.2.9. Classes of Conformance 827 Implementations sometimes need to describe their capabilities with 828 regard to the rules and practices described in this document. Tags 829 can be checked or verified in a number of ways, but two particular 830 classes of tag conformance are formally defined here. 832 A tag is considered "well-formed" if it conforms to the ABNF 833 (Section 2.1). Language tags may be well-formed in terms of syntax 834 but not valid in terms of content. Irregular grandfathered tags are 835 now listed in the 'irregular' production. 837 A tag is considered "valid" if it satisfies these conditions: 839 o The tag is well-formed. 841 o The tag is either a grandfathered tag, or all of its language, 842 extlang, script, region, and variant subtags appear in the IANA 843 language subtag registry as of the particular registry date. 845 o There are no duplicate singleton (extension) subtags and no 846 duplicate variant subtags. 848 Note that a tag's validity depends on the date of the registry used 849 to validate the tag. A more recent copy of the registry might 850 contain a subtag that an older version does not. 852 A tag is considered "valid" for a given extension (Section 3.7) (as 853 of a particular version, revision, and date) if it meets the criteria 854 for "valid" above and also satisfies this condition: 856 Each subtag used in the extension part of the tag is valid 857 according to the extension. 859 Older language tag implementations sometimes reference [RFC3066]. 860 Again, all valid tags under that version also match this document's 861 language tag ABNF. However, a wider array of tags could be 862 considered "well-formed" under that document. The 'Language-Tag' 863 production used in that document matches the following: 865 obs-language-tag = primary-subtag *( "-" subtag ) 866 primary-subtag = 1*8ALPHA 867 subtag = 1*8(ALPHA / DIGIT) 869 Figure 2: RFC 3066 Language Tag Syntax 871 Subtags designated for private use or private-use sequences 872 introduced by the 'x' subtag are available for cases in which no 873 assigned subtags are available and registration is not a suitable 874 option. For example, one might use a tag such as "no-QQ", where 'QQ' 875 is one of a range of private-use ISO 3166-1 codes to indicate an 876 otherwise-undefined region. Users MUST NOT assign and use subtags 877 that do not appear in the registry other than in private-use 878 sequences (such the subtag 'personal' in the tag "en-x-personal"). 879 Not only is such assignment nonconformant, it also risks collision 880 with a future possible assignment or registration. 882 Note well: although the 'Language-Tag' production appearing in this 883 document is functionally equivalent to the one in [RFC4646], it has 884 been changed to prevent certain errors in well-formedness arising 885 from the old 'grandfathered' production. This version of the ABNF is 886 RECOMMENDED as a replacement for the older version. 888 3. Registry Format and Maintenance 890 This section defines the Language Subtag Registry and the maintenance 891 and update procedures associated with it, as well as a registry for 892 extensions to language tags (Section 3.7). 894 The Language Subtag Registry contains a comprehensive list of all of 895 the subtags valid in language tags. This allows implementers a 896 straightforward and reliable way to validate language tags. The 897 Language Subtag Registry will be maintained so that, except for 898 extension subtags, it is possible to validate all of the subtags that 899 appear in a language tag under the provisions of this document or its 900 revisions or successors. In addition, the meaning of the various 901 subtags will be unambiguous and stable over time. (The meaning of 902 private use subtags, of course, is not defined by the IANA registry.) 904 3.1. Format of the IANA Language Subtag Registry 906 The IANA Language Subtag Registry ("the registry") is a machine- 907 readable file in the format described in this section, plus copies of 908 the registration forms approved in accordance with the process 909 described in Section 3.5. 911 Note: The existing registration forms for grandfathered and redundant 912 tags taken from RFC 3066 have been maintained as part of the obsolete 913 RFC 3066 registry. The subtags added to the registry by either 914 [RFC4645] or [registry-update] do not have separate registration 915 forms (so no forms are archived for these additions). 917 3.1.1. File Format 919 The registry consists of a series of records stored in the record-jar 920 format (described in [record-jar]). Each record, in turn, consists 921 of a series of fields that describe the various subtags and tags. 922 The registry is a Unicode [Unicode] text file, using the UTF-8 923 [RFC3629] character encoding. 925 Each field can be considered a single, logical line of Unicode 926 [Unicode] characters, comprising a field-name and a field-body 927 separated by a COLON character (%x3A). Each field is terminated by 928 the newline sequence CRLF. The text in each field MUST be in Unicode 929 Normalization Form C (NFC). 931 A collection of fields forms a 'record'. Records are separated by 932 lines containing only the sequence "%%" (%x25.25). 934 Although fields are logically a single line of text, each line of 935 text in the file format is limited to 72 bytes in length. To 936 accommodate this, the field-body can be split into a multiple-line 937 representation; this is called "folding". Folding is done according 938 to customary conventions for line-wrapping. This is typically on 939 whitespace boundaries, but can occur between other characters when 940 the value does not include spaces, such as when a language does not 941 use whitespace between words. In any event, there MUST NOT be breaks 942 inside a multibyte UTF-8 sequence nor in the middle of a combining 943 character sequence. For more information, see [UAX14]. 945 Although the file format uses the UTF-8 encoding fields are 946 restricted to the printable characters from the US-ASCII [ISO646] 947 repertoire unless otherwise indicated in the specific field 948 description below. 950 The format of the registry is described by the following ABNF (per 951 [RFC5234]): 953 registry = record *("%%" CRLF record) 954 record = 1*( field-name *SP ":" *SP field-body CRLF ) 955 field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] 956 field-body = *([[*SP CRLF] 1*SP] 1*CHARS) 957 CHARS = (%x21-10FFFF) ; Unicode code points 959 Figure 3: Registry Format ABNF 961 The sequence '..' (%x2E.2E) in a field-body denotes a range of 962 values. Such a range represents all subtags of the same length that 963 are in alphabetic or numeric order within that range, including the 964 values explicitly mentioned. For example 'a..c' denotes the values 965 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 966 '13'. 968 All fields whose field-body contains a date value use the "full-date" 969 format specified in [RFC3339]. For example: "2004-06-28" represents 970 June 28, 2004, in the Gregorian calendar. 972 3.1.2. Record Definitions 974 There are three types of records in the registry: "File-Date", 975 "Subtag", and "Tag" records. 977 The first record in the registry is a "File-Date" record. This 978 record contains the single field whose field-name is "File-Date" (see 979 Figure 3). The field-body of this record contains the last 980 modification date of this copy of the registry, making it possible to 981 compare different versions of the registry. The registry on the IANA 982 website is the most current. Versions with an older date than that 983 one are not up-to-date. 985 File-Date: 2004-06-28 986 %% 988 Figure 4: Example of the File-Date Record 990 Subsequent records represent either subtags or tags in the registry. 991 "Subtag" records contain a field with a field-name of "Subtag", 992 while, unsurprisingly, "Tag" records contain a field with a field- 993 name of "Tag". Each of the fields in each record MUST occur no more 994 than once, unless otherwise noted below. Each record MUST contain 995 the following fields: 997 o 'Type' 999 * Type's field-body MUST consist of one of the following strings: 1000 "language", "extlang", "script", "region", "variant", 1001 "grandfathered", and "redundant" and denotes the type of tag or 1002 subtag. 1004 o Either 'Subtag' or 'Tag' 1006 * Subtag's field-body contains the subtag being defined. This 1007 field MUST only appear in records of whose 'Type' has one of 1008 these values: "language", "extlang", "script", "region", or 1009 "variant". 1011 * Tag's field-body contains a complete language tag. This field 1012 MUST only appear in records whose 'Type' has one of these 1013 values: "grandfathered" or "redundant". Note that the field- 1014 body will always follow the 'grandfathered' production in the 1015 ABNF in Section 2.1 1017 o Description 1019 * Description's field-body contains a non-normative description 1020 of the subtag or tag. 1022 o Added 1024 * Added's field-body contains the date the record was registered 1025 or, in the case of grandfathered or redundant tags, the date 1026 the corresponding tag was registered under the rules of 1027 [RFC1766] or [RFC3066]. 1029 Each record MAY also contain the following fields: 1031 o Preferred-Value 1032 * Preferred-Value's field body contains a canonical mapping from 1033 this record's value to a modern equivalent that is preferred in 1034 it's place. Depending on the value of the 'Type' field, this 1035 value can take different forms: 1037 + For fields of type 'language', 'Preferred-Value' contains 1038 the primary language subtag that is preferred when forming 1039 the language tag. 1041 + For fields of type 'script', 'region', or 'variant', 1042 'Preferred-Value' contains the subtag of the same 'Type' 1043 that is preferred for forming the language tag. 1045 + For fields of type 'extlang', 'grandfathered', or 1046 'redundant', 'Preferred-Value' contains an extended language 1047 range that is preferred for forming the language tag. That 1048 is, each of the subtags that appears in the value MUST 1049 appear in the replacement tag; additional fields can be 1050 included in a language tag as described elsewhere in this 1051 document. For example, the replacement for the 1052 grandfathered tag "zh-min-nan" (Min Nan Chinese) is "zh- 1053 nan", which can be used as the basis for tags such as "zh- 1054 nan-Hant" or "zh-nan-TW". 1056 o Deprecated 1058 * Deprecated's field-body contains the date the record was 1059 deprecated. In some cases this value is before that of the 1060 associated 'Added' field in the registry. 1062 o Prefix 1064 * Prefix's field-body contains a language tag with which this 1065 subtag MAY be used to form a new language tag, perhaps with 1066 other subtags as well. The Prefix's subtags appear before the 1067 subtag. This field MUST only appear in records whose 'Type' 1068 field-body is either 'extlang' or 'variant'. For example, the 1069 'Prefix' for the variant 'nedis' is 'sl', meaning that the tags 1070 "sl-nedis" and "sl-IT-nedis" are appropriate while the tag "is- 1071 nedis" is not. 1073 o Comments 1075 * Comments's field-body contains additional information about the 1076 subtag, as deemed appropriate for understanding the registry 1077 and implementing language tags using the subtag or tag. 1079 o Suppress-Script 1081 * Suppress-Script's field-body contains a script subtag that 1082 SHOULD NOT be used to form language tags with the associated 1083 primary language subtag. This field MUST only appear in 1084 records whose 'Type' field-body is 'language'. See 1085 Section 4.1. 1087 o Macrolanguage 1089 * Macrolanguage's field-body contains a primary language subtag 1090 defined by ISO 639 as a "macrolanguage" that encompasses this 1091 language subtag. This field MUST only appear in records whose 1092 'Type' field-body is either 'language' or 'extlang'. 1094 o Scope 1096 * Scope's field-body contains information about a primary or 1097 extended language subtag indicating its type according to ISO 1098 639. The values permitted in this field are 'individual', 1099 'macrolanguage', 'collection', or 'special'. This field MUST 1100 only appear in records whose 'Type' field-body is either 1101 'language' or 'extlang'. 1103 Future versions of this document might add additional fields to the 1104 registry, so implementations SHOULD ignore fields found in the 1105 registry that are not defined in this document. 1107 3.1.3. Subtag and Tag Fields 1109 The 'Subtag' field MUST NOT use uppercase letters to form the subtag, 1110 with two exceptions. Subtags whose 'Type' field is 'script' (in 1111 other words, subtags defined by ISO 15924) MUST use titlecase. 1112 Subtags whose 'Type' field is 'region' (in other words, the non- 1113 numeric region subtags defined by ISO 3166-1) MUST use all uppercase. 1114 These exceptions mirror the use of case in the underlying standards. 1116 Each subtag in the tags contained in a 'Tag' field MUST be formatted 1117 using the rules in the preceding paragraph. That is, all subtags are 1118 lowercase except for subtags that represent script or region codes. 1120 3.1.4. Description Field 1122 The field 'Description' contains a description of the tag or subtag 1123 in the record. The 'Description' field MAY appear more than once per 1124 record, that is, there can be multiple descriptions for a given 1125 record. The 'Description' field MAY include the full range of 1126 Unicode characters. At least one of the 'Description' fields MUST be 1127 written or transcribed into the Latin script; additional 1128 'Description' fields MAY also include a description in a non-Latin 1129 script. Each 'Description' field MUST be unique, both within the 1130 record in which it appears and for the collection of records of the 1131 same type. Moreover, formatting variations of the same description 1132 MUST NOT occur in that specific record or in any other record of the 1133 same type. For example, while the ISO 639-1 code 'fy' contains both 1134 the descriptions "Western Frisian" and "Frisian, Western", only one 1135 of these descriptions appears in the registry. 1137 The 'Description' field is used for identification purposes. It 1138 doesn't necessarily represent the actual native name of the item in 1139 the record, nor are any of the descriptions guaranteed to be in any 1140 particular language (such as English or French, for example). 1142 For subtags taken from a source standard (such as ISO 639 or ISO 1143 15924), the 'Description' value(s) SHOULD also be taken from the 1144 source standard. Multiple descriptions in the source standard MUST 1145 be split into separate 'Description' fields. The source standard's 1146 descriptions MAY be edited, either prior to insertion or via the 1147 registration process. For fields of type 'language', the first 1148 'Description' field appearing in the Registry corresponds whenever 1149 possible to the Reference Name assigned by ISO 639-3. This helps 1150 facilitate cross-referencing between ISO 639 and the registry. 1152 When creating or updating a record due to the action of one of the 1153 source standards, the Language Subtag Reviewer SHOULD remove 1154 duplicate or redundant descriptions and MAY edit descriptions to 1155 correct irregularities in formatting (such as misspellings, 1156 inappropriate apostrophes or other punctuation, or excessive or 1157 missing spaces) prior to submitting the proposed record to the ietf- 1158 languages list. 1160 Note: Descriptions in registry entries that correspond to ISO 639, 1161 ISO 15924, ISO 3166-1, or UN M.49 codes are intended only to indicate 1162 the meaning of that identifier as defined in the source standard at 1163 the time it was added to the registry. The description does not 1164 replace the content of the source standard itself. The descriptions 1165 are not intended to be the localized English names for the subtags. 1166 Localization or translation of language tag and subtag descriptions 1167 is out of scope of this document. 1169 Descriptions SHOULD contain all and only that information necessary 1170 to distinguish one subtag from others that it might be confused with. 1171 They are not intended to provide general background information, nor 1172 to provide all possible alternate names or designations. 1174 3.1.5. Deprecated Field 1176 The field 'Deprecated' MAY be added, changed, or removed from any 1177 record via the maintenance process described in Section 3.3 or via 1178 the registration process described in Section 3.5. Usually, the 1179 addition of a 'Deprecated' field is due to the action of one of the 1180 standards bodies, such as ISO 3166, withdrawing a code. Although 1181 valid in language tags, subtags and tags with a 'Deprecated' field 1182 are deprecated and validating processors SHOULD NOT generate these 1183 subtags. Note that a record that contains a 'Deprecated' field and 1184 no corresponding 'Preferred-Value' field has no replacement mapping. 1186 In some historical cases, it might not have been possible to 1187 reconstruct the original deprecation date. For these cases, an 1188 approximate date appears in the registry. Some subtags and some 1189 grandfathered or redundant tags were deprecated before the initial 1190 creation of the registry. The exact rules for this appear in Section 1191 2 of [RFC4645]. Note that these records have a 'Deprecated' field 1192 with an earlier date then the corresponding 'Added' field! 1194 3.1.6. Preferred-Value Field 1196 The field 'Preferred-Value' contains a mapping between the record in 1197 which it appears and another tag or subtag. The value in this field 1198 is strongly RECOMMENDED as the best choice to represent the value of 1199 this record when selecting a language tag. These values form three 1200 groups: 1202 1. ISO 639 language codes that were later withdrawn in favor of 1203 other codes. These values are mostly a historical curiosity. 1205 2. Subtags (other than language codes) taken from codes or values 1206 that have been withdrawn in favor of a new code. In particular, 1207 this applies to region subtags taken from ISO 3166-1, because 1208 sometimes a country will change its name or administration in 1209 such a way that warrants a new region code. In some cases, 1210 countries have reverted to an older name, which might already be 1211 encoded. 1213 3. Tags or subtags that have become obsolete because the values they 1214 represent were later encoded. Many of the grandfathered or 1215 redundant tags were later encoded by ISO 639, for example, and 1216 fit this pattern. 1218 Records that contain a 'Preferred-Value' field MUST also have a 1219 'Deprecated' field. This field contains the date on which the tag or 1220 subtag was deprecated in favor of the preferred value. 1222 Note that 'Preferred-Value' mappings in records of type 'region' 1223 sometimes do not represent exactly the same meaning as the original 1224 value. There are many reasons for a country code to be changed, and 1225 the effect this has on the formation of language tags will depend on 1226 the nature of the change in question. 1228 A 'Preferred-Value' MAY be added to, changed, or removed from records 1229 according to the rules in Section 3.3. Addition, modification, or 1230 removal of a 'Preferred-Value' field in a record does not imply that 1231 content using the affected subtag needs to be retagged. 1233 The 'Preferred-Value' field in records of type "grandfathered" and 1234 "redundant" contains language ranges that are strongly RECOMMENDED 1235 for use in place of the record's value. In many cases, these 1236 mappings were created via deprecation of the tags during the period 1237 before [RFC4646] was adopted. For example, the tag "no-nyn" was 1238 deprecated in favor of the ISO 639-1-defined language code 'nn'. 1240 The 'Preferred-Value' field in subtag records of type "extlang" use 1241 the same format as grandfathered or redundant tags. This allows the 1242 subtag to be deprecated in favor of either a single primary language 1243 subtag or a new language-extlang sequence. 1245 Usually the addition, removal, or change of a Preferred-Value field 1246 for a subtag is done to reflect changes in one of the source 1247 standards. For example, if an ISO 3166-1 region code is deprecated 1248 in favor of another code, that SHOULD result in the addition of a 1249 Preferred-Value field. 1251 Changes to one subtag MAY affect other subtags as well: when 1252 proposing changes to the registry, the Language Subtag Reviewer will 1253 review the registry for such effects and propose the necessary 1254 changes using the process in Section 3.5, although anyone MAY request 1255 such changes. For example: 1257 Suppose that subtag 'XX' has a Preferred-Value of 'YY'. If 'YY' 1258 later changes to have a Preferred-Value of 'ZZ', then the 1259 Preferred-Value for 'XX' MUST also change to be 'ZZ'. 1261 Suppose that a registered language subtag 'dialect' represents a 1262 language not yet available in any part of ISO 639. The later 1263 addition of a corresponding language code in ISO 639 SHOULD result 1264 in the addition of a Preferred-Value for 'dialect'. 1266 3.1.7. Prefix Field 1268 The 'Prefix' field contains an extended language range whose subtags 1269 are appropriate to use with this subtag: each of the subtags in one 1270 of the subtag's Prefix fields SHOULD appear before the variant in a 1271 valid tag. For example, the variant subtag '1996' has a 'Prefix' 1272 field of "de". This means that tags starting with the sequence "de-" 1273 are appropriate with this subtag, so "de-Latg-1996" and "de-CH-1996" 1274 are both acceptable, while the tag "fr-1996" is an inappropriate 1275 choice. 1277 The field of type 'Prefix' MUST NOT be removed from any record. The 1278 field-body for this type of field MAY be modified, but only if the 1279 modification broadens the meaning of the subtag. That is, the field- 1280 body can be replaced only by a prefix of itself. For example, the 1281 Prefix "be-Latn" (Belarusian, Latin script) could be replaced by the 1282 Prefix "be" (Belarusian) but not by the Prefix "ru-Latn" (Russian, 1283 Latin script). 1285 Records of type 'variant' MAY have more than one field of type 1286 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1287 record via the registration process. Fields of type 'extlang' MUST 1288 have exactly one Prefix field. 1290 The field-body of the 'Prefix' field MUST NOT conflict with any 1291 'Prefix' already registered for a given record. Such a conflict 1292 would occur when no valid tag could be constructed that would contain 1293 the prefix, such as when two subtags each have a 'Prefix' that 1294 contains the other subtag. For example, suppose that the subtag 1295 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' 1296 cannot given the prefix 'avariant', for that would require a tag of 1297 the form "es-avariant-bvariant-avariant", which would not be valid. 1299 3.1.8. Suppress-Script Field 1301 The field 'Suppress-Script' contains a script subtag (whose record 1302 appears in the registry). The field 'Suppress-Script' MUST only 1303 appear in records whose 'Type' field-body is 'language'. This field 1304 MUST NOT appear more than one time in a record. This field indicates 1305 a script used to write the overwhelming majority of documents for the 1306 given language. This script code therefore adds no distinguishing 1307 information to a language tag. This helps ensure greater 1308 compatibility between the language tags generated according to the 1309 rules in this document and language tags and tag processors or 1310 consumers based on RFC 3066 by indicating that the script subtag 1311 SHOULD NOT be used for most documents in that language. For example, 1312 virtually all Icelandic documents are written in the Latin script, 1313 making the subtag 'Latn' redundant in the tag "is-Latn". 1315 Many language subtag records do not have a Suppress-Script field. 1316 The lack of a Suppress-Script might indicate that the language is 1317 customarily written in more than one script or that the language is 1318 not customarily written at all. It might also mean that sufficient 1319 information was not available when the record was created and thus 1320 remains a candidate for future registration. 1322 3.1.9. Macrolanguage Field 1324 The field 'Macrolanguage' contains a primary language subtag (whose 1325 record appears in the registry). This field indicates a language 1326 that encompasses this subtag's language according to assignments made 1327 by ISO 639-3. 1329 ISO 639-3 labels some languages in the registry as "macrolanguages". 1330 ISO 639-3 defines the term "Macrolanguage" to mean "clusters of 1331 closely-related language varieties that [...] can be considered 1332 distinct individual languages, yet in certain usage contexts a single 1333 language identity for all is needed". These correspond to codes 1334 registered in ISO 639-2 as individual languages that were found to 1335 correspond to more than one language in ISO 639-3. 1337 A language contained within a macrolanguage is called an "encompassed 1338 language". The record for each encompassed language contains a 1339 'Macrolanguage' field in the registry; the macrolanguages themselves 1340 are not specially marked. Note that some encompassed languages have 1341 ISO 639-1 or ISO 639-2 codes. 1343 The Macrolanguage field can only occur in records of type 'language' 1344 or 'extlang'. Only values assigned by ISO 639-3 will be considered 1345 for inclusion. Macrolanguage fields MAY be added or removed via the 1346 normal registration process whenever ISO 639-3 defines new values or 1347 withdraws old values. Macrolanguages are informational, and MAY be 1348 removed or changed if ISO 639-3 changes the values. For more 1349 information on the use of this field and choosing between 1350 macrolanguage and encompassed language subtags, see Section 4.1.1. 1352 For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' 1353 (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' 1354 (Norwegian). For more information see Section 4.1. 1356 3.1.10. Scope Field 1358 The field 'Scope' contains classification information about a primary 1359 or extended language subtag derived from ISO 639. This information 1360 can sometimes be helpful in selecting language tags, since it 1361 indicates the purpose of the code assignment within ISO 639. The 1362 available values are: 1364 o 'individual' - A langauge that is not a macrolanguage, specical 1365 value, or collection. That is, it is what one would normally 1366 consider to be a language. 1368 o 'macrolanguage' - Indicates a macrolanguage as defined by ISO 1369 639-3. For more information on macrolanguages, see: 1370 Section 3.1.9. 1372 o 'collection' - Indicates a subtag that represents a collection of 1373 languages. Unlike a macrolanguage, a collection can contain 1374 languages that are only loosely related. 1376 o 'special' - Indicates a special language code. These are used for 1377 special language identifcation purposes. 1379 The Scope field MUST appear in all records of type 'language' or 1380 'extlang'. Records of type 'extlang' MUST NOT include a value other 1381 than 'individual'. Note that most of the prefixes for extended 1382 language subtags will have a Scope of 'macrolanguage' (although some 1383 will not). 1385 The Scope fied MAY be modified via the registration process, should 1386 ISO 639 change the assignment's classification. Such a change is 1387 expected to be rare. 1389 For example, the primary language subtag 'zh' (Chinese) has a Scope 1390 of 'macrolanguage', while its enclosed language 'nan' (Min Nan 1391 Chinese) has a Scope of 'individual'. The special value 'und' 1392 (Undetermined) has a Scope of 'special'. The ISO 639-5 collection 1393 'gem' (Germanic languages) has a Scope of 'collection'. 1395 3.1.11. Comments Field 1397 The field 'Comments' conveys additional information about the record 1398 and MAY appear more than once per record. The field-body MAY include 1399 the full range of Unicode characters and is not restricted to any 1400 particular script. This field MAY be inserted or changed via the 1401 registration process and no guarantee of stability is provided. 1403 The content of this field is not restricted, except by the need to 1404 register the information, the suitability of the request, and by 1405 reasonable practical size limitations. The primary reason for the 1406 Comments field is subtag identification: to help distinguish the 1407 subtag from others with which it might be confused. In particular, 1408 large amounts of information about the use, history, or general 1409 background of a subtag are frowned upon as these generally belong and 1410 are encouraged in registration request forms themselves, but do not 1411 belong in the registry record proper. 1413 3.2. Language Subtag Reviewer 1415 The Language Subtag Reviewer moderates the ietf-languages mailing 1416 list, responds to requests for registration, and performs the other 1417 registry maintenance duties described in Section 3.3. Only the 1418 Language Subtag Reviewer is permitted to request IANA to change, 1419 update, or add records to the Language Subtag Registry. The Language 1420 Subtag Reviewer MAY delegate list moderation and other clerical 1421 duties as needed. 1423 The Language Subtag Reviewer is appointed by the IESG for an 1424 indefinite term, subject to removal or replacement at the IESG's 1425 discretion. The IESG will solicit nominees for the position (upon 1426 adoption of this document or upon a vacancy) and then solicit 1427 feedback on the nominees' qualifications. Qualified candidates 1428 should be familiar with BCP 47 and its requirements; be willing to 1429 fairly, responsively, and judiciously administer the registration 1430 process; and be suitably informed about the issues of language 1431 identification so that the reviewer can assess the claims and draw 1432 upon the contributions of language experts and subtag requesters. 1434 The subsequent performance or decisions of the Language Subtag 1435 Reviewer MAY be appealed to the IESG under the same rules as other 1436 IETF decisions (see [RFC2026]). The IESG can reverse or overturn the 1437 decisions of the Language Subtag Reviewer, provide guidance, or take 1438 other appropriate actions. 1440 3.3. Maintenance of the Registry 1442 Maintenance of the registry requires that as codes are assigned or 1443 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1444 Subtag Reviewer MUST evaluate each change and determine the 1445 appropriate course of action according to the rules in this document. 1446 Such updates follow the registration process described in 1447 Section 3.5. Usually the Language Subtag Reviewer will start the 1448 process for the new or updated record by filling in the registration 1449 form and submitting it. If a change to one of these standards takes 1450 place and the Language Subtag Reviewer does not do this in a timely 1451 manner, then any interested party MAY submit the form. Thereafter 1452 the registration process continues normally. 1454 Note that some registrations affect other subtags--perhaps more than 1455 one--as when a region subtag is being deprecated in favor of a new 1456 value. The Language Subtag Reviewer is responsible for ensuring that 1457 any such changes are properly registered, with each change requiring 1458 its own registration form. 1460 The Language Subtag Reviewer MUST ensure that new subtags meet the 1461 requirements elsewhere in this document (and most especially in 1462 Section 3.4) or submit an appropriate registration form for an 1463 alternate subtag as described in that section. Each individual 1464 subtag affected by a change MUST be sent to the ietf-languages list 1465 with its own registration form and in a separate message. 1467 3.4. Stability of IANA Registry Entries 1469 The stability of entries and their meaning in the registry is 1470 critical to the long-term stability of language tags. The rules in 1471 this section guarantee that a specific language tag's meaning is 1472 stable over time and will not change. 1474 These rules specifically deal with how changes to codes (including 1475 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1476 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1477 Subtag Registry. Assignments to the IANA Language Subtag Registry 1478 MUST follow the following stability rules: 1480 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST 1481 NOT be changed and are guaranteed to be stable over time. 1483 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be 1484 added, altered, or removed via the registration process. These 1485 changes SHOULD be limited to changes necessary to mirror changes 1486 in one of the underlying standards (ISO 639, ISO 15924, ISO 1487 3166-1, or UN M.49) and typically alteration or removal of a 1488 Preferred-Value is limited specifically to region codes. 1490 3. Values in the 'Description' field MUST NOT be changed in a way 1491 that would invalidate previously-existing tags. They MAY be 1492 broadened somewhat in scope, changed to add information, or 1493 adapted to the most common modern usage. For example, countries 1494 occasionally change their names; a historical example of this 1495 would be "Upper Volta" changing to "Burkina Faso". 1497 4. The field 'Prefix' MUST NOT be removed from any record in which 1498 it appears. This field SHOULD be included in the initial 1499 registration of any records of type 'variant' and MUST be 1500 included in any records of type 'extlang'. 1502 5. Values in the field 'Prefix' MAY be added to existing records of 1503 type 'variant' via the registration process. If a prefix is 1504 added to a variant record, 'Comment' fields SHOULD be used to 1505 explain different usages with the various prefixes. 1507 6. Values in the field 'Prefix' in records of type 'variant' MAY 1508 also be modified, so long as the modifications broaden the set 1509 of prefixes. That is, a prefix MAY be replaced by one of its 1510 own prefixes. For example, the prefix "en-US" could be replaced 1511 by "en", but not by the prefixes "en-Latn", "fr", or "en-US- 1512 boont". If one of those prefixes were needed, a new Prefix 1513 SHOULD be registered. 1515 7. Values in the field 'Prefix' in records of type 'extlang' MUST 1516 NOT be added, modified, or removed. 1518 8. The field 'Comments' MAY be added, changed, modified, or removed 1519 via the registration process or any of the processes or 1520 considerations described in this section. 1522 9. The field 'Suppress-Script' MAY be added or removed via the 1523 registration process. 1525 10. The field 'Macrolanguage' MAY be added or removed via the 1526 registration process, but only in response to changes made by 1527 ISO 639. The Macrolanguage field appears whenever a language 1528 has a corresponding Macrolanguage in ISO 639. That is, the 1529 Macrolanguage fields in the registry exactly match those of ISO 1530 639. No other macrolanguage mappings will be considered for 1531 registration. 1533 11. The field 'Scope' MUST NOT be added or removed from a primary or 1534 extended language subtag after initial registration, howeiver it 1535 MAY be modified in order to match any changes made by ISO 639. 1537 12. Primary and extended language subtags (other than independently 1538 registered values created using the registration process) are 1539 created according to the assignments of the various parts of ISO 1540 639, as follows: 1542 1. Codes assigned by ISO 639-1 that do not conflict with 1543 existing two-letter primary language subtags and which have 1544 no corresponding three-letter primary defined in the 1545 registry are entered into the IANA registry as new records 1546 of type 'language'. Note that languages given an ISO 639-1 1547 code cannot be extended language subtags, even if enclosed 1548 by a macrolanguage. 1550 2. Codes assigned by ISO 639-3 or ISO 639-5 that do not 1551 conflict with existing three-letter primary language subtags 1552 and which do not have ISO 639-1 codes assigned (or expected 1553 to be assigned) are entered into the IANA registry as new 1554 records of type 'language'. Codes that have a defined 1555 "macrolanguage" mapping at the time of their registration 1556 MUST contain a "Macrolanguage" field. 1558 3. Codes assigned by ISO 639-3 MAY also be considered for an 1559 extended language subtag registration. Note that they MUST 1560 be assigned a primary language subtag record of type 1561 'language' even when an 'extlang' record is proposed. When 1562 considering extended language subtag assignment, these 1563 criteria apply: 1565 1. Languages whose macrolanguage mapping at the time of 1566 their creation that maps to a language that has extended 1567 language records assigned SHOULD have an 'extlang' 1568 record. For example, any language with a macrolanguage 1569 of 'zh' or 'ar'. 1571 2. 'Extlang' records SHOULD NOT be created for languages if 1572 other languages enclosed by the macrolanguage do not 1573 also include 'extlang' records. For example, if a new 1574 Serbo-Croatian ('sh') language were registered, it would 1575 not get an extlang record because other languages 1576 enclosed such as Serbian ('sr') do not include one in 1577 the registry. 1579 3. Sign languages SHOULD have an 'extlang' record with a 1580 'Prefix' of 'sgn'. 1582 4. 'Extlang' records MUST NOT be created for items already 1583 in the registry. Extended language subtags will only be 1584 considered at the time of initial registration. 1586 5. Extended language subtag records MUST include the fields 1587 'Prefix', 'Deprecated', and 'Preferred-Value' with 1588 field-values assigned as described in Section 2.2.2. 1590 4. Any other codes assigned by ISO 639-2 that do not conflict 1591 with existing three-letter primary or extended language 1592 subtags and which do not have ISO 639-1 two-letter codes 1593 assigned are entered into the IANA registry as new records 1594 of type 'language'. This type of registration is not 1595 supposed to occur in the future. 1597 13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict 1598 with existing subtags of the associated type and whose meaning 1599 is not the same as an existing subtag of the same type are 1600 entered into the IANA registry as new records. 1602 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are 1603 withdrawn by their respective maintenance or registration 1604 authority remain valid in language tags. A 'Deprecated' field 1605 containing the date of withdrawal MUST be added to the record. 1607 If a new record of the same type is added that represents a 1608 replacement value, then a 'Preferred-Value' field MAY also be 1609 added. The registration process MAY be used to add comments 1610 about the withdrawal of the code by the respective standard. 1612 Example The region code 'TL' was assigned to the country 1613 'Timor-Leste', replacing the code 'TP' (which was assigned to 1614 'East Timor' when it was under administration by Portugal). 1615 The subtag 'TP' remains valid in language tags, but its 1616 record contains the a 'Preferred-Value' of 'TL' and its field 1617 'Deprecated' contains the date the new code was assigned 1618 ('2004-07-06'). 1620 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that 1621 conflict with existing subtags of the associated type, including 1622 subtags that are deprecated, MUST NOT be entered into the 1623 registry. The following additional considerations apply to 1624 subtag values that are reassigned: 1626 A. For ISO 639 codes, if the newly assigned code's meaning is 1627 not represented by a subtag in the IANA registry, the 1628 Language Subtag Reviewer, as described in Section 3.5, SHALL 1629 prepare a proposal for entering in the IANA registry as soon 1630 as practical a registered language subtag as an alternate 1631 value for the new code. The form of the registered language 1632 subtag will be at the discretion of the Language Subtag 1633 Reviewer and MUST conform to other restrictions on language 1634 subtags in this document. 1636 B. For all subtags whose meaning is derived from an external 1637 standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN 1638 M.49), if a new meaning is assigned to an existing code and 1639 the new meaning broadens the meaning of that code, then the 1640 meaning for the associated subtag MAY be changed to match. 1641 The meaning of a subtag MUST NOT be narrowed, however, as 1642 this can result in an unknown proportion of the existing 1643 uses of a subtag becoming invalid. Note: ISO 639 1644 registration authority (RA) has adopted a similar stability 1645 policy. 1647 C. For ISO 15924 codes, if the newly assigned code's meaning is 1648 not represented by a subtag in the IANA registry, the 1649 Language Subtag Reviewer, as described in Section 3.5, SHALL 1650 prepare a proposal for entering in the IANA registry as soon 1651 as practical a registered variant subtag as an alternate 1652 value for the new code. The form of the registered variant 1653 subtag will be at the discretion of the Language Subtag 1654 Reviewer and MUST conform to other restrictions on variant 1655 subtags in this document. 1657 D. For ISO 3166-1 codes, if the newly assigned code's meaning 1658 is associated with the same UN M.49 code as another 'region' 1659 subtag, then the existing region subtag remains as the 1660 preferred value for that region and no new entry is created. 1661 A comment MAY be added to the existing region subtag 1662 indicating the relationship to the new ISO 3166-1 code. 1664 E. For ISO 3166-1 codes, if the newly assigned code's meaning 1665 is associated with a UN M.49 code that is not represented by 1666 an existing region subtag, then the Language Subtag 1667 Reviewer, as described in Section 3.5, SHALL prepare a 1668 proposal for entering the appropriate UN M.49 country code 1669 as an entry in the IANA registry. 1671 F. For ISO 3166-1 codes, if there is no associated UN numeric 1672 code, then the Language Subtag Reviewer SHALL petition the 1673 UN to create one. If there is no response from the UN 1674 within ninety days of the request being sent, the Language 1675 Subtag Reviewer SHALL prepare a proposal for entering in the 1676 IANA registry as soon as practical a registered variant 1677 subtag as an alternate value for the new code. The form of 1678 the registered variant subtag will be at the discretion of 1679 the Language Subtag Reviewer and MUST conform to other 1680 restrictions on variant subtags in this document. This 1681 situation is very unlikely to ever occur. 1683 16. UN M.49 has codes for both countries and areas (such as '276' 1684 for Germany) and geographical regions and sub-regions (such as 1685 '150' for Europe). UN M.49 country or area codes for which 1686 there is no corresponding ISO 3166-1 code SHOULD NOT be 1687 registered, except as a surrogate for an ISO 3166-1 code that is 1688 blocked from registration by an existing subtag. If such a code 1689 becomes necessary, then the registration authority for ISO 1690 3166-1 SHOULD first be petitioned to assign a code to the 1691 region. If the petition for a code assignment by ISO 3166-1 is 1692 refused or not acted on in a timely manner, the registration 1693 process described in Section 3.5 MAY then be used to register 1694 the corresponding UN M.49 code. This way, UN M.49 codes remain 1695 available as the value of last resort in cases where ISO 3166-1 1696 reassigns a deprecated value in the registry. 1698 17. Stability provisions apply to grandfathered tags with this 1699 exception: should it become possible to compose one of the 1700 grandfathered tags from registered subtags, then the field 1701 'Type' in that record is changed from 'grandfathered' to 1702 'redundant'. Note that this will not affect language tags that 1703 match the grandfathered tag, since these tags will now match 1704 valid generative subtag sequences. For example, the variant 1705 subtag '1901' is registered, making the formerly-grandfathered 1706 tags such as "de-1901" and "de-AT-1901" redundant as a result. 1707 Of course, these tags, where applied to existing content or in 1708 existing implementations, remain valid (all of their subtags are 1709 in the registry, after all), while new tags or applications 1710 using these subtags become possible. 1712 Note: The redundant and grandfathered entries together are the 1713 complete list of tags registered under [RFC3066]. The redundant tags 1714 are those that can now be formed using the subtags defined in the 1715 registry together with the rules of Section 2.2. The grandfathered 1716 entries include those that can never be legal under those same 1717 provisions plus those tags that contain subtags not yet registered 1718 or, perhaps, inappropriate for registration. 1720 The set of redundant and grandfathered tags is permanent and stable: 1721 new entries in this section MUST NOT be added and existing entries 1722 MUST NOT be removed. Records of type 'grandfathered' MAY have their 1723 type converted to 'redundant'; see item 12 in Section 3.6 for more 1724 information. The decision-making process about which tags were 1725 initially grandfathered and which were made redundant is described in 1726 [RFC4645]. 1728 RFC 3066 tags that were deprecated prior to the adoption of [RFC4646] 1729 are part of the list of grandfathered tags, and their component 1730 subtags were not included as registered variants (although they 1731 remain eligible for registration). For example, the tag "art-lojban" 1732 was deprecated in favor of the language subtag 'jbo'. 1734 3.5. Registration Procedure for Subtags 1736 The procedure given here MUST be used by anyone who wants to use a 1737 subtag not currently in the IANA Language Subtag Registry. 1739 Only subtags of type 'language' and 'variant' will be considered for 1740 independent registration of new subtags. Subtags needed for 1741 stability and subtags necessary to keep the registry synchronized 1742 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1743 defined by this document also use this process, as described in 1744 Section 3.3. Stability provisions are described in Section 3.4. 1746 This procedure MAY also be used to register or alter the information 1747 for the 'Comments', 'Deprecated', 'Description', 'Prefix', 1748 'Preferred-Value', or 'Suppress-Script' fields in a subtag's record 1749 as described in Section 3.4. Changes to all other fields in the IANA 1750 registry are NOT permitted. 1752 Registering a new subtag or requesting modifications to an existing 1753 tag or subtag starts with the requester filling out the registration 1754 form reproduced below. Note that each response is not limited in 1755 size so that the request can adequately describe the registration. 1756 The fields in the "Record Requested" section SHOULD follow the 1757 requirements in Section 3.1. 1759 LANGUAGE SUBTAG REGISTRATION FORM 1760 1. Name of requester: 1761 2. E-mail address of requester: 1762 3. Record Requested: 1764 Type: 1765 Subtag: 1766 Description: 1767 Prefix: 1768 Preferred-Value: 1769 Deprecated: 1770 Suppress-Script: 1771 Macrolanguage: 1772 Comments: 1774 4. Intended meaning of the subtag: 1775 5. Reference to published description 1776 of the language (book or article): 1777 6. Any other relevant information: 1779 Figure 5: The Language Subtag Registration Form 1781 Examples of completed registration forms can be found in Appendix C 1782 or online at http://www.iana.org/assignments/lang-subtags-templates/. 1784 The subtag registration form MUST be sent to 1785 for a two-week review period before it can 1786 be submitted to IANA. If modifications are made to the request 1787 during the course of the registration process (such as corrections to 1788 meet the requirements in Section 3.1) the modified form MUST also be 1789 sent to at least one week prior to 1790 submission to IANA. 1792 The ietf-languages list is an open list and can be joined by sending 1793 a request to . The list can be 1794 hosted by IANA or by any third party at the request of IESG. 1796 Before forwarding a new registration to IANA, the Language Subtag 1797 Reviewer MUST ensure that all requirements in this document are met 1798 and that values in the 'Subtag' field match case according to the 1799 description in Section 3.1. The Reviewer MUST also ensure that an 1800 appropriate File-Date record is included in the request, to assist 1801 IANA when updating the registry (see Section 5.1). 1803 Some fields in both the registration form as well as the registry 1804 record itself permit the use of non-ASCII characters. Registration 1805 requests SHOULD use the UTF-8 encoding for consistency and clarity. 1806 However, since some mail clients do not support this encoding, other 1807 encodings MAY be used for the registration request. The Language 1808 Subtag Reviewer is responsible for ensuring that the proper Unicode 1809 characters appear in both the archived request form and the registry 1810 record. In the case of a transcription or encoding error by IANA, 1811 the Language Subtag Reviewer will request that the registry be 1812 repaired, providing any necessary information to assist IANA. 1814 Extended language subtags (type 'extlang'), by definition, are always 1815 enclosed by another language. All records of type 'extlang' MUST, 1816 therefore, contain a 'Prefix' field at the time of registration. 1817 This prefix value can never be altered or removed. 1819 Variant subtags are usually registered for use with a particular 1820 range of language tags. For example, the subtag 'rozaj' is intended 1821 for use with language tags that start with the primary language 1822 subtag "sl", since Resian is a dialect of Slovenian. Thus, the 1823 subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj" 1824 or "sl-IT-rozaj". This information is stored in the 'Prefix' field 1825 in the registry. Variant registration requests SHOULD include at 1826 least one 'Prefix' field in the registration form. 1828 The 'Prefix' field for a given registered variant subtag exists in 1829 the IANA registry as a guide to usage. Additional prefixes MAY be 1830 added by filing an additional registration form. In that form, the 1831 "Any other relevant information:" field MUST indicate that it is the 1832 addition of a prefix. 1834 Requests to add a 'Prefix' field to a variant subtag that imply a 1835 different semantic meaning SHOULD be rejected. For example, a 1836 request to add the prefix "de" to the subtag '1994' so that the tag 1837 "de-1994" represented some German dialect or orthographic form would 1838 be rejected. The '1994' subtag represents a particular Slovenian 1839 orthography and the additional registration would change or blur the 1840 semantic meaning assigned to the subtag. A separate subtag SHOULD be 1841 proposed instead. 1843 The 'Description' field MUST contain a description of the tag being 1844 registered written or transcribed into the Latin script; it MAY also 1845 include a description in a non-Latin script. The 'Description' field 1846 is used for identification purposes and doesn't necessarily represent 1847 the actual native name of the language or variation or to be in any 1848 particular language. 1850 While the 'Description' field itself is not guaranteed to be stable 1851 and errata corrections MAY be undertaken from time to time, attempts 1852 to provide translations or transcriptions of entries in the registry 1853 itself will probably be frowned upon by the community or rejected 1854 outright, as changes of this nature have an impact on the provisions 1855 in Section 3.4. 1857 When the two-week period has passed, the Language Subtag Reviewer 1858 MUST take one of the following actions: 1860 o Explicitly accept the request and forward the form containing the 1861 record to be inserted or modified to iana@iana.org according to 1862 the procedure described in Section 3.3. 1864 o Explicitly reject the request because of significant objections 1865 raised on the list or due to problems with constraints in this 1866 document (which MUST be explicitly cited). 1868 o Extend the review period by granting an additional two-week 1869 increment to permit further discussion. After each two-week 1870 increment, the Language Subtag Reviewer MUST indicate on the list 1871 whether the registration has been accepted, rejected, or extended. 1873 Note that the Language Subtag Reviewer MAY raise objections on the 1874 list if he or she so desires. The important thing is that the 1875 objection MUST be made publicly. 1877 Sometimes the request needs to be modified as a result of discussion 1878 during the review period or due to requirements in this document. 1879 The applicant, Language Subtag Reviewer, or others are free to submit 1880 a modified version of the completed registration form, which will be 1881 considered in lieu of the original request with the explicit approval 1882 of the applicant. Such changes do not restart the two-week 1883 discussion period, although an application containing the final 1884 record submitted to IANA MUST appear on the list at least one week 1885 prior to the Language Subtag Reviewer forwarding the record to IANA. 1886 The applicant is also free to modify a rejected application with 1887 additional information and submit it again; this starts a new two- 1888 week comment period. 1890 Registrations initiated due to the provisions of Section 3.3 or 1891 Section 3.4 SHALL NOT be rejected altogether (since they have to 1892 ultimately appear in the registry) and SHOULD be completed as quickly 1893 as possible. The review process allows list members to comment on 1894 the specific information in the form and the record it contains and 1895 thus help ensure that it is correct and consistent. The Language 1896 Subtag Reviewer MAY reject a specific version of the form, but MUST 1897 include in the rejection a suitable replacement, extending the review 1898 period as described above, until the form is in a format worthy of 1899 reviewer's approval. 1901 Decisions made by the Language Subtag Reviewer MAY be appealed to the 1902 IESG [RFC2028] under the same rules as other IETF decisions 1903 [RFC2026]. This includes a decision to extend the review period or 1904 the failure to announce a decision in a clear and timely manner. 1906 The approved records appear in the Language Subtag Registry. The 1907 approved registration forms are available online under 1908 http://www.iana.org/assignments/lang-subtags-templates/. 1910 Updates or changes to existing records follow the same procedure as 1911 new registrations. The Language Subtag Reviewer decides whether 1912 there is consensus to update the registration following the two week 1913 review period; normally, objections by the original registrant will 1914 carry extra weight in forming such a consensus. 1916 Registrations are permanent and stable. Once registered, subtags 1917 will not be removed from the registry and will remain a valid way in 1918 which to specify a specific language or variant. 1920 Note: The purpose of the "Reference to published description" section 1921 in the registration form is to aid in verifying whether a language is 1922 registered or what language or language variation a particular subtag 1923 refers to. In most cases, reference to an authoritative grammar or 1924 dictionary of that language will be useful; in cases where no such 1925 work exists, other well-known works describing that language or in 1926 that language MAY be appropriate. The Language Subtag Reviewer 1927 decides what constitutes "good enough" reference material. This 1928 requirement is not intended to exclude particular languages or 1929 dialects due to the size of the speaker population or lack of a 1930 standardized orthography. Minority languages will be considered 1931 equally on their own merits. 1933 3.6. Possibilities for Registration 1935 Possibilities for registration of subtags or information about 1936 subtags include: 1938 o Primary language subtags for languages not listed in ISO 639 that 1939 are not variants of any listed or registered language MAY be 1940 registered. At the time this document was created, there were no 1941 examples of this form of subtag. Before attempting to register a 1942 language subtag, there MUST be an attempt to register the language 1943 with ISO 639. Subtags MUST NOT be registered for languages 1944 defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, 1945 or that are under consideration by the ISO 639 registration 1946 authorities, or that have never been attempted for registration 1947 with those authorities. If ISO 639 has previously rejected a 1948 language for registration, it is reasonable to assume that there 1949 must be additional, very compelling evidence of need before it 1950 will be registered as a primary language subtag in the IANA 1951 registry (to the extent that it is very unlikely that any subtags 1952 will be registered of this type). 1954 o Dialect or other divisions or variations within a language, its 1955 orthography, writing system, regional or historical usage, 1956 transliteration or other transformation, or distinguishing 1957 variation MAY be registered as variant subtags. An example is the 1958 'rozaj' subtag (the Resian dialect of Slovenian). 1960 o The addition or maintenance of fields (generally of an 1961 informational nature) in Tag or Subtag records as described in 1962 Section 3.1 and subject to the stability provisions in 1963 Section 3.4. This includes descriptions, comments, deprecation 1964 and preferred values for obsolete or withdrawn codes, or the 1965 addition of script or macrolanguage information to primary 1966 language subtags. 1968 o The addition of records and related field value changes necessary 1969 to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and 1970 UN M.49 as described in Section 3.4. 1972 Subtags proposed for registration that would cause all or part of a 1973 grandfathered tag to become redundant but whose meaning conflicts 1974 with or alters the meaning of the grandfathered tag MUST be rejected. 1976 This document leaves the decision on what subtags or changes to 1977 subtags are appropriate (or not) to the registration process 1978 described in Section 3.5. 1980 Note: four-character primary language subtags are reserved to allow 1981 for the possibility of alpha4 codes in some future addition to the 1982 ISO 639 family of standards. 1984 ISO 639 defines a registration authority for additions to and changes 1985 in the list of languages in ISO 639. This agency is: 1987 International Information Centre for Terminology (Infoterm) 1988 Aichholzgasse 6/12, AT-1120 1989 Wien, Austria 1990 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1991 ISO 639-2 defines a registration authority for additions to and 1992 changes in the list of languages in ISO 639-2. This agency is: 1994 Library of Congress 1995 Network Development and MARC Standards Office 1996 Washington, D.C. 20540 USA 1997 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1998 URL: http://www.loc.gov/standards/iso639-2 2000 ISO 639-3 defines a registration authority for additions to and 2001 changes in the list of languages in ISO 639-3. This agency is: 2003 SIL International 2004 ISO 639-3 Registrar 2005 7500 W. Camp Wisdom Rd. 2006 Dallas, TX 75236 USA 2007 Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 2008 Email: iso639-3@sil.org 2009 URL: http://www.sil.org/iso639-3 2011 ISO 639-5 defines a registration authority for additions to and 2012 changes in the list of languages in ISO 639-5. This agency is the 2013 same as for ISO 639-2 and is: 2015 Library of Congress 2016 Network Development and MARC Standards Office 2017 Washington, D.C. 20540 USA 2018 Phone: +1 202 707 6237 Fax: +1 202 707 0115 2019 URL: http://www.loc.gov/standards/iso639-5 2021 The maintenance agency for ISO 3166-1 (country codes) is: 2023 ISO 3166 Maintenance Agency 2024 c/o International Organization for Standardization 2025 Case postale 56 2026 CH-1211 Geneva 20 Switzerland 2027 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 2028 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 2030 The registration authority for ISO 15924 (script codes) is: 2032 Unicode Consortium Box 391476 2033 Mountain View, CA 94039-1476, USA 2034 URL: http://www.unicode.org/iso15924 2036 The Statistics Division of the United Nations Secretariat maintains 2037 the Standard Country or Area Codes for Statistical Use and can be 2038 reached at: 2040 Statistical Services Branch 2041 Statistics Division 2042 United Nations, Room DC2-1620 2043 New York, NY 10017, USA 2045 Fax: +1-212-963-0623 2046 E-mail: statistics@un.org 2047 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 2049 3.7. Extensions and the Extensions Registry 2051 Extension subtags are those introduced by single-character subtags 2052 ("singletons") other than 'x'. They are reserved for the generation 2053 of identifiers that contain a language component and are compatible 2054 with applications that understand language tags. 2056 The structure and form of extensions are defined by this document so 2057 that implementations can be created that are forward compatible with 2058 applications that might be created using singletons in the future. 2059 In addition, defining a mechanism for maintaining singletons will 2060 lend stability to this document by reducing the likely need for 2061 future revisions or updates. 2063 Single-character subtags are assigned by IANA using the "IETF 2064 Consensus" policy defined by [RFC2434]. This policy requires the 2065 development of an RFC, which SHALL define the name, purpose, 2066 processes, and procedures for maintaining the subtags. The 2067 maintaining or registering authority, including name, contact email, 2068 discussion list email, and URL location of the registry, MUST be 2069 indicated clearly in the RFC. The RFC MUST specify or include each 2070 of the following: 2072 o The specification MUST reference the specific version or revision 2073 of this document that governs its creation and MUST reference this 2074 section of this document. 2076 o The specification and all subtags defined by the specification 2077 MUST follow the ABNF and other rules for the formation of tags and 2078 subtags as defined in this document. In particular, it MUST 2079 specify that case is not significant and that subtags MUST NOT 2080 exceed eight characters in length. 2082 o The specification MUST specify a canonical representation. 2084 o The specification of valid subtags MUST be available over the 2085 Internet and at no cost. 2087 o The specification MUST be in the public domain or available via a 2088 royalty-free license acceptable to the IETF and specified in the 2089 RFC. 2091 o The specification MUST be versioned, and each version of the 2092 specification MUST be numbered, dated, and stable. 2094 o The specification MUST be stable. That is, extension subtags, 2095 once defined by a specification, MUST NOT be retracted or change 2096 in meaning in any substantial way. 2098 o The specification MUST include in a separate section the 2099 registration form reproduced in this section (below) to be used in 2100 registering the extension upon publication as an RFC. 2102 o IANA MUST be informed of changes to the contact information and 2103 URL for the specification. 2105 IANA will maintain a registry of allocated single-character 2106 (singleton) subtags. This registry MUST use the record-jar format 2107 described by the ABNF in Section 3.1. Upon publication of an 2108 extension as an RFC, the maintaining authority defined in the RFC 2109 MUST forward this registration form to iesg@ietf.org, who MUST 2110 forward the request to iana@iana.org. The maintaining authority of 2111 the extension MUST maintain the accuracy of the record by sending an 2112 updated full copy of the record to iana@iana.org with the subject 2113 line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only 2114 the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY 2115 be modified in these updates. 2117 Failure to maintain this record, maintain the corresponding registry, 2118 or meet other conditions imposed by this section of this document MAY 2119 be appealed to the IESG [RFC2028] under the same rules as other IETF 2120 decisions (see [RFC2026]) and MAY result in the authority to maintain 2121 the extension being withdrawn or reassigned by the IESG. 2123 %% 2124 Identifier: 2125 Description: 2126 Comments: 2127 Added: 2128 RFC: 2129 Authority: 2130 Contact_Email: 2131 Mailing_List: 2132 URL: 2133 %% 2135 Figure 6: Format of Records in the Language Tag Extensions Registry 2137 'Identifier' contains the single-character subtag (singleton) 2138 assigned to the extension. The Internet-Draft submitted to define 2139 the extension SHOULD specify which letter or digit to use, although 2140 the IESG MAY change the assignment when approving the RFC. 2142 'Description' contains the name and description of the extension. 2144 'Comments' is an OPTIONAL field and MAY contain a broader description 2145 of the extension. 2147 'Added' contains the date the extension's RFC was published in the 2148 "full-date" format specified in [RFC3339]. For example: 2004-06-28 2149 represents June 28, 2004, in the Gregorian calendar. 2151 'RFC' contains the RFC number assigned to the extension. 2153 'Authority' contains the name of the maintaining authority for the 2154 extension. 2156 'Contact_Email' contains the email address used to contact the 2157 maintaining authority. 2159 'Mailing_List' contains the URL or subscription email address of the 2160 mailing list used by the maintaining authority. 2162 'URL' contains the URL of the registry for this extension. 2164 The determination of whether an Internet-Draft meets the above 2165 conditions and the decision to grant or withhold such authority rests 2166 solely with the IESG and is subject to the normal review and appeals 2167 process associated with the RFC process. 2169 Extension authors are strongly cautioned that many (including most 2170 well-formed) processors will be unaware of any special relationships 2171 or meaning inherent in the order of extension subtags. Extension 2172 authors SHOULD avoid subtag relationships or canonicalization 2173 mechanisms that interfere with matching or with length restrictions 2174 that sometimes exist in common protocols where the extension is used. 2175 In particular, applications MAY truncate the subtags in doing 2176 matching or in fitting into limited lengths, so it is RECOMMENDED 2177 that the most significant information be in the most significant 2178 (left-most) subtags and that the specification gracefully handle 2179 truncated subtags. 2181 When a language tag is to be used in a specific, known, protocol, it 2182 is RECOMMENDED that the language tag not contain extensions not 2183 supported by that protocol. In addition, note that some protocols 2184 MAY impose upper limits on the length of the strings used to store or 2185 transport the language tag. 2187 3.8. Update of the Language Subtag Registry 2189 Upon adoption of this document the IANA Language Subtag Registry will 2190 need an update so that it contains the complete set of subtags valid 2191 in a language tag. This collection of subtags, along with a 2192 description of the process used to create it, is described by 2193 [registry-update]. IANA will publish the updated version of the 2194 registry described by this document using the instructions and 2195 content of [registry-update]. Once published by IANA, the 2196 maintenance procedures, rules, and registration processes described 2197 in this document will be available for new registrations or updates. 2199 Registrations that are in process under the rules defined in 2200 [RFC4646] when this document is adopted MUST be completed under the 2201 rules contained in this document. 2203 4. Formation and Processing of Language Tags 2205 This section addresses how to use the information in the registry 2206 with the tag syntax to choose, form, and process language tags. 2208 4.1. Choice of Language Tag 2210 The guiding principle in forming language tags is to "tag content 2211 wisely." Sometimes there is a choice between several possible tags 2212 for the same content. The choice of which tag to use depends on the 2213 content and application in question and some amount of judgment might 2214 be necessary when selecting a tag. 2216 Interoperability is best served when the same language tag is used 2217 consistently to represent the same language. If an application has 2218 requirements that make the rules here inapplicable, then that 2219 application risks damaging interoperability. It is strongly 2220 RECOMMENDED that users not define their own rules for language tag 2221 choice. 2223 Standards, protocols, and applications that reference this document 2224 normatively but apply different rules to the ones given in this 2225 section MUST specify how language tag selection varies from the 2226 guidelines given here. 2228 To ensure consistent backward compatibility, this document contains 2229 several provisions to account for potential instability in the 2230 standards used to define the subtags that make up language tags. 2231 These provisions mean that no valid language tag can become invalid, 2232 nor will a language tag have a narrower scope in the future (it may 2233 have a broader scope). The most appropriate language tag for a given 2234 application or content item might evolve over time, but once tagged 2235 the content cannot become invalid. 2237 A subtag SHOULD only be used when it adds useful distinguishing 2238 information to the tag. Extraneous subtags interfere with the 2239 meaning, understanding, and processing of language tags. In 2240 particular, users and implementations SHOULD follow the 'Prefix' and 2241 'Suppress-Script' fields in the registry (defined in Section 3.1): 2242 these fields provide guidance on when specific additional subtags 2243 SHOULD be used or avoided in a language tag. 2245 Some applications can benefit from the use of script subtags in 2246 language tags, as long as the use is consistent for a given context. 2247 Script subtags are never appropriate for unwritten content (such as 2248 audio recordings). 2250 Script subtags were first formally defined in BCP 47 by [RFC4646]. 2252 Their use can affect matching and subtag identification for 2253 implementations of previous versions of BCP 47 (i.e. [RFC1766] or 2254 [RFC3066]), as these subtags appear between the primary language and 2255 region subtags. For example, if an implementation selects content 2256 using Basic Filtering [RFC4647] (originally described in Section 2.5 2257 of [RFC3066]) and the user requested the language range "en-US", 2258 content labeled "en-Latn-US" will not match the request and thus not 2259 be selected. Therefore, it is important to know when script subtags 2260 will customarily be used and when they ought not be used. In the 2261 registry, the Suppress-Script field helps ensure greater 2262 compatibility between the language tags by defining when users SHOULD 2263 NOT include a script subtag with a particular primary language 2264 subtag. 2266 The choice of subtags used to form a language tag SHOULD follow these 2267 guidelines: 2269 1. Use as precise a tag as possible, but no more specific than is 2270 justified. Avoid using subtags that are not important for 2271 distinguishing content in an application. 2273 * For example, 'de' might suffice for tagging an email written 2274 in German, while "de-CH-1996" is probably unnecessarily 2275 precise for such a task. 2277 * Note that some subtag sequences might not represent the 2278 language a casual user might expect, especially if when 2279 relying on the subtag's description in the registry. For 2280 example, the Swiss German (Schweizerdeutsch) language is 2281 represented by "gsw-CH" and not by "de-CH". This latter tag 2282 represents German ('de') as used in Switzerland ('CH'), also 2283 known as Swiss High German (Schweizer Hochdeutsch). Both are 2284 real languages and distinguishing between them could be 2285 important to an application. 2287 2. The script subtag SHOULD NOT be used to form language tags unless 2288 the script adds some distinguishing information to the tag. The 2289 field 'Suppress-Script' in the primary language record in the 2290 registry indicates script subtags that do not add distinguishing 2291 information for most applications. For example: 2293 * The subtag 'Latn' should not be used with the primary language 2294 'en' because nearly all English documents are written in the 2295 Latin script and it adds no distinguishing information. 2296 However, if a document were written in English mixing Latin 2297 script with another script such as Braille ('Brai'), then it 2298 might be appropriate to choose to indicate both scripts to aid 2299 in content selection, such as the application of a style 2300 sheet. 2302 * When labeling content that is unwritten (such as a recording 2303 of human speech), the script subtag should not be used, even 2304 if the language is customarily written in several scripts. 2305 Thus the subtitles to a movie might use the tag "uz-Arab" 2306 (Uzbek, Arabic script), but the audio track for the same 2307 language would be tagged simply "uz". (The tag "uz-Zxxx" 2308 could also be used where content is not written, as the subtag 2309 'Zxxx' represents the "Code for unwritten documents".) 2311 3. If a tag or subtag has a 'Preferred-Value' field in its registry 2312 entry, then the value of that field SHOULD be used to form the 2313 language tag in preference to the tag or subtag in which the 2314 preferred value appears. 2316 * For example, use 'he' for Hebrew in preference to 'iw'. 2318 4. [ISO639-2] has defined several codes included in the subtag 2319 registry that require additional care when choosing language 2320 tags. In most of these cases, where omitting the language tag is 2321 permitted, such omission is preferable to using these codes. 2322 Language tags SHOULD NOT incorporate these subtags as a prefix, 2323 unless the additional information conveys some value to the 2324 application. 2326 1. Use specific language subtags or subtag sequences in 2327 preference to subtags for language collections. A "language 2328 collection" is a subtag derived from one of the [ISO639-5] 2329 codes that represents multiple related languages. These 2330 codes are included as primary language subtags in the 2331 registry. For example, the code 'cmc' represents "Chamic 2332 languages". The registry contains values for each of the 2333 approximately ten individual languages represented by this 2334 collective code. Some other examples include the subtags 2335 Germanic languages ('gem') or Algonquian languages ('alg'). 2336 Since these codes are interpreted inclusively, content tagged 2337 with "en" (English), "de" (German), or "gsw" (Swiss German, 2338 Alemannic) could also (but SHOULD NOT) be tagged with "gem" 2339 (Germanic languages). Subtags derived from collection codes 2340 SHOULD NOT be used be used unless more specific language 2341 information is not available. Note that matching 2342 implementations generally do not understand the relationship 2343 between the collection and its encompassed languages, and so 2344 users ought not assume a subtag based on a language 2345 collection is a useful means for selecting content in its 2346 encompassed languages. 2348 2. The 'mul' (Multiple) primary language subtag identifies 2349 content in multiple languages. This subtag SHOULD NOT be 2350 used when a list of languages (such as Content-Language) or 2351 individual tags for each content element can be used instead. 2353 3. The 'und' (Undetermined) primary language subtag identifies 2354 linguistic content whose language is not determined. This 2355 subtag SHOULD NOT be used unless a language tag is required 2356 and language information is not available or cannot be 2357 determined. Omitting the language tag (where permitted) is 2358 preferred. The 'und' subtag MAY be useful for protocols that 2359 require a language tag to be provided or where a primary 2360 language subtag is required (such as in "und-Latn"). The 2361 'und' subtag MAY also be useful when matching language tags 2362 in certain situations. 2364 4. The 'zxx' (Non-Linguistic, Not Applicable) primary language 2365 subtag identifies content for which a language classification 2366 is inappropriate or does not apply. Some examples might 2367 include instrumental or electronic music; sound recordings 2368 consisting of nonverbal sounds; audiovisual materials with no 2369 narration, dialog, printed titles, or subtitles; machine- 2370 readable data files consisting of machine languages or 2371 character codes; or programming source code. 2373 5. The 'mis' (Uncoded) primary language subtag identifies 2374 content whose language is known but which does not currently 2375 have a corresponding subtag. This subtag SHOULD NOT be used. 2376 Because the addition of other codes in the future can render 2377 its application invalid, it is inherently unstable and hence 2378 incompatible with the stability goals of BCP 47. It is 2379 always preferable to use other subtags: either 'und' or (with 2380 prior agreement) private use subtags. 2382 6. The grandfathered tag "i-default" (Default Language) was 2383 originally registered according to [RFC1766] to meet the 2384 needs of [RFC2277]. It is used to indicate not a specific 2385 language, but rather, it identifies the condition or content 2386 used where the language preferences of the user cannot be 2387 established. It SHOULD NOT be used except as a means of 2388 labeling the default content for applications or protocols 2389 that require default language content to be labeled with that 2390 specific tag. It MAY also be used by an application or 2391 protocol to identify when the default language content is 2392 being returned. 2394 4.1.1. Tagging Encompassed Languages 2396 Some primary language records in the registry have a "Macrolanguage" 2397 field (Section 3.1.9) that contains a mapping from each "encompassed 2398 language" to its macrolanguage. The Macrolanguage mapping doesn't 2399 define what the relationship between the encompassed language and its 2400 macrolanguage is, nor does it define how languages encompassed by the 2401 same macrolanguage are related to each other.　Two different 2402 languages encompassed by the same macrolanguage may differ from one 2403 another more than say, French and Spanish do. 2405 The macrolanguages Chinese ('zh') and Arabic ('ar') are handled 2406 differently. See Section 4.1.2. 2408 The more specific encompassed language subtag SHOULD be used to form 2409 the language tag, although either the macrolanguage's primary 2410 language subtag or the encompassed language's subtag MAY be used. 2411 This means, for example, tagging Plains Cree with 'crk' rather than 2412 'cre' (Cree); and so forth. 2414 Each Macrolanguage's subtag, by definition, includes all of its 2415 encompassed languages. Since the relationship between encompassed 2416 languages varies, users cannot assume that the macrolanguage subtag 2417 means any particular encompassed language nor that any given pair of 2418 encompassed languages are mutually intelligible or otherwise 2419 interchangeable. 2421 Applications MAY use macrolanguage information to improve matching or 2422 language negotiation. For example, the information that 'sr' 2423 (Serbian) and 'hr' (Croatian) share a macrolanguage expresses a 2424 closer relation between those languages than between, say, 'sr' 2425 (Serbian) and 'ma' (Macedonian). However, this relationship is not 2426 guaranteed nor is it exclusive. For example, Romanian ('ro') and 2427 Moldavian ('mo') do not share a macrolanguage, but are far more 2428 closely related to each other than Cantonese ('yue') and Wu ('wuu') , 2429 which do share a macrolanguage. 2431 4.1.2. Using Extended Language Subtags 2433 To accommodate language tag forms used prior to the adoption of this 2434 document, language tags provide a special compatibility mechanism: 2435 the extended language subtag. Selected languages have been provided 2436 with both primary and extended language subtags. These include 2437 macrolanguages, such as Malay ('ms') or Uzbek ('uz'), that have a 2438 specific dominant variety that is generally synonymous with the 2439 macrolanguage. Other languages, such as the Chinese ('zh') and 2440 Arabic ('ar') macrolanguages and the various sign languages ('sgn'), 2441 have traditionally used their primary language subtag, possibly 2442 coupled with various region subtags or as part of a registered 2443 grandfathered tag, to indicate the language. 2445 With the adoption of this document, specific ISO 639-3 subtags became 2446 available to identify the languages contained within these diverse 2447 language families or groupings. This presents a choice of language 2448 tags where previously none existed: 2450 o Each encompassed language's subtag SHOULD be used as the primary 2451 language subtag. For example, a document in Mandarin Chinese 2452 would be tagged "cmn" (the subtag for Mandarin Chinese) in 2453 preference to "zh" (Chinese). 2455 o If compatibility is desired or needed, the encompassed subtag MAY 2456 be used as an extended language subtag. For example, a document 2457 in Mandarin Chinese could be tagged "zh-cmn" instead of either 2458 "cmn" or "zh". 2460 o The macrolanguage or prefixing subtag MAY still be used to form 2461 the tag instead of the more specific encompassed langauge subtag. 2462 That is, tags such as "zh-HK" or "sgn-RU" are still valid. 2464 Chinese ('zh') provides a useful illustration of this. In the past, 2465 various content has used tags beginning with the 'zh' subtag, with 2466 application specific meaning being associated with region codes, 2467 private-use sequences, or grandfathered registered values. This is 2468 because historically only the macrolanguage subtag 'zh' was available 2469 for forming language tags. However, the languages encompassed by the 2470 Chinese subtag 'zh' are, in the main, not mutually intelligible when 2471 spoken and the written forms of these languages also show wide 2472 variation in form and usage. 2474 To provide compatibility, Chinese languages encompassed by the 'zh' 2475 subtag are in the registry as both primary language subtags and as 2476 extended language subtags. For example, the ISO 639-3 code for 2477 Cantonese is 'yue'. Content in Cantonese might historically have 2478 used a tag such as "zh-HK" (since Cantonese is spoken commonly in 2479 Hong Kong), although that tag actually means any type of Chinese as 2480 used in Hong Kong. With the availability of ISO 639-3 codes in the 2481 registry, content in Cantonese can be directly tagged using the 'yue' 2482 subtag. The content can use it as a primary language subtag, as in 2483 the tag "yue-HK" (Cantonese, Hong Kong). Or it can use an extended 2484 language subtag with 'zh', as in the tag "zh-yue-Hant" (Chinese, 2485 Cantonese, Traditional script). 2487 As noted above, applications can choose to use the macrolanguage 2488 subtag to form the tag instead of using the more specific encompassed 2489 language subtag. For example, an application with large quantities 2490 of data already using tags with the 'zh' (Chinese) subtag might 2491 continue to use this more general subtag even for new data, even 2492 though the content could be more precisely tagged with 'cmn' 2493 (Mandarin), 'yue' (Cantonese), 'wuu' (Wu), and so on. Similarly, an 2494 application already using tags that start with the 'ar' (Arabic) 2495 subtag might continue to use this more general subtag even for new 2496 data, which could be more precisely be tagged with 'arb' (Standard 2497 Arabic). 2499 In some cases, the encompassed languages had tags registered for them 2500 during the RFC 3066 era. Those grandfathered tags not already 2501 deprecated or rendered redundant were deprecated in the registry upon 2502 adoption of this document. As grandfathered values, they remain 2503 valid for use and some content or applications might use them. As 2504 with other grandfathered tags, since implementations might not be 2505 able to associate the grandfathered tags with the encompassed 2506 language subtag equivalents that are recommended by this document, 2507 implementations are encouraged to canonicalize tags for comparison 2508 purposes. Some examples of this include the tags "zh-hakka" (Hakka) 2509 and "zh-guoyu" (Mandarin or Standard Chinese). 2511 Sign languages share a mode of communication rather than a linguistic 2512 heritage. There are many sign languages which have developed 2513 independently and the subtag 'sgn' indicates only the presence of a 2514 sign language. A number of sign languages also had grandfathered 2515 tags registered for them during the RFC 3066 era. 2517 Sign languages also provide this mechanism. Thus, a document in 2518 American Sign Language can be labeled either "ase" or "sgn-ase" (the 2519 'ase' subtag is for the language called 'American Sign Language'). 2521 4.2. Meaning of the Language Tag 2523 The meaning of a language tag is related to the meaning of the 2524 subtags that it contains. Each subtag, in turn, implies a certain 2525 range of expectations one might have for related content, although it 2526 is not a guarantee. For example, the use of a script subtag such as 2527 'Arab' (Arabic script) does not mean that the content contains only 2528 Arabic characters. It does mean that the language involved is 2529 predominantly in the Arabic script. Thus a language tag and its 2530 subtags can encompass a very wide range of variation and yet remain 2531 appropriate in each particular instance. 2533 Validity of a tag is not the only factor determining its usefulness. 2534 While every valid tag has a meaning, it might not represent any real- 2535 world language usage. This is unavoidable in a system in which 2536 subtags can be combined freely. For example, tags such as 2537 "ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia ) or "tlh- 2538 Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA 2539 phonetic transcription) are both valid and unlikely to represent a 2540 useful combination of language attributes. 2542 The meaning of a given tag doesn't depend on the context in which it 2543 appears. The relationship between a tag's meaning and the 2544 information objects to which that tag is applied, however, can vary. 2546 o For a single information object, the associated language tags 2547 might be interpreted as the set of languages that is necessary for 2548 a complete comprehension of the complete object. Example: Plain 2549 text documents. 2551 o For an aggregation of information objects, the associated language 2552 tags could be taken as the set of languages used inside components 2553 of that aggregation. Examples: Document stores and libraries. 2555 o For information objects whose purpose is to provide alternatives, 2556 the associated language tags could be regarded as a hint that the 2557 content is provided in several languages and that one has to 2558 inspect each of the alternatives in order to find its language or 2559 languages. In this case, the presence of multiple tags might not 2560 mean that one needs to be multi-lingual to get complete 2561 understanding of the document. Example: MIME multipart/ 2562 alternative. 2564 o In markup languages, such as HTML and XML, language information 2565 can be added to each part of the document identified by the markup 2566 structure (including the whole document itself). For example, one 2567 could write C'est la vie. inside a 2568 Norwegian document; the Norwegian-speaking user could then access 2569 a French-Norwegian dictionary to find out what the marked section 2570 meant. If the user were listening to that document through a 2571 speech synthesis interface, this formation could be used to signal 2572 the synthesizer to appropriately apply French text-to-speech 2573 pronunciation rules to that span of text, instead of applying the 2574 inappropriate Norwegian rules. 2576 o Language tags form the basis for most implementations of locale 2577 identifiers. For example, see Unicode's CLDR (Common Locale Data 2578 Repository) project. 2580 Language tags are related when they contain a similar sequence of 2581 subtags. For example, if a language tag B contains language tag A as 2582 a prefix, then B is typically "narrower" or "more specific" than A. 2583 Thus, "zh-Hant-TW" is more specific than "zh-Hant". 2585 This relationship is not guaranteed in all cases: specifically, 2586 languages that begin with the same sequence of subtags are NOT 2587 guaranteed to be mutually intelligible, although they might be. For 2588 example, the tag "az" shares a prefix with both "az-Latn" 2589 (Azerbaijani written using the Latin script) and "az-Cyrl" 2590 (Azerbaijani written using the Cyrillic script). A person fluent in 2591 one script might not be able to read the other, even though the text 2592 might be identical. Content tagged as "az" most probably is written 2593 in just one script and thus might not be intelligible to a reader 2594 familiar with the other script. 2596 Similarly, not all subtags specify an actual distinction in language. 2597 For example, the tags "en-US" and "en-CA" mean, roughly, English with 2598 features generally thought to be characteristic of the United States 2599 and Canada, respectively. They do not imply that a significant 2600 dialectical boundary exists between any arbitrarily selected point in 2601 the United States and any arbitrarily selected point in Canada. 2602 Neither does a particular region subtag imply that linguistic 2603 distinctions do not exist within that region. 2605 4.3. Lists of Languages 2607 In some applications, a single content item might best be associated 2608 with more than one language tag. Examples of such a usage include: 2610 o A language priority list [RFC4647] describing a user's language 2611 preferences. This is a (possibly weighted) list of potentially- 2612 unrelated varieties, expressing a preference, rather than as a 2613 declaration about actual content. 2615 o Content items that contain multiple, distinct varieties. Often 2616 this is used to indicate an appropriate audience for a given 2617 content item when multiple choices might be appropriate. Examples 2618 of this could include: 2620 * Metadata about the appropriate audience for a movie title. For 2621 example, a DVD might label its individual audio tracks 'de' 2622 (German), 'fr' (French), and 'es' (Spanish), but the overall 2623 title would list "de, fr, es" as its overall audience. 2625 * A French/English, English/French dictionary tagged as both "en" 2626 and "fr" to specify that it applies equally to French and 2627 English 2629 * A side-by-side or interlinear translation of a document, as is 2630 commonly done with classical works in Latin or Greek 2632 o Content items that contain a single language but which require 2633 multiple levels of specificity. For example, a library might wish 2634 to classify a particular work as both Norwegian ('no') and as 2635 Nynorsk ('nn') for audiences capable of appreciating the 2636 distinction or needing to select content more narrowly. 2638 4.4. Length Considerations 2640 There is no defined upper limit on the size of language tags. While 2641 historically most language tags have consisted of language and region 2642 subtags with a combined total length of up to six characters, larger 2643 tags have always been both possible and actually appeared in use. 2645 Neither the language tag syntax nor other requirements in this 2646 document impose a fixed upper limit on the number of subtags in a 2647 language tag (and thus an upper bound on the size of a tag). The 2648 language tag syntax suggests that, depending on the specific 2649 language, more subtags (and thus a longer tag) are sometimes 2650 necessary to completely identify the language for certain 2651 applications; thus, it is possible to envision long or complex subtag 2652 sequences. 2654 4.4.1. Working with Limited Buffer Sizes 2656 Some applications and protocols are forced to allocate fixed buffer 2657 sizes or otherwise limit the length of a language tag. A conformant 2658 implementation or specification MAY refuse to support the storage of 2659 language tags that exceed a specified length. Any such limitation 2660 SHOULD be clearly documented, and such documentation SHOULD include 2661 what happens to longer tags (for example, whether an error value is 2662 generated or the language tag is truncated). A protocol that allows 2663 tags to be truncated at an arbitrary limit, without giving any 2664 indication of what that limit is, has the potential for causing harm 2665 by changing the meaning of tags in substantial ways. 2667 In practice, most language tags do not require more than a few 2668 subtags and will not approach reasonably sized buffer limitations; 2669 see Section 4.1. 2671 Some specifications or protocols have limits on tag length but do not 2672 have a fixed length limitation. For example, [RFC2231] has no 2673 explicit length limitation: the length available for the language tag 2674 is constrained by the length of other header components (such as the 2675 charset's name) coupled with the 76-character limit in [RFC2047]. 2676 Thus, the "limit" might be 50 or more characters, but it could 2677 potentially be quite small. 2679 The considerations for assigning a buffer limit are: 2681 Implementations SHOULD NOT truncate language tags unless the 2682 meaning of the tag is purposefully being changed, or unless the 2683 tag does not fit into a limited buffer size specified by a 2684 protocol for storage or transmission. 2686 Implementations SHOULD warn the user when a tag is truncated since 2687 truncation changes the semantic meaning of the tag. 2689 Implementations of protocols or specifications that are space 2690 constrained but do not have a fixed limit SHOULD use the longest 2691 possible tag in preference to truncation. 2693 Protocols or specifications that specify limited buffer sizes for 2694 language tags MUST allow for language tags of up to 33 characters. 2696 Protocols or specifications that specify limited buffer sizes for 2697 language tags SHOULD allow for language tags of at least 30 2698 characters. Note that RFC 4646 [RFC4646] recommended a field size 2699 of 42 character because it included the permanently reserved (and 2700 unused) 'extlang' production. The current size recommendation 2701 does not include the use of the 'extlang' field. Protocols or 2702 specifications that commonly use extensions or private use subtags 2703 might wish to reserve or recommend a longer "minimum buffer" size. 2705 The following illustration shows how the 30-character recommendation 2706 was derived: 2708 language = 3 (ISO 639-2; ISO 639-1 requires 2) 2709 script = 5 (if not suppressed: see Section 4.1) 2710 region = 4 (UN M.49; ISO 3166-1 requires 3) 2711 variant1 = 9 (needs 'language' as a prefix) 2712 variant2 = 9 (needs 'language-variant1' as a prefix) 2714 total = 30 characters 2716 Figure 7: Derivation of the Limit on Tag Length 2718 4.4.2. Truncation of Language Tags 2720 Truncation of a language tag alters the meaning of the tag, and thus 2721 SHOULD be avoided. However, truncation of language tags is sometimes 2722 necessary due to limited buffer sizes. Such truncation MUST NOT 2723 permit a subtag to be chopped off in the middle or the formation of 2724 invalid tags (for example, one ending with the "-" character). 2726 This means that applications or protocols that truncate tags MUST do 2727 so by progressively removing subtags along with their preceding "-" 2728 from the right side of the language tag until the tag is short enough 2729 for the given buffer. If the resulting tag ends with a single- 2730 character subtag, that subtag and its preceding "-" MUST also be 2731 removed. For example: 2733 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 2734 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 2735 2. zh-Latn-CN-variant1-a-extend1 2736 3. zh-Latn-CN-variant1 2737 4. zh-Latn-CN 2738 5. zh-Latn 2739 6. zh 2741 Figure 8: Example of Tag Truncation 2743 4.5. Canonicalization of Language Tags 2745 Since a particular language tag is sometimes used by many processes, 2746 language tags SHOULD always be created or generated in a canonical 2747 form. 2749 A language tag is in canonical form when: 2751 1. The tag is well-formed according the rules in Section 2.1 and 2752 Section 2.2. 2754 2. Subtags of type 'Region' that have a Preferred-Value mapping in 2755 the IANA registry (see Section 3.1) MUST be replaced with their 2756 mapped value. 2758 3. Redundant or grandfathered tags that have a Preferred-Value 2759 mapping in the IANA registry (see Section 3.1) MUST be replaced 2760 with their mapped value. These items either are deprecated 2761 mappings created before the adoption of this document (such as 2762 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 2763 the result of later registrations or additions to this document 2764 (for example, "zh-hakka" was deprecated in favor of the ISO 639-3 2765 code 'hak' when this document was adopted). 2767 4. Other subtags that have a Preferred-Value mapping in the IANA 2768 registry (see Section 3.1) MUST be replaced with their mapped 2769 value. These items consist entirely of clerical corrections to 2770 ISO 639-1 in which the deprecated subtags have been maintained 2771 for compatibility purposes. 2773 5. If more than one extension subtag sequence exists, the extension 2774 sequences are ordered into case-insensitive ASCII order by 2775 singleton subtag. 2777 Example: The language tag "en-a-aaa-b-ccc-bbb-x-xyz" is in canonical 2778 form, while "en-b-ccc-bbb-a-aaa-X-xyz" is well-formed and potentially 2779 valid (extensions 'a' and 'b' are not defined as of the publication 2780 of this document) but not in canonical form (the extensions are not 2781 in alphabetical order). 2783 Example: The language tag "en-BU" (English as used in Burma) is not 2784 canonical because the 'BU' subtag has a canonical mapping to 'MM' 2785 (Myanmar), although the tag "en-BU" maintains its validity. 2787 Canonicalization of language tags does not imply anything about the 2788 use of upper or lowercase letters when processing or comparing 2789 subtags (and as described in Section 2.1). All comparisons MUST be 2790 performed in a case-insensitive manner. 2792 When performing canonicalization of language tags, processors MAY 2793 regularize the case of the subtags (that is, this process is 2794 OPTIONAL), following the case used in the registry. Note that this 2795 corresponds to the following casing rules: uppercase all non-initial 2796 two-letter subtags; titlecase all non-initial four-letter subtags; 2797 lowercase everything else. 2799 Note: Case folding of ASCII letters in certain locales, unless 2800 carefully handled, sometimes produces non-ASCII character values. 2801 The Unicode Character Database file "SpecialCasing.txt" defines the 2802 specific cases that are known to cause problems with this. In 2803 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 2804 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 2805 Implementers SHOULD specify a locale-neutral casing operation to 2806 ensure that case folding of subtags does not produce this value, 2807 which is illegal in language tags. For example, if one were to 2808 uppercase the region subtag 'in' using Turkish locale rules, the 2809 sequence U+0130 U+004E would result instead of the expected 'IN'. 2811 Note: if the field 'Deprecated' appears in a registry record without 2812 an accompanying 'Preferred-Value' field, then that tag or subtag is 2813 deprecated without a replacement. Validating processors SHOULD NOT 2814 generate tags that include these values, although the values are 2815 canonical when they appear in a language tag. 2817 An extension MUST define any relationships that exist between the 2818 various subtags in the extension and thus MAY define an alternate 2819 canonicalization scheme for the extension's subtags. Extensions MAY 2820 define how the order of the extension's subtags are interpreted. For 2821 example, an extension could define that its subtags are in canonical 2822 order when the subtags are placed into ASCII order: that is, "en-a- 2823 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 2824 define that the order of the subtags influences their semantic 2825 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 2826 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 2827 so that they are tolerant of the typical processes described in 2828 Section 3.7. 2830 4.6. Considerations for Private Use Subtags 2832 Private use subtags, like all other subtags, MUST conform to the 2833 format and content constraints in the ABNF. Private use subtags have 2834 no meaning outside the private agreement between the parties that 2835 intend to use or exchange language tags that employ them. The same 2836 subtags MAY be used with a different meaning under a separate private 2837 agreement. They SHOULD NOT be used where alternatives exist and 2838 SHOULD NOT be used in content or protocols intended for general use. 2840 Private use subtags are simply useless for information exchange 2841 without prior arrangement. The value and semantic meaning of private 2842 use tags and of the subtags used within such a language tag are not 2843 defined by this document. 2845 Subtags defined in the IANA registry as having a specific private use 2846 meaning convey more information that a purely private use tag 2847 prefixed by the singleton subtag 'x'. For applications, this 2848 additional information MAY be useful. 2850 For example, the region subtags 'AA', 'ZZ', and in the ranges 2851 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166-1 private use codes) 2852 MAY be used to form a language tag. A tag such as "zh-Hans-XQ" 2853 conveys a great deal of public, interchangeable information about the 2854 language material (that it is Chinese in the simplified Chinese 2855 script and is suitable for some geographic region 'XQ'). While the 2856 precise geographic region is not known outside of private agreement, 2857 the tag conveys far more information than an opaque tag such as 2858 "x-someLang", which contains no information about the language subtag 2859 or script subtag outside of the private agreement. 2861 However, in some cases content tagged with private use subtags MAY 2862 interact with other systems in a different and possibly unsuitable 2863 manner compared to tags that use opaque, privately defined subtags, 2864 so the choice of the best approach sometimes depends on the 2865 particular domain in question. 2867 5. IANA Considerations 2869 This section deals with the processes and requirements necessary for 2870 IANA to undertake to maintain the subtag and extension registries as 2871 defined by this document and in accordance with the requirements of 2872 [RFC2434]. 2874 The impact on the IANA maintainers of the two registries defined by 2875 this document will be a small increase in the frequency of new 2876 entries or updates. IANA also is required to create a new mailing 2877 list (described below in Section 5.1) to announce registry changes 2878 and updates. 2880 5.1. Language Subtag Registry 2882 Upon adoption of this document, IANA will update the registry using 2883 instructions and content provided in a companion document: 2884 [registry-update]. The criteria and process for selecting the 2885 updated set of records are described in that document. The updated 2886 set of records represents no impact on IANA, since the work to create 2887 it will be performed externally. 2889 Future work on the Language Subtag Registry includes the following 2890 activities: 2892 o Inserting or replacing whole records. These records are 2893 preformatted for IANA by the Language Subtag Reviewer, as 2894 described in Section 3.3. 2896 o Archiving and making publicly available the registration forms. 2898 o Announcing each updated version of the registry on the 2899 "ietf-languages-announcements@iana.org" mailing list. 2901 Each registration form sent to IANA contains a single record for 2902 incorporation into the registry. The form will be sent to 2903 "iana@iana.org" by the Language Subtag Reviewer. It will have a 2904 subject line indicating whether the enclosed form represents an 2905 insertion of a new record (indicated by the word "INSERT" in the 2906 subject line) or a replacement of an existing record (indicated by 2907 the word "MODIFY" in the subject line). At no time can a record be 2908 deleted from the registry. 2910 IANA will extract the record from the form and place the inserted or 2911 modified record into the appropriate section of the language subtag 2912 registry, grouping the records by their 'Type' field. Inserted 2913 records can be placed anywhere in the appropriate section; there is 2914 no guarantee of the order of the records beyond grouping them 2915 together by 'Type'. Modified records overwrite the record they 2916 replace. 2918 Whenever an entry is created or modified in the registry, the 'File- 2919 Date' record at the start of the registry is updated to reflect the 2920 most recent modification date in the [RFC3339] "full-date" format: 2921 included in any request to insert or modify records will be a new 2922 File-Date record indicating the acceptance date of the record. This 2923 record is to be placed first in the registry, replacing the existing 2924 File-Date record. In the event that the File-Date record present in 2925 the registry has a later date than the record being inserted or 2926 modified, then the latest (most recent) record will be preserved. 2927 IANA should attempt to process multiple registration requests in 2928 order according to the File-Date in the form, since one registration 2929 could otherwise cause a more recent change to be overwritten. 2931 The updated registry file MUST use the UTF-8 character encoding and 2932 IANA MUST check the registry file for proper encoding. Non-ASCII 2933 characters can be sent to IANA by attaching the registration form to 2934 the email message or by using various encodings in the mail message 2935 body (UTF-8 is recommended). IANA will verify any unclear or 2936 corrupted characters with the Language Subtag Reviewer prior to 2937 posting the updated registry. 2939 IANA will also archive and make publicly available from 2940 "http://www.iana.org/assignments/lang-subtags-templates/" each 2941 registration form. Note that multiple registrations can pertain to 2942 the same record in the registry. 2944 Developers who are dependent upon the language subtag registry 2945 sometimes would like to be informed of changes in the registry so 2946 that they can update their implementations. When any change is made 2947 to the language subtag registry, IANA will send an announcement 2948 message to "ietf-languages-announcements@iana.org" (a self- 2949 subscribing list that only IANA can post to). 2951 5.2. Extensions Registry 2953 The Language Tag Extensions Registry can contain at most 35 records 2954 and thus changes to this registry are expected to be very infrequent. 2956 Future work by IANA on the Language Tag Extensions Registry is 2957 limited to two cases. First, the IESG MAY request that new records 2958 be inserted into this registry from time to time. These requests 2959 MUST include the record to insert in the exact format described in 2960 Section 3.7. In addition, there MAY be occasional requests from the 2961 maintaining authority for a specific extension to update the contact 2962 information or URLs in the record. These requests MUST include the 2963 complete, updated record. IANA is not responsible for validating the 2964 information provided, only that it is properly formatted. It should 2965 reasonably be seen to come from the maintaining authority named in 2966 the record present in the registry. 2968 6. Security Considerations 2970 Language tags used in content negotiation, like any other information 2971 exchanged on the Internet, might be a source of concern because they 2972 might be used to infer the nationality of the sender, and thus 2973 identify potential targets for surveillance. 2975 This is a special case of the general problem that anything sent is 2976 visible to the receiving party and possibly to third parties as well. 2977 It is useful to be aware that such concerns can exist in some cases. 2979 The evaluation of the exact magnitude of the threat, and any possible 2980 countermeasures, is left to each application protocol (see BCP 72 2981 [RFC3552] for best current practice guidance on security threats and 2982 defenses). 2984 The language tag associated with a particular information item is of 2985 no consequence whatsoever in determining whether that content might 2986 contain possible homographs. The fact that a text is tagged as being 2987 in one language or using a particular script subtag provides no 2988 assurance whatsoever that it does not contain characters from scripts 2989 other than the one(s) associated with or specified by that language 2990 tag. 2992 Since there is no limit to the number of variant, private use, and 2993 extension subtags, and consequently no limit on the possible length 2994 of a tag, implementations need to guard against buffer overflow 2995 attacks. See Section 4.4 for details on language tag truncation, 2996 which can occur as a consequence of defenses against buffer overflow. 2998 Although the specification of valid subtags for an extension (see 2999 Section 3.7) MUST be available over the Internet, implementations 3000 SHOULD NOT mechanically depend on it being always accessible, to 3001 prevent denial-of-service attacks. 3003 7. Character Set Considerations 3005 The syntax in this document requires that language tags use only the 3006 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 3007 character sets, so the composition of language tags should not have 3008 any character set issues. 3010 Rendering of characters based on the content of a language tag is not 3011 addressed in this memo. Historically, some languages have relied on 3012 the use of specific character sets or other information in order to 3013 infer how a specific character should be rendered (notably this 3014 applies to language- and culture-specific variations of Han 3015 ideographs as used in Japanese, Chinese, and Korean). When language 3016 tags are applied to spans of text, rendering engines sometimes use 3017 that information in deciding which font to use in the absence of 3018 other information, particularly where languages with distinct writing 3019 traditions use the same characters. 3021 8. Changes from RFC 4646 3023 The main goal for this revision of this document was to incorporate 3024 two new parts of ISO 639 (ISO 639-3 and ISO 639-5) and their 3025 attendant sets of language codes into the IANA Language Subtag 3026 Registry. This permits the identification of many more languages and 3027 dialects than previously supported. 3029 The specific changes in this document to meet these goals are: 3031 o Defines the incorporation of ISO 639-3 and ISO 639-5 codes for use 3032 as primary and extended language subtags. It also permanently 3033 reserves and disallows the use of additional 'extlang' subtags. 3034 The changes necessary to achieve this were: 3036 * Modified the ABNF comments. 3038 * Updated various registration and stability requirements 3039 sections to reference ISO 639-3 and ISO 639-5 in addition to 3040 ISO 639-1 and ISO 639-2. 3042 * Edited the text to eliminate references to extended language 3043 subtags where they are no longer used. 3045 * Explained the change in the section on extended language 3046 subtags. 3048 o Changed the ABNF related to grandfathered tags. The irregular 3049 tags are now listed. Well-formed grandfathered tags are now 3050 described by the 'langtag' production and the 'grandfathered' 3051 production was removed as a result. Also: added description of 3052 both types of grandfathered tags to Section 2.2.8. 3054 o Added the paragraph on "collections" to Section 4.1. 3056 o Changed the capitalization rules for 'Tag' fields in Section 3.1. 3058 o Split section 3.1 up into subsections. 3060 o Modified section 3.5 to allow Suppress-Script fields to be added, 3061 modified, or removed via the registration process. This was an 3062 erratum from RFC 4646. 3064 o Modified examples that used region code 'CS' (formerly Serbia and 3065 Montenegro) to use 'RS' (Serbia) instead. 3067 o Modified the rules for creating and maintaining record 3068 'Description' fields to prevent duplicates, including inverted 3069 duplicates. 3071 o Removed the lengthy description of why RFC 4646 was created from 3072 this section, which also caused the removal of the reference to 3073 XML Schema. 3075 o Modified the text in section 2.1 to place more emphasis on the 3076 fact that language tags are not case sensitive. 3078 o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" 3079 and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the 3080 Suppress-Script on 'Latn' with 'fr'. 3082 o Changed the requirements for well-formedness to make singleton 3083 repetition checking optional (it is required for validity 3084 checking) in Section 2.2.9. 3086 o Changed the text in Section 2.2.9 referring to grandfathered 3087 checking to note that the list is now included in the ABNF. 3089 o Modified and added text to Section 3.2. The job description was 3090 placed first. A note was added making clear that the Language 3091 Subtag Reviewer may delegate various non-critical duties, 3092 including list moderation. Finally, additional text was added to 3093 make the appointment process clear and to clarify that decisions 3094 and performance of the reviewer are appealable. 3096 o Added text to Section 3.5 clarifying that the ietf-languages list 3097 is operated by whomever the IESG appoints. 3099 o Added text to Section 3.1.4 clarifying that the first Description 3100 in a 'language' record matches the corresponding Reference Name 3101 for the language in ISO 639-3. 3103 o Modified Section 2.2.9 to define classes of conformance related to 3104 specific tags (formerly 'well-formed' and 'valid' referred to 3105 implementations). Notes were added about the removal of 'extlang' 3106 from the ABNF provided in RFC 4646, allowing for well-formedness 3107 using this older definition. Reference to RFC 3066 well- 3108 formedness was also added. 3110 o Added text to the end of Section 3.1.2 noting that future versions 3111 of this document might add new field types to the Registry format 3112 and recommending that implementations ignore any unrecognized 3113 fields. 3115 o Added text about what the lack of a Suppress-Script field means in 3116 a record to Section 3.1.8. 3118 o Added text allowing the correction of misspellings and typographic 3119 errors to Section 3.1.4. 3121 o Added text to Section 3.1.7 disallowing Prefix field conflicts 3122 (such as circular prefix references). 3124 o Modified text in Section 3.5 to require the subtag reviewer to 3125 announce his/her decision (or extension) following the two-week 3126 period. Also clarified that any decision or failure to decide can 3127 be appealed. 3129 o Modified text in Section 4.1 to include the (heretofore anecdotal) 3130 guiding principle of tag choice, and clarifying the non-use of 3131 script subtags in non-written applications. Also updated examples 3132 in this section to use Chamic languages as an example of language 3133 collections. 3135 o Prohibited multiple use of the same variant in a tag (i.e. "de- 3136 1901-1901"). Previously this was only a recommendation 3137 ("SHOULD"). 3139 o Removed inappropriate [RFC2119] language from the illustration in 3140 Section 4.4.1. 3142 o Replaced the example of deprecating "zh-gouyu" with "zh- 3143 hakka"->"hak" in Section 4.5, noting that it was this document 3144 that caused the change. 3146 o Replaced the section in Section 4.1 dealing with "mul"/"und" to 3147 include the subtags 'zxx' and 'mis', as well as the tag 3148 "i-default". A normative reference to RFC 2277 was added, along 3149 with an informative reference to MARC21. 3151 o Added text to Section 3.5 clarifying that any modifications of a 3152 registration request must be sent to the ietf-languages list 3153 before submission to IANA. 3155 o Changed the ABNF for the record-jar format from using the LWSP 3156 production to use a folding whitespace production similar to obs- 3157 FWS in [RFC5234]. This effectively prevents unintentional blank 3158 lines inside a field. 3160 o Clarified and revised text in Section 3.3, Section 3.5, and 3161 Section 5.1 to clarify that the Language Subtag Reviewer sends the 3162 complete registration forms to IANA, that IANA extracts the record 3163 from the form, and that the forms must also be archived separately 3164 from the registry. 3166 o Added text to Section 5 requiring IANA to send an announcement to 3167 an ietf-languages-announce list whenever the registry is updated. 3169 o Modification of the registry to use UTF-8 as its character 3170 encoding. This also entails additional instructions to IANA and 3171 the Language Subtag Reviewer in the registration process. 3173 o Modified the rules in Section 2.2.4 so that "exceptionally 3174 reserved" ISO 3166-1 codes other than 'UK' were included into the 3175 registry. In particular, this allows the code 'EU' (European 3176 Union) to be used to form language tags or (more commonly) for 3177 applications that use the registry for region codes to reference 3178 this subtag. 3180 o Modified the IANA considerations section (Section 5) to remove 3181 unnecessary normative [RFC2119] language. 3183 9. References 3185 9.1. Normative References 3187 [ISO15924] 3188 International Organization for Standardization, "ISO 3189 15924:2004. Information and documentation -- Codes for the 3190 representation of names of scripts", January 2004. 3192 [ISO3166-1] 3193 International Organization for Standardization, "ISO 3166- 3194 1:2006. Codes for the representation of names of countries 3195 and their subdivisions -- Part 1: Country codes", 3196 November 2006. 3198 [ISO639-1] 3199 International Organization for Standardization, "ISO 639- 3200 1:2002. Codes for the representation of names of languages 3201 -- Part 1: Alpha-2 code", 2002. 3203 [ISO639-2] 3204 International Organization for Standardization, "ISO 639- 3205 2:1998. Codes for the representation of names of languages 3206 -- Part 2: Alpha-3 code, first edition", 1998. 3208 [ISO639-3] 3209 International Organization for Standardization, "ISO 639- 3210 3:2007. Codes for the representation of names of languages 3211 -- Part 3: Alpha-3 code for comprehensive coverage of 3212 languages", 2007. 3214 [ISO639-5] 3215 International Organization for Standardization, "ISO 639- 3216 5:1998. Codes for the representation of names of languages 3217 -- Part 5: Alpha-3 code for language families and groups", 3218 May 2008. 3220 [ISO646] International Organization for Standardization, "ISO/IEC 3221 646:1991, Information technology -- ISO 7-bit coded 3222 character set for information interchange.", 1991. 3224 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3225 3", BCP 9, RFC 2026, October 1996. 3227 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 3228 the IETF Standards Process", BCP 11, RFC 2028, 3229 October 1996. 3231 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3232 Requirement Levels", BCP 14, RFC 2119, March 1997. 3234 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and 3235 Languages", BCP 18, RFC 2277, January 1998. 3237 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3238 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 3239 October 1998. 3241 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 3242 Understanding Concerning the Technical Work of the 3243 Internet Assigned Numbers Authority", RFC 2860, June 2000. 3245 [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the 3246 Internet: Timestamps", RFC 3339, July 2002. 3248 [RFC4645] Ewell, D., "Initial Language Subtag Registry", RFC 4645, 3249 September 2006. 3251 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 3252 BCP 47, RFC 4647, September 2006. 3254 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 3255 Specifications: ABNF", STD 68, RFC 5234, January 2008. 3257 [UAX14] Freitag, A., "Unicode Standard Annex #14: Line Breaking 3258 Properties", August 2006, 3259 . 3261 [UN_M.49] Statistics Division, United Nations, "Standard Country or 3262 Area Codes for Statistical Use", UN Standard Country or 3263 Area Codes for Statistical Use, Revision 4 (United Nations 3264 publication, Sales No. 98.XVII.9, June 1999. 3266 9.2. Informative References 3268 [RFC1766] Alvestrand, H., "Tags for the Identification of 3269 Languages", RFC 1766, March 1995. 3271 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 3272 Part Three: Message Header Extensions for Non-ASCII Text", 3273 RFC 2047, November 1996. 3275 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 3276 Word Extensions: 3277 Character Sets, Languages, and Continuations", RFC 2231, 3278 November 1997. 3280 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 3281 10646", RFC 2781, February 2000. 3283 [RFC3066] Alvestrand, H., "Tags for the Identification of 3284 Languages", RFC 3066, January 2001. 3286 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 3287 Text on Security Considerations", BCP 72, RFC 3552, 3288 July 2003. 3290 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 3291 10646", STD 63, RFC 3629, November 2003. 3293 [RFC4646] Phillips, A. and M. Davis, "Tags for Identifying 3294 Languages", BCP 47, RFC 4646, September 2006. 3296 [UTS35] Davis, M., "Unicode Technical Standard #35: Locale Data 3297 Markup Language (LDML)", December 2007, 3298 . 3300 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 3301 Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. 3302 ISBN 0-321-49081-0)", January 2007. 3304 [iso639.prin] 3305 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 3306 Committee: Working principles for ISO 639 maintenance", 3307 March 2000, 3308 . 3311 [record-jar] 3312 Raymond, E., "The Art of Unix Programming", 2003, 3313 . 3315 [registry-update] 3316 Ewell, D., Ed., "Update to the Language Subtag Registry", 3317 September 2006, . 3320 Appendix A. Acknowledgements 3322 Any list of contributors is bound to be incomplete; please regard the 3323 following as only a selection from the group of people who have 3324 contributed to make this document what it is today. 3326 The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the 3327 precursors of this document, made enormous contributions directly or 3328 indirectly to this document and are generally responsible for the 3329 success of language tags. 3331 The following people contributed to this document: 3333 Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, 3334 Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion 3335 Gunn, Kent Karlsson, Chris Newman, Randy Presuhn, Stephen Silver, and 3336 many, many others. 3338 Very special thanks must go to Harald Tveit Alvestrand, who 3339 originated RFCs 1766 and 3066, and without whom this document would 3340 not have been possible. 3342 Special thanks go to Michael Everson, who served as the Language Tag 3343 Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as 3344 the Language Subtag Reviewer since the adoption of RFC 4646. 3346 Special thanks also to Doug Ewell, for his production of the first 3347 complete subtag registry, his work to support and maintain new 3348 registrations, and his careful editorship of both RFC 4645 and 3349 [registry-update]. 3351 Appendix B. Examples of Language Tags (Informative) 3353 Simple language subtag: 3355 de (German) 3357 fr (French) 3359 ja (Japanese) 3361 i-enochian (example of a grandfathered tag) 3363 Language subtag plus Script subtag: 3365 zh-Hant (Chinese written using the Traditional Chinese script) 3367 zh-Hans (Chinese written using the Simplified Chinese script) 3369 sr-Cyrl (Serbian written using the Cyrillic script) 3371 sr-Latn (Serbian written using the Latin script) 3373 Language-Script-Region: 3375 zh-Hans-CN (Chinese written using the Simplified script as used in 3376 mainland China) 3378 sr-Latn-RS (Serbian written using the Latin script as used in 3379 Serbia) 3381 Language-Variant: 3383 sl-rozaj (Resian dialect of Slovenian) 3385 sl-nedis (Nadiza dialect of Slovenian) 3387 Language-Region-Variant: 3389 de-CH-1901 (German as used in Switzerland using the 1901 variant 3390 [orthography]) 3392 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 3394 Language-Script-Region-Variant: 3396 hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as 3397 used in Italy) 3399 Language-Region: 3401 de-DE (German for Germany) 3403 en-US (English as used in the United States) 3405 es-419 (Spanish appropriate for the Latin America and Caribbean 3406 region using the UN region code) 3408 Private use subtags: 3410 de-CH-x-phonebk 3412 az-Arab-x-AZE-derbend 3414 Private use registry values: 3416 x-whatever (private use using the singleton 'x') 3418 qaa-Qaaa-QM-x-southern (all private tags) 3420 de-Qaaa (German, with a private script) 3422 sr-Latn-QM (Serbian, Latin-script, private region) 3424 sr-Qaaa-RS (Serbian, private script, for Serbia) 3426 Tags that use extensions (examples ONLY: extensions MUST be defined 3427 by revision or update to this document or by RFC): 3429 en-US-u-islamCal 3431 zh-CN-a-myExt-x-private 3433 en-a-myExt-b-another 3435 Some Invalid Tags: 3437 de-419-DE (two region tags) 3439 a-DE (use of a single-character subtag in primary position; note 3440 that there are a few grandfathered tags that start with "i-" that 3441 are valid) 3442 ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter 3443 prefix) 3445 Appendix C. Examples of Registration Forms 3446 LANGUAGE SUBTAG REGISTRATION FORM 3447 1. Name of requester: Han Steenwijk 3448 2. E-mail address of requester: han.steenwijk @ unipd.it 3449 3. Record Requested: 3451 Type: variant 3452 Subtag: biske 3453 Description: The San Giorgio dialect of Resian 3454 Description: The Bila dialect of Resian 3455 Prefix: sl-rozaj 3456 Comments: The dialect of San Giorgio/Bila is one of the 3457 four major local dialects of Resian 3459 4. Intended meaning of the subtag: The local variety of Resian as 3460 spoken in San Giorgio/Bila 3462 5. Reference to published description of the language (book or 3463 article): 3464 -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich 3465 govorov, Varsava - Peterburg: Vende - Kozancikov, 1875. 3467 LANGUAGE SUBTAG REGISTRATION FORM 3468 1. Name of requester: Jaska Zedlik 3469 2. E-mail address of requester: jz53 @ zedlik.com 3470 3. Record Requested: 3472 Type: variant 3473 Subtag: tarask 3474 Description: Belarusian in Taraskievica orthography 3475 Prefix: be 3476 Comments: The subtag represents Branislau Taraskievic's Belarusian 3477 orthography as published in "Bielaruski klasycny pravapis" by Juras 3478 Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka 3479 (Vilnia-Miensk 2005). 3481 4. Intended meaning of the subtag: 3483 The subtag is intended to represent the Belarusian orthography as 3484 published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk 3485 Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005). 3487 5. Reference to published description of the language (book or article): 3489 Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd. 3490 "Bielaruskaha kamitetu", 1929, 5th edition. 3492 Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier. 3493 Bielaruski klasycny pravapis. Vilnia-Miensk, 2005. 3495 6. Any other relevant information: 3497 Belarusian in Taraskievica orthography became widely used, especially in 3498 Belarusian-speaking Internet segment, but besides this some books and 3499 newspapers are also printed using this orthography of Belarusian. 3501 Authors' Addresses 3503 Addison Phillips (editor) 3504 Lab126 3506 Email: addison@inter-locale.com 3507 URI: http://www.inter-locale.com 3509 Mark Davis (editor) 3510 Google 3512 Email: mark.davis@google.com 3514 Full Copyright Statement 3516 Copyright (C) The IETF Trust (2008). 3518 This document is subject to the rights, licenses and restrictions 3519 contained in BCP 78, and except as set forth therein, the authors 3520 retain all their rights. 3522 This document and the information contained herein are provided on an 3523 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 3524 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 3525 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 3526 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 3527 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 3528 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 3530 Intellectual Property 3532 The IETF takes no position regarding the validity or scope of any 3533 Intellectual Property Rights or other rights that might be claimed to 3534 pertain to the implementation or use of the technology described in 3535 this document or the extent to which any license under such rights 3536 might or might not be available; nor does it represent that it has 3537 made any independent effort to identify any such rights. 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