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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 (April 29, 2008) is 5842 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. '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 (==), 18 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: October 31, 2008 April 29, 2008 8 Tags for Identifying Languages 9 draft-ietf-ltru-4646bis-13 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on October 31, 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 . . . . . . . . . . . . . . . . . . . . 11 53 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 12 54 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 14 55 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 15 56 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 17 57 2.2.8. Grandfathered Registrations . . . . . . . . . . . . . 17 58 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 18 59 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 20 60 3.1. Format of the IANA Language Subtag Registry . . . . . . . 20 61 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 20 62 3.1.2. Record Definitions . . . . . . . . . . . . . . . . . . 21 63 3.1.3. Subtag and Tag Fields . . . . . . . . . . . . . . . . 24 64 3.1.4. Description Field . . . . . . . . . . . . . . . . . . 24 65 3.1.5. Deprecated Field . . . . . . . . . . . . . . . . . . . 25 66 3.1.6. Preferred-Value Field . . . . . . . . . . . . . . . . 25 67 3.1.7. Prefix Field . . . . . . . . . . . . . . . . . . . . . 27 68 3.1.8. Suppress-Script Field . . . . . . . . . . . . . . . . 27 69 3.1.9. Macrolanguage Field . . . . . . . . . . . . . . . . . 28 70 3.1.10. Comments Field . . . . . . . . . . . . . . . . . . . . 28 71 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 29 72 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 29 73 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 30 74 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 34 75 3.6. Possibilities for Registration . . . . . . . . . . . . . . 38 76 3.7. Extensions and the Extensions Registry . . . . . . . . . . 40 77 3.8. Update of the Language Subtag Registry . . . . . . . . . . 43 78 4. Formation and Processing of Language Tags . . . . . . . . . . 44 79 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 44 80 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 49 81 4.3. Length Considerations . . . . . . . . . . . . . . . . . . 51 82 4.3.1. Working with Limited Buffer Sizes . . . . . . . . . . 51 83 4.3.2. Truncation of Language Tags . . . . . . . . . . . . . 52 84 4.4. Canonicalization of Language Tags . . . . . . . . . . . . 53 85 4.5. Considerations for Private Use Subtags . . . . . . . . . . 55 86 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56 87 5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 56 88 5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 57 89 6. Security Considerations . . . . . . . . . . . . . . . . . . . 59 90 7. Character Set Considerations . . . . . . . . . . . . . . . . . 60 91 8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 61 92 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 65 93 9.1. Normative References . . . . . . . . . . . . . . . . . . . 65 94 9.2. Informative References . . . . . . . . . . . . . . . . . . 66 95 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 68 96 Appendix B. Examples of Language Tags (Informative) . . . . . . . 69 97 Appendix C. Examples of Registration Forms . . . . . . . . . . . 72 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 74 99 Intellectual Property and Copyright Statements . . . . . . . . . . 75 101 1. Introduction 103 Human beings on our planet have, past and present, used a number of 104 languages. There are many reasons why one would want to identify the 105 language used when presenting or requesting information. 107 A user's language preferences often need to be identified so that 108 appropriate processing can be applied. For example, the user's 109 language preferences in a Web browser can be used to select Web pages 110 appropriately. Language preferences can also be used to select among 111 tools (such as dictionaries) to assist in the processing or 112 understanding of content in different languages. 114 In addition, knowledge about the particular language used by some 115 piece of information content might be useful or even required by some 116 types of processing; for example, spell-checking, computer- 117 synthesized speech, Braille transcription, or high-quality print 118 renderings. 120 One means of indicating the language used is by labeling the 121 information content with an identifier or "tag". These tags can be 122 used to specify user preferences when selecting information content, 123 or for labeling additional attributes of content and associated 124 resources. 126 Tags can also be used to indicate additional language attributes of 127 content. For example, indicating specific information about the 128 dialect, writing system, or orthography used in a document or 129 resource may enable the user to obtain information in a form that 130 they can understand, or it can be important in processing or 131 rendering the given content into an appropriate form or style. 133 This document specifies a particular identifier mechanism (the 134 language tag) and a registration function for values to be used to 135 form tags. It also defines a mechanism for private use values and 136 future extension. 138 This document replaces [RFC4646], which replaced [RFC3066] and its 139 predecessor [RFC1766]. For a list of changes in this document, see 140 Section 8. 142 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 143 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 144 document are to be interpreted as described in [RFC2119]. 146 2. The Language Tag 148 Language tags are used to help identify languages, whether spoken, 149 written, signed, or otherwise signaled, for the purpose of 150 communication. This includes constructed and artificial languages, 151 but excludes languages not intended primarily for human 152 communication, such as programming languages. 154 2.1. Syntax 156 The language tag is composed of one or more parts, known as 157 "subtags". Each subtag consists of a sequence of alphanumeric 158 characters. Subtags are distinguished and separated from one another 159 by a hyphen ("-", ABNF [RFC5234] %x2D). Usually a language tag 160 contains a "primary language" subtag, followed by a (possibly empty) 161 series of subsequent subtags, each of which refines or narrows the 162 range of languages identified by the overall tag. 164 Most subtags are distinguished by length, position in the tag, and 165 content: subtags can be recognized solely by these features. This 166 makes it possible to construct a parser that can extract and assign 167 some semantic information to the subtags, even if the specific subtag 168 values are not recognized. Thus, a parser need not have a list of 169 valid tags or subtags (that is, a copy of some version of the IANA 170 Language Subtag Registry) in order to perform common searching and 171 matching operations. The grandfathered tags registered under RFC 172 3066 [RFC3066], a fixed list that can never change, are the only 173 exception to this ability to infer meaning from subtag structure. 175 The syntax of the language tag in ABNF [RFC5234] is: 177 Language-Tag = langtag 178 / privateuse ; private use tag 179 / irregular ; tags grandfathered by rule 181 langtag = (language 182 ["-" script] 183 ["-" region] 184 *("-" variant) 185 *("-" extension) 186 ["-" privateuse]) 188 language = 2*3ALPHA ; shortest ISO 639 code 189 / 4ALPHA ; reserved for future use 190 / 5*8ALPHA ; registered language subtag 192 script = 4ALPHA ; ISO 15924 code 194 region = 2ALPHA ; ISO 3166-1 code 195 / 3DIGIT ; UN M.49 code 197 variant = 5*8alphanum ; registered variants 198 / (DIGIT 3alphanum) 200 extension = singleton 1*("-" (2*8alphanum)) 202 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 203 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 204 ; Single alphanumerics 205 ; "x" is reserved for private use 207 privateuse = "x" 1*("-" (1*8alphanum)) 209 irregular = "en-GB-oed" / "i-ami" / "i-bnn" / "i-default" 210 / "i-enochian" / "i-hak" / "i-klingon" / "i-lux" 211 / "i-mingo" / "i-navajo" / "i-pwn" / "i-tao" 212 / "i-tay" / "i-tsu" / "no-bok" / "no-nyn" 213 / "sgn-BE-FR" / "sgn-BE-NL" / "sgn-CH-DE" / "zh-cmn" 214 / "zh-cmn-Hans" / "zh-cmn-Hant" / "zh-gan" 215 / "zh-min" / "zh-min-nan" / "zh-wuu" / "zh-yue" 217 alphanum = (ALPHA / DIGIT) ; letters and numbers 219 Figure 1: Language Tag ABNF 221 All subtags have a maximum length of eight characters and whitespace 222 is not permitted in a language tag. There is a subtlety in the ABNF 223 production 'variant': variants starting with a digit MAY be four 224 characters long, while those starting with a letter MUST be at least 225 five characters long. For examples of language tags, see Appendix B. 227 Note Well: the ABNF syntax does not distinguish between upper and 228 lowercase. The appearance of upper and lowercase letters in the 229 various ABNF productions above do not affect how implementations 230 interpret tags. That is, the tag "I-AMI" matches the item "i-ami" in 231 the 'irregular' production. At all times, the tags and their 232 subtags, including private use and extensions, are to be treated as 233 case insensitive: there exist conventions for the capitalization of 234 some of the subtags, but these MUST NOT be taken to carry meaning. 236 For example: 238 o [ISO639-1] recommends that language codes be written in lowercase 239 ('mn' Mongolian). 241 o [ISO3166-1] recommends that country codes be capitalized ('MN' 242 Mongolia). 244 o [ISO15924] recommends that script codes use lowercase with the 245 initial letter capitalized ('Cyrl' Cyrillic). 247 However, in the tags defined by this document, the uppercase US-ASCII 248 letters in the range 'A' through 'Z' are considered equivalent and 249 mapped directly to their US-ASCII lowercase equivalents in the range 250 'a' through 'z'. Thus, the tag "mn-Cyrl-MN" is not distinct from 251 "MN-cYRL-mn" or "mN-cYrL-Mn" (or any other combination), and each of 252 these variations conveys the same meaning: Mongolian written in the 253 Cyrillic script as used in Mongolia. 255 Although case distinctions do not carry meaning in language tags, 256 consistent formatting and presentation of the tags will aid users. 257 The format of the tags and subtags in the registry is RECOMMENDED. 258 In this format, all subtags, including all those following singletons 259 (that is, in extension or private-use sequences) are in lowercase. 260 The exceptions to this are: all other non-initial two-letter subtags 261 are uppercase and all other non-initial four-letter subtags are 262 titlecase. 264 Note that although [RFC5234] refers to octets, the language tags 265 described in this document are sequences of characters from the US- 266 ASCII [ISO646] repertoire. Language tags MAY be used in documents 267 and applications that use other encodings, so long as these encompass 268 the US-ASCII repertoire. An example of this would be an XML document 269 that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 271 2.2. Language Subtag Sources and Interpretation 273 The namespace of language tags and their subtags is administered by 274 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 275 the rules in Section 5 of this document. The Language Subtag 276 Registry maintained by IANA is the source for valid subtags: other 277 standards referenced in this section provide the source material for 278 that registry. 280 Terminology used in this document: 282 o "Tag" refers to a complete language tag, such as "sr-Latn-RS" or 283 "az-Arab-IR". Examples of tags in this document are enclosed in 284 double-quotes ("en-US"). 286 o "Subtag" refers to a specific section of a tag, delimited by 287 hyphen, such as the subtag 'Hant' in "zh-Hant-CN". Examples of 288 subtags in this document are enclosed in single quotes ('Hant'). 290 o "Code" refers to values defined in external standards (and which 291 are used as subtags in this document). For example, 'Hant' is an 292 [ISO15924] script code that was used to define the 'Hant' script 293 subtag for use in a language tag. Examples of codes in this 294 document are enclosed in single quotes ('en', 'Hant'). 296 The definitions in this section apply to the various subtags within 297 the language tags defined by this document, excepting those 298 "grandfathered" tags defined in Section 2.2.8. 300 Language tags are designed so that each subtag type has unique length 301 and content restrictions. These make identification of the subtag's 302 type possible, even if the content of the subtag itself is 303 unrecognized. This allows tags to be parsed and processed without 304 reference to the latest version of the underlying standards or the 305 IANA registry and makes the associated exception handling when 306 parsing tags simpler. 308 Subtags in the IANA registry that do not come from an underlying 309 standard can only appear in specific positions in a tag. 310 Specifically, they can only occur as primary language subtags or as 311 variant subtags. 313 Note that sequences of private use and extension subtags MUST occur 314 at the end of the sequence of subtags and MUST NOT be interspersed 315 with subtags defined elsewhere in this document. 317 Single-letter and single-digit subtags are reserved for current or 318 future use. These include the following current uses: 320 o The single-letter subtag 'x' is reserved to introduce a sequence 321 of private use subtags. The interpretation of any private use 322 subtags is defined solely by private agreement and is not defined 323 by the rules in this section or in any standard or registry 324 defined in this document. 326 o All other single-letter subtags are reserved to introduce 327 standardized extension subtag sequences as described in 328 Section 3.7. 330 o The single-letter subtag 'i' is used by some grandfathered tags, 331 such as "i-default", where it always appears in the first position 332 and cannot be confused with an extension. 334 2.2.1. Primary Language Subtag 336 The primary language subtag is the first subtag in a language tag 337 (with the exception of private use and certain grandfathered tags) 338 and cannot be omitted. The following rules apply to the primary 339 language subtag: 341 1. All two-character primary language subtags were defined in the 342 IANA registry according to the assignments found in the standard 343 ISO 639 Part 1, "ISO 639-1:2002, Codes for the representation of 344 names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using 345 assignments subsequently made by the ISO 639-1 registration 346 authority (RA) or governing standardization bodies. 348 2. All three-character primary language subtags were defined in the 349 IANA registry according to the assignments found in either ISO 350 639 Part 2, "ISO 639-2:1998 - Codes for the representation of 351 names of languages -- Part 2: Alpha-3 code - edition 1" 352 [ISO639-2], ISO 639 Part 3, "Codes for the representation of 353 names of languages -- Part 3: Alpha-3 code for comprehensive 354 coverage of languages" [ISO639-3], or assignments subsequently 355 made by the relevant ISO 639 registration authorities or 356 governing standardization bodies. 358 3. The subtags in the range 'qaa' through 'qtz' are reserved for 359 private use in language tags. These subtags correspond to codes 360 reserved by ISO 639-2 for private use. These codes MAY be used 361 for non-registered primary language subtags (instead of using 362 private use subtags following 'x-'). Please refer to Section 4.5 363 for more information on private use subtags. 365 4. All four-character language subtags are reserved for possible 366 future standardization. 368 5. All language subtags of 5 to 8 characters in length in the IANA 369 registry were defined via the registration process in Section 3.5 370 and MAY be used to form the primary language subtag. At the time 371 this document was created, there were no examples of this kind of 372 subtag and future registrations of this type will be discouraged: 373 primary languages are strongly RECOMMENDED for registration with 374 ISO 639, and proposals rejected by ISO 639/RA-JAC will be closely 375 scrutinized before they are registered with IANA. 377 6. The single-character subtag 'x' as the primary subtag indicates 378 that the language tag consists solely of subtags whose meaning is 379 defined by private agreement. For example, in the tag "x-fr-CH", 380 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 381 French language or the country of Switzerland (or any other value 382 in the IANA registry) unless there is a private agreement in 383 place to do so. See Section 4.5. 385 7. The single-character subtag 'i' is used by some grandfathered 386 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 387 grandfathered tags have a primary language subtag in their first 388 position.) 390 8. Other values MUST NOT be assigned to the primary subtag except by 391 revision or update of this document. 393 Note: For languages that have both an ISO 639-1 two-character code 394 and a three character code assigned by either ISO 639-2 or ISO 639-3, 395 only the ISO 639-1 two-character code is defined in the IANA 396 registry. 398 Note: For languages that have no ISO 639-1 two-character code and for 399 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 400 (Bibliographic) codes differ, only the Terminology code is defined in 401 the IANA registry. At the time this document was created, all 402 languages that had both kinds of three-character code were also 403 assigned a two-character code; it is expected that future assignments 404 of this nature will not occur. 406 Note: To avoid problems with versioning and subtag choice as 407 experienced during the transition between RFC 1766 and RFC 3066, as 408 well as the canonical nature of subtags defined by this document, the 409 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 410 RA-JAC) has included the following statement in [iso639.prin]: 412 "A language code already in ISO 639-2 at the point of freezing ISO 413 639-1 shall not later be added to ISO 639-1. This is to ensure 414 consistency in usage over time, since users are directed in 415 Internet applications to employ the alpha-3 code when an alpha-2 416 code for that language is not available." 418 In order to avoid instability in the canonical form of tags, if a 419 two-character code is added to ISO 639-1 for a language for which a 420 three-character code was already included in either ISO 639-2 or ISO 421 639-3, the two-character code MUST NOT be registered. See 422 Section 3.4. 424 For example, if some content were tagged with 'haw' (Hawaiian), which 425 currently has no two-character code, the tag would not be invalidated 426 if ISO 639-1 were to assign a two-character code to the Hawaiian 427 language at a later date. 429 Note: An example of independent primary language subtag registration 430 might include: one of the grandfathered IANA registrations is 431 "i-enochian". The subtag 'enochian' could be registered in the IANA 432 registry as a primary language subtag (assuming that ISO 639 does not 433 register this language first), making tags such as "enochian-AQ" and 434 "enochian-Latn" valid. 436 2.2.2. Extended Language Subtags 438 [RFC4646] contained an additional type of subtag called the 'extended 439 language subtag' to allow for certain kinds of compatibility mappings 440 which ultimately were not used. These subtags were reserved for 441 future use and ultimately removed from the ABNF. They MUST NOT be 442 registered or used to form language tags. See also Section 2.2.9 for 443 a discussion of the consequences of removing the 'extlang' production 444 from grammar. 446 Note: a few grandfathered tags (Section 2.2.8) matched the 'extlang' 447 production in RFC 4646, and thus were not considered 'irregular'. 448 These tags are still valid and were added to the 'irregular' 449 production in the ABNF. 451 2.2.3. Script Subtag 453 Script subtags are used to indicate the script or writing system 454 variations that distinguish the written forms of a language or its 455 dialects. The following rules apply to the script subtags: 457 1. Script subtags MUST follow the primary language subtag and MUST 458 precede any other type of subtag. 460 2. All four-character subtags were defined according to 461 [ISO15924]--"Codes for the representation of the names of 462 scripts": alpha-4 script codes, or subsequently assigned by the 463 ISO 15924 maintenance agency or governing standardization bodies, 464 denoting the script or writing system used in conjunction with 465 this language. 467 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 468 use in language tags. These subtags correspond to codes reserved 469 by ISO 15924 for private use. These codes MAY be used for non- 470 registered script values. Please refer to Section 4.5 for more 471 information on private use subtags. 473 4. Script subtags MUST NOT be registered using the process in 474 Section 3.5 of this document. Variant subtags MAY be considered 475 for registration for that purpose. 477 5. There MUST be at most one script subtag in a language tag, and 478 the script subtag SHOULD be omitted when it adds no 479 distinguishing value to the tag or when the primary language 480 subtag's record includes a Suppress-Script field listing the 481 applicable script subtag. 483 Example: "sr-Latn" represents Serbian written using the Latin script. 485 2.2.4. Region Subtag 487 Region subtags are used to indicate linguistic variations associated 488 with or appropriate to a specific country, territory, or region. 489 Typically, a region subtag is used to indicate regional dialects or 490 usage, or region-specific spelling conventions. A region subtag can 491 also be used to indicate that content is expressed in a way that is 492 appropriate for use throughout a region, for instance, Spanish 493 content tailored to be useful throughout Latin America. 495 The following rules apply to the region subtags: 497 1. Region subtags MUST follow any language or script subtags and 498 MUST precede any other type of subtag. 500 2. All two-character subtags following the primary subtag were 501 defined in the IANA registry according to the assignments found 502 in [ISO3166-1] ("Codes for the representation of names of 503 countries and their subdivisions -- Part 1: Country codes") using 504 the list of alpha-2 country codes, or using assignments 505 subsequently made by the ISO 3166-1 maintenance agency or 506 governing standardization bodies. In addition, the codes that 507 are "exceptionally reserved" (as opposed to "assigned") in ISO 508 3166-1 were also defined in the registry, with the exception of 509 'UK', which is an exact synonym for the assigned code 'GB'. 511 3. All three-character subtags consisting of digit (numeric) 512 characters following the primary subtag were defined in the IANA 513 registry according to the assignments found in UN Standard 514 Country or Area Codes for Statistical Use [UN_M.49] or 515 assignments subsequently made by the governing standards body. 516 Note that not all of the UN M.49 codes are defined in the IANA 517 registry. The following rules define which codes are entered 518 into the registry as valid subtags: 520 A. UN numeric codes assigned to 'macro-geographical 521 (continental)' or sub-regions MUST be registered in the 522 registry. These codes are not associated with an assigned 523 ISO 3166-1 alpha-2 code and represent supra-national areas, 524 usually covering more than one nation, state, province, or 525 territory. 527 B. UN numeric codes for 'economic groupings' or 'other 528 groupings' MUST NOT be registered in the IANA registry and 529 MUST NOT be used to form language tags. 531 C. UN numeric codes for countries or areas which are assigned 532 ISO 3166-1 alpha2 codes already present in the registry, MUST 533 be defined according to the rules in Section 3.4 and MUST be 534 used to form language tags that represent the country or 535 region for which they are defined. This happens when ISO 536 3166-1 reassigns a code already included in the registry and 537 formerly used for one country to another. 539 D. UN numeric codes for countries or areas for which there is an 540 associated ISO 3166-1 alpha-2 code in the registry MUST NOT 541 be entered into the registry and MUST NOT be used to form 542 language tags. Note that the ISO 3166-based subtag in the 543 registry MUST actually be associated with the UN M.49 code in 544 question. 546 E. UN numeric codes and ISO 3166-1 alpha-2 codes for countries 547 or areas listed as eligible for registration in [RFC4645] but 548 not presently registered MAY be entered into the IANA 549 registry via the process described in Section 3.5. Once 550 registered, these codes MAY be used to form language tags. 552 F. All other UN numeric codes for countries or areas that do not 553 have an associated ISO 3166-1 alpha-2 code MUST NOT be 554 entered into the registry and MUST NOT be used to form 555 language tags. For more information about these codes, see 556 Section 3.4. 558 4. Note: The alphanumeric codes in Appendix X of the UN document 559 MUST NOT be entered into the registry and MUST NOT be used to 560 form language tags. (At the time this document was created, 561 these values matched the ISO 3166-1 alpha-2 codes.) 563 5. There MUST be at most one region subtag in a language tag and the 564 region subtag MAY be omitted, as when it adds no distinguishing 565 value to the tag. 567 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 568 reserved for private use in language tags. These subtags 569 correspond to codes reserved by ISO 3166 for private use. These 570 codes MAY be used for private use region subtags (instead of 571 using a private use subtag sequence). Please refer to 572 Section 4.5 for more information on private use subtags. 574 "de-AT" represents German ('de') as used in Austria ('AT'). 576 "sr-Latn-RS" represents Serbian ('sr') written using Latin script 577 ('Latn') as used in Serbia ('RS'). 579 "es-419" represents Spanish ('es') appropriate to the UN-defined 580 Latin America and Caribbean region ('419'). 582 2.2.5. Variant Subtags 584 Variant subtags are used to indicate additional, well-recognized 585 variations that define a language or its dialects that are not 586 covered by other available subtags. The following rules apply to the 587 variant subtags: 589 1. Variant subtags MUST follow any language, script, or region 590 subtags, but MUST precede any extension or private use subtag 591 sequences. 593 2. Variant subtags, as a collection, are not associated with any 594 particular external standard. The meaning of variant subtags in 595 the registry is defined in the course of the registration process 596 defined in Section 3.5. Note that any particular variant subtag 597 might be associated with some external standard. However, 598 association with a standard is not required for registration. 600 3. More than one variant MAY be used to form the language tag. 602 4. Variant subtags MUST be registered with IANA according to the 603 rules in Section 3.5 of this document before being used to form 604 language tags. In order to distinguish variants from other types 605 of subtags, registrations MUST meet the following length and 606 content restrictions: 608 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 609 at least five characters long. 611 2. Variant subtags that begin with a digit (0-9) MUST be at 612 least four characters long. 614 5. The same variant subtag MUST NOT be used more than once within a 615 language tag. 617 * For example, the tag "de-DE-1901-1901" is not valid. 619 Variant subtag records in the language subtag registry MAY include 620 one or more 'Prefix' fields. The 'Prefix' indicates the language tag 621 or tags that would make a suitable prefix (with other subtags, as 622 appropriate) in forming a language tag with the variant. That is, 623 each of the subtags in the prefix SHOULD appear, in order, before the 624 variant. For example, the subtag 'nedis' has a Prefix of "sl", 625 making it suitable for forming language tags such as "sl-nedis" and 626 "sl-IT-nedis", but not suitable for use in a tag such as "zh-nedis" 627 or "it-IT-nedis". 629 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 631 "de-CH-1996" represents German as used in Switzerland and as written 632 using the spelling reform beginning in the year 1996 C.E. 634 Most variants that share a prefix are mutually exclusive. For 635 example, the German orthographic variations '1996' and '1901' SHOULD 636 NOT be used in the same tag, as they represent the dates of different 637 spelling reforms. A variant that can meaningfully be used in 638 combination with another variant SHOULD include a 'Prefix' field in 639 its registry record that lists that other variant. For example, if 640 another German variant 'example' were created that made sense to use 641 with '1996', then 'example' should include two Prefix fields: "de" 642 and "de-1996". 644 2.2.6. Extension Subtags 646 Extensions provide a mechanism for extending language tags for use in 647 various applications. They are intended to identify information 648 which is commonly used in association with languages or language 649 tags, but which is not part of language identification. See 650 Section 3.7. The following rules apply to extensions: 652 1. An extension MUST follow at least a primary language subtag. 653 That is, a language tag cannot begin with an extension. 654 Extensions extend language tags, they do not override or replace 655 them. For example, "a-value" is not a well-formed language tag, 656 while "de-a-value" is. 658 2. Extension subtags are separated from the other subtags defined 659 in this document by a single-character subtag ("singleton"). 660 The singleton MUST be one allocated to a registration authority 661 via the mechanism described in Section 3.7 and MUST NOT be the 662 letter 'x', which is reserved for private use subtag sequences. 664 3. Note: Private use subtag sequences starting with the singleton 665 subtag 'x' are described in Section 2.2.7 below. 667 4. Each singleton subtag MUST appear at most one time in each tag 668 (other than as a private use subtag). That is, singleton 669 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 670 ccc" is invalid because the subtag 'a' appears twice. Note that 671 the tag "en-a-bbb-x-a-ccc" is valid because the second 672 appearance of the singleton 'a' is in a private use sequence. 674 5. Extension subtags MUST meet all of the requirements for the 675 content and format of subtags defined in this document. 677 6. Extension subtags MUST meet whatever requirements are set by the 678 document that defines their singleton prefix and whatever 679 requirements are provided by the maintaining authority. 681 7. Each extension subtag MUST be from two to eight characters long 682 and consist solely of letters or digits, with each subtag 683 separated by a single '-'. 685 8. Each singleton MUST be followed by at least one extension 686 subtag. For example, the tag "tlh-a-b-foo" is invalid because 687 the first singleton 'a' is followed immediately by another 688 singleton 'b'. 690 9. Extension subtags MUST follow all language, script, region, and 691 variant subtags in a tag. 693 10. All subtags following the singleton and before another singleton 694 are part of the extension. Example: In the tag "fr-a-Latn", the 695 subtag 'Latn' does not represent the script subtag 'Latn' 696 defined in the IANA Language Subtag Registry. Its meaning is 697 defined by the extension 'a'. 699 11. In the event that more than one extension appears in a single 700 tag, the tag SHOULD be canonicalized as described in 701 Section 4.4. 703 For example, if the prefix singleton 'r' and the shown subtags were 704 defined, then the following tag would be a valid example: "en-Latn- 705 GB-boont-r-extended-sequence-x-private" 707 2.2.7. Private Use Subtags 709 Private use subtags are used to indicate distinctions in language 710 important in a given context by private agreement. The following 711 rules apply to private use subtags: 713 1. Private use subtags are separated from the other subtags defined 714 in this document by the reserved single-character subtag 'x'. 716 2. Private use subtags MUST conform to the format and content 717 constraints defined in the ABNF for all subtags. 719 3. Private use subtags MUST follow all language, script, region, 720 variant, and extension subtags in the tag. Another way of saying 721 this is that all subtags following the singleton 'x' MUST be 722 considered private use. Example: The subtag 'US' in the tag "en- 723 x-US" is a private use subtag. 725 4. A tag MAY consist entirely of private use subtags. 727 5. No source is defined for private use subtags. Use of private use 728 subtags is by private agreement only. 730 6. Private use subtags are NOT RECOMMENDED where alternatives exist 731 or for general interchange. See Section 4.5 for more information 732 on private use subtag choice. 734 For example: The Unicode Consortium defines a set of private use 735 extensions in LDML ([UTS35], Locale Data Markup Language, the Unicode 736 standard for defining locale data) such as in the tag "es-419-x-ldml- 737 collation-traditio", which indicates Latin American Spanish with 738 traditional order for sorted lists. 740 2.2.8. Grandfathered Registrations 742 Prior to RFC 4646, whole language tags were registered according to 743 the rules in RFC 1766 and/or RFC 3066. These registered tags 744 maintain their validity. Of those tags, those that were made 745 obsolete or redundant by the advent of RFC 4646, by this document, or 746 by subsequent registration of subtags are maintained in the registry 747 in records as "redundant" records. Those tags that do not match the 748 'langtag' production in the ABNF in this document or that contain 749 subtags that do not individually appear in the registry are 750 maintained in the registry in records of the "grandfathered" type. 752 Grandfathered tags contain one or more subtags that are not defined 753 in the Language Subtag Registry (see Section 3). Redundant tags 754 consist entirely of subtags defined above and whose independent 755 registration was superseded by [RFC4646]. For more information see 756 Section 3.8. 758 Some grandfathered tags are "regular" in that they match the 759 'langtag' production in Figure 1. In some cases, these tags could 760 become redundant if their (currently unregistered) subtags were to be 761 registered (as variants, for example). In other cases, although the 762 subtags match the language tag pattern, the meaning assigned to the 763 various subtags is prohibited by rules elsewhere in this document. 764 Those tags can never become redundant. 766 The remaining grandfathered tags are "irregular" and do not match the 767 'langtag' production. These are listed in the 'irregular' production 768 in Figure 1. These grandfathered tags can never become redundant. 769 Many of these tags have been superseded by other registrations: their 770 record contains a Preferred-Value field that really ought to be used 771 to form language tags representing that value. 773 2.2.9. Classes of Conformance 775 Implementations sometimes need to describe their capabilities with 776 regard to the rules and practices described in this document. Tags 777 can be checked or verified in a number of ways, but two particular 778 classes of tag conformance are formally defined here. 780 A tag is considered "well-formed" if it conforms to the ABNF 781 (Section 2.1). Note that irregular grandfathered tags are now listed 782 in the 'irregular' production. 784 A tag is considered "valid" if it satisfies these conditions: 786 o The tag is well-formed. 788 o The tag is either a grandfathered tag, or all of its language, 789 script, region, and variant subtags appear in the IANA language 790 subtag registry as of the particular registry date. 792 o There are no duplicate singleton (extension) subtags and no 793 duplicate variant subtags. 795 Note that a tag's validity depends on the date of the registry used 796 to validate the tag. A more recent copy of the registry might 797 contain a subtag that an older version does not. 799 A tag is considered "valid" for a given extension (Section 3.7) (as 800 of a particular version, revision, and date) if it meets the criteria 801 for "valid" above and also satisfies this condition: 803 Each subtag used in the extension part of the tag is valid 804 according to the extension. 806 Some older implementations consider a tag "well-formed" if it matches 807 the ABNF in [RFC4646]. In that version, a well-formed tag could 808 contain a sequence matching the obsolete 'extlang' production. Other 809 than a few grandfathered tags (which are handled separately), no 810 valid tags have ever matched that pattern. The difference between 811 that ABNF and Figure 1 is that the language production is replaced as 812 follows: 814 obs-primary-language = (2*3ALPHA [ extlang ]) ; shortest ISO 639 code 815 / 4ALPHA ; reserved for future use 816 / 5*8ALPHA ; registered language subtag 818 extlang = *3("-" 3ALPHA) ; removed in this version 820 Figure 2: Obsolete Language ABNF 822 Older language tag implementations sometimes reference [RFC3066]. 823 Again, all valid tags under that version also match this document's 824 language tag ABNF. However, a wider array of tags could be 825 considered "well-formed" under that document. The 'Language-Tag' 826 production used in that document matches the following: 828 obs-language-tag = primary-subtag *( "-" subtag ) 829 primary-subtag = 1*8ALPHA 830 subtag = 1*8(ALPHA / DIGIT) 832 Figure 3: RFC 3066 Language Tag Syntax 834 Language tags may be well-formed in terms of syntax but not valid in 835 terms of content. Users MUST NOT assign and use their own subtags, 836 other than private-use sequences (such as "en-x-personal") or by 837 using subtags designated as private-use in the registry (such as 838 "no-QQ", where 'QQ' is one of a range of private-use ISO 3166-1 839 codes). Not only is such assignment nonconformant, it also risks 840 collision with a future possible assignment. The private use subtags 841 and sequences are designed for this case. 843 3. Registry Format and Maintenance 845 This section defines the Language Subtag Registry and the maintenance 846 and update procedures associated with it, as well as a registry for 847 extensions to language tags (Section 3.7). 849 The Language Subtag Registry contains a comprehensive list of all of 850 the subtags valid in language tags. This allows implementers a 851 straightforward and reliable way to validate language tags. The 852 Language Subtag Registry will be maintained so that, except for 853 extension subtags, it is possible to validate all of the subtags that 854 appear in a language tag under the provisions of this document or its 855 revisions or successors. In addition, the meaning of the various 856 subtags will be unambiguous and stable over time. (The meaning of 857 private use subtags, of course, is not defined by the IANA registry.) 859 3.1. Format of the IANA Language Subtag Registry 861 The IANA Language Subtag Registry ("the registry") is a machine- 862 readable file in the format described in this section, plus copies of 863 the registration forms approved in accordance with the process 864 described in Section 3.5. 866 Note: The existing registration forms for grandfathered and redundant 867 tags taken from RFC 3066 have been maintained as part of the obsolete 868 RFC 3066 registry. The subtags added to the registry by either 869 [RFC4645] or [registry-update] do not have separate registration 870 forms (so no forms are archived for these additions). 872 3.1.1. File Format 874 The registry consists of a series of records stored in the record-jar 875 format (described in [record-jar]). Each record, in turn, consists 876 of a series of fields that describe the various subtags and tags. 877 The registry is a Unicode [Unicode] text file, using the UTF-8 878 [RFC3629] character encoding. 880 Each field can be considered a single, logical line of Unicode 881 [Unicode] characters, comprising a field-name and a field-body 882 separated by a COLON character (%x3A). Each field is terminated by 883 the newline sequence CRLF. The text in each field MUST be in Unicode 884 Normalization Form C (NFC). 886 A collection of fields forms a 'record'. Records are separated by 887 lines containing only the sequence "%%" (%x25.25). 889 Although fields are logically a single line of text, each line of 890 text in the file format is limited to 72 bytes in length. To 891 accommodate this, the field-body can be split into a multiple-line 892 representation; this is called "folding". Folding is done according 893 to customary conventions for line-wrapping. This is typically on 894 whitespace boundaries, but can occur between other characters when 895 the value does not include spaces, such as when a language does not 896 use whitespace between words. In any event, there MUST NOT be breaks 897 inside a multibyte UTF-8 sequence nor in the middle of a combining 898 character sequence. For more information, see [UAX14]. 900 Although the file format uses the UTF-8 encoding, unless otherwise 901 indicated, fields are restricted to the printable characters from the 902 US-ASCII [ISO646] repertoire. 904 The format of the registry is described by the following ABNF (per 905 [RFC5234]): 907 registry = record *("%%" CRLF record) 908 record = 1*( field-name *SP ":" *SP field-body CRLF ) 909 field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] 910 field-body = *([[*SP CRLF] 1*SP] 1*CHARS) 911 CHARS = (%x21-10FFFF) ; Unicode code points 913 Figure 4: Registry Format ABNF 915 The sequence '..' (%x2E.2E) in a field-body denotes a range of 916 values. Such a range represents all subtags of the same length that 917 are in alphabetic or numeric order within that range, including the 918 values explicitly mentioned. For example 'a..c' denotes the values 919 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 920 '13'. 922 All fields whose field-body contains a date value use the "full-date" 923 format specified in [RFC3339]. For example: "2004-06-28" represents 924 June 28, 2004, in the Gregorian calendar. 926 3.1.2. Record Definitions 928 There are three types of records in the registry: "File-Date", 929 "Subtag", and "Tag" records. 931 The first record in the registry is a "File-Date" record. This 932 record contains the single field whose field-name is "File-Date" (see 933 Figure 4). The field-body of this record contains the last 934 modification date of this copy of the registry, making it possible to 935 compare different versions of the registry. The registry on the IANA 936 website is the most current. Versions with an older date than that 937 one are not up-to-date. 939 File-Date: 2004-06-28 940 %% 942 Figure 5: Example of the File-Date Record 944 Subsequent records represent either subtags or tags in the registry. 945 "Subtag" records contain a field with a field-name of "Subtag", 946 while, unsurprisingly, "Tag" records contain a field with a field- 947 name of "Tag". Each of the fields in each record MUST occur no more 948 than once, unless otherwise noted below. Each record MUST contain 949 the following fields: 951 o 'Type' 953 * Type's field-body MUST consist of one of the following strings: 954 "language", "script", "region", "variant", "grandfathered", and 955 "redundant" and denotes the type of tag or subtag. 957 o Either 'Subtag' or 'Tag' 959 * Subtag's field-body contains the subtag being defined. This 960 field MUST only appear in records of whose 'Type' has one of 961 these values: "language", "script", "region", or "variant". 963 * Tag's field-body contains a complete language tag. This field 964 MUST only appear in records whose 'Type' has one of these 965 values: "grandfathered" or "redundant". Note that the field- 966 body will always follow the 'grandfathered' production in the 967 ABNF in Section 2.1 969 o Description 971 * Description's field-body contains a non-normative description 972 of the subtag or tag. 974 o Added 976 * Added's field-body contains the date the record was added to 977 the registry. 979 Each record MAY also contain the following fields: 981 o Preferred-Value 983 * For fields of type 'script', 'region', and 'variant', 984 'Preferred-Value' contains the subtag of the same 'Type' that 985 is preferred for forming the language tag. 987 * For fields of type 'language', 'Preferred-Value' contains the 988 primary language subtag that is preferred when forming the 989 language tag. 991 * For fields of type 'grandfathered' and 'redundant', 'Preferred- 992 Value' contains a canonical mapping to a complete language tag. 994 o Deprecated 996 * The field-body of the Deprecated field contains the date the 997 record was deprecated. 999 o Prefix 1001 * Prefix's field-body contains a language tag with which this 1002 subtag MAY be used to form a new language tag, perhaps with 1003 other subtags as well. The Prefix's subtags appear before the 1004 subtag. This field MUST only appear in records whose 'Type' 1005 field-body is 'variant'. For example, the 'Prefix' for the 1006 variant 'nedis' is 'sl', meaning that the tags "sl-nedis" and 1007 "sl-IT-nedis" are appropriate while the tag "is-nedis" is not. 1009 o Comments 1011 * Comments contains additional information about the subtag, as 1012 deemed appropriate for understanding the registry and 1013 implementing language tags using the subtag or tag. 1015 o Suppress-Script 1017 * Suppress-Script contains a script subtag that SHOULD NOT be 1018 used to form language tags with the associated primary language 1019 subtag. This field MUST only appear in records whose 'Type' 1020 field-body is 'language'. See Section 4.1. 1022 o Macrolanguage 1024 * Macrolanguage contains a primary language subtag defined by ISO 1025 639 as a "macrolanguage" that encompasses this language subtag. 1026 This field MUST only appear in records whose 'Type' field-body 1027 is 'language'. 1029 Future versions of this document might add additional fields to the 1030 registry, so implementations SHOULD ignore fields found in the 1031 registry that are not defined in this document. 1033 3.1.3. Subtag and Tag Fields 1035 The 'Subtag' field MUST NOT use uppercase letters to form the subtag, 1036 with two exceptions. Subtags whose 'Type' field is 'script' (in 1037 other words, subtags defined by ISO 15924) MUST use titlecase. 1038 Subtags whose 'Type' field is 'region' (in other words, the non- 1039 numeric region subtags defined by ISO 3166-1) MUST use all uppercase. 1040 These exceptions mirror the use of case in the underlying standards. 1042 Each subtag in the tags contained in a 'Tag' field MUST be formatted 1043 using the rules in the preceding paragraph. That is, all subtags are 1044 lowercase except for subtags that represent script or region codes. 1046 3.1.4. Description Field 1048 The field 'Description' contains a description of the tag or subtag 1049 in the record. The 'Description' field MAY appear more than once per 1050 record, that is, there can be multiple descriptions for a given 1051 record. The 'Description' field MAY include the full range of 1052 Unicode characters. At least one of the 'Description' fields MUST be 1053 written or transcribed into the Latin script; additional 1054 'Description' fields MAY also include a description in a non-Latin 1055 script. Each 'Description' field MUST be unique, both within the 1056 record in which it appears and for the collection of records of the 1057 same type. Moreover, formatting variations of the same description 1058 MUST NOT occur in that specific record or in any other record of the 1059 same type. For example, while the ISO 639-1 code 'fy' contains both 1060 the descriptions "Western Frisian" and "Frisian, Western", only one 1061 of these descriptions appears in the registry. 1063 The 'Description' field is used for identification purposes. It 1064 doesn't necessarily represent the actual native name of the item in 1065 the record, nor are any of the descriptions guaranteed to be in any 1066 particular language (such as English or French, for example). 1068 For subtags taken from a source standard (such as ISO 639 or ISO 1069 15924), the 'Description' value(s) SHOULD also be taken from the 1070 source standard. Multiple descriptions in the source standard MUST 1071 be split into separate 'Description' fields. The source standard's 1072 descriptions MAY be edited, either prior to insertion or via the 1073 registration process. For fields of type 'language', the first 1074 'Description' field appearing in the Registry corresponds to the 1075 Reference Name assigned by ISO 639-3. This helps facilitate cross- 1076 referencing between ISO 639 and the registry. 1078 When creating or updating a record due to the action of one of the 1079 source standards, the Language Subtag Reviewer SHOULD remove 1080 duplicate or redundant descriptions and MAY edit descriptions to 1081 correct irregularities in formatting (such as misspellings, 1082 inappropriate apostrophes or other punctuation, or excessive or 1083 missing spaces) prior to submitting the proposed record to the ietf- 1084 languages list. 1086 Note: Descriptions in registry entries that correspond to ISO 639, 1087 ISO 15924, ISO 3166-1, or UN M.49 codes are intended only to indicate 1088 the meaning of that identifier as defined in the source standard at 1089 the time it was added to the registry. The description does not 1090 replace the content of the source standard itself. The descriptions 1091 are not intended to be the localized English names for the subtags. 1092 Localization or translation of language tag and subtag descriptions 1093 is out of scope of this document. 1095 Descriptions SHOULD contain all and only that information necessary 1096 to distinguish one subtag from others that it might be confused with. 1097 They are not intended to provide general background information, nor 1098 to provide all possible alternate names or designations. 1100 3.1.5. Deprecated Field 1102 The field 'Deprecated' MAY be added, changed, or removed from any 1103 record via the maintenance process described in Section 3.3 or via 1104 the registration process described in Section 3.5. Usually, the 1105 addition of a 'Deprecated' field is due to the action of one of the 1106 standards bodies, such as ISO 3166, withdrawing a code. In some 1107 historical cases, it might not have been possible to reconstruct the 1108 original deprecation date. For these cases, an approximate date 1109 appears in the registry. Although valid in language tags, subtags 1110 and tags with a 'Deprecated' field are deprecated and validating 1111 processors SHOULD NOT generate these subtags. Note that a record 1112 that contains a 'Deprecated' field and no corresponding 'Preferred- 1113 Value' field has no replacement mapping. 1115 3.1.6. Preferred-Value Field 1117 The field 'Preferred-Value' contains a mapping between the record in 1118 which it appears and another tag or subtag. The value in this field 1119 is strongly RECOMMENDED as the best choice to represent the value of 1120 this record when selecting a language tag. These values form three 1121 groups: 1123 1. ISO 639 language codes that were later withdrawn in favor of 1124 other codes. These values are mostly a historical curiosity. 1126 2. Codes that have been withdrawn in favor of a new code. In 1127 particular, this applies to region subtags taken from ISO 3166-1, 1128 because sometimes a country will change its name or 1129 administration in such a way that warrants a new region code. In 1130 some cases, countries have reverted to an older name, which might 1131 already be encoded. 1133 3. Tags or subtags that have become obsolete because the values they 1134 represent were later encoded. Many of the grandfathered or 1135 redundant tags were later encoded by ISO 639, for example, and 1136 fit this pattern. 1138 Records that contain a 'Preferred-Value' field MUST also have a 1139 'Deprecated' field. This field contains the date on which the tag or 1140 subtag was deprecated in favor of the preferred value. 1142 Note that 'Preferred-Value' mappings in records of type 'region' 1143 sometimes do not represent exactly the same meaning as the original 1144 value. There are many reasons for a country code to be changed, and 1145 the effect this has on the formation of language tags will depend on 1146 the nature of the change in question. 1148 The field MAY be added, changed, or removed from records according to 1149 the rules in Section 3.3. Addition, modification, or removal of a 1150 'Preferred-Value' field in a record does not imply that content using 1151 the affected subtag needs to be retagged. 1153 The 'Preferred-Value' field in records of type "grandfathered" and 1154 "redundant" contains whole language tags that are strongly 1155 RECOMMENDED for use in place of the record's value. In many cases, 1156 these mappings were created via deprecation of the tags during the 1157 period before [RFC4646] was adopted. For example, the tag "no-nyn" 1158 was deprecated in favor of the ISO 639-1-defined language code 'nn'. 1160 Usually the addition, removal, or change of a Preferred-Value field 1161 for a subtag is done to reflect changes in one of the source 1162 standards. For example, if an ISO 3166-1 region code is deprecated 1163 in favor of another code, that SHOULD result in the addition of a 1164 Preferred-Value field. 1166 Changes to one subtag MAY affect other subtags as well: when 1167 proposing changes to the registry, the Language Subtag Reviewer will 1168 review the registry for such effects and propose the necessary 1169 changes using the process in Section 3.5, although anyone MAY request 1170 such changes. For example: 1172 Suppose that subtag 'XX' has a Preferred-Value of 'YY'. If 'YY' 1173 later changes to have a Preferred-Value of 'ZZ', then the 1174 Preferred-Value for 'XX' MUST also change to be 'ZZ'. 1176 Suppose that a variant subtag 'dialect' represents a language not 1177 yet available in any part of ISO 639. The later addition of a 1178 corresponding language code in ISO 639 SHOULD result in the 1179 addition of a Preferred-Value for 'dialect'. 1181 3.1.7. Prefix Field 1183 The 'Prefix' field contains an extended language range whose subtags 1184 are appropriate to use with this subtag: each of the subtags in one 1185 of the subtag's Prefix fields SHOULD appear before the variant in a 1186 valid tag. For example, the variant subtag '1996' has a 'Prefix' 1187 field of "de". This means that tags starting with the sequence "de-" 1188 are appropriate with this subtag, so "de-Latg-1996" and "de-CH-1996" 1189 are both acceptable, while the tag "fr-1996" is an inappropriate 1190 choice. 1192 The field of type 'Prefix' MUST NOT be removed from any record. The 1193 field-body for this type of field MAY be modified, but only if the 1194 modification broadens the meaning of the subtag. That is, the field- 1195 body can be replaced only by a prefix of itself. For example, the 1196 Prefix "be-Latn" (Belarusian, Latin script) could be replaced by the 1197 Prefix "be" (Belarusian) but not by the Prefix "ru-Latn" (Russian, 1198 Latin script). 1200 Records of type 'variant' MAY have more than one field of type 1201 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1202 record via the registration process. 1204 The field-body of the 'Prefix' field MUST NOT conflict with any 1205 'Prefix' already registered for a given record. Such a conflict 1206 would occur when no valid tag could be constructed that would contain 1207 the prefix, such as when two subtags each have a 'Prefix' that 1208 contains the other subtag. For example, suppose that the subtag 1209 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' 1210 cannot given the prefix 'avariant', for that would require a tag of 1211 the form "es-avariant-bvariant-avariant", which would not be valid. 1213 3.1.8. Suppress-Script Field 1215 The field 'Suppress-Script' contains a script subtag (whose record 1216 appears in the registry). The field 'Suppress-Script' MUST only 1217 appear in records whose 'Type' field-body is 'language'. This field 1218 MUST NOT appear more than one time in a record. This field indicates 1219 a script used to write the overwhelming majority of documents for the 1220 given language. This script code therefore adds no distinguishing 1221 information to a language tag. This helps ensure greater 1222 compatibility between the language tags generated according to the 1223 rules in this document and language tags and tag processors or 1224 consumers based on RFC 3066 by indicating that the script subtag 1225 SHOULD NOT be used for most documents in that language. For example, 1226 virtually all Icelandic documents are written in the Latin script, 1227 making the subtag 'Latn' redundant in the tag "is-Latn". 1229 Many language subtag records do not have a Suppress-Script field. 1230 The lack of a Suppress-Script might indicate that the language is 1231 customarily written in more than one script or that the language is 1232 not customarily written at all. It might also mean that sufficient 1233 information was not available when the record was created and thus 1234 remains a candidate for future registration. 1236 3.1.9. Macrolanguage Field 1238 The Macrolanguage field contains a primary language subtag that 1239 encompasses this subtag's language. That is, the language subtag 1240 whose record this field appears in is sometimes considered to be a 1241 sub-language of the Macrolanguage. Macrolanguage values are defined 1242 by ISO 639-3 and the exact nature of the relationship between the 1243 encompassed and encompassing languages varies on a case-by-case 1244 basis. 1246 This field can be useful to applications or users when selecting 1247 language tags or as additional metadata useful in matching. The 1248 Macrolanguage field can only occur in records of type 'language'. 1249 Only values assigned by ISO 639-3 will be considered for inclusion. 1250 Macrolanguage fields MAY be added or removed via the normal 1251 registration process whenever ISO 639-3 defines new values or 1252 withdraws old values. Macrolanguages are informational, and MAY be 1253 removed or changed if ISO 639-3 changes the values. 1255 For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' 1256 (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' 1257 (Norwegian). For more information see Section 4.1. 1259 3.1.10. Comments Field 1261 The field 'Comments' conveys additional information about the record 1262 and MAY appear more than once per record. The field-body MAY include 1263 the full range of Unicode characters and is not restricted to any 1264 particular script. This field MAY be inserted or changed via the 1265 registration process and no guarantee of stability is provided. 1267 The content of this field is not restricted, except by the need to 1268 register the information, the suitability of the request, and by 1269 reasonable practical size limitations. The primary reason for the 1270 Comments field is subtag identification: to help distinguish the 1271 subtag from others with which it might be confused. In particular, 1272 large amounts of information about the use, history, or general 1273 background of a subtag are frowned upon as these generally belong and 1274 are encouraged in registration request forms themselves, but do not 1275 belong in the registry record proper. 1277 3.2. Language Subtag Reviewer 1279 The Language Subtag Reviewer moderates the ietf-languages mailing 1280 list, responds to requests for registration, and performs the other 1281 registry maintenance duties described in Section 3.3. Only the 1282 Language Subtag Reviewer is permitted to request IANA to change, 1283 update, or add records to the Language Subtag Registry. The Language 1284 Subtag Reviewer MAY delegate list moderation and other clerical 1285 duties as needed. 1287 The Language Subtag Reviewer is appointed by the IESG for an 1288 indefinite term, subject to removal or replacement at the IESG's 1289 discretion. The IESG will solicit nominees for the position (upon 1290 adoption of this document or upon a vacancy) and then solicit 1291 feedback on the nominees' qualifications. Qualified candidates 1292 should be familiar with BCP 47 and its requirements; be willing to 1293 fairly, responsively, and judiciously administer the registration 1294 process; and be suitably informed about the issues of language 1295 identification so that the reviewer can assess the claims and draw 1296 upon the contributions of language experts and subtag requesters. 1298 The subsequent performance or decisions of the Language Subtag 1299 Reviewer MAY be appealed to the IESG under the same rules as other 1300 IETF decisions (see [RFC2026]). The IESG can reverse or overturn the 1301 decisions of the Language Subtag Reviewer, provide guidance, or take 1302 other appropriate actions. 1304 3.3. Maintenance of the Registry 1306 Maintenance of the registry requires that as codes are assigned or 1307 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1308 Subtag Reviewer MUST evaluate each change and determine the 1309 appropriate course of action according to the rules in this document. 1310 Such updates follow the registration process described in 1311 Section 3.5. Usually the Language Subtag Reviewer will start the 1312 process for the new or updated record by filling in the registration 1313 form and submitting it. If a change to one of these standards takes 1314 place and the Language Subtag Reviewer does not do this in a timely 1315 manner, then any interested party MAY submit the form. Thereafter 1316 the registration process continues normally. 1318 Note that some registrations affect other subtags--perhaps more than 1319 one--as when a region subtag is being deprecated in favor of a new 1320 value. The Language Subtag Reviewer is responsible for ensuring that 1321 any such changes are properly registered, with each change requiring 1322 its own registration form. 1324 The Language Subtag Reviewer MUST ensure that new subtags meet the 1325 requirements elsewhere in this document (and most especially in 1326 Section 3.4) or submit an appropriate registration form for an 1327 alternate subtag as described in that section. Each individual 1328 subtag affected by a change MUST be sent to the ietf-languages list 1329 with its own registration form and in a separate message. 1331 3.4. Stability of IANA Registry Entries 1333 The stability of entries and their meaning in the registry is 1334 critical to the long-term stability of language tags. The rules in 1335 this section guarantee that a specific language tag's meaning is 1336 stable over time and will not change. 1338 These rules specifically deal with how changes to codes (including 1339 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1340 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1341 Subtag Registry. Assignments to the IANA Language Subtag Registry 1342 MUST follow the following stability rules: 1344 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST 1345 NOT be changed and are guaranteed to be stable over time. 1347 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be 1348 added, altered, or removed via the registration process. These 1349 changes SHOULD be limited to changes necessary to mirror changes 1350 in one of the underlying standards (ISO 639, ISO 15924, ISO 1351 3166-1, or UN M.49) and typically alteration or removal of a 1352 Preferred-Value is limited specifically to region codes. 1354 3. Values in the 'Description' field MUST NOT be changed in a way 1355 that would invalidate previously-existing tags. They MAY be 1356 broadened somewhat in scope, changed to add information, or 1357 adapted to the most common modern usage. For example, countries 1358 occasionally change their names; a historical example of this 1359 would be "Upper Volta" changing to "Burkina Faso". 1361 4. Values in the field 'Prefix' MAY be added to records of type 1362 'variant' via the registration process. If a prefix is added to 1363 a variant record, 'Comment' fields SHOULD be used to explain 1364 different usages with the various prefixes. 1366 5. Values in the field 'Prefix' in records of type 'variant' MAY be 1367 modified, so long as the modifications broaden the set of 1368 prefixes. That is, a prefix MAY be replaced by one of its own 1369 prefixes. For example, the prefix "en-US" could be replaced by 1370 "en", but not by the prefixes "en-Latn", "fr", or "en-US-boont". 1371 If one of those prefixes were needed, a new Prefix SHOULD be 1372 registered. 1374 6. Values in the field 'Prefix' MUST NOT be removed. 1376 7. The field 'Comments' MAY be added, changed, modified, or removed 1377 via the registration process or any of the processes or 1378 considerations described in this section. 1380 8. The field 'Suppress-Script' MAY be added or removed via the 1381 registration process. 1383 9. The field 'Macrolanguage' MAY be added or removed via the 1384 registration process, but only in response to changes made by 1385 ISO 639. The Macrolanguage field appears whenever a language 1386 has a corresponding Macrolanguage in ISO 639. That is, the 1387 macrolanguage fields in the registry exactly match those of ISO 1388 639. No other macrolanguage mappings will be considered for 1389 registration. 1391 10. Codes assigned by ISO 639-1 that do not conflict with existing 1392 two-letter primary language subtags and which have no 1393 corresponding three-letter primary defined in the registry are 1394 entered into the IANA registry as new records of type 1395 'language'. 1397 11. Codes assigned by ISO 639-2 that do not conflict with existing 1398 three-letter primary language subtags are entered into the IANA 1399 registry as new records of type 'language'. 1401 12. Codes assigned by ISO 639-3 that do not conflict with existing 1402 three-letter primary language subtags are entered into the IANA 1403 registry as new primary language records. 1405 13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict 1406 with existing subtags of the associated type and whose meaning 1407 is not the same as an existing subtag of the same type are 1408 entered into the IANA registry as new records. 1410 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are 1411 withdrawn by their respective maintenance or registration 1412 authority remain valid in language tags. A 'Deprecated' field 1413 containing the date of withdrawal MUST be added to the record. 1414 If a new record of the same type is added that represents a 1415 replacement value, then a 'Preferred-Value' field MAY also be 1416 added. The registration process MAY be used to add comments 1417 about the withdrawal of the code by the respective standard. 1419 Example The region code 'TL' was assigned to the country 1420 'Timor-Leste', replacing the code 'TP' (which was assigned to 1421 'East Timor' when it was under administration by Portugal). 1422 The subtag 'TP' remains valid in language tags, but its 1423 record contains the a 'Preferred-Value' of 'TL' and its field 1424 'Deprecated' contains the date the new code was assigned 1425 ('2004-07-06'). 1427 15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that 1428 conflict with existing subtags of the associated type, including 1429 subtags that are deprecated, MUST NOT be entered into the 1430 registry. The following additional considerations apply to 1431 subtag values that are reassigned: 1433 A. For ISO 639 codes, if the newly assigned code's meaning is 1434 not represented by a subtag in the IANA registry, the 1435 Language Subtag Reviewer, as described in Section 3.5, SHALL 1436 prepare a proposal for entering in the IANA registry as soon 1437 as practical a registered language subtag as an alternate 1438 value for the new code. The form of the registered language 1439 subtag will be at the discretion of the Language Subtag 1440 Reviewer and MUST conform to other restrictions on language 1441 subtags in this document. 1443 B. For all subtags whose meaning is derived from an external 1444 standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN 1445 M.49), if a new meaning is assigned to an existing code and 1446 the new meaning broadens the meaning of that code, then the 1447 meaning for the associated subtag MAY be changed to match. 1448 The meaning of a subtag MUST NOT be narrowed, however, as 1449 this can result in an unknown proportion of the existing 1450 uses of a subtag becoming invalid. Note: ISO 639 1451 maintenance agency/registration authority (MA/RA) has 1452 adopted a similar stability policy. 1454 C. For ISO 15924 codes, if the newly assigned code's meaning is 1455 not represented by a subtag in the IANA registry, the 1456 Language Subtag Reviewer, as described in Section 3.5, SHALL 1457 prepare a proposal for entering in the IANA registry as soon 1458 as practical a registered variant subtag as an alternate 1459 value for the new code. The form of the registered variant 1460 subtag will be at the discretion of the Language Subtag 1461 Reviewer and MUST conform to other restrictions on variant 1462 subtags in this document. 1464 D. For ISO 3166-1 codes, if the newly assigned code's meaning 1465 is associated with the same UN M.49 code as another 'region' 1466 subtag, then the existing region subtag remains as the 1467 preferred value for that region and no new entry is created. 1468 A comment MAY be added to the existing region subtag 1469 indicating the relationship to the new ISO 3166-1 code. 1471 E. For ISO 3166-1 codes, if the newly assigned code's meaning 1472 is associated with a UN M.49 code that is not represented by 1473 an existing region subtag, then the Language Subtag 1474 Reviewer, as described in Section 3.5, SHALL prepare a 1475 proposal for entering the appropriate UN M.49 country code 1476 as an entry in the IANA registry. 1478 F. For ISO 3166-1 codes, if there is no associated UN numeric 1479 code, then the Language Subtag Reviewer SHALL petition the 1480 UN to create one. If there is no response from the UN 1481 within ninety days of the request being sent, the Language 1482 Subtag Reviewer SHALL prepare a proposal for entering in the 1483 IANA registry as soon as practical a registered variant 1484 subtag as an alternate value for the new code. The form of 1485 the registered variant subtag will be at the discretion of 1486 the Language Subtag Reviewer and MUST conform to other 1487 restrictions on variant subtags in this document. This 1488 situation is very unlikely to ever occur. 1490 16. UN M.49 has codes for both countries and areas (such as '276' 1491 for Germany) and geographical regions and sub-regions (such as 1492 '150' for Europe). UN M.49 country or area codes for which 1493 there is no corresponding ISO 3166-1 code SHOULD NOT be 1494 registered, except as a surrogate for an ISO 3166-1 code that is 1495 blocked from registration by an existing subtag. If such a code 1496 becomes necessary, then the registration authority for ISO 1497 3166-1 SHOULD first be petitioned to assign a code to the 1498 region. If the petition for a code assignment by ISO 3166-1 is 1499 refused or not acted on in a timely manner, the registration 1500 process described in Section 3.5 MAY then be used to register 1501 the corresponding UN M.49 code. This way, UN M.49 codes remain 1502 available as the value of last resort in cases where ISO 3166-1 1503 reassigns a deprecated value in the registry. 1505 17. Stability provisions apply to grandfathered tags with this 1506 exception: should it become possible to compose one of the 1507 grandfathered tags from registered subtags, then the field 1508 'Type' in that record is changed from 'grandfathered' to 1509 'redundant'. Note that this will not affect language tags that 1510 match the grandfathered tag, since these tags will now match 1511 valid generative subtag sequences. For example, the variant 1512 subtag '1901' is registered, making the formerly-grandfathered 1513 tags such as "de-1901" and "de-AT-1901" redundant as a result. 1514 Of course, these tags, where applied to existing content or in 1515 existing implementations, remain valid (all of their subtags are 1516 in the registry, after all), while new tags or applications 1517 using these subtags become possible. 1519 Note: The redundant and grandfathered entries together are the 1520 complete list of tags registered under [RFC3066]. The redundant tags 1521 are those that can now be formed using the subtags defined in the 1522 registry together with the rules of Section 2.2. The grandfathered 1523 entries include those that can never be legal under those same 1524 provisions plus those tags that contain subtags not yet registered 1525 or, perhaps, inappropriate for registration. 1527 The set of redundant and grandfathered tags is permanent and stable: 1528 new entries in this section MUST NOT be added and existing entries 1529 MUST NOT be removed. Records of type 'grandfathered' MAY have their 1530 type converted to 'redundant'; see item 12 in Section 3.6 for more 1531 information. The decision-making process about which tags were 1532 initially grandfathered and which were made redundant is described in 1533 [RFC4645]. 1535 RFC 3066 tags that were deprecated prior to the adoption of [RFC4646] 1536 are part of the list of grandfathered tags, and their component 1537 subtags were not included as registered variants (although they 1538 remain eligible for registration). For example, the tag "art-lojban" 1539 was deprecated in favor of the language subtag 'jbo'. 1541 3.5. Registration Procedure for Subtags 1543 The procedure given here MUST be used by anyone who wants to use a 1544 subtag not currently in the IANA Language Subtag Registry. 1546 Only subtags of type 'language' and 'variant' will be considered for 1547 independent registration of new subtags. Subtags needed for 1548 stability and subtags necessary to keep the registry synchronized 1549 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1550 defined by this document also use this process, as described in 1551 Section 3.3. Stability provisions are described in Section 3.4. 1553 This procedure MAY also be used to register or alter the information 1554 for the 'Comments', 'Deprecated', 'Description', 'Prefix', 1555 'Preferred-Value', or 'Suppress-Script' fields in a subtag's record 1556 as described in Section 3.4. Changes to all other fields in the IANA 1557 registry are NOT permitted. 1559 Registering a new subtag or requesting modifications to an existing 1560 tag or subtag starts with the requester filling out the registration 1561 form reproduced below. Note that each response is not limited in 1562 size so that the request can adequately describe the registration. 1563 The fields in the "Record Requested" section SHOULD follow the 1564 requirements in Section 3.1. 1566 LANGUAGE SUBTAG REGISTRATION FORM 1567 1. Name of requester: 1568 2. E-mail address of requester: 1569 3. Record Requested: 1571 Type: 1572 Subtag: 1573 Description: 1574 Prefix: 1575 Preferred-Value: 1576 Deprecated: 1577 Suppress-Script: 1578 Macrolanguage: 1579 Comments: 1581 4. Intended meaning of the subtag: 1582 5. Reference to published description 1583 of the language (book or article): 1584 6. Any other relevant information: 1586 Figure 6: The Language Subtag Registration Form 1588 Examples of completed registration forms can be found in Appendix C 1589 or online at http://www.iana.org/assignments/lang-subtags-templates/. 1591 The subtag registration form MUST be sent to 1592 for a two-week review period before it can 1593 be submitted to IANA. If modifications are made to the request 1594 during the course of the registration process (such as corrections to 1595 meet the requirements in Section 3.1) the modified form MUST also be 1596 sent to at least one week prior to 1597 submission to IANA. 1599 The ietf-languages list is an open list and can be joined by sending 1600 a request to . The list can be 1601 hosted by IANA or by any third party at the request of IESG. 1603 Before forwarding a new registration to IANA, the Language Subtag 1604 Reviewer MUST ensure that all requirements in this document are met 1605 and that values in the 'Subtag' field match case according to the 1606 description in Section 3.1. The Reviewer MUST also ensure that an 1607 appropriate File-Date record is included in the request, to assist 1608 IANA when updating the registry (see Section 5.1). 1610 Some fields in both the registration form as well as the registry 1611 record itself permit the use of non-ASCII characters. Registration 1612 requests SHOULD use the UTF-8 encoding for consistency and clarity. 1613 However, since some mail clients do not support this encoding, other 1614 encodings MAY be used for the registration request. The Language 1615 Subtag Reviewer is responsible for ensuring that the proper Unicode 1616 characters appear in both the archived request form and the registry 1617 record. In the case of a transcription or encoding error by IANA, 1618 the Language Subtag Reviewer will request that the registry be 1619 repaired, providing any necessary information to assist IANA. 1621 Variant subtags are usually registered for use with a particular 1622 range of language tags. For example, the subtag 'rozaj' is intended 1623 for use with language tags that start with the primary language 1624 subtag "sl", since Resian is a dialect of Slovenian. Thus, the 1625 subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj" 1626 or "sl-IT-rozaj". This information is stored in the 'Prefix' field 1627 in the registry. Variant registration requests SHOULD include at 1628 least one 'Prefix' field in the registration form. 1630 The 'Prefix' field for a given registered subtag exists in the IANA 1631 registry as a guide to usage. Additional prefixes MAY be added by 1632 filing an additional registration form. In that form, the "Any other 1633 relevant information:" field MUST indicate that it is the addition of 1634 a prefix. 1636 Requests to add a prefix to a variant subtag that imply a different 1637 semantic meaning SHOULD be rejected. For example, a request to add 1638 the prefix "de" to the subtag 'nedis' so that the tag "de-nedis" 1639 represented some German dialect would be rejected. The 'nedis' 1640 subtag represents a particular Slovenian dialect and the additional 1641 registration would change the semantic meaning assigned to the 1642 subtag. A separate subtag SHOULD be proposed instead. 1644 The 'Description' field MUST contain a description of the tag being 1645 registered written or transcribed into the Latin script; it MAY also 1646 include a description in a non-Latin script. The 'Description' field 1647 is used for identification purposes and doesn't necessarily represent 1648 the actual native name of the language or variation or to be in any 1649 particular language. 1651 While the 'Description' field itself is not guaranteed to be stable 1652 and errata corrections MAY be undertaken from time to time, attempts 1653 to provide translations or transcriptions of entries in the registry 1654 itself will probably be frowned upon by the community or rejected 1655 outright, as changes of this nature have an impact on the provisions 1656 in Section 3.4. 1658 When the two-week period has passed, the Language Subtag Reviewer 1659 MUST take one of the following actions: 1661 o Explicitly accept the request and forward the form containing the 1662 record to be inserted or modified to iana@iana.org according to 1663 the procedure described in Section 3.3. 1665 o Explicitly reject the request because of significant objections 1666 raised on the list or due to problems with constraints in this 1667 document (which MUST be explicitly cited). 1669 o Extend the review period by granting an additional two-week 1670 increment to permit further discussion. After each two-week 1671 increment, the Language Subtag Reviewer MUST indicate on the list 1672 whether the registration has been accepted, rejected, or extended. 1674 Note that the Language Subtag Reviewer MAY raise objections on the 1675 list if he or she so desires. The important thing is that the 1676 objection MUST be made publicly. 1678 Sometimes the request needs to be modified as a result of discussion 1679 during the review period or due to requirements in this document. 1680 The applicant, Language Subtag Reviewer, or others are free to submit 1681 a modified version of the completed registration form, which will be 1682 considered in lieu of the original request with the explicit approval 1683 of the applicant. Such changes do not restart the two-week 1684 discussion period, although an application containing the final 1685 record submitted to IANA MUST appear on the list at least one week 1686 prior to the Language Subtag Reviewer forwarding the record to IANA. 1687 The applicant is also free to modify a rejected application with 1688 additional information and submit it again; this starts a new two- 1689 week comment period. 1691 Registrations initiated due to the provisions of Section 3.3 or 1692 Section 3.4 SHALL NOT be rejected altogether (since they have to 1693 ultimately appear in the registry) and SHOULD be completed as quickly 1694 as possible. The review process allows list members to comment on 1695 the specific information in the form and the record it contains and 1696 thus help ensure that it is correct and consistent. The Language 1697 Subtag Reviewer MAY reject a specific version of the form, but MUST 1698 include in the rejection a suitable replacement, extending the review 1699 period as described above, until the form is in a format worthy of 1700 reviewer's approval. 1702 Decisions made by the Language Subtag Reviewer MAY be appealed to the 1703 IESG [RFC2028] under the same rules as other IETF decisions 1705 [RFC2026]. This includes a decision to extend the review period or 1706 the failure to announce a decision in a clear and timely manner. 1708 The approved records appear in the Language Subtag Registry. The 1709 approved registration forms are available online under 1710 http://www.iana.org/assignments/lang-subtags-templates/. 1712 Updates or changes to existing records follow the same procedure as 1713 new registrations. The Language Subtag Reviewer decides whether 1714 there is consensus to update the registration following the two week 1715 review period; normally, objections by the original registrant will 1716 carry extra weight in forming such a consensus. 1718 Registrations are permanent and stable. Once registered, subtags 1719 will not be removed from the registry and will remain a valid way in 1720 which to specify a specific language or variant. 1722 Note: The purpose of the "Reference to published description" section 1723 in the registration form is to aid in verifying whether a language is 1724 registered or what language or language variation a particular subtag 1725 refers to. In most cases, reference to an authoritative grammar or 1726 dictionary of that language will be useful; in cases where no such 1727 work exists, other well-known works describing that language or in 1728 that language MAY be appropriate. The Language Subtag Reviewer 1729 decides what constitutes "good enough" reference material. This 1730 requirement is not intended to exclude particular languages or 1731 dialects due to the size of the speaker population or lack of a 1732 standardized orthography. Minority languages will be considered 1733 equally on their own merits. 1735 3.6. Possibilities for Registration 1737 Possibilities for registration of subtags or information about 1738 subtags include: 1740 o Primary language subtags for languages not listed in ISO 639 that 1741 are not variants of any listed or registered language MAY be 1742 registered. At the time this document was created, there were no 1743 examples of this form of subtag. Before attempting to register a 1744 language subtag, there MUST be an attempt to register the language 1745 with ISO 639. Subtags MUST NOT be registered for languages 1746 defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, 1747 or that are under consideration by the ISO 639 registration 1748 authorities, or that have never been attempted for registration 1749 with those authorities. If ISO 639 has previously rejected a 1750 language for registration, it is reasonable to assume that there 1751 must be additional, very compelling evidence of need before it 1752 will be registered as a primary language subtag in the IANA 1753 registry (to the extent that it is very unlikely that any subtags 1754 will be registered of this type). 1756 o Dialect or other divisions or variations within a language, its 1757 orthography, writing system, regional or historical usage, 1758 transliteration or other transformation, or distinguishing 1759 variation MAY be registered as variant subtags. An example is the 1760 'rozaj' subtag (the Resian dialect of Slovenian). 1762 o The addition or maintenance of fields (generally of an 1763 informational nature) in Tag or Subtag records as described in 1764 Section 3.1 and subject to the stability provisions in 1765 Section 3.4. This includes descriptions, comments, deprecation 1766 and preferred values for obsolete or withdrawn codes, or the 1767 addition of script or macrolanguage information to primary 1768 language subtags. 1770 o The addition of records and related field value changes necessary 1771 to reflect assignments made by ISO 639, ISO 15924, ISO 3166-1, and 1772 UN M.49 as described in Section 3.4. 1774 Subtags proposed for registration that would cause all or part of a 1775 grandfathered tag to become redundant but whose meaning conflicts 1776 with or alters the meaning of the grandfathered tag MUST be rejected. 1778 This document leaves the decision on what subtags or changes to 1779 subtags are appropriate (or not) to the registration process 1780 described in Section 3.5. 1782 Note: four-character primary language subtags are reserved to allow 1783 for the possibility of alpha4 codes in some future addition to the 1784 ISO 639 family of standards. 1786 ISO 639 defines a maintenance agency for additions to and changes in 1787 the list of languages in ISO 639. This agency is: 1789 International Information Centre for Terminology (Infoterm) 1790 Aichholzgasse 6/12, AT-1120 1791 Wien, Austria 1792 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1794 ISO 639-2 defines a maintenance agency for additions to and changes 1795 in the list of languages in ISO 639-2. This agency is: 1797 Library of Congress 1798 Network Development and MARC Standards Office 1799 Washington, D.C. 20540 USA 1800 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1801 URL: http://www.loc.gov/standards/iso639-2 1803 ISO 639-3 defines a maintenance agency for additions to and changes 1804 in the list of languages in ISO 639-3. This agency is: 1806 SIL International 1807 ISO 639-3 Registrar 1808 7500 W. Camp Wisdom Rd. 1809 Dallas, TX 75236 USA 1810 Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 1811 Email: iso639-3@sil.org 1812 URL: http://www.sil.org/iso639-3 1814 The maintenance agency for ISO 3166-1 (country codes) is: 1816 ISO 3166 Maintenance Agency 1817 c/o International Organization for Standardization 1818 Case postale 56 1819 CH-1211 Geneva 20 Switzerland 1820 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1821 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1823 The registration authority for ISO 15924 (script codes) is: 1825 Unicode Consortium Box 391476 1826 Mountain View, CA 94039-1476, USA 1827 URL: http://www.unicode.org/iso15924 1829 The Statistics Division of the United Nations Secretariat maintains 1830 the Standard Country or Area Codes for Statistical Use and can be 1831 reached at: 1833 Statistical Services Branch 1834 Statistics Division 1835 United Nations, Room DC2-1620 1836 New York, NY 10017, USA 1838 Fax: +1-212-963-0623 1839 E-mail: statistics@un.org 1840 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1842 3.7. Extensions and the Extensions Registry 1844 Extension subtags are those introduced by single-character subtags 1845 ("singletons") other than 'x'. They are reserved for the generation 1846 of identifiers that contain a language component and are compatible 1847 with applications that understand language tags. 1849 The structure and form of extensions are defined by this document so 1850 that implementations can be created that are forward compatible with 1851 applications that might be created using singletons in the future. 1852 In addition, defining a mechanism for maintaining singletons will 1853 lend stability to this document by reducing the likely need for 1854 future revisions or updates. 1856 Single-character subtags are assigned by IANA using the "IETF 1857 Consensus" policy defined by [RFC2434]. This policy requires the 1858 development of an RFC, which SHALL define the name, purpose, 1859 processes, and procedures for maintaining the subtags. The 1860 maintaining or registering authority, including name, contact email, 1861 discussion list email, and URL location of the registry, MUST be 1862 indicated clearly in the RFC. The RFC MUST specify or include each 1863 of the following: 1865 o The specification MUST reference the specific version or revision 1866 of this document that governs its creation and MUST reference this 1867 section of this document. 1869 o The specification and all subtags defined by the specification 1870 MUST follow the ABNF and other rules for the formation of tags and 1871 subtags as defined in this document. In particular, it MUST 1872 specify that case is not significant and that subtags MUST NOT 1873 exceed eight characters in length. 1875 o The specification MUST specify a canonical representation. 1877 o The specification of valid subtags MUST be available over the 1878 Internet and at no cost. 1880 o The specification MUST be in the public domain or available via a 1881 royalty-free license acceptable to the IETF and specified in the 1882 RFC. 1884 o The specification MUST be versioned, and each version of the 1885 specification MUST be numbered, dated, and stable. 1887 o The specification MUST be stable. That is, extension subtags, 1888 once defined by a specification, MUST NOT be retracted or change 1889 in meaning in any substantial way. 1891 o The specification MUST include in a separate section the 1892 registration form reproduced in this section (below) to be used in 1893 registering the extension upon publication as an RFC. 1895 o IANA MUST be informed of changes to the contact information and 1896 URL for the specification. 1898 IANA will maintain a registry of allocated single-character 1899 (singleton) subtags. This registry MUST use the record-jar format 1900 described by the ABNF in Section 3.1. Upon publication of an 1901 extension as an RFC, the maintaining authority defined in the RFC 1902 MUST forward this registration form to iesg@ietf.org, who MUST 1903 forward the request to iana@iana.org. The maintaining authority of 1904 the extension MUST maintain the accuracy of the record by sending an 1905 updated full copy of the record to iana@iana.org with the subject 1906 line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only 1907 the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY 1908 be modified in these updates. 1910 Failure to maintain this record, maintain the corresponding registry, 1911 or meet other conditions imposed by this section of this document MAY 1912 be appealed to the IESG [RFC2028] under the same rules as other IETF 1913 decisions (see [RFC2026]) and MAY result in the authority to maintain 1914 the extension being withdrawn or reassigned by the IESG. 1915 %% 1916 Identifier: 1917 Description: 1918 Comments: 1919 Added: 1920 RFC: 1921 Authority: 1922 Contact_Email: 1923 Mailing_List: 1924 URL: 1925 %% 1927 Figure 7: Format of Records in the Language Tag Extensions Registry 1929 'Identifier' contains the single-character subtag (singleton) 1930 assigned to the extension. The Internet-Draft submitted to define 1931 the extension SHOULD specify which letter or digit to use, although 1932 the IESG MAY change the assignment when approving the RFC. 1934 'Description' contains the name and description of the extension. 1936 'Comments' is an OPTIONAL field and MAY contain a broader description 1937 of the extension. 1939 'Added' contains the date the extension's RFC was published in the 1940 "full-date" format specified in [RFC3339]. For example: 2004-06-28 1941 represents June 28, 2004, in the Gregorian calendar. 1943 'RFC' contains the RFC number assigned to the extension. 1945 'Authority' contains the name of the maintaining authority for the 1946 extension. 1948 'Contact_Email' contains the email address used to contact the 1949 maintaining authority. 1951 'Mailing_List' contains the URL or subscription email address of the 1952 mailing list used by the maintaining authority. 1954 'URL' contains the URL of the registry for this extension. 1956 The determination of whether an Internet-Draft meets the above 1957 conditions and the decision to grant or withhold such authority rests 1958 solely with the IESG and is subject to the normal review and appeals 1959 process associated with the RFC process. 1961 Extension authors are strongly cautioned that many (including most 1962 well-formed) processors will be unaware of any special relationships 1963 or meaning inherent in the order of extension subtags. Extension 1964 authors SHOULD avoid subtag relationships or canonicalization 1965 mechanisms that interfere with matching or with length restrictions 1966 that sometimes exist in common protocols where the extension is used. 1967 In particular, applications MAY truncate the subtags in doing 1968 matching or in fitting into limited lengths, so it is RECOMMENDED 1969 that the most significant information be in the most significant 1970 (left-most) subtags and that the specification gracefully handle 1971 truncated subtags. 1973 When a language tag is to be used in a specific, known, protocol, it 1974 is RECOMMENDED that the language tag not contain extensions not 1975 supported by that protocol. In addition, note that some protocols 1976 MAY impose upper limits on the length of the strings used to store or 1977 transport the language tag. 1979 3.8. Update of the Language Subtag Registry 1981 Upon adoption of this document the IANA Language Subtag Registry will 1982 need an update so that it contains the complete set of subtags valid 1983 in a language tag. This collection of subtags, along with a 1984 description of the process used to create it, is described by 1985 [registry-update]. IANA will publish the updated version of the 1986 registry described by this document using the instructions and 1987 content of [registry-update]. Once published by IANA, the 1988 maintenance procedures, rules, and registration processes described 1989 in this document will be available for new registrations or updates. 1991 Registrations that are in process under the rules defined in 1992 [RFC4646] when this document is adopted MUST be completed under the 1993 rules contained in this document. 1995 4. Formation and Processing of Language Tags 1997 This section addresses how to use the information in the registry 1998 with the tag syntax to choose, form, and process language tags. 2000 4.1. Choice of Language Tag 2002 The guiding principle in forming language tags is to "tag content 2003 wisely." Sometimes there is a choice between several possible tags 2004 for the same content. The choice of which tag to use depends on the 2005 content and application in question and some amount of judgment might 2006 be necessary when selecting a tag. 2008 Interoperability is best served when the same language tag is used 2009 consistently to represent the same language. If an application has 2010 requirements that make the rules here inapplicable, then that 2011 application risks damaging interoperability. It is strongly 2012 RECOMMENDED that users not define their own rules for language tag 2013 choice. 2015 A subtag SHOULD only be used when it adds useful distinguishing 2016 information to the tag. Extraneous subtags interfere with the 2017 meaning, understanding, and processing of language tags. In 2018 particular, users and implementations SHOULD follow the 'Prefix' and 2019 'Suppress-Script' fields in the registry (defined in Section 3.1): 2020 these fields provide guidance on when specific additional subtags 2021 SHOULD be used or avoided in a language tag. 2023 Some applications can benefit from the use of script subtags in 2024 language tags, as long as the use is consistent for a given context. 2025 Script subtags are never appropriate for unwritten content (such as 2026 audio recordings). 2028 Script subtags were formally defined in BCP 47 by [RFC4646]. Their 2029 use can affect matching and subtag identification for implementations 2030 of previous versions of BCP 47 (i.e. [RFC1766] or [RFC3066]), as 2031 these subtags appear between the primary language and region subtags. 2032 For example, if an implementation selects content using Basic 2033 Filtering [RFC4647] (originally described in Section 2.5 of 2034 [RFC3066]) and the user requested the language range "en-US", content 2035 labeled "en-Latn-US" will not match the request and thus not be 2036 selected. Therefore, it is important to know when script subtags 2037 will customarily be used and when they ought not be used. In the 2038 registry, the Suppress-Script field helps ensure greater 2039 compatibility between the language tags by defining when users SHOULD 2040 NOT include a script subtag with a particular primary language 2041 subtag. 2043 The choice of subtags used to form a language tag SHOULD follow these 2044 guidelines: 2046 1. Use as precise a tag as possible, but no more specific than is 2047 justified. Avoid using subtags that are not important for 2048 distinguishing content in an application. 2050 * For example, 'de' might suffice for tagging an email written 2051 in German, while "de-CH-1996" is probably unnecessarily 2052 precise for such a task. 2054 * Note that some subtag sequences might not represent the 2055 language a casual user might expect, especially if when 2056 relying on the subtag's description in the registry. For 2057 example, the Swiss German (Schweizerdeutsch) language is 2058 represented by "gsw-CH" and not by "de-CH". This latter tag 2059 represents German ('de') as used in Switzerland ('CH'), also 2060 known as Swiss High German (Schweizer Hochdeutsch). Both are 2061 real languages and distinguishing between them could be 2062 important to an application. 2064 2. The script subtag SHOULD NOT be used to form language tags unless 2065 the script adds some distinguishing information to the tag. The 2066 field 'Suppress-Script' in the primary language record in the 2067 registry indicates script subtags that do not add distinguishing 2068 information for most applications. For example: 2070 * The subtag 'Latn' should not be used with the primary language 2071 'en' because nearly all English documents are written in the 2072 Latin script and it adds no distinguishing information. 2073 However, if a document were written in English mixing Latin 2074 script with another script such as Braille ('Brai'), then it 2075 might be appropriate to choose to indicate both scripts to aid 2076 in content selection, such as the application of a style 2077 sheet. 2079 * When labeling content that is unwritten (such as a recording 2080 of human speech), the script subtag should not be used, even 2081 if the language is customarily written in several scripts. 2082 Thus the subtitles to a movie might use the tag "zh-cmn-Hant" 2083 (Chinese, Mandarin, Traditional script), but the audio track 2084 for the same language would be tagged "zh-cmn". 2086 3. If a tag or subtag has a 'Preferred-Value' field in its registry 2087 entry, then the value of that field SHOULD be used to form the 2088 language tag in preference to the tag or subtag in which the 2089 preferred value appears. 2091 * For example, use 'he' for Hebrew in preference to 'iw'. 2093 4. [ISO639-2] has defined several codes included in the subtag 2094 registry that require additional care when choosing language 2095 tags. In most of these cases, where omitting the language tag is 2096 permitted, such omission is preferable to using these codes. 2097 Language tags SHOULD NOT incorporate these subtags as a prefix, 2098 unless the additional information conveys some value to the 2099 application. 2101 1. Use specific language subtags or subtag sequences in 2102 preference to subtags for language collections. A "language 2103 collection" is a subtag derived from one of the [ISO639-2] 2104 codes that represents multiple related languages. These 2105 codes are included as primary language subtags in the 2106 registry. For example, the code 'cmc' represents "Chamic 2107 languages". The registry contains values for each of the 2108 approximately ten individual languages represented by this 2109 collective code. Some other examples include the subtags 2110 Germanic languages ('gem') or Algonquian languages ('alg'). 2111 Since these codes are interpreted inclusively, content tagged 2112 with "en" (English), "de" (German), or "gsw" (Swiss German, 2113 Alemannic) could also (but SHOULD NOT) be tagged with "gem" 2114 (Germanic languages). Subtags derived from collection codes 2115 SHOULD NOT be used be used unless more specific language 2116 information is not available. Note that matching 2117 implementations generally do not understand the relationship 2118 between the collection and its encompassed languages, and so 2119 users ought not assume a subtag based on a language 2120 collection is a useful means for selecting content in its 2121 encompassed languages. 2123 2. The 'mul' (Multiple) primary language subtag identifies 2124 content in multiple languages. It SHOULD NOT be used when a 2125 list of languages (such as Content-Language) or individual 2126 tags for each content element can be used instead. 2128 3. The 'und' (Undetermined) primary language subtag identifies 2129 linguistic content whose language is not determined. It 2130 SHOULD NOT be used unless a language tag is required and 2131 language information is not available or cannot be 2132 determined. Omitting the language tag (where permitted) is 2133 preferred. The 'und' subtag MAY be useful for protocols that 2134 require a language tag to be provided or where a primary 2135 language subtag is required (such as in "und-Latn"). The 2136 'und' subtag MAY also be useful when matching language tags 2137 in certain situations. 2139 4. The 'zxx' (Non-Linguistic) primary language subtag identifies 2140 content that has no language. Some examples might include 2141 instrumental or electronic music; sound recordings consisting 2142 of nonverbal sounds; audiovisual materials with no narration, 2143 printed titles, or subtitles; machine-readable data files 2144 consisting of machine languages or character codes; or 2145 programming source code. Note: where there are fragments of 2146 linguistic content, such as programming source code 2147 containing comments written in English, the subtag 'zxx' 2148 might still be used to indicate the primary status of the 2149 content, just as 'en' can be applied to a predominantly 2150 English text that contains a few French phrases. 2152 5. The 'mis' (Uncoded) primary language subtag identifies 2153 content whose language is known but which does not currently 2154 have a corresponding subtag. This subtag SHOULD NOT be used. 2155 Because the addition of other codes in the future can render 2156 its application invalid, it is inherently unstable and hence 2157 incompatible with the stability goals of BCP 47. It is 2158 always preferable to use other subtags: either 'und' or (with 2159 prior agreement) private use subtags. 2161 6. The grandfathered tag "i-default" (Default Language) was 2162 originally registered according to [RFC1766] to meet the 2163 needs of [RFC2277]. It is used to indicate not a specific 2164 language, but rather, it identifies the condition or content 2165 used where the language preferences of the user cannot be 2166 established. It SHOULD NOT be used except as a means of 2167 labeling the default content for applications or protocols 2168 that require default language content to be labeled with that 2169 specific tag. It MAY also be used by an application or 2170 protocol to identify when the default language content is 2171 being returned. 2173 Some of the languages in the registry are labeled "macrolanguages" by 2174 ISO 639-3, which defines the term as "clusters of closely-related 2175 language varieties that [...] can be considered distinct individual 2176 languages, yet in certain usage contexts a single language identity 2177 for all is needed". These correspond to codes registered in ISO 2178 639-2 as single languages that were found to correspond to more than 2179 one language in ISO 639-3. The record for each of the languages 2180 encompassed by a macrolanguage contains a 'Macrolanguage' field in 2181 the registry; the macrolanguages themselves are not specially marked. 2183 It is always permitted, and sometimes useful, to tag an encompassed 2184 language using the subtag for its macrolanguage. However, the 2185 Macrolanguage field doesn't define what the relationship is between 2186 the encompassed language and its macrolanguage, nor does it define 2187 how languages encompassed by the same macrolanguage are related to 2188 each other. In some cases, one of the encompassed languages serves 2189 as a standard form for the entire macrolanguage and is frequently 2190 identified with it; in other cases there is no dominant language, and 2191 the macrolanguage simply serves as a cover term for the entire group. 2193 Applications MAY use macrolanguage information to improve matching or 2194 language negotiation. For example, the information that 'sr' 2195 (Serbian) and 'hr' (Croatian) share a macrolanguage expresses a 2196 closer relation between those languages than between, say, 'sr' 2197 (Serbian) and 'ma' (Macedonian). It is valid to use either the 2198 subtag of the encompassed language or of the macrolanguage to form 2199 language tags. However, many matching applications will not be aware 2200 of the relationship between the languages. Care in selecting which 2201 subtags are used is crucial to interoperability. 2203 In general, use the most specific subtag to form the language tag. 2204 However, where the macrolanguage tag has been historically used to 2205 denote a dominant encompassed language, it SHOULD be used in place of 2206 the subtag specific to that encompassed language unless it is 2207 necessary to clearly distinguish the macrolanguage as a whole from 2208 that enclosed dominant language variety. 2210 The pairs of macro and encompassed languages affected by this issue 2211 when this document was published were: 2213 Arabic 'ar' Standard Arabic 'arb' 2214 Konkani (macrolanguage) 'kok' Konkani (single language) 'knn' 2215 Malay (macrolanguage) 'ms' Malay (single language) 'mly' 2216 Swahili (macrolanguage) 'sw' Swahili (single language) 'swh' 2217 Uzbek 'uz' Northern Uzbek 'uzn' 2218 Chinese 'zh' Mandarin Chinese 'cmn' 2220 Figure 8 2222 In particular, the Chinese family of languages call for special 2223 consideration. Because the written form is very similar for most 2224 languages having 'zh' (Chinese) as a macrolanguage (and because 2225 historically subtags for the various encompassed languages were not 2226 available), languages such as 'yue' (Cantonese) have historically 2227 used either 'zh' or a tag (now grandfathered) beginning with 'zh'. 2228 This means that macrolanguage information can be usefully applied 2229 when searching for content or when providing fallbacks in language 2230 negotiation. For example, the information that 'yue' has a 2231 macrolangauge of 'zh' could be used in the Lookup algorithm to 2232 fallback from a request for "yue-Hans-CN" to "zh-Hans-CN" without 2233 losing the script and region information (even though the user did 2234 not specify "zh-Hans-CN" in their request). 2236 To ensure consistent backward compatibility, this document contains 2237 several provisions to account for potential instability in the 2238 standards used to define the subtags that make up language tags. 2239 These provisions mean that no language tag created under the rules in 2240 this document will become invalid, nor will a language tag have a 2241 narrower scope in the future (it may have a broader scope). 2243 Standards, protocols, and applications that reference this document 2244 normatively but apply different rules to the ones given in this 2245 section MUST specify how language tag selection varies from the 2246 guidelines given here. 2248 4.2. Meaning of the Language Tag 2250 The meaning of a language tag is related to the meaning of the 2251 subtags that it contains. Each subtag, in turn, implies a certain 2252 range of expectations one might have for related content, although it 2253 is not a guarantee. For example, the use of a script subtag such as 2254 'Arab' (Arabic script) does not mean that the content contains only 2255 Arabic characters. It does mean that the language involved is 2256 predominantly in the Arabic script. Thus a language tag and its 2257 subtags can encompass a very wide range of variation and yet remain 2258 appropriate in each particular instance. 2260 Validity of a tag is not the only factor determining its usefulness. 2261 While every valid tag has a meaning, it might not represent any real- 2262 world language usage. This is unavoidable in a system in which 2263 subtags can be combined freely. For example, tags such as 2264 "ar-Cyrl-CO" (Arabic, Cyrillic script, as used in Colombia ) or "tlh- 2265 Kore-AQ-fonipa" (Klingon, Korean script, as used in Antarctica, IPA 2266 phonetic transcription) are both valid and unlikely to represent a 2267 useful combination of language attributes. 2269 The meaning of a given tag doesn't depend on the context in which it 2270 appears. The relationship between a tag's meaning and the 2271 information objects to which that tag is applied, however, can vary. 2273 o For a single information object, the associated language tags 2274 might be interpreted as the set of languages that is necessary for 2275 a complete comprehension of the complete object. Example: Plain 2276 text documents. 2278 o For an aggregation of information objects, the associated language 2279 tags could be taken as the set of languages used inside components 2280 of that aggregation. Examples: Document stores and libraries. 2282 o For information objects whose purpose is to provide alternatives, 2283 the associated language tags could be regarded as a hint that the 2284 content is provided in several languages and that one has to 2285 inspect each of the alternatives in order to find its language or 2286 languages. In this case, the presence of multiple tags might not 2287 mean that one needs to be multi-lingual to get complete 2288 understanding of the document. Example: MIME multipart/ 2289 alternative. 2291 o In markup languages, such as HTML and XML, language information 2292 can be added to each part of the document identified by the markup 2293 structure (including the whole document itself). For example, one 2294 could write C'est la vie. inside a 2295 Norwegian document; the Norwegian-speaking user could then access 2296 a French-Norwegian dictionary to find out what the marked section 2297 meant. If the user were listening to that document through a 2298 speech synthesis interface, this formation could be used to signal 2299 the synthesizer to appropriately apply French text-to-speech 2300 pronunciation rules to that span of text, instead of applying the 2301 inappropriate Norwegian rules. 2303 o Language tags form the basis for most implementations of locale 2304 identifiers. For example, see Unicode's CLDR (Common Locale Data 2305 Repository) project. 2307 Language tags are related when they contain a similar sequence of 2308 subtags. For example, if a language tag B contains language tag A as 2309 a prefix, then B is typically "narrower" or "more specific" than A. 2310 Thus, "zh-Hant-TW" is more specific than "zh-Hant". 2312 This relationship is not guaranteed in all cases: specifically, 2313 languages that begin with the same sequence of subtags are NOT 2314 guaranteed to be mutually intelligible, although they might be. For 2315 example, the tag "az" shares a prefix with both "az-Latn" 2316 (Azerbaijani written using the Latin script) and "az-Cyrl" 2317 (Azerbaijani written using the Cyrillic script). A person fluent in 2318 one script might not be able to read the other, even though the text 2319 might be identical. Content tagged as "az" most probably is written 2320 in just one script and thus might not be intelligible to a reader 2321 familiar with the other script. 2323 Similarly, not all subtags specify an actual distinction in language. 2324 For example, the tags "en-US" and "en-CA" mean, roughly, English with 2325 features generally thought to be characteristic of the United States 2326 and Canada, respectively. They do not imply that a significant 2327 dialectical boundary exists between any arbitrarily selected point in 2328 the United States and any arbitrarily selected point in Canada. 2329 Neither does a particular region subtag imply that linguistic 2330 distinctions do not exist within that region. 2332 4.3. Length Considerations 2334 There is no defined upper limit on the size of language tags. While 2335 historically most language tags have consisted of language and region 2336 subtags with a combined total length of up to six characters, larger 2337 tags have always been both possible and actually appeared in use. 2339 Neither the language tag syntax nor other requirements in this 2340 document impose a fixed upper limit on the number of subtags in a 2341 language tag (and thus an upper bound on the size of a tag). The 2342 language tag syntax suggests that, depending on the specific 2343 language, more subtags (and thus a longer tag) are sometimes 2344 necessary to completely identify the language for certain 2345 applications; thus, it is possible to envision long or complex subtag 2346 sequences. 2348 4.3.1. Working with Limited Buffer Sizes 2350 Some applications and protocols are forced to allocate fixed buffer 2351 sizes or otherwise limit the length of a language tag. A conformant 2352 implementation or specification MAY refuse to support the storage of 2353 language tags that exceed a specified length. Any such limitation 2354 SHOULD be clearly documented, and such documentation SHOULD include 2355 what happens to longer tags (for example, whether an error value is 2356 generated or the language tag is truncated). A protocol that allows 2357 tags to be truncated at an arbitrary limit, without giving any 2358 indication of what that limit is, has the potential for causing harm 2359 by changing the meaning of tags in substantial ways. 2361 In practice, most language tags do not require more than a few 2362 subtags and will not approach reasonably sized buffer limitations; 2363 see Section 4.1. 2365 Some specifications or protocols have limits on tag length but do not 2366 have a fixed length limitation. For example, [RFC2231] has no 2367 explicit length limitation: the length available for the language tag 2368 is constrained by the length of other header components (such as the 2369 charset's name) coupled with the 76-character limit in [RFC2047]. 2370 Thus, the "limit" might be 50 or more characters, but it could 2371 potentially be quite small. 2373 The considerations for assigning a buffer limit are: 2375 Implementations SHOULD NOT truncate language tags unless the 2376 meaning of the tag is purposefully being changed, or unless the 2377 tag does not fit into a limited buffer size specified by a 2378 protocol for storage or transmission. 2380 Implementations SHOULD warn the user when a tag is truncated since 2381 truncation changes the semantic meaning of the tag. 2383 Implementations of protocols or specifications that are space 2384 constrained but do not have a fixed limit SHOULD use the longest 2385 possible tag in preference to truncation. 2387 Protocols or specifications that specify limited buffer sizes for 2388 language tags MUST allow for language tags of up to 33 characters. 2390 Protocols or specifications that specify limited buffer sizes for 2391 language tags SHOULD allow for language tags of at least 30 2392 characters. Note that RFC 4646 [RFC4646] recommended a field size 2393 of 42 character because it included the permanently reserved (and 2394 unused) 'extlang' production. The current size recommendation 2395 does not include the use of the 'extlang' field. Protocols or 2396 specifications that commonly use extensions or private use subtags 2397 might wish to reserve or recommend a longer "minimum buffer" size. 2399 The following illustration shows how the 30-character recommendation 2400 was derived: 2402 language = 3 (ISO 639-2; ISO 639-1 requires 2) 2403 script = 5 (if not suppressed: see Section 4.1) 2404 region = 4 (UN M.49; ISO 3166-1 requires 3) 2405 variant1 = 9 (needs 'language' as a prefix) 2406 variant2 = 9 (needs 'language-variant1' as a prefix) 2408 total = 30 characters 2410 Figure 9: Derivation of the Limit on Tag Length 2412 4.3.2. Truncation of Language Tags 2414 Truncation of a language tag alters the meaning of the tag, and thus 2415 SHOULD be avoided. However, truncation of language tags is sometimes 2416 necessary due to limited buffer sizes. Such truncation MUST NOT 2417 permit a subtag to be chopped off in the middle or the formation of 2418 invalid tags (for example, one ending with the "-" character). 2420 This means that applications or protocols that truncate tags MUST do 2421 so by progressively removing subtags along with their preceding "-" 2422 from the right side of the language tag until the tag is short enough 2423 for the given buffer. If the resulting tag ends with a single- 2424 character subtag, that subtag and its preceding "-" MUST also be 2425 removed. For example: 2427 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 2428 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 2429 2. zh-Latn-CN-variant1-a-extend1 2430 3. zh-Latn-CN-variant1 2431 4. zh-Latn-CN 2432 5. zh-Latn 2433 6. zh 2435 Figure 10: Example of Tag Truncation 2437 4.4. Canonicalization of Language Tags 2439 Since a particular language tag is sometimes used by many processes, 2440 language tags SHOULD always be created or generated in a canonical 2441 form. 2443 A language tag is in canonical form when: 2445 1. The tag is well-formed according the rules in Section 2.1 and 2446 Section 2.2. 2448 2. Subtags of type 'Region' that have a Preferred-Value mapping in 2449 the IANA registry (see Section 3.1) MUST be replaced with their 2450 mapped value. Note: In rare cases, the mapped value will also 2451 have a Preferred-Value. 2453 3. Redundant or grandfathered tags that have a Preferred-Value 2454 mapping in the IANA registry (see Section 3.1) MUST be replaced 2455 with their mapped value. These items either are deprecated 2456 mappings created before the adoption of this document (such as 2457 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 2458 the result of later registrations or additions to this document 2459 (for example, "zh-hakka" was deprecated in favor of the ISO 639-3 2460 code 'hak' when this document was adopted). 2462 4. Other subtags that have a Preferred-Value mapping in the IANA 2463 registry (see Section 3.1) MUST be replaced with their mapped 2464 value. These items consist entirely of clerical corrections to 2465 ISO 639-1 in which the deprecated subtags have been maintained 2466 for compatibility purposes. 2468 5. If more than one extension subtag sequence exists, the extension 2469 sequences are ordered into case-insensitive ASCII order by 2470 singleton subtag. 2472 Example: The language tag "en-a-aaa-b-ccc-bbb-x-xyz" is in canonical 2473 form, while "en-b-ccc-bbb-a-aaa-X-xyz" is well-formed and potentially 2474 valid (extensions 'a' and 'b' are not defined as of the publication 2475 of this document) but not in canonical form (the extensions are not 2476 in alphabetical order). 2478 Example: The language tag "en-BU" (English as used in Burma) is not 2479 canonical because the 'BU' subtag has a canonical mapping to 'MM' 2480 (Myanmar), although the tag "en-BU" maintains its validity. 2482 Canonicalization of language tags does not imply anything about the 2483 use of upper or lowercase letters when processing or comparing 2484 subtags (and as described in Section 2.1). All comparisons MUST be 2485 performed in a case-insensitive manner. 2487 When performing canonicalization of language tags, processors MAY 2488 regularize the case of the subtags (that is, this process is 2489 OPTIONAL), following the case used in the registry. Note that this 2490 corresponds to the following casing rules: uppercase all non-initial 2491 two-letter subtags; titlecase all non-initial four-letter subtags; 2492 lowercase everything else. 2494 Note: Case folding of ASCII letters in certain locales, unless 2495 carefully handled, sometimes produces non-ASCII character values. 2496 The Unicode Character Database file "SpecialCasing.txt" defines the 2497 specific cases that are known to cause problems with this. In 2498 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 2499 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 2500 Implementers SHOULD specify a locale-neutral casing operation to 2501 ensure that case folding of subtags does not produce this value, 2502 which is illegal in language tags. For example, if one were to 2503 uppercase the region subtag 'in' using Turkish locale rules, the 2504 sequence U+0130 U+004E would result instead of the expected 'IN'. 2506 Note: if the field 'Deprecated' appears in a registry record without 2507 an accompanying 'Preferred-Value' field, then that tag or subtag is 2508 deprecated without a replacement. Validating processors SHOULD NOT 2509 generate tags that include these values, although the values are 2510 canonical when they appear in a language tag. 2512 An extension MUST define any relationships that exist between the 2513 various subtags in the extension and thus MAY define an alternate 2514 canonicalization scheme for the extension's subtags. Extensions MAY 2515 define how the order of the extension's subtags are interpreted. For 2516 example, an extension could define that its subtags are in canonical 2517 order when the subtags are placed into ASCII order: that is, "en-a- 2518 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 2519 define that the order of the subtags influences their semantic 2520 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 2521 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 2522 so that they are tolerant of the typical processes described in 2523 Section 3.7. 2525 4.5. Considerations for Private Use Subtags 2527 Private use subtags, like all other subtags, MUST conform to the 2528 format and content constraints in the ABNF. Private use subtags have 2529 no meaning outside the private agreement between the parties that 2530 intend to use or exchange language tags that employ them. The same 2531 subtags MAY be used with a different meaning under a separate private 2532 agreement. They SHOULD NOT be used where alternatives exist and 2533 SHOULD NOT be used in content or protocols intended for general use. 2535 Private use subtags are simply useless for information exchange 2536 without prior arrangement. The value and semantic meaning of private 2537 use tags and of the subtags used within such a language tag are not 2538 defined by this document. 2540 Subtags defined in the IANA registry as having a specific private use 2541 meaning convey more information that a purely private use tag 2542 prefixed by the singleton subtag 'x'. For applications, this 2543 additional information MAY be useful. 2545 For example, the region subtags 'AA', 'ZZ', and in the ranges 2546 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166-1 private use codes) 2547 MAY be used to form a language tag. A tag such as "zh-Hans-XQ" 2548 conveys a great deal of public, interchangeable information about the 2549 language material (that it is Chinese in the simplified Chinese 2550 script and is suitable for some geographic region 'XQ'). While the 2551 precise geographic region is not known outside of private agreement, 2552 the tag conveys far more information than an opaque tag such as 2553 "x-someLang", which contains no information about the language subtag 2554 or script subtag outside of the private agreement. 2556 However, in some cases content tagged with private use subtags MAY 2557 interact with other systems in a different and possibly unsuitable 2558 manner compared to tags that use opaque, privately defined subtags, 2559 so the choice of the best approach sometimes depends on the 2560 particular domain in question. 2562 5. IANA Considerations 2564 This section deals with the processes and requirements necessary for 2565 IANA to undertake to maintain the subtag and extension registries as 2566 defined by this document and in accordance with the requirements of 2567 [RFC2434]. 2569 The impact on the IANA maintainers of the two registries defined by 2570 this document will be a small increase in the frequency of new 2571 entries or updates. IANA also is required to create a new mailing 2572 list (described below in Section 5.1) to announce registry changes 2573 and updates. 2575 5.1. Language Subtag Registry 2577 Upon adoption of this document, IANA will update the registry using 2578 instructions and content provided in a companion document: 2579 [registry-update]. The criteria and process for selecting the 2580 updated set of records are described in that document. The updated 2581 set of records represents no impact on IANA, since the work to create 2582 it will be performed externally. 2584 Future work on the Language Subtag Registry includes the following 2585 activities: 2587 o Inserting or replacing whole records. These records are 2588 preformatted for IANA by the Language Subtag Reviewer, as 2589 described in Section 3.3. 2591 o Archiving and making publicly available the registration forms. 2593 o Announcing each updated version of the registry on the 2594 "ietf-languages-announcements@iana.org" mailing list. 2596 Each registration form sent to IANA contains a single record for 2597 incorporation into the registry. The form will be sent to 2598 "iana@iana.org" by the Language Subtag Reviewer. It will have a 2599 subject line indicating whether the enclosed form represents an 2600 insertion of a new record (indicated by the word "INSERT" in the 2601 subject line) or a replacement of an existing record (indicated by 2602 the word "MODIFY" in the subject line). At no time can a record be 2603 deleted from the registry. 2605 IANA will extract the record from the form and place the inserted or 2606 modified record into the appropriate section of the language subtag 2607 registry, grouping the records by their 'Type' field. Inserted 2608 records can be placed anywhere in the appropriate section; there is 2609 no guarantee of the order of the records beyond grouping them 2610 together by 'Type'. Modified records overwrite the record they 2611 replace. 2613 Whenever an entry is created or modified in the registry, the 'File- 2614 Date' record at the start of the registry is updated to reflect the 2615 most recent modification date in the [RFC3339] "full-date" format: 2616 included in any request to insert or modify records will be a new 2617 File-Date record indicating the acceptance date of the record. This 2618 record is to be placed first in the registry, replacing the existing 2619 File-Date record. In the event that the File-Date record present in 2620 the registry has a later date than the record being inserted or 2621 modified, then the latest (most recent) record will be preserved. 2622 IANA should attempt to process multiple registration requests in 2623 order according to the File-Date in the form, since one registration 2624 could otherwise cause a more recent change to be overwritten. 2626 The updated registry file MUST use the UTF-8 character encoding and 2627 IANA MUST check the registry file for proper encoding. Non-ASCII 2628 characters can be sent to IANA by attaching the registration form to 2629 the email message or by using various encodings in the mail message 2630 body (UTF-8 is recommended). IANA will verify any unclear or 2631 corrupted characters with the Language Subtag Reviewer prior to 2632 posting the updated registry. 2634 IANA will also archive and make publicly available from 2635 "http://www.iana.org/assignments/lang-subtags-templates/" each 2636 registration form. Note that multiple registrations can pertain to 2637 the same record in the registry. 2639 Developers who are dependent upon the language subtag registry 2640 sometimes would like to be informed of changes in the registry so 2641 that they can update their implementations. When any change is made 2642 to the language subtag registry, IANA will send an announcement 2643 message to "ietf-languages-announcements@iana.org" (a self- 2644 subscribing list that only IANA can post to). 2646 5.2. Extensions Registry 2648 The Language Tag Extensions Registry can contain at most 35 records 2649 and thus changes to this registry are expected to be very infrequent. 2651 Future work by IANA on the Language Tag Extensions Registry is 2652 limited to two cases. First, the IESG MAY request that new records 2653 be inserted into this registry from time to time. These requests 2654 MUST include the record to insert in the exact format described in 2655 Section 3.7. In addition, there MAY be occasional requests from the 2656 maintaining authority for a specific extension to update the contact 2657 information or URLs in the record. These requests MUST include the 2658 complete, updated record. IANA is not responsible for validating the 2659 information provided, only that it is properly formatted. It should 2660 reasonably be seen to come from the maintaining authority named in 2661 the record present in the registry. 2663 6. Security Considerations 2665 Language tags used in content negotiation, like any other information 2666 exchanged on the Internet, might be a source of concern because they 2667 might be used to infer the nationality of the sender, and thus 2668 identify potential targets for surveillance. 2670 This is a special case of the general problem that anything sent is 2671 visible to the receiving party and possibly to third parties as well. 2672 It is useful to be aware that such concerns can exist in some cases. 2674 The evaluation of the exact magnitude of the threat, and any possible 2675 countermeasures, is left to each application protocol (see BCP 72 2676 [RFC3552] for best current practice guidance on security threats and 2677 defenses). 2679 The language tag associated with a particular information item is of 2680 no consequence whatsoever in determining whether that content might 2681 contain possible homographs. The fact that a text is tagged as being 2682 in one language or using a particular script subtag provides no 2683 assurance whatsoever that it does not contain characters from scripts 2684 other than the one(s) associated with or specified by that language 2685 tag. 2687 Since there is no limit to the number of variant, private use, and 2688 extension subtags, and consequently no limit on the possible length 2689 of a tag, implementations need to guard against buffer overflow 2690 attacks. See Section 4.3 for details on language tag truncation, 2691 which can occur as a consequence of defenses against buffer overflow. 2693 Although the specification of valid subtags for an extension (see 2694 Section 3.7) MUST be available over the Internet, implementations 2695 SHOULD NOT mechanically depend on it being always accessible, to 2696 prevent denial-of-service attacks. 2698 7. Character Set Considerations 2700 The syntax in this document requires that language tags use only the 2701 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2702 character sets, so the composition of language tags should not have 2703 any character set issues. 2705 Rendering of characters based on the content of a language tag is not 2706 addressed in this memo. Historically, some languages have relied on 2707 the use of specific character sets or other information in order to 2708 infer how a specific character should be rendered (notably this 2709 applies to language- and culture-specific variations of Han 2710 ideographs as used in Japanese, Chinese, and Korean). When language 2711 tags are applied to spans of text, rendering engines sometimes use 2712 that information in deciding which font to use in the absence of 2713 other information, particularly where languages with distinct writing 2714 traditions use the same characters. 2716 8. Changes from RFC 4646 2718 The main goal for this revision of this document was to incorporate 2719 ISO 639-3 and its attendant set of language codes into the IANA 2720 Language Subtag Registry, permitting the identification of many more 2721 languages and dialects than previously supported. 2723 The specific changes in this document to meet these goals are: 2725 o Defines the incorporation of ISO 639-3 codes as language. It also 2726 permanently reserves and disallows the use of extlang subtags. 2727 The changes necessary to achieve this were: 2729 * Modified the ABNF comments. 2731 * Updated various registration and stability requirements 2732 sections to reference ISO 639-3 in addition to ISO 639-1 and 2733 ISO 639-2. 2735 * Edited the text to eliminate references to extended language 2736 subtags where they are no longer used. 2738 * Explained the change in the section on extended language 2739 subtags. 2741 o Changed the ABNF related to grandfathered tags. The irregular 2742 tags are now listed. Well-formed grandfathered tags are now 2743 described by the 'langtag' production and the 'grandfathered' 2744 production was removed as a result. Also: added description of 2745 both types of grandfathered tags to Section 2.2.8. 2747 o Added the paragraph on "collections" to Section 4.1. 2749 o Changed the capitalization rules for 'Tag' fields in Section 3.1. 2751 o Split section 3.1 up into subsections. 2753 o Modified section 3.5 to allow Suppress-Script fields to be added, 2754 modified, or removed via the registration process. This was an 2755 erratum from RFC 4646. 2757 o Modified examples that used region code 'CS' (formerly Serbia and 2758 Montenegro) to use 'RS' (Serbia) instead. 2760 o Modified the rules for creating and maintaining record 2761 'Description' fields to prevent duplicates, including inverted 2762 duplicates. 2764 o Removed the lengthy description of why RFC 4646 was created from 2765 this section, which also caused the removal of the reference to 2766 XML Schema. 2768 o Modified the text in section 2.1 to place more emphasis on the 2769 fact that language tags are not case sensitive. 2771 o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" 2772 and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the 2773 Suppress-Script on 'Latn' with 'fr'. 2775 o Changed the requirements for well-formedness to make singleton 2776 repetition checking optional (it is required for validity 2777 checking) in Section 2.2.9. 2779 o Changed the text in Section 2.2.9 referring to grandfathered 2780 checking to note that the list is now included in the ABNF. 2782 o Modified and added text to Section 3.2. The job description was 2783 placed first. A note was added making clear that the Language 2784 Subtag Reviewer may delegate various non-critical duties, 2785 including list moderation. Finally, additional text was added to 2786 make the appointment process clear and to clarify that decisions 2787 and performance of the reviewer are appealable. 2789 o Added text to Section 3.5 clarifying that the ietf-languages list 2790 is operated by whomever the IESG appoints. 2792 o Added text to Section 3.1.4 clarifying that the first Description 2793 in a 'language' record matches the corresponding Reference Name 2794 for the language in ISO 639-3. 2796 o Modified Section 2.2.9 to define classes of conformance related to 2797 specific tags (formerly 'well-formed' and 'valid' referred to 2798 implementations). Notes were added about the removal of 'extlang' 2799 from the ABNF provided in RFC 4646, allowing for well-formedness 2800 using this older definition. Reference to RFC 3066 well- 2801 formedness was also added. 2803 o Added text to the end of Section 3.1.2 noting that future versions 2804 of this document might add new field types to the Registry format 2805 and recommending that implementations ignore any unrecognized 2806 fields. 2808 o Added text about what the lack of a Suppress-Script field means in 2809 a record to Section 3.1.8. 2811 o Added text allowing the correction of misspellings and typographic 2812 errors to Section 3.1.4. 2814 o Added text to Section 3.1.7 disallowing Prefix field conflicts 2815 (such as circular prefix references). 2817 o Modified text in Section 3.5 to require the subtag reviewer to 2818 announce his/her decision (or extension) following the two-week 2819 period. Also clarified that any decision or failure to decide can 2820 be appealed. 2822 o Modified text in Section 4.1 to include the (heretofore anecdotal) 2823 guiding principle of tag choice, and clarifying the non-use of 2824 script subtags in non-written applications. Also updated examples 2825 in this section to use Chamic languages as an example of language 2826 collections. 2828 o Prohibited multiple use of the same variant in a tag (i.e. "de- 2829 1901-1901"). Previously this was only a recommendation 2830 ("SHOULD"). 2832 o Removed inappropriate [RFC2119] language from the illustration in 2833 Section 4.3.1. 2835 o Replaced the example of deprecating "zh-gouyu" with "zh- 2836 hakka"->"hak" in Section 4.4, noting that it was this document 2837 that caused the change. 2839 o Replaced the section in Section 4.1 dealing with "mul"/"und" to 2840 include the subtags 'zxx' and 'mis', as well as the tag 2841 "i-default". A normative reference to RFC 2277 was added, along 2842 with an informative reference to MARC21. 2844 o Added text to Section 3.5 clarifying that any modifications of a 2845 registration request must be sent to the ietf-languages list 2846 before submission to IANA. 2848 o Changed the ABNF for the record-jar format from using the LWSP 2849 production to use a folding whitespace production similar to obs- 2850 FWS in [RFC5234]. This effectively prevents unintentional blank 2851 lines inside a field. 2853 o Clarified and revised text in Section 3.3, Section 3.5, and 2854 Section 5.1 to clarify that the Language Subtag Reviewer sends the 2855 complete registration forms to IANA, that IANA extracts the record 2856 from the form, and that the forms must also be archived separately 2857 from the registry. 2859 o Added text to Section 5 requiring IANA to send an announcement to 2860 an ietf-languages-announce list whenever the registry is updated. 2862 o Modification of the registry to use UTF-8 as its character 2863 encoding. This also entails additional instructions to IANA and 2864 the Language Subtag Reviewer in the registration process. 2866 o Modified the rules in Section 2.2.4 so that "exceptionally 2867 reserved" ISO 3166-1 codes other than 'UK' were included into the 2868 registry. In particular, this allows the code 'EU' (European 2869 Union) to be used to form language tags or (more commonly) for 2870 applications that use the registry for region codes to reference 2871 this subtag. 2873 o Modified the IANA considerations section (Section 5) to remove 2874 unnecessary normative [RFC2119] language. 2876 9. References 2878 9.1. Normative References 2880 [ISO15924] 2881 International Organization for Standardization, "ISO 2882 15924:2004. Information and documentation -- Codes for the 2883 representation of names of scripts", January 2004. 2885 [ISO3166-1] 2886 International Organization for Standardization, "ISO 3166- 2887 1:2006. Codes for the representation of names of countries 2888 and their subdivisions -- Part 1: Country codes", 2889 November 2006. 2891 [ISO639-1] 2892 International Organization for Standardization, "ISO 639- 2893 1:2002. Codes for the representation of names of languages 2894 -- Part 1: Alpha-2 code", 2002. 2896 [ISO639-2] 2897 International Organization for Standardization, "ISO 639- 2898 2:1998. Codes for the representation of names of languages 2899 -- Part 2: Alpha-3 code, first edition", 1998. 2901 [ISO639-3] 2902 International Organization for Standardization, "ISO 639- 2903 3:2007. Codes for the representation of names of languages 2904 -- Part 3: Alpha-3 code for comprehensive coverage of 2905 languages", 2007. 2907 [ISO646] International Organization for Standardization, "ISO/IEC 2908 646:1991, Information technology -- ISO 7-bit coded 2909 character set for information interchange.", 1991. 2911 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 2912 3", BCP 9, RFC 2026, October 1996. 2914 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 2915 the IETF Standards Process", BCP 11, RFC 2028, 2916 October 1996. 2918 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2919 Requirement Levels", BCP 14, RFC 2119, March 1997. 2921 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and 2922 Languages", BCP 18, RFC 2277, January 1998. 2924 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2925 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 2926 October 1998. 2928 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2929 Understanding Concerning the Technical Work of the 2930 Internet Assigned Numbers Authority", RFC 2860, June 2000. 2932 [RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the 2933 Internet: Timestamps", RFC 3339, July 2002. 2935 [RFC4645] Ewell, D., "Initial Language Subtag Registry", RFC 4645, 2936 September 2006. 2938 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 2939 BCP 47, RFC 4647, September 2006. 2941 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2942 Specifications: ABNF", STD 68, RFC 5234, January 2008. 2944 [UAX14] Freitag, A., "Unicode Standard Annex #14: Line Breaking 2945 Properties", August 2006, 2946 . 2948 [UN_M.49] Statistics Division, United Nations, "Standard Country or 2949 Area Codes for Statistical Use", UN Standard Country or 2950 Area Codes for Statistical Use, Revision 4 (United Nations 2951 publication, Sales No. 98.XVII.9, June 1999. 2953 9.2. Informative References 2955 [RFC1766] Alvestrand, H., "Tags for the Identification of 2956 Languages", RFC 1766, March 1995. 2958 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 2959 Part Three: Message Header Extensions for Non-ASCII Text", 2960 RFC 2047, November 1996. 2962 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 2963 Word Extensions: 2964 Character Sets, Languages, and Continuations", RFC 2231, 2965 November 1997. 2967 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 2968 10646", RFC 2781, February 2000. 2970 [RFC3066] Alvestrand, H., "Tags for the Identification of 2971 Languages", RFC 3066, January 2001. 2973 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2974 Text on Security Considerations", BCP 72, RFC 3552, 2975 July 2003. 2977 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 2978 10646", STD 63, RFC 3629, November 2003. 2980 [RFC4646] Phillips, A. and M. Davis, "Tags for Identifying 2981 Languages", BCP 47, RFC 4646, September 2006. 2983 [UTS35] Davis, M., "Unicode Technical Standard #35: Locale Data 2984 Markup Language (LDML)", December 2007, 2985 . 2987 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 2988 Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. 2989 ISBN 0-321-49081-0)", January 2007. 2991 [iso639.prin] 2992 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2993 Committee: Working principles for ISO 639 maintenance", 2994 March 2000, 2995 . 2998 [record-jar] 2999 Raymond, E., "The Art of Unix Programming", 2003, 3000 . 3002 [registry-update] 3003 Ewell, D., Ed., "Update to the Language Subtag Registry", 3004 September 2006, . 3007 Appendix A. Acknowledgements 3009 Any list of contributors is bound to be incomplete; please regard the 3010 following as only a selection from the group of people who have 3011 contributed to make this document what it is today. 3013 The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the 3014 precursors of this document, made enormous contributions directly or 3015 indirectly to this document and are generally responsible for the 3016 success of language tags. 3018 The following people contributed to this document: 3020 Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, 3021 Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion 3022 Gunn, Kent Karlsson, Chris Newman, Randy Presuhn, Stephen Silver, and 3023 many, many others. 3025 Very special thanks must go to Harald Tveit Alvestrand, who 3026 originated RFCs 1766 and 3066, and without whom this document would 3027 not have been possible. 3029 Special thanks go to Michael Everson, who served as the Language Tag 3030 Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as 3031 the Language Subtag Reviewer since the adoption of RFC 4646. 3033 Special thanks also to Doug Ewell, for his production of the first 3034 complete subtag registry, his work to support and maintain new 3035 registrations, and his careful editorship of both RFC 4645 and 3036 [registry-update]. 3038 Appendix B. Examples of Language Tags (Informative) 3040 Simple language subtag: 3042 de (German) 3044 fr (French) 3046 ja (Japanese) 3048 i-enochian (example of a grandfathered tag) 3050 Language subtag plus Script subtag: 3052 zh-Hant (Chinese written using the Traditional Chinese script) 3054 zh-Hans (Chinese written using the Simplified Chinese script) 3056 sr-Cyrl (Serbian written using the Cyrillic script) 3058 sr-Latn (Serbian written using the Latin script) 3060 Language-Script-Region: 3062 zh-Hans-CN (Chinese written using the Simplified script as used in 3063 mainland China) 3065 sr-Latn-RS (Serbian written using the Latin script as used in 3066 Serbia) 3068 Language-Variant: 3070 sl-rozaj (Resian dialect of Slovenian) 3072 sl-nedis (Nadiza dialect of Slovenian) 3074 Language-Region-Variant: 3076 de-CH-1901 (German as used in Switzerland using the 1901 variant 3077 [orthography]) 3079 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 3081 Language-Script-Region-Variant: 3083 hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as 3084 used in Italy) 3086 Language-Region: 3088 de-DE (German for Germany) 3090 en-US (English as used in the United States) 3092 es-419 (Spanish appropriate for the Latin America and Caribbean 3093 region using the UN region code) 3095 Private use subtags: 3097 de-CH-x-phonebk 3099 az-Arab-x-AZE-derbend 3101 Private use registry values: 3103 x-whatever (private use using the singleton 'x') 3105 qaa-Qaaa-QM-x-southern (all private tags) 3107 de-Qaaa (German, with a private script) 3109 sr-Latn-QM (Serbian, Latin-script, private region) 3111 sr-Qaaa-RS (Serbian, private script, for Serbia) 3113 Tags that use extensions (examples ONLY: extensions MUST be defined 3114 by revision or update to this document or by RFC): 3116 en-US-u-islamCal 3118 zh-CN-a-myExt-x-private 3120 en-a-myExt-b-another 3122 Some Invalid Tags: 3124 de-419-DE (two region tags) 3126 a-DE (use of a single-character subtag in primary position; note 3127 that there are a few grandfathered tags that start with "i-" that 3128 are valid) 3129 ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter 3130 prefix) 3132 Appendix C. Examples of Registration Forms 3133 LANGUAGE SUBTAG REGISTRATION FORM 3134 1. Name of requester: Han Steenwijk 3135 2. E-mail address of requester: han.steenwijk @ unipd.it 3136 3. Record Requested: 3138 Type: variant 3139 Subtag: biske 3140 Description: The San Giorgio dialect of Resian 3141 Description: The Bila dialect of Resian 3142 Prefix: sl-rozaj 3143 Comments: The dialect of San Giorgio/Bila is one of the 3144 four major local dialects of Resian 3146 4. Intended meaning of the subtag: The local variety of Resian as 3147 spoken in San Giorgio/Bila 3149 5. Reference to published description of the language (book or 3150 article): 3151 -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich 3152 govorov, Varsava - Peterburg: Vende - Kozancikov, 1875. 3154 LANGUAGE SUBTAG REGISTRATION FORM 3155 1. Name of requester: Jaska Zedlik 3156 2. E-mail address of requester: jz53 @ zedlik.com 3157 3. Record Requested: 3159 Type: variant 3160 Subtag: tarask 3161 Description: Belarusian in Taraskievica orthography 3162 Prefix: be 3163 Comments: The subtag represents Branislau Taraskievic's Belarusian 3164 orthography as published in "Bielaruski klasycny pravapis" by Juras 3165 Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka 3166 (Vilnia-Miensk 2005). 3168 4. Intended meaning of the subtag: 3170 The subtag is intended to represent the Belarusian orthography as 3171 published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk 3172 Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005). 3174 5. Reference to published description of the language (book or article): 3176 Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd. 3177 "Bielaruskaha kamitetu", 1929, 5th edition. 3179 Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier. 3180 Bielaruski klasycny pravapis. Vilnia-Miensk, 2005. 3182 6. Any other relevant information: 3184 Belarusian in Taraskievica orthography became widely used, especially in 3185 Belarusian-speaking Internet segment, but besides this some books and 3186 newspapers are also printed using this orthography of Belarusian. 3188 Authors' Addresses 3190 Addison Phillips (editor) 3191 Lab126 3193 Email: addison@inter-locale.com 3194 URI: http://www.inter-locale.com 3196 Mark Davis (editor) 3197 Google 3199 Email: mark.davis@google.com 3201 Full Copyright Statement 3203 Copyright (C) The IETF Trust (2008). 3205 This document is subject to the rights, licenses and restrictions 3206 contained in BCP 78, and except as set forth therein, the authors 3207 retain all their rights. 3209 This document and the information contained herein are provided on an 3210 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 3211 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 3212 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 3213 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 3214 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 3215 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 3217 Intellectual Property 3219 The IETF takes no position regarding the validity or scope of any 3220 Intellectual Property Rights or other rights that might be claimed to 3221 pertain to the implementation or use of the technology described in 3222 this document or the extent to which any license under such rights 3223 might or might not be available; nor does it represent that it has 3224 made any independent effort to identify any such rights. Information 3225 on the procedures with respect to rights in RFC documents can be 3226 found in BCP 78 and BCP 79. 3228 Copies of IPR disclosures made to the IETF Secretariat and any 3229 assurances of licenses to be made available, or the result of an 3230 attempt made to obtain a general license or permission for the use of 3231 such proprietary rights by implementers or users of this 3232 specification can be obtained from the IETF on-line IPR repository at 3233 http://www.ietf.org/ipr. 3235 The IETF invites any interested party to bring to its attention any 3236 copyrights, patents or patent applications, or other proprietary 3237 rights that may cover technology that may be required to implement 3238 this standard. Please address the information to the IETF at 3239 ietf-ipr@ietf.org.