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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 (December 4, 2007) is 5988 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 ** Obsolete normative reference: RFC 4234 (Obsoleted by RFC 5234) ** Downref: Normative reference to an Informational RFC: RFC 4645 -- 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: 6 errors (**), 0 flaws (~~), 2 warnings (==), 17 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 Yahoo! Inc. 4 Obsoletes: 4646 (if approved) M. Davis, Ed. 5 Intended status: Best Current Google 6 Practice December 4, 2007 7 Expires: June 6, 2008 9 Tags for Identifying Languages 10 draft-ietf-ltru-4646bis-10 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on June 6, 2008. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 41 Abstract 43 This document describes the structure, content, construction, and 44 semantics of language tags for use in cases where it is desirable to 45 indicate the language used in an information object. It also 46 describes how to register values for use in language tags and the 47 creation of user-defined extensions for private interchange. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 52 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 5 53 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 5 54 2.2. Language Subtag Sources and Interpretation . . . . . . . . 8 55 2.2.1. Primary Language Subtag . . . . . . . . . . . . . . . 9 56 2.2.2. Extended Language Subtags . . . . . . . . . . . . . . 11 57 2.2.3. Script Subtag . . . . . . . . . . . . . . . . . . . . 11 58 2.2.4. Region Subtag . . . . . . . . . . . . . . . . . . . . 12 59 2.2.5. Variant Subtags . . . . . . . . . . . . . . . . . . . 14 60 2.2.6. Extension Subtags . . . . . . . . . . . . . . . . . . 15 61 2.2.7. Private Use Subtags . . . . . . . . . . . . . . . . . 16 62 2.2.8. Grandfathered Registrations . . . . . . . . . . . . . 17 63 2.2.9. Classes of Conformance . . . . . . . . . . . . . . . . 18 64 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 19 65 3.1. Format of the IANA Language Subtag Registry . . . . . . . 19 66 3.1.1. File Format . . . . . . . . . . . . . . . . . . . . . 19 67 3.1.2. Record Definitions . . . . . . . . . . . . . . . . . . 20 68 3.1.3. Subtag and Tag Fields . . . . . . . . . . . . . . . . 22 69 3.1.4. Description Field . . . . . . . . . . . . . . . . . . 23 70 3.1.5. Deprecated Field . . . . . . . . . . . . . . . . . . . 24 71 3.1.6. Preferred-Value Field . . . . . . . . . . . . . . . . 24 72 3.1.7. Prefix Field . . . . . . . . . . . . . . . . . . . . . 25 73 3.1.8. Suppress-Script Field . . . . . . . . . . . . . . . . 26 74 3.1.9. Macrolanguage Field . . . . . . . . . . . . . . . . . 26 75 3.1.10. Comments Field . . . . . . . . . . . . . . . . . . . . 27 76 3.2. Language Subtag Reviewer . . . . . . . . . . . . . . . . . 27 77 3.3. Maintenance of the Registry . . . . . . . . . . . . . . . 27 78 3.4. Stability of IANA Registry Entries . . . . . . . . . . . . 28 79 3.5. Registration Procedure for Subtags . . . . . . . . . . . . 32 80 3.6. Possibilities for Registration . . . . . . . . . . . . . . 36 81 3.7. Extensions and Extensions Registry . . . . . . . . . . . . 38 82 3.8. Update of the Language Subtag Registry . . . . . . . . . . 41 83 4. Formation and Processing of Language Tags . . . . . . . . . . 42 84 4.1. Choice of Language Tag . . . . . . . . . . . . . . . . . . 42 85 4.2. Meaning of the Language Tag . . . . . . . . . . . . . . . 46 86 4.3. Length Considerations . . . . . . . . . . . . . . . . . . 48 87 4.3.1. Working with Limited Buffer Sizes . . . . . . . . . . 48 88 4.3.2. Truncation of Language Tags . . . . . . . . . . . . . 49 89 4.4. Canonicalization of Language Tags . . . . . . . . . . . . 50 90 4.5. Considerations for Private Use Subtags . . . . . . . . . . 52 91 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53 92 5.1. Language Subtag Registry . . . . . . . . . . . . . . . . . 53 93 5.2. Extensions Registry . . . . . . . . . . . . . . . . . . . 54 94 6. Security Considerations . . . . . . . . . . . . . . . . . . . 55 95 7. Character Set Considerations . . . . . . . . . . . . . . . . . 56 96 8. Changes from RFC 4646 . . . . . . . . . . . . . . . . . . . . 57 97 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 61 98 9.1. Normative References . . . . . . . . . . . . . . . . . . . 61 99 9.2. Informative References . . . . . . . . . . . . . . . . . . 62 100 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 64 101 Appendix B. Examples of Language Tags (Informative) . . . . . . . 65 102 Appendix C. Examples of Registration Forms . . . . . . . . . . . 68 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 70 104 Intellectual Property and Copyright Statements . . . . . . . . . . 71 106 1. Introduction 108 Human beings on our planet have, past and present, used a number of 109 languages. There are many reasons why one would want to identify the 110 language used when presenting or requesting information. 112 A user's language preferences often need to be identified so that 113 appropriate processing can be applied. For example, the user's 114 language preferences in a Web browser can be used to select Web pages 115 appropriately. Language preferences can also be used to select among 116 tools (such as dictionaries) to assist in the processing or 117 understanding of content in different languages. 119 In addition, knowledge about the particular language used by some 120 piece of information content might be useful or even required by some 121 types of processing; for example, spell-checking, computer- 122 synthesized speech, Braille transcription, or high-quality print 123 renderings. 125 One means of indicating the language used is by labeling the 126 information content with an identifier or "tag". These tags can be 127 used to specify user preferences when selecting information content, 128 or for labeling additional attributes of content and associated 129 resources. 131 Tags can also be used to indicate additional language attributes of 132 content. For example, indicating specific information about the 133 dialect, writing system, or orthography used in a document or 134 resource may enable the user to obtain information in a form that 135 they can understand, or it can be important in processing or 136 rendering the given content into an appropriate form or style. 138 This document specifies a particular identifier mechanism (the 139 language tag) and a registration function for values to be used to 140 form tags. It also defines a mechanism for private use values and 141 future extension. 143 This document replaces [RFC4646], which replaced [RFC3066] and its 144 predecessor [RFC1766]. For a list of changes in this document, see 145 Section 8. 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 149 document are to be interpreted as described in [RFC2119]. 151 2. The Language Tag 153 Language tags are used to help identify languages, whether spoken, 154 written, signed, or otherwise signaled, for the purpose of 155 communication. This includes constructed and artificial languages, 156 but excludes languages not intended primarily for human 157 communication, such as programming languages. 159 2.1. Syntax 161 The language tag is composed of one or more parts, known as 162 "subtags". Each subtag consists of a sequence of alphanumeric 163 characters. Subtags are distinguished and separated from one another 164 by a hyphen ("-", ABNF [RFC4234] %x2D). A language tag consists of a 165 "primary language" subtag and a (possibly empty) series of subsequent 166 subtags, each of which refines or narrows the range of languages 167 identified by the overall tag. 169 Usually, each type of subtag is distinguished by length, position in 170 the tag, and content: subtags can be recognized solely by these 171 features. The only exception to this is a fixed list of 172 grandfathered tags registered under RFC 3066 [RFC3066]. This makes 173 it possible to construct a parser that can extract and assign some 174 semantic information to the subtags, even if the specific subtag 175 values are not recognized. Thus, a parser need not have an up-to- 176 date copy (or any copy at all) of the subtag registry to perform most 177 searching and matching operations. 179 The syntax of the language tag in ABNF [RFC4234] is: 181 Language-Tag = langtag 182 / privateuse ; private use tag 183 / irregular ; tags grandfathered by rule 185 langtag = (language 186 ["-" script] 187 ["-" region] 188 *("-" variant) 189 *("-" extension) 190 ["-" privateuse]) 192 language = (2*3ALPHA [ extlang ]) ; shortest ISO 639 code 193 / 4ALPHA ; reserved for future use 194 / 5*8ALPHA ; registered language subtag 196 extlang = *3("-" 3ALPHA) ; permanently reserved 198 script = 4ALPHA ; ISO 15924 code 200 region = 2ALPHA ; ISO 3166 code 201 / 3DIGIT ; UN M.49 code 203 variant = 5*8alphanum ; registered variants 204 / (DIGIT 3alphanum) 206 extension = singleton 1*("-" (2*8alphanum)) 208 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 209 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 210 ; Single alphanumerics 211 ; "x" is reserved for private use 213 privateuse = "x" 1*("-" (1*8alphanum)) 215 irregular = "en-GB-oed" / "i-ami" / "i-bnn" / "i-default" 216 / "i-enochian" / "i-hak" / "i-klingon" / "i-lux" 217 / "i-mingo" / "i-navajo" / "i-pwn" / "i-tao" 218 / "i-tay" / "i-tsu" / "sgn-BE-fr" / "sgn-BE-nl" 219 / "sgn-CH-de" 221 alphanum = (ALPHA / DIGIT) ; letters and numbers 223 Figure 1: Language Tag ABNF 225 All subtags have a maximum length of eight characters and whitespace 226 is not permitted in a language tag. There is a subtlety in the ABNF 227 production 'variant': variants starting with a digit MAY be four 228 characters long, while those starting with a letter MUST be at least 229 five characters long. For examples of language tags, see Appendix B. 231 Note Well: the ABNF syntax does not distinguish between upper and 232 lowercase. The appearance of upper and lowercase letters in the 233 varous ABNF productions above do not affect how implementations 234 interpret tags. That is, the tag "I-AMI" matches the item "i-ami" in 235 the 'irregular' production. At all times, the tags and their 236 subtags, including private use and extensions, are to be treated as 237 case insensitive: there exist conventions for the capitalization of 238 some of the subtags, but these MUST NOT be taken to carry meaning. 240 For example: 242 o [ISO639-1] recommends that language codes be written in lowercase 243 ('mn' Mongolian). 245 o [ISO3166-1] recommends that country codes be capitalized ('MN' 246 Mongolia). 248 o [ISO15924] recommends that script codes use lowercase with the 249 initial letter capitalized ('Cyrl' Cyrillic). 251 However, in the tags defined by this document, the uppercase US-ASCII 252 letters in the range 'A' through 'Z' are considered equivalent and 253 mapped directly to their US-ASCII lowercase equivalents in the range 254 'a' through 'z'. Thus, the tag "mn-Cyrl-MN" is not distinct from 255 "MN-cYRL-mn" or "mN-cYrL-Mn" (or any other combination), and each of 256 these variations conveys the same meaning: Mongolian written in the 257 Cyrillic script as used in Mongolia. 259 Although case distinctions do not carry meaning in language tags, 260 consistent formatting and presentation of the tags will aid users. 261 The format of the tags and subtags in the registry is RECOMMENDED. 262 In this format, all non-initial two-letter subtags are uppercase, all 263 non-initial four-letter subtags are titlecase, and all other subtags 264 are lowercase. 266 Note that although [RFC4234] refers to octets, the language tags 267 described in this document are sequences of characters from the US- 268 ASCII [ISO646] repertoire. Language tags MAY be used in documents 269 and applications that use other encodings, so long as these encompass 270 the US-ASCII repertoire. An example of this would be an XML document 271 that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 273 2.2. Language Subtag Sources and Interpretation 275 The namespace of language tags and their subtags is administered by 276 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 277 the rules in Section 5 of this document. The Language Subtag 278 Registry maintained by IANA is the source for valid subtags: other 279 standards referenced in this section provide the source material for 280 that registry. 282 Terminology used in this document: 284 o Tag or tags refers to a complete language tag, such as 285 "sr-Latn-RS" or "az-Arab-IR". Examples of tags in this document 286 are enclosed in double-quotes ("en-US"). 288 o Subtag refers to a specific section of a tag, delimited by hyphen, 289 such as the subtag 'Hant' in "zh-Hant-CN". Examples of subtags in 290 this document are enclosed in single quotes ('Hant'). 292 o Code or codes refers to values defined in external standards (and 293 which are used as subtags in this document). For example, 'Hant' 294 is an [ISO15924] script code that was used to define the 'Hant' 295 script subtag for use in a language tag. Examples of codes in 296 this document are enclosed in single quotes ('en', 'Hant'). 298 The definitions in this section apply to the various subtags within 299 the language tags defined by this document, excepting those 300 "grandfathered" tags defined in Section 2.2.8. 302 Language tags are designed so that each subtag type has unique length 303 and content restrictions. These make identification of the subtag's 304 type possible, even if the content of the subtag itself is 305 unrecognized. This allows tags to be parsed and processed without 306 reference to the latest version of the underlying standards or the 307 IANA registry and makes the associated exception handling when 308 parsing tags simpler. 310 Subtags in the IANA registry that do not come from an underlying 311 standard can only appear in specific positions in a tag. 312 Specifically, they can only occur as primary language subtags or as 313 variant subtags. 315 Note that sequences of private use and extension subtags MUST occur 316 at the end of the sequence of subtags and MUST NOT be interspersed 317 with subtags defined elsewhere in this document. 319 Single-letter and single-digit subtags are reserved for current or 320 future use. These include the following current uses: 322 o The single-letter subtag 'x' is reserved to introduce a sequence 323 of private use subtags. The interpretation of any private use 324 subtags is defined solely by private agreement and is not defined 325 by the rules in this section or in any standard or registry 326 defined in this document. 328 o All other single-letter subtags are reserved to introduce 329 standardized extension subtag sequences as described in 330 Section 3.7. 332 The single-letter subtag 'i' is used by some grandfathered tags, such 333 as "i-default", where it always appears in the first position and 334 cannot be confused with an extension. 336 2.2.1. Primary Language Subtag 338 The primary language subtag is the first subtag in a language tag 339 (with the exception of private use and certain grandfathered tags) 340 and cannot be omitted. The following rules apply to the primary 341 language subtag: 343 1. All two-character primary language subtags were defined in the 344 IANA registry according to the assignments found in the standard 345 ISO 639 Part 1, "ISO 639-1:2002, Codes for the representation of 346 names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using 347 assignments subsequently made by the ISO 639-1 registration 348 authority (RA) or governing standardization bodies. 350 2. All three-character primary language subtags were defined in the 351 IANA registry according to the assignments found in either ISO 352 639 Part 2, "ISO 639-2:1998 - Codes for the representation of 353 names of languages -- Part 2: Alpha-3 code - edition 1" 354 [ISO639-2], ISO 639 Part 3, "Codes for the representation of 355 names of languages -- Part 3: Alpha-3 code for comprehensive 356 coverage of languages" [ISO639-3], or assignments subsequently 357 made by the relevant ISO 639 registration authorities or 358 governing standardization bodies. 360 3. The subtags in the range 'qaa' through 'qtz' are reserved for 361 private use in language tags. These subtags correspond to codes 362 reserved by ISO 639-2 for private use. These codes MAY be used 363 for non-registered primary language subtags (instead of using 364 private use subtags following 'x-'). Please refer to Section 4.5 365 for more information on private use subtags. 367 4. All four-character language subtags are reserved for possible 368 future standardization. 370 5. All language subtags of 5 to 8 characters in length in the IANA 371 registry were defined via the registration process in Section 3.5 372 and MAY be used to form the primary language subtag. At the time 373 this document was created, there were no examples of this kind of 374 subtag and future registrations of this type will be discouraged: 375 primary languages are strongly RECOMMENDED for registration with 376 ISO 639, and proposals rejected by ISO 639/RA-JAC will be closely 377 scrutinized before they are registered with IANA. 379 6. The single-character subtag 'x' as the primary subtag indicates 380 that the language tag consists solely of subtags whose meaning is 381 defined by private agreement. For example, in the tag "x-fr-CH", 382 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 383 French language or the country of Switzerland (or any other value 384 in the IANA registry) unless there is a private agreement in 385 place to do so. See Section 4.5. 387 7. The single-character subtag 'i' is used by some grandfathered 388 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 389 grandfathered tags have a primary language subtag in their first 390 position.) 392 8. Other values MUST NOT be assigned to the primary subtag except by 393 revision or update of this document. 395 Note: For languages that have both an ISO 639-1 two-character code 396 and a three character code assigned by either ISO 639-2 or ISO 639-3, 397 only the ISO 639-1 two-character code is defined in the IANA 398 registry. 400 Note: For languages that have no ISO 639-1 two-character code and for 401 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 402 (Bibliographic) codes differ, only the Terminology code is defined in 403 the IANA registry. At the time this document was created, all 404 languages that had both kinds of three-character code were also 405 assigned a two-character code; it is expected that future assignments 406 of this nature will not occur. 408 Note: To avoid problems with versioning and subtag choice as 409 experienced during the transition between RFC 1766 and RFC 3066, as 410 well as the canonical nature of subtags defined by this document, the 411 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 412 RA-JAC) has included the following statement in [iso639.prin]: 414 "A language code already in ISO 639-2 at the point of freezing ISO 415 639-1 shall not later be added to ISO 639-1. This is to ensure 416 consistency in usage over time, since users are directed in 417 Internet applications to employ the alpha-3 code when an alpha-2 418 code for that language is not available." 420 In order to avoid instability in the canonical form of tags, if a 421 two-character code is added to ISO 639-1 for a language for which a 422 three-character code was already included in either ISO 639-2 or ISO 423 639-3, the two-character code MUST NOT be registered. See 424 Section 3.4. 426 For example, if some content were tagged with 'haw' (Hawaiian), which 427 currently has no two-character code, the tag would not be invalidated 428 if ISO 639-1 were to assign a two-character code to the Hawaiian 429 language at a later date. 431 Note: An example of independent primary language subtag registration 432 might include: one of the grandfathered IANA registrations is 433 "i-enochian". The subtag 'enochian' could be registered in the IANA 434 registry as a primary language subtag (assuming that ISO 639 does not 435 register this language first), making tags such as "enochian-AQ" and 436 "enochian-Latn" valid. 438 2.2.2. Extended Language Subtags 440 Extended language subtags are permanently reserved. They MUST NOT be 441 registered or used to form language tags (except in grandfathered 442 tags). They were originally created to allow for certain kinds of 443 compatibility mappings which ultimately were not used. 445 2.2.3. Script Subtag 447 Script subtags are used to indicate the script or writing system 448 variations that distinguish the written forms of a language or its 449 dialects. The following rules apply to the script subtags: 451 1. All four-character subtags were defined according to 452 [ISO15924]--"Codes for the representation of the names of 453 scripts": alpha-4 script codes, or subsequently assigned by the 454 ISO 15924 maintenance agency or governing standardization bodies, 455 denoting the script or writing system used in conjunction with 456 this language. 458 2. Script subtags MUST immediately follow the primary language 459 subtag and all extended language subtags and MUST occur before 460 any other type of subtag described below. 462 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 463 use in language tags. These subtags correspond to codes reserved 464 by ISO 15924 for private use. These codes MAY be used for non- 465 registered script values. Please refer to Section 4.5 for more 466 information on private use subtags. 468 4. Script subtags MUST NOT be registered using the process in 469 Section 3.5 of this document. Variant subtags MAY be considered 470 for registration for that purpose. 472 5. There MUST be at most one script subtag in a language tag, and 473 the script subtag SHOULD be omitted when it adds no 474 distinguishing value to the tag or when the primary language 475 subtag's record includes a Suppress-Script field listing the 476 applicable script subtag. 478 Example: "sr-Latn" represents Serbian written using the Latin script. 480 2.2.4. Region Subtag 482 Region subtags are used to indicate linguistic variations associated 483 with or appropriate to a specific country, territory, or region. 484 Typically, a region subtag is used to indicate regional dialects or 485 usage, or region-specific spelling conventions. A region subtag can 486 also be used to indicate that content is expressed in a way that is 487 appropriate for use throughout a region, for instance, Spanish 488 content tailored to be useful throughout Latin America. 490 The following rules apply to the region subtags: 492 1. Region subtags MUST follow any language, extended language, or 493 script subtags and MUST precede all other subtags. 495 2. All two-character subtags following the primary subtag were 496 defined in the IANA registry according to the assignments found 497 in [ISO3166-1] ("Codes for the representation of names of 498 countries and their subdivisions -- Part 1: Country codes") using 499 the list of alpha-2 country codes, or using assignments 500 subsequently made by the ISO 3166 maintenance agency or governing 501 standardization bodies. In addition, the codes that are 502 "exceptionally reserved" (as opposed to "assigned") in ISO 3166-1 503 were also defined in the registry, with the exception of 'UK', 504 which is an exact synonym for the assigned code 'GB'. 506 3. All three-character subtags consisting of digit (numeric) 507 characters following the primary subtag were defined in the IANA 508 registry according to the assignments found in UN Standard 509 Country or Area Codes for Statistical Use [UN_M.49] or 510 assignments subsequently made by the governing standards body. 511 Note that not all of the UN M.49 codes are defined in the IANA 512 registry. The following rules define which codes are entered 513 into the registry as valid subtags: 515 A. UN numeric codes assigned to 'macro-geographical 516 (continental)' or sub-regions MUST be registered in the 517 registry. These codes are not associated with an assigned 518 ISO 3166 alpha-2 code and represent supra-national areas, 519 usually covering more than one nation, state, province, or 520 territory. 522 B. UN numeric codes for 'economic groupings' or 'other 523 groupings' MUST NOT be registered in the IANA registry and 524 MUST NOT be used to form language tags. 526 C. UN numeric codes for countries or areas with ambiguous ISO 527 3166 alpha-2 codes, when entered into the registry, MUST be 528 defined according to the rules in Section 3.4 and MUST be 529 used to form language tags that represent the country or 530 region for which they are defined. 532 D. UN numeric codes for countries or areas for which there is an 533 associated ISO 3166 alpha-2 code in the registry MUST NOT be 534 entered into the registry and MUST NOT be used to form 535 language tags. Note that the ISO 3166-based subtag in the 536 registry MUST actually be associated with the UN M.49 code in 537 question. 539 E. UN numeric codes and ISO 3166 alpha-2 codes for countries or 540 areas listed as eligible for registration in [RFC4645] but 541 not presently registered MAY be entered into the IANA 542 registry via the process described in Section 3.5. Once 543 registered, these codes MAY be used to form language tags. 545 F. All other UN numeric codes for countries or areas that do not 546 have an associated ISO 3166 alpha-2 code MUST NOT be entered 547 into the registry and MUST NOT be used to form language tags. 548 For more information about these codes, see Section 3.4. 550 4. Note: The alphanumeric codes in Appendix X of the UN document 551 MUST NOT be entered into the registry and MUST NOT be used to 552 form language tags. (At the time this document was created, 553 these values matched the ISO 3166 alpha-2 codes.) 555 5. There MUST be at most one region subtag in a language tag and the 556 region subtag MAY be omitted, as when it adds no distinguishing 557 value to the tag. 559 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 560 reserved for private use in language tags. These subtags 561 correspond to codes reserved by ISO 3166 for private use. These 562 codes MAY be used for private use region subtags (instead of 563 using a private use subtag sequence). Please refer to 564 Section 4.5 for more information on private use subtags. 566 "de-CH" represents German ('de') as used in Switzerland ('CH'). 568 "sr-Latn-RS" represents Serbian ('sr') written using Latin script 569 ('Latn') as used in Serbia ('RS'). 571 "es-419" represents Spanish ('es') appropriate to the UN-defined 572 Latin America and Caribbean region ('419'). 574 2.2.5. Variant Subtags 576 Variant subtags are used to indicate additional, well-recognized 577 variations that define a language or its dialects that are not 578 covered by other available subtags. The following rules apply to the 579 variant subtags: 581 1. Variant subtags are not associated with any external standard. 582 Variant subtags and their meanings are defined by the 583 registration process defined in Section 3.5. 585 2. Variant subtags MUST follow all of the other defined subtags, but 586 precede any extension or private use subtag sequences. 588 3. More than one variant MAY be used to form the language tag. 590 4. Variant subtags MUST be registered with IANA according to the 591 rules in Section 3.5 of this document before being used to form 592 language tags. In order to distinguish variants from other types 593 of subtags, registrations MUST meet the following length and 594 content restrictions: 596 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 597 at least five characters long. 599 2. Variant subtags that begin with a digit (0-9) MUST be at 600 least four characters long. 602 Variant subtag records in the language subtag registry MAY include 603 one or more 'Prefix' fields. The 'Prefix' indicates the language tag 604 or tags that would make a suitable prefix (with other subtags, as 605 appropriate) in forming a language tag with the variant. That is, 606 each of the subtags in the prefix SHOULD appear before the variant. 607 For example, the subtag 'nedis' has a Prefix of "sl", making it 608 suitable to form language tags such as "sl-nedis" and "sl-IT-nedis", 609 but not suitable for use in a tag such as "zh-nedis" or "it-IT- 610 nedis". 612 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 614 "de-CH-1996" represents German as used in Switzerland and as written 615 using the spelling reform beginning in the year 1996 C.E. 617 Most variants that share a prefix are mutually exclusive. For 618 example, the German orthographic variations '1996' and '1901' SHOULD 619 NOT be used in the same tag, as they represent the dates of different 620 spelling reforms. A variant that can meaningfully be used in 621 combination with another variant SHOULD include a 'Prefix' field in 622 its registry record that lists that other variant. For example, if 623 another German variant 'example' were created that made sense to use 624 with '1996', then 'example' should include two Prefix fields: "de" 625 and "de-1996". 627 2.2.6. Extension Subtags 629 Extensions provide a mechanism for extending language tags for use in 630 various applications. See Section 3.7. The following rules apply to 631 extensions: 633 1. Extension subtags are separated from the other subtags defined 634 in this document by a single-character subtag ("singleton"). 635 The singleton MUST be one allocated to a registration authority 636 via the mechanism described in Section 3.7 and MUST NOT be the 637 letter 'x', which is reserved for private use subtag sequences. 639 2. Note: Private use subtag sequences starting with the singleton 640 subtag 'x' are described in Section 2.2.7 below. 642 3. An extension MUST follow at least a primary language subtag. 643 That is, a language tag cannot begin with an extension. 644 Extensions extend language tags, they do not override or replace 645 them. For example, "a-value" is not a well-formed language tag, 646 while "de-a-value" is. 648 4. Each singleton subtag MUST appear at most one time in each tag 649 (other than as a private use subtag). That is, singleton 650 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 651 ccc" is invalid because the subtag 'a' appears twice. Note that 652 the tag "en-a-bbb-x-a-ccc" is valid because the second 653 appearance of the singleton 'a' is in a private use sequence. 655 5. Extension subtags MUST meet all of the requirements for the 656 content and format of subtags defined in this document. 658 6. Extension subtags MUST meet whatever requirements are set by the 659 document that defines their singleton prefix and whatever 660 requirements are provided by the maintaining authority. 662 7. Each extension subtag MUST be from two to eight characters long 663 and consist solely of letters or digits, with each subtag 664 separated by a single '-'. 666 8. Each singleton MUST be followed by at least one extension 667 subtag. For example, the tag "tlh-a-b-foo" is invalid because 668 the first singleton 'a' is followed immediately by another 669 singleton 'b'. 671 9. Extension subtags MUST follow all language, extended language, 672 script, region, and variant subtags in a tag. 674 10. All subtags following the singleton and before another singleton 675 are part of the extension. Example: In the tag "fr-a-Latn", the 676 subtag 'Latn' does not represent the script subtag 'Latn' 677 defined in the IANA Language Subtag Registry. Its meaning is 678 defined by the extension 'a'. 680 11. In the event that more than one extension appears in a single 681 tag, the tag SHOULD be canonicalized as described in 682 Section 4.4. 684 For example, if the prefix singleton 'r' and the shown subtags were 685 defined, then the following tag would be a valid example: "en-Latn- 686 GB-boont-r-extended-sequence-x-private" 688 2.2.7. Private Use Subtags 690 Private use subtags are used to indicate distinctions in language 691 important in a given context by private agreement. The following 692 rules apply to private use subtags: 694 1. Private use subtags are separated from the other subtags defined 695 in this document by the reserved single-character subtag 'x'. 697 2. Private use subtags MUST conform to the format and content 698 constraints defined in the ABNF for all subtags. 700 3. Private use subtags MUST follow all language, extended language, 701 script, region, variant, and extension subtags in the tag. 702 Another way of saying this is that all subtags following the 703 singleton 'x' MUST be considered private use. Example: The 704 subtag 'US' in the tag "en-x-US" is a private use subtag. 706 4. A tag MAY consist entirely of private use subtags. 708 5. No source is defined for private use subtags. Use of private use 709 subtags is by private agreement only. 711 6. Private use subtags are NOT RECOMMENDED where alternatives exist 712 or for general interchange. See Section 4.5 for more information 713 on private use subtag choice. 715 For example: Users who wished to utilize codes from the Ethnologue 716 publication of SIL International for language identification might 717 agree to exchange tags such as "az-Arab-x-AZE-derbend". This example 718 contains two private use subtags. The first is 'AZE' and the second 719 is 'derbend'. 721 2.2.8. Grandfathered Registrations 723 Prior to RFC 4646, whole language tags were registered according to 724 the rules in RFC 1766 and/or RFC 3066. These registered tags 725 maintain their validity. Of those tags, those that were made 726 obsolete or redundant by the advent of RFC 4646, by this document, or 727 by subsequent registration of subtags are maintained in the registry 728 in records as "redundant" records. Those tags that do not match the 729 'langtag' production in the ABNF in this document or that contain 730 subtags that do not individually appear in the registry are 731 maintained in the registry in records of the "grandfathered" type. 733 Grandfathered tags contain one or more subtags that are not defined 734 in the Language Subtag Registry (see Section 3). Redundant tags 735 consist entirely of subtags defined above and whose independent 736 registration was superseded by [RFC4646]. For more information see 737 Section 3.8. 739 Some grandfathered tags are "regular" in that they match the 740 'langtag' production in Figure 1. In some cases, these tags could 741 become redundant if their (current unregistered) subtags were to be 742 registered (as variants, for example). In other cases, although the 743 subtags match the language tag pattern, the meaning assigned to the 744 various subtags is prohibited by rules elsewhere in this document. 745 Those tags can never become redundant. 747 The remaining grandfathered tags are "irregular" and do not match the 748 'langtag' production. These are listed in the 'irregular' production 749 in Figure 1. These grandfathered tags can never become redundant. 750 Many of these tags have been superseded by other registrations: their 751 record contains a Preferred-Value field that really ought to be used 752 to form language tags representing that value. 754 2.2.9. Classes of Conformance 756 Implementations sometimes need to describe their capabilities with 757 regard to the rules and practices described in this document. Tags 758 can be checked or verified in a number of ways, but two particular 759 classes of tag conformance are formally defined here. 761 A tag is considered "well-formed" if it conforms to the ABNF 762 (Section 2.1). Note that irregular grandfathered tags are now listed 763 in the 'irregular' production. 765 Although a tag is considered "well-formed" if it contains a sequence 766 matching the permanently reserved 'extlang' production, non- 767 grandfathered tags that match this pattern are never valid and are 768 ill-considered. 770 A tag is considered "valid" if it well-formed and it also satisfies 771 these conditions: 773 o The tag is either a grandfathered tag, or all of its language, 774 extended language, script, region, and variant subtags appear in 775 the IANA language subtag registry as of the particular registry 776 date. 778 o There are no duplicate singleton (extension) subtags and no 779 duplicate variant subtags. 781 o For each subtag that has a 'Prefix' field in the registry, the 782 Prefix matches the language tag using Extended Filtering 783 [RFC4647]. That is, each subtag in the Prefix is present in the 784 tag and in the same order. Furthermore, all of the Prefix's 785 subtags MUST appear before the subtag. For example, the Prefix 786 "zh-TW" matches the tag "zh-Hant-TW". 788 Note that a tag's validity depends on the date of the registry used 789 to validate the tag. A more-recent copy of the registry might 790 contain a subtag that an older version does not. 792 A tag is considered "valid" for a given extension (Section 3.7) (as 793 of a particular version, revision, and date) if it meets the criteria 794 for "valid" above and also satisfies this condition: 796 Each subtag used in the extension part of the tag is valid 797 according to the extension. 799 3. Registry Format and Maintenance 801 This section defines the Language Subtag Registry and the maintenance 802 and update procedures associated with it, as well as a registry for 803 extensions to language tags (Section 3.7). 805 The Language Subtag Registry contains a comprehensive list of all of 806 the subtags valid in language tags. This allows implementers a 807 straightforward and reliable way to validate language tags. The 808 Language Subtag Registry will be maintained so that, except for 809 extension subtags, it is possible to validate all of the subtags that 810 appear in a language tag under the provisions of this document or its 811 revisions or successors. In addition, the meaning of the various 812 subtags will be unambiguous and stable over time. (The meaning of 813 private use subtags, of course, is not defined by the IANA registry.) 815 3.1. Format of the IANA Language Subtag Registry 817 The IANA Language Subtag Registry ("the registry") is a machine- 818 readable file in the format described in this section, plus copies of 819 the registration forms approved in accordance with the process 820 described in Section 3.5. The existing registration forms for 821 grandfathered and redundant tags taken from RFC 3066 will be 822 maintained as part of the obsolete RFC 3066 registry. The remaining 823 set of subtags created by either [RFC4645] or [registry-update] will 824 not have registration forms created for them. 826 3.1.1. File Format 828 The registry consists of a series of records stored in the record-jar 829 format (described in [record-jar]). Each record, in turn, consists 830 of a series of fields that describe the various subtags and tags. 831 The registry is a Unicode [Unicode] text file, using the UTF-8 832 [RFC3629] character encoding. 834 Each field can be considered a single, logical line of Unicode 835 [Unicode] characters, comprising a field-name and a field-body 836 separated by a COLON character (%x3A). Each field is terminated by 837 the newline sequence CRLF. The text in each field MUST be in Unicode 838 Normalization Form C (NFC). 840 A collection of fields forms a 'record'. Records are separated by 841 lines containing only the sequence "%%" (%x25.25). 843 Although fields are logically a single line of text, each line of 844 text in the file format is limited to 72 bytes in length. To 845 accommodate this, the field-body can be split into a multiple-line 846 representation; this is called "folding". Folding is always done on 847 Unicode code point boundaries (never in the middle of a multibyte 848 UTF-8 sequence) and MUST NOT occur just prior to a combining mark. 850 Although the file format uses the UTF-8 encoding, unless otherwise 851 indicated, fields are restricted to the printable characters from the 852 US-ASCII [ISO646] repertoire. 854 The format of the registry is described by the following ABNF (per 855 [RFC4234]): 857 registry = record *("%%" CRLF record) 858 record = 1*( field-name *SP ":" *SP field-body CRLF ) 859 field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] 860 field-body = *([[*SP CRLF] 1*SP] 1*CHARS) 861 CHARS = (%x21-10FFFF) ; Unicode code points 863 Figure 2: Registry Format ABNF 865 The sequence '..' (%x2E.2E) in a field-body denotes a range of 866 values. Such a range represents all subtags of the same length that 867 are in alphabetic or numeric order within that range, including the 868 values explicitly mentioned. For example 'a..c' denotes the values 869 'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and 870 '13'. 872 All fields whose field-body contains a date value use the "full-date" 873 format specified in [RFC3339]. For example: "2004-06-28" represents 874 June 28, 2004, in the Gregorian calendar. 876 3.1.2. Record Definitions 878 There are three types of records in the registry: "File-Date", 879 "Subtag", and "Tag" records. 881 The first record in the registry is a "File-Date" record. This 882 record contains the single field whose field-name is "File-Date" (see 883 Figure 2). The field-body of this record contains the last 884 modification date of this copy of the registry, making it possible to 885 compare different versions of the registry. The registry on the IANA 886 website is the most current. Versions with an older date than that 887 one are not up-to-date. 889 File-Date: 2004-06-28 890 %% 892 Figure 3: Example of the File-Date Record 894 Subsequent records represent either subtags or tags in the registry. 896 "Subtag" records contain a field with a field-name of "Subtag", 897 while, unsurprisingly, "Tag" records contain a field with a field- 898 name of "Tag". Each of the fields in each record MUST occur no more 899 than once, unless otherwise noted below. Each record MUST contain 900 the following fields: 902 o 'Type' 904 * Type's field-body MUST consist of one of the following strings: 905 "language", "script", "region", "variant", "grandfathered", and 906 "redundant" and denotes the type of tag or subtag. 908 o Either 'Subtag' or 'Tag' 910 * Subtag's field-body contains the subtag being defined. This 911 field MUST only appear in records of whose 'Type' has one of 912 these values: "language", "script", "region", or "variant". 914 * Tag's field-body contains a complete language tag. This field 915 MUST only appear in records whose 'Type' has one of these 916 values: "grandfathered" or "redundant". Note that the field- 917 body will always follow the 'grandfathered' production in the 918 ABNF in Section 2.1 920 o Description 922 * Description's field-body contains a non-normative description 923 of the subtag or tag. 925 o Added 927 * Added's field-body contains the date the record was added to 928 the registry. 930 Each record MAY also contain the following fields: 932 o Preferred-Value 934 * For fields of type 'script', 'region', and 'variant', 935 'Preferred-Value' contains the subtag of the same 'Type' that 936 is preferred for forming the language tag. 938 * For fields of type 'language', 'Preferred-Value' contains the 939 primary language subtag that is preferred when forming the 940 language tag. 942 * For fields of type 'grandfathered' and 'redundant', a canonical 943 mapping to a complete language tag. 945 o Deprecated 947 * The field-body of the Deprecated field contains the date the 948 record was deprecated. 950 o Prefix 952 * Prefix's field-body contains a language tag with which this 953 subtag MAY be used to form a new language tag, perhaps with 954 other subtags as well. The Prefix's subtags appear before the 955 subtag. This field MUST only appear in records whose 'Type' 956 field-body is 'variant'. For example, the 'Prefix' for the 957 variant 'nedis' is 'sl', meaning that the tags "sl-nedis" and 958 "sl-IT-nedis" might be appropriate while the tag "is-nedis" is 959 not. 961 o Comments 963 * Comments contains additional information about the subtag, as 964 deemed appropriate for understanding the registry and 965 implementing language tags using the subtag or tag. 967 o Suppress-Script 969 * Suppress-Script contains a script subtag that SHOULD NOT be 970 used to form language tags with the associated primary language 971 subtag. This field MUST only appear in records whose 'Type' 972 field-body is 'language'. See Section 4.1. 974 o Macrolanguage 976 * Macrolanguage contains a primary language subtag defined by ISO 977 639 as a "macrolanguage" that encompasses this language subtag. 978 This field MUST only appear in records whose 'Type' field-body 979 is 'language'. 981 Future versions of this document might add additional fields to the 982 registry, so implementations SHOULD ignore fields found in the 983 registry that are not defined in this document. 985 3.1.3. Subtag and Tag Fields 987 The 'Subtag' field MUST use lowercase letters to form the subtag, 988 with two exceptions. Subtags whose 'Type' field is 'script' (in 989 other words, subtags defined by ISO 15924) MUST use titlecase. 990 Subtags whose 'Type' field is 'region' (in other words, the non- 991 numeric region subtags defined by ISO 3166) MUST use uppercase. 992 These exceptions mirror the use of case in the underlying standards. 994 Each subtag in the tags contained in a 'Tag' field MUST be formatted 995 using the rules in the preceeding paragraph. That is, all subtags 996 are lowercase except for subtags that represent script or region 997 codes. 999 3.1.4. Description Field 1001 The field 'Description' contains a description of the tag or subtag 1002 in the record. The 'Description' field MAY appear more than once per 1003 record, that is, there can be multiple descriptions for a given 1004 record. The 'Description' field MAY include the full range of 1005 Unicode characters. At least one of the 'Description' fields MUST be 1006 written or transcribed into the Latin script; additional 1007 'Description' fields MAY also include a description in a non-Latin 1008 script. Each 'Description' field MUST be unique, both within the 1009 record in which it appears and for the collection of records of the 1010 same type. Moreover, formatting variations of the same description 1011 MUST NOT occur in that specific record or in any other record of the 1012 same type. For example, while the ISO 639-1 code 'fy' contains both 1013 the descriptions "Western Frisian" and "Frisian, Western", only one 1014 of these descriptions appears in the registry. 1016 The 'Description' field is used for identification purposes and 1017 SHOULD NOT be taken to represent the actual native name of the 1018 language or variation or to be in any particular language. 1020 For records taken from a source standard (such as ISO 639 or ISO 1021 3166), the 'Description' value(s) SHOULD also be taken from the 1022 source standard. Multiple descriptions in the source standard MUST 1023 be split into separate 'Description' fields. The source standard's 1024 descriptions MAY be edited, either prior to insertion or via the 1025 registration process. For fields of type 'language', the first 1026 'Description' field appearing in the Registry corresponds to the 1027 Reference Name assigned by ISO 639-3. This helps facilitate cross- 1028 referencing between ISO 639 and the registry. 1030 When creating or updating a record due to the action of one of the 1031 source standards, the Language Subtag Reviewer SHOULD remove 1032 duplicate or redundant descriptions and MAY edit descriptions to 1033 correct irregularities in formatting (such as misspellings, 1034 inappropriate apostrophes or other punctuation, or excessive or 1035 missing spaces) prior to submitting the proposed record to the ietf- 1036 languages list. 1038 Note: Descriptions in registry entries that correspond to ISO 639, 1039 ISO 15924, ISO 3166, or UN M.49 codes are intended only to indicate 1040 the meaning of that identifier as defined in the source standard at 1041 the time it was added to the registry. The description does not 1042 replace the content of the source standard itself. The descriptions 1043 are not intended to be the English localized names for the subtags. 1044 Localization or translation of language tag and subtag descriptions 1045 is out of scope of this document. 1047 3.1.5. Deprecated Field 1049 The field 'Deprecated' MAY be added to any record via the maintenance 1050 process described in Section 3.3 or via the registration process 1051 described in Section 3.5. Usually, the addition of a 'Deprecated' 1052 field is due to the action of one of the standards bodies, such as 1053 ISO 3166, withdrawing a code. In some historical cases, it might not 1054 have been possible to reconstruct the original deprecation date. For 1055 these cases, an approximate date appears in the registry. Although 1056 valid in language tags, subtags and tags with a 'Deprecated' field 1057 are deprecated and validating processors SHOULD NOT generate these 1058 subtags. Note that a record that contains a 'Deprecated' field and 1059 no corresponding 'Preferred-Value' field has no replacement mapping. 1061 3.1.6. Preferred-Value Field 1063 The field 'Preferred-Value' contains a mapping between the record in 1064 which it appears and another tag or subtag. The value in this field 1065 is strongly RECOMMENDED as the best choice to represent the value of 1066 this record when selecting a language tag. These values form three 1067 groups: 1069 1. ISO 639 language codes that were later withdrawn in favor of 1070 other codes. These values are mostly a historical curiosity. 1072 2. ISO 3166 region codes that have been withdrawn in favor of a new 1073 code. This sometimes happens when a country changes its name or 1074 administration in such a way that warrants a new region code. 1076 3. Grandfathered or redundant tags from RFC 3066. In many cases, 1077 these tags have become obsolete because the values they represent 1078 were later encoded by ISO 639. 1080 Records that contain a 'Preferred-Value' field MUST also have a 1081 'Deprecated' field. This field contains a date of deprecation. 1082 Thus, a language tag processor can use the registry to construct the 1083 valid, non-deprecated set of subtags for a given date. In addition, 1084 for any given tag, a processor can construct the set of valid 1085 language tags that correspond to that tag for all dates up to the 1086 date of the registry. The ability to do these mappings MAY be 1087 beneficial to applications that are matching, selecting, for 1088 filtering content based on its language tags. 1090 Note that 'Preferred-Value' mappings in records of type 'region' 1091 sometimes do not represent exactly the same meaning as the original 1092 value. There are many reasons for a country code to be changed, and 1093 the effect this has on the formation of language tags will depend on 1094 the nature of the change in question. 1096 In particular, the 'Preferred-Value' field does not imply retagging 1097 content that uses the affected subtag. 1099 The field 'Preferred-Value' MUST NOT be modified once created in the 1100 registry. The field MAY be added to records according to the rules 1101 in Section 3.3. 1103 The 'Preferred-Value' field in records of type "grandfathered" and 1104 "redundant" contains whole language tags that are strongly 1105 RECOMMENDED for use in place of the record's value. In many cases, 1106 the mappings were created by deprecation of the tags during the 1107 period before this document was adopted. For example, the tag "no- 1108 nyn" was deprecated in favor of the ISO 639-1-defined language code 1109 'nn'. 1111 3.1.7. Prefix Field 1113 The 'Prefix' field contains an extended language range whose subtags 1114 are appropriate to use with this subtag: each of the subtags in one 1115 of the subtag's Prefix fields MUST appear before the variant in a 1116 valid tag. For example, the variant subtag '1996' has a 'Prefix' 1117 field of "de". This means that tags starting with the sequence "de-" 1118 are appropriate with this subtag, so "de-Latg-1996" and "de-CH-1996" 1119 are both acceptable, while the tag "fr-1996" is an inappropriate 1120 choice. 1122 The field of type 'Prefix' MUST NOT be removed from any record. The 1123 field-body for this type of field MAY be modified, but only if the 1124 modification broadens the meaning of the subtag. That is, the field- 1125 body can be replaced only by a prefix a prefix of itself. For 1126 example, the Prefix "be-Latn" (Belarusian, Latin script) could be 1127 replaced by the Prefix "be" (Belarusian) but not by the Prefix "ru- 1128 Latn" (Russian, Latin script). 1130 Records of type 'variant' MAY have more than one field of type 1131 'Prefix'. Additional fields of this type MAY be added to a 'variant' 1132 record via the registration process. 1134 The field-body of the 'Prefix' field MUST NOT conflict with any 1135 'Prefix' already registered for a given record. Such a conflict 1136 would occur when when no valid tag could be constructed that would 1137 contain the prefix, such as when when two subtags each have a 1138 'Prefix' that contains the other subtag. For example, suppose that 1139 the subtag 'avariant' has the prefix "es-bvariant". Then the subtag 1140 'bvariant' cannot given the prefix 'avariant', for that would require 1141 a tag of the form "es-avariant-bvariant-avariant", which would not be 1142 valid. 1144 3.1.8. Suppress-Script Field 1146 The field 'Suppress-Script' contains a script subtag (whose record 1147 appears in the registry). The field 'Suppress-Script' MUST only 1148 appear in records whose 'Type' field-body is 'language'. This field 1149 MUST NOT appear more than one time in a record. This field indicates 1150 a script used to write the overwhelming majority of documents for the 1151 given language. This script code therefore adds no distinguishing 1152 information to a language tag. This helps ensure greater 1153 compatibility between the language tags generated according to the 1154 rules in this document and language tags and tag processors or 1155 consumers based on RFC 3066 by indicating that the script subtag 1156 SHOULD NOT be used for most documents in that language. For example, 1157 virtually all Icelandic documents are written in the Latin script, 1158 making the subtag 'Latn' redundant in the tag "is-Latn". 1160 Many language subtag records do not have a Suppress-Script field. 1161 The lack of a Suppress-Script might indicate that the language is 1162 customarily written in more than one script or that the language is 1163 not customarily written at all. It might also mean that sufficient 1164 information was not available when the record was created and thus 1165 remains a candidate for future registration. 1167 3.1.9. Macrolanguage Field 1169 The Macrolanguage field contains a primary language subtag that 1170 encompasses this subtag's language. That is, the language subtag 1171 whose record this field appears in is sometimes considered to be a 1172 sub-language of the Macrolanguage. Macrolanguage values are defined 1173 by ISO 639-3 and the exact nature of the relationship between the 1174 encompassed and encompassing languages varies on a case-by-case 1175 basis. 1177 This field can be useful to applications or users when selecting 1178 language tags or as additional metadata useful in matching. The 1179 Macrolanguage field can only occur in records of type 'language'. 1180 Only values assigned by ISO 639-3 will be considered for inclusion. 1181 Macrolanguage fields MAY be added or removed via the normal 1182 registration process whenever ISO 639-3 defines new values or 1183 withdraws old values. Macrolanguages are informational, and MAY be 1184 removed or changed if ISO 639-3 changes the values. 1186 For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' 1187 (Norwegian Nynorsk) each have a Macrolanguage entry of 'no' 1188 (Norwegian). For more information see Section 4.1. 1190 3.1.10. Comments Field 1192 The field 'Comments' conveys additional information about the record 1193 and MAY appear more than once per record. The field-body MAY include 1194 the full range of Unicode characters and is not restricted to any 1195 particular script. This field MAY be inserted or changed via the 1196 registration process and no guarantee of stability is provided. The 1197 content of this field is not restricted, except by the need to 1198 register the information, the suitability of the request, and by 1199 reasonable practical size limitations. 1201 3.2. Language Subtag Reviewer 1203 The Language Subtag Reviewer moderates the ietf-languages mailing 1204 list, responds to requests for registration, and performs the other 1205 registry maintenance duties described in Section 3.3. Only the 1206 Language Subtag Reviewer is permitted to request IANA to change, 1207 update, or add records to the Language Subtag Registry. The Language 1208 Subtag Reviewer MAY delegate list moderation and other clerical 1209 duties as needed. 1211 The Language Subtag Reviewer is appointed by the IESG for an 1212 indefinite term, subject to removal or replacement at the IESG's 1213 discretion. The IESG will solicit nominees for the position (upon 1214 adoption of this document or upon a vacancy) and then solicit 1215 feedback on the nominees' qualifications. Qualified candidates 1216 should be familiar with BCP 47 and its requirements; be willing to 1217 fairly, responsively, and judiciously administer the registration 1218 process; and be suitably informed about the issues of language 1219 identification so that they can draw upon and assess the claim and 1220 contributions of language experts and subtag requesters. 1222 The subsequent performance or decisions of the Language Subtag 1223 Reviewer MAY be appealed to the IESG under the same rules as other 1224 IETF decisions (see [RFC2026]). The IESG can reverse or overturn the 1225 decision of the Language Subtag Reviewer, provide guidance, or take 1226 other appropriate actions. 1228 3.3. Maintenance of the Registry 1230 Maintenance of the registry requires that as codes are assigned or 1231 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1232 Subtag Reviewer MUST evaluate each change and determine the 1233 appropriate course of action according to the rules in this document. 1235 Such updates follow the registration process described in 1236 Section 3.5. Usually the Language Subtag Reviewer will start the 1237 process for the new or updated record by filling in the registration 1238 form and submitting it. If a change to one of these standards takes 1239 place and the Language Subtag Reviewer does not do this in a timely 1240 manner, then any interested party MAY submit the form. Thereafter 1241 the registration process continues normally. 1243 The Language Subtag Reviewer MUST ensure that new subtags meet the 1244 requirements elsewhere in this document (and most especially in 1245 Section 3.4) or submit an appropriate registration form for an 1246 alternate subtag as described in that section. Each individual 1247 subtag affected by a change MUST be sent to the ietf-languages list 1248 with its own registration form and in a separate message. 1250 3.4. Stability of IANA Registry Entries 1252 The stability of entries and their meaning in the registry is 1253 critical to the long-term stability of language tags. The rules in 1254 this section guarantee that a specific language tag's meaning is 1255 stable over time and will not change. 1257 These rules specifically deal with how changes to codes (including 1258 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1259 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1260 Subtag Registry. Assignments to the IANA Language Subtag Registry 1261 MUST follow the following stability rules: 1263 1. Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1264 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1265 guaranteed to be stable over time. 1267 2. Values in the 'Description' field MUST NOT be changed in a way 1268 that would invalidate previously-existing tags. They MAY be 1269 broadened somewhat in scope, changed to add information, or 1270 adapted to the most common modern usage. For example, countries 1271 occasionally change their official names; a historical example 1272 of this would be "Upper Volta" changing to "Burkina Faso". 1274 3. Values in the field 'Prefix' MAY be added to records of type 1275 'variant' via the registration process. If a prefix is added to 1276 a variant record, 'Comment' fields SHOULD be used to explain 1277 different usages with the various prefixes. 1279 4. Values in the field 'Prefix' in records of type 'variant' MAY be 1280 modified, so long as the modifications broaden the set of 1281 prefixes. That is, a prefix MAY be replaced by one of its own 1282 prefixes. For example, the prefix "en-US" could be replaced by 1283 "en", but not by the prefixes "en-Latn", "fr", or "en-US-boont". 1284 If one of those prefixes were needed, a new Prefix SHOULD be 1285 registered. 1287 5. Values in the field 'Prefix' MUST NOT be removed. 1289 6. The field 'Comments' MAY be added, changed, modified, or removed 1290 via the registration process or any of the processes or 1291 considerations described in this section. 1293 7. The field 'Suppress-Script' MAY be added or removed via the 1294 registration process. 1296 8. The field 'Macrolanguage' MAY be added or removed via the 1297 registration process, but only in response to changes made by 1298 ISO 639. The Macrolanguage field appears whenever a language 1299 has a corresponding Macrolanguage in ISO 639. That is, the 1300 macrolanguage fields in the registry exactly match those of ISO 1301 639. No other macrolanguage mappings will be considered for 1302 registration. 1304 9. Codes assigned by ISO 639-1 that do not conflict with existing 1305 two-letter primary language subtags and which have no 1306 corresponding three-letter primary or extended language subtags 1307 defined in the registry are entered into the IANA registry as 1308 new records of type 'language'. 1310 10. Codes assigned by ISO 639-2 that do not conflict with existing 1311 three-letter primary or extended language subtags are entered 1312 into the IANA registry as new records of type 'language'. 1314 11. Codes assigned by ISO 639-3 that do not conflict with existing 1315 three-letter primary language subtags are entered into the IANA 1316 registry as new primary language records. 1318 12. Codes assigned by ISO 15924 and ISO 3166 that do not conflict 1319 with existing subtags of the associated type and whose meaning 1320 is not the same as an existing subtag of the same type are 1321 entered into the IANA registry as new records. 1323 13. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1324 withdrawn by their respective maintenance or registration 1325 authority remain valid in language tags. A 'Deprecated' field 1326 containing the date of withdrawal MUST be added to the record. 1327 If a new record of the same type is added that represents a 1328 replacement value, then a 'Preferred-Value' field MAY also be 1329 added. The registration process MAY be used to add comments 1330 about the withdrawal of the code by the respective standard. 1332 Example The region code 'TL' was assigned to the country 1333 'Timor-Leste', replacing the code 'TP' (which was assigned to 1334 'East Timor' when it was under administration by Portugal). 1335 The subtag 'TP' remains valid in language tags, but its 1336 record contains the a 'Preferred-Value' of 'TL' and its field 1337 'Deprecated' contains the date the new code was assigned 1338 ('2004-07-06'). 1340 14. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1341 with existing subtags of the associated type, including subtags 1342 that are deprecated, MUST NOT be entered into the registry. The 1343 following additional considerations apply to subtag values that 1344 are reassigned: 1346 A. For ISO 639 codes, if the newly assigned code's meaning is 1347 not represented by a subtag in the IANA registry, the 1348 Language Subtag Reviewer, as described in Section 3.5, SHALL 1349 prepare a proposal for entering in the IANA registry as soon 1350 as practical a registered language subtag as an alternate 1351 value for the new code. The form of the registered language 1352 subtag will be at the discretion of the Language Subtag 1353 Reviewer and MUST conform to other restrictions on language 1354 subtags in this document. 1356 B. For all subtags whose meaning is derived from an external 1357 standard (that is, by ISO 639, ISO 15924, ISO 3166, or UN 1358 M.49), if a new meaning is assigned to an existing code and 1359 the new meaning broadens the meaning of that code, then the 1360 meaning for the associated subtag MAY be changed to match. 1361 The meaning of a subtag MUST NOT be narrowed, however, as 1362 this can result in an unknown proportion of the existing 1363 uses of a subtag becoming invalid. Note: ISO 639 1364 maintenance agency/registration authority (MA/RA) has 1365 adopted a similar stability policy. 1367 C. For ISO 15924 codes, if the newly assigned code's meaning is 1368 not represented by a subtag in the IANA registry, the 1369 Language Subtag Reviewer, as described in Section 3.5, SHALL 1370 prepare a proposal for entering in the IANA registry as soon 1371 as practical a registered variant subtag as an alternate 1372 value for the new code. The form of the registered variant 1373 subtag will be at the discretion of the Language Subtag 1374 Reviewer and MUST conform to other restrictions on variant 1375 subtags in this document. 1377 D. For ISO 3166 codes, if the newly assigned code's meaning is 1378 associated with the same UN M.49 code as another 'region' 1379 subtag, then the existing region subtag remains as the 1380 preferred value for that region and no new entry is created. 1381 A comment MAY be added to the existing region subtag 1382 indicating the relationship to the new ISO 3166 code. 1384 E. For ISO 3166 codes, if the newly assigned code's meaning is 1385 associated with a UN M.49 code that is not represented by an 1386 existing region subtag, then the Language Subtag Reviewer, 1387 as described in Section 3.5, SHALL prepare a proposal for 1388 entering the appropriate UN M.49 country code as an entry in 1389 the IANA registry. 1391 F. For ISO 3166 codes, if there is no associated UN numeric 1392 code, then the Language Subtag Reviewer SHALL petition the 1393 UN to create one. If there is no response from the UN 1394 within ninety days of the request being sent, the Language 1395 Subtag Reviewer SHALL prepare a proposal for entering in the 1396 IANA registry as soon as practical a registered variant 1397 subtag as an alternate value for the new code. The form of 1398 the registered variant subtag will be at the discretion of 1399 the Language Subtag Reviewer and MUST conform to other 1400 restrictions on variant subtags in this document. This 1401 situation is very unlikely to ever occur. 1403 15. UN M.49 has codes for both countries and areas (such as '276' 1404 for Germany) and geographical regions and sub-regions (such as 1405 '150' for Europe). UN M.49 country or area codes for which 1406 there is no corresponding ISO 3166 code SHOULD NOT be 1407 registered, except as a surrogate for an ISO 3166 code that is 1408 blocked from registration by an existing subtag. If such a code 1409 becomes necessary, then the registration authority for ISO 3166 1410 SHOULD first be petitioned to assign a code to the region. If 1411 the petition for a code assignment by ISO 3166 is refused or not 1412 acted on in a timely manner, the registration process described 1413 in Section 3.5 MAY then be used to register the corresponding UN 1414 M.49 code. This way, UN M.49 codes remain available as the 1415 value of last resort in cases where ISO 3166 reassigns a 1416 deprecated value in the registry. 1418 16. Stability provisions apply to grandfathered tags with this 1419 exception: should it be possible to compose one of the 1420 grandfathered tags from registered subtags, then the field 1421 'Type' in that record is changed from 'grandfathered' to 1422 'redundant'. Note that this will not affect language tags that 1423 match the grandfathered tag, since these tags will now match 1424 valid generative subtag sequences. For example, this document 1425 caused the ISO 639-3 code 'gan', used in the redundant tag "zh- 1426 gan", to be registered as an extended language subtag. The 1427 formerly-grandfathered tag "zh-gan" became a redundant tag as a 1428 result (but existing content or implementations that use "zh- 1429 gan" remain valid). 1431 Note: The redundant and grandfathered entries together are the 1432 complete list of tags registered under [RFC3066]. The redundant tags 1433 are those that can now be formed using the subtags defined in the 1434 registry together with the rules of Section 2.2. The grandfathered 1435 entries include those that can never be legal under those same 1436 provisions plus those tags that contain subtags not yet registered 1437 or, perhaps, inappropriate for registration. 1439 The set of redundant and grandfathered tags is permanent and stable: 1440 new entries in this section MUST NOT be added and existing entries 1441 MUST NOT be removed. Records of type 'grandfathered' MAY have their 1442 type converted to 'redundant'; see item 12 in Section 3.6 for more 1443 information. The decision-making process about which tags were 1444 initially grandfathered and which were made redundant is described in 1445 [RFC4645]. 1447 RFC 3066 tags that were deprecated prior to the adoption of [RFC4646] 1448 are part of the list of grandfathered tags, and their component 1449 subtags were not included as registered variants (although they 1450 remain eligible for registration). For example, the tag "art-lojban" 1451 was deprecated in favor of the language subtag 'jbo'. 1453 3.5. Registration Procedure for Subtags 1455 The procedure given here MUST be used by anyone who wants to use a 1456 subtag not currently in the IANA Language Subtag Registry. 1458 Only subtags of type 'language' and 'variant' will be considered for 1459 independent registration of new subtags. Subtags needed for 1460 stability and subtags necessary to keep the registry synchronized 1461 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1462 defined by this document also use this process, as described in 1463 Section 3.3. Stability provisions are described in Section 3.4. 1465 This procedure MAY also be used to register or alter the information 1466 for the 'Description', 'Comments', 'Deprecated', 'Prefix', or 1467 'Suppress-Script' fields in a subtag's record as described in 1468 Section 3.4. Changes to all other fields in the IANA registry are 1469 NOT permitted. 1471 Registering a new subtag or requesting modifications to an existing 1472 tag or subtag starts with the requester filling out the registration 1473 form reproduced below. Note that each response is not limited in 1474 size so that the request can adequately describe the registration. 1475 The fields in the "Record Requested" section SHOULD follow the 1476 requirements in Section 3.1. 1478 LANGUAGE SUBTAG REGISTRATION FORM 1479 1. Name of requester: 1480 2. E-mail address of requester: 1481 3. Record Requested: 1483 Type: 1484 Subtag: 1485 Description: 1486 Prefix: 1487 Preferred-Value: 1488 Deprecated: 1489 Suppress-Script: 1490 Macrolanguage: 1491 Comments: 1493 4. Intended meaning of the subtag: 1494 5. Reference to published description 1495 of the language (book or article): 1496 6. Any other relevant information: 1498 Figure 4: The Language Subtag Registration Form 1500 Examples of completed registration forms can be found in Appendix C 1501 or online at http://www.iana.org/assignments/lang-subtags-templates/. 1503 The subtag registration form MUST be sent to 1504 for a two-week review period before it can 1505 be submitted to IANA. If modifications are made to the request 1506 during the course of the registration process (such as corrections to 1507 meet the requirements in Section 3.1) the modified form MUST also be 1508 sent to at least one week prior to 1509 submission to IANA. 1511 Whenever an entry is created or modified in the registry, the 'File- 1512 Date' record at the start of the registry is updated to reflect the 1513 most recent modification date in the [RFC3339] "full-date" format. 1515 Before forwarding a new registration to IANA, the Language Subtag 1516 Reviewer MUST ensure that values in the 'Subtag' field match case 1517 according to the description in Section 3.1. 1519 The ietf-languages list is an open list and can be joined by sending 1520 a request to . The list can be 1521 hosted by IANA or by any third party at the request of IESG. 1523 Some fields in both the registration form as well as the registry 1524 record itself permit the use of non-ASCII characters. Registration 1525 requests SHOULD use the UTF-8 encoding for consistency and clarity. 1526 However, since some mail clients do not support this encoding, other 1527 encodings MAY be used for the registration request. The Language 1528 Subtag Reviewer is responsible for ensuring that the proper Unicode 1529 characters appear in both the archived request form and the registry 1530 record. In the case of a transcription or encoding error by IANA, 1531 the Language Subtag Reviewer will request that the registry be 1532 repaired, providing any necessary information to assist IANA. 1534 Variant subtags are usually registered for use with a particular 1535 range of language tags. For example, the subtag 'rozaj' is intended 1536 for use with language tags that start with the primary language 1537 subtag "sl", since Resian is a dialect of Slovenian. Thus, the 1538 subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj" 1539 or "sl-IT-rozaj". This information is stored in the 'Prefix' field 1540 in the registry. Variant registration requests SHOULD include at 1541 least one 'Prefix' field in the registration form. 1543 Extended language subtags MUST include exactly one 'Prefix' field. 1545 The 'Prefix' field for a given registered subtag exists in the IANA 1546 registry as a guide to usage. Additional prefixes MAY be added by 1547 filing an additional registration form. In that form, the "Any other 1548 relevant information:" field MUST indicate that it is the addition of 1549 a prefix. 1551 Requests to add a prefix to a variant subtag that imply a different 1552 semantic meaning will probably be rejected. For example, a request 1553 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1554 nedis" represented some German dialect would be rejected. The 1555 'nedis' subtag represents a particular Slovenian dialect and the 1556 additional registration would change the semantic meaning assigned to 1557 the subtag. A separate subtag SHOULD be proposed instead. 1559 The 'Description' field MUST contain a description of the tag being 1560 registered written or transcribed into the Latin script; it MAY also 1561 include a description in a non-Latin script. The 'Description' field 1562 is used for identification purposes and doesn't necessarily represent 1563 the actual native name of the language or variation or to be in any 1564 particular language. 1566 While the 'Description' field itself is not guaranteed to be stable 1567 and errata corrections MAY be undertaken from time to time, attempts 1568 to provide translations or transcriptions of entries in the registry 1569 itself will probably be frowned upon by the community or rejected 1570 outright, as changes of this nature have an impact on the provisions 1571 in Section 3.4. 1573 When the two-week period has passed, the Language Subtag Reviewer 1574 MUST take one of the following actions: 1576 o Explicitly accept the request and forward the form containing the 1577 record to be inserted or modified to iana@iana.org according to 1578 the procedure described in Section 3.3. 1580 o Explicitly reject the request because of significant objections 1581 raised on the list or due to problems with constraints in this 1582 document (which MUST be explicitly cited). 1584 o Extend the review period by granting an additional two-week 1585 increment to permit further discussion. After each two-week 1586 increment, the Language Subtag Reviewer MUST indicate on the list 1587 whether the registration has been accepted, rejected, or extended. 1589 Note that the Language Subtag Reviewer MAY raise objections on the 1590 list if he or she so desires. The important thing is that the 1591 objection MUST be made publicly. 1593 Sometimes the request needs to be modified as a result of discussion 1594 during the review period or due to requirements in this document. 1595 The applicant, Language Subtag Reviewer, or others are free to submit 1596 a modified version of the completed registration form, which will be 1597 considered in lieu of the original request with the explicit approval 1598 of the applicant. Such changes do not restart the two-week 1599 discussion period, although an application containing the final 1600 record submitted to IANA MUST appear on the list at least one week 1601 prior to the Language Subtag Reviewer forwarding the record to IANA. 1602 The applicant is also free to modify a rejected application with 1603 additional information and submit it again; this starts a new two- 1604 week comment period. 1606 Registrations initiated due to the provisions of Section 3.3 or 1607 Section 3.4 SHALL NOT be rejected altogether (since they have to 1608 ultimately appear in the registry) and SHOULD be completed as quickly 1609 as possible. The review process allows list members to comment on 1610 the specific information in the form and the record it contains and 1611 thus help ensure that it is correct and consistent. The Language 1612 Subtag Reviewer MAY reject a specific version of the form, but MUST 1613 include in the rejection a suitable replacement, extending the review 1614 period as described above, until the form is in a format worthy of 1615 reviewer's approval. 1617 Decisions made by the Language Subtag Reviewer MAY be appealed to the 1618 IESG [RFC2028] under the same rules as other IETF decisions 1619 [RFC2026]. This includes a decision to extend the review period or 1620 the failure to announce a decision in a clear and timely manner. 1622 The approved records appear in the Language Subtag Registry. The 1623 approved registration forms are available online under 1624 http://www.iana.org/assignments/lang-subtags-templates/. 1626 Updates or changes to existing records follow the same procedure as 1627 new registrations. The Language Subtag Reviewer decides whether 1628 there is consensus to update the registration following the two week 1629 review period; normally, objections by the original registrant will 1630 carry extra weight in forming such a consensus. 1632 Registrations are permanent and stable. Once registered, subtags 1633 will not be removed from the registry and will remain a valid way in 1634 which to specify a specific language or variant. 1636 Note: The purpose of the "Reference to published description" section 1637 in the registration form is to aid in verifying whether a language is 1638 registered or what language or language variation a particular subtag 1639 refers to. In most cases, reference to an authoritative grammar or 1640 dictionary of that language will be useful; in cases where no such 1641 work exists, other well-known works describing that language or in 1642 that language MAY be appropriate. The Language Subtag Reviewer 1643 decides what constitutes "good enough" reference material. This 1644 requirement is not intended to exclude particular languages or 1645 dialects due to the size of the speaker population or lack of a 1646 standardized orthography. Minority languages will be considered 1647 equally on their own merits. 1649 3.6. Possibilities for Registration 1651 Possibilities for registration of subtags or information about 1652 subtags include: 1654 o Primary language subtags for languages not listed in ISO 639 that 1655 are not variants of any listed or registered language MAY be 1656 registered. At the time this document was created, there were no 1657 examples of this form of subtag. Before attempting to register a 1658 language subtag, there MUST be an attempt to register the language 1659 with ISO 639. Subtags MUST NOT be registered for languages 1660 defined by codes that exist in ISO 639-1, ISO 639-2, or ISO 639-3, 1661 or that are under consideration by the ISO 639 registration 1662 authorities, or that have never been attempted for registration 1663 with those authorities. If ISO 639 has previously rejected a 1664 language for registration, it is reasonable to assume that there 1665 must be additional, very compelling evidence of need before it 1666 will be registered as a primary language subtag in the IANA 1667 registry (to the extent that it is very unlikely that any subtags 1668 will be registered of this type). 1670 o Dialect or other divisions or variations within a language, its 1671 orthography, writing system, regional or historical usage, 1672 transliteration or other transformation, or distinguishing 1673 variation MAY be registered as variant subtags. An example is the 1674 'rozaj' subtag (the Resian dialect of Slovenian). 1676 o The addition or maintenance of fields (generally of an 1677 informational nature) in Tag or Subtag records as described in 1678 Section 3.1 and subject to the stability provisions in 1679 Section 3.4. This includes descriptions, comments, deprecation 1680 and preferred values for obsolete or withdrawn codes, or the 1681 addition of script or macrolanguage information to primary 1682 language subtags. 1684 o The addition of records and related field value changes necessary 1685 to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and 1686 UN M.49 as described in Section 3.4. 1688 Subtags proposed for registration that would cause all or part of a 1689 grandfathered tag to become redundant but whose meaning conflicts 1690 with or alters the meaning of the grandfathered tag MUST be rejected. 1692 This document leaves the decision on what subtags or changes to 1693 subtags are appropriate (or not) to the registration process 1694 described in Section 3.5. 1696 Note: four-character primary language subtags are reserved to allow 1697 for the possibility of alpha4 codes in some future addition to the 1698 ISO 639 family of standards. 1700 ISO 639 defines a maintenance agency for additions to and changes in 1701 the list of languages in ISO 639. This agency is: 1703 International Information Centre for Terminology (Infoterm) 1704 Aichholzgasse 6/12, AT-1120 1705 Wien, Austria 1706 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1708 ISO 639-2 defines a maintenance agency for additions to and changes 1709 in the list of languages in ISO 639-2. This agency is: 1711 Library of Congress 1712 Network Development and MARC Standards Office 1713 Washington, D.C. 20540 USA 1714 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1715 URL: http://www.loc.gov/standards/iso639-2 1717 ISO 639-3 defines a maintenance agency for additions to and changes 1718 in the list of languages in ISO 639-3. This agency is: 1720 SIL International 1721 ISO 639-3 Registrar 1722 7500 W. Camp Wisdom Rd. 1723 Dallas, TX 75236 USA 1724 Phone: +1 972 708 7400, ext. 2293 Fax: +1 972 708 7546 1725 Email: iso639-3@sil.org 1726 URL: http://www.sil.org/iso639-3 1728 The maintenance agency for ISO 3166 (country codes) is: 1730 ISO 3166 Maintenance Agency 1731 c/o International Organization for Standardization 1732 Case postale 56 1733 CH-1211 Geneva 20 Switzerland 1734 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1735 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1737 The registration authority for ISO 15924 (script codes) is: 1739 Unicode Consortium Box 391476 1740 Mountain View, CA 94039-1476, USA 1741 URL: http://www.unicode.org/iso15924 1743 The Statistics Division of the United Nations Secretariat maintains 1744 the Standard Country or Area Codes for Statistical Use and can be 1745 reached at: 1747 Statistical Services Branch 1748 Statistics Division 1749 United Nations, Room DC2-1620 1750 New York, NY 10017, USA 1752 Fax: +1-212-963-0623 1753 E-mail: statistics@un.org 1754 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1756 3.7. Extensions and Extensions Registry 1758 Extension subtags are those introduced by single-character subtags 1759 ("singletons") other than 'x'. They are reserved for the generation 1760 of identifiers that contain a language component and are compatible 1761 with applications that understand language tags. 1763 The structure and form of extensions are defined by this document so 1764 that implementations can be created that are forward compatible with 1765 applications that might be created using singletons in the future. 1767 In addition, defining a mechanism for maintaining singletons will 1768 lend stability to this document by reducing the likely need for 1769 future revisions or updates. 1771 Single-character subtags are assigned by IANA using the "IETF 1772 Consensus" policy defined by [RFC2434]. This policy requires the 1773 development of an RFC, which SHALL define the name, purpose, 1774 processes, and procedures for maintaining the subtags. The 1775 maintaining or registering authority, including name, contact email, 1776 discussion list email, and URL location of the registry, MUST be 1777 indicated clearly in the RFC. The RFC MUST specify or include each 1778 of the following: 1780 o The specification MUST reference the specific version or revision 1781 of this document that governs its creation and MUST reference this 1782 section of this document. 1784 o The specification and all subtags defined by the specification 1785 MUST follow the ABNF and other rules for the formation of tags and 1786 subtags as defined in this document. In particular, it MUST 1787 specify that case is not significant and that subtags MUST NOT 1788 exceed eight characters in length. 1790 o The specification MUST specify a canonical representation. 1792 o The specification of valid subtags MUST be available over the 1793 Internet and at no cost. 1795 o The specification MUST be in the public domain or available via a 1796 royalty-free license acceptable to the IETF and specified in the 1797 RFC. 1799 o The specification MUST be versioned, and each version of the 1800 specification MUST be numbered, dated, and stable. 1802 o The specification MUST be stable. That is, extension subtags, 1803 once defined by a specification, MUST NOT be retracted or change 1804 in meaning in any substantial way. 1806 o The specification MUST include in a separate section the 1807 registration form reproduced in this section (below) to be used in 1808 registering the extension upon publication as an RFC. 1810 o IANA MUST be informed of changes to the contact information and 1811 URL for the specification. 1813 IANA will maintain a registry of allocated single-character 1814 (singleton) subtags. This registry MUST use the record-jar format 1815 described by the ABNF in Section 3.1. Upon publication of an 1816 extension as an RFC, the maintaining authority defined in the RFC 1817 MUST forward this registration form to iesg@ietf.org, who MUST 1818 forward the request to iana@iana.org. The maintaining authority of 1819 the extension MUST maintain the accuracy of the record by sending an 1820 updated full copy of the record to iana@iana.org with the subject 1821 line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only 1822 the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY 1823 be modified in these updates. 1825 Failure to maintain this record, maintain the corresponding registry, 1826 or meet other conditions imposed by this section of this document MAY 1827 be appealed to the IESG [RFC2028] under the same rules as other IETF 1828 decisions (see [RFC2026]) and MAY result in the authority to maintain 1829 the extension being withdrawn or reassigned by the IESG. 1830 %% 1831 Identifier: 1832 Description: 1833 Comments: 1834 Added: 1835 RFC: 1836 Authority: 1837 Contact_Email: 1838 Mailing_List: 1839 URL: 1840 %% 1842 Figure 5: Format of Records in the Language Tag Extensions Registry 1844 'Identifier' contains the single-character subtag (singleton) 1845 assigned to the extension. The Internet-Draft submitted to define 1846 the extension SHOULD specify which letter or digit to use, although 1847 the IESG MAY change the assignment when approving the RFC. 1849 'Description' contains the name and description of the extension. 1851 'Comments' is an OPTIONAL field and MAY contain a broader description 1852 of the extension. 1854 'Added' contains the date the RFC was published in the "full-date" 1855 format specified in [RFC3339]. For example: 2004-06-28 represents 1856 June 28, 2004, in the Gregorian calendar. 1858 'RFC' contains the RFC number assigned to the extension. 1860 'Authority' contains the name of the maintaining authority for the 1861 extension. 1863 'Contact_Email' contains the email address used to contact the 1864 maintaining authority. 1866 'Mailing_List' contains the URL or subscription email address of the 1867 mailing list used by the maintaining authority. 1869 'URL' contains the URL of the registry for this extension. 1871 The determination of whether an Internet-Draft meets the above 1872 conditions and the decision to grant or withhold such authority rests 1873 solely with the IESG and is subject to the normal review and appeals 1874 process associated with the RFC process. 1876 Extension authors are strongly cautioned that many (including most 1877 well-formed) processors will be unaware of any special relationships 1878 or meaning inherent in the order of extension subtags. Extension 1879 authors SHOULD avoid subtag relationships or canonicalization 1880 mechanisms that interfere with matching or with length restrictions 1881 that sometimes exist in common protocols where the extension is used. 1882 In particular, applications MAY truncate the subtags in doing 1883 matching or in fitting into limited lengths, so it is RECOMMENDED 1884 that the most significant information be in the most significant 1885 (left-most) subtags and that the specification gracefully handle 1886 truncated subtags. 1888 When a language tag is to be used in a specific, known, protocol, it 1889 is RECOMMENDED that that the language tag not contain extensions not 1890 supported by that protocol. In addition, note that some protocols 1891 MAY impose upper limits on the length of the strings used to store or 1892 transport the language tag. 1894 3.8. Update of the Language Subtag Registry 1896 Upon adoption of this document the IANA Language Subtag Registry will 1897 need an update so that it contains the complete set of subtags valid 1898 in a language tag. This collection of subtags, along with a 1899 description of the process used to create it, is described by 1900 [registry-update]. IANA will publish the updated version of the 1901 registry described by this document using the instructions and 1902 content of [registry-update]. Once published by IANA, the 1903 maintenance procedures, rules, and registration processes described 1904 in this document will be available for new registrations or updates. 1906 Registrations that are in process under the rules defined in 1907 [RFC4646] when this document is adopted MUST be completed under the 1908 rules contained in this document. 1910 4. Formation and Processing of Language Tags 1912 This section addresses how to use the information in the registry 1913 with the tag syntax to choose, form, and process language tags. 1915 4.1. Choice of Language Tag 1917 The guiding principle in forming language tags is to "tag content 1918 wisely." Sometimes there is a choice between several possible tags 1919 for the same content. The choice of which tag to use depends on the 1920 content and application in question and some amount of judgment might 1921 be necessary when selecting a tag. 1923 Interoperability is best served when the same language tag is used 1924 consistently to represent the same language. If an application has 1925 requirements that make the rules here inapplicable, then that 1926 application risks damaging interoperability. It is strongly 1927 RECOMMENDED that users not define their own rules for language tag 1928 choice. 1930 A subtag SHOULD only be used when it adds useful distinguishing 1931 information to the tag. Extraneous subtags interfere with the 1932 meaning, understanding, and processing of language tags. In 1933 particular, users and implementations SHOULD follow the 'Prefix' and 1934 'Suppress-Script' fields in the registry (defined in Section 3.1): 1935 these fields provide guidance on when specific additional subtags 1936 SHOULD be used or avoided in a language tag. 1938 Some applications can benefit from the use of script subtags in 1939 language tags, as long as the use is consistent for a given context. 1940 Script subtags are never appropriate for unwritten content (such as 1941 audio recordings). 1943 Script subtags were not formally defined in [RFC3066] and their use 1944 can affect matching and subtag identification for implementations of 1945 RFC 3066, as these subtags appear between the primary language and 1946 region subtags. For example, if an implementation selects content 1947 using Basic Filtering [RFC4647] (originally described in Section 2.5 1948 of [RFC3066]) and the user requested the language range "en-US", 1949 content labeled "en-Latn-US" will not match the request and thus not 1950 be selected. Therefore, it is important to know when script subtags 1951 will customarily be used and when they ought not be used. In the 1952 registry, the Suppress-Script field helps ensure greater 1953 compatibility between the language tags by defining when users SHOULD 1954 NOT include a script subtag with a particular primary language 1955 subtag. 1957 The choice of subtags used to form a language tag SHOULD be guided by 1958 the following rules: 1960 1. Use as precise a tag as possible, but no more specific than is 1961 justified. Avoid using subtags that are not important for 1962 distinguishing content in an application. 1964 * For example, 'de' might suffice for tagging an email written 1965 in German, while "de-CH-1996" is probably unnecessarily 1966 precise for such a task. 1968 2. The script subtag SHOULD NOT be used to form language tags unless 1969 the script adds some distinguishing information to the tag. The 1970 field 'Suppress-Script' in the primary language record in the 1971 registry indicates script subtags that do not add distinguishing 1972 information for most applications. For example: 1974 * The subtag 'Latn' should not be used with the primary language 1975 'en' because nearly all English documents are written in the 1976 Latin script and it adds no distinguishing information. 1977 However, if a document were written in English mixing Latin 1978 script with another script such as Braille ('Brai'), then it 1979 might be appropriate to choose to indicate both scripts to aid 1980 in content selection, such as the application of a style 1981 sheet. 1983 * When labeling content that is unwritten (such as a recording 1984 of human speech), the script subtag should not be used, even 1985 if the language is customarily written in several scripts. 1986 Thus the subtitles to a movie might use the tag "zh-cmn-Hant" 1987 (Chinese, Mandarin, Traditional script), but the audio track 1988 for the same language would be tagged "zh-cmn". 1990 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1991 entry, then the value of that field SHOULD be used to form the 1992 language tag in preference to the tag or subtag in which the 1993 preferred value appears. 1995 * For example, use 'he' for Hebrew in preference to 'iw'. 1997 4. [ISO639-2] has defined several codes included in the subtag 1998 registry that require additional care when choosing language 1999 tags. In most of these cases, where omitting the language tag is 2000 permitted, such omission is preferable to using these codes. 2001 Language tags SHOULD NOT incorporate these subtags as a prefix, 2002 unless the additional information conveys some value to the 2003 application. 2005 1. Use specific language subtags or subtag sequences in 2006 preference to subtags for language collections. A "language 2007 collection" is a subtag derived from one of the [ISO639-2] 2008 codes that represents multiple related languages. These 2009 codes are included as primary language subtags in the 2010 registry. For example, the code 'cmc' represents "Chamic 2011 languages". The registry contains values for each of the 2012 approximately ten individual languages represented by this 2013 collective code. Some other examples include the subtags 2014 Germanic languages ('gem') or Algonquian languages ('alg'). 2015 Since these codes are interpreted inclusively, content tagged 2016 with "en" (English), "de" (German), or "gsw" (Swiss German, 2017 Alemannic) could also (but SHOULD NOT) be tagged with "gem" 2018 (Germanic languages). Subtags derived from collection codes 2019 SHOULD NOT be used be used unless more specific language 2020 information is not available. Note that matching 2021 implementations generally do not understand the relationship 2022 between the collection and its encompassed languages, and so 2023 users ought not assume a subtag based on a language 2024 collection is a useful means for selecting content in its 2025 encompassed languages. 2027 2. The 'mul' (Multiple) primary language subtag identifies 2028 content in multiple languages. It SHOULD NOT be used when a 2029 list of languages (such as Content-Language) or individual 2030 tags for each content element can be used instead. 2032 3. The 'und' (Undetermined) primary language subtag identifies 2033 linguistic content whose language is not known. It SHOULD 2034 NOT be used unless a language tag is required and language 2035 information is not available or cannot be determined. 2036 Omitting the language tag (where permitted) is preferred. 2037 The 'und' subtag MAY be useful for protocols that require a 2038 language tag to be provided or where a primary language 2039 subtag is required (such as in "und-Latn"). The 'und' subtag 2040 MAY also be useful when matching language tags in certain 2041 situations. 2043 4. The 'zxx' (Non-Linguistic) primary language subtag identifies 2044 content that has no language. Some examples might include 2045 instrumental or electronic music; sound recordings consisting 2046 of nonverbal sounds; audiovisual materials with no narration, 2047 printed titles, or subtitles; machine-readable data files 2048 consisting of machine languages or character codes; or 2049 programming source code. Note: where there are fragments of 2050 linguistic content, such as programming source code 2051 containing comments written in English, the subtag 'zxx' 2052 might still be used to indicate the primary status of the 2053 content, just as 'en' can be applied to a predominantly 2054 English text that contains a few French phrases. 2056 5. The 'mis' (Uncoded) primary language subtag identifies 2057 content whose language is known but which does not currently 2058 have a corresponding subtag. This subtag SHOULD NOT be used. 2059 Because the addition of other codes in the future can render 2060 its application invalid, it is inherently unstable and hence 2061 incompatible with the stability goals of BCP 47. It is 2062 always preferable to use other subtags: either 'und' or (with 2063 prior agreement) private use subtags. 2065 6. The grandfathered tag "i-default" (Default Language) was 2066 originally registered according to [RFC1766] to meet the 2067 needs of [RFC2277]. It is used to indicate not a specific 2068 language, but rather, it identifies the condition or content 2069 used where the language preferences of the user cannot be 2070 established. It SHOULD NOT be used except as a means of 2071 labeling the default content for applications or protocols 2072 that require default language content to be labeled with that 2073 specific tag. It MAY also be used by an application or 2074 protocol to identify when the default language content is 2075 being returned. 2077 5. The same variant subtag MUST NOT be used more than once within a 2078 language tag. 2080 * For example, the tag "de-DE-1901-1901" is not valid. 2082 Languages with a Macrolanguage field in the registry sometimes can be 2083 usefully referenced using their Macrolanguage. However, the 2084 Macrolanguage field doesn't define what the relationship is between 2085 the language subtag whose record it appears in and its encompassed 2086 language or languages. Nor does it define how the encompassed 2087 languages are related to one-another. In some cases, the 2088 Macrolanguage has a standard form as well as a variety of less-common 2089 dialects. In other cases there is no particular standard form and 2090 the encompassed subtags describe specific variations within the 2091 parent language. 2093 Applications MAY use Macrolanguage information to improve matching or 2094 language negotiation. For example, the information that 'sr' 2095 (Serbian) and 'hr' (Croatian) share a Macrolanguage expresses a 2096 closer relation between those languages than between, say, 'sr' 2097 (Serbian) and 'ma' (Macedonian). It is valid to use the encompassed 2098 language or just its Macrolanguage to form language tags. However, 2099 many matching applications will not be aware of the relationship 2100 between the languages. Care in selecting which subtags are used is 2101 crucial to interoperability. In general, use the most specific tag. 2102 However, where the standard form of an encompassed language is 2103 captured by the Macrolanguage, the Macrolanguage SHOULD be used in 2104 preference to one of its sublanguages unless there is a specific 2105 reason not to. 2107 In particular, the Chinese family of languages call for special 2108 consideration. Because the written form is very similar for most 2109 languages having 'zh' as a Macrolanguage (and because historically 2110 subtags for the various sub-languages and dialects were not 2111 available), languages such as 'yue' (Cantonese) have usually used 2112 tags beginning with the subtag 'zh'. This means that Macrolanguage 2113 information can be usefully applied when searching for content or 2114 when providing fallbacks in language negotiation. For example, the 2115 information that 'yue' has a macrolangauge of 'zh' could be used in 2116 the Lookup algorithm to fallback from a request for "yue-Hans-CN" to 2117 "zh-Hans-CN" without losing the script and region information (even 2118 though the user did not specify "zh-Hans-CN" in their request). 2120 To ensure consistent backward compatibility, this document contains 2121 several provisions to account for potential instability in the 2122 standards used to define the subtags that make up language tags. 2123 These provisions mean that no language tag created under the rules in 2124 this document will become invalid. 2126 Standards, protocols, and applications that reference this document 2127 normatively but apply different rules to the ones given in this 2128 section MUST specify how language tag selection varies from the 2129 guidelines given here. 2131 4.2. Meaning of the Language Tag 2133 The meaning of a language tag is related to the meaning of the 2134 subtags that it contains. Each subtag, in turn, implies a certain 2135 range of expectations one might have for related content, although it 2136 is not a guarantee. For example, the use of a script subtag such as 2137 'Arab' (Arabic script) does not mean that the content contains only 2138 Arabic characters. It does mean that the language involved is 2139 predominently in the Arabic script. Thus a language tag and its 2140 subtags can encompass a very wide range of variation and yet remain 2141 valid in each particular instance. 2143 Validity of a tag is not everything. While every valid tag has a 2144 meaning, it might not represent any real-world language usage. This 2145 is unavoidable in a system in which subtags can be combined freely. 2146 For example, tags such as "ar-Cyrl-CO" (Arabic, Cyrillic script, as 2147 used in Colombia ) or "tlh-Kore-AQ-fonipa" (Klingon, Korean script, 2148 as used in Antarctica, IPA phonetic transcription) are both valid and 2149 unlikely to represent a useful combination of language attributes. 2151 The relationship between the tag and the information it identifies is 2152 defined by the context in which the tag appears. Accordingly, this 2153 section gives only possible examples of its usage. 2155 o For a single information object, the associated language tags 2156 might be interpreted as the set of languages that is necessary for 2157 a complete comprehension of the complete object. Example: Plain 2158 text documents. 2160 o For an aggregation of information objects, the associated language 2161 tags could be taken as the set of languages used inside components 2162 of that aggregation. Examples: Document stores and libraries. 2164 o For information objects whose purpose is to provide alternatives, 2165 the associated language tags could be regarded as a hint that the 2166 content is provided in several languages and that one has to 2167 inspect each of the alternatives in order to find its language or 2168 languages. In this case, the presence of multiple tags might not 2169 mean that one needs to be multi-lingual to get complete 2170 understanding of the document. Example: MIME multipart/ 2171 alternative. 2173 o In markup languages, such as HTML and XML, language information 2174 can be added to each part of the document identified by the markup 2175 structure (including the whole document itself). For example, one 2176 could write C'est la vie. inside a 2177 Norwegian document; the Norwegian-speaking user could then access 2178 a French-Norwegian dictionary to find out what the marked section 2179 meant. If the user were listening to that document through a 2180 speech synthesis interface, this formation could be used to signal 2181 the synthesizer to appropriately apply French text-to-speech 2182 pronunciation rules to that span of text, instead of applying the 2183 inappropriate Norwegian rules. 2185 Language tags are related when they contain a similar sequence of 2186 subtags. For example, if a language tag B contains language tag A as 2187 a prefix, then B is typically "narrower" or "more specific" than A. 2188 Thus, "zh-Hant-TW" is more specific than "zh-Hant". 2190 This relationship is not guaranteed in all cases: specifically, 2191 languages that begin with the same sequence of subtags are NOT 2192 guaranteed to be mutually intelligible, although they might be. For 2193 example, the tag "az" shares a prefix with both "az-Latn" 2194 (Azerbaijani written using the Latin script) and "az-Cyrl" 2195 (Azerbaijani written using the Cyrillic script). A person fluent in 2196 one script might not be able to read the other, even though the text 2197 might be identical. Content tagged as "az" most probably is written 2198 in just one script and thus might not be intelligible to a reader 2199 familiar with the other script. 2201 4.3. Length Considerations 2203 There is no defined upper limit on the size of language tags. While 2204 historically most language tags have consisted of language and region 2205 subtags with a combined total length of up to six characters, larger 2206 tags have always been both possible and actually appeared in use. 2208 Neither the language tag syntax nor other requirements in this 2209 document impose a fixed upper limit on the number of subtags in a 2210 language tag (and thus an upper bound on the size of a tag). The 2211 language tag syntax suggests that, depending on the specific 2212 language, more subtags (and thus a longer tag) are sometimes 2213 necessary to completely identify the language for certain 2214 applications; thus, it is possible to envision long or complex subtag 2215 sequences. 2217 4.3.1. Working with Limited Buffer Sizes 2219 Some applications and protocols are forced to allocate fixed buffer 2220 sizes or otherwise limit the length of a language tag. A conformant 2221 implementation or specification MAY refuse to support the storage of 2222 language tags that exceed a specified length. Any such limitation 2223 SHOULD be clearly documented, and such documentation SHOULD include 2224 what happens to longer tags (for example, whether an error value is 2225 generated or the language tag is truncated). A protocol that allows 2226 tags to be truncated at an arbitrary limit, without giving any 2227 indication of what that limit is, has the potential for causing harm 2228 by changing the meaning of tags in substantial ways. 2230 In practice, most language tags do not require more than a few 2231 subtags and will not approach reasonably sized buffer limitations; 2232 see Section 4.1. 2234 Some specifications or protocols have limits on tag length but do not 2235 have a fixed length limitation. For example, [RFC2231] has no 2236 explicit length limitation: the length available for the language tag 2237 is constrained by the length of other header components (such as the 2238 charset's name) coupled with the 76-character limit in [RFC2047]. 2239 Thus, the "limit" might be 50 or more characters, but it could 2240 potentially be quite small. 2242 The considerations for assigning a buffer limit are: 2244 Implementations SHOULD NOT truncate language tags unless the 2245 meaning of the tag is purposefully being changed, or unless the 2246 tag does not fit into a limited buffer size specified by a 2247 protocol for storage or transmission. 2249 Implementations SHOULD warn the user when a tag is truncated since 2250 truncation changes the semantic meaning of the tag. 2252 Implementations of protocols or specifications that are space 2253 constrained but do not have a fixed limit SHOULD use the longest 2254 possible tag in preference to truncation. 2256 Protocols or specifications that specify limited buffer sizes for 2257 language tags MUST allow for language tags of up to 33 characters. 2259 Protocols or specifications that specify limited buffer sizes for 2260 language tags SHOULD allow for language tags of at least 30 2261 characters. Note that RFC 4646 [RFC4646] recommended a field size 2262 of 42 character because it included the permanently reserved (and 2263 unused) 'extlang' production. The current size recommendation 2264 does not include the use of the 'extlang' field. 2266 The following illustration shows how the 30-character recommendation 2267 was derived. The combination of language and extended language 2268 subtags was chosen for future compatibility. At up to 15 characters, 2269 this combination is longer than the longest possible primary language 2270 subtag (8 characters): 2272 language = 3 (ISO 639-2; ISO 639-1 requires 2) 2273 script = 5 (if not suppressed: see Section 4.1) 2274 region = 4 (UN M.49; ISO 3166 requires 3) 2275 variant1 = 9 (needs 'language' as a prefix) 2276 variant2 = 9 (needs 'language-variant1' as a prefix) 2278 total = 30 characters 2280 Figure 6: Derivation of the Limit on Tag Length 2282 4.3.2. Truncation of Language Tags 2284 Truncation of a language tag alters the meaning of the tag, and thus 2285 SHOULD be avoided. However, truncation of language tags is sometimes 2286 necessary due to limited buffer sizes. Such truncation MUST NOT 2287 permit a subtag to be chopped off in the middle or the formation of 2288 invalid tags (for example, one ending with the "-" character). 2290 This means that applications or protocols that truncate tags MUST do 2291 so by progressively removing subtags along with their preceding "-" 2292 from the right side of the language tag until the tag is short enough 2293 for the given buffer. If the resulting tag ends with a single- 2294 character subtag, that subtag and its preceding "-" MUST also be 2295 removed. For example: 2297 Tag to truncate: zh-Latn-CN-variant1-a-extend1-x-wadegile-private1 2298 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 2299 2. zh-Latn-CN-variant1-a-extend1 2300 3. zh-Latn-CN-variant1 2301 4. zh-Latn-CN 2302 5. zh-Latn 2303 6. zh 2305 Figure 7: Example of Tag Truncation 2307 4.4. Canonicalization of Language Tags 2309 Since a particular language tag is sometimes used by many processes, 2310 language tags SHOULD always be created or generated in a canonical 2311 form. 2313 A language tag is in canonical form when: 2315 1. The tag is well-formed according the rules in Section 2.1 and 2316 Section 2.2. 2318 2. Subtags of type 'Region' that have a Preferred-Value mapping in 2319 the IANA registry (see Section 3.1) SHOULD be replaced with their 2320 mapped value. Note: In rare cases, the mapped value will also 2321 have a Preferred-Value. 2323 3. Redundant or grandfathered tags that have a Preferred-Value 2324 mapping in the IANA registry (see Section 3.1) MUST be replaced 2325 with their mapped value. These items either are deprecated 2326 mappings created before the adoption of this document (such as 2327 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 2328 the result of later registrations or additions to this document 2329 (for example, "zh-hakka" was deprecated in favor of the ISO 639-3 2330 code 'hak' when this document was adopted). 2332 4. Other subtags that have a Preferred-Value mapping in the IANA 2333 registry (see Section 3.1) MUST be replaced with their mapped 2334 value. These items consist entirely of clerical corrections to 2335 ISO 639-1 in which the deprecated subtags have been maintained 2336 for compatibility purposes. 2338 5. If more than one extension subtag sequence exists, the extension 2339 sequences are ordered into case-insensitive ASCII order by 2340 singleton subtag. 2342 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 2343 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 2344 canonical form. 2346 Example: The language tag "en-BU" (English as used in Burma) is not 2347 canonical because the 'BU' subtag has a canonical mapping to 'MM' 2348 (Myanmar), although the tag "en-BU" maintains its validity. 2350 Canonicalization of language tags does not imply anything about the 2351 use of upper or lowercase letters when processing or comparing 2352 subtags (and as described in Section 2.1). All comparisons MUST be 2353 performed in a case-insensitive manner. 2355 When performing canonicalization of language tags, processors MAY 2356 regularize the case of the subtags (that is, this process is 2357 OPTIONAL), following the case used in the registry. Note that this 2358 corresponds to the following casing rules: uppercase all non-initial 2359 two-letter subtags; titlecase all non-initial four-letter subtags; 2360 lowercase everything else. 2362 Note: Case folding of ASCII letters in certain locales, unless 2363 carefully handled, sometimes produces non-ASCII character values. 2364 The Unicode Character Database file "SpecialCasing.txt" defines the 2365 specific cases that are known to cause problems with this. In 2366 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 2367 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 2368 Implementers SHOULD specify a locale-neutral casing operation to 2369 ensure that case folding of subtags does not produce this value, 2370 which is illegal in language tags. For example, if one were to 2371 uppercase the region subtag 'in' using Turkish locale rules, the 2372 sequence U+0130 U+004E would result instead of the expected 'IN'. 2374 Note: if the field 'Deprecated' appears in a registry record without 2375 an accompanying 'Preferred-Value' field, then that tag or subtag is 2376 deprecated without a replacement. Validating processors SHOULD NOT 2377 generate tags that include these values, although the values are 2378 canonical when they appear in a language tag. 2380 An extension MUST define any relationships that exist between the 2381 various subtags in the extension and thus MAY define an alternate 2382 canonicalization scheme for the extension's subtags. Extensions MAY 2383 define how the order of the extension's subtags are interpreted. For 2384 example, an extension could define that its subtags are in canonical 2385 order when the subtags are placed into ASCII order: that is, "en-a- 2386 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 2387 define that the order of the subtags influences their semantic 2388 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 2389 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 2390 so that they are tolerant of the typical processes described in 2391 Section 3.7. 2393 4.5. Considerations for Private Use Subtags 2395 Private use subtags, like all other subtags, MUST conform to the 2396 format and content constraints in the ABNF. Private use subtags have 2397 no meaning outside the private agreement between the parties that 2398 intend to use or exchange language tags that employ them. The same 2399 subtags MAY be used with a different meaning under a separate private 2400 agreement. They SHOULD NOT be used where alternatives exist and 2401 SHOULD NOT be used in content or protocols intended for general use. 2403 Private use subtags are simply useless for information exchange 2404 without prior arrangement. The value and semantic meaning of private 2405 use tags and of the subtags used within such a language tag are not 2406 defined by this document. 2408 Subtags defined in the IANA registry as having a specific private use 2409 meaning convey more information that a purely private use tag 2410 prefixed by the singleton subtag 'x'. For applications, this 2411 additional information MAY be useful. 2413 For example, the region subtags 'AA', 'ZZ', and in the ranges 2414 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 2415 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 2416 great deal of public, interchangeable information about the language 2417 material (that it is Chinese in the simplified Chinese script and is 2418 suitable for some geographic region 'XQ'). While the precise 2419 geographic region is not known outside of private agreement, the tag 2420 conveys far more information than an opaque tag such as "x-someLang", 2421 which contains no information about the language subtag or script 2422 subtag outside of the private agreement. 2424 However, in some cases content tagged with private use subtags MAY 2425 interact with other systems in a different and possibly unsuitable 2426 manner compared to tags that use opaque, privately defined subtags, 2427 so the choice of the best approach sometimes depends on the 2428 particular domain in question. 2430 5. IANA Considerations 2432 This section deals with the processes and requirements necessary for 2433 IANA to undertake to maintain the subtag and extension registries as 2434 defined by this document and in accordance with the requirements of 2435 [RFC2434]. 2437 The impact on the IANA maintainers of the two registries defined by 2438 this document will be a small increase in the frequency of new 2439 entries or updates. 2441 5.1. Language Subtag Registry 2443 Upon adoption of this document, IANA will update the registry using 2444 instructions and content provided in a companion document: 2445 [registry-update]. The criteria and process for selecting the 2446 updated set of records are described in that document. The updated 2447 set of records represents no impact on IANA, since the work to create 2448 it will be performed externally. 2450 Future work on the Language Subtag Registry has been limited to 2451 inserting or replacing whole records preformatted for IANA by the 2452 Language Subtag Reviewer as described in Section 3.3 of this document 2453 and archiving and making publically available the forwarded 2454 registration form. 2456 Each registration form sent to IANA contains a single record for 2457 incorporation into the registry. The form MUST be sent to 2458 iana@iana.org by the Language Subtag Reviewer. It will have a 2459 subject line indicating whether the enclosed form represents an 2460 insertion of a new record (indicated by the word "INSERT" in the 2461 subject line) or a replacement of an existing record (indicated by 2462 the word "MODIFY" in the subject line). Records MUST NOT be deleted 2463 from the registry. 2465 IANA MUST extract the record from the form and place the inserted or 2466 modified record into the appropriate section of the language subtag 2467 registry, grouping the records by their 'Type' field. Inserted 2468 records MAY be placed anywhere in the appropriate section; there is 2469 no guarantee of the order of the records beyond grouping them 2470 together by 'Type'. Modified records MUST overwrite the record they 2471 replace. 2473 IANA MUST update the File-Date record to contain the most recent 2474 modification date when performing any inserting or modification: 2475 included in any request to insert or modify records will be a new 2476 File-Date record indicating the acceptance date of the record. This 2477 record MUST be placed first in the registry, replacing the existing 2478 File-Date record. In the event that the File-Date record present in 2479 the registry has a later date than the record being inserted or 2480 modified, then the latest (most recent) record MUST be preserved. 2481 IANA SHOULD process multiple registration requests in order according 2482 to the File-Date in the form, since one registration could otherwise 2483 cause a more recent change to be overwritten. 2485 The updated registry file MUST use the UTF-8 character encoding and 2486 IANA MUST check the registry file for proper encoding. Non-ASCII 2487 characters can be sent to IANA by attaching the registration form to 2488 the email message or by using various encodings in the mail message 2489 body (UTF-8 is recommended). IANA will verify any unclear or 2490 corrupted characters with the Language Subtag Reviewer prior to 2491 posting the updated registry. 2493 The registration form sent to IANA MUST be archived and made publicly 2494 available from 2495 "http://www.iana.org/assignments/lang-subtags-templates/". Note that 2496 multiple registrations can pertain to the same record in the 2497 registry. 2499 Developers who are dependent upon the language subtag registry 2500 sometimes would like to be informed of changes in the registry so 2501 that they can update their implementations. When any change is made 2502 to the language subtag registry, IANA MUST send an announcement 2503 message to ietf-languages-announcements@iana.org (a self-subscribing 2504 list that only IANA can post to). 2506 5.2. Extensions Registry 2508 The Language Tag Extensions Registry can contain at most 35 records 2509 and thus changes to this registry are expected to be very infrequent. 2511 Future work by IANA on the Language Tag Extensions Registry is 2512 limited to two cases. First, the IESG MAY request that new records 2513 be inserted into this registry from time to time. These requests 2514 MUST include the record to insert in the exact format described in 2515 Section 3.7. In addition, there MAY be occasional requests from the 2516 maintaining authority for a specific extension to update the contact 2517 information or URLs in the record. These requests MUST include the 2518 complete, updated record. IANA is not responsible for validating the 2519 information provided, only that it is properly formatted. It should 2520 reasonably be seen to come from the maintaining authority named in 2521 the record present in the registry. 2523 6. Security Considerations 2525 Language tags used in content negotiation, like any other information 2526 exchanged on the Internet, might be a source of concern because they 2527 might be used to infer the nationality of the sender, and thus 2528 identify potential targets for surveillance. 2530 This is a special case of the general problem that anything sent is 2531 visible to the receiving party and possibly to third parties as well. 2532 It is useful to be aware that such concerns can exist in some cases. 2534 The evaluation of the exact magnitude of the threat, and any possible 2535 countermeasures, is left to each application protocol (see BCP 72 2536 [RFC3552] for best current practice guidance on security threats and 2537 defenses). 2539 The language tag associated with a particular information item is of 2540 no consequence whatsoever in determining whether that content might 2541 contain possible homographs. The fact that a text is tagged as being 2542 in one language or using a particular script subtag provides no 2543 assurance whatsoever that it does not contain characters from scripts 2544 other than the one(s) associated with or specified by that language 2545 tag. 2547 Since there is no limit to the number of variant, private use, and 2548 extension subtags, and consequently no limit on the possible length 2549 of a tag, implementations need to guard against buffer overflow 2550 attacks. See Section 4.3 for details on language tag truncation, 2551 which can occur as a consequence of defenses against buffer overflow. 2553 Although the specification of valid subtags for an extension (see 2554 Section 3.7) MUST be available over the Internet, implementations 2555 SHOULD NOT mechanically depend on it being always accessible, to 2556 prevent denial-of-service attacks. 2558 7. Character Set Considerations 2560 The syntax in this document requires that language tags use only the 2561 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2562 character sets, so the composition of language tags should not have 2563 any character set issues. 2565 Rendering of characters based on the content of a language tag is not 2566 addressed in this memo. Historically, some languages have relied on 2567 the use of specific character sets or other information in order to 2568 infer how a specific character should be rendered (notably this 2569 applies to language- and culture-specific variations of Han 2570 ideographs as used in Japanese, Chinese, and Korean). When language 2571 tags are applied to spans of text, rendering engines sometimes use 2572 that information in deciding which font to use in the absence of 2573 other information, particularly where languages with distinct writing 2574 traditions use the same characters. 2576 8. Changes from RFC 4646 2578 The main goal for this revision of this document was to incorporate 2579 ISO 639-3 and its attendent set of language codes into the IANA 2580 Language Subtag Registry, permitting the identification of many more 2581 languages and dialects than previously supported. 2583 The specific changes in this document to meet these goals are: 2585 o Defines the incorporation of ISO 639-3 codes as language. It also 2586 permanently reserves and disallows the use of extlang subtags. 2587 The changes necessary to achieve this were: 2589 * something 2591 o Changed the ABNF related to grandfathered tags. The irregular 2592 tags are now listed. Well-formed grandfathered tags are now 2593 described by the 'langtag' production and the 'grandfathered' 2594 production was removed as a result. Also: added description of 2595 both types of grandfathered tags to Section 2.2.8. 2597 o Added the paragraph on "collections" to Section 4.1. 2599 o Changed the capitalization rules for 'Tag' fields in Section 3.1. 2601 o Split section 3.1 up into subsections. 2603 o Modified section 3.5 to allow Suppress-Script fields to be added, 2604 modified, or removed via the registration process. This was an 2605 erratum from RFC 4646. 2607 o Modified examples that used region code 'CS' (formerly Serbia and 2608 Montenegro) to use 'RS' (Serbia) instead. 2610 o Modified the rules for creating and maintaining record 2611 'Description' fields to prevent duplicates, including inverted 2612 duplicates. 2614 o Removed the lengthy description of why RFC 4646 was created from 2615 this section, which also caused the removal of the reference to 2616 XML Schema. 2618 o Modified the text in section 2.1 to place more emphasis on the 2619 fact that language tags are not case sensitive. 2621 o Replaced the example "fr-Latn-CA" in Section 2.1 with "sr-Latn-RS" 2622 and "az-Arab-IR" because "fr-Latn-CA" doesn't respect the 2623 Suppress-Script on 'Latn' with 'fr'. 2625 o Changed the requirements for well-formedness to make singleton 2626 repetition checking optional (it is required for validity 2627 checking) in Section 2.2.9. 2629 o Changed the text in Section 2.2.9 refering to grandfathered 2630 checking to note that the list is now included in the ABNF. 2632 o Modified and added text to Section 3.2. The job description was 2633 placed first. A note was added making clear that the Language 2634 Subtag Reviewer may delegate various non-critical duties, 2635 including list moderation. Finally, additional text was added to 2636 make the appointment process clear and to clarify that decisions 2637 and performance of the reviewer are appealable. 2639 o Added text to Section 3.5 clarifying that the ietf-languages list 2640 is operated by whomever the IESG appoints. 2642 o Added text to Section 3.1.4 clarifying that the first Description 2643 in a 'language' record matches the corresponding Reference Name 2644 for the language in ISO 639-3. 2646 o Modified Section 2.2.9 to define classes of conformance related to 2647 specific tags (formerly 'well-formed' and 'valid' referred to 2648 implementations). 2650 o Added text to the end of Section 3.1.2 noting that future versions 2651 of this document might add new field types and recommending that 2652 implementations ignore any unrecognized fields. 2654 o Added text about what the lack of a Suppress-Script field means in 2655 a record to Section 3.1.8. 2657 o Added text allowing the correction of misspellings and typographic 2658 errors to Section 3.1.4. 2660 o Added text to Section 3.1.7 disallowing Prefix field conflicts 2661 (such as circular prefix references). 2663 o Modified text in Section 3.5 to require the subtag reviewer to 2664 announce his/her decision (or extension) following the two-week 2665 period. Also clarified that any decision or failure to decide can 2666 be appealed. 2668 o Modified text in Section 4.1 to include the (heretofore anecdotal) 2669 guiding principle of tag choice, and clarifying the non-use of 2670 script subtags in non-written applications. Also updated examples 2671 in this section to use Chamic languages as an example of language 2672 collections. 2674 o Prohibited multiple use of the same variant in a tag (i.e. "de- 2675 1901-1901"). Previously this was only a recommendation 2676 ("SHOULD"). 2678 o Removed inappropriate [RFC2119] language from the illustration in 2679 Section 4.3.1. 2681 o Replaced the example of "zh-gouyu" with "zh-hakka"->"zh-hak" in 2682 Section 4.4, noting that it was this document that caused the 2683 change. 2685 o Replaced the section in Section 4.1 dealing with "mul"/"und" to 2686 include the subtags 'zxx' and 'mis', as well as the tag 2687 "i-default". A normative reference to RFC 2277 was added, along 2688 with an informative reference to MARC21. 2690 o Added text to Section 3.5 clarifying that any modifications of a 2691 registration request must be sent to the ietf-languages list 2692 before submission to IANA. 2694 o Changed the ABNF for the record-jar format from using the LWSP 2695 production to use a folding whitespace production similar to obs- 2696 FWS in [RFC4234]. This effectively prevents unintentional blank 2697 lines inside a field. 2699 o Clarified and revised text in Section 3.3, Section 3.5, and 2700 Section 5.1 to clarify that the Language Subtag Reviewer sends the 2701 complete registration forms to IANA, that IANA extracts the record 2702 from the form, and that the forms must also be archived separately 2703 from the registry. 2705 o Added text to Section 5 requiring IANA to send an announcement to 2706 an ietf-languages-announce list whenever the registry is updated. 2708 o Modification of the registry to use UTF-8 as its character 2709 encoding. This also entails additional instructions to IANA and 2710 the Language Subtag Reviewer in the registration process. 2712 o Modified the rules in Section 2.2.4 so that "exceptionally 2713 reserved" ISO 3166-1 codes other than 'UK' were included into the 2714 registry. In particular, this allows the code 'EU' (European 2715 Union) to be used to form language tags or (more commonly) for 2716 applications that use the registry for region codes to reference 2717 this subtag. 2719 [[Ed.Note: Open issues in this version: 2721 Inclusion of additional information related to Suppress-Script in 2722 the registry (e.g. that it wasn't assigned on purpose) 2724 ]] 2726 9. References 2728 9.1. Normative References 2730 [ISO15924] 2731 International Organization for Standardization, "ISO 2732 15924:2004. Information and documentation -- Codes for the 2733 representation of names of scripts", January 2004. 2735 [ISO3166-1] 2736 International Organization for Standardization, "ISO 3166- 2737 1:2006. Codes for the representation of names of countries 2738 and their subdivisions -- Part 1: Country codes", 2739 November 2006. 2741 [ISO639-1] 2742 International Organization for Standardization, "ISO 639- 2743 1:2002. Codes for the representation of names of languages 2744 -- Part 1: Alpha-2 code", 2002. 2746 [ISO639-2] 2747 International Organization for Standardization, "ISO 639- 2748 2:1998. Codes for the representation of names of languages 2749 -- Part 2: Alpha-3 code, first edition", 1998. 2751 [ISO639-3] 2752 International Organization for Standardization, "ISO 639- 2753 3:2007. Codes for the representation of names of languages 2754 -- Part 3: Alpha-3 code for comprehensive coverage of 2755 languages", 2007. 2757 [ISO646] International Organization for Standardization, "ISO/IEC 2758 646:1991, Information technology -- ISO 7-bit coded 2759 character set for information interchange.", 1991. 2761 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 2762 3", BCP 9, RFC 2026, October 1996. 2764 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 2765 the IETF Standards Process", BCP 11, RFC 2028, 2766 October 1996. 2768 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2769 Requirement Levels", BCP 14, RFC 2119, March 1997. 2771 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and 2772 Languages", BCP 18, RFC 2277, January 1998. 2774 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2775 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 2776 October 1998. 2778 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2779 Understanding Concerning the Technical Work of the 2780 Internet Assigned Numbers Authority", RFC 2860, June 2000. 2782 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2783 Timestamps", RFC 3339, July 2002. 2785 [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2786 Specifications: ABNF", RFC 4234, October 2005. 2788 [RFC4645] Ewell, D., Ed., "Initial Language Subtag Registry", 2789 September 2006, . 2791 [RFC4647] Phillips, A., Ed. and M. Davis, Ed., "Matching of Language 2792 Tags", September 2006, 2793 . 2795 [UN_M.49] Statistics Division, United Nations, "Standard Country or 2796 Area Codes for Statistical Use", UN Standard Country or 2797 Area Codes for Statistical Use, Revision 4 (United Nations 2798 publication, Sales No. 98.XVII.9, June 1999. 2800 9.2. Informative References 2802 [RFC1766] Alvestrand, H., "Tags for the Identification of 2803 Languages", RFC 1766, March 1995. 2805 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 2806 Part Three: Message Header Extensions for Non-ASCII Text", 2807 RFC 2047, November 1996. 2809 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 2810 Word Extensions: Character Sets, Languages, and 2811 Continuations", RFC 2231, November 1997. 2813 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 2814 10646", RFC 2781, February 2000. 2816 [RFC3066] Alvestrand, H., "Tags for the Identification of 2817 Languages", BCP 47, RFC 3066, January 2001. 2819 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2820 Text on Security Considerations", BCP 72, RFC 3552, 2821 July 2003. 2823 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 2824 10646", STD 63, RFC 3629, November 2003. 2826 [RFC4646] Phillips, A., Ed. and M. Davis, Ed., "Tags for the 2827 Identification of Languages", September 2006, 2828 . 2830 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 2831 Standard, Version 5.0, (Boston, MA, Addison-Wesley, 2003. 2832 ISBN 0-321-49081-0)", January 2007. 2834 [iso639.prin] 2835 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2836 Committee: Working principles for ISO 639 maintenance", 2837 March 2000, 2838 . 2841 [record-jar] 2842 Raymond, E., "The Art of Unix Programming", 2003, 2843 . 2845 [registry-update] 2846 Ewell, D., Ed., "Update to the Language Subtag Registry", 2847 September 2006, . 2850 Appendix A. Acknowledgements 2852 Any list of contributors is bound to be incomplete; please regard the 2853 following as only a selection from the group of people who have 2854 contributed to make this document what it is today. 2856 The contributors to RFC 4646, RFC 4647, RFC 3066, and RFC 1766, the 2857 precursors of this document, made enormous contributions directly or 2858 indirectly to this document and are generally responsible for the 2859 success of language tags. 2861 The following people contributed to this document: 2863 Stephane Bortzmeyer, Karen Broome, Peter Constable, John Cowan, 2864 Martin Duerst, Frank Ellerman, Doug Ewell, Deborah Garside, Marion 2865 Gunn, Kent Karlsson, Chris Newman, Randy Presuhn, Stephen Silver, and 2866 many, many others. 2868 Very special thanks must go to Harald Tveit Alvestrand, who 2869 originated RFCs 1766 and 3066, and without whom this document would 2870 not have been possible. 2872 Special thanks go to Michael Everson, who served as the Language Tag 2873 Reviewer for almost the entire RFC 1766/RFC 3066 period, as well as 2874 the Language Subtag Reviewer since the adoption of RFC 4646. 2876 Special thanks also to Doug Ewell, for his production of the first 2877 complete subtag registry, his work to support and maintain new 2878 registrations, and his careful editorship of both RFC 4645 and 2879 [registry-update]. 2881 Appendix B. Examples of Language Tags (Informative) 2883 Simple language subtag: 2885 de (German) 2887 fr (French) 2889 ja (Japanese) 2891 i-enochian (example of a grandfathered tag) 2893 Language subtag plus Script subtag: 2895 zh-Hant (Chinese written using the Traditional Chinese script) 2897 zh-Hans (Chinese written using the Simplified Chinese script) 2899 sr-Cyrl (Serbian written using the Cyrillic script) 2901 sr-Latn (Serbian written using the Latin script) 2903 Language-Script-Region: 2905 zh-Hans-CN (Chinese written using the Simplified script as used in 2906 mainland China) 2908 sr-Latn-RS (Serbian written using the Latin script as used in 2909 Serbia) 2911 Language-Variant: 2913 sl-rozaj (Resian dialect of Slovenian) 2915 sl-nedis (Nadiza dialect of Slovenian) 2917 Language-Region-Variant: 2919 de-CH-1901 (German as used in Switzerland using the 1901 variant 2920 [orthography]) 2922 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 2924 Language-Script-Region-Variant: 2926 hy-Latn-IT-arevela (Eastern Armenian written in Latin script, as 2927 used in Italy) 2929 Language-Region: 2931 de-DE (German for Germany) 2933 en-US (English as used in the United States) 2935 es-419 (Spanish appropriate for the Latin America and Caribbean 2936 region using the UN region code) 2938 Private use subtags: 2940 de-CH-x-phonebk 2942 az-Arab-x-AZE-derbend 2944 Private use registry values: 2946 x-whatever (private use using the singleton 'x') 2948 qaa-Qaaa-QM-x-southern (all private tags) 2950 de-Qaaa (German, with a private script) 2952 sr-Latn-QM (Serbian, Latin-script, private region) 2954 sr-Qaaa-RS (Serbian, private script, for Serbia) 2956 Tags that use extensions (examples ONLY: extensions MUST be defined 2957 by revision or update to this document or by RFC): 2959 en-US-u-islamCal 2961 zh-CN-a-myExt-x-private 2963 en-a-myExt-b-another 2965 Some Invalid Tags: 2967 de-419-DE (two region tags) 2969 a-DE (use of a single-character subtag in primary position; note 2970 that there are a few grandfathered tags that start with "i-" that 2971 are valid) 2972 ar-a-aaa-b-bbb-a-ccc (two extensions with same single-letter 2973 prefix) 2975 Appendix C. Examples of Registration Forms 2976 LANGUAGE SUBTAG REGISTRATION FORM 2977 1. Name of requester: Han Steenwijk 2978 2. E-mail address of requester: han.steenwijk @ unipd.it 2979 3. Record Requested: 2981 Type: variant 2982 Subtag: biske 2983 Description: The San Giorgio dialect of Resian 2984 Description: The Bila dialect of Resian 2985 Prefix: sl-rozaj 2986 Comments: The dialect of San Giorgio/Bila is one of the 2987 four major local dialects of Resian 2989 4. Intended meaning of the subtag: The local variety of Resian as 2990 spoken in San Giorgio/Bila 2992 5. Reference to published description of the language (book or 2993 article): 2994 -- Jan I.N. Baudouin de Courtenay - Opyt fonetiki rez'janskich 2995 govorov, Varsava - Peterburg: Vende - Kozancikov, 1875. 2997 LANGUAGE SUBTAG REGISTRATION FORM 2998 1. Name of requester: Jaska Zedlik 2999 2. E-mail address of requester: jz53 @ zedlik.com 3000 3. Record Requested: 3002 Type: variant 3003 Subtag: tarask 3004 Description: Belarusian in Taraskievica orthography 3005 Prefix: be 3006 Comments: The subtag represents Branislau Taraskievic's Belarusian 3007 orthography as published in "Bielaruski klasycny pravapis" by Juras 3008 Buslakou, Vincuk Viacorka, Zmicier Sanko, and Zmicier Sauka 3009 (Vilnia-Miensk 2005). 3011 4. Intended meaning of the subtag: 3013 The subtag is intended to represent the Belarusian orthography as 3014 published in "Bielaruski klasycny pravapis" by Juras Buslakou, Vincuk 3015 Viacorka, Zmicier Sanko, and Zmicier Sauka (Vilnia-Miensk 2005). 3017 5. Reference to published description of the language (book or article): 3019 Taraskievic, Branislau. Bielaruskaja gramatyka dla skol. Vilnia: Vyd. 3020 "Bielaruskaha kamitetu", 1929, 5th edition. 3022 Buslakou, Juras; Viacorka, Vincuk; Sanko, Zmicier; Sauka, Zmicier. 3023 Bielaruski klasycny pravapis. Vilnia-Miensk, 2005. 3025 6. Any other relevant information: 3027 Belarusian in Taraskievica orthography became widely used, especially in 3028 Belarusian-speaking Internet segment, but besides this some books and 3029 newspapers are also printed using this orthography of Belarusian. 3031 Authors' Addresses 3033 Addison Phillips (editor) 3034 Yahoo! Inc. 3036 Email: addison@inter-locale.com 3037 URI: http://www.inter-locale.com 3039 Mark Davis (editor) 3040 Google 3042 Email: mark.davis@macchiato.com or mark.davis@google.com 3044 Full Copyright Statement 3046 Copyright (C) The IETF Trust (2007). 3048 This document is subject to the rights, licenses and restrictions 3049 contained in BCP 78, and except as set forth therein, the authors 3050 retain all their rights. 3052 This document and the information contained herein are provided on an 3053 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 3054 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 3055 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 3056 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 3057 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 3058 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 3060 Intellectual Property 3062 The IETF takes no position regarding the validity or scope of any 3063 Intellectual Property Rights or other rights that might be claimed to 3064 pertain to the implementation or use of the technology described in 3065 this document or the extent to which any license under such rights 3066 might or might not be available; nor does it represent that it has 3067 made any independent effort to identify any such rights. Information 3068 on the procedures with respect to rights in RFC documents can be 3069 found in BCP 78 and BCP 79. 3071 Copies of IPR disclosures made to the IETF Secretariat and any 3072 assurances of licenses to be made available, or the result of an 3073 attempt made to obtain a general license or permission for the use of 3074 such proprietary rights by implementers or users of this 3075 specification can be obtained from the IETF on-line IPR repository at 3076 http://www.ietf.org/ipr. 3078 The IETF invites any interested party to bring to its attention any 3079 copyrights, patents or patent applications, or other proprietary 3080 rights that may cover technology that may be required to implement 3081 this standard. Please address the information to the IETF at 3082 ietf-ipr@ietf.org. 3084 Acknowledgment 3086 Funding for the RFC Editor function is provided by the IETF 3087 Administrative Support Activity (IASA).