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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: The tags and their subtags, including private-use and extensions, are to be treated as case insensitive: there exist conventions for the capitalization of some of the subtags, but these MUST not be taken to carry meaning. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). Found 'MAY NOT' in this paragraph: Note that 'Preferred-Value' mappings in records of type 'region' MAY NOT represent exactly the same meaning as the original value. 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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC1766' is defined on line 2375, but no explicit reference was found in the text -- 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. 'ISO15924' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO3166' -- Possible downref: Non-RFC (?) normative reference: ref. 'ISO10646' ** 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 2781 ** Downref: Normative reference to an Informational RFC: RFC 2860 -- 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) Summary: 7 errors (**), 0 flaws (~~), 12 warnings (==), 14 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Phillips, Ed. 3 Internet-Draft Quest Software 4 Expires: December 30, 2005 M. Davis, Ed. 5 IBM 6 June 28, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-08 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on December 30, 2005. 36 Copyright Notice 38 Copyright (C) The Internet Society (2005). 40 Abstract 42 This document describes the structure, content, construction, and 43 semantics of language tags for use in cases where it is desirable to 44 indicate the language used in an information object. It also 45 describes how to register values for use in language tags and the 46 creation of user defined extensions for private interchange. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4 52 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4 53 2.2 Language Subtag Sources and Interpretation . . . . . . . . 6 54 2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 7 55 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 9 56 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 10 57 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 11 58 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 13 59 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 14 60 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 15 61 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 15 62 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 16 63 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 18 64 3.1 Format of the IANA Language Subtag Registry . . . . . . . 18 65 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 23 66 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 25 67 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 28 68 3.5 Possibilities for Registration . . . . . . . . . . . . . . 31 69 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 33 70 3.7 Initialization of the Registry . . . . . . . . . . . . . . 36 71 4. Formation and Processing of Language Tags . . . . . . . . . . 37 72 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 37 73 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 39 74 4.3 Length Considerations . . . . . . . . . . . . . . . . . . 40 75 4.3.1 Working with Limited Buffer Sizes . . . . . . . . . . 40 76 4.3.2 Truncation of Language Tags . . . . . . . . . . . . . 42 77 4.4 Canonicalization of Language Tags . . . . . . . . . . . . 42 78 4.5 Considerations for Private Use Subtags . . . . . . . . . . 44 79 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 80 5.1 Language Subtag Registry . . . . . . . . . . . . . . . . . 46 81 5.2 Extensions Registry . . . . . . . . . . . . . . . . . . . 47 82 6. Security Considerations . . . . . . . . . . . . . . . . . . . 48 83 7. Character Set Considerations . . . . . . . . . . . . . . . . . 49 84 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 50 85 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53 86 9.1 Normative References . . . . . . . . . . . . . . . . . . . 53 87 9.2 Informative References . . . . . . . . . . . . . . . . . . 54 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 55 89 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 56 90 B. Examples of Language Tags (Informative) . . . . . . . . . . . 57 91 Intellectual Property and Copyright Statements . . . . . . . . 60 93 1. Introduction 95 Human beings on our planet have, past and present, used a number of 96 languages. There are many reasons why one would want to identify the 97 language used when presenting or requesting information. 99 User's language preferences often need to be identified so that 100 appropriate processing can be applied. For example, the user's 101 language preferences in a Web browser can be used to select Web pages 102 appropriately. Language preferences can also be used to select among 103 tools (such as dictionaries) to assist in the processing or 104 understanding of content in different languages. 106 In addition, knowledge about the particular language used by some 107 piece of information content might be useful or even required by some 108 types of processing; for example spell-checking, computer-synthesized 109 speech, Braille transcription, or high-quality print renderings. 111 One means of indicating the language used is by labeling the 112 information content with an identifier or "tag". These tags can be 113 used to specify user preferences when selecting information content, 114 or for labeling additional attributes of content and associated 115 resources. 117 Tags can also be used to indicate additional language attributes of 118 content. For example, indicating specific information about the 119 dialect, writing system, or orthography used in a document or 120 resource may enable the user to obtain information in a form that 121 they can understand, or important in processing or rendering the 122 given content into an appropriate form or style. 124 This document specifies a particular identifier mechanism (the 125 language tag) and a registration function for values to be used to 126 form tags. It also defines a mechanism for private use values and 127 future extension. 129 This document replaces RFC 3066, which replaced RFC 1766. For a list 130 of changes in this document, see Section 8. 132 The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 133 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 134 document are to be interpreted as described in [RFC2119]. 136 2. The Language Tag 138 The language tag always defines a language as used (which includes 139 being spoken, written, signed, or otherwise signaled) by human 140 beings for communication of information to other human beings. 141 Computer languages such as programming languages are explicitly 142 excluded. 144 2.1 Syntax 146 The language tag is composed of one or more parts or "subtags". Each 147 subtag consists of a sequence of alpha-numeric characters. Subtags 148 are distinguished and separated from one another by a hyphen ("-", 149 ABNF %x2D). A language tag consists of a "primary language" subtag 150 and a (possibly empty) series of subsequent subtags, each of which 151 refines or narrows the range of language identified by the overall 152 tag. 154 Each type of subtag is distinguished by length, position in the tag, 155 and content: subtags can be recognized solely by these features. 156 This makes it possible to construct a parser that can extract and 157 assign some semantic information to the subtags, even if the specific 158 subtag values are not recognized. Thus a parser need not have an up- 159 to-date copy (or any copy at all) of the subtag registry to perform 160 most searching and matching operations. 162 The syntax of the language tag in ABNF [RFC2234bis] is: 164 Language-Tag = (lang 165 *3("-" extlang) 166 ["-" script] 167 ["-" region] 168 *("-" variant) 169 *("-" extension) 170 ["-" privateuse]) 171 / privateuse ; private-use tag 172 / grandfathered ; grandfathered registrations 174 lang = 2*4ALPHA ; shortest ISO 639 code 175 / registered-lang 176 extlang = 3ALPHA ; reserved for future use 177 script = 4ALPHA ; ISO 15924 code 178 region = 2ALPHA ; ISO 3166 code 179 / 3DIGIT ; UN country number 180 variant = 5*8alphanum ; registered variants 181 / ( DIGIT 3alphanum ) 182 extension = singleton 1*("-" (2*8alphanum)) 183 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 184 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 185 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 186 ; Single letters: x/X is reserved for private use 187 registered-lang = 4*8ALPHA ; registered language subtag 188 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 189 ; grandfathered registration 190 ; Note: i is the only singleton 191 ; that starts a grandfathered tag 192 alphanum = (ALPHA / DIGIT) ; letters and numbers 194 Figure 1: Language Tag ABNF 196 Note: There is a subtlety in the ABNF for 'variant': variants 197 starting with a digit MAY be four characters long, while those 198 starting with a letter MUST be at least five characters long. 200 All subtags have a maximum length of eight characters and whitespace 201 is not permitted in a language tag. For examples of language tags, 202 see Appendix B. 204 Note that although [RFC2234bis] refers to octets, the language tags 205 described in this document are sequences of characters from the US- 206 ASCII repertoire. Language tags MAY be used in documents and 207 applications that use other encodings, so long as these encompass the 208 US-ASCII repertoire. An example of this would be an XML document 209 that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 211 The tags and their subtags, including private-use and extensions, are 212 to be treated as case insensitive: there exist conventions for the 213 capitalization of some of the subtags, but these MUST not be taken to 214 carry meaning. 216 For example: 218 o [ISO639-1] recommends that language codes be written in lower case 219 ('mn' Mongolian). 221 o [ISO3166] recommends that country codes be capitalized ('MN' 222 Mongolia). 224 o [ISO15924] recommends that script codes use lower case with the 225 initial letter capitalized ('Cyrl' Cyrillic). 227 However, in the tags defined by this document, the uppercase US-ASCII 228 letters in the range 'A' through 'Z' are considered equivalent and 229 mapped directly to their US-ASCII lowercase equivalents in the range 230 'a' through 'z'. Thus the tag "mn-Cyrl-MN" is not distinct from "MN- 231 cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these 232 variations conveys the same meaning: Mongolian written in the 233 Cyrillic script as used in Mongolia. 235 2.2 Language Subtag Sources and Interpretation 237 The namespace of language tags and their subtags is administered by 238 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 239 the rules in Section 5 of this document. The registry maintained by 240 IANA is the source for valid subtags: other standards referenced in 241 this section provide the source material for that registry. 243 Terminology in this section: 245 o Tag or tags refers to a complete language tag, such as 246 "fr-Latn-CA". Examples of tags in this document are enclosed in 247 double-quotes ("en-US"). 249 o Subtag refers to a specific section of a tag, delimited by hyphen, 250 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 251 this document are enclosed in single quotes ('Latn'). 253 o Code or codes refers to values defined in external standards (and 254 which are used as subtags in this document). For example, 'Latn' 255 is an [ISO15924] script code which was used to define the 'Latn' 256 script subtag for use in a language tag. Examples of codes in 257 this document are enclosed in single quotes ('en', 'Latn'). 259 The definitions in this section apply to the various subtags within 260 the language tags defined by this document, excepting those 261 "grandfathered" tags defined in Section 2.2.8. 263 Language tags are designed so that each subtag type has unique length 264 and content restrictions. These make identification of the subtag's 265 type possible, even if the content of the subtag itself is 266 unrecognized. This allows tags to be parsed and processed without 267 reference to the latest version of the underlying standards or the 268 IANA registry and makes the associated exception handling when 269 parsing tags simpler. 271 Subtags in the IANA registry that do not come from an underlying 272 standard can only appear in specific positions in a tag. 273 Specifically, they can only occur as primary language subtags or as 274 variant subtags. 276 Note that sequences of private-use and extension subtags MUST occur 277 at the end of the sequence of subtags and MUST NOT be interspersed 278 with subtags defined elsewhere in this document. 280 Single letter and digit subtags are reserved for current or future 281 use. These include the following current uses: 283 o The single letter subtag 'x' is reserved to introduce a sequence 284 of private-use subtags. The interpretation of any private-use 285 subtags is defined solely by private agreement and is not defined 286 by the rules in this section or in any standard or registry 287 defined in this document. 289 o All other single letter subtags are reserved to introduce 290 standardized extension subtag sequences as described in 291 Section 3.6. 293 The single letter subtag 'i' is used by some grandfathered tags, such 294 as "i-enochian", where it always appears in the first position and 295 cannot be confused with an extension. 297 2.2.1 Primary Language Subtag 299 The primary language subtag is the first subtag in a language tag 300 (with the exception of private-use and certain grandfathered tags) 301 and cannot be omitted. The following rules apply to the primary 302 language subtag: 304 1. All two character language subtags were defined in the IANA 305 registry according to the assignments found in the standard ISO 306 639 Part 1, "ISO 639-1:2002, Codes for the representation of 307 names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using 308 assignments subsequently made by the ISO 639 Part 1 maintenance 309 agency or governing standardization bodies. 311 2. All three character language subtags were defined in the IANA 312 registry according to the assignments found in ISO 639 Part 2, 313 "ISO 639-2:1998 - Codes for the representation of names of 314 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2], or 315 assignments subsequently made by the ISO 639 Part 2 maintenance 316 agency or governing standardization bodies. 318 3. The subtags in the range 'qaa' through 'qtz' are reserved for 319 private use in language tags. These subtags correspond to codes 320 reserved by ISO 639-2 for private use. These codes MAY be used 321 for non-registered primary-language subtags (instead of using 322 private-use subtags following 'x-'). Please refer to Section 4.5 323 for more information on private use subtags. 325 4. All four character language subtags are reserved for possible 326 future standardization. 328 5. All language subtags of 5 to 8 characters in length in the IANA 329 registry were defined via the registration process in Section 3.4 330 and MAY be used to form the primary language subtag. At the time 331 this document was created, there were no examples of this kind of 332 subtag and future registrations of this type will be discouraged: 333 primary languages are strongly RECOMMENDED for registration with 334 ISO 639 and proposals rejected by ISO 639/RA will be closely 335 scrutinized before they are registered with IANA. 337 6. The single character subtag 'x' as the primary subtag indicates 338 that the language tag consists solely of subtags whose meaning is 339 defined by private agreement. For example, in the tag "x-fr-CH", 340 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 341 French language or the country of Switzerland (or any other value 342 in the IANA registry) unless there is a private agreement in 343 place to do so. See Section 4.5. 345 7. The single character subtag 'i' is used by some grandfathered 346 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 347 grandfathered tags have a primary language subtag in their first 348 position) 350 8. Other values MUST NOT be assigned to the primary subtag except by 351 revision or update of this document. 353 Note: For languages that have both an ISO 639-1 two character code 354 and an ISO 639-2 three character code, only the ISO 639-1 two 355 character code is defined in the IANA registry. 357 Note: For languages that have no ISO 639-1 two character code and for 358 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 359 (Bibliographic) codes differ, only the Terminology code is defined in 360 the IANA registry. At the time this document was created, all 361 languages that had both kinds of three character code were also 362 assigned a two character code; it is not expected that future 363 assignments of this nature will occur. 365 Note: To avoid problems with versioning and subtag choice as 366 experienced during the transition between RFC 1766 and RFC 3066, as 367 well as the canonical nature of subtags defined by this document, the 368 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 369 RA-JAC) has included the following statement in [iso639.principles]: 371 "A language code already in ISO 639-2 at the point of freezing ISO 372 639-1 shall not later be added to ISO 639-1. This is to ensure 373 consistency in usage over time, since users are directed in Internet 374 applications to employ the alpha-3 code when an alpha-2 code for that 375 language is not available." 377 In order to avoid instability of the canonical form of tags, if a two 378 character code is added to ISO 639-1 for a language for which a three 379 character code was already included in ISO 639-2, the two character 380 code will not be added as a subtag in the registry. See Section 3.3. 382 For example, if some content were tagged with 'haw' (Hawaiian), which 383 currently has no two character code, the tag would not be invalidated 384 if ISO 639-1 were to assign a two character code to the Hawaiian 385 language at a later date. 387 For example, one of the grandfathered IANA registrations is 388 "i-enochian". The subtag 'enochian' could be registered in the IANA 389 registry as a primary language subtag (assuming that ISO 639 does not 390 register this language first), making tags such as "enochian-AQ" and 391 "enochian-Latn" valid. 393 2.2.2 Extended Language Subtags 395 The following rules apply to the extended language subtags: 397 1. Three letter subtags immediately following the primary subtag are 398 reserved for future standardization, anticipating work that is 399 currently under way on ISO 639. 401 2. Extended language subtags MUST follow the primary subtag and 402 precede any other subtags. 404 3. There MAY be up to three extended language subtags. 406 4. Extended language subtags MUST NOT be registered or used to form 407 language tags. Their syntax is described here so that 408 implementations can be compatible with any future revision of 409 this document which does provide for their registration. 411 Extended language subtag records, once they appear in the registry, 412 MUST include exactly one 'Prefix' field indicating an appropriate 413 language subtag or sequence of subtags that MUST always appear as a 414 prefix to the extended language subtag. 416 Example: In a future revision or update of this document, the tag 417 "zh-gan" (registered under RFC 3066) might become a valid non- 418 grandfathered (that is, redundant) tag in which the subtag 'gan' 419 might represent the Chinese dialect 'Gan'. 421 2.2.3 Script Subtag 423 Script subtags are used to indicate the script or writing system 424 variations that distinguish the written forms of a language or its 425 dialects. The following rules apply to the script subtags: 427 1. All four character subtags were defined according to 428 [ISO15924]--"Codes for the representation of the names of 429 scripts": alpha-4 script codes, or subsequently assigned by the 430 ISO 15924 maintenance agency or governing standardization bodies, 431 denoting the script or writing system used in conjunction with 432 this language. 434 2. Script subtags MUST immediately follow the primary language 435 subtag and all extended language subtags and MUST occur before 436 any other type of subtag described below. 438 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 439 use in language tags. These subtags correspond to codes reserved 440 by ISO 15924 for private use. These codes MAY be used for non- 441 registered script values. Please refer to Section 4.5 for more 442 information on private-use subtags. 444 4. Script subtags cannot be registered using the process in 445 Section 3.4 of this document. Variant subtags MAY be considered 446 for registration for that purpose. 448 5. There MUST be at most one script subtag in a language tag and the 449 script subtag SHOULD be omitted when it adds no distinguishing 450 value to the tag or when the primary language subtag's record 451 includes a Supress-Script field listing the applicable script 452 subtag. 454 Example: "sr-Latn" represents Serbian written using the Latin script. 456 2.2.4 Region Subtag 458 Region subtags are used to indicate linguistic variations associated 459 with or appropriate to a specific country, territory, or region. 460 Typically, a region subtag is used to indicate regional dialects or 461 usage, or region-specific spelling conventions. A region subtag can 462 also be used to indicate that content is expressed in a way that is 463 appropriate for use throughout a region; for instance, Spanish 464 content tailored to be useful throughout Latin America. 466 The following rules apply to the region subtags: 468 1. Region subtags MUST follow any language, extended language, or 469 script subtags and MUST precede all other subtags. 471 2. All two character subtags following the primary subtag were 472 defined in the IANA registry according to the assignments found 473 in [ISO3166]--"Codes for the representation of names of countries 474 and their subdivisions - Part 1: Country codes"--alpha-2 country 475 codes or assignments subsequently made by the ISO 3166 476 maintenance agency or governing standardization bodies. 478 3. All three character subtags consisting of digit (numeric) 479 characters following the primary subtag were defined in the IANA 480 registry according to the assignments found in UN Standard 481 Country or Area Codes for Statistical Use [UN_M.49] or 482 assignments subsequently made by the governing standards body. 483 Note that not all of the UN M.49 codes are defined in the IANA 484 registry. The following rules define which codes are entered 485 into the registry as valid subtags: 487 A. UN numeric codes assigned to 'macro-geographical 488 (continental)' or sub-regions MUST be registered in the 489 registry. These codes are not associated with an assigned 490 ISO 3166 alpha-2 code and represent supra-national areas, 491 usually covering more than one nation, state, province, or 492 territory. 494 B. UN numeric codes for 'economic groupings' or 'other 495 groupings' MUST NOT be registered in the IANA registry and 496 MUST NOT be used to form language tags. 498 C. UN numeric codes for countries or areas with ambiguous ISO 499 3166 alpha-2 codes, when entered into the registry, MUST be 500 defined according to the rules in Section 3.3 and MUST be 501 used to form language tags that represent the country or 502 region for which they are defined. 504 D. UN numeric codes for countries or areas for which there is an 505 associated ISO 3166 alpha-2 code in the registry MUST NOT be 506 entered into the registry and MUST NOT be used to form 507 language tags. Note that the ISO 3166-based subtag in the 508 registry MUST actually be associated with the UN M.49 code in 509 question. 511 E. UN numeric codes and ISO 3166 alpha-2 codes for countries or 512 areas listed as eligible for registration in [initial- 513 registry] but not presently registered MAY be entered into 514 the IANA registry via the process described in Section 3.4. 515 Once registered, these codes MAY be used to form language 516 tags. 518 F. All other UN numeric codes for countries or areas which do 519 not have an associated ISO 3166 alpha-2 code MUST NOT be 520 entered into the registry and MUST NOT be used to form 521 language tags. For more information about these codes, see 522 Section 3.3. 524 4. Note: The alphanumeric codes in Appendix X of the UN document 525 MUST NOT be entered into the registry and MUST NOT be used to 526 form language tags. (At the time this document was created these 527 values match the ISO 3166 alpha-2 codes.) 529 5. There MUST be at most one region subtag in a language tag and the 530 region subtag MAY be omitted, as when it adds no distinguishing 531 value to the tag. 533 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 534 reserved for private use in language tags. These subtags 535 correspond to codes reserved by ISO 3166 for private use. These 536 codes MAY be used for private use region subtags (instead of 537 using a private-use subtag sequence). Please refer to 538 Section 4.5 for more information on private use subtags. 540 "de-CH" represents German ('de') as used in Switzerland ('CH'). 542 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 543 ('Latn') as used in Serbia and Montenegro ('CS'). 545 "es-419" represents Spanish ('es') appropriate to the UN-defined 546 Latin America and Caribbean region ('419'). 548 2.2.5 Variant Subtags 550 Variant subtags are used to indicate additional, well-recognized 551 variations that define a language or its dialects which are not 552 covered by other available subtags. The following rules apply to the 553 variant subtags: 555 1. Variant subtags are not associated with any external standard. 556 Variant subtags and their meanings are defined by the 557 registration process defined in Section 3.4. 559 2. Variant subtags MUST follow all of the other defined subtags, but 560 precede any extension or private-use subtag sequences. 562 3. More than one variant MAY be used to form the language tag. 564 4. Variant subtags MUST be registered with IANA according to the 565 rules in Section 3.4 of this document before being used to form 566 language tags. In order to distinguish variants from other types 567 of subtags, registrations MUST meet the following length and 568 content restrictions: 570 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 571 at least five characters long. 573 2. Variant subtags that begin with a digit (0-9) MUST be at 574 least four characters long. 576 Variant subtag records in the language subtag registry MAY include 577 one or more 'Prefix' fields, which indicates the language tag or tags 578 that would make a suitable prefix (with other subtags, as 579 appropriate) in forming a language tag with the variant. For 580 example, the subtag 'nedis' has a Prefix of "sl", making it suitable 581 to form language tags such as "sl-nedis" and "sl-IT-nedis", but not 582 suitable for use in a tag such as "zh-nedis" or "it-IT-nedis". 584 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 586 "de-CH-1996" represents German as used in Switzerland and as written 587 using the spelling reform beginning in the year 1996 C.E. 589 Most variants that share a prefix are mutually exclusive. For 590 example, the German orthographic variations '1996' and '1901' SHOULD 591 NOT be used in the same tag, as they represent the dates of different 592 spelling reforms. A variant that can meaningfully be used in 593 combination with another variant SHOULD include a 'Prefix' field in 594 its registry record that lists that other variant. For example, if 595 another German variant 'example' were created that made sense to use 596 with '1996', then 'example' should include two Prefix fields: "de" 597 and "de-1996". 599 2.2.6 Extension Subtags 601 Extensions provide a mechanism for extending language tags for use in 602 various applications. See: Section 3.6. The following rules apply 603 to extensions: 605 1. Extension subtags are separated from the other subtags defined 606 in this document by a single-letter subtag ("singleton"). The 607 singleton MUST be one allocated to a registration authority via 608 the mechanism described in Section 3.6 and cannot be the letter 609 'x', which is reserved for private-use subtag sequences. 611 2. Note: Private-use subtag sequences starting with the singleton 612 subtag 'x' are described below. 614 3. An extension MUST follow at least a primary language subtag. 615 That is, a language tag cannot begin with an extension. 616 Extensions extend language tags, they do not override or replace 617 them. For example, "a-value" is not a well-formed language tag, 618 while "de-a-value" is. 620 4. Each singleton subtag MUST appear at most one time in each tag 621 (other than as a private-use subtag). That is, singleton 622 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 623 ccc" is invalid because the subtag 'a' appears twice. Note that 624 the tag "en-a-bbb-x-a-ccc" is valid because the second 625 appearance of the singleton 'a' is in a private use sequence. 627 5. Extension subtags MUST meet all of the requirements for the 628 content and format of subtags defined in this document. 630 6. Extension subtags MUST meet whatever requirements are set by the 631 document that defines their singleton prefix and whatever 632 requirements are provided by the maintaining authority. 634 7. Each extension subtag MUST be from two to eight characters long 635 and consist solely of letters or digits, with each subtag 636 separated by a single '-'. 638 8. Each singleton MUST be followed by at least one extension 639 subtag. For example, the tag "tlh-a-b-foo" is invalid because 640 the first singleton 'a' is followed immediately by another 641 singleton 'b'. 643 9. Extension subtags MUST follow all language, extended language, 644 script, region and variant subtags in a tag. 646 10. All subtags following the singleton and before another singleton 647 are part of the extension. Example: In the tag "fr-a-Latn", the 648 subtag 'Latn' does not represent the script subtag 'Latn' 649 defined in the IANA Language Subtag Registry. Its meaning is 650 defined by the extension 'a'. 652 11. In the event that more than one extension appears in a single 653 tag, the tag SHOULD be canonicalized as described in 654 Section 4.4. 656 For example, if the prefix singleton 'r' and the shown subtags were 657 defined, then the following tag would be a valid example: "en-Latn- 658 GB-boont-r-extended-sequence-x-private" 660 2.2.7 Private Use Subtags 662 Private use subtags are used to indicate distinctions in language 663 important in a given context by private agreement. The following 664 rules apply to private-use subtags: 666 1. Private-use subtags are separated from the other subtags defined 667 in this document by the reserved single-character subtag 'x'. 669 2. Private-use subtags MUST follow all language, extended language, 670 script, region, variant, and extension subtags in the tag. 671 Another way of saying this is that all subtags following the 672 singleton 'x' MUST be considered private use. Example: The 673 subtag 'US' in the tag "en-x-US" is a private use subtag. 675 3. A tag MAY consist entirely of private-use subtags. 677 4. No source is defined for private use subtags. Use of private use 678 subtags is by private agreement only. 680 For example: Users who wished to utilize SIL Ethnologue for 681 identification might agree to exchange tags such as "az-Arab-x-AZE- 682 derbend". This example contains two private-use subtags. The first 683 is 'AZE' and the second is 'derbend'. 685 2.2.8 Pre-Existing RFC 3066 Registrations 687 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 688 maintain their validity. IANA will maintain these tags in the 689 registry under either the "grandfathered" or "redundant" type. For 690 more information see Section 3.7. 692 It is important to note that all language tags formed under the 693 guidelines in this document were either legal, well-formed tags or 694 could have been registered under RFC 3066. 696 2.2.9 Classes of Conformance 698 Implementations sometimes need to describe their capabilities with 699 regard to the rules and practices described in this document. There 700 are two classes of conforming implementations described by this 701 document: "well-formed" processors and "validating" processors. 702 Claims of conformance SHOULD explicitly reference one of these 703 definitions. 705 An implementation that claims to check for well-formed language tags 706 MUST: 708 o Check that the tag and all of its subtags, including extension and 709 private-use subtags, conform to the ABNF or that the tag is on the 710 list of grandfathered tags. 712 o Check that singleton subtags that identify extensions do not 713 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 714 formed. 716 Well-formed processors are strongly encouraged to implement the 717 canonicalization rules contained in Section 4.4. 719 An implementation that claims to be validating MUST: 721 o Check that the tag is well-formed. 723 o Specify the particular registry date for which the implementation 724 performs validation of subtags. 726 o Check that either the tag is a grandfathered tag, or that all 727 language, script, region, and variant subtags consist of valid 728 codes for use in language tags according to the IANA registry as 729 of the particular date specified by the implementation. 731 o Specify which, if any, extension RFCs as defined in Section 3.6 732 are supported, including version, revision, and date. 734 o For any such extensions supported, check that all subtags used in 735 that extension are valid. 737 o For variant and extended language subtags, if the registry 738 contains one or more 'Prefix' fields for that subtag, check that 739 the tag matches at least one prefix. The tag matches if all the 740 subtags in the 'Prefix' also appear in the tag. For example, the 741 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 742 the 'es' language subtag and 'CO' region subtag appear in the tag. 744 3. Registry Format and Maintenance 746 This section defines the Language Subtag Registry and the maintenance 747 and update procedures associated with it. 749 The language subtag registry will be maintained so that, except for 750 extension subtags, it is possible to validate all of the subtags that 751 appear in a language tag under the provisions of this document or its 752 revisions or successors. In addition, the meaning of the various 753 subtags will be unambiguous and stable over time. (The meaning of 754 private-use subtags, of course, is not defined by the IANA registry.) 756 The registry defined under this document contains a comprehensive 757 list of all of the subtags valid in language tags. This allows 758 implementers a straightforward and reliable way to validate language 759 tags. 761 3.1 Format of the IANA Language Subtag Registry 763 The IANA Language Subtag Registry ("the registry") will consist of a 764 text file that is machine readable in the format described in this 765 section, plus copies of the registration forms approved by the 766 Language Subtag Reviewer in accordance with the process described in 767 Section 3.4. With the exception of the registration forms for 768 grandfathered and redundant tags, no registration records will be 769 maintained for the initial set of subtags. 771 The registry will be in a modified record-jar format text file 772 [record-jar]. Lines are limited to 72 characters, including all 773 whitespace. 775 Records are separated by lines containing only the sequence "%%" 776 (%x25.25). 778 Each field can be viewed as a single, logical line of ASCII 779 characters, comprising a field-name and a field-body separated by a 780 COLON character (%x3A). For convenience, the field-body portion of 781 this conceptual entity can be split into a multiple-line 782 representation; this is called "folding". The format of the registry 783 is described by the following ABNF (per [RFC2234bis]): 785 registry = record *("%%" CRLF record) 786 record = 1*( field-name *SP ":" *SP field-body CRLF ) 787 field-name = *(ALPHA / DIGIT / "-") 788 field-body = *(ASCCHAR/LWSP) 789 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 790 UNICHAR = "&#x" 2*6HEXDIG ";" 791 The sequence '..' (%x2E.2E) in a field-body denotes a range of 792 values. Such a range represents all subtags of the same length that 793 are alphabetically within that range, including the values explicitly 794 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 796 Characters from outside the US-ASCII repertoire, as well as the 797 AMPERSAND character ("&", %x26) when it occurs in a field-body are 798 represented by a "Numeric Character Reference" using hexadecimal 799 notation in the style used by [XML10] (see 800 ). This consists of the 801 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 802 of the character's code point in [ISO10646] followed by a closing 803 semicolon (%x3B). For example, the EURO SIGN, U+20AC, would be 804 represented by the sequence "€". Note that the hexadecimal 805 notation MAY have between two and six digits. 807 All fields whose field-body contains a date value use the "full-date" 808 format specified in [RFC3339]. For example: "2004-06-28" represents 809 June 28, 2004 in the Gregorian calendar. 811 The first record in the file contains the single field whose field- 812 name is "File-Date". The field-body of this record contains the last 813 modification date of this copy of the registry, making it possible to 814 compare different versions of the registry. The registry on the IANA 815 website is the most current. Versions with an older date than that 816 one are not up-to-date. 818 File-Date: 2004-06-28 819 %% 821 Subsequent records represent subtags in the registry. Each of the 822 fields in each record MUST occur no more than once, unless otherwise 823 noted below. Each record MUST contain the following fields: 825 o 'Type' 827 * Type's field-value MUST consist of one of the following 828 strings: "language", "extlang", "script", "region", "variant", 829 "grandfathered", and "redundant" and denotes the type of tag or 830 subtag. 832 o Either 'Subtag' or 'Tag' 834 * Subtag's field-value contains the subtag being defined. This 835 field MUST only appear in records of whose Type has one of 836 these values: "language", "extlang", "script", "region", or 837 "variant". 839 * Tag's field-value contains a complete language tag. This field 840 MUST only appear in records whose Type has one of these values: 841 "grandfathered" or "redundant". 843 o Description 845 * Description's field-value contains a non-normative description 846 of the subtag or tag. 848 o Added 850 * Added's field-value contains the date the record was added to 851 the registry. 853 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 854 subtag or tag, with two exceptions. Subtags whose 'Type' field is 855 'script' (in other words, subtags defined by ISO 15924) MUST use 856 titlecase. Subtags whose 'Type' field is 'region' (in other words, 857 subtags defined by ISO 3166) MUST use uppercase. These exceptions 858 mirror the use of case in the underlying standards. 860 The field 'Description' MAY appear more than one time. At least one 861 of the 'Description' fields MUST contain a description of the tag 862 being registered written or transcribed into the Latin script; the 863 same or additional fields MAY also include a description in a non- 864 Latin script. The 'Description' field is used for identification 865 purposes and SHOULD NOT be taken to represent the actual native name 866 of the language or variation or to be in any particular language. 867 Most descriptions are taken directly from source standards such as 868 ISO 639 or ISO 3166. 870 Note: Descriptions in registry entries that correspond to ISO 639, 871 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 872 the meaning of that identifier as defined in the source standard at 873 the time it was added to the registry. The description does not 874 replace the content of the source standard itself. The descriptions 875 are not intended to be the English localized names for the subtags. 876 Localization or translation of language tag and subtag descriptions 877 is out of scope of this document. 879 Each record MAY also contain the following fields: 881 o Preferred-Value 883 * For fields of type 'language', 'extlang', 'script', 'region', 884 and 'variant', 'Preferred-Value' contains a subtag of the same 885 'Type' which is preferred for forming the language tag. 887 * For fields of type 'grandfathered' and 'redundant', a canonical 888 mapping to a complete language tag. 890 o Deprecated 892 * Deprecated's field-value contains the date the record was 893 deprecated. 895 o Prefix 897 * Prefix's field-value contains a language tag with which this 898 subtag MAY be used to form a new language tag, perhaps with 899 other subtags as well. This field MUST only appear in records 900 whose 'Type' field-value is 'variant' or 'extlang'. For 901 example, the 'Prefix' for the variant 'nedis' is 'sl', meaning 902 that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate 903 while the tag "is-nedis" is not. 905 o Comments 907 * Comments contains additional information about the subtag, as 908 deemed appropriate for understanding the registry and 909 implementing language tags using the subtag or tag. 911 o Suppress-Script 913 * Suppress-Script contains a script subtag that SHOULD NOT be 914 used to form language tags with the associated primary language 915 subtag. This field MUST only appear in records whose 'Type' 916 field-value is 'language'. See Section 4.1. 918 The field 'Deprecated' MAY be added to any record via the maintenance 919 process described in Section 3.2 or via the registration process 920 described in Section 3.4. Usually the addition of a 'Deprecated' 921 field is due to the action of one of the standards bodies, such as 922 ISO 3166, withdrawing a code. In some historical cases it might not 923 have been possible to reconstruct the original deprecation date. 924 For these cases, an approximate date appears in the registry. 925 Although valid in language tags, subtags and tags with a 'Deprecated' 926 field are deprecated and validating processors SHOULD NOT generate 927 these subtags. Note that a record that contains a 'Deprecated' field 928 and no corresponding 'Preferred-Value' field has no replacement 929 mapping. 931 Thie field 'Preferred-Value' contains a mapping between the record in 932 which it appears and a tag or subtag which SHOULD be preferred when 933 selected language tags. These values form three groups: 935 ISO 639 language codes which were later withdrawn in favor of 936 other codes. These values are mostly a historical curiosity. 938 ISO 3166 region codes which have been withdrawn in favor of a new 939 code. This sometimes happens when a country changes its name or 940 administration in such a way that warrants a new region code. 942 Tags grandfathered from RFC 3066. In many cases these tags have 943 become obsolete because the values they represent were later 944 encoded by ISO 639. 946 Records that contain a 'Preferred-Value' field MUST also have a 947 'Deprecated' field. This field contains a date of deprecation. Thus 948 a language tag processor can use the registry to construct the valid, 949 non-deprecated set of subtags for a given date. In addition, for any 950 given tag, a processor can construct the set of valid language tags 951 that correspond to that tag for all dates up to the date of the 952 registry. The ability to do these mappings MAY be beneficial to 953 applications that are matching, selecting, for filtering content 954 based on its language tags. 956 Note that 'Preferred-Value' mappings in records of type 'region' MAY 957 NOT represent exactly the same meaning as the original value. There 958 are many reasons for a country code to be changed and the effect this 959 has on the formation of language tags will depend on the nature of 960 the change in question. 962 In particular, the 'Preferred-Value' field does not imply retagging 963 content that uses the affected subtag. 965 The field 'Preferred-Value' MUST NOT be modified once created in the 966 registry. The field MAY be added to records of type "grandfathered" 967 and "region" according to the rules in Section 3.2. Otherwise the 968 field MUST NOT be added to any record already in the registry. 970 The 'Preferred-Value' field in records of type "grandfathered" and 971 "redundant" contains whole language tags that are strongly 972 RECOMMENDED for use in place of the record's value. In many cases 973 the mappings were created by deprecation of the tags during the 974 period before this document was adopted. For example, the tag "no- 975 nyn" was deprecated in favor of the ISO 639-1 defined language code 976 'nn'. 978 Records of type 'variant' MAY have more than one field of type 979 'Prefix'. Additional fields of this type MAY be added to a 'variant' 980 record via the registration process. 982 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 984 The field-value of the 'Prefix' field consists of a language tag 985 whose subtags are appropriate to use with this subtag. For example, 986 the variant subtag '1996' has a Prefix field of "de". This means 987 that tags starting with the sequence "de-" are appropriate with this 988 subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while 989 the tag "fr-1996" is an inappropriate choice. 991 The field of type 'Prefix' MUST NOT be removed from any record. The 992 field-value for this type of field MUST NOT be modified. 994 The field 'Comments' MAY appear more than once per record. This 995 field MAY be inserted or changed via the registration process and no 996 guarantee of stability is provided. The content of this field is not 997 restricted, except by the need to register the information, the 998 suitability of the request, and by reasonable practical size 999 limitations. Long screeds about a particular subtag are frowned 1000 upon. 1002 The field 'Suppress-Script' MUST only appear in records whose 'Type' 1003 field-value is 'language'. This field MAY appear at most one time in 1004 a record. This field indicates a script used to write the 1005 overwhelming majority of documents for the given language and which 1006 therefore adds no distinguishing information to a language tag. It 1007 helps ensure greater compatibility between the language tags 1008 generated according to the rules in this document and language tags 1009 and tag processors or consumers based on RFC 3066. For example, 1010 virtually all Icelandic documents are written in the Latin script, 1011 making the subtag 'Latn' redundant in the tag "is-Latn". 1013 3.2 Maintenance of the Registry 1015 Maintenance of the registry requires that as codes are assigned or 1016 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1017 Subtag Reviewer will evaluate each change, determine whether it 1018 conflicts with existing registry entries, and submit the information 1019 to IANA for inclusion in the registry. If an change takes place and 1020 the Language Subtag Reviewer does not do this in a timely manner, 1021 then any interested party MAY use the procedure in Section 3.4 to 1022 register the appropriate update. 1024 Note: The redundant and grandfathered entries together are the 1025 complete list of tags registered under [RFC3066]. The redundant tags 1026 are those that can now be formed using the subtags defined in the 1027 registry together with the rules of Section 2.2. The grandfathered 1028 entries are those that can never be legal under those same 1029 provisions. 1031 The set of redundant and grandfathered tags is permanent and stable: 1033 no new entries will be added and none of the entries will be removed. 1034 Records of type 'grandfathered' MAY have their type converted to 1035 'redundant': see Section 3.7 for more information. 1037 RFC 3066 tags that were deprecated prior to the adoption of this 1038 document are part of the list of grandfathered tags and their 1039 component subtags were not included as registered variants (although 1040 they remain eligible for registration). For example, the tag "art- 1041 lojban" was deprecated in favor of the language subtag 'jbo'. 1043 The Language Subtag Reviewer MUST ensure that new subtags meet the 1044 requirements in Section 4.1 or submit an appropriate alternate subtag 1045 as described in that section. When either a change or addition to 1046 the registry is needed, the Language Subtag Reviewer MUST prepare the 1047 complete record, including all fields, and forward it to IANA for 1048 insertion into the registry. 1050 If record represents a new subtag that does not currently exist in 1051 the registry, then the message's subject line MUST include the word 1052 "INSERT". If the record represents a change to an existing subtag, 1053 then the subject line of the message MUST include the word "MODIFY". 1054 The message MUST contain both the record for the subtag being 1055 inserted or modified and the new File-Date record. Here is an 1056 example of what the body of the message might contain: 1058 LANGUAGE SUBTAG MODIFICATION 1059 File-Date: 2005-01-02 1060 %% 1061 Type: variant 1062 Subtag: nedis 1063 Description: Natisone dialect 1064 Description: Nadiza dialect 1065 Added: 2003-10-09 1066 Prefix: sl 1067 Comments: This is a comment shown 1068 as an example. 1069 %% 1071 Figure 4 1073 Whenever an entry is created or modified in the registry, the 'File- 1074 Date' record at the start of the registry is updated to reflect the 1075 most recent modification date in the [RFC3339] "full-date" format. 1077 Values in the 'Subtag' field MUST be lowercase except as provided for 1078 in Section 3.1. 1080 3.3 Stability of IANA Registry Entries 1082 The stability of entries and their meaning in the registry is 1083 critical to the long term stability of language tags. The rules in 1084 this section guarantee that a specific language tag's meaning is 1085 stable over time and will not change. 1087 These rules specifically deal with how changes to codes (including 1088 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1089 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1090 Subtag Registry. Assignments to the IANA Language Subtag Registry 1091 MUST follow the following stability rules: 1093 1. Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1094 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1095 guaranteed to be stable over time. 1097 2. Values in the 'Description' field MUST NOT be changed in a way 1098 that would invalidate previously-existing tags. They MAY be 1099 broadened somewhat in scope, changed to add information, or 1100 adapted to the most common modern usage. For example, countries 1101 occasionally change their official names: an historical example 1102 of this would be "Upper Volta" changing to "Burkina Faso". 1104 3. Values in the field 'Prefix' MAY be added to records of type 1105 'variant' via the registration process. 1107 4. Values in the field 'Prefix' MAY be modified, so long as the 1108 modifications broaden the set of prefixes. That is, a prefix 1109 MAY be replaced by one of its own prefixes. For example, the 1110 prefix "en-US" could be replaced by "en", but not by the 1111 prefixes "en-Latn", "fr", or "en-US-boont". If one of those 1112 prefixes were needed, a new Prefix SHOULD be registered. 1114 5. Values in the field 'Prefix' MUST NOT be removed. 1116 6. The field 'Comments' MAY be added, changed, modified, or removed 1117 via the registration process or any of the processes or 1118 considerations described in this section. 1120 7. The field 'Suppress-Script' MAY be added or removed via the 1121 registration process. 1123 8. Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1124 conflict with existing subtags of the associated type and whose 1125 meaning is not the same as an existing subtag of the same type 1126 are entered into the IANA registry as new records. 1128 9. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1129 withdrawn by their respective maintenance or registration 1130 authority remain valid in language tags. A 'Deprecated' field 1131 containing the date of withdrawal is added to the record. If a 1132 new record of the same type is added that represents a 1133 replacement value, then a 'Preferred-Value' field MAY also be 1134 added. The registration process MAY be used to add comments 1135 about the withdrawal of the code by the respective standard. 1137 1. The region code 'TL' was assigned to the country 'Timor- 1138 Leste', replacing the code 'TP' (which was assigned to 'East 1139 Timor' when it was under administration by Portugal). The 1140 subtag 'TP' remains valid in language tags, but its record 1141 contains the a 'Preferred-Value' of 'TL' and its field 1142 'Deprecated' contains the date the new code was assigned 1143 ('2004-07-06'). 1145 10. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1146 with existing subtags of the associated type, including subtags 1147 that are deprecated, MUST NOT be entered into the registry. The 1148 following additional considerations apply to subtag values that 1149 are reassigned: 1151 A. For ISO 639 codes, if the newly assigned code's meaning is 1152 not represented by a subtag in the IANA registry, the 1153 Language Subtag Reviewer, as described in Section 3.4, SHALL 1154 prepare a proposal for entering in the IANA registry as soon 1155 as practical a registered language subtag as an alternate 1156 value for the new code. The form of the registered language 1157 subtag will be at the discretion of the Language Subtag 1158 Reviewer and MUST conform to other restrictions on language 1159 subtags in this document. 1161 B. For all subtags whose meaning is derived from an external 1162 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), 1163 if a new meaning is assigned to an existing code and the new 1164 meaning broadens the meaning of that code, then the meaning 1165 for the associated subtag MAY be changed to match. The 1166 meaning of a subtag MUST NOT be narrowed, however, as this 1167 can result in an unknown proportion of the existing uses of 1168 a subtag becoming invalid. Note: ISO 639 MA/RA has adopted 1169 a similar stability policy. 1171 C. For ISO 15924 codes, if the newly assigned code's meaning is 1172 not represented by a subtag in the IANA registry, the 1173 Language Subtag Reviewer, as described in Section 3.4, SHALL 1174 prepare a proposal for entering in the IANA registry as soon 1175 as practical a registered variant subtag as an alternate 1176 value for the new code. The form of the registered variant 1177 subtag will be at the discretion of the Language Subtag 1178 Reviewer and MUST conform to other restrictions on variant 1179 subtags in this document. 1181 D. For ISO 3166 codes, if the newly assigned code's meaning is 1182 associated with the same UN M.49 code as another 'region' 1183 subtag, then the existing region subtag remains as the 1184 preferred value for that region and no new entry is created. 1185 A comment MAY be added to the existing region subtag 1186 indicating the relationship to the new ISO 3166 code. 1188 E. For ISO 3166 codes, if the newly assigned code's meaning is 1189 associated with a UN M.49 code that is not represented by an 1190 existing region subtag, then the Language Subtag Reviewer, 1191 as described in Section 3.4, SHALL prepare a proposal for 1192 entering the appropriate UN M.49 country code as an entry in 1193 the IANA registry. 1195 F. For ISO 3166 codes, if there is no associated UN numeric 1196 code, then the Language Subtag Reviewer SHALL petition the 1197 UN to create one. If there is no response from the UN 1198 within ninety days of the request being sent, the Language 1199 Subtag Reviewer SHALL prepare a proposal for entering in the 1200 IANA registry as soon as practical a registered variant 1201 subtag as an alternate value for the new code. The form of 1202 the registered variant subtag will be at the discretion of 1203 the Language Subtag Reviewer and MUST conform to other 1204 restrictions on variant subtags in this document. This 1205 situation is very unlikely to ever occur. 1207 11. Codes assigned by UN M.49 to countries or areas (as opposed to 1208 geographical regions and sub-regions) for which there is no 1209 corresponding ISO 3166 code MUST NOT be registered, except under 1210 the previous provisions (as a surrogate for an ISO 3166 code 1211 that cannot itself be registered). If it is necessary to 1212 identify a region for which only a UN M.49 code exists in 1213 language tags, then the registration authority for ISO 3166 1214 SHOULD be petitioned to assign a code, which can then be 1215 registered for use in language tags. At the time this document 1216 was written, there were only four such codes: 830 (Channel 1217 Islands), 831 (Guernsey), 832 (Jersey), and 833 (Isle of Man). 1218 This rule exists so that UN M.49 codes remain available as the 1219 value of last resort in cases where ISO 3166 reassigns a 1220 deprecated value in the registry. 1222 12. Stability provisions apply to grandfathered tags with this 1223 exception: should all of the subtags in a grandfathered tag 1224 become valid subtags in the IANA registry, then the field 'Type' 1225 in that record is changed from 'grandfathered' to 'redundant'. 1226 Note that this will not affect language tags that match the 1227 grandfathered tag, since these tags will now match valid 1228 generative subtag sequences. For example, if the subtag 'gan' 1229 in the language tag "zh-gan" were to be registered as an 1230 extended language subtag, then the grandfathered tag "zh-gan" 1231 would be deprecated (but existing content or implementations 1232 that use "zh-gan" would remain valid). 1234 3.4 Registration Procedure for Subtags 1236 The procedure given here MUST be used by anyone who wants to use a 1237 subtag not currently in the IANA Language Subtag Registry. 1239 Only subtags of type 'language' and 'variant' will be considered for 1240 independent registration of new subtags. Handling of subtags needed 1241 for stability and subtags necessary to keep the registry synchronized 1242 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1243 defined by this document are described in Section 3.2. Stability 1244 provisions are described in Section 3.3. 1246 This procedure MAY also be used to register or alter the information 1247 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1248 in a subtag's record as described in Section 3.3. Changes to all 1249 other fields in the IANA registry are NOT permitted. 1251 Registering a new subtag or requesting modifications to an existing 1252 tag or subtag starts with the requester filling out the registration 1253 form reproduced below. Note that each response is not limited in 1254 size so that the request can adequately describe the registration. 1255 The fields in the "Record Requested" section SHOULD follow the 1256 requirements in Section 3.1. 1258 LANGUAGE SUBTAG REGISTRATION FORM 1259 1. Name of requester: 1260 2. E-mail address of requester: 1261 3. Record Requested: 1263 Type: 1264 Subtag: 1265 Description: 1266 Prefix: 1267 Preferred-Value: 1268 Deprecated: 1269 Suppress-Script: 1270 Comments: 1272 4. Intended meaning of the subtag: 1273 5. Reference to published description 1274 of the language (book or article): 1275 6. Any other relevant information: 1277 Figure 5 1279 The subtag registration form MUST be sent to 1280 for a two week review period before it can 1281 be submitted to IANA. (This is an open list and can be joined by 1282 sending a request to .) 1284 Variant and extlang subtags are always registered for use with a 1285 particular range of language tags. For example, the subtag 'rozaj' 1286 is intended for use with language tags that start with the primary 1287 language subtag "sl", since Resian is a dialect of Slovenian. Thus 1288 the subtag 'rozaj' could be included in tags such as "sl-Latn-rozaj" 1289 or "sl-IT-rozaj". This information is stored in the "Prefix" field 1290 in the registry. Variant registration requests are REQUIRED to 1291 include at least one "Prefix" field in the registration form. 1293 The 'Prefix' field for a given registered subtag will be maintained 1294 in the IANA registry as a guide to usage. Additional prefixes MAY be 1295 added by filing an additional registration form. In that form, the 1296 "Any other relevant information:" field MUST indicate that it is the 1297 addition of a prefix. 1299 Requests to add a prefix to a variant subtag that imply a different 1300 semantic meaning will probably be rejected. For example, a request 1301 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1302 nedis" represented some German dialect would be rejected. The 1303 'nedis' subtag represents a particular Slovenian dialect and the 1304 additional registration would change the semantic meaning assigned to 1305 the subtag. A separate subtag SHOULD be proposed instead. 1307 The 'Description' field MUST contain a description of the tag being 1308 registered written or transcribed into the Latin script; it MAY also 1309 include a description in a non-Latin script. Non-ASCII characters 1310 MUST be escaped using the syntax described in Section 3.1. The 1311 'Description' field is used for identification purposes and doesn't 1312 necessarily represent the actual native name of the language or 1313 variation or to be in any particular language. 1315 While the 'Description' field itself is not guaranteed to be stable 1316 and errata corrections MAY be undertaken from time to time, attempts 1317 to provide translations or transcriptions of entries in the registry 1318 itself will probably be frowned upon by the community or rejected 1319 outright, as changes of this nature have an impact on the provisions 1320 in Section 3.3. 1322 The Language Subtag Reviewer is responsible for responding to 1323 requests for the registration of subtags through the registration 1324 process and is appointed by the IESG. 1326 When the two week period has passed the Language Subtag Reviewer 1327 either forwards the record to be inserted or modified to 1328 iana@iana.org according to the procedure described in Section 3.2, or 1329 rejects the request because of significant objections raised on the 1330 list or due to problems with constraints in this document (which MUST 1331 be explicitly cited). The reviewer MAY also extend the review period 1332 in two week increments to permit further discussion. The reviewer 1333 MUST indicate on the list whether the registration has been accepted, 1334 rejected, or extended following each two week period. 1336 Note that the reviewer can raise objections on the list if he or she 1337 so desires. The important thing is that the objection MUST be made 1338 publicly. 1340 The applicant is free to modify a rejected application with 1341 additional information and submit it again; this restarts the two 1342 week comment period. 1344 Decisions made by the reviewer MAY be appealed to the IESG [RFC2028] 1345 under the same rules as other IETF decisions [RFC2026]. 1347 All approved registration forms are available online in the directory 1348 http://www.iana.org/numbers.html under "languages". 1350 Updates or changes to existing records follow the same procedure as 1351 new registrations. The Language Subtag Reviewer decides whether 1352 there is consensus to update the registration following the two week 1353 review period; normally objections by the original registrant will 1354 carry extra weight in forming such a consensus. 1356 Registrations are permanent and stable. Once registered, subtags 1357 will not be removed from the registry and will remain a valid way in 1358 which to specify a specific language or variant. 1360 Note: The purpose of the "Description" in the registration form is 1361 intended as an aid to people trying to verify whether a language is 1362 registered or what language or language variation a particular subtag 1363 refers to. In most cases, reference to an authoritative grammar or 1364 dictionary of that language will be useful; in cases where no such 1365 work exists, other well known works describing that language or in 1366 that language MAY be appropriate. The subtag reviewer decides what 1367 constitutes "good enough" reference material. This requirement is 1368 not intended to exclude particular languages or dialects due to the 1369 size of the speaker population or lack of a standardized orthography. 1370 Minority languages will be considered equally on their own merits. 1372 3.5 Possibilities for Registration 1374 Possibilities for registration of subtags or information about 1375 subtags include: 1377 o Primary language subtags for languages not listed in ISO 639 that 1378 are not variants of any listed or registered language can be 1379 registered. At the time this document was created there were no 1380 examples of this form of subtag. Before attempting to register a 1381 language subtag, there MUST be an attempt to register the language 1382 with ISO 639. No language subtags will be registered for codes 1383 that exist in ISO 639-1 or ISO 639-2, which are under 1384 consideration by the ISO 639 maintenance or registration 1385 authorities, or which have never been attempted for registration 1386 with those authorities. If ISO 639 has previously rejected a 1387 language for registration, it is reasonable to assume that there 1388 must be additional very compelling evidence of need before it will 1389 be registered in the IANA registry (to the extent that it is very 1390 unlikely that any subtags will be registered of this type). 1392 o Dialect or other divisions or variations within a language, its 1393 orthography, writing system, regional or historical usage, 1394 transliteration or other transformation, or distinguishing 1395 variation MAY be registered as variant subtags. An example is the 1396 'rozaj' subtag (the Resian dialect of Slovenian). 1398 o The addition or maintenance of fields (generally of an 1399 informational nature) in Tag or Subtag records as described in 1400 Section 3.1 and subject to the stability provisions in 1401 Section 3.3. This includes descriptions; comments; deprecation 1402 and preferred values for obsolete or withdrawn codes; or the 1403 addition of script or extlang information to primary language 1404 subtags. 1406 o The addition of records and related field value changes necessary 1407 to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and 1408 UN M.49 as described in Section 3.3. 1410 This document leaves the decision on what subtags or changes to 1411 subtags are appropriate (or not) to the registration process 1412 described in Section 3.4. 1414 Note: four character primary language subtags are reserved to allow 1415 for the possibility of alpha4 codes in some future addition to the 1416 ISO 639 family of standards. 1418 ISO 639 defines a maintenance agency for additions to and changes in 1419 the list of languages in ISO 639. This agency is: 1421 International Information Centre for Terminology (Infoterm) 1422 Aichholzgasse 6/12, AT-1120 1423 Wien, Austria 1424 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1426 ISO 639-2 defines a maintenance agency for additions to and changes 1427 in the list of languages in ISO 639-2. This agency is: 1429 Library of Congress 1430 Network Development and MARC Standards Office 1431 Washington, D.C. 20540 USA 1432 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1433 URL: http://www.loc.gov/standards/iso639 1435 The maintenance agency for ISO 3166 (country codes) is: 1437 ISO 3166 Maintenance Agency 1438 c/o International Organization for Standardization 1439 Case postale 56 1440 CH-1211 Geneva 20 Switzerland 1441 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1442 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1444 The registration authority for ISO 15924 (script codes) is: 1446 Unicode Consortium Box 391476 1447 Mountain View, CA 94039-1476, USA 1448 URL: http://www.unicode.org/iso15924 1450 The Statistics Division of the United Nations Secretariat maintains 1451 the Standard Country or Area Codes for Statistical Use and can be 1452 reached at: 1454 Statistical Services Branch 1455 Statistics Division 1456 United Nations, Room DC2-1620 1457 New York, NY 10017, USA 1459 Fax: +1-212-963-0623 1460 E-mail: statistics@un.org 1461 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1463 3.6 Extensions and Extensions Namespace 1465 Extension subtags are those introduced by single-letter subtags other 1466 than 'x'. They are reserved for the generation of identifiers which 1467 contain a language component, and are compatible with applications 1468 that understand language tags. For example, they might be used to 1469 define locale identifiers, which are generally based on language. 1471 The structure and form of extensions are defined by this document so 1472 that implementations can be created that are forward compatible with 1473 applications that might be created using single-letter subtags in the 1474 future. In addition, defining a mechanism for maintaining single- 1475 letter subtags will lend to the stability of this document by 1476 reducing the likely need for future revisions or updates. 1478 Allocation of a single-letter subtag SHALL take the form of an RFC 1479 defining the name, purpose, processes, and procedures for maintaining 1480 the subtags. The maintaining or registering authority, including 1481 name, contact email, discussion list email, and URL location of the 1482 registry MUST be indicated clearly in the RFC. The RFC MUST specify 1483 or include each of the following: 1485 o The specification MUST reference the specific version or revision 1486 of this document that governs its creation and MUST reference this 1487 section of this document. 1489 o The specification and all subtags defined by the specification 1490 MUST follow the ABNF and other rules for the formation of tags and 1491 subtags as defined in this document. In particular it MUST 1492 specify that case is not significant and that subtags MUST NOT 1493 exceed eight characters in length. 1495 o The specification MUST specify a canonical representation. 1497 o The specification of valid subtags MUST be available over the 1498 Internet and at no cost. 1500 o The specification MUST be in the public domain or available via a 1501 royalty-free license acceptable to the IETF and specified in the 1502 RFC. 1504 o The specification MUST be versioned and each version of the 1505 specification MUST be numbered, dated, and stable. 1507 o The specification MUST be stable. That is, extension subtags, 1508 once defined by a specification, MUST NOT be retracted or change 1509 in meaning in any substantial way. 1511 o The specification MUST include in a separate section the 1512 registration form reproduced in this section (below) to be used in 1513 registering the extension upon publication as an RFC. 1515 o IANA MUST be informed of changes to the contact information and 1516 URL for the specification. 1518 IANA will maintain a registry of allocated single-letter (singleton) 1519 subtags. This registry will use the record-jar format described by 1520 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1521 the maintaining authority defined in the RFC MUST forward this 1522 registration form to iesg@ietf.org, who will forward the request to 1523 iana@iana.org. The maintaining authority of the extension MUST 1524 maintain the accuracy of the record by sending an updated full copy 1525 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1526 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1527 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in 1528 these updates. 1530 Failure to maintain this record, the corresponding registry, or meet 1531 other conditions imposed by this section of this document MAY be 1532 appealed to the IESG [RFC2028] under the same rules as other IETF 1533 decisions (see [RFC2026]) and MAY result in the authority to maintain 1534 the extension being withdrawn or reassigned by the IESG. 1536 %% 1537 Identifier: 1538 Description: 1539 Comments: 1540 Added: 1541 RFC: 1542 Authority: 1543 Contact_Email: 1544 Mailing_List: 1545 URL: 1546 %% 1548 Figure 6: Format of Records in the Language Tag Extensions Registry 1550 'Identifier' contains the single letter subtag (singleton) assigned 1551 to the extension. The Internet-Draft submitted to define the 1552 extension SHOULD specify which letter to use, although the IESG MAY 1553 change the assignment when approving the RFC. 1555 'Description' contains the name and description of the extension. 1557 'Comments' is an OPTIONAL field and MAY contain a broader description 1558 of the extension. 1560 'Added' contains the date the RFC was published in the "full-date" 1561 format specified in [RFC3339]. For example: 2004-06-28 represents 1562 June 28, 2004, in the Gregorian calendar. 1564 'RFC' contains the RFC number assigned to the extension. 1566 'Authority' contains the name of the maintaining authority for the 1567 extension. 1569 'Contact_Email' contains the email address used to contact the 1570 maintaining authority. 1572 'Mailing_List' contains the URL or subscription email address of the 1573 mailing list used by the maintaining authority. 1575 'URL' contains the URL of the registry for this extension. 1577 The determination of whether an Internet-Draft meets the above 1578 conditions and the decision to grant or withhold such authority rests 1579 solely with the IESG, and is subject to the normal review and appeals 1580 process associated with the RFC process. 1582 Extension authors are strongly cautioned that many (including most 1583 well-formed) processors will be unaware of any special relationships 1584 or meaning inherent in the order of extension subtags. Extension 1585 authors SHOULD avoid subtag relationships or canonicalization 1586 mechanisms that interfere with matching or with length restrictions 1587 that sometimes exist in common protocols where the extension is used. 1588 In particular, applications MAY truncate the subtags in doing 1589 matching or in fitting into limited lengths, so it is RECOMMENDED 1590 that the most significant information be in the most significant 1591 (left-most) subtags, and that the specification gracefully handle 1592 truncated subtags. 1594 When a language tag is to be used in a specific, known, protocol, it 1595 is RECOMMENDED that that the language tag not contain extensions not 1596 supported by that protocol. In addition, note that some protocols 1597 MAY impose upper limits on the length of the strings used to store or 1598 transport the language tag. 1600 3.7 Initialization of the Registry 1602 Adoption of this document will REQUIRE an initial version of the 1603 registry containing the various subtags initially valid in a language 1604 tag. This collection of subtags, along with a description of the 1605 process used to create it, is described by [initial-registry]. 1607 Registrations that are in process under the rules defined in 1608 [RFC3066] when this document is adopted MAY be completed under the 1609 former rules, at the discretion of the language tag reviewer. Any 1610 new registrations submitted after the adoption of this document MUST 1611 be rejected. 1613 4. Formation and Processing of Language Tags 1615 This section addresses how to use the information in the registry 1616 with the tag syntax to choose, form and process language tags. 1618 4.1 Choice of Language Tag 1620 One is sometimes faced with the choice between several possible tags 1621 for the same body of text. 1623 Interoperability is best served when all users use the same language 1624 tag in order to represent the same language. If an application has 1625 requirements that make the rules here inapplicable, then that 1626 application risks damaging interoperability. It is strongly 1627 RECOMMENDED that users not define their own rules for language tag 1628 choice. 1630 Subtags SHOULD only be used where they add useful distinguishing 1631 information; extraneous subtags interfere with the meaning, 1632 understanding, and processing of language tags. In particular, users 1633 and implementations SHOULD follow the 'Prefix' and 'Suppress-Script' 1634 fields in the registry (defined in Section 3.1): these fields provide 1635 guidance on when specific additional subtags SHOULD (and SHOULD NOT) 1636 be used in a language tag. 1638 Of particular note, many applications can benefit from the use of 1639 script subtags in language tags, as long as the use is consistent for 1640 a given context. Script subtags were not formally defined in RFC 1641 3066 and their use can affect matching and subtag identification by 1642 implementations of RFC 3066, as these subtags appear between the 1643 primary language and region subtags. For example, if a user requests 1644 content in an implementation of Section 2.5 of [RFC3066] using the 1645 language range "en-US", content labeled "en-Latn-US" will not match 1646 the request. Therefore it is important to know when script subtags 1647 will customarily be used and when they ought not be used. In the 1648 registry, the Suppress-Script field helps ensure greater 1649 compatibility between the language tags generated according to the 1650 rules in this document and language tags and tag processors or 1651 consumers based on RFC 3066 by defining when users SHOULD NOT include 1652 a script subtag with a particular primary language subtag. 1654 Extended language subtags (type 'extlang' in the registry, see 1655 Section 3.1) also appear between the primary language and region 1656 subtags and are reserved for future standardization. Applications 1657 might benefit from their judicious use in forming language tags in 1658 the future. Similar recommendations are expected to apply to their 1659 use as apply to script subtags. 1661 Standards, protocols and applications that reference this document 1662 normatively but apply different rules to the ones given in this 1663 section MUST specify how the procedure varies from the one given 1664 here. 1666 The choice of subtags used to form a language tag SHOULD be guided by 1667 the following rules: 1669 1. Use as precise a tag as possible, but no more specific than is 1670 justified. Avoid using subtags that are not important for 1671 distinguishing content in an application. 1673 * For example, 'de' might suffice for tagging an email written 1674 in German, while "de-CH-1996" is probably unnecessarily 1675 precise for such a task. 1677 2. The script subtag SHOULD NOT be used to form language tags unless 1678 the script adds some distinguishing information to the tag. The 1679 field 'Suppress-Script' in the primary language record in the 1680 registry indicates which script subtags do not add distinguishing 1681 information for most applications. 1683 * For example, the subtag 'Latn' should not be used with the 1684 primary language 'en' because nearly all English documents are 1685 written in the Latin script and it adds no distinguishing 1686 information. However, if a document were written in English 1687 mixing Latin script with another script such as Braille 1688 ('Brai'), then it might be appropriate to choose to indicate 1689 both scripts to aid in content selection, such as the 1690 application of a stylesheet. 1692 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1693 entry, then the value of that field SHOULD be used to form the 1694 language tag in preference to the tag or subtag in which the 1695 preferred value appears. 1697 * For example, use 'he' for Hebrew in preference to 'iw'. 1699 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1700 used to label content, even if the language is unknown. Omitting 1701 the language tag altogether is preferred to using a tag with a 1702 primary language subtag of 'und'. The 'und' subtag MAY be useful 1703 for protocols that require a language tag to be provided. The 1704 'und' subtag MAY also be useful when matching language tags in 1705 certain situations. 1707 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1708 whenever the protocol allows the separate tags for multiple 1709 languages, as is the case for the Content-Language header in 1710 HTTP. The 'mul' subtag conveys little useful information: 1711 content in multiple languages SHOULD individually tag the 1712 languages where they appear or otherwise indicate the actual 1713 language in preference to the 'mul' subtag. 1715 6. The same variant subtag SHOULD NOT be used more than once within 1716 a language tag. 1718 * For example, do not use "de-DE-1901-1901". 1720 To ensure consistent backward compatibility, this document contains 1721 several provisions to account for potential instability in the 1722 standards used to define the subtags that make up language tags. 1723 These provisions mean that no language tag created under the rules in 1724 this document will become obsolete. 1726 4.2 Meaning of the Language Tag 1728 The relationship between the tag and the information it relates to is 1729 defined by the the context in which the tag appears. Accordingly, 1730 this section can only give possible examples of its usage. 1732 o For a single information object, the associated language tags 1733 might be interpreted as the set of languages that is necessary for 1734 a complete comprehension of the complete object. Example: Plain 1735 text documents. 1737 o For an aggregation of information objects, the associated language 1738 tags could be taken as the set of languages used inside components 1739 of that aggregation. Examples: Document stores and libraries. 1741 o For information objects whose purpose is to provide alternatives, 1742 the associated language tags could be regarded as a hint that the 1743 content is provided in several languages, and that one has to 1744 inspect each of the alternatives in order to find its language or 1745 languages. In this case, the presence of multiple tags might not 1746 mean that one needs to be multi-lingual to get complete 1747 understanding of the document. Example: MIME multipart/ 1748 alternative. 1750 o In markup languages, such as HTML and XML, language information 1751 can be added to each part of the document identified by the markup 1752 structure (including the whole document itself). For example, one 1753 could write C'est la vie. inside a 1754 Norwegian document; the Norwegian-speaking user could then access 1755 a French-Norwegian dictionary to find out what the marked section 1756 meant. If the user were listening to that document through a 1757 speech synthesis interface, this formation could be used to signal 1758 the synthesizer to appropriately apply French text-to-speech 1759 pronunciation rules to that span of text, instead of applying the 1760 inappropriate Norwegian rules. 1762 Language tags are related when they contain a similar sequence of 1763 subtags. For example, if a language tag B contains language tag A as 1764 a prefix, then B is typically "narrower" or "more specific" than A. 1765 Thus "zh-Hant-TW" is more specific than "zh-Hant". 1767 This relationship is not guaranteed in all cases: specifically, 1768 languages that begin with the same sequence of subtags are NOT 1769 guaranteed to be mutually intelligible, although they might be. For 1770 example, the tag "az" shares a prefix with both "az-Latn" 1771 (Azerbaijani written using the Latin script) and "az-Cyrl" 1772 (Azerbaijani written using the Cyrillic script). A person fluent in 1773 one script might not be able to read the other, even though the text 1774 might be identical. Content tagged as "az" most probably is written 1775 in just one script and thus might not be intelligible to a reader 1776 familiar with the other script. 1778 4.3 Length Considerations 1780 [RFC3066] did not provide an upper limit on the size of language 1781 tags. While RFC 3066 did define the semantics of particular subtags 1782 in such a way that most language tags consisted of language and 1783 region subtags with a combined total length of up to six characters, 1784 larger registered tags were not only possible but were actually 1785 registered. 1787 Neither the language tag syntax nor other requirements in this 1788 document impose a fixed upper limit on the number of subtags in a 1789 language tag (and thus an upper bound on the size of a tag). The 1790 language tag syntax suggests that, depending on the specific 1791 language, more subtags (and thus a longer tag) are sometimes 1792 necessary to completely identify the language for certain 1793 applications; thus it is possible to envision long or complex subtag 1794 sequences. 1796 4.3.1 Working with Limited Buffer Sizes 1798 Some applications and protocols are forced to allocate fixed buffer 1799 sizes or otherwise limit the length of a language tag. A conformant 1800 implementation or specification MAY refuse to support the storage of 1801 language tags which exceed a specified length. Any such limitation 1802 SHOULD be clearly documented, and such documentation SHOULD include 1803 what happens to longer tags (for example, whether an error value is 1804 generated or the language tag is truncated). A protocol that allows 1805 tags to be truncated at an arbitrary limit, without giving any 1806 indication of what that limit is, has the potential for causing harm 1807 by changing the meaning of tags in substantial ways. 1809 In practice, most language tags do not require more than a few 1810 subtags and will not approach reasonably sized buffer limitations: 1811 see Section 4.1. 1813 Some specifications or protocols have limits on tag length but do not 1814 have a fixed length limitation. For example, [RFC2231] has no 1815 explicit length limitation: the length available for the language tag 1816 is constrained by the length of other header components (such as the 1817 charset's name) coupled with the 76 character limit in [RFC2047]. 1818 Thus the "limit" might be 50 or more characters, but it could 1819 potentially be quite small. 1821 The considerations for assigning a buffer limit are: 1823 Implementations SHOULD NOT truncate language tags unless the 1824 meaning of the tag is purposefully being changed, or unless the 1825 tag does not fit into a limited buffer size specified by a 1826 protocol for storage or transmission. 1828 Implementations SHOULD warn the user when a tag is truncated since 1829 truncation changes the semantic meaning of the tag. 1831 Implementations of protocols or specifications that are space 1832 constrained but do not have a fixed limit SHOULD use the longest 1833 possible tag in preference to truncation. 1835 Protocols or specifications that specify limited buffer sizes for 1836 language tags MUST allow for language tags of up to 33 characters. 1838 Protocols or specifications that specify limited buffer sizes for 1839 language tags SHOULD allow for language tags of at least 42 1840 characters. 1842 The following illustration shows how the 42-character recommendation 1843 was derived. The combination of language and extended language 1844 subtags was chosen for future compatibility. At up to 15 characters, 1845 this combination is longer than the longest possible primary language 1846 subtag (8 characters): 1848 language = 3 (ISO 639-2; ISO 639-1 requires 2) 1849 extlang1 = 4 (each subsequent subtag includes '-') 1850 extlang2 = 4 (unlikely: needs prefix="language-extlang1") 1851 extlang3 = 4 (extremely unlikely) 1852 script = 5 (if not suppressed: see Section 4.1) 1853 region = 4 (UN M.49; ISO 3166 requires 3) 1854 variant1 = 9 (MUST have language as a prefix) 1855 variant2 = 9 (MUST have language-variant1 as a prefix) 1857 total = 42 characters 1859 Figure 7: Derivation of the Limit on Tag Length 1861 4.3.2 Truncation of Language Tags 1863 Truncation of a language tag alters the meaning of the tag, and thus 1864 SHOULD be avoided. However, truncation of language tags is sometimes 1865 necessary due to limited buffer sizes. Such truncation MUST NOT 1866 permit a subtag to be chopped off in the middle or the formation of 1867 invalid tags (for example, one ending with the "-" character). 1869 This means that applications or protocols which truncate tags MUST do 1870 so by progressively removing subtags along with their preceding "-" 1871 from the right side of the language tag until the tag is short enough 1872 for the given buffer. If the resulting tag ends with a single- 1873 character subtag, that subtag and its preceding "-" MUST also be 1874 removed. For example: 1876 Tag to truncate: zh-Hant-CN-variant1-a-extend1-x-wadegile-private1 1877 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 1878 2. zh-Latn-CN-variant1-a-extend1 1879 3. zh-Latn-CN-variant1 1880 4. zh-Latn-CN 1881 5. zh-Latn 1882 6. zh 1884 Figure 8: Example of Tag Truncation 1886 4.4 Canonicalization of Language Tags 1888 Since a particular language tag is sometimes used by many processes, 1889 language tags SHOULD always be created or generated in a canonical 1890 form. 1892 A language tag is in canonical form when: 1894 1. The tag is well-formed according the rules in Section 2.1 and 1895 Section 2.2. 1897 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1898 the IANA registry (see Section 3.1) SHOULD be replaced with their 1899 mapped value. 1901 3. Redundant or grandfathered tags that have a Preferred-Value 1902 mapping in the IANA registry (see Section 3.1) MUST be replaced 1903 with their mapped value. These items are either deprecated 1904 mappings created before the adoption of this document (such as 1905 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1906 the result of later registrations or additions to this document 1907 (for example, "zh-guoyu" might be mapped to a language-extlang 1908 combination such as "zh-cmn" by some future update of this 1909 document). 1911 4. Other subtags that have a Preferred-Value mapping in the IANA 1912 registry (see Section 3.1) MUST be replaced with their mapped 1913 value. These items consist entirely of clerical corrections to 1914 ISO 639-1 in which the deprecated subtags have been maintained 1915 for compatibility purposes. 1917 5. If more than one extension subtag sequence exists, the extension 1918 sequences are ordered into case-insensitive ASCII order by 1919 singleton subtag. 1921 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1922 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1923 canonical form. 1925 Example: The language tag "en-NH" (English as used in the New 1926 Hebrides) is not canonical because the 'NH' subtag has a canonical 1927 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1928 validity. 1930 Canonicalization of language tags does not imply anything about the 1931 use of upper or lowercase letters when processing or comparing 1932 subtags (and as described in Section 2.1). All comparisons MUST be 1933 performed in a case-insensitive manner. 1935 When performing canonicalization of language tags, processors MAY 1936 regularize the case of the subtags (that is, this process is 1937 OPTIONAL), following the case used in the registry. Note that this 1938 corresponds to the following casing rules: uppercase all non-initial 1939 two-letter subtags; titlecase all non-initial four-letter subtags; 1940 lowercase everything else. 1942 Note: Case folding of ASCII letters in certain locales, unless 1943 carefully handled, sometimes produces non-ASCII character values. 1944 The Unicode Character Database file "SpecialCasing.txt" defines the 1945 specific cases that are known to cause problems with this. In 1946 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1947 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1948 Implementers SHOULD specify a locale-neutral casing operation to 1949 ensure that case folding of subtags does not produce this value, 1950 which is illegal in language tags. For example, if one were to 1951 uppercase the region subtag 'in' using Turkish locale rules, the 1952 sequence U+0130 U+004E would result instead of the expected 'IN'. 1954 Note: if the field 'Deprecated' appears in a registry record without 1955 an accompanying 'Preferred-Value' field, then that tag or subtag is 1956 deprecated without a replacement. Validating processors SHOULD NOT 1957 generate tags that include these values, although the values are 1958 canonical when they appear in a language tag. 1960 An extension MUST define any relationships that exist between the 1961 various subtags in the extension and thus MAY define an alternate 1962 canonicalization scheme for the extension's subtags. Extensions MAY 1963 define how the order of the extension's subtags are interpreted. For 1964 example, an extension could define that its subtags are in canonical 1965 order when the subtags are placed into ASCII order: that is, "en-a- 1966 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1967 define that the order of the subtags influences their semantic 1968 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1969 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1970 so that they are tolerant of the typical processes described in 1971 Section 3.6. 1973 4.5 Considerations for Private Use Subtags 1975 Private-use subtags require private agreement between the parties 1976 that intend to use or exchange language tags that use them and great 1977 caution SHOULD be used in employing them in content or protocols 1978 intended for general use. Private-use subtags are simply useless for 1979 information exchange without prior arrangement. 1981 The value and semantic meaning of private-use tags and of the subtags 1982 used within such a language tag are not defined by this document. 1984 The use of subtags defined in the IANA registry as having a specific 1985 private use meaning convey more information that a purely private use 1986 tag prefixed by the singleton subtag 'x'. For applications this 1987 additional information MAY be useful. 1989 For example, the region subtags 'AA', 'ZZ' and in the ranges 1990 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 1991 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 1992 great deal of public, interchangeable information about the language 1993 material (that it is Chinese in the simplified Chinese script and is 1994 suitable for some geographic region 'XQ'). While the precise 1995 geographic region is not known outside of private agreement, the tag 1996 conveys far more information than an opaque tag such as "x-someLang", 1997 which contains no information about the language subtag or script 1998 subtag outside of the private agreement. 2000 However, in some cases content tagged with private use subtags MAY 2001 interact with other systems in a different and possibly unsuitable 2002 manner compared to tags that use opaque, privately defined subtags, 2003 so the choice of the best approach sometimes depends on the 2004 particular domain in question. 2006 5. IANA Considerations 2008 This section deals with the processes and requirements necessary for 2009 IANA to undertake to maintain the subtag and extension registries as 2010 defined by this document and in accordance with the requirements of 2011 [RFC2434]. 2013 The impact on the IANA maintainers of the two registries defined by 2014 this document will be a small increase in the frequency of new 2015 entries or updates. 2017 5.1 Language Subtag Registry 2019 Upon adoption of this document, the registry will be initialized by a 2020 companion document: [initial-registry]. The criteria and process for 2021 selecting the initial set of records is described in that document. 2022 The initial set of records represents no impact on IANA, since the 2023 work to create it will be performed externally. 2025 The new registry MUST be listed under "Language Tags" at 2026 , replacing the existing 2027 registrations defined by [RFC3066]. The existing set of registration 2028 forms and RFC 3066 registrations will be relabeled as "Language Tags 2029 (Obsolete)" and maintained (but not added to or modified). 2031 Future work on the Language Subtag Registry will be limited to 2032 inserting or replacing whole records preformatted for IANA by the 2033 Language Subtag Reviewer as described in Section 3.2 of this 2034 document. This simplifies IANA's work by limiting it to placing the 2035 text in the appropriate location in the registry. 2037 Each record will be sent to iana@iana.org with a subject line 2038 indicating whether the enclosed record is an insertion of a new 2039 record (indicated by the word "INSERT" in the subject line) or a 2040 replacement of an existing record (indicated by the word "MODIFY" in 2041 the subject line). Records MUST NOT be deleted from the registry. 2042 IANA MUST place any inserted or modified records into the appropriate 2043 section of the language subtag registry, grouping the records by 2044 their "Type" field. Inserted records MAY be placed anywhere in the 2045 appropriate section; there is no guarantee of the order of the 2046 records beyond grouping them together by 'Type'. Modified records 2047 MUST overwrite the record they replace. 2049 Included in any request to insert or modify records MUST be a new 2050 File-Date record. This record MUST be placed first in the registry. 2051 In the event that the File-Date record present in the registry has a 2052 later date then the record being inserted or modified, the existing 2053 record MUST be preserved. 2055 5.2 Extensions Registry 2057 The Language Tag Extensions registry will also be generated and sent 2058 to IANA as described in Section 3.6. This registry can contain at 2059 most 35 records and thus changes to this registry are expected to be 2060 very infrequent. 2062 Future work by IANA on the Language Tag Extensions Registry is 2063 limited to two cases. First, the IESG MAY request that new records 2064 be inserted into this registry from time to time. These requests 2065 will include the record to insert in the exact format described in 2066 Section 3.6. In addition, there MAY be occasional requests from the 2067 maintaining authority for a specific extension to update the contact 2068 information or URLs in the record. These requests MUST include the 2069 complete, updated record. IANA is not responsible for validating the 2070 information provided, only that it is properly formatted. It should 2071 reasonably be seen to come from the maintaining authority named in 2072 the record present in the registry. 2074 6. Security Considerations 2076 Language tags used in content negotiation, like any other information 2077 exchanged on the Internet, might be a source of concern because they 2078 might be used to infer the nationality of the sender, and thus 2079 identify potential targets for surveillance. 2081 This is a special case of the general problem that anything sent is 2082 visible to the receiving party and possibly to third parties as well. 2083 It is useful to be aware that such concerns can exist in some cases. 2085 The evaluation of the exact magnitude of the threat, and any possible 2086 countermeasures, is left to each application protocol (see BCP 72 2087 [RFC3552] for best current practice guidance on security threats and 2088 defenses). 2090 The language tag associated with a particular information item is of 2091 no consequence whatsoever in determining whether that content might 2092 contain possible homographs. The fact that a text is tagged as being 2093 in one language or using a particular script subtag provides no 2094 assurance whatsoever that it does not contain characters from scripts 2095 other than the one(s) associated with or specified by that language 2096 tag. 2098 Since there is no limit to the number of variant, private use, and 2099 extension subtags, and consequently no limit on the possible length 2100 of a tag, implementations need to guard against buffer overflow 2101 attacks. See Section 4.3 for details on language tag truncation, 2102 which can occur as a consequence of defenses against buffer overflow. 2104 Although the specification of valid subtags for an extension (see: 2105 Section 3.6) MUST be available over the Internet, implementations 2106 SHOULD NOT mechanically depend on it being always accessible, to 2107 prevent denial-of-service attacks. 2109 7. Character Set Considerations 2111 The syntax in this document requires that language tags use only the 2112 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2113 character sets, so the composition of language tags should not have 2114 any character set issues. 2116 Rendering of characters based on the content of a language tag is not 2117 addressed in this memo. Historically, some languages have relied on 2118 the use of specific character sets or other information in order to 2119 infer how a specific character should be rendered (notably this 2120 applies to language and culture specific variations of Han ideographs 2121 as used in Japanese, Chinese, and Korean). When language tags are 2122 applied to spans of text, rendering engines can use that information 2123 in deciding which font to use in the absence of other information, 2124 particularly where languages with distinct writing traditions use the 2125 same characters. 2127 8. Changes from RFC 3066 2129 The main goals for this revision of language tags were the following: 2131 *Compatibility.* All RFC 3066 language tags (including those in the 2132 IANA registry) remain valid in this specification. The changes in 2133 this document represent additional constraints on language tags. 2134 That is, in no case is the syntax more permissive and processors 2135 based on the RFC 3066 ABNF (such as those described in [XMLSchema]) 2136 will be able to process the tags described by this document. In 2137 addition, this document defines language tags in such as way as to 2138 ensure future compatibility. 2140 *Stability.* Because of changes in the past in the underlying ISO 2141 standards, a valid RFC 3066 language tag could become invalid or have 2142 its meaning change. This has the potential of invalidating content 2143 that may have an extensive shelf-life. In this specification, once a 2144 language tag is valid, it remains valid forever. 2146 *Validity.* The structure of language tags defined by this document 2147 makes it possible to determine if a particular tag is well-formed 2148 without regard for the actual content or "meaning" of the tag as a 2149 whole. This is important because the registry grows and underlying 2150 standards change over time. In addition, it must be possible to 2151 determine if a tag is valid (or not) for a given point in time in 2152 order to provide reproducible, testable results. This process must 2153 not be error-prone; otherwise implementations might give different 2154 results. By having an authoritative registry with specific 2155 versioning information, the validity of language tags at any point in 2156 time can be precisely determined (instead of interpolating values 2157 from many separate sources). 2159 *Utility.* It is sometimes important to be able to differentiate 2160 between written forms of a language -- for many implementations this 2161 is more important than distinguishing between the spoken variants of 2162 a language. Languages are written in a wide variety of different 2163 scripts, so this document provides for the generative use of ISO 2164 15924 script codes. Like the generative use of ISO language and 2165 country codes in RFC 3066, this allows combinations to be produced 2166 without resorting to the registration process. The addition of UN 2167 M.49 codes provides for the generation of language tags with regional 2168 scope, which is also required by some applications. 2170 The recast of the registry from containing whole language tags to 2171 subtags is a key part of this. An important feature of RFC 3066 was 2172 that it allowed generative use of subtags. This allows people to 2173 meaningfully use generated tags, without the delays in registering 2174 whole tags or the need to register all of the combinations that might 2175 be useful. 2177 The choice of placing the extended language and script subtags 2178 between the primary language and region subtags was widely debated. 2179 This design was chosen because the prevalent matching and content 2180 negotiation schemes rely on the subtags being arranged in order of 2181 increasing specificity. That is, the subtags that mark a greater 2182 barrier to mutual intelligibility appear left-most in a tag. For 2183 example, when selecting content written in Azerbaijani, the script 2184 (Arabic, Cyrillic, or Latin) represents a greater barrier to 2185 understanding than any regional variations (those associated with 2186 Azerbaijan or Iran, for example). Individuals who prefer documents 2187 in a particular script, but can deal with the minor regional 2188 differences, can therefore select appropriate content. Applications 2189 that do not deal with written content will continue to omit these 2190 subtags. 2192 *Extensibility.* Because of the widespread use of language tags, it 2193 is disruptive to have periodic revisions of the core specification, 2194 even in the face of demonstrated need. The extension mechanism 2195 provides for a way for independent RFCs to define extensions to 2196 language tags. These extensions have a very constrained, well- 2197 defined structure that prevent extensions from interfering with 2198 implementations of language tags defined in this document. 2200 The document also anticipates features of ISO 639-3 with the addition 2201 of the extended language subtags, as well as the possibility of other 2202 ISO 639 parts becoming useful for the formation of language tags in 2203 the future. 2205 The use and definition of private use tags has also been modified, to 2206 allow people to use private use subtags to extend or modify defined 2207 tags and to move as much information as possible out of private use 2208 and into the regular structure. 2210 The goal for each of these modifications is to reduce or eliminate 2211 the need for future revisions of this document. 2213 The specific changes in this document to meet these goals are: 2215 o Defines the ABNF and rules for subtags so that the category of all 2216 subtags can be determined without reference to the registry. 2218 o Adds the concept of well-formed vs. validating processors, 2219 defining the rules by which an implementation can claim to be one 2220 or the other. 2222 o Replaces the IANA language tag registry with a language subtag 2223 registry that provides a complete list of valid subtags in the 2224 IANA registry. This allows for robust implementation and ease of 2225 maintenance. The language subtag registry becomes the canonical 2226 source for forming language tags. 2228 o Provides a process that guarantees stability of language tags, by 2229 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2230 the event that they register a previously used value for a new 2231 purpose. 2233 o Allows ISO 15924 script code subtags and allows them to be used 2234 generatively. Defines a method for indicating in the registry 2235 when script subtags are necessary for a given language tag. 2237 o Adds the concept of a variant subtag and allows variants to be 2238 used generatively. 2240 o Adds the ability to use a class of UN M.49 tags for supra- 2241 national regions and to resolve conflicts in the assignment of ISO 2242 3166 codes. 2244 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2245 as the mechanism for creating private-use language, script, and 2246 region subtags respectively. 2248 o Adds a well-defined extension mechanism. 2250 o Defines an extended language subtag, possibly for use with certain 2251 anticipated features of ISO 639-3. 2253 Ed Note: The following items are provided for the convenience of 2254 reviewers and will be removed from the final document. 2256 Changes between draft-ietf-ltru-registry-07 and this version are: 2258 o Removed the reference to RFC 3066 and RFC 1766 from the abstract. 2259 (F.Ellermann) 2261 o Minor tweaking of the text in Section 2.1. (A.Phillips) 2263 9. References 2265 9.1 Normative References 2267 [ISO639-1] 2268 International Organization for Standardization, "ISO 639- 2269 1:2002, Codes for the representation of names of languages 2270 -- Part 1: Alpha-2 code", ISO Standard 639, 2002, . 2273 [ISO639-2] 2274 International Organization for Standardization, "ISO 639- 2275 2:1998 - Codes for the representation of names of 2276 languages -- Part 2: Alpha-3 code - edition 1", 2277 August 1988, . 2279 [ISO15924] 2280 ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2281 representation of names of scripts", January 2004, . 2284 [ISO3166] International Organization for Standardization, "Codes for 2285 the representation of names of countries, 3rd edition", 2286 ISO Standard 3166, August 1988, . 2288 [UN_M.49] Statistical Division, United Nations, "Standard Country or 2289 Area Codes for Statistical Use", UN Standard Country or 2290 Area Codes for Statistical Use, Revision 4 (United Nations 2291 publication, Sales No. 98.XVII.9, June 1999, . 2293 [ISO10646] 2294 International Organization for Standardization, "ISO/IEC 2295 10646-1:2000. Information technology -- Universal 2296 Multiple-Octet Coded Character Set (UCS) -- Part 1: 2297 Architecture and Basic Multilingual Plane and ISO/IEC 2298 10646-2:2001. Information technology -- Universal 2299 Multiple-Octet Coded Character Set (UCS) -- Part 2: 2300 Supplementary Planes, as, from time to time, amended, 2301 replaced by a new edition or expanded by the addition of 2302 new parts", 2000, . 2304 [RFC2234bis] 2305 Crocker, D. and P. Overell, "Augmented BNF for Syntax 2306 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 2307 (work in progress), March 2005. 2309 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 2310 3", BCP 9, RFC 2026, October 1996. 2312 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 2313 the IETF Standards Process", BCP 11, RFC 2028, 2314 October 1996. 2316 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 2317 Part Three: Message Header Extensions for Non-ASCII Text", 2318 RFC 2047, November 1996. 2320 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2321 Requirement Levels", BCP 14, RFC 2119, March 1997. 2323 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2324 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 2325 October 1998. 2327 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 2328 10646", RFC 2781, February 2000. 2330 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2331 Understanding Concerning the Technical Work of the 2332 Internet Assigned Numbers Authority", RFC 2860, June 2000. 2334 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2335 Timestamps", RFC 3339, July 2002. 2337 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2338 Text on Security Considerations", BCP 72, RFC 3552, 2339 July 2003. 2341 9.2 Informative References 2343 [initial-registry] 2344 Ewell, D., Ed., "Initial Language Subtag Registry", 2345 June 2005, . 2348 [iso639.principles] 2349 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2350 Committee: Working principles for ISO 639 maintenance", 2351 March 2000, 2352 . 2355 [record-jar] 2356 Raymond, E., "The Art of Unix Programming", 2003. 2358 [XML10] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2359 02 2004. 2361 [XMLSchema] 2362 Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2363 Datatypes Second Edition", 10 2004, < 2364 http://www.w3.org/TR/xmlschema-2/>. 2366 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 2367 Standard, Version 4.1.0, defined by: The Unicode Standard, 2368 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2369 18578-1), as amended by Unicode 4.0.1 2370 (http://www.unicode.org/versions/Unicode4.0.1) and by 2371 Unicode 4.1.0 2372 (http://www.unicode.org/versions/Unicode4.1.0).", 2373 March 2005. 2375 [RFC1766] Alvestrand, H., "Tags for the Identification of 2376 Languages", RFC 1766, March 1995. 2378 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 2379 Word Extensions: Character Sets, Languages, and 2380 Continuations", RFC 2231, November 1997. 2382 [RFC3066] Alvestrand, H., "Tags for the Identification of 2383 Languages", BCP 47, RFC 3066, January 2001. 2385 Authors' Addresses 2387 Addison Phillips (editor) 2388 Quest Software 2390 Email: addison.phillips@quest.com 2392 Mark Davis (editor) 2393 IBM 2395 Email: mark.davis@us.ibm.com 2397 Appendix A. Acknowledgements 2399 Any list of contributors is bound to be incomplete; please regard the 2400 following as only a selection from the group of people who have 2401 contributed to make this document what it is today. 2403 The contributors to RFC 3066 and RFC 1766, the precursors of this 2404 document, made enormous contributions directly or indirectly to this 2405 document and are generally responsible for the success of language 2406 tags. 2408 The following people (in alphabetical order) contributed to this 2409 document or to RFCs 1766 and 3066: 2411 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2412 Nathaniel Borenstein, Karen Broome, Eric Brunner, Sean M. Burke, M.T. 2413 Carrasco Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter 2414 Constable, John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, 2415 Frank Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, 2416 Dirk-Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty 2417 Harold, Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle 2418 Jarnefors, Kent Karlsson, John Klensin, Alain LaBonte, Eric Mader, 2419 Ira McDonald, Keith Moore, Chris Newman, Masataka Ohta, Randy 2420 Presuhn, George Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry 2421 Sourbier, Otto Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha 2422 Wolf, Francois Yergeau and many, many others. 2424 Very special thanks must go to Harald Tveit Alvestrand, who 2425 originated RFCs 1766 and 3066, and without whom this document would 2426 not have been possible. Special thanks must go to Michael Everson, 2427 who has served as language tag reviewer for almost the complete 2428 period since the publication of RFC 1766. Special thanks to Doug 2429 Ewell, for his production of the first complete subtag registry, and 2430 his work in producing a test parser for verifying language tags. 2432 Appendix B. Examples of Language Tags (Informative) 2434 Simple language subtag: 2436 de (German) 2438 fr (French) 2440 ja (Japanese) 2442 i-enochian (example of a grandfathered tag) 2444 Language subtag plus Script subtag: 2446 zh-Hant (Chinese written using the Traditional Chinese script) 2448 zh-Hans (Chinese written using the Simplified Chinese script) 2450 sr-Cyrl (Serbian written using the Cyrillic script) 2452 sr-Latn (Serbian written using the Latin script) 2454 Language-Script-Region: 2456 zh-Hans-CN (Chinese written using the Simplified script as used in 2457 mainland China) 2459 sr-Latn-CS (Serbian written using the Latin script as used in 2460 Serbia and Montenegro) 2462 Language-Variant: 2464 sl-rozaj (Resian dialect of Slovenian 2466 sl-nedis (Nadiza dialect of Slovenian) 2468 Language-Region-Variant: 2470 de-CH-1901 (German as used in Switzerland using the 1901 variant 2471 [othography]) 2473 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 2475 Language-Script-Region-Variant: 2477 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2478 Latin script as used in Italy. Note that this tag is NOT 2479 RECOMMENDED because subtag 'sl' has a Suppress-Script value of 2480 'Latn') 2482 Language-Region: 2484 de-DE (German for Germany) 2486 en-US (English as used in the United States) 2488 es-419 (Spanish appropriate for the Latin America and Caribbean 2489 region using the UN region code) 2491 Private-use subtags: 2493 de-CH-x-phonebk 2495 az-Arab-x-AZE-derbend 2497 Extended language subtags (examples ONLY: extended languages MUST be 2498 defined by revision or update to this document): 2500 zh-min 2502 zh-min-nan-Hant-CN 2504 Private-use registry values: 2506 x-whatever (private use using the singleton 'x') 2508 qaa-Qaaa-QM-x-southern (all private tags) 2510 de-Qaaa (German, with a private script) 2512 sr-Latn-QM (Serbian, Latin-script, private region) 2514 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2516 Tags that use extensions (examples ONLY: extensions MUST be defined 2517 by revision or update to this document or by RFC): 2519 en-US-u-islamCal 2521 zh-CN-a-myExt-x-private 2522 en-a-myExt-b-another 2524 Some Invalid Tags: 2526 de-419-DE (two region tags) 2528 a-DE (use of a single character subtag in primary position; note 2529 that there are a few grandfathered tags that start with "i-" that 2530 are valid) 2532 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2533 prefix) 2535 Intellectual Property Statement 2537 The IETF takes no position regarding the validity or scope of any 2538 Intellectual Property Rights or other rights that might be claimed to 2539 pertain to the implementation or use of the technology described in 2540 this document or the extent to which any license under such rights 2541 might or might not be available; nor does it represent that it has 2542 made any independent effort to identify any such rights. Information 2543 on the procedures with respect to rights in RFC documents can be 2544 found in BCP 78 and BCP 79. 2546 Copies of IPR disclosures made to the IETF Secretariat and any 2547 assurances of licenses to be made available, or the result of an 2548 attempt made to obtain a general license or permission for the use of 2549 such proprietary rights by implementers or users of this 2550 specification can be obtained from the IETF on-line IPR repository at 2551 http://www.ietf.org/ipr. 2553 The IETF invites any interested party to bring to its attention any 2554 copyrights, patents or patent applications, or other proprietary 2555 rights that may cover technology that may be required to implement 2556 this standard. Please address the information to the IETF at 2557 ietf-ipr@ietf.org. 2559 Disclaimer of Validity 2561 This document and the information contained herein are provided on an 2562 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2563 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2564 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2565 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2566 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2567 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2569 Copyright Statement 2571 Copyright (C) The Internet Society (2005). This document is subject 2572 to the rights, licenses and restrictions contained in BCP 78, and 2573 except as set forth therein, the authors retain all their rights. 2575 Acknowledgment 2577 Funding for the RFC Editor function is currently provided by the 2578 Internet Society.