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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 2399, 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: January 12, 2006 M. Davis, Ed. 5 IBM 6 July 11, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-09 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 January 12, 2006. 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 . . . . . . . . . 16 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 . . . . . . . . . . . . . . . . . . . . . . . . . . 54 86 9.1 Normative References . . . . . . . . . . . . . . . . . . . 54 87 9.2 Informative References . . . . . . . . . . . . . . . . . . 55 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 56 89 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 57 90 B. Examples of Language Tags (Informative) . . . . . . . . . . . 58 91 Intellectual Property and Copyright Statements . . . . . . . . 61 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 beings 140 for communication of information to other human beings. Computer 141 languages such as programming languages are explicitly excluded. 143 2.1 Syntax 145 The language tag is composed of one or more parts or "subtags". Each 146 subtag consists of a sequence of alpha-numeric characters. Subtags 147 are distinguished and separated from one another by a hyphen ("-", 148 ABNF %x2D). A language tag consists of a "primary language" subtag 149 and a (possibly empty) series of subsequent subtags, each of which 150 refines or narrows the range of language identified by the overall 151 tag. 153 Each type of subtag is distinguished by length, position in the tag, 154 and content: subtags can be recognized solely by these features. 155 This makes it possible to construct a parser that can extract and 156 assign some semantic information to the subtags, even if the specific 157 subtag values are not recognized. Thus a parser need not have an up- 158 to-date copy (or any copy at all) of the subtag registry to perform 159 most searching and matching operations. 161 The syntax of the language tag in ABNF [RFC2234bis] is: 163 Language-Tag = (lang 164 *3("-" extlang) 165 ["-" script] 166 ["-" region] 167 *("-" variant) 168 *("-" extension) 169 ["-" privateuse]) 170 / privateuse ; private use tag 171 / grandfathered ; grandfathered registrations 173 lang = 2*4ALPHA ; shortest ISO 639 code 174 / registered-lang 175 extlang = 3ALPHA ; reserved for future use 176 script = 4ALPHA ; ISO 15924 code 177 region = 2ALPHA ; ISO 3166 code 178 / 3DIGIT ; UN country number 179 variant = 5*8alphanum ; registered variants 180 / ( DIGIT 3alphanum ) 181 extension = singleton 1*("-" (2*8alphanum)) 182 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 183 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 184 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 185 ; Single letters: x/X is reserved for private use 186 registered-lang = 4*8ALPHA ; registered language subtag 187 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 188 ; grandfathered registration 189 ; Note: i is the only singleton 190 ; that starts a grandfathered tag 191 alphanum = (ALPHA / DIGIT) ; letters and numbers 193 Figure 1: Language Tag ABNF 195 Note: There is a subtlety in the ABNF for 'variant': variants 196 starting with a digit MAY be four characters long, while those 197 starting with a letter MUST be at least five characters long. 199 All subtags have a maximum length of eight characters and whitespace 200 is not permitted in a language tag. For examples of language tags, 201 see Appendix B. 203 Note that although [RFC2234bis] refers to octets, the language tags 204 described in this document are sequences of characters from the US- 205 ASCII repertoire. Language tags MAY be used in documents and 206 applications that use other encodings, so long as these encompass the 207 US-ASCII repertoire. An example of this would be an XML document 208 that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 210 The tags and their subtags, including private use and extensions, are 211 to be treated as case insensitive: there exist conventions for the 212 capitalization of some of the subtags, but these MUST not be taken to 213 carry meaning. 215 For example: 217 o [ISO639-1] recommends that language codes be written in lower case 218 ('mn' Mongolian). 220 o [ISO3166] recommends that country codes be capitalized ('MN' 221 Mongolia). 223 o [ISO15924] recommends that script codes use lower case with the 224 initial letter capitalized ('Cyrl' Cyrillic). 226 However, in the tags defined by this document, the uppercase US-ASCII 227 letters in the range 'A' through 'Z' are considered equivalent and 228 mapped directly to their US-ASCII lowercase equivalents in the range 229 'a' through 'z'. Thus the tag "mn-Cyrl-MN" is not distinct from "MN- 230 cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these 231 variations conveys the same meaning: Mongolian written in the 232 Cyrillic script as used in Mongolia. 234 2.2 Language Subtag Sources and Interpretation 236 The namespace of language tags and their subtags is administered by 237 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 238 the rules in Section 5 of this document. The registry maintained by 239 IANA is the source for valid subtags: other standards referenced in 240 this section provide the source material for that registry. 242 Terminology in this section: 244 o Tag or tags refers to a complete language tag, such as 245 "fr-Latn-CA". Examples of tags in this document are enclosed in 246 double-quotes ("en-US"). 248 o Subtag refers to a specific section of a tag, delimited by hyphen, 249 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 250 this document are enclosed in single quotes ('Latn'). 252 o Code or codes refers to values defined in external standards (and 253 which are used as subtags in this document). For example, 'Latn' 254 is an [ISO15924] script code which was used to define the 'Latn' 255 script subtag for use in a language tag. Examples of codes in 256 this document are enclosed in single quotes ('en', 'Latn'). 258 The definitions in this section apply to the various subtags within 259 the language tags defined by this document, excepting those 260 "grandfathered" tags defined in Section 2.2.8. 262 Language tags are designed so that each subtag type has unique length 263 and content restrictions. These make identification of the subtag's 264 type possible, even if the content of the subtag itself is 265 unrecognized. This allows tags to be parsed and processed without 266 reference to the latest version of the underlying standards or the 267 IANA registry and makes the associated exception handling when 268 parsing tags simpler. 270 Subtags in the IANA registry that do not come from an underlying 271 standard can only appear in specific positions in a tag. 272 Specifically, they can only occur as primary language subtags or as 273 variant subtags. 275 Note that sequences of private use and extension subtags MUST occur 276 at the end of the sequence of subtags and MUST NOT be interspersed 277 with subtags defined elsewhere in this document. 279 Single letter and digit subtags are reserved for current or future 280 use. These include the following current uses: 282 o The single letter subtag 'x' is reserved to introduce a sequence 283 of private use subtags. The interpretation of any private use 284 subtags is defined solely by private agreement and is not defined 285 by the rules in this section or in any standard or registry 286 defined in this document. 288 o All other single letter subtags are reserved to introduce 289 standardized extension subtag sequences as described in 290 Section 3.6. 292 The single letter subtag 'i' is used by some grandfathered tags, such 293 as "i-enochian", where it always appears in the first position and 294 cannot be confused with an extension. 296 2.2.1 Primary Language Subtag 298 The primary language subtag is the first subtag in a language tag 299 (with the exception of private use and certain grandfathered tags) 300 and cannot be omitted. The following rules apply to the primary 301 language subtag: 303 1. All two character language subtags were defined in the IANA 304 registry according to the assignments found in the standard ISO 305 639 Part 1, "ISO 639-1:2002, Codes for the representation of 306 names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using 307 assignments subsequently made by the ISO 639 Part 1 maintenance 308 agency or governing standardization bodies. 310 2. All three character language subtags were defined in the IANA 311 registry according to the assignments found in ISO 639 Part 2, 312 "ISO 639-2:1998 - Codes for the representation of names of 313 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2], or 314 assignments subsequently made by the ISO 639 Part 2 maintenance 315 agency or governing standardization bodies. 317 3. The subtags in the range 'qaa' through 'qtz' are reserved for 318 private use in language tags. These subtags correspond to codes 319 reserved by ISO 639-2 for private use. These codes MAY be used 320 for non-registered primary-language subtags (instead of using 321 private use subtags following 'x-'). Please refer to Section 4.5 322 for more information on private use subtags. 324 4. All four character language subtags are reserved for possible 325 future standardization. 327 5. All language subtags of 5 to 8 characters in length in the IANA 328 registry were defined via the registration process in Section 3.4 329 and MAY be used to form the primary language subtag. At the time 330 this document was created, there were no examples of this kind of 331 subtag and future registrations of this type will be discouraged: 332 primary languages are strongly RECOMMENDED for registration with 333 ISO 639 and proposals rejected by ISO 639/RA will be closely 334 scrutinized before they are registered with IANA. 336 6. The single character subtag 'x' as the primary subtag indicates 337 that the language tag consists solely of subtags whose meaning is 338 defined by private agreement. For example, in the tag "x-fr-CH", 339 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 340 French language or the country of Switzerland (or any other value 341 in the IANA registry) unless there is a private agreement in 342 place to do so. See Section 4.5. 344 7. The single character subtag 'i' is used by some grandfathered 345 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 346 grandfathered tags have a primary language subtag in their first 347 position) 349 8. Other values MUST NOT be assigned to the primary subtag except by 350 revision or update of this document. 352 Note: For languages that have both an ISO 639-1 two character code 353 and an ISO 639-2 three character code, only the ISO 639-1 two 354 character code is defined in the IANA registry. 356 Note: For languages that have no ISO 639-1 two character code and for 357 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 358 (Bibliographic) codes differ, only the Terminology code is defined in 359 the IANA registry. At the time this document was created, all 360 languages that had both kinds of three character code were also 361 assigned a two character code; it is not expected that future 362 assignments of this nature will occur. 364 Note: To avoid problems with versioning and subtag choice as 365 experienced during the transition between RFC 1766 and RFC 3066, as 366 well as the canonical nature of subtags defined by this document, the 367 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 368 RA-JAC) has included the following statement in [iso639.principles]: 370 "A language code already in ISO 639-2 at the point of freezing ISO 371 639-1 shall not later be added to ISO 639-1. This is to ensure 372 consistency in usage over time, since users are directed in Internet 373 applications to employ the alpha-3 code when an alpha-2 code for that 374 language is not available." 376 In order to avoid instability of the canonical form of tags, if a two 377 character code is added to ISO 639-1 for a language for which a three 378 character code was already included in ISO 639-2, the two character 379 code will not be added as a subtag in the registry. See Section 3.3. 381 For example, if some content were tagged with 'haw' (Hawaiian), which 382 currently has no two character code, the tag would not be invalidated 383 if ISO 639-1 were to assign a two character code to the Hawaiian 384 language at a later date. 386 For example, one of the grandfathered IANA registrations is 387 "i-enochian". The subtag 'enochian' could be registered in the IANA 388 registry as a primary language subtag (assuming that ISO 639 does not 389 register this language first), making tags such as "enochian-AQ" and 390 "enochian-Latn" valid. 392 2.2.2 Extended Language Subtags 394 The following rules apply to the extended language subtags: 396 1. Three letter subtags immediately following the primary subtag are 397 reserved for future standardization, anticipating work that is 398 currently under way on ISO 639. 400 2. Extended language subtags MUST follow the primary subtag and 401 precede any other subtags. 403 3. There MAY be up to three extended language subtags. 405 4. Extended language subtags MUST NOT be registered or used to form 406 language tags. Their syntax is described here so that 407 implementations can be compatible with any future revision of 408 this document which does provide for their registration. 410 Extended language subtag records, once they appear in the registry, 411 MUST include exactly one 'Prefix' field indicating an appropriate 412 language subtag or sequence of subtags that MUST always appear as a 413 prefix to the extended language subtag. 415 Example: In a future revision or update of this document, the tag 416 "zh-gan" (registered under RFC 3066) might become a valid non- 417 grandfathered (that is, redundant) tag in which the subtag 'gan' 418 might represent the Chinese dialect 'Gan'. 420 2.2.3 Script Subtag 422 Script subtags are used to indicate the script or writing system 423 variations that distinguish the written forms of a language or its 424 dialects. The following rules apply to the script subtags: 426 1. All four character subtags were defined according to 427 [ISO15924]--"Codes for the representation of the names of 428 scripts": alpha-4 script codes, or subsequently assigned by the 429 ISO 15924 maintenance agency or governing standardization bodies, 430 denoting the script or writing system used in conjunction with 431 this language. 433 2. Script subtags MUST immediately follow the primary language 434 subtag and all extended language subtags and MUST occur before 435 any other type of subtag described below. 437 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 438 use in language tags. These subtags correspond to codes reserved 439 by ISO 15924 for private use. These codes MAY be used for non- 440 registered script values. Please refer to Section 4.5 for more 441 information on private use subtags. 443 4. Script subtags cannot be registered using the process in 444 Section 3.4 of this document. Variant subtags MAY be considered 445 for registration for that purpose. 447 5. There MUST be at most one script subtag in a language tag and the 448 script subtag SHOULD be omitted when it adds no distinguishing 449 value to the tag or when the primary language subtag's record 450 includes a Suppress-Script field listing the applicable script 451 subtag. 453 Example: "sr-Latn" represents Serbian written using the Latin script. 455 2.2.4 Region Subtag 457 Region subtags are used to indicate linguistic variations associated 458 with or appropriate to a specific country, territory, or region. 459 Typically, a region subtag is used to indicate regional dialects or 460 usage, or region-specific spelling conventions. A region subtag can 461 also be used to indicate that content is expressed in a way that is 462 appropriate for use throughout a region; for instance, Spanish 463 content tailored to be useful throughout Latin America. 465 The following rules apply to the region subtags: 467 1. Region subtags MUST follow any language, extended language, or 468 script subtags and MUST precede all other subtags. 470 2. All two character subtags following the primary subtag were 471 defined in the IANA registry according to the assignments found 472 in [ISO3166]--"Codes for the representation of names of countries 473 and their subdivisions - Part 1: Country codes"--alpha-2 country 474 codes or assignments subsequently made by the ISO 3166 475 maintenance agency or governing standardization bodies. 477 3. All three character subtags consisting of digit (numeric) 478 characters following the primary subtag were defined in the IANA 479 registry according to the assignments found in UN Standard 480 Country or Area Codes for Statistical Use [UN_M.49] or 481 assignments subsequently made by the governing standards body. 482 Note that not all of the UN M.49 codes are defined in the IANA 483 registry. The following rules define which codes are entered 484 into the registry as valid subtags: 486 A. UN numeric codes assigned to 'macro-geographical 487 (continental)' or sub-regions MUST be registered in the 488 registry. These codes are not associated with an assigned 489 ISO 3166 alpha-2 code and represent supra-national areas, 490 usually covering more than one nation, state, province, or 491 territory. 493 B. UN numeric codes for 'economic groupings' or 'other 494 groupings' MUST NOT be registered in the IANA registry and 495 MUST NOT be used to form language tags. 497 C. UN numeric codes for countries or areas with ambiguous ISO 498 3166 alpha-2 codes, when entered into the registry, MUST be 499 defined according to the rules in Section 3.3 and MUST be 500 used to form language tags that represent the country or 501 region for which they are defined. 503 D. UN numeric codes for countries or areas for which there is an 504 associated ISO 3166 alpha-2 code in the registry MUST NOT be 505 entered into the registry and MUST NOT be used to form 506 language tags. Note that the ISO 3166-based subtag in the 507 registry MUST actually be associated with the UN M.49 code in 508 question. 510 E. UN numeric codes and ISO 3166 alpha-2 codes for countries or 511 areas listed as eligible for registration in [initial- 512 registry] but not presently registered MAY be entered into 513 the IANA registry via the process described in Section 3.4. 514 Once registered, these codes MAY be used to form language 515 tags. 517 F. All other UN numeric codes for countries or areas which do 518 not have an associated ISO 3166 alpha-2 code MUST NOT be 519 entered into the registry and MUST NOT be used to form 520 language tags. For more information about these codes, see 521 Section 3.3. 523 4. Note: The alphanumeric codes in Appendix X of the UN document 524 MUST NOT be entered into the registry and MUST NOT be used to 525 form language tags. (At the time this document was created these 526 values match the ISO 3166 alpha-2 codes.) 528 5. There MUST be at most one region subtag in a language tag and the 529 region subtag MAY be omitted, as when it adds no distinguishing 530 value to the tag. 532 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 533 reserved for private use in language tags. These subtags 534 correspond to codes reserved by ISO 3166 for private use. These 535 codes MAY be used for private use region subtags (instead of 536 using a private use subtag sequence). Please refer to 537 Section 4.5 for more information on private use subtags. 539 "de-CH" represents German ('de') as used in Switzerland ('CH'). 541 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 542 ('Latn') as used in Serbia and Montenegro ('CS'). 544 "es-419" represents Spanish ('es') appropriate to the UN-defined 545 Latin America and Caribbean region ('419'). 547 2.2.5 Variant Subtags 549 Variant subtags are used to indicate additional, well-recognized 550 variations that define a language or its dialects which are not 551 covered by other available subtags. The following rules apply to the 552 variant subtags: 554 1. Variant subtags are not associated with any external standard. 555 Variant subtags and their meanings are defined by the 556 registration process defined in Section 3.4. 558 2. Variant subtags MUST follow all of the other defined subtags, but 559 precede any extension or private use subtag sequences. 561 3. More than one variant MAY be used to form the language tag. 563 4. Variant subtags MUST be registered with IANA according to the 564 rules in Section 3.4 of this document before being used to form 565 language tags. In order to distinguish variants from other types 566 of subtags, registrations MUST meet the following length and 567 content restrictions: 569 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 570 at least five characters long. 572 2. Variant subtags that begin with a digit (0-9) MUST be at 573 least four characters long. 575 Variant subtag records in the language subtag registry MAY include 576 one or more 'Prefix' fields, which indicates the language tag or tags 577 that would make a suitable prefix (with other subtags, as 578 appropriate) in forming a language tag with the variant. For 579 example, the subtag 'nedis' has a Prefix of "sl", making it suitable 580 to form language tags such as "sl-nedis" and "sl-IT-nedis", but not 581 suitable for use in a tag such as "zh-nedis" or "it-IT-nedis". 583 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 585 "de-CH-1996" represents German as used in Switzerland and as written 586 using the spelling reform beginning in the year 1996 C.E. 588 Most variants that share a prefix are mutually exclusive. For 589 example, the German orthographic variations '1996' and '1901' SHOULD 590 NOT be used in the same tag, as they represent the dates of different 591 spelling reforms. A variant that can meaningfully be used in 592 combination with another variant SHOULD include a 'Prefix' field in 593 its registry record that lists that other variant. For example, if 594 another German variant 'example' were created that made sense to use 595 with '1996', then 'example' should include two Prefix fields: "de" 596 and "de-1996". 598 2.2.6 Extension Subtags 600 Extensions provide a mechanism for extending language tags for use in 601 various applications. See: Section 3.6. The following rules apply 602 to extensions: 604 1. Extension subtags are separated from the other subtags defined 605 in this document by a single-letter subtag ("singleton"). The 606 singleton MUST be one allocated to a registration authority via 607 the mechanism described in Section 3.6 and cannot be the letter 608 'x', which is reserved for private use subtag sequences. 610 2. Note: Private use subtag sequences starting with the singleton 611 subtag 'x' are described below. 613 3. An extension MUST follow at least a primary language subtag. 614 That is, a language tag cannot begin with an extension. 615 Extensions extend language tags, they do not override or replace 616 them. For example, "a-value" is not a well-formed language tag, 617 while "de-a-value" is. 619 4. Each singleton subtag MUST appear at most one time in each tag 620 (other than as a private use subtag). That is, singleton 621 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 622 ccc" is invalid because the subtag 'a' appears twice. Note that 623 the tag "en-a-bbb-x-a-ccc" is valid because the second 624 appearance of the singleton 'a' is in a private use sequence. 626 5. Extension subtags MUST meet all of the requirements for the 627 content and format of subtags defined in this document. 629 6. Extension subtags MUST meet whatever requirements are set by the 630 document that defines their singleton prefix and whatever 631 requirements are provided by the maintaining authority. 633 7. Each extension subtag MUST be from two to eight characters long 634 and consist solely of letters or digits, with each subtag 635 separated by a single '-'. 637 8. Each singleton MUST be followed by at least one extension 638 subtag. For example, the tag "tlh-a-b-foo" is invalid because 639 the first singleton 'a' is followed immediately by another 640 singleton 'b'. 642 9. Extension subtags MUST follow all language, extended language, 643 script, region and variant subtags in a tag. 645 10. All subtags following the singleton and before another singleton 646 are part of the extension. Example: In the tag "fr-a-Latn", the 647 subtag 'Latn' does not represent the script subtag 'Latn' 648 defined in the IANA Language Subtag Registry. Its meaning is 649 defined by the extension 'a'. 651 11. In the event that more than one extension appears in a single 652 tag, the tag SHOULD be canonicalized as described in 653 Section 4.4. 655 For example, if the prefix singleton 'r' and the shown subtags were 656 defined, then the following tag would be a valid example: "en-Latn- 657 GB-boont-r-extended-sequence-x-private" 659 2.2.7 Private Use Subtags 661 Private use subtags are used to indicate distinctions in language 662 important in a given context by private agreement. The following 663 rules apply to private use subtags: 665 1. Private use subtags are separated from the other subtags defined 666 in this document by the reserved single-character subtag 'x'. 668 2. Private use subtags MUST conform to the format and content 669 constraints defined in the ABNF for all subtags. 671 3. Private use subtags MUST follow all language, extended language, 672 script, region, variant, and extension subtags in the tag. 673 Another way of saying this is that all subtags following the 674 singleton 'x' MUST be considered private use. Example: The 675 subtag 'US' in the tag "en-x-US" is a private use subtag. 677 4. A tag MAY consist entirely of private use subtags. 679 5. No source is defined for private use subtags. Use of private use 680 subtags is by private agreement only. 682 6. Private use subtags are NOT RECOMMENDED where alternatives exist 683 or for general interchange. See Section 4.5 for more information 684 on private use subtag choice. 686 For example: Users who wished to utilize codes from the Ethnologue 687 publication of SIL International for language identification might 688 agree to exchange tags such as "az-Arab-x-AZE-derbend". This example 689 contains two private use subtags. The first is 'AZE' and the second 690 is 'derbend'. 692 2.2.8 Pre-Existing RFC 3066 Registrations 694 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 695 maintain their validity. IANA will maintain these tags in the 696 registry under either the "grandfathered" or "redundant" type. For 697 more information see Section 3.7. 699 It is important to note that all language tags formed under the 700 guidelines in this document were either legal, well-formed tags or 701 could have been registered under RFC 3066. 703 2.2.9 Classes of Conformance 705 Implementations sometimes need to describe their capabilities with 706 regard to the rules and practices described in this document. There 707 are two classes of conforming implementations described by this 708 document: "well-formed" processors and "validating" processors. 709 Claims of conformance SHOULD explicitly reference one of these 710 definitions. 712 An implementation that claims to check for well-formed language tags 713 MUST: 715 o Check that the tag and all of its subtags, including extension and 716 private use subtags, conform to the ABNF or that the tag is on the 717 list of grandfathered tags. 719 o Check that singleton subtags that identify extensions do not 720 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 721 formed. 723 Well-formed processors are strongly encouraged to implement the 724 canonicalization rules contained in Section 4.4. 726 An implementation that claims to be validating MUST: 728 o Check that the tag is well-formed. 730 o Specify the particular registry date for which the implementation 731 performs validation of subtags. 733 o Check that either the tag is a grandfathered tag, or that all 734 language, script, region, and variant subtags consist of valid 735 codes for use in language tags according to the IANA registry as 736 of the particular date specified by the implementation. 738 o Specify which, if any, extension RFCs as defined in Section 3.6 739 are supported, including version, revision, and date. 741 o For any such extensions supported, check that all subtags used in 742 that extension are valid. 744 o For variant and extended language subtags, if the registry 745 contains one or more 'Prefix' fields for that subtag, check that 746 the tag matches at least one prefix. The tag matches if all the 747 subtags in the 'Prefix' also appear in the tag. For example, the 748 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 749 the 'es' language subtag and 'CO' region subtag appear in the tag. 751 3. Registry Format and Maintenance 753 This section defines the Language Subtag Registry and the maintenance 754 and update procedures associated with it. 756 The language subtag registry will be maintained so that, except for 757 extension subtags, it is possible to validate all of the subtags that 758 appear in a language tag under the provisions of this document or its 759 revisions or successors. In addition, the meaning of the various 760 subtags will be unambiguous and stable over time. (The meaning of 761 private use subtags, of course, is not defined by the IANA registry.) 763 The registry defined under this document contains a comprehensive 764 list of all of the subtags valid in language tags. This allows 765 implementers a straightforward and reliable way to validate language 766 tags. 768 3.1 Format of the IANA Language Subtag Registry 770 The IANA Language Subtag Registry ("the registry") will consist of a 771 text file that is machine readable in the format described in this 772 section, plus copies of the registration forms approved by the 773 Language Subtag Reviewer in accordance with the process described in 774 Section 3.4. With the exception of the registration forms for 775 grandfathered and redundant tags, no registration records will be 776 maintained for the initial set of subtags. 778 The registry will be in a modified record-jar format text file 779 [record-jar]. Lines are limited to 72 characters, including all 780 whitespace. 782 Records are separated by lines containing only the sequence "%%" 783 (%x25.25). 785 Each field can be viewed as a single, logical line of ASCII 786 characters, comprising a field-name and a field-body separated by a 787 COLON character (%x3A). For convenience, the field-body portion of 788 this conceptual entity can be split into a multiple-line 789 representation; this is called "folding". The format of the registry 790 is described by the following ABNF (per [RFC2234bis]): 792 registry = record *("%%" CRLF record) 793 record = 1*( field-name *SP ":" *SP field-body CRLF ) 794 field-name = *(ALPHA / DIGIT / "-") 795 field-body = *(ASCCHAR/LWSP) 796 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 797 UNICHAR = "&#x" 2*6HEXDIG ";" 798 The sequence '..' (%x2E.2E) in a field-body denotes a range of 799 values. Such a range represents all subtags of the same length that 800 are alphabetically within that range, including the values explicitly 801 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 803 Characters from outside the US-ASCII repertoire, as well as the 804 AMPERSAND character ("&", %x26) when it occurs in a field-body are 805 represented by a "Numeric Character Reference" using hexadecimal 806 notation in the style used by [XML10] (see 807 ). This consists of the 808 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 809 of the character's code point in [ISO10646] followed by a closing 810 semicolon (%x3B). For example, the EURO SIGN, U+20AC, would be 811 represented by the sequence "€". Note that the hexadecimal 812 notation MAY have between two and six digits. 814 All fields whose field-body contains a date value use the "full-date" 815 format specified in [RFC3339]. For example: "2004-06-28" represents 816 June 28, 2004 in the Gregorian calendar. 818 The first record in the file contains the single field whose field- 819 name is "File-Date". The field-body of this record contains the last 820 modification date of this copy of the registry, making it possible to 821 compare different versions of the registry. The registry on the IANA 822 website is the most current. Versions with an older date than that 823 one are not up-to-date. 825 File-Date: 2004-06-28 826 %% 828 Subsequent records represent subtags in the registry. Each of the 829 fields in each record MUST occur no more than once, unless otherwise 830 noted below. Each record MUST contain the following fields: 832 o 'Type' 834 * Type's field-value MUST consist of one of the following 835 strings: "language", "extlang", "script", "region", "variant", 836 "grandfathered", and "redundant" and denotes the type of tag or 837 subtag. 839 o Either 'Subtag' or 'Tag' 841 * Subtag's field-value contains the subtag being defined. This 842 field MUST only appear in records of whose Type has one of 843 these values: "language", "extlang", "script", "region", or 844 "variant". 846 * Tag's field-value contains a complete language tag. This field 847 MUST only appear in records whose Type has one of these values: 848 "grandfathered" or "redundant". 850 o Description 852 * Description's field-value contains a non-normative description 853 of the subtag or tag. 855 o Added 857 * Added's field-value contains the date the record was added to 858 the registry. 860 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 861 subtag or tag, with two exceptions. Subtags whose 'Type' field is 862 'script' (in other words, subtags defined by ISO 15924) MUST use 863 titlecase. Subtags whose 'Type' field is 'region' (in other words, 864 subtags defined by ISO 3166) MUST use uppercase. These exceptions 865 mirror the use of case in the underlying standards. 867 The field 'Description' MAY appear more than one time. At least one 868 of the 'Description' fields MUST contain a description of the tag 869 being registered written or transcribed into the Latin script; the 870 same or additional fields MAY also include a description in a non- 871 Latin script. The 'Description' field is used for identification 872 purposes and SHOULD NOT be taken to represent the actual native name 873 of the language or variation or to be in any particular language. 874 Most descriptions are taken directly from source standards such as 875 ISO 639 or ISO 3166. 877 Note: Descriptions in registry entries that correspond to ISO 639, 878 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 879 the meaning of that identifier as defined in the source standard at 880 the time it was added to the registry. The description does not 881 replace the content of the source standard itself. The descriptions 882 are not intended to be the English localized names for the subtags. 883 Localization or translation of language tag and subtag descriptions 884 is out of scope of this document. 886 Each record MAY also contain the following fields: 888 o Preferred-Value 890 * For fields of type 'language', 'extlang', 'script', 'region', 891 and 'variant', 'Preferred-Value' contains a subtag of the same 892 'Type' which is preferred for forming the language tag. 894 * For fields of type 'grandfathered' and 'redundant', a canonical 895 mapping to a complete language tag. 897 o Deprecated 899 * Deprecated's field-value contains the date the record was 900 deprecated. 902 o Prefix 904 * Prefix's field-value contains a language tag with which this 905 subtag MAY be used to form a new language tag, perhaps with 906 other subtags as well. This field MUST only appear in records 907 whose 'Type' field-value is 'variant' or 'extlang'. For 908 example, the 'Prefix' for the variant 'nedis' is 'sl', meaning 909 that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate 910 while the tag "is-nedis" is not. 912 o Comments 914 * Comments contains additional information about the subtag, as 915 deemed appropriate for understanding the registry and 916 implementing language tags using the subtag or tag. 918 o Suppress-Script 920 * Suppress-Script contains a script subtag that SHOULD NOT be 921 used to form language tags with the associated primary language 922 subtag. This field MUST only appear in records whose 'Type' 923 field-value is 'language'. See Section 4.1. 925 The field 'Deprecated' MAY be added to any record via the maintenance 926 process described in Section 3.2 or via the registration process 927 described in Section 3.4. Usually the addition of a 'Deprecated' 928 field is due to the action of one of the standards bodies, such as 929 ISO 3166, withdrawing a code. In some historical cases it might not 930 have been possible to reconstruct the original deprecation date. For 931 these cases, an approximate date appears in the registry. Although 932 valid in language tags, subtags and tags with a 'Deprecated' field 933 are deprecated and validating processors SHOULD NOT generate these 934 subtags. Note that a record that contains a 'Deprecated' field and 935 no corresponding 'Preferred-Value' field has no replacement mapping. 937 The field 'Preferred-Value' contains a mapping between the record in 938 which it appears and a tag or subtag which SHOULD be preferred when 939 selected language tags. These values form three groups: 941 ISO 639 language codes which were later withdrawn in favor of 942 other codes. These values are mostly a historical curiosity. 944 ISO 3166 region codes which have been withdrawn in favor of a new 945 code. This sometimes happens when a country changes its name or 946 administration in such a way that warrants a new region code. 948 Tags grandfathered from RFC 3066. In many cases these tags have 949 become obsolete because the values they represent were later 950 encoded by ISO 639. 952 Records that contain a 'Preferred-Value' field MUST also have a 953 'Deprecated' field. This field contains a date of deprecation. Thus 954 a language tag processor can use the registry to construct the valid, 955 non-deprecated set of subtags for a given date. In addition, for any 956 given tag, a processor can construct the set of valid language tags 957 that correspond to that tag for all dates up to the date of the 958 registry. The ability to do these mappings MAY be beneficial to 959 applications that are matching, selecting, for filtering content 960 based on its language tags. 962 Note that 'Preferred-Value' mappings in records of type 'region' MAY 963 NOT represent exactly the same meaning as the original value. There 964 are many reasons for a country code to be changed and the effect this 965 has on the formation of language tags will depend on the nature of 966 the change in question. 968 In particular, the 'Preferred-Value' field does not imply retagging 969 content that uses the affected subtag. 971 The field 'Preferred-Value' MUST NOT be modified once created in the 972 registry. The field MAY be added to records of type "grandfathered" 973 and "region" according to the rules in Section 3.2. Otherwise the 974 field MUST NOT be added to any record already in the registry. 976 The 'Preferred-Value' field in records of type "grandfathered" and 977 "redundant" contains whole language tags that are strongly 978 RECOMMENDED for use in place of the record's value. In many cases 979 the mappings were created by deprecation of the tags during the 980 period before this document was adopted. For example, the tag "no- 981 nyn" was deprecated in favor of the ISO 639-1 defined language code 982 'nn'. 984 Records of type 'variant' MAY have more than one field of type 985 'Prefix'. Additional fields of this type MAY be added to a 'variant' 986 record via the registration process. 988 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 990 The field-value of the 'Prefix' field consists of a language tag 991 whose subtags are appropriate to use with this subtag. For example, 992 the variant subtag '1996' has a Prefix field of "de". This means 993 that tags starting with the sequence "de-" are appropriate with this 994 subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while 995 the tag "fr-1996" is an inappropriate choice. 997 The field of type 'Prefix' MUST NOT be removed from any record. The 998 field-value for this type of field MUST NOT be modified. 1000 The field 'Comments' MAY appear more than once per record. This 1001 field MAY be inserted or changed via the registration process and no 1002 guarantee of stability is provided. The content of this field is not 1003 restricted, except by the need to register the information, the 1004 suitability of the request, and by reasonable practical size 1005 limitations. Long screeds about a particular subtag are frowned 1006 upon. 1008 The field 'Suppress-Script' MUST only appear in records whose 'Type' 1009 field-value is 'language'. This field MAY appear at most one time in 1010 a record. This field indicates a script used to write the 1011 overwhelming majority of documents for the given language and which 1012 therefore adds no distinguishing information to a language tag. It 1013 helps ensure greater compatibility between the language tags 1014 generated according to the rules in this document and language tags 1015 and tag processors or consumers based on RFC 3066. For example, 1016 virtually all Icelandic documents are written in the Latin script, 1017 making the subtag 'Latn' redundant in the tag "is-Latn". 1019 3.2 Maintenance of the Registry 1021 Maintenance of the registry requires that as codes are assigned or 1022 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1023 Subtag Reviewer will evaluate each change, determine whether it 1024 conflicts with existing registry entries, and submit the information 1025 to IANA for inclusion in the registry. If an change takes place and 1026 the Language Subtag Reviewer does not do this in a timely manner, 1027 then any interested party MAY use the procedure in Section 3.4 to 1028 register the appropriate update. 1030 Note: The redundant and grandfathered entries together are the 1031 complete list of tags registered under [RFC3066]. The redundant tags 1032 are those that can now be formed using the subtags defined in the 1033 registry together with the rules of Section 2.2. The grandfathered 1034 entries are those that can never be legal under those same 1035 provisions. 1037 The set of redundant and grandfathered tags is permanent and stable: 1039 no new entries will be added and none of the entries will be removed. 1040 Records of type 'grandfathered' MAY have their type converted to 1041 'redundant': see Section 3.7 for more information. 1043 RFC 3066 tags that were deprecated prior to the adoption of this 1044 document are part of the list of grandfathered tags and their 1045 component subtags were not included as registered variants (although 1046 they remain eligible for registration). For example, the tag "art- 1047 lojban" was deprecated in favor of the language subtag 'jbo'. 1049 The Language Subtag Reviewer MUST ensure that new subtags meet the 1050 requirements in Section 4.1 or submit an appropriate alternate subtag 1051 as described in that section. When either a change or addition to 1052 the registry is needed, the Language Subtag Reviewer MUST prepare the 1053 complete record, including all fields, and forward it to IANA for 1054 insertion into the registry. 1056 If record represents a new subtag that does not currently exist in 1057 the registry, then the message's subject line MUST include the word 1058 "INSERT". If the record represents a change to an existing subtag, 1059 then the subject line of the message MUST include the word "MODIFY". 1060 The message MUST contain both the record for the subtag being 1061 inserted or modified and the new File-Date record. Here is an 1062 example of what the body of the message might contain: 1064 LANGUAGE SUBTAG MODIFICATION 1065 File-Date: 2005-01-02 1066 %% 1067 Type: variant 1068 Subtag: nedis 1069 Description: Natisone dialect 1070 Description: Nadiza dialect 1071 Added: 2003-10-09 1072 Prefix: sl 1073 Comments: This is a comment shown 1074 as an example. 1075 %% 1077 Figure 4 1079 Whenever an entry is created or modified in the registry, the 'File- 1080 Date' record at the start of the registry is updated to reflect the 1081 most recent modification date in the [RFC3339] "full-date" format. 1083 Values in the 'Subtag' field MUST be lowercase except as provided for 1084 in Section 3.1. 1086 3.3 Stability of IANA Registry Entries 1088 The stability of entries and their meaning in the registry is 1089 critical to the long term stability of language tags. The rules in 1090 this section guarantee that a specific language tag's meaning is 1091 stable over time and will not change. 1093 These rules specifically deal with how changes to codes (including 1094 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1095 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1096 Subtag Registry. Assignments to the IANA Language Subtag Registry 1097 MUST follow the following stability rules: 1099 1. Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1100 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1101 guaranteed to be stable over time. 1103 2. Values in the 'Description' field MUST NOT be changed in a way 1104 that would invalidate previously-existing tags. They MAY be 1105 broadened somewhat in scope, changed to add information, or 1106 adapted to the most common modern usage. For example, countries 1107 occasionally change their official names: an historical example 1108 of this would be "Upper Volta" changing to "Burkina Faso". 1110 3. Values in the field 'Prefix' MAY be added to records of type 1111 'variant' via the registration process. 1113 4. Values in the field 'Prefix' MAY be modified, so long as the 1114 modifications broaden the set of prefixes. That is, a prefix 1115 MAY be replaced by one of its own prefixes. For example, the 1116 prefix "en-US" could be replaced by "en", but not by the 1117 prefixes "en-Latn", "fr", or "en-US-boont". If one of those 1118 prefixes were needed, a new Prefix SHOULD be registered. 1120 5. Values in the field 'Prefix' MUST NOT be removed. 1122 6. The field 'Comments' MAY be added, changed, modified, or removed 1123 via the registration process or any of the processes or 1124 considerations described in this section. 1126 7. The field 'Suppress-Script' MAY be added or removed via the 1127 registration process. 1129 8. Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1130 conflict with existing subtags of the associated type and whose 1131 meaning is not the same as an existing subtag of the same type 1132 are entered into the IANA registry as new records. 1134 9. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1135 withdrawn by their respective maintenance or registration 1136 authority remain valid in language tags. A 'Deprecated' field 1137 containing the date of withdrawal is added to the record. If a 1138 new record of the same type is added that represents a 1139 replacement value, then a 'Preferred-Value' field MAY also be 1140 added. The registration process MAY be used to add comments 1141 about the withdrawal of the code by the respective standard. 1143 1. The region code 'TL' was assigned to the country 'Timor- 1144 Leste', replacing the code 'TP' (which was assigned to 'East 1145 Timor' when it was under administration by Portugal). The 1146 subtag 'TP' remains valid in language tags, but its record 1147 contains the a 'Preferred-Value' of 'TL' and its field 1148 'Deprecated' contains the date the new code was assigned 1149 ('2004-07-06'). 1151 10. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1152 with existing subtags of the associated type, including subtags 1153 that are deprecated, MUST NOT be entered into the registry. The 1154 following additional considerations apply to subtag values that 1155 are reassigned: 1157 A. For ISO 639 codes, if the newly assigned code's meaning is 1158 not represented by a subtag in the IANA registry, the 1159 Language Subtag Reviewer, as described in Section 3.4, SHALL 1160 prepare a proposal for entering in the IANA registry as soon 1161 as practical a registered language subtag as an alternate 1162 value for the new code. The form of the registered language 1163 subtag will be at the discretion of the Language Subtag 1164 Reviewer and MUST conform to other restrictions on language 1165 subtags in this document. 1167 B. For all subtags whose meaning is derived from an external 1168 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), 1169 if a new meaning is assigned to an existing code and the new 1170 meaning broadens the meaning of that code, then the meaning 1171 for the associated subtag MAY be changed to match. The 1172 meaning of a subtag MUST NOT be narrowed, however, as this 1173 can result in an unknown proportion of the existing uses of 1174 a subtag becoming invalid. Note: ISO 639 MA/RA has adopted 1175 a similar stability policy. 1177 C. For ISO 15924 codes, if the newly assigned code's meaning is 1178 not represented by a subtag in the IANA registry, the 1179 Language Subtag Reviewer, as described in Section 3.4, SHALL 1180 prepare a proposal for entering in the IANA registry as soon 1181 as practical a registered variant subtag as an alternate 1182 value for the new code. The form of the registered variant 1183 subtag will be at the discretion of the Language Subtag 1184 Reviewer and MUST conform to other restrictions on variant 1185 subtags in this document. 1187 D. For ISO 3166 codes, if the newly assigned code's meaning is 1188 associated with the same UN M.49 code as another 'region' 1189 subtag, then the existing region subtag remains as the 1190 preferred value for that region and no new entry is created. 1191 A comment MAY be added to the existing region subtag 1192 indicating the relationship to the new ISO 3166 code. 1194 E. For ISO 3166 codes, if the newly assigned code's meaning is 1195 associated with a UN M.49 code that is not represented by an 1196 existing region subtag, then the Language Subtag Reviewer, 1197 as described in Section 3.4, SHALL prepare a proposal for 1198 entering the appropriate UN M.49 country code as an entry in 1199 the IANA registry. 1201 F. For ISO 3166 codes, if there is no associated UN numeric 1202 code, then the Language Subtag Reviewer SHALL petition the 1203 UN to create one. If there is no response from the UN 1204 within ninety days of the request being sent, the Language 1205 Subtag Reviewer SHALL prepare a proposal for entering in the 1206 IANA registry as soon as practical a registered variant 1207 subtag as an alternate value for the new code. The form of 1208 the registered variant subtag will be at the discretion of 1209 the Language Subtag Reviewer and MUST conform to other 1210 restrictions on variant subtags in this document. This 1211 situation is very unlikely to ever occur. 1213 11. UN M.49 has codes for both countries and areas (such as '276' 1214 for Germany) and geographical regions and sub-regions (such as 1215 '150' for Europe). UN M.49 country or area codes for which 1216 there is no corresponding ISO 3166 code SHOULD NOT be 1217 registered, except as a surrogate for an ISO 3166 code that is 1218 blocked from registration by an existing subtag. If such a code 1219 becomes necessary, then the registration authority for ISO 3166 1220 SHOULD first be petitioned to assign a code to the region. If 1221 the petition for a code assignment by ISO 3166 is refused or not 1222 acted on in a timely manner, the registration process described 1223 in Section 3.4 MAY then be used to register the corresponding UN 1224 M.49 code. At the time this document was written, there were 1225 only four such codes: 830 (Channel Islands), 831 (Guernsey), 832 1226 (Jersey), and 833 (Isle of Man). This way UN M.49 codes remain 1227 available as the value of last resort in cases where ISO 3166 1228 reassigns a deprecated value in the registry. 1230 12. Stability provisions apply to grandfathered tags with this 1231 exception: should all of the subtags in a grandfathered tag 1232 become valid subtags in the IANA registry, then the field 'Type' 1233 in that record is changed from 'grandfathered' to 'redundant'. 1234 Note that this will not affect language tags that match the 1235 grandfathered tag, since these tags will now match valid 1236 generative subtag sequences. For example, if the subtag 'gan' 1237 in the language tag "zh-gan" were to be registered as an 1238 extended language subtag, then the grandfathered tag "zh-gan" 1239 would be deprecated (but existing content or implementations 1240 that use "zh-gan" would remain valid). 1242 3.4 Registration Procedure for Subtags 1244 The procedure given here MUST be used by anyone who wants to use a 1245 subtag not currently in the IANA Language Subtag Registry. 1247 Only subtags of type 'language' and 'variant' will be considered for 1248 independent registration of new subtags. Handling of subtags needed 1249 for stability and subtags necessary to keep the registry synchronized 1250 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1251 defined by this document are described in Section 3.2. Stability 1252 provisions are described in Section 3.3. 1254 This procedure MAY also be used to register or alter the information 1255 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1256 in a subtag's record as described in Section 3.3. Changes to all 1257 other fields in the IANA registry are NOT permitted. 1259 Registering a new subtag or requesting modifications to an existing 1260 tag or subtag starts with the requester filling out the registration 1261 form reproduced below. Note that each response is not limited in 1262 size so that the request can adequately describe the registration. 1263 The fields in the "Record Requested" section SHOULD follow the 1264 requirements in Section 3.1. 1266 LANGUAGE SUBTAG REGISTRATION FORM 1267 1. Name of requester: 1268 2. E-mail address of requester: 1269 3. Record Requested: 1271 Type: 1272 Subtag: 1273 Description: 1274 Prefix: 1275 Preferred-Value: 1276 Deprecated: 1277 Suppress-Script: 1278 Comments: 1280 4. Intended meaning of the subtag: 1281 5. Reference to published description 1282 of the language (book or article): 1283 6. Any other relevant information: 1285 Figure 5 1287 The subtag registration form MUST be sent to 1288 for a two week review period before it can 1289 be submitted to IANA. (This is an open list and can be joined by 1290 sending a request to .) 1292 Variant and extlang subtags are always registered for use with a 1293 particular range of language tags. For example, the subtag 'rozaj' 1294 is intended for use with language tags that start with the primary 1295 language subtag "sl", since Resian is a dialect of Slovenian. Thus 1296 the subtag 'rozaj' could be included in tags such as "sl-Latn-rozaj" 1297 or "sl-IT-rozaj". This information is stored in the "Prefix" field 1298 in the registry. Variant registration requests are REQUIRED to 1299 include at least one "Prefix" field in the registration form. 1301 The 'Prefix' field for a given registered subtag will be maintained 1302 in the IANA registry as a guide to usage. Additional prefixes MAY be 1303 added by filing an additional registration form. In that form, the 1304 "Any other relevant information:" field MUST indicate that it is the 1305 addition of a prefix. 1307 Requests to add a prefix to a variant subtag that imply a different 1308 semantic meaning will probably be rejected. For example, a request 1309 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1310 nedis" represented some German dialect would be rejected. The 1311 'nedis' subtag represents a particular Slovenian dialect and the 1312 additional registration would change the semantic meaning assigned to 1313 the subtag. A separate subtag SHOULD be proposed instead. 1315 The 'Description' field MUST contain a description of the tag being 1316 registered written or transcribed into the Latin script; it MAY also 1317 include a description in a non-Latin script. Non-ASCII characters 1318 MUST be escaped using the syntax described in Section 3.1. The 1319 'Description' field is used for identification purposes and doesn't 1320 necessarily represent the actual native name of the language or 1321 variation or to be in any particular language. 1323 While the 'Description' field itself is not guaranteed to be stable 1324 and errata corrections MAY be undertaken from time to time, attempts 1325 to provide translations or transcriptions of entries in the registry 1326 itself will probably be frowned upon by the community or rejected 1327 outright, as changes of this nature have an impact on the provisions 1328 in Section 3.3. 1330 The Language Subtag Reviewer is responsible for responding to 1331 requests for the registration of subtags through the registration 1332 process and is appointed by the IESG. 1334 When the two week period has passed the Language Subtag Reviewer 1335 either forwards the record to be inserted or modified to 1336 iana@iana.org according to the procedure described in Section 3.2, or 1337 rejects the request because of significant objections raised on the 1338 list or due to problems with constraints in this document (which MUST 1339 be explicitly cited). The reviewer MAY also extend the review period 1340 in two week increments to permit further discussion. The reviewer 1341 MUST indicate on the list whether the registration has been accepted, 1342 rejected, or extended following each two week period. 1344 Note that the reviewer can raise objections on the list if he or she 1345 so desires. The important thing is that the objection MUST be made 1346 publicly. 1348 The applicant is free to modify a rejected application with 1349 additional information and submit it again; this restarts the two 1350 week comment period. 1352 Decisions made by the reviewer MAY be appealed to the IESG [RFC2028] 1353 under the same rules as other IETF decisions [RFC2026]. 1355 All approved registration forms are available online in the directory 1356 http://www.iana.org/numbers.html under "languages". 1358 Updates or changes to existing records follow the same procedure as 1359 new registrations. The Language Subtag Reviewer decides whether 1360 there is consensus to update the registration following the two week 1361 review period; normally objections by the original registrant will 1362 carry extra weight in forming such a consensus. 1364 Registrations are permanent and stable. Once registered, subtags 1365 will not be removed from the registry and will remain a valid way in 1366 which to specify a specific language or variant. 1368 Note: The purpose of the "Description" in the registration form is 1369 intended as an aid to people trying to verify whether a language is 1370 registered or what language or language variation a particular subtag 1371 refers to. In most cases, reference to an authoritative grammar or 1372 dictionary of that language will be useful; in cases where no such 1373 work exists, other well known works describing that language or in 1374 that language MAY be appropriate. The subtag reviewer decides what 1375 constitutes "good enough" reference material. This requirement is 1376 not intended to exclude particular languages or dialects due to the 1377 size of the speaker population or lack of a standardized orthography. 1378 Minority languages will be considered equally on their own merits. 1380 3.5 Possibilities for Registration 1382 Possibilities for registration of subtags or information about 1383 subtags include: 1385 o Primary language subtags for languages not listed in ISO 639 that 1386 are not variants of any listed or registered language can be 1387 registered. At the time this document was created there were no 1388 examples of this form of subtag. Before attempting to register a 1389 language subtag, there MUST be an attempt to register the language 1390 with ISO 639. No language subtags will be registered for codes 1391 that exist in ISO 639-1 or ISO 639-2, which are under 1392 consideration by the ISO 639 maintenance or registration 1393 authorities, or which have never been attempted for registration 1394 with those authorities. If ISO 639 has previously rejected a 1395 language for registration, it is reasonable to assume that there 1396 must be additional very compelling evidence of need before it will 1397 be registered in the IANA registry (to the extent that it is very 1398 unlikely that any subtags will be registered of this type). 1400 o Dialect or other divisions or variations within a language, its 1401 orthography, writing system, regional or historical usage, 1402 transliteration or other transformation, or distinguishing 1403 variation MAY be registered as variant subtags. An example is the 1404 'rozaj' subtag (the Resian dialect of Slovenian). 1406 o The addition or maintenance of fields (generally of an 1407 informational nature) in Tag or Subtag records as described in 1408 Section 3.1 and subject to the stability provisions in 1409 Section 3.3. This includes descriptions; comments; deprecation 1410 and preferred values for obsolete or withdrawn codes; or the 1411 addition of script or extlang information to primary language 1412 subtags. 1414 o The addition of records and related field value changes necessary 1415 to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and 1416 UN M.49 as described in Section 3.3. 1418 This document leaves the decision on what subtags or changes to 1419 subtags are appropriate (or not) to the registration process 1420 described in Section 3.4. 1422 Note: four character primary language subtags are reserved to allow 1423 for the possibility of alpha4 codes in some future addition to the 1424 ISO 639 family of standards. 1426 ISO 639 defines a maintenance agency for additions to and changes in 1427 the list of languages in ISO 639. This agency is: 1429 International Information Centre for Terminology (Infoterm) 1430 Aichholzgasse 6/12, AT-1120 1431 Wien, Austria 1432 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1434 ISO 639-2 defines a maintenance agency for additions to and changes 1435 in the list of languages in ISO 639-2. This agency is: 1437 Library of Congress 1438 Network Development and MARC Standards Office 1439 Washington, D.C. 20540 USA 1440 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1441 URL: http://www.loc.gov/standards/iso639 1443 The maintenance agency for ISO 3166 (country codes) is: 1445 ISO 3166 Maintenance Agency 1446 c/o International Organization for Standardization 1447 Case postale 56 1448 CH-1211 Geneva 20 Switzerland 1449 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1450 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1452 The registration authority for ISO 15924 (script codes) is: 1454 Unicode Consortium Box 391476 1455 Mountain View, CA 94039-1476, USA 1456 URL: http://www.unicode.org/iso15924 1458 The Statistics Division of the United Nations Secretariat maintains 1459 the Standard Country or Area Codes for Statistical Use and can be 1460 reached at: 1462 Statistical Services Branch 1463 Statistics Division 1464 United Nations, Room DC2-1620 1465 New York, NY 10017, USA 1467 Fax: +1-212-963-0623 1468 E-mail: statistics@un.org 1469 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1471 3.6 Extensions and Extensions Namespace 1473 Extension subtags are those introduced by single-letter subtags other 1474 than 'x'. They are reserved for the generation of identifiers which 1475 contain a language component, and are compatible with applications 1476 that understand language tags. For example, they might be used to 1477 define locale identifiers, which are generally based on language. 1479 The structure and form of extensions are defined by this document so 1480 that implementations can be created that are forward compatible with 1481 applications that might be created using single-letter subtags in the 1482 future. In addition, defining a mechanism for maintaining single- 1483 letter subtags will lend to the stability of this document by 1484 reducing the likely need for future revisions or updates. 1486 Allocation of a single-letter subtag SHALL take the form of an RFC 1487 defining the name, purpose, processes, and procedures for maintaining 1488 the subtags. The maintaining or registering authority, including 1489 name, contact email, discussion list email, and URL location of the 1490 registry MUST be indicated clearly in the RFC. The RFC MUST specify 1491 or include each of the following: 1493 o The specification MUST reference the specific version or revision 1494 of this document that governs its creation and MUST reference this 1495 section of this document. 1497 o The specification and all subtags defined by the specification 1498 MUST follow the ABNF and other rules for the formation of tags and 1499 subtags as defined in this document. In particular it MUST 1500 specify that case is not significant and that subtags MUST NOT 1501 exceed eight characters in length. 1503 o The specification MUST specify a canonical representation. 1505 o The specification of valid subtags MUST be available over the 1506 Internet and at no cost. 1508 o The specification MUST be in the public domain or available via a 1509 royalty-free license acceptable to the IETF and specified in the 1510 RFC. 1512 o The specification MUST be versioned and each version of the 1513 specification MUST be numbered, dated, and stable. 1515 o The specification MUST be stable. That is, extension subtags, 1516 once defined by a specification, MUST NOT be retracted or change 1517 in meaning in any substantial way. 1519 o The specification MUST include in a separate section the 1520 registration form reproduced in this section (below) to be used in 1521 registering the extension upon publication as an RFC. 1523 o IANA MUST be informed of changes to the contact information and 1524 URL for the specification. 1526 IANA will maintain a registry of allocated single-letter (singleton) 1527 subtags. This registry will use the record-jar format described by 1528 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1529 the maintaining authority defined in the RFC MUST forward this 1530 registration form to iesg@ietf.org, who will forward the request to 1531 iana@iana.org. The maintaining authority of the extension MUST 1532 maintain the accuracy of the record by sending an updated full copy 1533 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1534 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1535 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in 1536 these updates. 1538 Failure to maintain this record, the corresponding registry, or meet 1539 other conditions imposed by this section of this document MAY be 1540 appealed to the IESG [RFC2028] under the same rules as other IETF 1541 decisions (see [RFC2026]) and MAY result in the authority to maintain 1542 the extension being withdrawn or reassigned by the IESG. 1544 %% 1545 Identifier: 1546 Description: 1547 Comments: 1548 Added: 1549 RFC: 1550 Authority: 1551 Contact_Email: 1552 Mailing_List: 1553 URL: 1554 %% 1556 Figure 6: Format of Records in the Language Tag Extensions Registry 1558 'Identifier' contains the single letter subtag (singleton) assigned 1559 to the extension. The Internet-Draft submitted to define the 1560 extension SHOULD specify which letter to use, although the IESG MAY 1561 change the assignment when approving the RFC. 1563 'Description' contains the name and description of the extension. 1565 'Comments' is an OPTIONAL field and MAY contain a broader description 1566 of the extension. 1568 'Added' contains the date the RFC was published in the "full-date" 1569 format specified in [RFC3339]. For example: 2004-06-28 represents 1570 June 28, 2004, in the Gregorian calendar. 1572 'RFC' contains the RFC number assigned to the extension. 1574 'Authority' contains the name of the maintaining authority for the 1575 extension. 1577 'Contact_Email' contains the email address used to contact the 1578 maintaining authority. 1580 'Mailing_List' contains the URL or subscription email address of the 1581 mailing list used by the maintaining authority. 1583 'URL' contains the URL of the registry for this extension. 1585 The determination of whether an Internet-Draft meets the above 1586 conditions and the decision to grant or withhold such authority rests 1587 solely with the IESG, and is subject to the normal review and appeals 1588 process associated with the RFC process. 1590 Extension authors are strongly cautioned that many (including most 1591 well-formed) processors will be unaware of any special relationships 1592 or meaning inherent in the order of extension subtags. Extension 1593 authors SHOULD avoid subtag relationships or canonicalization 1594 mechanisms that interfere with matching or with length restrictions 1595 that sometimes exist in common protocols where the extension is used. 1596 In particular, applications MAY truncate the subtags in doing 1597 matching or in fitting into limited lengths, so it is RECOMMENDED 1598 that the most significant information be in the most significant 1599 (left-most) subtags, and that the specification gracefully handle 1600 truncated subtags. 1602 When a language tag is to be used in a specific, known, protocol, it 1603 is RECOMMENDED that that the language tag not contain extensions not 1604 supported by that protocol. In addition, note that some protocols 1605 MAY impose upper limits on the length of the strings used to store or 1606 transport the language tag. 1608 3.7 Initialization of the Registry 1610 Adoption of this document will REQUIRE an initial version of the 1611 registry containing the various subtags initially valid in a language 1612 tag. This collection of subtags, along with a description of the 1613 process used to create it, is described by [initial-registry]. 1615 Registrations that are in process under the rules defined in 1616 [RFC3066] when this document is adopted MAY be completed under the 1617 former rules, at the discretion of the language tag reviewer. Any 1618 new registrations submitted after the adoption of this document MUST 1619 be rejected. 1621 4. Formation and Processing of Language Tags 1623 This section addresses how to use the information in the registry 1624 with the tag syntax to choose, form and process language tags. 1626 4.1 Choice of Language Tag 1628 One is sometimes faced with the choice between several possible tags 1629 for the same body of text. 1631 Interoperability is best served when all users use the same language 1632 tag in order to represent the same language. If an application has 1633 requirements that make the rules here inapplicable, then that 1634 application risks damaging interoperability. It is strongly 1635 RECOMMENDED that users not define their own rules for language tag 1636 choice. 1638 Subtags SHOULD only be used where they add useful distinguishing 1639 information; extraneous subtags interfere with the meaning, 1640 understanding, and processing of language tags. In particular, users 1641 and implementations SHOULD follow the 'Prefix' and 'Suppress-Script' 1642 fields in the registry (defined in Section 3.1): these fields provide 1643 guidance on when specific additional subtags SHOULD (and SHOULD NOT) 1644 be used in a language tag. 1646 Of particular note, many applications can benefit from the use of 1647 script subtags in language tags, as long as the use is consistent for 1648 a given context. Script subtags were not formally defined in RFC 1649 3066 and their use can affect matching and subtag identification by 1650 implementations of RFC 3066, as these subtags appear between the 1651 primary language and region subtags. For example, if a user requests 1652 content in an implementation of Section 2.5 of [RFC3066] using the 1653 language range "en-US", content labeled "en-Latn-US" will not match 1654 the request. Therefore it is important to know when script subtags 1655 will customarily be used and when they ought not be used. In the 1656 registry, the Suppress-Script field helps ensure greater 1657 compatibility between the language tags generated according to the 1658 rules in this document and language tags and tag processors or 1659 consumers based on RFC 3066 by defining when users SHOULD NOT include 1660 a script subtag with a particular primary language subtag. 1662 Extended language subtags (type 'extlang' in the registry, see 1663 Section 3.1) also appear between the primary language and region 1664 subtags and are reserved for future standardization. Applications 1665 might benefit from their judicious use in forming language tags in 1666 the future. Similar recommendations are expected to apply to their 1667 use as apply to script subtags. 1669 Standards, protocols and applications that reference this document 1670 normatively but apply different rules to the ones given in this 1671 section MUST specify how the procedure varies from the one given 1672 here. 1674 The choice of subtags used to form a language tag SHOULD be guided by 1675 the following rules: 1677 1. Use as precise a tag as possible, but no more specific than is 1678 justified. Avoid using subtags that are not important for 1679 distinguishing content in an application. 1681 * For example, 'de' might suffice for tagging an email written 1682 in German, while "de-CH-1996" is probably unnecessarily 1683 precise for such a task. 1685 2. The script subtag SHOULD NOT be used to form language tags unless 1686 the script adds some distinguishing information to the tag. The 1687 field 'Suppress-Script' in the primary language record in the 1688 registry indicates which script subtags do not add distinguishing 1689 information for most applications. 1691 * For example, the subtag 'Latn' should not be used with the 1692 primary language 'en' because nearly all English documents are 1693 written in the Latin script and it adds no distinguishing 1694 information. However, if a document were written in English 1695 mixing Latin script with another script such as Braille 1696 ('Brai'), then it might be appropriate to choose to indicate 1697 both scripts to aid in content selection, such as the 1698 application of a style sheet. 1700 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1701 entry, then the value of that field SHOULD be used to form the 1702 language tag in preference to the tag or subtag in which the 1703 preferred value appears. 1705 * For example, use 'he' for Hebrew in preference to 'iw'. 1707 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1708 used to label content, even if the language is unknown. Omitting 1709 the language tag altogether is preferred to using a tag with a 1710 primary language subtag of 'und'. The 'und' subtag MAY be useful 1711 for protocols that require a language tag to be provided. The 1712 'und' subtag MAY also be useful when matching language tags in 1713 certain situations. 1715 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1716 whenever the protocol allows the separate tags for multiple 1717 languages, as is the case for the Content-Language header in 1718 HTTP. The 'mul' subtag conveys little useful information: 1719 content in multiple languages SHOULD individually tag the 1720 languages where they appear or otherwise indicate the actual 1721 language in preference to the 'mul' subtag. 1723 6. The same variant subtag SHOULD NOT be used more than once within 1724 a language tag. 1726 * For example, do not use "de-DE-1901-1901". 1728 To ensure consistent backward compatibility, this document contains 1729 several provisions to account for potential instability in the 1730 standards used to define the subtags that make up language tags. 1731 These provisions mean that no language tag created under the rules in 1732 this document will become obsolete. 1734 4.2 Meaning of the Language Tag 1736 The relationship between the tag and the information it relates to is 1737 defined by the context in which the tag appears. Accordingly, this 1738 section can only give possible examples of its usage. 1740 o For a single information object, the associated language tags 1741 might be interpreted as the set of languages that is necessary for 1742 a complete comprehension of the complete object. Example: Plain 1743 text documents. 1745 o For an aggregation of information objects, the associated language 1746 tags could be taken as the set of languages used inside components 1747 of that aggregation. Examples: Document stores and libraries. 1749 o For information objects whose purpose is to provide alternatives, 1750 the associated language tags could be regarded as a hint that the 1751 content is provided in several languages, and that one has to 1752 inspect each of the alternatives in order to find its language or 1753 languages. In this case, the presence of multiple tags might not 1754 mean that one needs to be multi-lingual to get complete 1755 understanding of the document. Example: MIME multipart/ 1756 alternative. 1758 o In markup languages, such as HTML and XML, language information 1759 can be added to each part of the document identified by the markup 1760 structure (including the whole document itself). For example, one 1761 could write C'est la vie. inside a 1762 Norwegian document; the Norwegian-speaking user could then access 1763 a French-Norwegian dictionary to find out what the marked section 1764 meant. If the user were listening to that document through a 1765 speech synthesis interface, this formation could be used to signal 1766 the synthesizer to appropriately apply French text-to-speech 1767 pronunciation rules to that span of text, instead of applying the 1768 inappropriate Norwegian rules. 1770 Language tags are related when they contain a similar sequence of 1771 subtags. For example, if a language tag B contains language tag A as 1772 a prefix, then B is typically "narrower" or "more specific" than A. 1773 Thus "zh-Hant-TW" is more specific than "zh-Hant". 1775 This relationship is not guaranteed in all cases: specifically, 1776 languages that begin with the same sequence of subtags are NOT 1777 guaranteed to be mutually intelligible, although they might be. For 1778 example, the tag "az" shares a prefix with both "az-Latn" 1779 (Azerbaijani written using the Latin script) and "az-Cyrl" 1780 (Azerbaijani written using the Cyrillic script). A person fluent in 1781 one script might not be able to read the other, even though the text 1782 might be identical. Content tagged as "az" most probably is written 1783 in just one script and thus might not be intelligible to a reader 1784 familiar with the other script. 1786 4.3 Length Considerations 1788 [RFC3066] did not provide an upper limit on the size of language 1789 tags. While RFC 3066 did define the semantics of particular subtags 1790 in such a way that most language tags consisted of language and 1791 region subtags with a combined total length of up to six characters, 1792 larger registered tags were not only possible but were actually 1793 registered. 1795 Neither the language tag syntax nor other requirements in this 1796 document impose a fixed upper limit on the number of subtags in a 1797 language tag (and thus an upper bound on the size of a tag). The 1798 language tag syntax suggests that, depending on the specific 1799 language, more subtags (and thus a longer tag) are sometimes 1800 necessary to completely identify the language for certain 1801 applications; thus it is possible to envision long or complex subtag 1802 sequences. 1804 4.3.1 Working with Limited Buffer Sizes 1806 Some applications and protocols are forced to allocate fixed buffer 1807 sizes or otherwise limit the length of a language tag. A conformant 1808 implementation or specification MAY refuse to support the storage of 1809 language tags which exceed a specified length. Any such limitation 1810 SHOULD be clearly documented, and such documentation SHOULD include 1811 what happens to longer tags (for example, whether an error value is 1812 generated or the language tag is truncated). A protocol that allows 1813 tags to be truncated at an arbitrary limit, without giving any 1814 indication of what that limit is, has the potential for causing harm 1815 by changing the meaning of tags in substantial ways. 1817 In practice, most language tags do not require more than a few 1818 subtags and will not approach reasonably sized buffer limitations: 1819 see Section 4.1. 1821 Some specifications or protocols have limits on tag length but do not 1822 have a fixed length limitation. For example, [RFC2231] has no 1823 explicit length limitation: the length available for the language tag 1824 is constrained by the length of other header components (such as the 1825 charset's name) coupled with the 76 character limit in [RFC2047]. 1826 Thus the "limit" might be 50 or more characters, but it could 1827 potentially be quite small. 1829 The considerations for assigning a buffer limit are: 1831 Implementations SHOULD NOT truncate language tags unless the 1832 meaning of the tag is purposefully being changed, or unless the 1833 tag does not fit into a limited buffer size specified by a 1834 protocol for storage or transmission. 1836 Implementations SHOULD warn the user when a tag is truncated since 1837 truncation changes the semantic meaning of the tag. 1839 Implementations of protocols or specifications that are space 1840 constrained but do not have a fixed limit SHOULD use the longest 1841 possible tag in preference to truncation. 1843 Protocols or specifications that specify limited buffer sizes for 1844 language tags MUST allow for language tags of up to 33 characters. 1846 Protocols or specifications that specify limited buffer sizes for 1847 language tags SHOULD allow for language tags of at least 42 1848 characters. 1850 The following illustration shows how the 42-character recommendation 1851 was derived. The combination of language and extended language 1852 subtags was chosen for future compatibility. At up to 15 characters, 1853 this combination is longer than the longest possible primary language 1854 subtag (8 characters): 1856 language = 3 (ISO 639-2; ISO 639-1 requires 2) 1857 extlang1 = 4 (each subsequent subtag includes '-') 1858 extlang2 = 4 (unlikely: needs prefix="language-extlang1") 1859 extlang3 = 4 (extremely unlikely) 1860 script = 5 (if not suppressed: see Section 4.1) 1861 region = 4 (UN M.49; ISO 3166 requires 3) 1862 variant1 = 9 (MUST have language as a prefix) 1863 variant2 = 9 (MUST have language-variant1 as a prefix) 1865 total = 42 characters 1867 Figure 7: Derivation of the Limit on Tag Length 1869 4.3.2 Truncation of Language Tags 1871 Truncation of a language tag alters the meaning of the tag, and thus 1872 SHOULD be avoided. However, truncation of language tags is sometimes 1873 necessary due to limited buffer sizes. Such truncation MUST NOT 1874 permit a subtag to be chopped off in the middle or the formation of 1875 invalid tags (for example, one ending with the "-" character). 1877 This means that applications or protocols which truncate tags MUST do 1878 so by progressively removing subtags along with their preceding "-" 1879 from the right side of the language tag until the tag is short enough 1880 for the given buffer. If the resulting tag ends with a single- 1881 character subtag, that subtag and its preceding "-" MUST also be 1882 removed. For example: 1884 Tag to truncate: zh-Hant-CN-variant1-a-extend1-x-wadegile-private1 1885 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 1886 2. zh-Latn-CN-variant1-a-extend1 1887 3. zh-Latn-CN-variant1 1888 4. zh-Latn-CN 1889 5. zh-Latn 1890 6. zh 1892 Figure 8: Example of Tag Truncation 1894 4.4 Canonicalization of Language Tags 1896 Since a particular language tag is sometimes used by many processes, 1897 language tags SHOULD always be created or generated in a canonical 1898 form. 1900 A language tag is in canonical form when: 1902 1. The tag is well-formed according the rules in Section 2.1 and 1903 Section 2.2. 1905 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1906 the IANA registry (see Section 3.1) SHOULD be replaced with their 1907 mapped value. 1909 3. Redundant or grandfathered tags that have a Preferred-Value 1910 mapping in the IANA registry (see Section 3.1) MUST be replaced 1911 with their mapped value. These items are either deprecated 1912 mappings created before the adoption of this document (such as 1913 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1914 the result of later registrations or additions to this document 1915 (for example, "zh-guoyu" might be mapped to a language-extlang 1916 combination such as "zh-cmn" by some future update of this 1917 document). 1919 4. Other subtags that have a Preferred-Value mapping in the IANA 1920 registry (see Section 3.1) MUST be replaced with their mapped 1921 value. These items consist entirely of clerical corrections to 1922 ISO 639-1 in which the deprecated subtags have been maintained 1923 for compatibility purposes. 1925 5. If more than one extension subtag sequence exists, the extension 1926 sequences are ordered into case-insensitive ASCII order by 1927 singleton subtag. 1929 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1930 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1931 canonical form. 1933 Example: The language tag "en-NH" (English as used in the New 1934 Hebrides) is not canonical because the 'NH' subtag has a canonical 1935 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1936 validity. 1938 Canonicalization of language tags does not imply anything about the 1939 use of upper or lowercase letters when processing or comparing 1940 subtags (and as described in Section 2.1). All comparisons MUST be 1941 performed in a case-insensitive manner. 1943 When performing canonicalization of language tags, processors MAY 1944 regularize the case of the subtags (that is, this process is 1945 OPTIONAL), following the case used in the registry. Note that this 1946 corresponds to the following casing rules: uppercase all non-initial 1947 two-letter subtags; titlecase all non-initial four-letter subtags; 1948 lowercase everything else. 1950 Note: Case folding of ASCII letters in certain locales, unless 1951 carefully handled, sometimes produces non-ASCII character values. 1952 The Unicode Character Database file "SpecialCasing.txt" defines the 1953 specific cases that are known to cause problems with this. In 1954 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1955 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1956 Implementers SHOULD specify a locale-neutral casing operation to 1957 ensure that case folding of subtags does not produce this value, 1958 which is illegal in language tags. For example, if one were to 1959 uppercase the region subtag 'in' using Turkish locale rules, the 1960 sequence U+0130 U+004E would result instead of the expected 'IN'. 1962 Note: if the field 'Deprecated' appears in a registry record without 1963 an accompanying 'Preferred-Value' field, then that tag or subtag is 1964 deprecated without a replacement. Validating processors SHOULD NOT 1965 generate tags that include these values, although the values are 1966 canonical when they appear in a language tag. 1968 An extension MUST define any relationships that exist between the 1969 various subtags in the extension and thus MAY define an alternate 1970 canonicalization scheme for the extension's subtags. Extensions MAY 1971 define how the order of the extension's subtags are interpreted. For 1972 example, an extension could define that its subtags are in canonical 1973 order when the subtags are placed into ASCII order: that is, "en-a- 1974 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1975 define that the order of the subtags influences their semantic 1976 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1977 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1978 so that they are tolerant of the typical processes described in 1979 Section 3.6. 1981 4.5 Considerations for Private Use Subtags 1983 Private use subtags, like all other subtags, MUST conform to the 1984 format and content constraints in the ABNF. Private use subtags have 1985 no meaning outside the private agreement between the parties that 1986 intend to use or exchange language tags that employ them. The same 1987 subtags could be used with a different meaning under a separate 1988 private agreement. They SHOULD NOT be used where alternatives exist 1989 and SHOULD NOT be used in content or protocols intended for general 1990 use. 1992 Private use subtags are simply useless for information exchange 1993 without prior arrangement. The value and semantic meaning of private 1994 use tags and of the subtags used within such a language tag are not 1995 defined by this document. 1997 Subtags defined in the IANA registry as having a specific private use 1998 meaning convey more information that a purely private use tag 1999 prefixed by the singleton subtag 'x'. For applications this 2000 additional information MAY be useful. 2002 For example, the region subtags 'AA', 'ZZ' and in the ranges 2003 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 2004 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 2005 great deal of public, interchangeable information about the language 2006 material (that it is Chinese in the simplified Chinese script and is 2007 suitable for some geographic region 'XQ'). While the precise 2008 geographic region is not known outside of private agreement, the tag 2009 conveys far more information than an opaque tag such as "x-someLang", 2010 which contains no information about the language subtag or script 2011 subtag outside of the private agreement. 2013 However, in some cases content tagged with private use subtags MAY 2014 interact with other systems in a different and possibly unsuitable 2015 manner compared to tags that use opaque, privately defined subtags, 2016 so the choice of the best approach sometimes depends on the 2017 particular domain in question. 2019 5. IANA Considerations 2021 This section deals with the processes and requirements necessary for 2022 IANA to undertake to maintain the subtag and extension registries as 2023 defined by this document and in accordance with the requirements of 2024 [RFC2434]. 2026 The impact on the IANA maintainers of the two registries defined by 2027 this document will be a small increase in the frequency of new 2028 entries or updates. 2030 5.1 Language Subtag Registry 2032 Upon adoption of this document, the registry will be initialized by a 2033 companion document: [initial-registry]. The criteria and process for 2034 selecting the initial set of records is described in that document. 2035 The initial set of records represents no impact on IANA, since the 2036 work to create it will be performed externally. 2038 The new registry MUST be listed under "Language Tags" at 2039 , replacing the existing 2040 registrations defined by [RFC3066]. The existing set of registration 2041 forms and RFC 3066 registrations will be relabeled as "Language Tags 2042 (Obsolete)" and maintained (but not added to or modified). 2044 Future work on the Language Subtag Registry will be limited to 2045 inserting or replacing whole records preformatted for IANA by the 2046 Language Subtag Reviewer as described in Section 3.2 of this 2047 document. This simplifies IANA's work by limiting it to placing the 2048 text in the appropriate location in the registry. 2050 Each record will be sent to iana@iana.org with a subject line 2051 indicating whether the enclosed record is an insertion of a new 2052 record (indicated by the word "INSERT" in the subject line) or a 2053 replacement of an existing record (indicated by the word "MODIFY" in 2054 the subject line). Records MUST NOT be deleted from the registry. 2055 IANA MUST place any inserted or modified records into the appropriate 2056 section of the language subtag registry, grouping the records by 2057 their "Type" field. Inserted records MAY be placed anywhere in the 2058 appropriate section; there is no guarantee of the order of the 2059 records beyond grouping them together by 'Type'. Modified records 2060 MUST overwrite the record they replace. 2062 Included in any request to insert or modify records MUST be a new 2063 File-Date record. This record MUST be placed first in the registry. 2064 In the event that the File-Date record present in the registry has a 2065 later date then the record being inserted or modified, the existing 2066 record MUST be preserved. 2068 5.2 Extensions Registry 2070 The Language Tag Extensions registry will also be generated and sent 2071 to IANA as described in Section 3.6. This registry can contain at 2072 most 35 records and thus changes to this registry are expected to be 2073 very infrequent. 2075 Future work by IANA on the Language Tag Extensions Registry is 2076 limited to two cases. First, the IESG MAY request that new records 2077 be inserted into this registry from time to time. These requests 2078 will include the record to insert in the exact format described in 2079 Section 3.6. In addition, there MAY be occasional requests from the 2080 maintaining authority for a specific extension to update the contact 2081 information or URLs in the record. These requests MUST include the 2082 complete, updated record. IANA is not responsible for validating the 2083 information provided, only that it is properly formatted. It should 2084 reasonably be seen to come from the maintaining authority named in 2085 the record present in the registry. 2087 6. Security Considerations 2089 Language tags used in content negotiation, like any other information 2090 exchanged on the Internet, might be a source of concern because they 2091 might be used to infer the nationality of the sender, and thus 2092 identify potential targets for surveillance. 2094 This is a special case of the general problem that anything sent is 2095 visible to the receiving party and possibly to third parties as well. 2096 It is useful to be aware that such concerns can exist in some cases. 2098 The evaluation of the exact magnitude of the threat, and any possible 2099 countermeasures, is left to each application protocol (see BCP 72 2100 [RFC3552] for best current practice guidance on security threats and 2101 defenses). 2103 The language tag associated with a particular information item is of 2104 no consequence whatsoever in determining whether that content might 2105 contain possible homographs. The fact that a text is tagged as being 2106 in one language or using a particular script subtag provides no 2107 assurance whatsoever that it does not contain characters from scripts 2108 other than the one(s) associated with or specified by that language 2109 tag. 2111 Since there is no limit to the number of variant, private use, and 2112 extension subtags, and consequently no limit on the possible length 2113 of a tag, implementations need to guard against buffer overflow 2114 attacks. See Section 4.3 for details on language tag truncation, 2115 which can occur as a consequence of defenses against buffer overflow. 2117 Although the specification of valid subtags for an extension (see: 2118 Section 3.6) MUST be available over the Internet, implementations 2119 SHOULD NOT mechanically depend on it being always accessible, to 2120 prevent denial-of-service attacks. 2122 7. Character Set Considerations 2124 The syntax in this document requires that language tags use only the 2125 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2126 character sets, so the composition of language tags should not have 2127 any character set issues. 2129 Rendering of characters based on the content of a language tag is not 2130 addressed in this memo. Historically, some languages have relied on 2131 the use of specific character sets or other information in order to 2132 infer how a specific character should be rendered (notably this 2133 applies to language and culture specific variations of Han ideographs 2134 as used in Japanese, Chinese, and Korean). When language tags are 2135 applied to spans of text, rendering engines can use that information 2136 in deciding which font to use in the absence of other information, 2137 particularly where languages with distinct writing traditions use the 2138 same characters. 2140 8. Changes from RFC 3066 2142 The main goals for this revision of language tags were the following: 2144 *Compatibility.* All RFC 3066 language tags (including those in the 2145 IANA registry) remain valid in this specification. The changes in 2146 this document represent additional constraints on language tags. 2147 That is, in no case is the syntax more permissive and processors 2148 based on the RFC 3066 ABNF (such as those described in [XMLSchema]) 2149 will be able to process the tags described by this document. In 2150 addition, this document defines language tags in such as way as to 2151 ensure future compatibility. 2153 *Stability.* Because of changes in the past in the underlying ISO 2154 standards, a valid RFC 3066 language tag could become invalid or have 2155 its meaning change. This has the potential of invalidating content 2156 that may have an extensive shelf-life. In this specification, once a 2157 language tag is valid, it remains valid forever. 2159 *Validity.* The structure of language tags defined by this document 2160 makes it possible to determine if a particular tag is well-formed 2161 without regard for the actual content or "meaning" of the tag as a 2162 whole. This is important because the registry grows and underlying 2163 standards change over time. In addition, it must be possible to 2164 determine if a tag is valid (or not) for a given point in time in 2165 order to provide reproducible, testable results. This process must 2166 not be error-prone; otherwise implementations might give different 2167 results. By having an authoritative registry with specific 2168 versioning information, the validity of language tags at any point in 2169 time can be precisely determined (instead of interpolating values 2170 from many separate sources). 2172 *Utility.* It is sometimes important to be able to differentiate 2173 between written forms of a language -- for many implementations this 2174 is more important than distinguishing between the spoken variants of 2175 a language. Languages are written in a wide variety of different 2176 scripts, so this document provides for the generative use of ISO 2177 15924 script codes. Like the generative use of ISO language and 2178 country codes in RFC 3066, this allows combinations to be produced 2179 without resorting to the registration process. The addition of UN 2180 M.49 codes provides for the generation of language tags with regional 2181 scope, which is also required by some applications. 2183 The recast of the registry from containing whole language tags to 2184 subtags is a key part of this. An important feature of RFC 3066 was 2185 that it allowed generative use of subtags. This allows people to 2186 meaningfully use generated tags, without the delays in registering 2187 whole tags or the need to register all of the combinations that might 2188 be useful. 2190 The choice of placing the extended language and script subtags 2191 between the primary language and region subtags was widely debated. 2192 This design was chosen because the prevalent matching and content 2193 negotiation schemes rely on the subtags being arranged in order of 2194 increasing specificity. That is, the subtags that mark a greater 2195 barrier to mutual intelligibility appear left-most in a tag. For 2196 example, when selecting content written in Azerbaijani, the script 2197 (Arabic, Cyrillic, or Latin) represents a greater barrier to 2198 understanding than any regional variations (those associated with 2199 Azerbaijan or Iran, for example). Individuals who prefer documents 2200 in a particular script, but can deal with the minor regional 2201 differences, can therefore select appropriate content. Applications 2202 that do not deal with written content will continue to omit these 2203 subtags. 2205 *Extensibility.* Because of the widespread use of language tags, it 2206 is disruptive to have periodic revisions of the core specification, 2207 even in the face of demonstrated need. The extension mechanism 2208 provides for a way for independent RFCs to define extensions to 2209 language tags. These extensions have a very constrained, well- 2210 defined structure that prevent extensions from interfering with 2211 implementations of language tags defined in this document. 2213 The document also anticipates features of ISO 639-3 with the addition 2214 of the extended language subtags, as well as the possibility of other 2215 ISO 639 parts becoming useful for the formation of language tags in 2216 the future. 2218 The use and definition of private use tags has also been modified, to 2219 allow people to use private use subtags to extend or modify defined 2220 tags and to move as much information as possible out of private use 2221 and into the regular structure. 2223 The goal for each of these modifications is to reduce or eliminate 2224 the need for future revisions of this document. 2226 The specific changes in this document to meet these goals are: 2228 o Defines the ABNF and rules for subtags so that the category of all 2229 subtags can be determined without reference to the registry. 2231 o Adds the concept of well-formed vs. validating processors, 2232 defining the rules by which an implementation can claim to be one 2233 or the other. 2235 o Replaces the IANA language tag registry with a language subtag 2236 registry that provides a complete list of valid subtags in the 2237 IANA registry. This allows for robust implementation and ease of 2238 maintenance. The language subtag registry becomes the canonical 2239 source for forming language tags. 2241 o Provides a process that guarantees stability of language tags, by 2242 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2243 the event that they register a previously used value for a new 2244 purpose. 2246 o Allows ISO 15924 script code subtags and allows them to be used 2247 generatively. Defines a method for indicating in the registry 2248 when script subtags are necessary for a given language tag. 2250 o Adds the concept of a variant subtag and allows variants to be 2251 used generatively. 2253 o Adds the ability to use a class of UN M.49 tags for supra- 2254 national regions and to resolve conflicts in the assignment of ISO 2255 3166 codes. 2257 o Defines the private use tags in ISO 639, ISO 15924, and ISO 3166 2258 as the mechanism for creating private use language, script, and 2259 region subtags respectively. 2261 o Adds a well-defined extension mechanism. 2263 o Defines an extended language subtag, possibly for use with certain 2264 anticipated features of ISO 639-3. 2266 Ed Note: The following items are provided for the convenience of 2267 reviewers and will be removed from the final document. 2269 Changes between draft-ietf-ltru-registry-08 and this version are: 2271 o Added a reference URI to the editor's address. (F.Ellermann) 2273 o Various nit fixings. 2275 o Fixed rule #11 in Section 3.3 to allow UN M.49 codes to be 2276 registered in extreme situations (#1026) (F.Ellermann, R.Presuhn, 2277 etc.) 2279 o Added more cautionary text about private use subtags to 2280 Section 4.5. (#1061) (D.Pierce) 2282 o Regularized "private-use" to always use the form "private use". 2283 (A.Phillips) 2285 o Additional wordsmithing on rule #11 in Section 3.3. (F.Ellermann) 2287 9. References 2289 9.1 Normative References 2291 [ISO639-1] 2292 International Organization for Standardization, "ISO 639- 2293 1:2002, Codes for the representation of names of languages 2294 -- Part 1: Alpha-2 code", ISO Standard 639, 2002, . 2297 [ISO639-2] 2298 International Organization for Standardization, "ISO 639- 2299 2:1998 - Codes for the representation of names of 2300 languages -- Part 2: Alpha-3 code - edition 1", 2301 August 1988, . 2303 [ISO15924] 2304 ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2305 representation of names of scripts", January 2004, . 2308 [ISO3166] International Organization for Standardization, "Codes for 2309 the representation of names of countries, 3rd edition", 2310 ISO Standard 3166, August 1988, . 2312 [UN_M.49] Statistical Division, United Nations, "Standard Country or 2313 Area Codes for Statistical Use", UN Standard Country or 2314 Area Codes for Statistical Use, Revision 4 (United Nations 2315 publication, Sales No. 98.XVII.9, June 1999, . 2317 [ISO10646] 2318 International Organization for Standardization, "ISO/IEC 2319 10646-1:2000. Information technology -- Universal 2320 Multiple-Octet Coded Character Set (UCS) -- Part 1: 2321 Architecture and Basic Multilingual Plane and ISO/IEC 2322 10646-2:2001. Information technology -- Universal 2323 Multiple-Octet Coded Character Set (UCS) -- Part 2: 2324 Supplementary Planes, as, from time to time, amended, 2325 replaced by a new edition or expanded by the addition of 2326 new parts", 2000, . 2328 [RFC2234bis] 2329 Crocker, D. and P. Overell, "Augmented BNF for Syntax 2330 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 2331 (work in progress), March 2005. 2333 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 2334 3", BCP 9, RFC 2026, October 1996. 2336 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 2337 the IETF Standards Process", BCP 11, RFC 2028, 2338 October 1996. 2340 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 2341 Part Three: Message Header Extensions for Non-ASCII Text", 2342 RFC 2047, November 1996. 2344 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2345 Requirement Levels", BCP 14, RFC 2119, March 1997. 2347 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2348 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 2349 October 1998. 2351 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 2352 10646", RFC 2781, February 2000. 2354 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2355 Understanding Concerning the Technical Work of the 2356 Internet Assigned Numbers Authority", RFC 2860, June 2000. 2358 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2359 Timestamps", RFC 3339, July 2002. 2361 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2362 Text on Security Considerations", BCP 72, RFC 3552, 2363 July 2003. 2365 9.2 Informative References 2367 [initial-registry] 2368 Ewell, D., Ed., "Initial Language Subtag Registry", 2369 June 2005, . 2372 [iso639.principles] 2373 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2374 Committee: Working principles for ISO 639 maintenance", 2375 March 2000, 2376 . 2379 [record-jar] 2380 Raymond, E., "The Art of Unix Programming", 2003. 2382 [XML10] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2383 02 2004. 2385 [XMLSchema] 2386 Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2387 Datatypes Second Edition", 10 2004, < 2388 http://www.w3.org/TR/xmlschema-2/>. 2390 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 2391 Standard, Version 4.1.0, defined by: The Unicode Standard, 2392 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2393 18578-1), as amended by Unicode 4.0.1 2394 (http://www.unicode.org/versions/Unicode4.0.1) and by 2395 Unicode 4.1.0 2396 (http://www.unicode.org/versions/Unicode4.1.0).", 2397 March 2005. 2399 [RFC1766] Alvestrand, H., "Tags for the Identification of 2400 Languages", RFC 1766, March 1995. 2402 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 2403 Word Extensions: Character Sets, Languages, and 2404 Continuations", RFC 2231, November 1997. 2406 [RFC3066] Alvestrand, H., "Tags for the Identification of 2407 Languages", BCP 47, RFC 3066, January 2001. 2409 Authors' Addresses 2411 Addison Phillips (editor) 2412 Quest Software 2414 Email: addison.phillips@quest.com 2415 URI: http://www.inter-locale.com 2417 Mark Davis (editor) 2418 IBM 2420 Email: mark.davis@us.ibm.com 2422 Appendix A. Acknowledgements 2424 Any list of contributors is bound to be incomplete; please regard the 2425 following as only a selection from the group of people who have 2426 contributed to make this document what it is today. 2428 The contributors to RFC 3066 and RFC 1766, the precursors of this 2429 document, made enormous contributions directly or indirectly to this 2430 document and are generally responsible for the success of language 2431 tags. 2433 The following people (in alphabetical order) contributed to this 2434 document or to RFCs 1766 and 3066: 2436 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2437 Nathaniel Borenstein, Karen Broome, Eric Brunner, Sean M. Burke, M.T. 2438 Carrasco Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter 2439 Constable, John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, 2440 Frank Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, 2441 Dirk-Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty 2442 Harold, Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle 2443 Jarnefors, Kent Karlsson, John Klensin, Alain LaBonte, Eric Mader, 2444 Ira McDonald, Keith Moore, Chris Newman, Masataka Ohta, Dylan Pierce, 2445 Randy Presuhn, George Rhoten, Markus Scherer, Keld Jorn Simonsen, 2446 Thierry Sourbier, Otto Stolz, Tex Texin, Andrea Vine, Rhys 2447 Weatherley, Misha Wolf, Francois Yergeau and many, many others. 2449 Very special thanks must go to Harald Tveit Alvestrand, who 2450 originated RFCs 1766 and 3066, and without whom this document would 2451 not have been possible. Special thanks must go to Michael Everson, 2452 who has served as language tag reviewer for almost the complete 2453 period since the publication of RFC 1766. Special thanks to Doug 2454 Ewell, for his production of the first complete subtag registry, and 2455 his work in producing a test parser for verifying language tags. 2457 Appendix B. Examples of Language Tags (Informative) 2459 Simple language subtag: 2461 de (German) 2463 fr (French) 2465 ja (Japanese) 2467 i-enochian (example of a grandfathered tag) 2469 Language subtag plus Script subtag: 2471 zh-Hant (Chinese written using the Traditional Chinese script) 2473 zh-Hans (Chinese written using the Simplified Chinese script) 2475 sr-Cyrl (Serbian written using the Cyrillic script) 2477 sr-Latn (Serbian written using the Latin script) 2479 Language-Script-Region: 2481 zh-Hans-CN (Chinese written using the Simplified script as used in 2482 mainland China) 2484 sr-Latn-CS (Serbian written using the Latin script as used in 2485 Serbia and Montenegro) 2487 Language-Variant: 2489 sl-rozaj (Resian dialect of Slovenian 2491 sl-nedis (Nadiza dialect of Slovenian) 2493 Language-Region-Variant: 2495 de-CH-1901 (German as used in Switzerland using the 1901 variant 2496 [orthography]) 2498 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 2500 Language-Script-Region-Variant: 2502 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2503 Latin script as used in Italy. Note that this tag is NOT 2504 RECOMMENDED because subtag 'sl' has a Suppress-Script value of 2505 'Latn') 2507 Language-Region: 2509 de-DE (German for Germany) 2511 en-US (English as used in the United States) 2513 es-419 (Spanish appropriate for the Latin America and Caribbean 2514 region using the UN region code) 2516 Private use subtags: 2518 de-CH-x-phonebk 2520 az-Arab-x-AZE-derbend 2522 Extended language subtags (examples ONLY: extended languages MUST be 2523 defined by revision or update to this document): 2525 zh-min 2527 zh-min-nan-Hant-CN 2529 Private use registry values: 2531 x-whatever (private use using the singleton 'x') 2533 qaa-Qaaa-QM-x-southern (all private tags) 2535 de-Qaaa (German, with a private script) 2537 sr-Latn-QM (Serbian, Latin-script, private region) 2539 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2541 Tags that use extensions (examples ONLY: extensions MUST be defined 2542 by revision or update to this document or by RFC): 2544 en-US-u-islamCal 2546 zh-CN-a-myExt-x-private 2547 en-a-myExt-b-another 2549 Some Invalid Tags: 2551 de-419-DE (two region tags) 2553 a-DE (use of a single character subtag in primary position; note 2554 that there are a few grandfathered tags that start with "i-" that 2555 are valid) 2557 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2558 prefix) 2560 Intellectual Property Statement 2562 The IETF takes no position regarding the validity or scope of any 2563 Intellectual Property Rights or other rights that might be claimed to 2564 pertain to the implementation or use of the technology described in 2565 this document or the extent to which any license under such rights 2566 might or might not be available; nor does it represent that it has 2567 made any independent effort to identify any such rights. Information 2568 on the procedures with respect to rights in RFC documents can be 2569 found in BCP 78 and BCP 79. 2571 Copies of IPR disclosures made to the IETF Secretariat and any 2572 assurances of licenses to be made available, or the result of an 2573 attempt made to obtain a general license or permission for the use of 2574 such proprietary rights by implementers or users of this 2575 specification can be obtained from the IETF on-line IPR repository at 2576 http://www.ietf.org/ipr. 2578 The IETF invites any interested party to bring to its attention any 2579 copyrights, patents or patent applications, or other proprietary 2580 rights that may cover technology that may be required to implement 2581 this standard. Please address the information to the IETF at 2582 ietf-ipr@ietf.org. 2584 Disclaimer of Validity 2586 This document and the information contained herein are provided on an 2587 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2588 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2589 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2590 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2591 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2592 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2594 Copyright Statement 2596 Copyright (C) The Internet Society (2005). This document is subject 2597 to the rights, licenses and restrictions contained in BCP 78, and 2598 except as set forth therein, the authors retain all their rights. 2600 Acknowledgment 2602 Funding for the RFC Editor function is currently provided by the 2603 Internet Society.