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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. There are many reasons for a country code to be changed and the effect this has on the formation of language tags will depend on the nature of the change in question. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (June 24, 2005) is 6881 days in the past. Is this intentional? 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 2366, 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 (==), 15 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Phillips, Ed. 3 Internet-Draft Quest Software 4 Expires: December 26, 2005 M. Davis, Ed. 5 IBM 6 June 24, 2005 8 Tags for Identifying Languages 9 draft-ietf-ltru-registry-07 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on December 26, 2005. 36 Copyright Notice 38 Copyright (C) The Internet Society (2005). 40 Abstract 42 This document describes the structure, content, construction, and 43 semantics of language tags for use in cases where it is desirable to 44 indicate the language used in an information object. It also 45 describes how to register values for use in language tags and the 46 creation of user defined extensions for private interchange. This 47 document obsoletes RFC 3066 (which replaced RFC 1766). 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4 53 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 2.2 Language Subtag Sources and Interpretation . . . . . . . . 6 55 2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 7 56 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 9 57 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 10 58 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 11 59 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 12 60 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 14 61 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 15 62 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 15 63 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 16 64 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 18 65 3.1 Format of the IANA Language Subtag Registry . . . . . . . 18 66 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 23 67 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 25 68 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 28 69 3.5 Possibilities for Registration . . . . . . . . . . . . . . 31 70 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 33 71 3.7 Initialization of the Registry . . . . . . . . . . . . . . 36 72 4. Formation and Processing of Language Tags . . . . . . . . . . 37 73 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 37 74 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 39 75 4.3 Length Considerations . . . . . . . . . . . . . . . . . . 40 76 4.3.1 Working with Limited Buffer Sizes . . . . . . . . . . 40 77 4.3.2 Truncation of Language Tags . . . . . . . . . . . . . 42 78 4.4 Canonicalization of Language Tags . . . . . . . . . . . . 42 79 4.5 Considerations for Private Use Subtags . . . . . . . . . . 44 80 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 81 5.1 Language Subtag Registry . . . . . . . . . . . . . . . . . 46 82 5.2 Extensions Registry . . . . . . . . . . . . . . . . . . . 47 83 6. Security Considerations . . . . . . . . . . . . . . . . . . . 48 84 7. Character Set Considerations . . . . . . . . . . . . . . . . . 49 85 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 50 86 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53 87 9.1 Normative References . . . . . . . . . . . . . . . . . . . 53 88 9.2 Informative References . . . . . . . . . . . . . . . . . . 54 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 55 90 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 56 91 B. Examples of Language Tags (Informative) . . . . . . . . . . . 57 92 Intellectual Property and Copyright Statements . . . . . . . . 60 94 1. Introduction 96 Human beings on our planet have, past and present, used a number of 97 languages. There are many reasons why one would want to identify the 98 language used when presenting or requesting information. 100 User's language preferences often need to be identified so that 101 appropriate processing can be applied. For example, the user's 102 language preferences in a Web browser can be used to select Web pages 103 appropriately. Language preferences can also be used to select among 104 tools (such as dictionaries) to assist in the processing or 105 understanding of content in different languages. 107 In addition, knowledge about the particular language used by some 108 piece of information content might be useful or even required by some 109 types of processing; for example spell-checking, computer-synthesized 110 speech, Braille transcription, or high-quality print renderings. 112 One means of indicating the language used is by labeling the 113 information content with an identifier or "tag". These tags can be 114 used to specify user preferences when selecting information content, 115 or for labeling additional attributes of content and associated 116 resources. 118 Tags can also be used to indicate additional language attributes of 119 content. For example, indicating specific information about the 120 dialect, writing system, or orthography used in a document or 121 resource may enable the user to obtain information in a form that 122 they can understand, or important in processing or rendering the 123 given content into an appropriate form or style. 125 This document specifies a particular identifier mechanism (the 126 language tag) and a registration function for values to be used to 127 form tags. It also defines a mechanism for private use values and 128 future extension. 130 This document replaces RFC 3066, which replaced RFC 1766. For a list 131 of changes in this document, see Section 8. 133 The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in [RFC2119]. 137 2. The Language Tag 139 The language tag always defines a language as used (which includes 140 being spoken, written, signed, or otherwise signaled) by human 141 beings for communication of information to other human beings. 142 Computer languages such as programming languages are explicitly 143 excluded. 145 2.1 Syntax 147 The language tag is composed of one or more parts or "subtags". Each 148 subtag consists of a sequence of alpha-numeric characters. Subtags 149 are distinguished and separated from one another by a hyphen ("-"). 150 A language tag consists of a "primary language" subtag and a 151 (possibly empty) series of subsequent subtags, each of which refines 152 or narrows the range of language identified by the overall tag. 154 Each type of subtag is distinguished by length, position in the tag, 155 and content: subtags can be recognized solely by these features. 156 This makes it possible to construct a parser that can extract and 157 assign some semantic information to the subtags, even if the specific 158 subtag values are not recognized. Thus a parser need not have an up- 159 to-date copy (or any copy at all) of the subtag registry to perform 160 most searching and matching operations. 162 The syntax of the language tag in ABNF [RFC2234bis] is: 164 Language-Tag = (lang 165 *3("-" extlang) 166 ["-" script] 167 ["-" region] 168 *("-" variant) 169 *("-" extension) 170 ["-" privateuse]) 171 / privateuse ; private-use tag 172 / grandfathered ; grandfathered registrations 174 lang = 2*4ALPHA ; shortest ISO 639 code 175 / registered-lang 176 extlang = 3ALPHA ; reserved for future use 177 script = 4ALPHA ; ISO 15924 code 178 region = 2ALPHA ; ISO 3166 code 179 / 3DIGIT ; UN country number 180 variant = 5*8alphanum ; registered variants 181 / ( DIGIT 3alphanum ) 182 extension = singleton 1*("-" (2*8alphanum)) 183 privateuse = ("x"/"X") 1*("-" (1*8alphanum)) 184 singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT 185 ; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z" / "0"-"9" 186 ; Single letters: x/X is reserved for private use 187 registered-lang = 4*8ALPHA ; registered language subtag 188 grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum)) 189 ; grandfathered registration 190 ; Note: i is the only singleton 191 ; that starts a grandfathered tag 192 alphanum = (ALPHA / DIGIT) ; letters and numbers 194 Figure 1: Language Tag ABNF 196 The character "-" is HYPHEN-MINUS (ABNF: %x2D). All subtags have a 197 maximum length of eight characters. Note that there is a subtlety in 198 the ABNF for 'variant': variants starting with a digit MAY be four 199 characters long, while those starting with a letter MUST be at least 200 five characters long. 202 Whitespace is not permitted in a language tag. For examples of 203 language tags, see Appendix B. 205 Note that although [RFC2234bis] refers to octets, the language tags 206 described in this document are sequences of characters from the US- 207 ASCII repertoire. Language tags MAY be used in documents and 208 applications that use other encodings, so long as these encompass the 209 US-ASCII repertoire. An example of this would be an XML document 210 that uses the UTF-16LE [RFC2781] encoding of [Unicode]. 212 The tags and their subtags, including private-use and extensions, are 213 to be treated as case insensitive: there exist conventions for the 214 capitalization of some of the subtags, but these MUST not be taken to 215 carry meaning. 217 For example: 219 o [ISO639-1] recommends that language codes be written in lower case 220 ('mn' Mongolian). 222 o [ISO3166] recommends that country codes be capitalized ('MN' 223 Mongolia). 225 o [ISO15924] recommends that script codes use lower case with the 226 initial letter capitalized ('Cyrl' Cyrillic). 228 However, in the tags defined by this document, the uppercase US-ASCII 229 letters in the range 'A' through 'Z' are considered equivalent and 230 mapped directly to their US-ASCII lowercase equivalents in the range 231 'a' through 'z'. Thus the tag "mn-Cyrl-MN" is not distinct from "MN- 232 cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these 233 variations conveys the same meaning: Mongolian written in the 234 Cyrillic script as used in Mongolia. 236 2.2 Language Subtag Sources and Interpretation 238 The namespace of language tags and their subtags is administered by 239 the Internet Assigned Numbers Authority (IANA) [RFC2860] according to 240 the rules in Section 5 of this document. The registry maintained by 241 IANA is the source for valid subtags: other standards referenced in 242 this section provide the source material for that registry. 244 Terminology in this section: 246 o Tag or tags refers to a complete language tag, such as 247 "fr-Latn-CA". Examples of tags in this document are enclosed in 248 double-quotes ("en-US"). 250 o Subtag refers to a specific section of a tag, delimited by hyphen, 251 such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in 252 this document are enclosed in single quotes ('Latn'). 254 o Code or codes refers to values defined in external standards (and 255 which are used as subtags in this document). For example, 'Latn' 256 is an [ISO15924] script code which was used to define the 'Latn' 257 script subtag for use in a language tag. Examples of codes in 258 this document are enclosed in single quotes ('en', 'Latn'). 260 The definitions in this section apply to the various subtags within 261 the language tags defined by this document, excepting those 262 "grandfathered" tags defined in Section 2.2.8. 264 Language tags are designed so that each subtag type has unique length 265 and content restrictions. These make identification of the subtag's 266 type possible, even if the content of the subtag itself is 267 unrecognized. This allows tags to be parsed and processed without 268 reference to the latest version of the underlying standards or the 269 IANA registry and makes the associated exception handling when 270 parsing tags simpler. 272 Subtags in the IANA registry that do not come from an underlying 273 standard can only appear in specific positions in a tag. 274 Specifically, they can only occur as primary language subtags or as 275 variant subtags. 277 Note that sequences of private-use and extension subtags MUST occur 278 at the end of the sequence of subtags and MUST NOT be interspersed 279 with subtags defined elsewhere in this document. 281 Single letter and digit subtags are reserved for current or future 282 use. These include the following current uses: 284 o The single letter subtag 'x' is reserved to introduce a sequence 285 of private-use subtags. The interpretation of any private-use 286 subtags is defined solely by private agreement and is not defined 287 by the rules in this section or in any standard or registry 288 defined in this document. 290 o All other single letter subtags are reserved to introduce 291 standardized extension subtag sequences as described in 292 Section 3.6. 294 The single letter subtag 'i' is used by some grandfathered tags, such 295 as "i-enochian", where it always appears in the first position and 296 cannot be confused with an extension. 298 2.2.1 Primary Language Subtag 300 The primary language subtag is the first subtag in a language tag 301 (with the exception of private-use and certain grandfathered tags) 302 and cannot be omitted. The following rules apply to the primary 303 language subtag: 305 1. All two character language subtags were defined in the IANA 306 registry according to the assignments found in the standard ISO 307 639 Part 1, "ISO 639-1:2002, Codes for the representation of 308 names of languages -- Part 1: Alpha-2 code" [ISO639-1], or using 309 assignments subsequently made by the ISO 639 Part 1 maintenance 310 agency or governing standardization bodies. 312 2. All three character language subtags were defined in the IANA 313 registry according to the assignments found in ISO 639 Part 2, 314 "ISO 639-2:1998 - Codes for the representation of names of 315 languages -- Part 2: Alpha-3 code - edition 1" [ISO639-2], or 316 assignments subsequently made by the ISO 639 Part 2 maintenance 317 agency or governing standardization bodies. 319 3. The subtags in the range 'qaa' through 'qtz' are reserved for 320 private use in language tags. These subtags correspond to codes 321 reserved by ISO 639-2 for private use. These codes MAY be used 322 for non-registered primary-language subtags (instead of using 323 private-use subtags following 'x-'). Please refer to Section 4.5 324 for more information on private use subtags. 326 4. All four character language subtags are reserved for possible 327 future standardization. 329 5. All language subtags of 5 to 8 characters in length in the IANA 330 registry were defined via the registration process in Section 3.4 331 and MAY be used to form the primary language subtag. At the time 332 this document was created, there were no examples of this kind of 333 subtag and future registrations of this type will be discouraged: 334 primary languages are strongly RECOMMENDED for registration with 335 ISO 639 and proposals rejected by ISO 639/RA will be closely 336 scrutinized before they are registered with IANA. 338 6. The single character subtag 'x' as the primary subtag indicates 339 that the language tag consists solely of subtags whose meaning is 340 defined by private agreement. For example, in the tag "x-fr-CH", 341 the subtags 'fr' and 'CH' SHOULD NOT be taken to represent the 342 French language or the country of Switzerland (or any other value 343 in the IANA registry) unless there is a private agreement in 344 place to do so. See Section 4.5. 346 7. The single character subtag 'i' is used by some grandfathered 347 tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other 348 grandfathered tags have a primary language subtag in their first 349 position) 351 8. Other values MUST NOT be assigned to the primary subtag except by 352 revision or update of this document. 354 Note: For languages that have both an ISO 639-1 two character code 355 and an ISO 639-2 three character code, only the ISO 639-1 two 356 character code is defined in the IANA registry. 358 Note: For languages that have no ISO 639-1 two character code and for 359 which the ISO 639-2/T (Terminology) code and the ISO 639-2/B 360 (Bibliographic) codes differ, only the Terminology code is defined in 361 the IANA registry. At the time this document was created, all 362 languages that had both kinds of three character code were also 363 assigned a two character code; it is not expected that future 364 assignments of this nature will occur. 366 Note: To avoid problems with versioning and subtag choice as 367 experienced during the transition between RFC 1766 and RFC 3066, as 368 well as the canonical nature of subtags defined by this document, the 369 ISO 639 Registration Authority Joint Advisory Committee (ISO 639/ 370 RA-JAC) has included the following statement in [iso639.principles]: 372 "A language code already in ISO 639-2 at the point of freezing ISO 373 639-1 shall not later be added to ISO 639-1. This is to ensure 374 consistency in usage over time, since users are directed in Internet 375 applications to employ the alpha-3 code when an alpha-2 code for that 376 language is not available." 378 In order to avoid instability of the canonical form of tags, if a two 379 character code is added to ISO 639-1 for a language for which a three 380 character code was already included in ISO 639-2, the two character 381 code will not be added as a subtag in the registry. See Section 3.3. 383 For example, if some content were tagged with 'haw' (Hawaiian), which 384 currently has no two character code, the tag would not be invalidated 385 if ISO 639-1 were to assign a two character code to the Hawaiian 386 language at a later date. 388 For example, one of the grandfathered IANA registrations is 389 "i-enochian". The subtag 'enochian' could be registered in the IANA 390 registry as a primary language subtag (assuming that ISO 639 does not 391 register this language first), making tags such as "enochian-AQ" and 392 "enochian-Latn" valid. 394 2.2.2 Extended Language Subtags 396 The following rules apply to the extended language subtags: 398 1. Three letter subtags immediately following the primary subtag are 399 reserved for future standardization, anticipating work that is 400 currently under way on ISO 639. 402 2. Extended language subtags MUST follow the primary subtag and 403 precede any other subtags. 405 3. There MAY be up to three extended language subtags. 407 4. Extended language subtags MUST NOT be registered or used to form 408 language tags. Their syntax is described here so that 409 implementations can be compatible with any future revision of 410 this document which does provide for their registration. 412 Extended language subtag records, once they appear in the registry, 413 MUST include exactly one 'Prefix' field indicating an appropriate 414 language subtag or sequence of subtags that MUST always appear as a 415 prefix to the extended language subtag. 417 Example: In a future revision or update of this document, the tag 418 "zh-gan" (registered under RFC 3066) might become a valid non- 419 grandfathered (that is, redundant) tag in which the subtag 'gan' 420 might represent the Chinese dialect 'Gan'. 422 2.2.3 Script Subtag 424 Script subtags are used to indicate the script or writing system 425 variations that distinguish the written forms of a language or its 426 dialects. The following rules apply to the script subtags: 428 1. All four character subtags were defined according to 429 [ISO15924]--"Codes for the representation of the names of 430 scripts": alpha-4 script codes, or subsequently assigned by the 431 ISO 15924 maintenance agency or governing standardization bodies, 432 denoting the script or writing system used in conjunction with 433 this language. 435 2. Script subtags MUST immediately follow the primary language 436 subtag and all extended language subtags and MUST occur before 437 any other type of subtag described below. 439 3. The script subtags 'Qaaa' through 'Qabx' are reserved for private 440 use in language tags. These subtags correspond to codes reserved 441 by ISO 15924 for private use. These codes MAY be used for non- 442 registered script values. Please refer to Section 4.5 for more 443 information on private-use subtags. 445 4. Script subtags cannot be registered using the process in 446 Section 3.4 of this document. Variant subtags MAY be considered 447 for registration for that purpose. 449 5. There MUST be at most one script subtag in a language tag and the 450 script subtag SHOULD be omitted when it adds no distinguishing 451 value to the tag or when the primary language subtag's record 452 includes a Supress-Script field listing the applicable script 453 subtag. 455 Example: "sr-Latn" represents Serbian written using the Latin script. 457 2.2.4 Region Subtag 459 Region subtags are used to indicate linguistic variations associated 460 with or appropriate to a specific country, territory, or region. 461 Typically, a region subtag is used to indicate regional dialects or 462 usage, or region-specific spelling conventions. A region subtag can 463 also be used to indicate that content is expressed in a way that is 464 appropriate for use throughout a region; for instance, Spanish 465 content tailored to be useful throughout Latin America. 467 The following rules apply to the region subtags: 469 1. Region subtags MUST follow any language, extended language, or 470 script subtags and MUST precede all other subtags. 472 2. All two character subtags following the primary subtag were 473 defined in the IANA registry according to the assignments found 474 in [ISO3166]--"Codes for the representation of names of countries 475 and their subdivisions - Part 1: Country codes"--alpha-2 country 476 codes or assignments subsequently made by the ISO 3166 477 maintenance agency or governing standardization bodies. 479 3. All three character subtags consisting of digit (numeric) 480 characters following the primary subtag were defined in the IANA 481 registry according to the assignments found in UN Standard 482 Country or Area Codes for Statistical Use [UN_M.49] or 483 assignments subsequently made by the governing standards body. 484 Note that not all of the UN M.49 codes are defined in the IANA 485 registry. The following rules define which codes are entered 486 into the registry as valid subtags: 488 A. UN numeric codes assigned to 'macro-geographical 489 (continental)' or sub-regions MUST be registered in the 490 registry. These codes are not associated with an assigned 491 ISO 3166 alpha-2 code and represent supra-national areas, 492 usually covering more than one nation, state, province, or 493 territory. 495 B. UN numeric codes for 'economic groupings' or 'other 496 groupings' MUST NOT be registered in the IANA registry and 497 MUST NOT be used to form language tags. 499 C. UN numeric codes for countries or areas with ambiguous ISO 500 3166 alpha-2 codes, when entered into the registry, MUST be 501 defined according to the rules in Section 3.3 and MUST be 502 used to form language tags that represent the country or 503 region for which they are defined. 505 D. UN numeric codes for countries or areas for which there is an 506 associated ISO 3166 alpha-2 code in the registry MUST NOT be 507 entered into the registry and MUST NOT be used to form 508 language tags. Note that the ISO 3166-based subtag in the 509 registry MUST actually be associated with the UN M.49 code in 510 question. 512 E. All other UN numeric codes for countries or areas which do 513 not have an associated ISO 3166 alpha-2 code MUST NOT be 514 entered into the registry and MUST NOT be used to form 515 language tags. For more information about these codes, see 516 Section 3.3. 518 4. Note: The alphanumeric codes in Appendix X of the UN document 519 MUST NOT be entered into the registry and MUST NOT be used to 520 form language tags. (At the time this document was created these 521 values match the ISO 3166 alpha-2 codes.) 523 5. There MUST be at most one region subtag in a language tag and the 524 region subtag MAY be omitted, as when it adds no distinguishing 525 value to the tag. 527 6. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are 528 reserved for private use in language tags. These subtags 529 correspond to codes reserved by ISO 3166 for private use. These 530 codes MAY be used for private use region subtags (instead of 531 using a private-use subtag sequence). Please refer to 532 Section 4.5 for more information on private use subtags. 534 "de-CH" represents German ('de') as used in Switzerland ('CH'). 536 "sr-Latn-CS" represents Serbian ('sr') written using Latin script 537 ('Latn') as used in Serbia and Montenegro ('CS'). 539 "es-419" represents Spanish ('es') appropriate to the UN-defined 540 Latin America and Caribbean region ('419'). 542 2.2.5 Variant Subtags 544 Variant subtags are used to indicate additional, well-recognized 545 variations that define a language or its dialects which are not 546 covered by other available subtags. The following rules apply to the 547 variant subtags: 549 1. Variant subtags are not associated with any external standard. 550 Variant subtags and their meanings are defined by the 551 registration process defined in Section 3.4. 553 2. Variant subtags MUST follow all of the other defined subtags, but 554 precede any extension or private-use subtag sequences. 556 3. More than one variant MAY be used to form the language tag. 558 4. Variant subtags MUST be registered with IANA according to the 559 rules in Section 3.4 of this document before being used to form 560 language tags. In order to distinguish variants from other types 561 of subtags, registrations MUST meet the following length and 562 content restrictions: 564 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 565 at least five characters long. 567 2. Variant subtags that begin with a digit (0-9) MUST be at 568 least four characters long. 570 Variant subtag records in the language subtag registry MAY include 571 one or more 'Prefix' fields, which indicates the language tag or tags 572 that would make a suitable prefix (with other subtags, as 573 appropriate) in forming a language tag with the variant. For 574 example, the subtag 'nedis' has a Prefix of "sl", making it suitable 575 to form language tags such as "sl-nedis" and "sl-IT-nedis", but not 576 suitable for use in a tag such as "zh-nedis" or "it-IT-nedis". 578 "sl-nedis" represents the Natisone or Nadiza dialect of Slovenian. 580 "de-CH-1996" represents German as used in Switzerland and as written 581 using the spelling reform beginning in the year 1996 C.E. 583 Most variants that share a prefix are mutually exclusive. For 584 example, the German orthographic variations '1996' and '1901' SHOULD 585 NOT be used in the same tag, as they represent the dates of different 586 spelling reforms. A variant that can meaningfully be used in 587 combination with another variant SHOULD include a 'Prefix' field in 588 its registry record that lists that other variant. For example, if 589 another German variant 'example' were created that made sense to use 590 with '1996', then 'example' should include two Prefix fields: "de" 591 and "de-1996". 593 2.2.6 Extension Subtags 595 Extensions provide a mechanism for extending language tags for use in 596 various applications. See: Section 3.6. The following rules apply 597 to extensions: 599 1. Extension subtags are separated from the other subtags defined 600 in this document by a single-letter subtag ("singleton"). The 601 singleton MUST be one allocated to a registration authority via 602 the mechanism described in Section 3.6 and cannot be the letter 603 'x', which is reserved for private-use subtag sequences. 605 2. Note: Private-use subtag sequences starting with the singleton 606 subtag 'x' are described below. 608 3. An extension MUST follow at least a primary language subtag. 609 That is, a language tag cannot begin with an extension. 610 Extensions extend language tags, they do not override or replace 611 them. For example, "a-value" is not a well-formed language tag, 612 while "de-a-value" is. 614 4. Each singleton subtag MUST appear at most one time in each tag 615 (other than as a private-use subtag). That is, singleton 616 subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a- 617 ccc" is invalid because the subtag 'a' appears twice. Note that 618 the tag "en-a-bbb-x-a-ccc" is valid because the second 619 appearance of the singleton 'a' is in a private use sequence. 621 5. Extension subtags MUST meet all of the requirements for the 622 content and format of subtags defined in this document. 624 6. Extension subtags MUST meet whatever requirements are set by the 625 document that defines their singleton prefix and whatever 626 requirements are provided by the maintaining authority. 628 7. Each extension subtag MUST be from two to eight characters long 629 and consist solely of letters or digits, with each subtag 630 separated by a single '-'. 632 8. Each singleton MUST be followed by at least one extension 633 subtag. For example, the tag "tlh-a-b-foo" is invalid because 634 the first singleton 'a' is followed immediately by another 635 singleton 'b'. 637 9. Extension subtags MUST follow all language, extended language, 638 script, region and variant subtags in a tag. 640 10. All subtags following the singleton and before another singleton 641 are part of the extension. Example: In the tag "fr-a-Latn", the 642 subtag 'Latn' does not represent the script subtag 'Latn' 643 defined in the IANA Language Subtag Registry. Its meaning is 644 defined by the extension 'a'. 646 11. In the event that more than one extension appears in a single 647 tag, the tag SHOULD be canonicalized as described in 648 Section 4.4. 650 For example, if the prefix singleton 'r' and the shown subtags were 651 defined, then the following tag would be a valid example: "en-Latn- 652 GB-boont-r-extended-sequence-x-private" 654 2.2.7 Private Use Subtags 656 Private use subtags are used to indicate distinctions in language 657 important in a given context by private agreement. The following 658 rules apply to private-use subtags: 660 1. Private-use subtags are separated from the other subtags defined 661 in this document by the reserved single-character subtag 'x'. 663 2. Private-use subtags MUST follow all language, extended language, 664 script, region, variant, and extension subtags in the tag. 665 Another way of saying this is that all subtags following the 666 singleton 'x' MUST be considered private use. Example: The 667 subtag 'US' in the tag "en-x-US" is a private use subtag. 669 3. A tag MAY consist entirely of private-use subtags. 671 4. No source is defined for private use subtags. Use of private use 672 subtags is by private agreement only. 674 For example: Users who wished to utilize SIL Ethnologue for 675 identification might agree to exchange tags such as "az-Arab-x-AZE- 676 derbend". This example contains two private-use subtags. The first 677 is 'AZE' and the second is 'derbend'. 679 2.2.8 Pre-Existing RFC 3066 Registrations 681 Existing IANA-registered language tags from RFC 1766 and/or RFC 3066 682 maintain their validity. IANA will maintain these tags in the 683 registry under either the "grandfathered" or "redundant" type. For 684 more information see Section 3.7. 686 It is important to note that all language tags formed under the 687 guidelines in this document were either legal, well-formed tags or 688 could have been registered under RFC 3066. 690 2.2.9 Classes of Conformance 692 Implementations sometimes need to describe their capabilities with 693 regard to the rules and practices described in this document. There 694 are two classes of conforming implementations described by this 695 document: "well-formed" processors and "validating" processors. 696 Claims of conformance SHOULD explicitly reference one of these 697 definitions. 699 An implementation that claims to check for well-formed language tags 700 MUST: 702 o Check that the tag and all of its subtags, including extension and 703 private-use subtags, conform to the ABNF or that the tag is on the 704 list of grandfathered tags. 706 o Check that singleton subtags that identify extensions do not 707 repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not well- 708 formed. 710 Well-formed processors are strongly encouraged to implement the 711 canonicalization rules contained in Section 4.4. 713 An implementation that claims to be validating MUST: 715 o Check that the tag is well-formed. 717 o Specify the particular registry date for which the implementation 718 performs validation of subtags. 720 o Check that either the tag is a grandfathered tag, or that all 721 language, script, region, and variant subtags consist of valid 722 codes for use in language tags according to the IANA registry as 723 of the particular date specified by the implementation. 725 o Specify which, if any, extension RFCs as defined in Section 3.6 726 are supported, including version, revision, and date. 728 o For any such extensions supported, check that all subtags used in 729 that extension are valid. 731 o For variant and extended language subtags, if the registry 732 contains one or more 'Prefix' fields for that subtag, check that 733 the tag matches at least one prefix. The tag matches if all the 734 subtags in the 'Prefix' also appear in the tag. For example, the 735 prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both 736 the 'es' language subtag and 'CO' region subtag appear in the tag. 738 3. Registry Format and Maintenance 740 This section defines the Language Subtag Registry and the maintenance 741 and update procedures associated with it. 743 The language subtag registry will be maintained so that, except for 744 extension subtags, it is possible to validate all of the subtags that 745 appear in a language tag under the provisions of this document or its 746 revisions or successors. In addition, the meaning of the various 747 subtags will be unambiguous and stable over time. (The meaning of 748 private-use subtags, of course, is not defined by the IANA registry.) 750 The registry defined under this document contains a comprehensive 751 list of all of the subtags valid in language tags. This allows 752 implementers a straightforward and reliable way to validate language 753 tags. 755 3.1 Format of the IANA Language Subtag Registry 757 The IANA Language Subtag Registry ("the registry") will consist of a 758 text file that is machine readable in the format described in this 759 section, plus copies of the registration forms approved by the 760 Language Subtag Reviewer in accordance with the process described in 761 Section 3.4. With the exception of the registration forms for 762 grandfathered and redundant tags, no registration records will be 763 maintained for the initial set of subtags. 765 The registry will be in a modified record-jar format text file 766 [record-jar]. Lines are limited to 72 characters, including all 767 whitespace. 769 Records are separated by lines containing only the sequence "%%" 770 (%x25.25). 772 Each field can be viewed as a single, logical line of ASCII 773 characters, comprising a field-name and a field-body separated by a 774 COLON character (%x3A). For convenience, the field-body portion of 775 this conceptual entity can be split into a multiple-line 776 representation; this is called "folding". The format of the registry 777 is described by the following ABNF (per [RFC2234bis]): 779 registry = record *("%%" CRLF record) 780 record = 1*( field-name *SP ":" *SP field-body CRLF ) 781 field-name = *(ALPHA / DIGIT / "-") 782 field-body = *(ASCCHAR/LWSP) 783 ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26 784 UNICHAR = "&#x" 2*6HEXDIG ";" 785 The sequence '..' (%x2E.2E) in a field-body denotes a range of 786 values. Such a range represents all subtags of the same length that 787 are alphabetically within that range, including the values explicitly 788 mentioned. For example 'a..c' denotes the values 'a', 'b', and 'c'. 790 Characters from outside the US-ASCII repertoire, as well as the 791 AMPERSAND character ("&", %x26) when it occurs in a field-body are 792 represented by a "Numeric Character Reference" using hexadecimal 793 notation in the style used by [XML10] (see 794 ). This consists of the 795 sequence "&#x" (%x26.23.78) followed by a hexadecimal representation 796 of the character's code point in [ISO10646] followed by a closing 797 semicolon (%x3B). For example, the EURO SIGN, U+20AC, would be 798 represented by the sequence "€". Note that the hexadecimal 799 notation MAY have between two and six digits. 801 All fields whose field-body contains a date value use the "full-date" 802 format specified in [RFC3339]. For example: "2004-06-28" represents 803 June 28, 2004 in the Gregorian calendar. 805 The first record in the file contains the single field whose field- 806 name is "File-Date". The field-body of this record contains the last 807 modification date of this copy of the registry, making it possible to 808 compare different versions of the registry. The registry on the IANA 809 website is the most current. Versions with an older date than that 810 one are not up-to-date. 812 File-Date: 2004-06-28 813 %% 815 Subsequent records represent subtags in the registry. Each of the 816 fields in each record MUST occur no more than once, unless otherwise 817 noted below. Each record MUST contain the following fields: 819 o 'Type' 821 * Type's field-value MUST consist of one of the following 822 strings: "language", "extlang", "script", "region", "variant", 823 "grandfathered", and "redundant" and denotes the type of tag or 824 subtag. 826 o Either 'Subtag' or 'Tag' 828 * Subtag's field-value contains the subtag being defined. This 829 field MUST only appear in records of whose Type has one of 830 these values: "language", "extlang", "script", "region", or 831 "variant". 833 * Tag's field-value contains a complete language tag. This field 834 MUST only appear in records whose Type has one of these values: 835 "grandfathered" or "redundant". 837 o Description 839 * Description's field-value contains a non-normative description 840 of the subtag or tag. 842 o Added 844 * Added's field-value contains the date the record was added to 845 the registry. 847 The 'Subtag' or 'Tag' field MUST use lowercase letters to form the 848 subtag or tag, with two exceptions. Subtags whose 'Type' field is 849 'script' (in other words, subtags defined by ISO 15924) MUST use 850 titlecase. Subtags whose 'Type' field is 'region' (in other words, 851 subtags defined by ISO 3166) MUST use uppercase. These exceptions 852 mirror the use of case in the underlying standards. 854 The field 'Description' MAY appear more than one time. At least one 855 of the 'Description' fields MUST contain a description of the tag 856 being registered written or transcribed into the Latin script; the 857 same or additional fields MAY also include a description in a non- 858 Latin script. The 'Description' field is used for identification 859 purposes and SHOULD NOT be taken to represent the actual native name 860 of the language or variation or to be in any particular language. 861 Most descriptions are taken directly from source standards such as 862 ISO 639 or ISO 3166. 864 Note: Descriptions in registry entries that correspond to ISO 639, 865 ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate 866 the meaning of that identifier as defined in the source standard at 867 the time it was added to the registry. The description does not 868 replace the content of the source standard itself. The descriptions 869 are not intended to be the English localized names for the subtags. 870 Localization or translation of language tag and subtag descriptions 871 is out of scope of this document. 873 Each record MAY also contain the following fields: 875 o Preferred-Value 877 * For fields of type 'language', 'extlang', 'script', 'region', 878 and 'variant', 'Preferred-Value' contains a subtag of the same 879 'Type' which is preferred for forming the language tag. 881 * For fields of type 'grandfathered' and 'redundant', a canonical 882 mapping to a complete language tag. 884 o Deprecated 886 * Deprecated's field-value contains the date the record was 887 deprecated. 889 o Prefix 891 * Prefix's field-value contains a language tag with which this 892 subtag MAY be used to form a new language tag, perhaps with 893 other subtags as well. This field MUST only appear in records 894 whose 'Type' field-value is 'variant' or 'extlang'. For 895 example, the 'Prefix' for the variant 'nedis' is 'sl', meaning 896 that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate 897 while the tag "is-nedis" is not. 899 o Comments 901 * Comments contains additional information about the subtag, as 902 deemed appropriate for understanding the registry and 903 implementing language tags using the subtag or tag. 905 o Suppress-Script 907 * Suppress-Script contains a script subtag that SHOULD NOT be 908 used to form language tags with the associated primary language 909 subtag. This field MUST only appear in records whose 'Type' 910 field-value is 'language'. See Section 4.1. 912 The field 'Deprecated' MAY be added to any record via the maintenance 913 process described in Section 3.2 or via the registration process 914 described in Section 3.4. Usually the addition of a 'Deprecated' 915 field is due to the action of one of the standards bodies, such as 916 ISO 3166, withdrawing a code. In some historical cases it might not 917 have been possible to reconstruct the original deprecation date. 918 For these cases, an approximate date appears in the registry. 919 Although valid in language tags, subtags and tags with a 'Deprecated' 920 field are deprecated and validating processors SHOULD NOT generate 921 these subtags. Note that a record that contains a 'Deprecated' field 922 and no corresponding 'Preferred-Value' field has no replacement 923 mapping. 925 Thie field 'Preferred-Value' contains a mapping between the record in 926 which it appears and a tag or subtag which SHOULD be preferred when 927 selected language tags. These values form three groups: 929 ISO 639 language codes which were later withdrawn in favor of 930 other codes. These values are mostly a historical curiosity. 932 ISO 3166 region codes which have been withdrawn in favor of a new 933 code. This sometimes happens when a country changes its name or 934 administration in such a way that warrants a new region code. 936 Tags grandfathered from RFC 3066. In many cases these tags have 937 become obsolete because the values they represent were later 938 encoded by ISO 639. 940 Records that contain a 'Preferred-Value' field MUST also have a 941 'Deprecated' field. This field contains a date of deprecation. Thus 942 a language tag processor can use the registry to construct the valid, 943 non-deprecated set of subtags for a given date. In addition, for any 944 given tag, a processor can construct the set of valid language tags 945 that correspond to that tag for all dates up to the date of the 946 registry. The ability to do these mappings MAY be beneficial to 947 applications that are matching, selecting, for filtering content 948 based on its language tags. 950 Note that 'Preferred-Value' mappings in records of type 'region' MAY 951 NOT represent exactly the same meaning as the original value. There 952 are many reasons for a country code to be changed and the effect this 953 has on the formation of language tags will depend on the nature of 954 the change in question. 956 In particular, the 'Preferred-Value' field does not imply retagging 957 content that uses the affected subtag. 959 The field 'Preferred-Value' MUST NOT be modified once created in the 960 registry. The field MAY be added to records of type "grandfathered" 961 and "region" according to the rules in Section 3.2. Otherwise the 962 field MUST NOT be added to any record already in the registry. 964 The 'Preferred-Value' field in records of type "grandfathered" and 965 "redundant" contains whole language tags that are strongly 966 RECOMMENDED for use in place of the record's value. In many cases 967 the mappings were created by deprecation of the tags during the 968 period before this document was adopted. For example, the tag "no- 969 nyn" was deprecated in favor of the ISO 639-1 defined language code 970 'nn'. 972 Records of type 'variant' MAY have more than one field of type 973 'Prefix'. Additional fields of this type MAY be added to a 'variant' 974 record via the registration process. 976 Records of type 'extlang' MUST have _exactly_ one 'Prefix' field. 978 The field-value of the 'Prefix' field consists of a language tag 979 whose subtags are appropriate to use with this subtag. For example, 980 the variant subtag '1996' has a Prefix field of "de". This means 981 that tags starting with the sequence "de-" are appropriate with this 982 subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while 983 the tag "fr-1996" is an inappropriate choice. 985 The field of type 'Prefix' MUST NOT be removed from any record. The 986 field-value for this type of field MUST NOT be modified. 988 The field 'Comments' MAY appear more than once per record. This 989 field MAY be inserted or changed via the registration process and no 990 guarantee of stability is provided. The content of this field is not 991 restricted, except by the need to register the information, the 992 suitability of the request, and by reasonable practical size 993 limitations. Long screeds about a particular subtag are frowned 994 upon. 996 The field 'Suppress-Script' MUST only appear in records whose 'Type' 997 field-value is 'language'. This field MAY appear at most one time in 998 a record. This field indicates a script used to write the 999 overwhelming majority of documents for the given language and which 1000 therefore adds no distinguishing information to a language tag. It 1001 helps ensure greater compatibility between the language tags 1002 generated according to the rules in this document and language tags 1003 and tag processors or consumers based on RFC 3066. For example, 1004 virtually all Icelandic documents are written in the Latin script, 1005 making the subtag 'Latn' redundant in the tag "is-Latn". 1007 3.2 Maintenance of the Registry 1009 Maintenance of the registry requires that as codes are assigned or 1010 withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language 1011 Subtag Reviewer will evaluate each change, determine whether it 1012 conflicts with existing registry entries, and submit the information 1013 to IANA for inclusion in the registry. If an change takes place and 1014 the Language Subtag Reviewer does not do this in a timely manner, 1015 then any interested party MAY use the procedure in Section 3.4 to 1016 register the appropriate update. 1018 Note: The redundant and grandfathered entries together are the 1019 complete list of tags registered under [RFC3066]. The redundant tags 1020 are those that can now be formed using the subtags defined in the 1021 registry together with the rules of Section 2.2. The grandfathered 1022 entries are those that can never be legal under those same 1023 provisions. 1025 The set of redundant and grandfathered tags is permanent and stable: 1027 no new entries will be added and none of the entries will be removed. 1028 Records of type 'grandfathered' MAY have their type converted to 1029 'redundant': see Section 3.7 for more information. 1031 RFC 3066 tags that were deprecated prior to the adoption of this 1032 document are part of the list of grandfathered tags and their 1033 component subtags were not included as registered variants (although 1034 they remain eligible for registration). For example, the tag "art- 1035 lojban" was deprecated in favor of the language subtag 'jbo'. 1037 The Language Subtag Reviewer MUST ensure that new subtags meet the 1038 requirements in Section 4.1 or submit an appropriate alternate subtag 1039 as described in that section. When either a change or addition to 1040 the registry is needed, the Language Subtag Reviewer MUST prepare the 1041 complete record, including all fields, and forward it to IANA for 1042 insertion into the registry. 1044 If record represents a new subtag that does not currently exist in 1045 the registry, then the message's subject line MUST include the word 1046 "INSERT". If the record represents a change to an existing subtag, 1047 then the subject line of the message MUST include the word "MODIFY". 1048 The message MUST contain both the record for the subtag being 1049 inserted or modified and the new File-Date record. Here is an 1050 example of what the body of the message might contain: 1052 LANGUAGE SUBTAG MODIFICATION 1053 File-Date: 2005-01-02 1054 %% 1055 Type: variant 1056 Subtag: nedis 1057 Description: Natisone dialect 1058 Description: Nadiza dialect 1059 Added: 2003-10-09 1060 Prefix: sl 1061 Comments: This is a comment shown 1062 as an example. 1063 %% 1065 Figure 4 1067 Whenever an entry is created or modified in the registry, the 'File- 1068 Date' record at the start of the registry is updated to reflect the 1069 most recent modification date in the [RFC3339] "full-date" format. 1071 Values in the 'Subtag' field MUST be lowercase except as provided for 1072 in Section 3.1. 1074 3.3 Stability of IANA Registry Entries 1076 The stability of entries and their meaning in the registry is 1077 critical to the long term stability of language tags. The rules in 1078 this section guarantee that a specific language tag's meaning is 1079 stable over time and will not change. 1081 These rules specifically deal with how changes to codes (including 1082 withdrawal and deprecation of codes) maintained by ISO 639, ISO 1083 15924, ISO 3166, and UN M.49 are reflected in the IANA Language 1084 Subtag Registry. Assignments to the IANA Language Subtag Registry 1085 MUST follow the following stability rules: 1087 o Values in the fields 'Type', 'Subtag', 'Tag', 'Added', 1088 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are 1089 guaranteed to be stable over time. 1091 o Values in the 'Description' field MUST NOT be changed in a way 1092 that would invalidate previously-existing tags. They MAY be 1093 broadened somewhat in scope, changed to add information, or 1094 adapted to the most common modern usage. For example, countries 1095 occasionally change their official names: an historical example of 1096 this would be "Upper Volta" changing to "Burkina Faso". 1098 o Values in the field 'Prefix' MAY be added to records of type 1099 'variant' via the registration process. 1101 o Values in the field 'Prefix' MAY be modified, so long as the 1102 modifications broaden the set of prefixes. That is, a prefix MAY 1103 be replaced by one of its own prefixes. For example, the prefix 1104 "en-US" could be replaced by "en", but not by the prefixes "en- 1105 Latn", "fr", or "en-US-boont". If one of those prefixes were 1106 needed, a new Prefix SHOULD be registered. 1108 o Values in the field 'Prefix' MUST NOT be removed. 1110 o The field 'Comments' MAY be added, changed, modified, or removed 1111 via the registration process or any of the processes or 1112 considerations described in this section. 1114 o The field 'Suppress-Script' MAY be added or removed via the 1115 registration process. 1117 o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not 1118 conflict with existing subtags of the associated type and whose 1119 meaning is not the same as an existing subtag of the same type are 1120 entered into the IANA registry as new records. 1122 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are 1123 withdrawn by their respective maintenance or registration 1124 authority remain valid in language tags. A 'Deprecated' field 1125 containing the date of withdrawal is added to the record. If a 1126 new record of the same type is added that represents a replacement 1127 value, then a 'Preferred-Value' field MAY also be added. The 1128 registration process MAY be used to add comments about the 1129 withdrawal of the code by the respective standard. 1131 * The region code 'TL' was assigned to the country 'Timor-Leste', 1132 replacing the code 'TP' (which was assigned to 'East Timor' 1133 when it was under administration by Portugal). The subtag 'TP' 1134 remains valid in language tags, but its record contains the a 1135 'Preferred-Value' of 'TL' and its field 'Deprecated' contains 1136 the date the new code was assigned ('2004-07-06'). 1138 o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict 1139 with existing subtags of the associated type, including subtags 1140 that are deprecated, MUST NOT be entered into the registry. The 1141 following additional considerations apply to subtag values that 1142 are reassigned: 1144 * For ISO 639 codes, if the newly assigned code's meaning is not 1145 represented by a subtag in the IANA registry, the Language 1146 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1147 proposal for entering in the IANA registry as soon as practical 1148 a registered language subtag as an alternate value for the new 1149 code. The form of the registered language subtag will be at 1150 the discretion of the Language Subtag Reviewer and MUST conform 1151 to other restrictions on language subtags in this document. 1153 * For all subtags whose meaning is derived from an external 1154 standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if a 1155 new meaning is assigned to an existing code and the new meaning 1156 broadens the meaning of that code, then the meaning for the 1157 associated subtag MAY be changed to match. The meaning of a 1158 subtag MUST NOT be narrowed, however, as this can result in an 1159 unknown proportion of the existing uses of a subtag becoming 1160 invalid. Note: ISO 639 MA/RA has adopted a similar stability 1161 policy. 1163 * For ISO 15924 codes, if the newly assigned code's meaning is 1164 not represented by a subtag in the IANA registry, the Language 1165 Subtag Reviewer, as described in Section 3.4, SHALL prepare a 1166 proposal for entering in the IANA registry as soon as practical 1167 a registered variant subtag as an alternate value for the new 1168 code. The form of the registered variant subtag will be at the 1169 discretion of the Language Subtag Reviewer and MUST conform to 1170 other restrictions on variant subtags in this document. 1172 * For ISO 3166 codes, if the newly assigned code's meaning is 1173 associated with the same UN M.49 code as another 'region' 1174 subtag, then the existing region subtag remains as the 1175 preferred value for that region and no new entry is created. A 1176 comment MAY be added to the existing region subtag indicating 1177 the relationship to the new ISO 3166 code. 1179 * For ISO 3166 codes, if the newly assigned code's meaning is 1180 associated with a UN M.49 code that is not represented by an 1181 existing region subtag, then the Language Subtag Reviewer, as 1182 described in Section 3.4, SHALL prepare a proposal for entering 1183 the appropriate UN M.49 country code as an entry in the IANA 1184 registry. 1186 * Codes assigned by UN M.49 to countries or areas (as opposed to 1187 geographical regions and sub-regions) for which there is no 1188 corresponding ISO 3166 code MUST NOT be registered, except 1189 under the previous provision. If it is necessary to identify a 1190 region for which only a UN M.49 code exists in language tags, 1191 then the registration authority for ISO 3166 SHOULD be 1192 petitioned to assign a code, which can then be registered for 1193 use in language tags. At the time this document was written, 1194 there were only four such codes: 830 (Channel Islands), 831 1195 (Guernsey), 832 (Jersey), and 833 (Isle of Man). This rule 1196 exists so that UN M.49 codes remain available as the value of 1197 last resort in cases where ISO 3166 reassigns a deprecated 1198 value in the registry. 1200 * For ISO 3166 codes, if there is no associated UN numeric code, 1201 then the Language Subtag Reviewer SHALL petition the UN to 1202 create one. If there is no response from the UN within ninety 1203 days of the request being sent, the Language Subtag Reviewer 1204 SHALL prepare a proposal for entering in the IANA registry as 1205 soon as practical a registered variant subtag as an alternate 1206 value for the new code. The form of the registered variant 1207 subtag will be at the discretion of the Language Subtag 1208 Reviewer and MUST conform to other restrictions on variant 1209 subtags in this document. This situation is very unlikely to 1210 ever occur. 1212 o Stability provisions apply to grandfathered tags with this 1213 exception: should all of the subtags in a grandfathered tag become 1214 valid subtags in the IANA registry, then the field 'Type' in that 1215 record is changed from 'grandfathered' to 'redundant'. Note that 1216 this will not affect language tags that match the grandfathered 1217 tag, since these tags will now match valid generative subtag 1218 sequences. For example, if the subtag 'gan' in the language tag 1219 "zh-gan" were to be registered as an extended language subtag, 1220 then the grandfathered tag "zh-gan" would be deprecated (but 1221 existing content or implementations that use "zh-gan" would remain 1222 valid). 1224 3.4 Registration Procedure for Subtags 1226 The procedure given here MUST be used by anyone who wants to use a 1227 subtag not currently in the IANA Language Subtag Registry. 1229 Only subtags of type 'language' and 'variant' will be considered for 1230 independent registration of new subtags. Handling of subtags needed 1231 for stability and subtags necessary to keep the registry synchronized 1232 with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits 1233 defined by this document are described in Section 3.2. Stability 1234 provisions are described in Section 3.3. 1236 This procedure MAY also be used to register or alter the information 1237 for the "Description", "Comments", "Deprecated", or "Prefix" fields 1238 in a subtag's record as described in Section 3.3. Changes to all 1239 other fields in the IANA registry are NOT permitted. 1241 Registering a new subtag or requesting modifications to an existing 1242 tag or subtag starts with the requester filling out the registration 1243 form reproduced below. Note that each response is not limited in 1244 size so that the request can adequately describe the registration. 1245 The fields in the "Record Requested" section SHOULD follow the 1246 requirements in Section 3.1. 1248 LANGUAGE SUBTAG REGISTRATION FORM 1249 1. Name of requester: 1250 2. E-mail address of requester: 1251 3. Record Requested: 1253 Type: 1254 Subtag: 1255 Description: 1256 Prefix: 1257 Preferred-Value: 1258 Deprecated: 1259 Suppress-Script: 1260 Comments: 1262 4. Intended meaning of the subtag: 1263 5. Reference to published description 1264 of the language (book or article): 1265 6. Any other relevant information: 1267 Figure 5 1269 The subtag registration form MUST be sent to 1270 for a two week review period before it can 1271 be submitted to IANA. (This is an open list and can be joined by 1272 sending a request to .) 1274 Variant and extlang subtags are always registered for use with a 1275 particular range of language tags. For example, the subtag 'rozaj' 1276 is intended for use with language tags that start with the primary 1277 language subtag "sl", since Resian is a dialect of Slovenian. Thus 1278 the subtag 'rozaj' could be included in tags such as "sl-Latn-rozaj" 1279 or "sl-IT-rozaj". This information is stored in the "Prefix" field 1280 in the registry. Variant registration requests are REQUIRED to 1281 include at least one "Prefix" field in the registration form. 1283 The 'Prefix' field for a given registered subtag will be maintained 1284 in the IANA registry as a guide to usage. Additional prefixes MAY be 1285 added by filing an additional registration form. In that form, the 1286 "Any other relevant information:" field MUST indicate that it is the 1287 addition of a prefix. 1289 Requests to add a prefix to a variant subtag that imply a different 1290 semantic meaning will probably be rejected. For example, a request 1291 to add the prefix "de" to the subtag 'nedis' so that the tag "de- 1292 nedis" represented some German dialect would be rejected. The 1293 'nedis' subtag represents a particular Slovenian dialect and the 1294 additional registration would change the semantic meaning assigned to 1295 the subtag. A separate subtag SHOULD be proposed instead. 1297 The 'Description' field MUST contain a description of the tag being 1298 registered written or transcribed into the Latin script; it MAY also 1299 include a description in a non-Latin script. Non-ASCII characters 1300 MUST be escaped using the syntax described in Section 3.1. The 1301 'Description' field is used for identification purposes and doesn't 1302 necessarily represent the actual native name of the language or 1303 variation or to be in any particular language. 1305 While the 'Description' field itself is not guaranteed to be stable 1306 and errata corrections MAY be undertaken from time to time, attempts 1307 to provide translations or transcriptions of entries in the registry 1308 itself will probably be frowned upon by the community or rejected 1309 outright, as changes of this nature have an impact on the provisions 1310 in Section 3.3. 1312 The Language Subtag Reviewer is responsible for responding to 1313 requests for the registration of subtags through the registration 1314 process and is appointed by the IESG. 1316 When the two week period has passed the Language Subtag Reviewer 1317 either forwards the record to be inserted or modified to 1318 iana@iana.org according to the procedure described in Section 3.2, or 1319 rejects the request because of significant objections raised on the 1320 list or due to problems with constraints in this document (which MUST 1321 be explicitly cited). The reviewer MAY also extend the review period 1322 in two week increments to permit further discussion. The reviewer 1323 MUST indicate on the list whether the registration has been accepted, 1324 rejected, or extended following each two week period. 1326 Note that the reviewer can raise objections on the list if he or she 1327 so desires. The important thing is that the objection MUST be made 1328 publicly. 1330 The applicant is free to modify a rejected application with 1331 additional information and submit it again; this restarts the two 1332 week comment period. 1334 Decisions made by the reviewer MAY be appealed to the IESG [RFC2028] 1335 under the same rules as other IETF decisions [RFC2026]. 1337 All approved registration forms are available online in the directory 1338 http://www.iana.org/numbers.html under "languages". 1340 Updates or changes to existing records follow the same procedure as 1341 new registrations. The Language Subtag Reviewer decides whether 1342 there is consensus to update the registration following the two week 1343 review period; normally objections by the original registrant will 1344 carry extra weight in forming such a consensus. 1346 Registrations are permanent and stable. Once registered, subtags 1347 will not be removed from the registry and will remain a valid way in 1348 which to specify a specific language or variant. 1350 Note: The purpose of the "Description" in the registration form is 1351 intended as an aid to people trying to verify whether a language is 1352 registered or what language or language variation a particular subtag 1353 refers to. In most cases, reference to an authoritative grammar or 1354 dictionary of that language will be useful; in cases where no such 1355 work exists, other well known works describing that language or in 1356 that language MAY be appropriate. The subtag reviewer decides what 1357 constitutes "good enough" reference material. This requirement is 1358 not intended to exclude particular languages or dialects due to the 1359 size of the speaker population or lack of a standardized orthography. 1360 Minority languages will be considered equally on their own merits. 1362 3.5 Possibilities for Registration 1364 Possibilities for registration of subtags or information about 1365 subtags include: 1367 o Primary language subtags for languages not listed in ISO 639 that 1368 are not variants of any listed or registered language can be 1369 registered. At the time this document was created there were no 1370 examples of this form of subtag. Before attempting to register a 1371 language subtag, there MUST be an attempt to register the language 1372 with ISO 639. No language subtags will be registered for codes 1373 that exist in ISO 639-1 or ISO 639-2, which are under 1374 consideration by the ISO 639 maintenance or registration 1375 authorities, or which have never been attempted for registration 1376 with those authorities. If ISO 639 has previously rejected a 1377 language for registration, it is reasonable to assume that there 1378 must be additional very compelling evidence of need before it will 1379 be registered in the IANA registry (to the extent that it is very 1380 unlikely that any subtags will be registered of this type). 1382 o Dialect or other divisions or variations within a language, its 1383 orthography, writing system, regional or historical usage, 1384 transliteration or other transformation, or distinguishing 1385 variation MAY be registered as variant subtags. An example is the 1386 'rozaj' subtag (the Resian dialect of Slovenian). 1388 o The addition or maintenance of fields (generally of an 1389 informational nature) in Tag or Subtag records as described in 1390 Section 3.1 and subject to the stability provisions in 1391 Section 3.3. This includes descriptions; comments; deprecation 1392 and preferred values for obsolete or withdrawn codes; or the 1393 addition of script or extlang information to primary language 1394 subtags. 1396 o The addition of records and related field value changes necessary 1397 to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and 1398 UN M.49 as described in Section 3.3. 1400 This document leaves the decision on what subtags or changes to 1401 subtags are appropriate (or not) to the registration process 1402 described in Section 3.4. 1404 Note: four character primary language subtags are reserved to allow 1405 for the possibility of alpha4 codes in some future addition to the 1406 ISO 639 family of standards. 1408 ISO 639 defines a maintenance agency for additions to and changes in 1409 the list of languages in ISO 639. This agency is: 1411 International Information Centre for Terminology (Infoterm) 1412 Aichholzgasse 6/12, AT-1120 1413 Wien, Austria 1414 Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72 1416 ISO 639-2 defines a maintenance agency for additions to and changes 1417 in the list of languages in ISO 639-2. This agency is: 1419 Library of Congress 1420 Network Development and MARC Standards Office 1421 Washington, D.C. 20540 USA 1422 Phone: +1 202 707 6237 Fax: +1 202 707 0115 1423 URL: http://www.loc.gov/standards/iso639 1425 The maintenance agency for ISO 3166 (country codes) is: 1427 ISO 3166 Maintenance Agency 1428 c/o International Organization for Standardization 1429 Case postale 56 1430 CH-1211 Geneva 20 Switzerland 1431 Phone: +41 22 749 72 33 Fax: +41 22 749 73 49 1432 URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html 1434 The registration authority for ISO 15924 (script codes) is: 1436 Unicode Consortium Box 391476 1437 Mountain View, CA 94039-1476, USA 1438 URL: http://www.unicode.org/iso15924 1440 The Statistics Division of the United Nations Secretariat maintains 1441 the Standard Country or Area Codes for Statistical Use and can be 1442 reached at: 1444 Statistical Services Branch 1445 Statistics Division 1446 United Nations, Room DC2-1620 1447 New York, NY 10017, USA 1449 Fax: +1-212-963-0623 1450 E-mail: statistics@un.org 1451 URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm 1453 3.6 Extensions and Extensions Namespace 1455 Extension subtags are those introduced by single-letter subtags other 1456 than 'x'. They are reserved for the generation of identifiers which 1457 contain a language component, and are compatible with applications 1458 that understand language tags. For example, they might be used to 1459 define locale identifiers, which are generally based on language. 1461 The structure and form of extensions are defined by this document so 1462 that implementations can be created that are forward compatible with 1463 applications that might be created using single-letter subtags in the 1464 future. In addition, defining a mechanism for maintaining single- 1465 letter subtags will lend to the stability of this document by 1466 reducing the likely need for future revisions or updates. 1468 Allocation of a single-letter subtag SHALL take the form of an RFC 1469 defining the name, purpose, processes, and procedures for maintaining 1470 the subtags. The maintaining or registering authority, including 1471 name, contact email, discussion list email, and URL location of the 1472 registry MUST be indicated clearly in the RFC. The RFC MUST specify 1473 or include each of the following: 1475 o The specification MUST reference the specific version or revision 1476 of this document that governs its creation and MUST reference this 1477 section of this document. 1479 o The specification and all subtags defined by the specification 1480 MUST follow the ABNF and other rules for the formation of tags and 1481 subtags as defined in this document. In particular it MUST 1482 specify that case is not significant and that subtags MUST NOT 1483 exceed eight characters in length. 1485 o The specification MUST specify a canonical representation. 1487 o The specification of valid subtags MUST be available over the 1488 Internet and at no cost. 1490 o The specification MUST be in the public domain or available via a 1491 royalty-free license acceptable to the IETF and specified in the 1492 RFC. 1494 o The specification MUST be versioned and each version of the 1495 specification MUST be numbered, dated, and stable. 1497 o The specification MUST be stable. That is, extension subtags, 1498 once defined by a specification, MUST NOT be retracted or change 1499 in meaning in any substantial way. 1501 o The specification MUST include in a separate section the 1502 registration form reproduced in this section (below) to be used in 1503 registering the extension upon publication as an RFC. 1505 o IANA MUST be informed of changes to the contact information and 1506 URL for the specification. 1508 IANA will maintain a registry of allocated single-letter (singleton) 1509 subtags. This registry will use the record-jar format described by 1510 the ABNF in Section 3.1. Upon publication of an extension as an RFC, 1511 the maintaining authority defined in the RFC MUST forward this 1512 registration form to iesg@ietf.org, who will forward the request to 1513 iana@iana.org. The maintaining authority of the extension MUST 1514 maintain the accuracy of the record by sending an updated full copy 1515 of the record to iana@iana.org with the subject line "LANGUAGE TAG 1516 EXTENSION UPDATE" whenever content changes. Only the 'Comments', 1517 'Contact_Email', 'Mailing_List', and 'URL' fields MAY be modified in 1518 these updates. 1520 Failure to maintain this record, the corresponding registry, or meet 1521 other conditions imposed by this section of this document MAY be 1522 appealed to the IESG [RFC2028] under the same rules as other IETF 1523 decisions (see [RFC2026]) and MAY result in the authority to maintain 1524 the extension being withdrawn or reassigned by the IESG. 1526 %% 1527 Identifier: 1528 Description: 1529 Comments: 1530 Added: 1531 RFC: 1532 Authority: 1533 Contact_Email: 1534 Mailing_List: 1535 URL: 1536 %% 1538 Figure 6: Format of Records in the Language Tag Extensions Registry 1540 'Identifier' contains the single letter subtag (singleton) assigned 1541 to the extension. The Internet-Draft submitted to define the 1542 extension SHOULD specify which letter to use, although the IESG MAY 1543 change the assignment when approving the RFC. 1545 'Description' contains the name and description of the extension. 1547 'Comments' is an OPTIONAL field and MAY contain a broader description 1548 of the extension. 1550 'Added' contains the date the RFC was published in the "full-date" 1551 format specified in [RFC3339]. For example: 2004-06-28 represents 1552 June 28, 2004, in the Gregorian calendar. 1554 'RFC' contains the RFC number assigned to the extension. 1556 'Authority' contains the name of the maintaining authority for the 1557 extension. 1559 'Contact_Email' contains the email address used to contact the 1560 maintaining authority. 1562 'Mailing_List' contains the URL or subscription email address of the 1563 mailing list used by the maintaining authority. 1565 'URL' contains the URL of the registry for this extension. 1567 The determination of whether an Internet-Draft meets the above 1568 conditions and the decision to grant or withhold such authority rests 1569 solely with the IESG, and is subject to the normal review and appeals 1570 process associated with the RFC process. 1572 Extension authors are strongly cautioned that many (including most 1573 well-formed) processors will be unaware of any special relationships 1574 or meaning inherent in the order of extension subtags. Extension 1575 authors SHOULD avoid subtag relationships or canonicalization 1576 mechanisms that interfere with matching or with length restrictions 1577 that sometimes exist in common protocols where the extension is used. 1578 In particular, applications MAY truncate the subtags in doing 1579 matching or in fitting into limited lengths, so it is RECOMMENDED 1580 that the most significant information be in the most significant 1581 (left-most) subtags, and that the specification gracefully handle 1582 truncated subtags. 1584 When a language tag is to be used in a specific, known, protocol, it 1585 is RECOMMENDED that that the language tag not contain extensions not 1586 supported by that protocol. In addition, note that some protocols 1587 MAY impose upper limits on the length of the strings used to store or 1588 transport the language tag. 1590 3.7 Initialization of the Registry 1592 Adoption of this document will REQUIRE an initial version of the 1593 registry containing the various subtags initially valid in a language 1594 tag. This collection of subtags, along with a description of the 1595 process used to create it, is described by [initial-registry]. 1597 Registrations that are in process under the rules defined in 1598 [RFC3066] when this document is adopted MAY be completed under the 1599 former rules, at the discretion of the language tag reviewer. Any 1600 new registrations submitted after the adoption of this document MUST 1601 be rejected. 1603 4. Formation and Processing of Language Tags 1605 This section addresses how to use the information in the registry 1606 with the tag syntax to choose, form and process language tags. 1608 4.1 Choice of Language Tag 1610 One is sometimes faced with the choice between several possible tags 1611 for the same body of text. 1613 Interoperability is best served when all users use the same language 1614 tag in order to represent the same language. If an application has 1615 requirements that make the rules here inapplicable, then that 1616 application risks damaging interoperability. It is strongly 1617 RECOMMENDED that users not define their own rules for language tag 1618 choice. 1620 Subtags SHOULD only be used where they add useful distinguishing 1621 information; extraneous subtags interfere with the meaning, 1622 understanding, and processing of language tags. In particular, users 1623 and implementations SHOULD follow the 'Prefix' and 'Suppress-Script' 1624 fields in the registry (defined in Section 3.1): these fields provide 1625 guidance on when specific additional subtags SHOULD (and SHOULD NOT) 1626 be used in a language tag. 1628 Of particular note, many applications can benefit from the use of 1629 script subtags in language tags, as long as the use is consistent for 1630 a given context. Script subtags were not formally defined in RFC 1631 3066 and their use can affect matching and subtag identification by 1632 implementations of RFC 3066, as these subtags appear between the 1633 primary language and region subtags. For example, if a user requests 1634 content in an implementation of Section 2.5 of [RFC3066] using the 1635 language range "en-US", content labeled "en-Latn-US" will not match 1636 the request. Therefore it is important to know when script subtags 1637 will customarily be used and when they ought not be used. In the 1638 registry, the Suppress-Script field helps ensure greater 1639 compatibility between the language tags generated according to the 1640 rules in this document and language tags and tag processors or 1641 consumers based on RFC 3066 by defining when users SHOULD NOT include 1642 a script subtag with a particular primary language subtag. 1644 Extended language subtags (type 'extlang' in the registry, see 1645 Section 3.1) also appear between the primary language and region 1646 subtags and are reserved for future standardization. Applications 1647 might benefit from their judicious use in forming language tags in 1648 the future. Similar recommendations are expected to apply to their 1649 use as apply to script subtags. 1651 Standards, protocols and applications that reference this document 1652 normatively but apply different rules to the ones given in this 1653 section MUST specify how the procedure varies from the one given 1654 here. 1656 The choice of subtags used to form a language tag SHOULD be guided by 1657 the following rules: 1659 1. Use as precise a tag as possible, but no more specific than is 1660 justified. Avoid using subtags that are not important for 1661 distinguishing content in an application. 1663 * For example, 'de' might suffice for tagging an email written 1664 in German, while "de-CH-1996" is probably unnecessarily 1665 precise for such a task. 1667 2. The script subtag SHOULD NOT be used to form language tags unless 1668 the script adds some distinguishing information to the tag. The 1669 field 'Suppress-Script' in the primary language record in the 1670 registry indicates which script subtags do not add distinguishing 1671 information for most applications. 1673 * For example, the subtag 'Latn' should not be used with the 1674 primary language 'en' because nearly all English documents are 1675 written in the Latin script and it adds no distinguishing 1676 information. However, if a document were written in English 1677 mixing Latin script with another script such as Braille 1678 ('Brai'), then it might be appropriate to choose to indicate 1679 both scripts to aid in content selection, such as the 1680 application of a stylesheet. 1682 3. If a tag or subtag has a 'Preferred-Value' field in its registry 1683 entry, then the value of that field SHOULD be used to form the 1684 language tag in preference to the tag or subtag in which the 1685 preferred value appears. 1687 * For example, use 'he' for Hebrew in preference to 'iw'. 1689 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 1690 used to label content, even if the language is unknown. Omitting 1691 the language tag altogether is preferred to using a tag with a 1692 primary language subtag of 'und'. The 'und' subtag MAY be useful 1693 for protocols that require a language tag to be provided. The 1694 'und' subtag MAY also be useful when matching language tags in 1695 certain situations. 1697 5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used 1698 whenever the protocol allows the separate tags for multiple 1699 languages, as is the case for the Content-Language header in 1700 HTTP. The 'mul' subtag conveys little useful information: 1701 content in multiple languages SHOULD individually tag the 1702 languages where they appear or otherwise indicate the actual 1703 language in preference to the 'mul' subtag. 1705 6. The same variant subtag SHOULD NOT be used more than once within 1706 a language tag. 1708 * For example, do not use "de-DE-1901-1901". 1710 To ensure consistent backward compatibility, this document contains 1711 several provisions to account for potential instability in the 1712 standards used to define the subtags that make up language tags. 1713 These provisions mean that no language tag created under the rules in 1714 this document will become obsolete. 1716 4.2 Meaning of the Language Tag 1718 The relationship between the tag and the information it relates to is 1719 defined by the the context in which the tag appears. Accordingly, 1720 this section can only give possible examples of its usage. 1722 o For a single information object, the associated language tags 1723 might be interpreted as the set of languages that is necessary for 1724 a complete comprehension of the complete object. Example: Plain 1725 text documents. 1727 o For an aggregation of information objects, the associated language 1728 tags could be taken as the set of languages used inside components 1729 of that aggregation. Examples: Document stores and libraries. 1731 o For information objects whose purpose is to provide alternatives, 1732 the associated language tags could be regarded as a hint that the 1733 content is provided in several languages, and that one has to 1734 inspect each of the alternatives in order to find its language or 1735 languages. In this case, the presence of multiple tags might not 1736 mean that one needs to be multi-lingual to get complete 1737 understanding of the document. Example: MIME multipart/ 1738 alternative. 1740 o In markup languages, such as HTML and XML, language information 1741 can be added to each part of the document identified by the markup 1742 structure (including the whole document itself). For example, one 1743 could write C'est la vie. inside a 1744 Norwegian document; the Norwegian-speaking user could then access 1745 a French-Norwegian dictionary to find out what the marked section 1746 meant. If the user were listening to that document through a 1747 speech synthesis interface, this formation could be used to signal 1748 the synthesizer to appropriately apply French text-to-speech 1749 pronunciation rules to that span of text, instead of applying the 1750 inappropriate Norwegian rules. 1752 Language tags are related when they contain a similar sequence of 1753 subtags. For example, if a language tag B contains language tag A as 1754 a prefix, then B is typically "narrower" or "more specific" than A. 1755 Thus "zh-Hant-TW" is more specific than "zh-Hant". 1757 This relationship is not guaranteed in all cases: specifically, 1758 languages that begin with the same sequence of subtags are NOT 1759 guaranteed to be mutually intelligible, although they might be. For 1760 example, the tag "az" shares a prefix with both "az-Latn" 1761 (Azerbaijani written using the Latin script) and "az-Cyrl" 1762 (Azerbaijani written using the Cyrillic script). A person fluent in 1763 one script might not be able to read the other, even though the text 1764 might be identical. Content tagged as "az" most probably is written 1765 in just one script and thus might not be intelligible to a reader 1766 familiar with the other script. 1768 4.3 Length Considerations 1770 [RFC3066] did not provide an upper limit on the size of language 1771 tags. While RFC 3066 did define the semantics of particular subtags 1772 in such a way that most language tags consisted of language and 1773 region subtags with a combined total length of up to six characters, 1774 larger registered tags were not only possible but were actually 1775 registered. 1777 Neither the language tag syntax nor other requirements in this 1778 document impose a fixed upper limit on the number of subtags in a 1779 language tag (and thus an upper bound on the size of a tag). The 1780 language tag syntax suggests that, depending on the specific 1781 language, more subtags (and thus a longer tag) are sometimes 1782 necessary to completely identify the language for certain 1783 applications; thus it is possible to envision long or complex subtag 1784 sequences. 1786 4.3.1 Working with Limited Buffer Sizes 1788 Some applications and protocols are forced to allocate fixed buffer 1789 sizes or otherwise limit the length of a language tag. A conformant 1790 implementation or specification MAY refuse to support the storage of 1791 language tags which exceed a specified length. Any such limitation 1792 SHOULD be clearly documented, and such documentation SHOULD include 1793 what happens to longer tags (for example, whether an error value is 1794 generated or the language tag is truncated). A protocol that allows 1795 tags to be truncated at an arbitrary limit, without giving any 1796 indication of what that limit is, has the potential for causing harm 1797 by changing the meaning of tags in substantial ways. 1799 In practice, most language tags do not require more than a few 1800 subtags and will not approach reasonably sized buffer limitations: 1801 see Section 4.1. 1803 Some specifications or protocols have limits on tag length but do not 1804 have a fixed length limitation. For example, [RFC2231] has no 1805 explicit length limitation: the length available for the language tag 1806 is constrained by the length of other header components (such as the 1807 charset's name) coupled with the 76 character limit in [RFC2047]. 1808 Thus the "limit" might be 50 or more characters, but it could 1809 potentially be quite small. 1811 The considerations for assigning a buffer limit are: 1813 Implementations SHOULD NOT truncate language tags unless the 1814 meaning of the tag is purposefully being changed, or unless the 1815 tag does not fit into a limited buffer size specified by a 1816 protocol for storage or transmission. 1818 Implementations SHOULD warn the user when a tag is truncated since 1819 truncation changes the semantic meaning of the tag. 1821 Implementations of protocols or specifications that are space 1822 constrained but do not have a fixed limit SHOULD use the longest 1823 possible tag in preference to truncation. 1825 Protocols or specifications that specify limited buffer sizes for 1826 language tags MUST allow for language tags of up to 33 characters. 1828 Protocols or specifications that specify limited buffer sizes for 1829 language tags SHOULD allow for language tags of at least 42 1830 characters. 1832 The following illustration shows how the 42-character recommendation 1833 was derived. The combination of language and extended language 1834 subtags was chosen for future compatibility. At up to 15 characters, 1835 this combination is longer than the longest possible primary language 1836 subtag (8 characters): 1838 language = 3 (ISO 639-2; ISO 639-1 requires 2) 1839 extlang1 = 4 (each subsequent subtag includes '-') 1840 extlang2 = 4 (unlikely: needs prefix="language-extlang1") 1841 extlang3 = 4 (extremely unlikely) 1842 script = 5 (if not suppressed: see Section 4.1) 1843 region = 4 (UN M.49; ISO 3166 requires 3) 1844 variant1 = 9 (MUST have language as a prefix) 1845 variant2 = 9 (MUST have language-variant1 as a prefix) 1847 total = 42 characters 1849 Figure 7: Derivation of the Limit on Tag Length 1851 4.3.2 Truncation of Language Tags 1853 Truncation of a language tag alters the meaning of the tag, and thus 1854 SHOULD be avoided. However, truncation of language tags is sometimes 1855 necessary due to limited buffer sizes. Such truncation MUST NOT 1856 permit a subtag to be chopped off in the middle or the formation of 1857 invalid tags (for example, one ending with the "-" character). 1859 This means that applications or protocols which truncate tags MUST do 1860 so by progressively removing subtags along with their preceding "-" 1861 from the right side of the language tag until the tag is short enough 1862 for the given buffer. If the resulting tag ends with a single- 1863 character subtag, that subtag and its preceding "-" MUST also be 1864 removed. For example: 1866 Tag to truncate: zh-Hant-CN-variant1-a-extend1-x-wadegile-private1 1867 1. zh-Latn-CN-variant1-a-extend1-x-wadegile 1868 2. zh-Latn-CN-variant1-a-extend1 1869 3. zh-Latn-CN-variant1 1870 4. zh-Latn-CN 1871 5. zh-Latn 1872 6. zh 1874 Figure 8: Example of Tag Truncation 1876 4.4 Canonicalization of Language Tags 1878 Since a particular language tag is sometimes used by many processes, 1879 language tags SHOULD always be created or generated in a canonical 1880 form. 1882 A language tag is in canonical form when: 1884 1. The tag is well-formed according the rules in Section 2.1 and 1885 Section 2.2. 1887 2. Subtags of type 'Region' that have a Preferred-Value mapping in 1888 the IANA registry (see Section 3.1) SHOULD be replaced with their 1889 mapped value. 1891 3. Redundant or grandfathered tags that have a Preferred-Value 1892 mapping in the IANA registry (see Section 3.1) MUST be replaced 1893 with their mapped value. These items are either deprecated 1894 mappings created before the adoption of this document (such as 1895 the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are 1896 the result of later registrations or additions to this document 1897 (for example, "zh-guoyu" might be mapped to a language-extlang 1898 combination such as "zh-cmn" by some future update of this 1899 document). 1901 4. Other subtags that have a Preferred-Value mapping in the IANA 1902 registry (see Section 3.1) MUST be replaced with their mapped 1903 value. These items consist entirely of clerical corrections to 1904 ISO 639-1 in which the deprecated subtags have been maintained 1905 for compatibility purposes. 1907 5. If more than one extension subtag sequence exists, the extension 1908 sequences are ordered into case-insensitive ASCII order by 1909 singleton subtag. 1911 Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical 1912 form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in 1913 canonical form. 1915 Example: The language tag "en-NH" (English as used in the New 1916 Hebrides) is not canonical because the 'NH' subtag has a canonical 1917 mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its 1918 validity. 1920 Canonicalization of language tags does not imply anything about the 1921 use of upper or lowercase letters when processing or comparing 1922 subtags (and as described in Section 2.1). All comparisons MUST be 1923 performed in a case-insensitive manner. 1925 When performing canonicalization of language tags, processors MAY 1926 regularize the case of the subtags (that is, this process is 1927 OPTIONAL), following the case used in the registry. Note that this 1928 corresponds to the following casing rules: uppercase all non-initial 1929 two-letter subtags; titlecase all non-initial four-letter subtags; 1930 lowercase everything else. 1932 Note: Case folding of ASCII letters in certain locales, unless 1933 carefully handled, sometimes produces non-ASCII character values. 1934 The Unicode Character Database file "SpecialCasing.txt" defines the 1935 specific cases that are known to cause problems with this. In 1936 particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is 1937 uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). 1938 Implementers SHOULD specify a locale-neutral casing operation to 1939 ensure that case folding of subtags does not produce this value, 1940 which is illegal in language tags. For example, if one were to 1941 uppercase the region subtag 'in' using Turkish locale rules, the 1942 sequence U+0130 U+004E would result instead of the expected 'IN'. 1944 Note: if the field 'Deprecated' appears in a registry record without 1945 an accompanying 'Preferred-Value' field, then that tag or subtag is 1946 deprecated without a replacement. Validating processors SHOULD NOT 1947 generate tags that include these values, although the values are 1948 canonical when they appear in a language tag. 1950 An extension MUST define any relationships that exist between the 1951 various subtags in the extension and thus MAY define an alternate 1952 canonicalization scheme for the extension's subtags. Extensions MAY 1953 define how the order of the extension's subtags are interpreted. For 1954 example, an extension could define that its subtags are in canonical 1955 order when the subtags are placed into ASCII order: that is, "en-a- 1956 aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might 1957 define that the order of the subtags influences their semantic 1958 meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b- 1959 aaa-bbb-ccc"). However, extension specifications SHOULD be designed 1960 so that they are tolerant of the typical processes described in 1961 Section 3.6. 1963 4.5 Considerations for Private Use Subtags 1965 Private-use subtags require private agreement between the parties 1966 that intend to use or exchange language tags that use them and great 1967 caution SHOULD be used in employing them in content or protocols 1968 intended for general use. Private-use subtags are simply useless for 1969 information exchange without prior arrangement. 1971 The value and semantic meaning of private-use tags and of the subtags 1972 used within such a language tag are not defined by this document. 1974 The use of subtags defined in the IANA registry as having a specific 1975 private use meaning convey more information that a purely private use 1976 tag prefixed by the singleton subtag 'x'. For applications this 1977 additional information MAY be useful. 1979 For example, the region subtags 'AA', 'ZZ' and in the ranges 1980 'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) MAY 1981 be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a 1982 great deal of public, interchangeable information about the language 1983 material (that it is Chinese in the simplified Chinese script and is 1984 suitable for some geographic region 'XQ'). While the precise 1985 geographic region is not known outside of private agreement, the tag 1986 conveys far more information than an opaque tag such as "x-someLang", 1987 which contains no information about the language subtag or script 1988 subtag outside of the private agreement. 1990 However, in some cases content tagged with private use subtags MAY 1991 interact with other systems in a different and possibly unsuitable 1992 manner compared to tags that use opaque, privately defined subtags, 1993 so the choice of the best approach sometimes depends on the 1994 particular domain in question. 1996 5. IANA Considerations 1998 This section deals with the processes and requirements necessary for 1999 IANA to undertake to maintain the subtag and extension registries as 2000 defined by this document and in accordance with the requirements of 2001 [RFC2434]. 2003 The impact on the IANA maintainers of the two registries defined by 2004 this document will be a small increase in the frequency of new 2005 entries or updates. 2007 5.1 Language Subtag Registry 2009 Upon adoption of this document, the registry will be initialized by a 2010 companion document: [initial-registry]. The criteria and process for 2011 selecting the initial set of records is described in that document. 2012 The initial set of records represents no impact on IANA, since the 2013 work to create it will be performed externally. 2015 The new registry MUST be listed under "Language Tags" at 2016 , replacing the existing 2017 registrations defined by [RFC3066]. The existing set of registration 2018 forms and RFC 3066 registrations will be relabeled as "Language Tags 2019 (Obsolete)" and maintained (but not added to or modified). 2021 Future work on the Language Subtag Registry will be limited to 2022 inserting or replacing whole records preformatted for IANA by the 2023 Language Subtag Reviewer as described in Section 3.2 of this 2024 document. This simplifies IANA's work by limiting it to placing the 2025 text in the appropriate location in the registry. 2027 Each record will be sent to iana@iana.org with a subject line 2028 indicating whether the enclosed record is an insertion of a new 2029 record (indicated by the word "INSERT" in the subject line) or a 2030 replacement of an existing record (indicated by the word "MODIFY" in 2031 the subject line). Records MUST NOT be deleted from the registry. 2032 IANA MUST place any inserted or modified records into the appropriate 2033 section of the language subtag registry, grouping the records by 2034 their "Type" field. Inserted records MAY be placed anywhere in the 2035 appropriate section; there is no guarantee of the order of the 2036 records beyond grouping them together by 'Type'. Modified records 2037 MUST overwrite the record they replace. 2039 Included in any request to insert or modify records MUST be a new 2040 File-Date record. This record MUST be placed first in the registry. 2041 In the event that the File-Date record present in the registry has a 2042 later date then the record being inserted or modified, the existing 2043 record MUST be preserved. 2045 5.2 Extensions Registry 2047 The Language Tag Extensions registry will also be generated and sent 2048 to IANA as described in Section 3.6. This registry can contain at 2049 most 35 records and thus changes to this registry are expected to be 2050 very infrequent. 2052 Future work by IANA on the Language Tag Extensions Registry is 2053 limited to two cases. First, the IESG MAY request that new records 2054 be inserted into this registry from time to time. These requests 2055 will include the record to insert in the exact format described in 2056 Section 3.6. In addition, there MAY be occasional requests from the 2057 maintaining authority for a specific extension to update the contact 2058 information or URLs in the record. These requests MUST include the 2059 complete, updated record. IANA is not responsible for validating the 2060 information provided, only that it is properly formatted. It should 2061 reasonably be seen to come from the maintaining authority named in 2062 the record present in the registry. 2064 6. Security Considerations 2066 Language tags used in content negotiation, like any other information 2067 exchanged on the Internet, might be a source of concern because they 2068 might be used to infer the nationality of the sender, and thus 2069 identify potential targets for surveillance. 2071 This is a special case of the general problem that anything sent is 2072 visible to the receiving party and possibly to third parties as well. 2073 It is useful to be aware that such concerns can exist in some cases. 2075 The evaluation of the exact magnitude of the threat, and any possible 2076 countermeasures, is left to each application protocol (see BCP 72 2077 [RFC3552] for best current practice guidance on security threats and 2078 defenses). 2080 The language tag associated with a particular information item is of 2081 no consequence whatsoever in determining whether that content might 2082 contain possible homographs. The fact that a text is tagged as being 2083 in one language or using a particular script subtag provides no 2084 assurance whatsoever that it does not contain characters from scripts 2085 other than the one(s) associated with or specified by that language 2086 tag. 2088 Since there is no limit to the number of variant, private use, and 2089 extension subtags, and consequently no limit on the possible length 2090 of a tag, implementations need to guard against buffer overflow 2091 attacks. See Section 4.3 for details on language tag truncation, 2092 which can occur as a consequence of defenses against buffer overflow. 2094 Although the specification of valid subtags for an extension (see: 2095 Section 3.6) MUST be available over the Internet, implementations 2096 SHOULD NOT mechanically depend on it being always accessible, to 2097 prevent denial-of-service attacks. 2099 7. Character Set Considerations 2101 The syntax in this document requires that language tags use only the 2102 characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most 2103 character sets, so the composition of language tags should not have 2104 any character set issues. 2106 Rendering of characters based on the content of a language tag is not 2107 addressed in this memo. Historically, some languages have relied on 2108 the use of specific character sets or other information in order to 2109 infer how a specific character should be rendered (notably this 2110 applies to language and culture specific variations of Han ideographs 2111 as used in Japanese, Chinese, and Korean). When language tags are 2112 applied to spans of text, rendering engines can use that information 2113 in deciding which font to use in the absence of other information, 2114 particularly where languages with distinct writing traditions use the 2115 same characters. 2117 8. Changes from RFC 3066 2119 The main goals for this revision of language tags were the following: 2121 *Compatibility.* All valid RFC 3066 language tags (including those 2122 in the IANA registry) remain valid in this specification. Thus 2123 there is complete backward compatibility of this specification with 2124 existing content. In addition, this document defines language tags 2125 in such as way as to ensure future compatibility, and processors 2126 based solely on the RFC 3066 ABNF (such as those described in 2127 [XMLSchema]) will be able to process tags described by this document. 2129 *Stability.* Because of the changes in underlying ISO standards, a 2130 valid RFC 3066 language tag may become invalid (or have its meaning 2131 change) at a later date. With so much of the world's computing 2132 infrastructure dependent on language tags, this is simply 2133 unacceptable: it invalidates content that may have an extensive 2134 shelf-life. In this specification, once a language tag is valid, it 2135 remains valid forever. Previously, there was no way to determine 2136 when two tags were equivalent. This specification provides a stable 2137 mechanism for doing so, through the use of canonical forms. These 2138 are also stable, so that implementations can depend on the use of 2139 canonical forms to assess equivalency. 2141 *Validity.* The structure of language tags defined by this document 2142 makes it possible to determine if a particular tag is well-formed 2143 without regard for the actual content or "meaning" of the tag as a 2144 whole. This is important because the registry and underlying 2145 standards change over time. In addition, it must be possible to 2146 determine if a tag is valid (or not) for a given point in time in 2147 order to provide reproducible, testable results. This process must 2148 not be error-prone; otherwise even intelligent people will generate 2149 implementations that give different results. This specification 2150 provides for that by having a single data file, with specific 2151 versioning information, so that the validity of language tags at any 2152 point in time can be precisely determined (instead of interpolating 2153 values from many separate sources). 2155 *Extensibility.* It is important to be able to differentiate between 2156 written forms of language -- for many implementations this is more 2157 important than distinguishing between spoken variants of a language. 2158 Languages are written in a wide variety of different scripts, so this 2159 document provides for the generative use of ISO 15924 script codes. 2160 Like the generative use of ISO language and country codes in RFC 2161 3066, this allows combinations to be produced without resorting to 2162 the registration process. The addition of UN codes provides for the 2163 generation of language tags with regional scope, which is also 2164 required for information technology. 2166 The recast of the registry from containing whole language tags to 2167 subtags is a key part of this. An important feature of RFC 3066 was 2168 that it allowed generative use of subtags. This allows people to 2169 meaningfully use generated tags, without the delays in registering 2170 whole tags, and the burden on the registry of having to supply all of 2171 the combinations that people may find useful. 2173 Because of the widespread use of language tags, it is potentially 2174 disruptive to have periodic revisions of the core specification, 2175 despite demonstrated need. The extension mechanism provides for a 2176 way for independent RFCs to define extensions to language tags. 2177 These extensions have a very constrained, well-defined structure to 2178 prevent extensions from interfering with implementations of language 2179 tags defined in this document. The document also anticipates 2180 features of ISO 639-3 with the addition of the extended language 2181 subtags, as well as the possibility of other ISO 639 parts becoming 2182 useful for the formation of language tags in the future. The use and 2183 definition of private use tags has also been modified, to allow 2184 people to move as much information as possible out of private use 2185 tags, and into the regular structure. The goal is to dramatically 2186 reduce the need to produce a revision of this document in the future. 2188 The specific changes in this document to meet these goals are: 2190 o Defines the ABNF and rules for subtags so that the category of all 2191 subtags can be determined without reference to the registry. 2193 o Adds the concept of well-formed vs. validating processors, 2194 defining the rules by which an implementation can claim to be one 2195 or the other. 2197 o Replaces the IANA language tag registry with a language subtag 2198 registry that provides a complete list of valid subtags in the 2199 IANA registry. This allows for robust implementation and ease of 2200 maintenance. The language subtag registry becomes the canonical 2201 source for forming language tags. 2203 o Provides a process that guarantees stability of language tags, by 2204 handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in 2205 the event that they register a previously used value for a new 2206 purpose. 2208 o Allows ISO 15924 script code subtags and allows them to be used 2209 generatively. Defines a method for indicating in the registry 2210 when script subtags are necessary for a given language tag. 2212 o Adds the concept of a variant subtag and allows variants to be 2213 used generatively. 2215 o Adds the ability to use a class of UN M.49 tags for supra- 2216 national regions and to resolve conflicts in the assignment of ISO 2217 3166 codes. 2219 o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166 2220 as the mechanism for creating private-use language, script, and 2221 region subtags respectively. 2223 o Adds a well-defined extension mechanism. 2225 o Defines an extended language subtag, possibly for use with certain 2226 anticipated features of ISO 639-3. 2228 Ed Note: The following items are provided for the convenience of 2229 reviewers and will be removed from the final document. 2231 Changes between draft-ietf-ltru-registry-06 and this version are: 2233 o Modified the rules for creating the initial-registry draft to 2234 require purposefully omitted by eligible codes to be listed 2235 (#1034)(R.Presuhn) 2237 o Removed the example registry. The initial-registry draft is a 2238 better example. Added an informative reference to that document. 2239 (A.Phillips) 2241 o Modified the introduction to Section 2.2.4 and changed the use of 2242 "as used in" for some examples to clarify how UN M.49 codes and 2243 other larger regional codes are related to language tags. 2244 (K.Broome, P.Constable) 2246 o Removed nearly all of the text from Section 3.7 to [initial- 2247 registry]. A bit of new glue text pointing to that document was 2248 added. (F.Ellermann) 2250 o Updated the Section 5 section to reflect the removal of most of 2251 the text in Section 3.7 and to generally clean it up. This 2252 includes breaking it into subsections. (A.Phillips) 2254 9. References 2256 9.1 Normative References 2258 [ISO639-1] 2259 International Organization for Standardization, "ISO 639- 2260 1:2002, Codes for the representation of names of languages 2261 -- Part 1: Alpha-2 code", ISO Standard 639, 2002, . 2264 [ISO639-2] 2265 International Organization for Standardization, "ISO 639- 2266 2:1998 - Codes for the representation of names of 2267 languages -- Part 2: Alpha-3 code - edition 1", 2268 August 1988, . 2270 [ISO15924] 2271 ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for the 2272 representation of names of scripts", January 2004, . 2275 [ISO3166] International Organization for Standardization, "Codes for 2276 the representation of names of countries, 3rd edition", 2277 ISO Standard 3166, August 1988, . 2279 [UN_M.49] Statistical Division, United Nations, "Standard Country or 2280 Area Codes for Statistical Use", UN Standard Country or 2281 Area Codes for Statistical Use, Revision 4 (United Nations 2282 publication, Sales No. 98.XVII.9, June 1999, . 2284 [ISO10646] 2285 International Organization for Standardization, "ISO/IEC 2286 10646-1:2000. Information technology -- Universal 2287 Multiple-Octet Coded Character Set (UCS) -- Part 1: 2288 Architecture and Basic Multilingual Plane and ISO/IEC 2289 10646-2:2001. Information technology -- Universal 2290 Multiple-Octet Coded Character Set (UCS) -- Part 2: 2291 Supplementary Planes, as, from time to time, amended, 2292 replaced by a new edition or expanded by the addition of 2293 new parts", 2000, . 2295 [RFC2234bis] 2296 Crocker, D. and P. Overell, "Augmented BNF for Syntax 2297 Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 2298 (work in progress), March 2005. 2300 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 2301 3", BCP 9, RFC 2026, October 1996. 2303 [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in 2304 the IETF Standards Process", BCP 11, RFC 2028, 2305 October 1996. 2307 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 2308 Part Three: Message Header Extensions for Non-ASCII Text", 2309 RFC 2047, November 1996. 2311 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2312 Requirement Levels", BCP 14, RFC 2119, March 1997. 2314 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2315 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 2316 October 1998. 2318 [RFC2781] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of ISO 2319 10646", RFC 2781, February 2000. 2321 [RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of 2322 Understanding Concerning the Technical Work of the 2323 Internet Assigned Numbers Authority", RFC 2860, June 2000. 2325 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 2326 Timestamps", RFC 3339, July 2002. 2328 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2329 Text on Security Considerations", BCP 72, RFC 3552, 2330 July 2003. 2332 9.2 Informative References 2334 [initial-registry] 2335 Ewell, D., Ed., "Initial Language Subtag Registry", 2336 June 2005, . 2339 [iso639.principles] 2340 ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory 2341 Committee: Working principles for ISO 639 maintenance", 2342 March 2000, 2343 . 2346 [record-jar] 2347 Raymond, E., "The Art of Unix Programming", 2003. 2349 [XML10] Bray (et al), T., "Extensible Markup Language (XML) 1.0", 2350 02 2004. 2352 [XMLSchema] 2353 Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: 2354 Datatypes Second Edition", 10 2004, < 2355 http://www.w3.org/TR/xmlschema-2/>. 2357 [Unicode] Unicode Consortium, "The Unicode Consortium. The Unicode 2358 Standard, Version 4.1.0, defined by: The Unicode Standard, 2359 Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321- 2360 18578-1), as amended by Unicode 4.0.1 2361 (http://www.unicode.org/versions/Unicode4.0.1) and by 2362 Unicode 4.1.0 2363 (http://www.unicode.org/versions/Unicode4.1.0).", 2364 March 2005. 2366 [RFC1766] Alvestrand, H., "Tags for the Identification of 2367 Languages", RFC 1766, March 1995. 2369 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 2370 Word Extensions: Character Sets, Languages, and 2371 Continuations", RFC 2231, November 1997. 2373 [RFC3066] Alvestrand, H., "Tags for the Identification of 2374 Languages", BCP 47, RFC 3066, January 2001. 2376 Authors' Addresses 2378 Addison Phillips (editor) 2379 Quest Software 2381 Email: addison.phillips@quest.com 2383 Mark Davis (editor) 2384 IBM 2386 Email: mark.davis@us.ibm.com 2388 Appendix A. Acknowledgements 2390 Any list of contributors is bound to be incomplete; please regard the 2391 following as only a selection from the group of people who have 2392 contributed to make this document what it is today. 2394 The contributors to RFC 3066 and RFC 1766, the precursors of this 2395 document, made enormous contributions directly or indirectly to this 2396 document and are generally responsible for the success of language 2397 tags. 2399 The following people (in alphabetical order) contributed to this 2400 document or to RFCs 1766 and 3066: 2402 Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet, 2403 Nathaniel Borenstein, Karen Broome, Eric Brunner, Sean M. Burke, M.T. 2404 Carrasco Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter 2405 Constable, John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, 2406 Frank Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, 2407 Dirk-Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty 2408 Harold, Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle 2409 Jarnefors, Kent Karlsson, John Klensin, Alain LaBonte, Eric Mader, 2410 Ira McDonald, Keith Moore, Chris Newman, Masataka Ohta, Randy 2411 Presuhn, George Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry 2412 Sourbier, Otto Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha 2413 Wolf, Francois Yergeau and many, many others. 2415 Very special thanks must go to Harald Tveit Alvestrand, who 2416 originated RFCs 1766 and 3066, and without whom this document would 2417 not have been possible. Special thanks must go to Michael Everson, 2418 who has served as language tag reviewer for almost the complete 2419 period since the publication of RFC 1766. Special thanks to Doug 2420 Ewell, for his production of the first complete subtag registry, and 2421 his work in producing a test parser for verifying language tags. 2423 Appendix B. Examples of Language Tags (Informative) 2425 Simple language subtag: 2427 de (German) 2429 fr (French) 2431 ja (Japanese) 2433 i-enochian (example of a grandfathered tag) 2435 Language subtag plus Script subtag: 2437 zh-Hant (Chinese written using the Traditional Chinese script) 2439 zh-Hans (Chinese written using the Simplified Chinese script) 2441 sr-Cyrl (Serbian written using the Cyrillic script) 2443 sr-Latn (Serbian written using the Latin script) 2445 Language-Script-Region: 2447 zh-Hans-CN (Chinese written using the Simplified script as used in 2448 mainland China) 2450 sr-Latn-CS (Serbian written using the Latin script as used in 2451 Serbia and Montenegro) 2453 Language-Variant: 2455 sl-rozaj (Resian dialect of Slovenian 2457 sl-nedis (Nadiza dialect of Slovenian) 2459 Language-Region-Variant: 2461 de-CH-1901 (German as used in Switzerland using the 1901 variant 2462 [othography]) 2464 sl-IT-nedis (Slovenian as used in Italy, Nadiza dialect) 2466 Language-Script-Region-Variant: 2468 sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the 2469 Latin script as used in Italy. Note that this tag is NOT 2470 RECOMMENDED because subtag 'sl' has a Suppress-Script value of 2471 'Latn') 2473 Language-Region: 2475 de-DE (German for Germany) 2477 en-US (English as used in the United States) 2479 es-419 (Spanish appropriate for the Latin America and Caribbean 2480 region using the UN region code) 2482 Private-use subtags: 2484 de-CH-x-phonebk 2486 az-Arab-x-AZE-derbend 2488 Extended language subtags (examples ONLY: extended languages MUST be 2489 defined by revision or update to this document): 2491 zh-min 2493 zh-min-nan-Hant-CN 2495 Private-use registry values: 2497 x-whatever (private use using the singleton 'x') 2499 qaa-Qaaa-QM-x-southern (all private tags) 2501 de-Qaaa (German, with a private script) 2503 sr-Latn-QM (Serbian, Latin-script, private region) 2505 sr-Qaaa-CS (Serbian, private script, for Serbia and Montenegro) 2507 Tags that use extensions (examples ONLY: extensions MUST be defined 2508 by revision or update to this document or by RFC): 2510 en-US-u-islamCal 2512 zh-CN-a-myExt-x-private 2513 en-a-myExt-b-another 2515 Some Invalid Tags: 2517 de-419-DE (two region tags) 2519 a-DE (use of a single character subtag in primary position; note 2520 that there are a few grandfathered tags that start with "i-" that 2521 are valid) 2523 ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter 2524 prefix) 2526 Intellectual Property Statement 2528 The IETF takes no position regarding the validity or scope of any 2529 Intellectual Property Rights or other rights that might be claimed to 2530 pertain to the implementation or use of the technology described in 2531 this document or the extent to which any license under such rights 2532 might or might not be available; nor does it represent that it has 2533 made any independent effort to identify any such rights. Information 2534 on the procedures with respect to rights in RFC documents can be 2535 found in BCP 78 and BCP 79. 2537 Copies of IPR disclosures made to the IETF Secretariat and any 2538 assurances of licenses to be made available, or the result of an 2539 attempt made to obtain a general license or permission for the use of 2540 such proprietary rights by implementers or users of this 2541 specification can be obtained from the IETF on-line IPR repository at 2542 http://www.ietf.org/ipr. 2544 The IETF invites any interested party to bring to its attention any 2545 copyrights, patents or patent applications, or other proprietary 2546 rights that may cover technology that may be required to implement 2547 this standard. Please address the information to the IETF at 2548 ietf-ipr@ietf.org. 2550 Disclaimer of Validity 2552 This document and the information contained herein are provided on an 2553 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 2554 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 2555 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 2556 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 2557 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 2558 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 2560 Copyright Statement 2562 Copyright (C) The Internet Society (2005). This document is subject 2563 to the rights, licenses and restrictions contained in BCP 78, and 2564 except as set forth therein, the authors retain all their rights. 2566 Acknowledgment 2568 Funding for the RFC Editor function is currently provided by the 2569 Internet Society.