RFC 5646
Tags for Identifying Languages
Pages: 84
Best Current Practice: 47
→ Errata
BCP 47 is also: 4647
Obsoletes: 4646
Best Current Practice: 47
→ Errata
BCP 47 is also: 4647
Obsoletes: 4646
Part 2 of 4 – Pages 21 to 46
3. Registry Format and Maintenance
The IANA Language Subtag Registry ("the registry") contains a comprehensive list of all of the subtags valid in language tags. This allows implementers a straightforward and reliable way to validate language tags. The registry will be maintained so that, except for extension subtags, it is possible to validate all of the subtags that appear in a language tag under the provisions of this document or its revisions or successors. In addition, the meaning of the various subtags will be unambiguous and stable over time. (The meaning of private use subtags, of course, is not defined by the registry.) This section defines the registry along with the maintenance and update procedures associated with it, as well as a registry for extensions to language tags (Section 3.7).3.1. Format of the IANA Language Subtag Registry
The IANA Language Subtag Registry is a machine-readable file in the format described in this section, plus copies of the registration forms approved in accordance with the process described in Section 3.5. The existing registration forms for grandfathered and redundant tags taken from RFC 3066 have been maintained as part of the obsolete RFC 3066 registry. The subtags added to the registry by either [RFC4645] or [RFC5645] do not have separate registration forms (so no forms are archived for these additions).3.1.1. File Format
The registry is a [Unicode] text file and consists of a series of records in a format based on "record-jar" (described in [record-jar]). Each record, in turn, consists of a series of fields that describe the various subtags and tags. The actual registry file is encoded using the UTF-8 [RFC3629] character encoding. Each field can be considered a single, logical line of characters. Each field contains a "field-name" and a "field-body". These are separated by a "field-separator". The field-separator is a COLON character (U+003A) plus any surrounding whitespace. Each field is terminated by the newline sequence CRLF. The text in each field MUST be in Unicode Normalization Form C (NFC).
A collection of fields forms a "record". Records are separated by lines containing only the sequence "%%" (U+0025 U+0025). Although fields are logically a single line of text, each line of text in the file format is limited to 72 bytes in length. To accommodate this, the field-body can be split into a multiple-line representation; this is called "folding". Folding is done according to customary conventions for line-wrapping. This is typically on whitespace boundaries, but can occur between other characters when the value does not include spaces, such as when a language does not use whitespace between words. In any event, there MUST NOT be breaks inside a multibyte UTF-8 sequence or in the middle of a combining character sequence. For more information, see [UAX14]. Although the file format uses the Unicode character set and the file itself is encoded using the UTF-8 encoding, fields are restricted to the printable characters from the US-ASCII [ISO646] repertoire unless otherwise indicated in the description of a specific field (Section 3.1.2). The format of the registry is described by the following ABNF [RFC5234]. Character numbers (code points) are taken from Unicode, and terminals in the ABNF productions are in terms of characters rather than bytes. registry = record *("%%" CRLF record) record = 1*field field = ( field-name field-sep field-body CRLF ) field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)] field-sep = *SP ":" *SP field-body = *([[*SP CRLF] 1*SP] 1*CHARS) CHARS = (%x21-10FFFF) ; Unicode code points Figure 3: Registry Format ABNF The sequence '..' (U+002E U+002E) in a field-body denotes a range of values. Such a range represents all subtags of the same length that are in alphabetic or numeric order within that range, including the values explicitly mentioned. For example, 'a..c' denotes the values 'a', 'b', and 'c', and '11..13' denotes the values '11', '12', and '13'. All fields whose field-body contains a date value use the "full-date" format specified in [RFC3339]. For example, "2004-06-28" represents June 28, 2004, in the Gregorian calendar.
3.1.2. Record and Field Definitions
There are three types of records in the registry: "File-Date", "Subtag", and "Tag". The first record in the registry is always the "File-Date" record. This record occurs only once in the file and contains a single field whose field-name is "File-Date". The field-body of this record contains a date (see Section 5.1), making it possible to easily recognize different versions of the registry. File-Date: 2004-06-28 %% Figure 4: Example of the File-Date Record Subsequent records contain multiple fields and represent information about either subtags or tags. Both types of records have an identical structure, except that "Subtag" records contain a field with a field-name of "Subtag", while, unsurprisingly, "Tag" records contain a field with a field-name of "Tag". Field-names MUST NOT occur more than once per record, with the exception of the 'Description', 'Comments', and 'Prefix' fields. Each record MUST contain at least one of each of the following fields: o 'Type' * Type's field-body MUST consist of one of the following strings: "language", "extlang", "script", "region", "variant", "grandfathered", and "redundant"; it denotes the type of tag or subtag. o Either 'Subtag' or 'Tag' * Subtag's field-body contains the subtag being defined. This field MUST appear in all records whose 'Type' has one of these values: "language", "extlang", "script", "region", or "variant". * Tag's field-body contains a complete language tag. This field MUST appear in all records whose 'Type' has one of these values: "grandfathered" or "redundant". If the 'Type' is "grandfathered", then the 'Tag' field-body will be one of the tags listed in either the 'regular' or 'irregular' production found in Section 2.1.
o 'Description'
* Description's field-body contains a non-normative description
of the subtag or tag.
o 'Added'
* Added's field-body contains the date the record was registered
or, in the case of grandfathered or redundant tags, the date
the corresponding tag was registered under the rules of
[RFC1766] or [RFC3066].
Each record MAY also contain the following fields:
o 'Deprecated'
* Deprecated's field-body contains the date the record was
deprecated. In some cases, this value is earlier than that of
the 'Added' field in the same record. That is, the date of
deprecation preceded the addition of the record to the
registry.
o 'Preferred-Value'
* Preferred-Value's field-body contains a canonical mapping from
this record's value to a modern equivalent that is preferred in
its place. Depending on the value of the 'Type' field, this
value can take different forms:
+ For fields of type 'language', 'Preferred-Value' contains
the primary language subtag that is preferred when forming
the language tag.
+ For fields of type 'script', 'region', or 'variant',
'Preferred-Value' contains the subtag of the same type that
is preferred for forming the language tag.
+ For fields of type 'extlang', 'grandfathered', or
'redundant', 'Preferred-Value' contains an "extended
language range" [RFC4647] that is preferred for forming the
language tag. That is, the preferred language tag will
contain, in order, each of the subtags that appears in the
'Preferred-Value'; additional fields can be included in a
language tag, as described elsewhere in this document. For
example, the replacement for the grandfathered tag "zh-min-
nan" (Min Nan Chinese) is "nan", which can be used as the
basis for tags such as "nan-Hant" or "nan-TW" (note that the
extended language subtag form such as "zh-nan-Hant" or "zh-
nan-TW" can also be used).
o 'Prefix'
* Prefix's field-body contains a valid language tag that is
RECOMMENDED as one possible prefix to this record's subtag.
This field MAY appear in records whose 'Type' field-body is
either 'extlang' or 'variant' (it MUST NOT appear in any other
record type).
o 'Suppress-Script'
* Suppress-Script's field-body contains a script subtag that
SHOULD NOT be used to form language tags with the associated
primary or extended language subtag. This field MUST appear
only in records whose 'Type' field-body is 'language' or
'extlang'. See Section 4.1.
o 'Macrolanguage'
* Macrolanguage's field-body contains a primary language subtag
defined by ISO 639 as the "macrolanguage" that encompasses this
language subtag. This field MUST appear only in records whose
'Type' field-body is either 'language' or 'extlang'.
o 'Scope'
* Scope's field-body contains information about a primary or
extended language subtag indicating the type of language code
according to ISO 639. The values permitted in this field are
"macrolanguage", "collection", "special", and "private-use".
This field only appears in records whose 'Type' field-body is
either 'language' or 'extlang'. When this field is omitted,
the language is an individual language.
o 'Comments'
* Comments's field-body contains additional information about the
subtag, as deemed appropriate for understanding the registry
and implementing language tags using the subtag or tag.
Future versions of this document might add additional fields to the
registry; implementations SHOULD ignore fields found in the registry
that are not defined in this document.
3.1.3. Type Field
The field 'Type' contains the string identifying the record type in which it appears. Values for the 'Type' field-body are: "language" (Section 2.2.1); "extlang" (Section 2.2.2); "script" (Section 2.2.3); "region" (Section 2.2.4); "variant" (Section 2.2.5); "grandfathered" or "redundant" (Section 2.2.8).3.1.4. Subtag and Tag Fields
The field 'Subtag' contains the subtag defined in the record. The field 'Tag' appears in records whose 'Type' is either 'grandfathered' or 'redundant' and contains a tag registered under [RFC3066]. The 'Subtag' field-body MUST follow the casing conventions described in Section 2.1.1. All subtags use lowercase letters in the field- body, with two exceptions: Subtags whose 'Type' field is 'script' (in other words, subtags defined by ISO 15924) MUST use titlecase. Subtags whose 'Type' field is 'region' (in other words, the non- numeric region subtags defined by ISO 3166-1) MUST use all uppercase. The 'Tag' field-body MUST be formatted according to the rules described in Section 2.1.1.3.1.5. Description Field
The field 'Description' contains a description of the tag or subtag in the record. The 'Description' field MAY appear more than once per record. The 'Description' field MAY include the full range of Unicode characters. At least one of the 'Description' fields MUST be written or transcribed into the Latin script; additional 'Description' fields MAY be in any script or language. The 'Description' field is used for identification purposes. Descriptions SHOULD contain all and only that information necessary to distinguish one subtag from others with which it might be confused. They are not intended to provide general background information or to provide all possible alternate names or designations. 'Description' fields don't necessarily represent the actual native name of the item in the record, nor are any of the descriptions guaranteed to be in any particular language (such as English or French, for example).
Descriptions in the registry that correspond to ISO 639, ISO 15924, ISO 3166-1, or UN M.49 codes are intended only to indicate the meaning of that identifier as defined in the source standard at the time it was added to the registry or as subsequently modified, within the bounds of the stability rules (Section 3.4), via subsequent registration. The 'Description' does not replace the content of the source standard itself. 'Description' fields are not intended to be the localized English names for the subtags. Localization or translation of language tag and subtag descriptions is out of scope of this document. For subtags taken from a source standard (such as ISO 639 or ISO 15924), the 'Description' fields in the record are also initially taken from that source standard. Multiple descriptions in the source standard are split into separate 'Description' fields. The source standard's descriptions MAY be edited or modified, either prior to insertion or via the registration process, and additional or extraneous descriptions omitted or removed. Each 'Description' field MUST be unique within the record in which it appears, and formatting variations of the same description SHOULD NOT occur in that specific record. For example, while the ISO 639-1 code 'fy' has both the description "Western Frisian" and the description "Frisian, Western" in that standard, only one of these descriptions appears in the registry. To help ensure that users do not become confused about which subtag to use, 'Description' fields assigned to a record of any specific type ('language', 'extlang', 'script', and so on) MUST be unique within that given record type with the following exception: if a particular 'Description' field occurs in multiple records of a given type, then at most one of the records can omit the 'Deprecated' field. All deprecated records that share a 'Description' MUST have the same 'Preferred-Value', and all non-deprecated records MUST be that 'Preferred-Value'. This means that two records of the same type that share a 'Description' are also semantically equivalent and no more than one record with a given 'Description' is preferred for that meaning. For example, consider the 'language' subtags 'zza' (Zaza) and 'diq' (Dimli). It so happens that 'zza' is a macrolanguage enclosing 'diq' and thus also has a description in ISO 639-3 of "Dimli". This description was edited to read "Dimli (macrolanguage)" in the registry record for 'zza' to prevent a collision. By contrast, the subtags 'he' and 'iw' share a 'Description' value of "Hebrew"; this is permitted because 'iw' is deprecated and its 'Preferred-Value' is 'he'.
For fields of type 'language', the first 'Description' field appearing in the registry corresponds whenever possible to the Reference Name assigned by ISO 639-3. This helps facilitate cross- referencing between ISO 639 and the registry. When creating or updating a record due to the action of one of the source standards, the Language Subtag Reviewer MAY edit descriptions to correct irregularities in formatting (such as misspellings, inappropriate apostrophes or other punctuation, or excessive or missing spaces) prior to submitting the proposed record to the ietf-languages@iana.org list for consideration.3.1.6. Deprecated Field
The field 'Deprecated' contains the date the record was deprecated and MAY be added, changed, or removed from any record via the maintenance process described in Section 3.3 or via the registration process described in Section 3.5. Usually, the addition of a 'Deprecated' field is due to the action of one of the standards bodies, such as ISO 3166, withdrawing a code. Although valid in language tags, subtags and tags with a 'Deprecated' field are deprecated, and validating processors SHOULD NOT generate these subtags. Note that a record that contains a 'Deprecated' field and no corresponding 'Preferred-Value' field has no replacement mapping. In some historical cases, it might not have been possible to reconstruct the original deprecation date. For these cases, an approximate date appears in the registry. Some subtags and some grandfathered or redundant tags were deprecated before the initial creation of the registry. The exact rules for this appear in Section 2 of [RFC4645]. Note that these records have a 'Deprecated' field with an earlier date then the corresponding 'Added' field!3.1.7. Preferred-Value Field
The field 'Preferred-Value' contains a mapping between the record in which it appears and another tag or subtag (depending on the record's 'Type'). The value in this field is used for canonicalization (see Section 4.5). In cases where the subtag or tag also has a 'Deprecated' field, then the 'Preferred-Value' is RECOMMENDED as the best choice to represent the value of this record when selecting a language tag. Records containing a 'Preferred-Value' fall into one of these four groups:
1. ISO 639 language codes that were later withdrawn in favor of
other codes. These values are mostly a historical curiosity.
The 'he'/'iw' pairing above is an example of this.
2. Subtags (with types other than language or extlang) taken from
codes or values that have been withdrawn in favor of a new code.
In particular, this applies to region subtags taken from ISO
3166-1, because sometimes a country will change its name or
administration in such a way that warrants a new region code. In
some cases, countries have reverted to an older name, which might
already be encoded. For example, the subtag 'ZR' (Zaire) was
replaced by the subtag 'CD' (Democratic Republic of the Congo)
when that country's name was changed.
3. Tags or subtags that have become obsolete because the values they
represent were later encoded. Many of the grandfathered or
redundant tags were later encoded by ISO 639, for example, and
fall into this grouping. For example, "i-klingon" was deprecated
when the subtag 'tlh' was added. The record for "i-klingon" has
a 'Preferred-Value' of 'tlh'.
4. Extended language subtags always have a mapping to their
identical primary language subtag. For example, the extended
language subtag 'yue' (Cantonese) can be used to form the tag
"zh-yue". It has a 'Preferred-Value' mapping to the primary
language subtag 'yue', meaning that a tag such as
"zh-yue-Hant-HK" can be canonicalized to "yue-Hant-HK".
Records other than those of type 'extlang' that contain a 'Preferred-
Value' field MUST also have a 'Deprecated' field. This field
contains the date on which the tag or subtag was deprecated in favor
of the preferred value.
For records of type 'extlang', the 'Preferred-Value' field appears
without a corresponding 'Deprecated' field. An implementation MAY
ignore these preferred value mappings, although if it ignores the
mapping, it SHOULD do so consistently. It SHOULD also treat the
'Preferred-Value' as equivalent to the mapped item. For example, the
tags "zh-yue-Hant-HK" and "yue-Hant-HK" are semantically equivalent
and ought to be treated as if they were the same tag.
Occasionally, the deprecated code is preferred in certain contexts.
For example, both "iw" and "he" can be used in the Java programming
language, but "he" is converted on input to "iw", which is thus the
canonical form in Java.
'Preferred-Value' mappings in records of type 'region' sometimes do 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. For example, the region subtag 'YD' (Democratic Yemen) was deprecated in favor of the subtag 'YE' (Yemen) when those two countries unified in 1990. A 'Preferred-Value' MAY be added to, changed, or removed from records according to the rules in Section 3.3. Addition, modification, or removal of a 'Preferred-Value' field in a record does not imply that content using the affected subtag needs to be retagged. The 'Preferred-Value' fields in records of type "grandfathered" and "redundant" each contain an "extended language range" [RFC4647] that is strongly RECOMMENDED for use in place of the record's value. In many cases, these mappings were created via deprecation of the tags during the period before [RFC4646] was adopted. For example, the tag "no-nyn" was deprecated in favor of the ISO 639-1-defined language code 'nn'. The 'Preferred-Value' field in subtag records of type "extlang" also contains an "extended language range". This allows the subtag to be deprecated in favor of either a single primary language subtag or a new language-extlang sequence. Usually, the addition, removal, or change of a 'Preferred-Value' field for a subtag is done to reflect changes in one of the source standards. For example, if an ISO 3166-1 region code is deprecated in favor of another code, that SHOULD result in the addition of a 'Preferred-Value' field. Changes to one subtag can affect other subtags as well: when proposing changes to the registry, the Language Subtag Reviewer MUST review the registry for such effects and propose the necessary changes using the process in Section 3.5, although anyone MAY request such changes. For example: Suppose that subtag 'XX' has a 'Preferred-Value' of 'YY'. If 'YY' later changes to have a 'Preferred-Value' of 'ZZ', then the 'Preferred-Value' for 'XX' MUST also change to be 'ZZ'. Suppose that a registered language subtag 'dialect' represents a language not yet available in any part of ISO 639. The later addition of a corresponding language code in ISO 639 SHOULD result in the addition of a 'Preferred-Value' for 'dialect'.
3.1.8. Prefix Field
The field 'Prefix' contains a valid language tag that is RECOMMENDED as one possible prefix to this record's subtag, perhaps with other subtags. That is, when including an extended language or a variant subtag that has at least one 'Prefix' in a language tag, the resulting tag SHOULD match at least one of the subtag's 'Prefix' fields using the "Extended Filtering" algorithm (see [RFC4647]), and each of the subtags in that 'Prefix' SHOULD appear before the subtag itself. The 'Prefix' field MUST appear exactly once in a record of type 'extlang'. The 'Prefix' field MAY appear multiple times (or not at all) in records of type 'variant'. Additional fields of this type MAY be added to a 'variant' record via the registration process, provided the 'variant' record already has at least one 'Prefix' field. Each 'Prefix' field indicates a particular sequence of subtags that form a meaningful tag with this subtag. For example, the extended language subtag 'cmn' (Mandarin Chinese) only makes sense with its prefix 'zh' (Chinese). Similarly, 'rozaj' (Resian, a dialect of Slovenian) would be appropriate when used with its prefix 'sl' (Slovenian), while tags such as "is-1994" are not appropriate (and probably not meaningful). Although the 'Prefix' for 'rozaj' is "sl", other subtags might appear between them. For example, the tag "sl- IT-rozaj" (Slovenian, Italy, Resian) matches the 'Prefix' "sl". The 'Prefix' also indicates when variant subtags make sense when used together (many that otherwise share a 'Prefix' are mutually exclusive) and what the relative ordering of variants is supposed to be. For example, the variant '1994' (Standardized Resian orthography) has several 'Prefix' fields in the registry ("sl-rozaj", "sl-rozaj-biske", "sl-rozaj-njiva", "sl-rozaj-osojs", and "sl-rozaj- solba"). This indicates not only that '1994' is appropriate to use with each of these five Resian variant subtags ('rozaj', 'biske', 'njiva', 'osojs', and 'solba'), but also that it SHOULD appear following any of these variants in a tag. Thus, the language tag ought to take the form "sl-rozaj-biske-1994", rather than "sl-1994- rozaj-biske" or "sl-rozaj-1994-biske". If a record includes no 'Prefix' field, a 'Prefix' field MUST NOT be added to the record at a later date. Otherwise, changes (additions, deletions, or modifications) to the set of 'Prefix' fields MAY be registered, as long as they strictly widen the range of language tags that are recommended. For example, a 'Prefix' with the value "be- Latn" (Belarusian, Latin script) could be replaced by the value "be" (Belarusian) but not by the value "ru-Latn" (Russian, Latin script)
or the value "be-Latn-BY" (Belarusian, Latin script, Belarus), since these latter either change or narrow the range of suggested tags. The field-body of the 'Prefix' field MUST NOT conflict with any 'Prefix' already registered for a given record. Such a conflict would occur when no valid tag could be constructed that would contain the prefix, such as when two subtags each have a 'Prefix' that contains the other subtag. For example, suppose that the subtag 'avariant' has the prefix "es-bvariant". Then the subtag 'bvariant' cannot be assigned the prefix 'avariant', for that would require a tag of the form "es-avariant-bvariant-avariant", which would not be valid.3.1.9. Suppress-Script Field
The field 'Suppress-Script' contains a script subtag (whose record appears in the registry). The field 'Suppress-Script' MUST appear only in records whose 'Type' field-body is either 'language' or 'extlang'. This field MUST NOT appear more than one time in a record. This field indicates a script used to write the overwhelming majority of documents for the given language. The subtag for such a script therefore adds no distinguishing information to a language tag and thus SHOULD NOT be used for most documents in that language. Omitting the script subtag indicated by this field helps ensure greater compatibility between the language tags generated according to the rules in this document and language tags and tag processors or consumers based on RFC 3066. For example, virtually all Icelandic documents are written in the Latin script, making the subtag 'Latn' redundant in the tag "is-Latn". Many language subtag records do not have a 'Suppress-Script' field. The lack of a 'Suppress-Script' might indicate that the language is customarily written in more than one script or that the language is not customarily written at all. It might also mean that sufficient information was not available when the record was created and thus remains a candidate for future registration.3.1.10. Macrolanguage Field
The field 'Macrolanguage' contains a primary language subtag (whose record appears in the registry). This field indicates a language that encompasses this subtag's language according to assignments made by ISO 639-3. ISO 639-3 labels some languages in the registry as "macrolanguages". ISO 639-3 defines the term "macrolanguage" to mean "clusters of
closely-related language varieties that [...] can be considered distinct individual languages, yet in certain usage contexts a single language identity for all is needed". These correspond to codes registered in ISO 639-2 as individual languages that were found to correspond to more than one language in ISO 639-3. A language contained within a macrolanguage is called an "encompassed language". The record for each encompassed language contains a 'Macrolanguage' field in the registry; the macrolanguages themselves are not specially marked. Note that some encompassed languages have ISO 639-1 or ISO 639-2 codes. The 'Macrolanguage' field can only occur in records of type 'language' or 'extlang'. Only values assigned by ISO 639-3 will be considered for inclusion. 'Macrolanguage' fields MAY be added or removed via the normal registration process whenever ISO 639-3 defines new values or withdraws old values. Macrolanguages are informational, and MAY be removed or changed if ISO 639-3 changes the values. For more information on the use of this field and choosing between macrolanguage and encompassed language subtags, see Section 4.1.1. For example, the language subtags 'nb' (Norwegian Bokmal) and 'nn' (Norwegian Nynorsk) each have a 'Macrolanguage' field with a value of 'no' (Norwegian). For more information, see Section 4.1.3.1.11. Scope Field
The field 'Scope' contains classification information about a primary or extended language subtag derived from ISO 639. Most languages have a scope of 'individual', which means that the language is not a macrolanguage, collection, special code, or private use. That is, it is what one would normally consider to be 'a language'. Any primary or extended language subtag that has no 'Scope' field is an individual language. 'Scope' information can sometimes be helpful in selecting language tags, since it indicates the purpose or "scope" of the code assignment within ISO 639. The available values are: o 'macrolanguage' - Indicates a macrolanguage as defined by ISO 639-3 (see Section 3.1.10). A macrolanguage is a cluster of closely related languages that are sometimes considered to be a single language. o 'collection' - Indicates a subtag that represents a collection of languages, typically related by some type of historical, geographical, or linguistic association. Unlike a macrolanguage,
a collection can contain languages that are only loosely related
and a collection cannot be used interchangeably with languages
that belong to it.
o 'special' - Indicates a special language code. These are subtags
used for identifying linguistic attributes not particularly
associated with a concrete language. These include codes for when
the language is undetermined or for non-linguistic content.
o 'private-use' - Indicates a code reserved for private use in the
underlying standard. Subtags with this scope can be used to
indicate a primary language for which no ISO 639 or registered
assignment exists.
The 'Scope' field MAY appear in records of type 'language' or
'extlang'. Note that many of the prefixes for extended language
subtags will have a 'Scope' of 'macrolanguage' (although some will
not) and that many languages that have a 'Scope' of 'macrolanguage'
will have extended language subtags associated with them.
The 'Scope' field MAY be added, modified, or removed via the
registration process, provided the change mirrors changes made by ISO
639 to the assignment's classification. Such a change is expected to
be rare.
For example, the primary language subtag 'zh' (Chinese) has a 'Scope'
of 'macrolanguage', while its enclosed language 'nan' (Min Nan
Chinese) has a 'Scope' of 'individual'. The special value 'und'
(Undetermined) has a 'Scope' of 'special'. The ISO 639-5 collection
'gem' (Germanic languages) has a 'Scope' of 'collection'.
3.1.12. Comments Field
The field 'Comments' contains additional information about the record
and MAY appear more than once per record. The field-body MAY include
the full range of Unicode characters and is not restricted to any
particular script. This field MAY be inserted or changed via the
registration process, and no guarantee of stability is provided.
The content of this field is not restricted, except by the need to
register the information, the suitability of the request, and by
reasonable practical size limitations. The primary reason for the
'Comments' field is subtag identification -- to help distinguish the
subtag from others with which it might be confused as an aid to
usage. Large amounts of information about the use, history, or
general background of a subtag are frowned upon, as these generally
belong in a registration request rather than in the registry.
3.2. Language Subtag Reviewer
The Language Subtag Reviewer moderates the ietf-languages@iana.org mailing list, responds to requests for registration, and performs the other registry maintenance duties described in Section 3.3. Only the Language Subtag Reviewer is permitted to request IANA to change, update, or add records to the Language Subtag Registry. The Language Subtag Reviewer MAY delegate list moderation and other clerical duties as needed. The Language Subtag Reviewer is appointed by the IESG for an indefinite term, subject to removal or replacement at the IESG's discretion. The IESG will solicit nominees for the position (upon adoption of this document or upon a vacancy) and then solicit feedback on the nominees' qualifications. Qualified candidates should be familiar with BCP 47 and its requirements; be willing to fairly, responsively, and judiciously administer the registration process; and be suitably informed about the issues of language identification so that the reviewer can assess the claims and draw upon the contributions of language experts and subtag requesters. The subsequent performance or decisions of the Language Subtag Reviewer MAY be appealed to the IESG under the same rules as other IETF decisions (see [RFC2026]). The IESG can reverse or overturn the decisions of the Language Subtag Reviewer, provide guidance, or take other appropriate actions.3.3. Maintenance of the Registry
Maintenance of the registry requires that, as codes are assigned or withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language Subtag Reviewer MUST evaluate each change and determine the appropriate course of action according to the rules in this document. Such updates follow the registration process described in Section 3.5. Usually, the Language Subtag Reviewer will start the process for the new or updated record by filling in the registration form and submitting it. If a change to one of these standards takes place and the Language Subtag Reviewer does not do this in a timely manner, then any interested party MAY submit the form. Thereafter, the registration process continues normally. Note that some registrations affect other subtags--perhaps more than one--as when a region subtag is being deprecated in favor of a new value. The Language Subtag Reviewer is responsible for ensuring that any such changes are properly registered, with each change requiring its own registration form.
The Language Subtag Reviewer MUST ensure that new subtags meet the requirements elsewhere in this document (and most especially in Section 3.4) or submit an appropriate registration form for an alternate subtag as described in that section. Each individual subtag affected by a change MUST be sent to the ietf-languages@iana.org list with its own registration form and in a separate message.3.4. Stability of IANA Registry Entries
The stability of entries and their meaning in the registry is critical to the long-term stability of language tags. The rules in this section guarantee that a specific language tag's meaning is stable over time and will not change. These rules specifically deal with how changes to codes (including withdrawal and deprecation of codes) maintained by ISO 639, ISO 15924, ISO 3166, and UN M.49 are reflected in the IANA Language Subtag Registry. Assignments to the IANA Language Subtag Registry MUST follow the following stability rules: 1. Values in the fields 'Type', 'Subtag', 'Tag', and 'Added' MUST NOT be changed and are guaranteed to be stable over time. 2. Values in the fields 'Preferred-Value' and 'Deprecated' MAY be added, altered, or removed via the registration process. These changes SHOULD be limited to changes necessary to mirror changes in one of the underlying standards (ISO 639, ISO 15924, ISO 3166-1, or UN M.49) and typically alteration or removal of a 'Preferred-Value' is limited specifically to region codes. 3. Values in the 'Description' field MUST NOT be changed in a way that would invalidate any existing tags. The description MAY be broadened somewhat in scope, changed to add information, or adapted to the most common modern usage. For example, countries occasionally change their names; a historical example of this is "Upper Volta" changing to "Burkina Faso". 4. Values in the field 'Prefix' MAY be added to existing records of type 'variant' via the registration process, provided the 'variant' already has at least one 'Prefix'. A 'Prefix' field SHALL NOT be registered for any 'variant' that has no existing 'Prefix' field. If a prefix is added to a variant record, 'Comment' fields MAY be used to explain different usages with the various prefixes.
5. Values in the field 'Prefix' in records of type 'variant' MAY
also be modified, so long as the modifications broaden the set
of prefixes. That is, a prefix MAY be replaced by one of its
own prefixes. For example, the prefix "en-US" could be replaced
by "en", but not by the prefixes "en-Latn", "fr", or "en-US-
boont". If one of those prefix values were needed, it would
have to be separately registered.
6. Values in the field 'Prefix' in records of type 'extlang' MUST
NOT be added, modified, or removed.
7. The field 'Prefix' MUST NOT be removed from any record in which
it appears. This field SHOULD be included in the initial
registration of any records of type 'variant' and MUST be
included in any records of type 'extlang'.
8. The field 'Comments' MAY be added, changed, modified, or removed
via the registration process or any of the processes or
considerations described in this section.
9. The field 'Suppress-Script' MAY be added or removed via the
registration process.
10. The field 'Macrolanguage' MAY be added or removed via the
registration process, but only in response to changes made by
ISO 639. The 'Macrolanguage' field appears whenever a language
has a corresponding macrolanguage in ISO 639. That is, the
'Macrolanguage' fields in the registry exactly match those of
ISO 639. No other macrolanguage mappings will be considered for
registration.
11. The field 'Scope' MAY be added or removed from a primary or
extended language subtag after initial registration, and it MAY
be modified in order to match any changes made by ISO 639.
Changes to the 'Scope' field MUST mirror changes made by ISO
639. Note that primary or extended language subtags whose
records do not contain a 'Scope' field (that is, most of them)
are individual languages as described in Section 3.1.11.
12. Primary and extended language subtags (other than independently
registered values created using the registration process) are
created according to the assignments of the various parts of ISO
639, as follows:
A. Codes assigned by ISO 639-1 that do not conflict with
existing two-letter primary language subtags and that have
no corresponding three-letter primary defined in the
registry are entered into the IANA registry as new records
of type 'language'. Note that languages given an ISO 639-1
code cannot be given extended language subtags, even if
encompassed by a macrolanguage.
B. Codes assigned by ISO 639-3 or ISO 639-5 that do not
conflict with existing three-letter primary language subtags
and that do not have ISO 639-1 codes assigned (or expected
to be assigned) are entered into the IANA registry as new
records of type 'language'. Note that these two standards
now comprise a superset of ISO 639-2 codes. Codes that have
a defined 'macrolanguage' mapping at the time of their
registration MUST contain a 'Macrolanguage' field.
C. Codes assigned by ISO 639-3 MAY also be considered for an
extended language subtag registration. Note that they MUST
be assigned a primary language subtag record of type
'language' even when an 'extlang' record is proposed. When
considering extended language subtag assignment, these
criteria apply:
1. If a language has a macrolanguage mapping, and that
macrolanguage has other encompassed languages that are
assigned extended language subtags, then the new
language SHOULD have an 'extlang' record assigned to it
as well. For example, any language with a macrolanguage
of 'zh' or 'ar' would be assigned an 'extlang' record.
2. 'Extlang' records SHOULD NOT be created for languages if
other languages encompassed by the macrolanguage do not
also include 'extlang' records. For example, if a new
Serbo-Croatian ('sh') language were registered, it would
not get an extlang record because other languages
encompassed, such as Serbian ('sr'), do not include one
in the registry.
3. Sign languages SHOULD have an 'extlang' record with a
'Prefix' of 'sgn'.
4. 'Extlang' records MUST NOT be created for items already
in the registry. Extended language subtags will only be
considered at the time of initial registration.
5. Extended language subtag records MUST include the fields
'Prefix' and 'Preferred-Value' with field values
assigned as described in Section 2.2.2.
D. Any other codes assigned by ISO 639-2 that do not conflict
with existing three-letter primary or extended language
subtags and that do not have ISO 639-1 two-letter codes
assigned are entered into the IANA registry as new records
of type 'language'. This type of registration is not
supposed to occur in the future.
13. Codes assigned by ISO 15924 and ISO 3166-1 that do not conflict
with existing subtags of the associated type and whose meaning
is not the same as an existing subtag of the same type are
entered into the IANA registry as new records.
14. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that are
withdrawn by their respective maintenance or registration
authority remain valid in language tags. A 'Deprecated' field
containing the date of withdrawal MUST be added to the record.
If a new record of the same type is added that represents a
replacement value, then a 'Preferred-Value' field MAY also be
added. The registration process MAY be used to add comments
about the withdrawal of the code by the respective standard.
For example: the region code 'TL' was assigned to the country
'Timor-Leste', replacing the code 'TP' (which was assigned to
'East Timor' when it was under administration by Portugal).
The subtag 'TP' remains valid in language tags, but its
record contains the 'Preferred-Value' of 'TL' and its field
'Deprecated' contains the date the new code was assigned
('2004-07-06').
15. Codes assigned by ISO 639, ISO 15924, or ISO 3166-1 that
conflict with existing subtags of the associated type, including
subtags that are deprecated, MUST NOT be entered into the
registry. The following additional considerations apply to
subtag values that are reassigned:
A. For ISO 639 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry, as
soon as practical, a registered language subtag as an
alternate value for the new code. The form of the
registered language subtag will be at the discretion of the
Language Subtag Reviewer and MUST conform to other
restrictions on language subtags in this document.
B. For all subtags whose meaning is derived from an external
standard (that is, by ISO 639, ISO 15924, ISO 3166-1, or UN
M.49), if a new meaning is assigned to an existing code and
the new meaning broadens the meaning of that code, then the
meaning for the associated subtag MAY be changed to match.
The meaning of a subtag MUST NOT be narrowed, however, as
this can result in an unknown proportion of the existing
uses of a subtag becoming invalid. Note: the ISO 639
registration authority (RA) has adopted a similar stability
policy.
C. For ISO 15924 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry, as
soon as practical, a registered variant subtag as an
alternate value for the new code. The form of the
registered variant subtag will be at the discretion of the
Language Subtag Reviewer and MUST conform to other
restrictions on variant subtags in this document.
D. For ISO 3166-1 codes, if the newly assigned code's meaning
is associated with the same UN M.49 code as another 'region'
subtag, then the existing region subtag remains as the
preferred value for that region and no new entry is created.
A comment MAY be added to the existing region subtag
indicating the relationship to the new ISO 3166-1 code.
E. For ISO 3166-1 codes, if the newly assigned code's meaning
is associated with a UN M.49 code that is not represented by
an existing region subtag, then the Language Subtag
Reviewer, as described in Section 3.5, SHALL prepare a
proposal for entering the appropriate UN M.49 country code
as an entry in the IANA registry.
F. For ISO 3166-1 codes, if there is no associated UN numeric
code, then the Language Subtag Reviewer SHALL petition the
UN to create one. If there is no response from the UN
within 90 days of the request being sent, the Language
Subtag Reviewer SHALL prepare a proposal for entering in the
IANA registry, as soon as practical, a registered variant
subtag as an alternate value for the new code. The form of
the registered variant subtag will be at the discretion of
the Language Subtag Reviewer and MUST conform to other
restrictions on variant subtags in this document. This
situation is very unlikely to ever occur.
16. UN M.49 has codes for both "countries and areas" (such as '276'
for Germany) and "geographical regions and sub-regions" (such as
'150' for Europe). UN M.49 country or area codes for which
there is no corresponding ISO 3166-1 code MUST NOT be
registered, except as a surrogate for an ISO 3166-1 code that is
blocked from registration by an existing subtag.
If such a code becomes necessary, then the maintenance agency
for ISO 3166-1 SHALL first be petitioned to assign a code to the
region. If the petition for a code assignment by ISO 3166-1 is
refused or not acted on in a timely manner, the registration
process described in Section 3.5 can then be used to register
the corresponding UN M.49 code. This way, UN M.49 codes remain
available as the value of last resort in cases where ISO 3166-1
reassigns a deprecated value in the registry.
17. The redundant and grandfathered entries together form the
complete list of tags registered under [RFC3066]. The redundant
tags are those previously registered tags that can now be formed
using the subtags defined in the registry. The grandfathered
entries include those that can never be legal because they are
'irregular' (that is, they do not match the 'langtag' production
in Figure 1), are limited by rule (subtags such as 'nyn' and
'min' look like the extlang production, but cannot be registered
as extended language subtags), or their subtags are
inappropriate for registration. All of the grandfathered tags
are listed in either the 'regular' or the 'irregular'
productions in the ABNF. Under [RFC4646] it was possible for
grandfathered tags to become redundant. However, all of the
tags for which this was possible became redundant before this
document was produced. So the set of redundant and
grandfathered tags is now permanent and immutable: new entries
of either type MUST NOT be added and existing entries MUST NOT
be removed. The decision-making process about which tags were
initially grandfathered and which were made redundant is
described in [RFC4645].
Many of the grandfathered tags are deprecated -- indeed, they
were deprecated even before [RFC4646]. For example, the tag
"art-lojban" was deprecated in favor of the primary language
subtag 'jbo'. These tags could have been made 'redundant' by
registering some of their subtags as 'variants'. The 'variant-
like' subtags in the grandfathered registrations SHALL NOT be
registered in the future, even with a similar or identical
meaning.
3.5. Registration Procedure for Subtags
The procedure given here MUST be used by anyone who wants to use a
subtag not currently in the IANA Language Subtag Registry or who
wishes to add, modify, update, or remove information in existing
records as permitted by this document.
Only subtags of type 'language' and 'variant' will be considered for
independent registration of new subtags. Subtags needed for
stability and subtags necessary to keep the registry synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits defined by this document also use this process, as described in Section 3.3 and subject to stability provisions as described in Section 3.4. Registration requests are accepted relating to information in the 'Comments', 'Deprecated', 'Description', 'Prefix', 'Preferred-Value', 'Macrolanguage', or 'Suppress-Script' fields in a subtag's record as described in Section 3.4. Changes to all other fields in the IANA registry are NOT permitted. Registering a new subtag or requesting modifications to an existing tag or subtag starts with the requester filling out the registration form reproduced below. Note that each response is not limited in size so that the request can adequately describe the registration. The fields in the "Record Requested" section need to follow the requirements in Section 3.1 before the record will be approved. LANGUAGE SUBTAG REGISTRATION FORM 1. Name of requester: 2. E-mail address of requester: 3. Record Requested: Type: Subtag: Description: Prefix: Preferred-Value: Deprecated: Suppress-Script: Macrolanguage: Comments: 4. Intended meaning of the subtag: 5. Reference to published description of the language (book or article): 6. Any other relevant information: Figure 5: The Language Subtag Registration Form Examples of completed registration forms can be found in Appendix B. A complete list of approved registration forms is online through http://www.iana.org; readers should note that the Language Tag Registry is now obsolete and should instead look for the Language Subtag Registry.
The subtag registration form MUST be sent to <ietf-languages@iana.org>. Registration requests receive a two-week review period before being approved and submitted to IANA for inclusion in the registry. If modifications are made to the request during the course of the registration process (such as corrections to meet the requirements in Section 3.1 or to make the 'Description' fields unique for the given record type), the modified form MUST also be sent to <ietf-languages@iana.org> at least one week prior to submission to IANA. The ietf-languages list is an open list and can be joined by sending a request to <ietf-languages-request@iana.org>. The list can be hosted by IANA or any third party at the request of IESG. Before forwarding any registration to IANA, the Language Subtag Reviewer MUST ensure that all requirements in this document are met. This includes ensuring that values in the 'Subtag' field match case according to the description in Section 3.1.4 and that 'Description' fields are unique for the given record type as described in Section 3.1.5. The Reviewer MUST also ensure that an appropriate File-Date record is included in the request, to assist IANA when updating the registry (see Section 5.1). Some fields in both the registration form as well as the registry record itself permit the use of non-ASCII characters. Registration requests SHOULD use the UTF-8 encoding for consistency and clarity. However, since some mail clients do not support this encoding, other encodings MAY be used for the registration request. The Language Subtag Reviewer is responsible for ensuring that the proper Unicode characters appear in both the archived request form and the registry record. In the case of a transcription or encoding error by IANA, the Language Subtag Reviewer will request that the registry be repaired, providing any necessary information to assist IANA. Extended language subtags (type 'extlang'), by definition, are always encompassed by another language. All records of type 'extlang' MUST, therefore, contain a 'Prefix' field at the time of registration. This 'Prefix' field can never be altered or removed, and requests to do so MUST be rejected. Variant subtags are usually registered for use with a particular range of language tags, and variant subtags based on the terminology of the language to which they are apply are encouraged. For example, the subtag 'rozaj' (Resian) is intended for use with language tags that start with the primary language subtag "sl" (Slovenian), since Resian is a dialect of Slovenian. Thus, the subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj" or "sl-IT-rozaj". This information is stored in the 'Prefix' field in the registry. Variant
registration requests SHOULD include at least one 'Prefix' field in the registration form. Requests to assign an additional record of a given type with an existing subtag value MUST be rejected. For example, the variant subtag 'rozaj' already exists in the registry, so adding a second record of type 'variant' with the subtag 'rozaj' is prohibited. The 'Prefix' field for a given registered variant subtag exists in the IANA registry as a guide to usage. Additional 'Prefix' fields MAY be added by filing an additional registration form. In that form, the "Any other relevant information:" field MUST indicate that it is the addition of a prefix. Requests to add a 'Prefix' field to a variant subtag that imply a different semantic meaning SHOULD be rejected. For example, a request to add the prefix "de" to the subtag '1994' so that the tag "de-1994" represented some German dialect or orthographic form would be rejected. The '1994' subtag represents a particular Slovenian orthography, and the additional registration would change or blur the semantic meaning assigned to the subtag. A separate subtag SHOULD be proposed instead. Requests to add a 'Prefix' to a variant subtag that has no current 'Prefix' field MUST be rejected. Variants are registered with no prefix because they are potentially useful with many or even all languages. Adding one or more 'Prefix' fields would be potentially harmful to the use of the variant, since it dramatically reduces the scope of the subtag (which is not allowed under the stability rules (Section 3.4) as opposed to broadening the scope of the subtag, which is what the addition of a 'Prefix' normally does. An example of such a "no-prefix" variant is the subtag 'fonipa', which represents the International Phonetic Alphabet, a scheme that can be used to transcribe many languages. The 'Description' fields provided in the request MUST contain at least one description written or transcribed into the Latin script; the request MAY also include additional 'Description' fields in any script or language. The 'Description' field is used for identification purposes and doesn't necessarily represent the actual native name of the language or variation. It also doesn't have to be in any particular language, but SHOULD be both suitable and sufficient to identify the item in the record. The Language Subtag Reviewer will check and edit any proposed 'Description' fields so as to ensure uniqueness and prevent collisions with 'Description' fields in other records of the same type. If this occurs in an independent registration request, the Language Subtag Reviewer MUST resubmit the record to <ietf-languages@iana.org>, treating it as a modification of
a request due to discussion, as described in Section 3.5, unless the request's sole purpose is to introduce a duplicate 'Description' field, in which case the request SHALL be rejected. The 'Description' field is not guaranteed to be stable. Corrections or clarifications of intent are examples of possible changes. Attempts to provide translations or transcriptions of entries in the registry (which, by definition, provide no new information) are unlikely to be approved. Soon after the two-week review period has passed, the Language Subtag Reviewer MUST take one of the following actions: o Explicitly accept the request and forward the form containing the record to be inserted or modified to <iana@iana.org> according to the procedure described in Section 3.3. o Explicitly reject the request because of significant objections raised on the list or due to problems with constraints in this document (which MUST be explicitly cited). o Extend the review period by granting an additional two-week increment to permit further discussion. After each two-week increment, the Language Subtag Reviewer MUST indicate on the list whether the registration has been accepted, rejected, or extended. Note that the Language Subtag Reviewer MAY raise objections on the list if he or she so desires. The important thing is that the objection MUST be made publicly. Sometimes the request needs to be modified as a result of discussion during the review period or due to requirements in this document. The applicant, Language Subtag Reviewer, or others MAY submit a modified version of the completed registration form, which will be considered in lieu of the original request with the explicit approval of the applicant. Such changes do not restart the two-week discussion period, although an application containing the final record submitted to IANA MUST appear on the list at least one week prior to the Language Subtag Reviewer forwarding the record to IANA. The applicant MAY modify a rejected application with more appropriate or additional information and submit it again; this starts a new two- week comment period. Registrations initiated due to the provisions of Section 3.3 or Section 3.4 SHALL NOT be rejected altogether (since they have to ultimately appear in the registry) and SHOULD be completed as quickly as possible. The review process allows list members to comment on the specific information in the form and the record it contains and
thus help ensure that it is correct and consistent. The Language Subtag Reviewer MAY reject a specific version of the form, but MUST propose a suitable replacement, extending the review period as described above, until the form is in a format worthy of the reviewer's approval and meets with rough consensus of the list. Decisions made by the Language Subtag Reviewer MAY be appealed to the IESG [RFC2028] under the same rules as other IETF decisions [RFC2026]. This includes a decision to extend the review period or the failure to announce a decision in a clear and timely manner. The approved records appear in the Language Subtag Registry. The approved registration forms are available online from http://www.iana.org. Updates or changes to existing records follow the same procedure as new registrations. The Language Subtag Reviewer decides whether there is consensus to update the registration following the two-week review period; normally, objections by the original registrant will carry extra weight in forming such a consensus. Registrations are permanent and stable. Once registered, subtags will not be removed from the registry and will remain a valid way in which to specify a specific language or variant. Note: The purpose of the "Reference to published description" section in the registration form is to aid in verifying whether a language is registered or to which language or language variation a particular subtag refers. In most cases, reference to an authoritative grammar or dictionary of that language will be useful; in cases where no such work exists, other well-known works describing that language or in that language MAY be appropriate. The Language Subtag Reviewer decides what constitutes "good enough" reference material. This requirement is not intended to exclude particular languages or dialects due to the size of the speaker population or lack of a standardized orthography. Minority languages will be considered equally on their own merits.
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