draft-ietf-ltru-registry-02.txt   draft-ietf-ltru-registry-03.txt 
Network Working Group A. Phillips, Ed. Network Working Group A. Phillips, Ed.
Internet-Draft Quest Software Internet-Draft Quest Software
Expires: November 20, 2005 M. Davis, Ed. Expires: December 4, 2005 M. Davis, Ed.
IBM IBM
May 19, 2005 June 02, 2005
Tags for Identifying Languages Tags for Identifying Languages
draft-ietf-ltru-registry-02 draft-ietf-ltru-registry-03
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document describes the structure, content, construction, and This document describes the structure, content, construction, and
semantics of language tags for use in cases where it is desirable to semantics of language tags for use in cases where it is desirable to
indicate the language used in an information object. It also indicate the language used in an information object. It also
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creation of user defined extensions for private interchange. This creation of user defined extensions for private interchange. This
document obsoletes RFC 3066 (which replaced RFC 1766). document obsoletes RFC 3066 (which replaced RFC 1766).
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 Length Considerations . . . . . . . . . . . . . . . . 6 2.1.1 Length Considerations . . . . . . . . . . . . . . . . 6
2.2 Language Subtag Sources and Interpretation . . . . . . . . 7 2.2 Language Subtag Sources and Interpretation . . . . . . . . 7
2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 8 2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 9
2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 10 2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 11
2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 10 2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 11
2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 11 2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 12
2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 12 2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 13
2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 13 2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 14
2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 14 2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 15
2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 15 2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 16
2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 15 2.2.9 Classes of Conformance . . . . . . . . . . . . . . . . 16
3. Registry Format and Maintenance . . . . . . . . . . . . . . . 17 3. Registry Format and Maintenance . . . . . . . . . . . . . . . 18
3.1 Format of the IANA Language Subtag Registry . . . . . . . 17 3.1 Format of the IANA Language Subtag Registry . . . . . . . 18
3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 21 3.2 Maintenance of the Registry . . . . . . . . . . . . . . . 23
3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 23 3.3 Stability of IANA Registry Entries . . . . . . . . . . . . 24
3.4 Registration Procedure for Subtags . . . . . . . . . . . . 26 3.4 Registration Procedure for Subtags . . . . . . . . . . . . 27
3.5 Possibilities for Registration . . . . . . . . . . . . . . 29 3.5 Possibilities for Registration . . . . . . . . . . . . . . 30
3.6 Extensions and Extensions Namespace . . . . . . . . . . . 31 3.6 Extensions and Extensions Namespace . . . . . . . . . . . 32
3.7 Conversion of the RFC 3066 Language Tag Registry . . . . . 34 3.7 Initialization of the Registry . . . . . . . . . . . . . . 35
4. Formation and Processing of Language Tags . . . . . . . . . . 37 4. Formation and Processing of Language Tags . . . . . . . . . . 38
4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 37 4.1 Choice of Language Tag . . . . . . . . . . . . . . . . . . 38
4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 39 4.2 Meaning of the Language Tag . . . . . . . . . . . . . . . 40
4.3 Canonicalization of Language Tags . . . . . . . . . . . . 40 4.3 Canonicalization of Language Tags . . . . . . . . . . . . 41
4.4 Considerations for Private Use Subtags . . . . . . . . . . 41 4.4 Considerations for Private Use Subtags . . . . . . . . . . 43
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
6. Security Considerations . . . . . . . . . . . . . . . . . . . 44 6. Security Considerations . . . . . . . . . . . . . . . . . . . 45
7. Character Set Considerations . . . . . . . . . . . . . . . . . 45 7. Character Set Considerations . . . . . . . . . . . . . . . . . 46
8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 46 8. Changes from RFC 3066 . . . . . . . . . . . . . . . . . . . . 47
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 50 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.1 Normative References . . . . . . . . . . . . . . . . . . . 50 9.1 Normative References . . . . . . . . . . . . . . . . . . . 51
9.2 Informative References . . . . . . . . . . . . . . . . . . 51 9.2 Informative References . . . . . . . . . . . . . . . . . . 52
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 52 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 53
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54
B. Examples of Language Tags (Informative) . . . . . . . . . . . 54 B. Examples of Language Tags (Informative) . . . . . . . . . . . 55
C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 57 C. Example Registry . . . . . . . . . . . . . . . . . . . . . . . 58
Intellectual Property and Copyright Statements . . . . . . . . 61 Intellectual Property and Copyright Statements . . . . . . . . 62
1. Introduction 1. Introduction
Human beings on our planet have, past and present, used a number of Human beings on our planet have, past and present, used a number of
languages. There are many reasons why one would want to identify the languages. There are many reasons why one would want to identify the
language used when presenting or requesting information. language used when presenting or requesting information.
Information about a user's language preferences commonly needs to be Information about a user's language preferences commonly needs to be
identified so that appropriate processing can be applied. For identified so that appropriate processing can be applied. For
example, the user's language preferences in a browser can be used to example, the user's language preferences in a browser can be used to
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and content, so that each type of subtag can be recognized solely by and content, so that each type of subtag can be recognized solely by
these features. This makes it possible to construct a parser that these features. This makes it possible to construct a parser that
can extract and assign some semantic information to the subtags, even can extract and assign some semantic information to the subtags, even
if specific subtag values are not recognized. Thus a parser need not if specific subtag values are not recognized. Thus a parser need not
have an up-to-date copy of the registered subtag values to perform have an up-to-date copy of the registered subtag values to perform
most searching and matching operations. most searching and matching operations.
The syntax of this tag in ABNF [7] is: The syntax of this tag in ABNF [7] is:
Language-Tag = (lang Language-Tag = (lang
*("-" extlang) *3("-" extlang)
["-" script] ["-" script]
["-" region] ["-" region]
*("-" variant) *("-" variant)
*("-" extension) *("-" extension)
["-" privateuse]) ["-" privateuse])
/ privateuse ; private-use tag / privateuse ; private-use tag
/ grandfathered ; grandfathered registrations / grandfathered ; grandfathered registrations
lang = 2*3ALPHA ; shortest ISO 639 code lang = 2*4ALPHA ; shortest ISO 639 code
/ registered-lang / registered-lang
extlang = 3ALPHA ; reserved for future use extlang = 3ALPHA ; reserved for future use
script = 4ALPHA ; ISO 15924 code script = 4ALPHA ; ISO 15924 code
region = 2ALPHA ; ISO 3166 code region = 2ALPHA ; ISO 3166 code
/ 3DIGIT ; UN country number / 3DIGIT ; UN country number
variant = 5*8alphanum ; registered variants variant = 5*8alphanum ; registered variants
/ ( DIGIT 3alphanum ) / ( DIGIT 3alphanum )
extension = singleton 1*("-" (2*8alphanum)) extension = singleton 1*("-" (2*8alphanum))
privateuse = ("x"/"X") 1*("-" (1*8alphanum)) privateuse = ("x"/"X") 1*("-" (1*8alphanum))
singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT singleton = %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT
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Although neither the ABNF nor other guidelines in this document Although neither the ABNF nor other guidelines in this document
provide a fixed upper limit on the number of subtags in a Language provide a fixed upper limit on the number of subtags in a Language
Tag (and thus the upper bound on the size of a tag) and it is Tag (and thus the upper bound on the size of a tag) and it is
possible to envision quite long and complex subtag sequences, in possible to envision quite long and complex subtag sequences, in
practice these are rare because additional granularity in tags seldom practice these are rare because additional granularity in tags seldom
adds useful distinguishing information and because longer, more adds useful distinguishing information and because longer, more
granular tags interefere with the meaning, understanding, and granular tags interefere with the meaning, understanding, and
processing of language tags. processing of language tags.
A conformant implementation MAY refuse to support the storage of
language tags which exceed a specified length. For an example, see
[RFC 2231] [22]. Any such limitation SHOULD be clearly documented,
and such documentation SHOULD include the disposition of any longer
tags (for example, whether an error value is generated or the
language tag is truncated). If truncation is permitted it MUST NOT
permit a subtag to be divided. Implementations that restrict storage
should consider removing extensions before processing. A protocol
that allows tags to be truncated at an arbitrary limit, without
giving any indication of what that limit is, has the potential for
causing harm by changing the meaning of tags in substantial ways.
In particular, variant subtags SHOULD be used only with their In particular, variant subtags SHOULD be used only with their
recommended prefix. In practice, this limits most tags to a sequence recommended prefix. In practice, this limits most tags to a sequence
of four subtags, and thus a maximum length of 26 characters of four subtags, and thus a maximum length of 26 characters
(excluding any extensions or private use sequences). This is because (excluding any extensions or private use sequences). This is because
subtags are limited to a length of eight characters and the extlang, subtags are limited to a length of eight characters and the extlang,
script, and region subtags are limited to even fewer characters. See script, and region subtags are limited to even fewer characters. See
Section 4.1 for more information on selecting the most appropriate Section 4.1 for more information on selecting the most appropriate
Language Tag. Language Tag.
A conformant implementation MAY refuse to support the storage of Longer tags are possible. The longest tags (excluding extensions)
language tags which exceed a specified length. For an example, see could have a length of up to 62 characters, as shown below.
[RFC 2231] [22]. Any such limitation MUST be clearly documented, and Implementations MUST be able to handle tags of this length without
such documentation SHOULD include the disposition of any longer tags truncation. Support for tags of up to 64 characters is RECOMMENDED.
(for example, whether an error value is generated or the language tag Implementations MAY support longer tags.
is truncated). If truncation is permitted it MUST NOT permit a
subtag to be divided. Here is how the 62-character length of the longest practical tag
(excluding extensions) is derived:
language = 3
extlang1 = 4
extlang2 = 4 (unlikely: needs prefix="language-extlang1")
extlang3 = 4 (extremely unlikely)
script = 5
region = 4 (UN M.49)
variant1 = 9
variant2 = 9 (unlikely: needs prefix="language-variant1")
private use 1 = 11 ("-x-" + subtag)
private use 2 = 9
total = 62 characters
Figure 2: Derviation of the Longest Tag
2.2 Language Subtag Sources and Interpretation 2.2 Language Subtag Sources and Interpretation
The namespace of language tags and their subtags is administered by The namespace of language tags and their subtags is administered by
the Internet Assigned Numbers Authority (IANA) [13] according to the the Internet Assigned Numbers Authority (IANA) [13] according to the
rules in Section 5 of this document. The registry maintained by IANA rules in Section 5 of this document. The registry maintained by IANA
is the source for valid subtags: other standards referenced in this is the source for valid subtags: other standards referenced in this
section provide the source material for that registry. section provide the source material for that registry.
Terminology in this section: Terminology in this section:
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for more information on private use subtags. for more information on private use subtags.
4. All four character language subtags are reserved for possible 4. All four character language subtags are reserved for possible
future standardization. future standardization.
5. All language subtags of 5 to 8 characters in length in the IANA 5. All language subtags of 5 to 8 characters in length in the IANA
registry were defined via the registration process in Section 3.4 registry were defined via the registration process in Section 3.4
and MAY be used to form the primary language subtag. At the time and MAY be used to form the primary language subtag. At the time
this document was created, there were no examples of this kind of this document was created, there were no examples of this kind of
subtag and future registrations of this type will be discouraged: subtag and future registrations of this type will be discouraged:
primary languages are STRONGLY RECOMMENDED for registration with primary languages are strongly RECOMMENDED for registration with
ISO 639 and proposals rejected by ISO 639/RA will be closely ISO 639 and proposals rejected by ISO 639/RA will be closely
scrutinized before they are registered with IANA. scrutinized before they are registered with IANA.
6. The single character subtag 'x' as the primary subtag indicates 6. The single character subtag 'x' as the primary subtag indicates
that the language tag consists solely of subtags whose meaning is that the language tag consists solely of subtags whose meaning is
defined by private agreement. For example, in the tag "x-fr-CH", defined by private agreement. For example, in the tag "x-fr-CH",
the subtags 'fr' and 'CH' should not be taken to represent the the subtags 'fr' and 'CH' should not be taken to represent the
French language or the country of Switzerland (or any other value French language or the country of Switzerland (or any other value
in the IANA registry) unless there is a private agreement in in the IANA registry) unless there is a private agreement in
place to do so. See Section 4.4. place to do so. See Section 4.4.
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The following rules apply to the extended language subtags: The following rules apply to the extended language subtags:
1. Three letter subtags immediately following the primary subtag are 1. Three letter subtags immediately following the primary subtag are
reserved for future standardization, anticipating work that is reserved for future standardization, anticipating work that is
currently under way on ISO 639. currently under way on ISO 639.
2. Extended language subtags MUST follow the primary subtag and 2. Extended language subtags MUST follow the primary subtag and
precede any other subtags. precede any other subtags.
3. There MAY be any additional number of extended language subtags. 3. There MAY be up to three extended language subtags.
4. Extended language subtags will not be registered except by 4. Extended language subtags will not be registered except by
revision of this document. revision of this document.
5. Extended language subtags MUST NOT be used to form language tags 5. Extended language subtags MUST NOT be used to form language tags
except by revision of this document. except by revision of this document.
Extended language subtag records, once they appear in the registry,
MUST include exactly one 'Prefix' field indicating an appropriate
language subtag or sequence of subtags that MUST always appear as a
prefix to the extended language subtag.
Example: In a future revision or update of this document, the tag Example: In a future revision or update of this document, the tag
"zh-gan" (registered under RFC 3066) might become a valid non- "zh-gan" (registered under RFC 3066) might become a valid non-
grandfathered (that is, redundant) tag in which the subtag 'gan' grandfathered (that is, redundant) tag in which the subtag 'gan'
might represent the Chinese dialect 'Gan'. might represent the Chinese dialect 'Gan'.
2.2.3 Script Subtag 2.2.3 Script Subtag
The following rules apply to the script subtags: The following rules apply to the script subtags:
1. All four character subtags were defined according to ISO 15924 1. All four character subtags were defined according to ISO 15924
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language tags. In order to distinguish variants from other types language tags. In order to distinguish variants from other types
of subtags, registrations must meet the following length and of subtags, registrations must meet the following length and
content restrictions: content restrictions:
1. Variant subtags that begin with a letter (a-z, A-Z) MUST be 1. Variant subtags that begin with a letter (a-z, A-Z) MUST be
at least five characters long. at least five characters long.
2. Variant subtags that begin with a digit (0-9) MUST be at 2. Variant subtags that begin with a digit (0-9) MUST be at
least four characters long. least four characters long.
Variant subtag records in the language subtag registry may include
one or more 'Prefix' fields, which indicates the language tag or tags
that would make a suitable prefix (with other subtags, as
appropriate) in forming a language tag with the variant. For
example, the subtag 'scouse' has a Prefix of "en", making it suitable
to form language tags such as "en-scouse" and "en-GB-scouse", but not
suitable for use in a tag such as "zh-scouse" or "it-GB-scouse".
"en-scouse" represents the Scouse dialect of English. "en-scouse" represents the Scouse dialect of English.
"de-CH-1996" represents German as used in Switzerland and as written "de-CH-1996" represents German as used in Switzerland and as written
using the spelling reform beginning in the year 1996 C.E. using the spelling reform beginning in the year 1996 C.E.
Most variants that share a prefix are mutually exclusive. For
example, the German orthographic variantions '1996' and '1901' should
not be used in the same tag, as they represent the dates of different
spelling reforms. A variant that may be used in combination with
another variant should include a 'Prefix' field in its registry
record that lists that other variant. For example, if another German
variant 'example' were created that made sense to use with '1996',
then 'example' should include two Prefix fields: "de" and "de-1996".
2.2.6 Extension Subtags 2.2.6 Extension Subtags
The following rules apply to extensions: The following rules apply to extensions:
1. Extension subtags are separated from the other subtags defined 1. Extension subtags are separated from the other subtags defined
in this document by a single-letter subtag ("singleton"). The in this document by a single-letter subtag ("singleton"). The
singleton MUST be one allocated to a registration authority via singleton MUST be one allocated to a registration authority via
the mechanism described in Section 3.6 and cannot be the letter the mechanism described in Section 3.6 and cannot be the letter
'x', which is reserved for private-use subtag sequences. 'x', which is reserved for private-use subtag sequences.
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language, script, region, and variant subtags consist of valid language, script, region, and variant subtags consist of valid
codes for use in language tags according to the IANA registry as codes for use in language tags according to the IANA registry as
of the particular date specified by the implementation. of the particular date specified by the implementation.
o Specify which, if any, extension RFCs as defined in Section 3.6 o Specify which, if any, extension RFCs as defined in Section 3.6
are supported, including version, revision, and date. are supported, including version, revision, and date.
o For any such extensions supported, check that all subtags used in o For any such extensions supported, check that all subtags used in
that extension are valid. that extension are valid.
o If the processor generates tags, it MUST do so in canonical form, o For variant and extended language subtags, if the registry
including any supported extensions, as defined in Section 4.3. contains one or more 'Prefix' fields for that subtag, check that
the tag matches at least one prefix. The tag matches if all the
subtags in the 'Prefix' also appear in the tag. For example, the
prefix "es-CO" matches the tag "es-Latn-CO-x-private" because both
the 'es' language subtag and 'CO' region subtag appear in the tag.
3. Registry Format and Maintenance 3. Registry Format and Maintenance
This section defines the Language Subtag Registry and the maintenance This section defines the Language Subtag Registry and the maintenance
and update procedures associated with it. and update procedures associated with it.
The language subtag registry will be maintained so that, except for The language subtag registry will be maintained so that, except for
extension subtags, it is possible to validate all of the subtags that 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 appear in a language tag under the provisions of this document or its
revisions or successors. In addition, the meaning of the various revisions or successors. In addition, the meaning of the various
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of the character's code point in ISO/IEC 10646 [6] followed by a of the character's code point in ISO/IEC 10646 [6] followed by a
closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would
be represented by the sequence "€". Note that the hexadecimal be represented by the sequence "€". Note that the hexadecimal
notation may have between two and six digits. notation may have between two and six digits.
All fields whose field-body contains a date value use the "full-date" All fields whose field-body contains a date value use the "full-date"
format specified in RFC 3339 [14]. For example: "2004-06-28" format specified in RFC 3339 [14]. For example: "2004-06-28"
represents June 28, 2004 in the Gregorian calendar. represents June 28, 2004 in the Gregorian calendar.
The first record in the file contains the single field whose field- The first record in the file contains the single field whose field-
name is "File-Date" and whose field-body contains the last name is "File-Date". The field-body of this record contains the last
modification date of the registry: modification date of this copy of the registry, making it possible to
compare different versions of the registry. The registry on the IANA
website is the most current. Versions with an older date than that
one are not up-to-date.
File-Date: 2004-06-28 File-Date: 2004-06-28
%% %%
Subsequent records represent subtags in the registry. Each of the Subsequent records represent subtags in the registry. Each of the
fields in each record MUST occur no more than once, unless otherwise fields in each record MUST occur no more than once, unless otherwise
noted below. Each record MUST contain the following fields: noted below. Each record MUST contain the following fields:
o 'Type' o 'Type'
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ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate ISO 15924, ISO 3166 or UN M.49 codes are intended only to indicate
the meaning of that identifier as defined in the source standard at the meaning of that identifier as defined in the source standard at
the time it was added to the registry. The description does not the time it was added to the registry. The description does not
replace the content of the source standard itself. The descriptions replace the content of the source standard itself. The descriptions
are not intended to be the English localized names for the subtags. are not intended to be the English localized names for the subtags.
Localization or translation of language tag and subtag descriptions Localization or translation of language tag and subtag descriptions
is out of scope of this document. is out of scope of this document.
Each record MAY also contain the following fields: Each record MAY also contain the following fields:
o Canonical o Preferred-Value
* For fields of type 'language', 'extlang', 'script', 'region', * For fields of type 'language', 'extlang', 'script', 'region',
and 'variant', a canonical mapping of this record to a subtag and 'variant', 'Preferred-Value' contains a subtag of the same
record of the same 'Type'. 'Type' which is preferred for forming the language tag.
* For fields of type 'grandfathered' and 'redundant', a canonical * For fields of type 'grandfathered' and 'redundant', a canonical
mapping to a complete language tag. mapping to a complete language tag.
o Deprecated o Deprecated
* Deprecated's field-value contains the date the record was * Deprecated's field-value contains the date the record was
deprecated. deprecated.
o Recommended-Prefix o Prefix
* Recommended-Prefix's field-value contains a language tag with * Prefix's field-value contains a language tag with which this
which this subtag may be used to form a new language tag, subtag may be used to form a new language tag, perhaps with
perhaps with other subtags as well. This field MUST only other subtags as well. This field MUST only appear in records
appear in records whose 'Type' field-value is 'variant' or whose 'Type' field-value is 'variant' or 'extlang'. For
'extlang'. For example, the 'Recommended-Prefix' for the example, the 'Prefix' for the variant 'scouse' is 'en', meaning
variant 'scouse' is 'en', meaning that the tags "en-scouse" and that the tags "en-scouse" and "en-GB-scouse" might be
"en-GB-scouse" might be appropriate while the tag "is-scouse" appropriate while the tag "is-scouse" is not.
is not.
o Comments o Comments
* Comments contains additional information about the subtag, as * Comments contains additional information about the subtag, as
deemed appropriate for understanding the registry and deemed appropriate for understanding the registry and
implementing language tags using the subtag or tag. implementing language tags using the subtag or tag.
o Suppress-Script o Suppress-Script
* Suppress-Script contains a script subtag that SHOULD NOT be * Suppress-Script contains a script subtag that SHOULD NOT be
used to form language tags with the associated primary language used to form language tags with the associated primary language
subtag. This field MUST only appear in records whose 'Type' subtag. This field MUST only appear in records whose 'Type'
field-value is 'language'. See Section 4.1. field-value is 'language'. See Section 4.1.
The field 'Canonical' SHALL NOT be added to any record already in the
registry. The field 'Canonical' SHALL NOT be modified except for
records of type "grandfathered": therefore a subtag whose record
contains no canonical mapping when the record is created is a
canonical form and will remain so.
The 'Canonical' field in records of type "grandfathered" and
"redundant" contains whole language tags that are STRONGLY
RECOMMENDED for use in place of the record's value. In many cases
the mappings were created by deprecation of the tags during the
period before this document was adopted. For example, the tag "no-
nyn" was deprecated in favor of the ISO 639-1 defined language code
'nn'.
Note that a record that has a 'Canonical' field MUST have a
'Deprecated' field also (although the converse is not true).
The field 'Deprecated' MAY be added to any record via the maintenance The field 'Deprecated' MAY be added to any record via the maintenance
process described in Section 3.2 or via the registration process process described in Section 3.2 or via the registration process
described in Section 3.4. Usually the addition of a 'Deprecated' described in Section 3.4. Usually the addition of a 'Deprecated'
field is due to the action of one of the standards bodies, such as field is due to the action of one of the standards bodies, such as
ISO 3166, withdrawing a code. In some historical cases it may not ISO 3166, withdrawing a code. In some historical cases it may not
have been possible to reconstruct the original deprecation date. have been possible to reconstruct the original deprecation date.
For these cases, an approximate date appears in the registry. For these cases, an approximate date appears in the registry.
Although valid in language tags, subtags and tags with a 'Deprecated' Although valid in language tags, subtags and tags with a 'Deprecated'
field are deprecated and validating processors SHOULD NOT generate field are deprecated and validating processors SHOULD NOT generate
these subtags. Note that a record that contains a 'Deprecated' field these subtags. Note that a record that contains a 'Deprecated' field
and no corresponding 'Canonical' field has no replacement mapping. and no corresponding 'Preferred-Value' field has no replacement
mapping.
The field 'Recommended-Prefix' MAY appear more than once per record. Thie field 'Preferred-Value' contains a mapping between the record in
Additional fields of this type MAY be added to a record via the which it appears and a tag or subtag which should be preferred when
registration process. The field-value of of this field consists of a selected language tags. These values form three groups:
language tag that is RECOMMENDED for use as a prefix for this subtag.
For example, the variant subtag 'scouse' has a recommended prefix of
"en". This means that tags starting with the prefix "en-" are most
appropriate with this subtag, so "en-Latn-scouse" and "en-GB-scouse"
are both acceptable, while the tag "fr-scouse" is probably an
inappropriate choice.
The field of type Recommended-Prefix MUST NOT be removed from any ISO 639 language codes which were later withdrawn in favor of
record. The field-value for this type of field MUST NOT be modified. other codes. These values are mostly a historical curiosity.
ISO 3166 region codes which have been withdrawn in favor of a new
code. This sometimes happens when a country changes its name or
administration in such a way that warrents a new region code.
Tags grandfathered from RFC 3066. In many cases these tags have
become obsolete because the values they represent were later
encoded by ISO 639.
Records that contain a 'Preferred-Value' field MUST also have a
'Deprecated' field. This field contains a date of deprecation. Thus
a language tag processor can use the registry to construct the valid,
non-deprecated set of subtags for a given date. In addition, for any
given tag, a processor can construct the set of valid language tags
that correspond to that tag for all dates up to the date of the
registry. The ability to do these mappings may be beneficial to
applications that are matching, selecting, for filtering content
based on its language tags.
It should be noted that 'Preferred-Value' mappings in records of type
'region' may not represent exactly the same meaning as the original
value. There are many reasons that a country code may be changed and
the effect this has on the formation of language tags may depend on
the nature of the change in question.
In particular, the 'Preferred-Value' field does not imply that
content formerly tagged with one tag should be retagged.
The field 'Preferred-Value' MUST NOT be modified once created in the
registry. The field MAY be added to records of type "grandfathered"
and "region" according to the rules in Section 3.2. Otherwise the
field MUST NOT be added to any record already in the registry.
The 'Preferred-Value' field in records of type "grandfathered" and
"redundant" contains whole language tags that are strongly
RECOMMENDED for use in place of the record's value. In many cases
the mappings were created by deprecation of the tags during the
period before this document was adopted. For example, the tag "no-
nyn" was deprecated in favor of the ISO 639-1 defined language code
'nn'.
Records of type 'variant' MAY have more than one field of type
'Prefix'. Additional fields of this type MAY be added to a 'variant'
record via the registration process.
Records of type 'extlang' MUST have _exactly_ one 'Prefix' field.
The field-value of the 'Prefix' field consists of a language tag
whose subtags are appropriate to use with this subtag. For example,
the variant subtag 'scouse' has a recommended prefix of "en". This
means that tags starting with the prefix "en-" are most appropriate
with this subtag, so "en-Latn-scouse" and "en-GB-scouse" are both
acceptable, while the tag "fr-scouse" is an inappropriate choice.
The field of type 'Prefix' MUST NOT be removed from any record. The
field-value for this type of field MUST NOT be modified.
The field 'Comments' MAY appear more than once per record. This The field 'Comments' MAY appear more than once per record. This
field MAY be inserted or changed via the registration process and no field MAY be inserted or changed via the registration process and no
guarantee of stability is provided. The content of this field is not guarantee of stability is provided. The content of this field is not
restricted, except by the need to register the information, the restricted, except by the need to register the information, the
suitability of the request, and by reasonable practical size suitability of the request, and by reasonable practical size
limitations. Long screeds about a particular subtag are frowned limitations. Long screeds about a particular subtag are frowned
upon. upon.
The field 'Suppress-Script' MUST only appear in records whose 'Type' The field 'Suppress-Script' MUST only appear in records whose 'Type'
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helps ensure greater compatibility between the language tags helps ensure greater compatibility between the language tags
generated according to the rules in this document and language tags generated according to the rules in this document and language tags
and tag processors or consumers based on RFC 3066. For example, and tag processors or consumers based on RFC 3066. For example,
virtually all Icelandic documents are written in the Latin script, virtually all Icelandic documents are written in the Latin script,
making the subtag 'Latn' redundant in the tag "is-Latn". making the subtag 'Latn' redundant in the tag "is-Latn".
For examples of registry entries and their format, see Appendix C. For examples of registry entries and their format, see Appendix C.
3.2 Maintenance of the Registry 3.2 Maintenance of the Registry
Maintenance of the registry requires that as new codes are assigned Maintenance of the registry requires that as codes are assigned or
by ISO 639, ISO 15924, and ISO 3166, the Language Subtag Reviewer withdrawn by ISO 639, ISO 15924, and ISO 3166, the Language Subtag
will evaluate each assignment, determine whether it conflicts with Reviewer will evaluate each change, determine whether it conflicts
existing registry entries, and submit the information to IANA for with existing registry entries, and submit the information to IANA
inclusion in the registry. If an assignment takes place and the for inclusion in the registry. If an change takes place and the
Language Subtag Reviewer does not do this in a timely manner, then Language Subtag Reviewer does not do this in a timely manner, then
any interested party may use the procedure in Section 3.4 to register any interested party may use the procedure in Section 3.4 to register
the appropriate update. the appropriate update.
Note: The redundant and grandfathered entries together are the Note: The redundant and grandfathered entries together are the
complete list of tags registered under RFC 3066 [23]. The redundant complete list of tags registered under RFC 3066 [23]. The redundant
tags are those that can now be formed using the subtags defined in tags are those that can now be formed using the subtags defined in
the registry together with the rules of Section 2.2. The the registry together with the rules of Section 2.2. The
grandfathered entries are those that can never be legal under those grandfathered entries are those that can never be legal under those
same provisions. The items in both lists are permanent and stable, same provisions.
although grandfathered items may be deprecated over time. Refer to
Section 3.7 for more information. The set of redundant and grandfathered tags is permanent and stable:
no new entries will be added and none of the entries will be removed.
Records of type 'grandfathered' may have their type converted to
'redundant': see Section 3.7 for more information.
RFC 3066 tags that were deprecated prior to the adoption of this RFC 3066 tags that were deprecated prior to the adoption of this
document are part of the list of grandfathered tags and their document are part of the list of grandfathered tags and their
component subtags were not included as registered variants (although component subtags were not included as registered variants (although
they remain eligible for registration). For example, the tag "art- they remain eligible for registration). For example, the tag "art-
lojban" was deprecated in favor of the language subtag 'jbo'. lojban" was deprecated in favor of the language subtag 'jbo'.
The Language Subtag Reviewer MUST ensure that new subtags meet the The Language Subtag Reviewer MUST ensure that new subtags meet the
requirements in Section 4.1 or submit an appropriate alternate subtag requirements in Section 4.1 or submit an appropriate alternate subtag
as described in that section. If a change or addition to the as described in that section. If a change or addition to the
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in the following example: in the following example:
LANGUAGE SUBTAG MODIFICATION LANGUAGE SUBTAG MODIFICATION
File-Date: 2005-01-02 File-Date: 2005-01-02
%% %%
Type: variant Type: variant
Subtag: nedis Subtag: nedis
Description: Natisone dialect Description: Natisone dialect
Description: Nadiza dialect Description: Nadiza dialect
Added: 2003-10-09 Added: 2003-10-09
Recommended-Prefix: sl Prefix: sl
Comments: This is a comment shown Comments: This is a comment shown
as an example. as an example.
%% %%
Figure 4 Figure 5
Whenever an entry is created or modified in the registry, the 'File- Whenever an entry is created or modified in the registry, the 'File-
Date' record at the start of the registry is updated to reflect the Date' record at the start of the registry is updated to reflect the
most recent modification date in the RFC 3339 [14] "full-date" most recent modification date in the RFC 3339 [14] "full-date"
format. format.
Values in the 'Subtag' field must be lowercase except as provided for Values in the 'Subtag' field must be lowercase except as provided for
in Section 3.1. in Section 3.1.
3.3 Stability of IANA Registry Entries 3.3 Stability of IANA Registry Entries
The stability of entries and their meaning in the registry is The stability of entries and their meaning in the registry is
critical to the long term stability of language tags. The rules in critical to the long term stability of language tags. The rules in
this section guarantee that a specific language tag's meaning is this section guarantee that a specific language tag's meaning is
stable over time and will not change and that the choice of language stable over time and will not change.
tag for specific content is also stable over time.
These rules specifically deal with how changes to codes (including These rules specifically deal with how changes to codes (including
withdrawal and deprecation of codes) maintained by ISO 639, ISO withdrawal and deprecation of codes) maintained by ISO 639, ISO
15924, ISO 3166, and UN M.49 are reflected in the IANA Language 15924, ISO 3166, and UN M.49 are reflected in the IANA Language
Subtag Registry. Assignments to the IANA Language Subtag Registry Subtag Registry. Assignments to the IANA Language Subtag Registry
MUST follow the following stability rules: MUST follow the following stability rules:
o Values in the fields 'Type', 'Subtag', 'Tag', 'Added' and o Values in the fields 'Type', 'Subtag', 'Tag', 'Added',
'Canonical' MUST NOT be changed and are guaranteed to be stable 'Deprecated' and 'Preferred-Value' MUST NOT be changed and are
over time. guaranteed to be stable over time.
o Values in the 'Description' field MUST NOT be changed in a way o Values in the 'Description' field MUST NOT be changed in a way
that would invalidate previously-existing tags. They may be that would invalidate previously-existing tags. They may be
broadened somewhat in scope, changed to add information, or broadened somewhat in scope, changed to add information, or
adapted to the most common modern usage. For example, countries adapted to the most common modern usage. For example, countries
occasionally change their official names: an historical example of occasionally change their official names: an historical example of
this would be "Upper Volta" changing to "Burkina Faso". this would be "Upper Volta" changing to "Burkina Faso".
o Values in the field 'Recommended-Prefix' MAY be added via the o Values in the field 'Prefix' MAY be added to records of type
registration process. 'variant' via the registration process.
o Values in the field 'Recommended-Prefix' MAY be modified, so long o Values in the field 'Prefix' MAY be modified, so long as the
as the modifications broaden the set of recommended prefixes. modifications broaden the set of recommended prefixes. That is, a
That is, a recommended prefix MAY be replaced by one of its own recommended prefix MAY be replaced by one of its own prefixes.
prefixes. For example, the prefix "en-US" could be replaced by For example, the prefix "en-US" could be replaced by "en", but not
"en", but not by the ranges "en-Latn", "fr", or "en-US-boont". by the ranges "en-Latn", "fr", or "en-US-boont".
o Values in the field 'Recommended-Prefix' MUST NOT be removed. o Values in the field 'Prefix' MUST NOT be removed.
o The field 'Comments' MAY be added, changed, modified, or removed o The field 'Comments' MAY be added, changed, modified, or removed
via the registration process or any of the processes or via the registration process or any of the processes or
considerations described in this section. considerations described in this section.
o The field 'Suppress-Script' MAY be added or removed via the o The field 'Suppress-Script' MAY be added or removed via the
registration process. registration process.
o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not
conflict with existing subtags of the associated type and whose conflict with existing subtags of the associated type and whose
meaning is not the same as an existing subtag of the same type are meaning is not the same as an existing subtag of the same type are
entered into the IANA registry as new records and their value is entered into the IANA registry as new records and their value is
canonical for the meaning assigned to them. canonical for the meaning assigned to them.
o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are
withdrawn by their respective maintenance or registration withdrawn by their respective maintenance or registration
authority remain valid in language tags. The registration process authority remain valid in language tags. A 'Deprecated' field
MAY be used to add a note indicating the withdrawal of the code by containing the date of withdrawl is added to the record. If a new
the respective standard. record of the same type is added that represents a replacement
value, then a 'Preferred-Value' field may also be added. The
o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that do not registration process MAY be used to add comments about the
conflict with existing subtags of the associated type but which withdrawal of the code by the respective standard.
represent the same meaning as an existing subtag of that type are
entered into the IANA registry as new records. The field
'canonical value' for that record MUST contain the existing subtag
of the same meaning
Example If ISO 3166 were to assign the code 'IM' to represent the
value "Isle of Man" (represented in the IANA registry by the UN
M.49 code '833'), '833' remains the canonical subtag and 'IM'
would be assigned '833' as a canonical value. This prevents
tags that are in canonical form from becoming non-canonical.
Example If the tag 'enochian' were registered as a primary * The region code 'TL' was assigned to the country 'Timor-Leste',
language subtag and ISO 639 subsequently assigned an alpha-3 replacing the code 'TP' (which was assigned to 'East Timor'
code to the same language, the new ISO 639 code would be when it was under administration by Portugal). The subtag 'TP'
entered into the IANA registry as a subtag with a canonical remains valid in language tags, but its record contains the a
mapping to 'enochian'. The new ISO code can be used, but it is 'Preferred-Value' of 'TL' and its field 'Deprecated' contains
not canonical. the date the new code was assigned ('2004-07-06').
o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict
with existing subtags of the associated type MUST NOT be entered with existing subtags of the associated type, including subtags
into the registry. The following additional considerations apply: that are deprecated, MUST NOT be entered into the registry. The
following additional considerations apply:
* For ISO 639 codes, if the newly assigned code's meaning is not * For ISO 639 codes, if the newly assigned code's meaning is not
represented by a subtag in the IANA registry, the Language represented by a subtag in the IANA registry, the Language
Subtag Reviewer, as described in Section 3.4, shall prepare a Subtag Reviewer, as described in Section 3.4, shall prepare a
proposal for entering in the IANA registry as soon as practical proposal for entering in the IANA registry as soon as practical
a registered language subtag as an alternate value for the new a registered language subtag as an alternate value for the new
code. The form of the registered language subtag will be at code. The form of the registered language subtag will be at
the discretion of the Language Subtag Reviewer and must conform the discretion of the Language Subtag Reviewer and must conform
to other restrictions on language subtags in this document. to other restrictions on language subtags in this document.
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Subtag Reviewer, as described in Section 3.4, shall prepare a Subtag Reviewer, as described in Section 3.4, shall prepare a
proposal for entering in the IANA registry as soon as practical proposal for entering in the IANA registry as soon as practical
a registered variant subtag as an alternate value for the new a registered variant subtag as an alternate value for the new
code. The form of the registered variant subtag will be at the code. The form of the registered variant subtag will be at the
discretion of the Language Subtag Reviewer and must conform to discretion of the Language Subtag Reviewer and must conform to
other restrictions on variant subtags in this document. other restrictions on variant subtags in this document.
* For ISO 3166 codes, if the newly assigned code's meaning is * For ISO 3166 codes, if the newly assigned code's meaning is
associated with the same UN M.49 code as another 'region' associated with the same UN M.49 code as another 'region'
subtag, then the existing region subtag remains as the subtag, then the existing region subtag remains as the
canonical entry for that region and no new entry is created. A preferred value for that region and no new entry is created. A
comment MAY be added to the existing region subtag indicating comment MAY be added to the existing region subtag indicating
the relationship to the new ISO 3166 code. the relationship to the new ISO 3166 code.
* For ISO 3166 codes, if the newly assigned code's meaning is * For ISO 3166 codes, if the newly assigned code's meaning is
associated with a UN M.49 code that is not represented by an associated with a UN M.49 code that is not represented by an
existing region subtag, then then the Language Subtag Reviewer, existing region subtag, then then the Language Subtag Reviewer,
as described in Section 3.4, shall prepare a proposal for as described in Section 3.4, shall prepare a proposal for
entering the appropriate numeric UN country code as an entry in entering the appropriate numeric UN country code as an entry in
the IANA registry. the IANA registry.
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shall prepare a proposal for entering in the IANA registry as shall prepare a proposal for entering in the IANA registry as
soon as practical a registered variant subtag as an alternate soon as practical a registered variant subtag as an alternate
value for the new code. The form of the registered variant value for the new code. The form of the registered variant
subtag will be at the discretion of the Language Subtag subtag will be at the discretion of the Language Subtag
Reviewer and must conform to other restrictions on variant Reviewer and must conform to other restrictions on variant
subtags in this document. This situation is very unlikely to subtags in this document. This situation is very unlikely to
ever occur. ever occur.
o Stability provisions apply to grandfathered tags with this o Stability provisions apply to grandfathered tags with this
exception: should all of the subtags in a grandfathered tag become exception: should all of the subtags in a grandfathered tag become
valid subtags in the IANA registry, then the grandfathered tag valid subtags in the IANA registry, then the field 'Type' in that
MUST be marked as redundant. Note that this will not affect record is changed from 'grandfathered' to 'redundant'. Note that
language tags that match the grandfathered tag, since these tags this will not affect language tags that match the grandfathered
will now match valid generative subtag sequences. For example, if tag, since these tags will now match valid generative subtag
the subtag 'gan' in the language tag "zh-gan" were to be sequences. For example, if the subtag 'gan' in the language tag
registered as an extended language subtag, then the grandfathered "zh-gan" were to be registered as an extended language subtag,
tag "zh-gan" would be deprecated (but existing content or then the grandfathered tag "zh-gan" would be deprecated (but
implementations that use "zh-gan" would remain valid). existing content or implementations that use "zh-gan" would remain
valid).
3.4 Registration Procedure for Subtags 3.4 Registration Procedure for Subtags
The procedure given here MUST be used by anyone who wants to use a The procedure given here MUST be used by anyone who wants to use a
subtag not currently in the IANA Language Subtag Registry. subtag not currently in the IANA Language Subtag Registry.
Only subtags of type 'language' and 'variant' will be considered for Only subtags of type 'language' and 'variant' will be considered for
independent registration of new subtags. Handling of subtags independent registration of new subtags. Handling of subtags
required for stability and subtags required to keep the registry required for stability and subtags required to keep the registry
synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within
the limits defined by this document are described in Section 3.2. the limits defined by this document are described in Section 3.2.
Stability provisions are described in Section 3.3. Stability provisions are described in Section 3.3.
This procedure MAY also be used to register or alter the information This procedure MAY also be used to register or alter the information
for the "Description", "Comments", "Deprecated", or "Recommended- for the "Description", "Comments", "Deprecated", or "Prefix" fields
Prefix" fields in a subtag's record as described in Figure 7. in a subtag's record as described in Figure 8. Changes to all other
Changes to all other fields in the IANA registry are NOT permitted. fields in the IANA registry are NOT permitted.
Registering a new subtag or requesting modifications to an existing Registering a new subtag or requesting modifications to an existing
tag or subtag starts with the requster filling out the registration tag or subtag starts with the requster filling out the registration
form reproduced below. Note that each response is not limited in form reproduced below. Note that each response is not limited in
size and should take the room necessary to adequately describe the size and should take the room necessary to adequately describe the
registration. The fields in the "Record Requested" section SHOULD registration. The fields in the "Record Requested" section SHOULD
follow the requirements in Section 3.1. follow the requirements in Section 3.1.
LANGUAGE SUBTAG REGISTRATION FORM LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester: 1. Name of requester:
2. E-mail address of requester: 2. E-mail address of requester:
3. Record Requested: 3. Record Requested:
Type: Type:
Subtag: Subtag:
Description: Description:
Recommended-Prefix: Prefix:
Canonical: Preferred-Value:
Deprecated: Deprecated:
Suppress-Script: Suppress-Script:
Comments: Comments:
4. Intended meaning of the subtag: 4. Intended meaning of the subtag:
5. Reference to published description 5. Reference to published description
of the language (book or article): of the language (book or article):
6. Any other relevant information: 6. Any other relevant information:
Figure 5 Figure 6
The subtag registration form MUST be sent to The subtag registration form MUST be sent to
<ietf-languages@iana.org> for a two week review period before it can <ietf-languages@iana.org> for a two week review period before it can
be submitted to IANA. (This is an open list. Requests to be added be submitted to IANA. (This is an open list. Requests to be added
should be sent to <ietf-languages-request@iana.org>.) should be sent to <ietf-languages-request@iana.org>.)
Variant subtags are generally registered for use with a particular Variant and extlang subtags are always registered for use with a
range of language tags. For example, the subtag 'scouse' is intended particular range of language tags. For example, the subtag 'scouse'
for use with language tags that start with the primary language is intended for use with language tags that start with the primary
subtag "en", since Scouse is a dialect of English. Thus the subtag language subtag "en", since Scouse is a dialect of English. Thus the
'scouse' could be included in tags such as "en-Latn-scouse" or "en- subtag 'scouse' could be included in tags such as "en-Latn-scouse" or
GB-scouse". This information is stored in the "Recommended-Prefix" "en-GB-scouse". This information is stored in the "Prefix" field in
field in the registry. Variant registration requests are REQUIRED to the registry. Variant registration requests are REQUIRED to include
include at least one "Recommended-Prefix" field in the registration at least one "Prefix" field in the registration form.
form.
Any subtag MAY be incorporated into a variety of language tags,
according to the rules of Section 2.1, including tags that do not
match any of the recommended prefixes of the registered subtag.
(Note that this is probably a poor choice.) This makes validation
simpler and thus more uniform across implementations, and does not
require the registration of a separate subtag for the same purpose
and meaning but a different recommended prefix.
The recommended prefixes for a given registered subtag will be The 'Prefix' field for a given registered subtag will be maintained
maintained in the IANA registry as a guide to usage. If it is in the IANA registry as a guide to usage. Additional prefixes MAY be
necessary to add an additional prefix to that list for an existing added by filing an additional registration form. In that form, the
language tag, that can be done by filing an additional registration "Any other relevant information:" field should indicate that it is
form. In that form, the "Any other relevant information:" field the addition of a prefix.
should indicate that it is the addition of an additional recommended
prefix.
Requests to add a recommended prefix to a subtag that imply a Requests to add a prefix to a variant subtag that imply a different
different semantic meaning will probably be rejected. For example, a semantic meaning will probably be rejected. For example, a request
request to add the prefix "de" to the subtag 'nedis' so that the tag to add the prefix "de" to the subtag 'nedis' so that the tag "de-
"de-nedis" represented some German dialect would be rejected. The nedis" represented some German dialect would be rejected. The
'nedis' subtag represents a particular Slovenian dialect and the 'nedis' subtag represents a particular Slovenian dialect and the
additional registration would change the semantic meaning assigned to additional registration would change the semantic meaning assigned to
the subtag. A separate subtag should be proposed instead. the subtag. A separate subtag should be proposed instead.
The 'Description' field must contain a description of the tag being The 'Description' field must contain a description of the tag being
registered written or transcribed into the Latin script; it may also registered written or transcribed into the Latin script; it may also
include a description in a non-Latin script. Non-ASCII characters include a description in a non-Latin script. Non-ASCII characters
must be escaped using the syntax described in Section 3.1. The must be escaped using the syntax described in Section 3.1. The
'Description' field is used for identification purposes and should 'Description' field is used for identification purposes and should
not be taken to represent the actual native name of the language or not be taken to represent the actual native name of the language or
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http://www.iana.org/numbers.html under "languages". http://www.iana.org/numbers.html under "languages".
Updates or changes to existing records, including previous Updates or changes to existing records, including previous
registrations, follow the same procedure as new registrations. The registrations, follow the same procedure as new registrations. The
Language Subtag Reviewer decides whether there is consensus to update Language Subtag Reviewer decides whether there is consensus to update
the registration following the two week review period; normally the registration following the two week review period; normally
objections by the original registrant will carry extra weight in objections by the original registrant will carry extra weight in
forming such a consensus. forming such a consensus.
Registrations are permanent and stable. Once registered, subtags Registrations are permanent and stable. Once registered, subtags
will not be removed from the registry and will remain the canonical will not be removed from the registry and will remain a valid way in
method of referring to a specific language or variant. This which to specify a specific language or variant.
provision does not apply to grandfathered tags, which may become
deprecated due to registration of subtags. For example, the tag
"i-navajo" is deprecated in favor of the tag "nv", which consists of
the single primary language subtag 'nv'.
Note: The purpose of the "published description" in the registration Note: The purpose of the "Description" in the registration form is
form is intended as an aid to people trying to verify whether a intended as an aid to people trying to verify whether a language is
language is registered or what language or language variation a registered or what language or language variation a particular subtag
particular subtag refers to. In most cases, reference to an refers to. In most cases, reference to an authoritative grammar or
authoritative grammar or dictionary of that language will be useful; dictionary of that language will be useful; in cases where no such
in cases where no such work exists, other well known works describing work exists, other well known works describing that language or in
that language or in that language may be appropriate. The subtag that language may be appropriate. The subtag reviewer decides what
reviewer decides what constitutes "good enough" reference material. constitutes "good enough" reference material. This requirement is
This requirement is not intended to exclude particular languages or not intended to exclude particular languages or dialects due to the
dialects due to the size of the speaker population or lack of a size of the speaker population or lack of a standardized orthography.
standardized orthography. Minority languages will be considered Minority languages will be considered equally on their own merits.
equally on their own merits.
3.5 Possibilities for Registration 3.5 Possibilities for Registration
Possibilities for registration of subtags or information about Possibilities for registration of subtags or information about
subtags include: subtags include:
o Primary language subtags for languages not listed in ISO 639 that o Primary language subtags for languages not listed in ISO 639 that
are not variants of any listed or registered language can be are not variants of any listed or registered language can be
registered. At the time this document was created there were no registered. At the time this document was created there were no
examples of this form of subtag. Before attempting to register a examples of this form of subtag. Before attempting to register a
language subtag, there MUST be an attempt to register the language language subtag, there MUST be an attempt to register the language
with ISO 639. No language subtags will be registered for codes with ISO 639. No language subtags will be registered for codes
that exist in ISO 639-1 or ISO 639-2, which are under that exist in ISO 639-1 or ISO 639-2, which are under
consideration by the ISO 639 maintenance or registration consideration by the ISO 639 maintenance or registration
authorities, or which have never been attempted for registration authorities, or which have never been attempted for registration
with those authorities. If ISO 639 has previously rejected a with those authorities. If ISO 639 has previously rejected a
language for registration, it is reasonable to assume that there language for registration, it is reasonable to assume that there
MUST be additional very compelling evidence of need before it will must be additional very compelling evidence of need before it will
be registered in the IANA registry (to the extent that it is very be registered in the IANA registry (to the extent that it is very
unlikely that any subtags will be registered of this type). unlikely that any subtags will be registered of this type).
o Dialect or other divisions or variations within a language, its o Dialect or other divisions or variations within a language, its
orthography, writing system, regional or historical usage, orthography, writing system, regional or historical usage,
transliteration or other transformation, or distinguishing transliteration or other transformation, or distinguishing
variation may be registered as variant subtags. An example is the variation may be registered as variant subtags. An example is the
'scouse' subtag (the Scouse dialect of English). 'scouse' subtag (the Scouse dialect of English).
o The addition or maintenance of fields (generally of an o The addition or maintenance of fields (generally of an
informational nature) in Tag or Subtag records as described in informational nature) in Tag or Subtag records as described in
Section 3.1 and subject to the stability provisions in Section 3.1 and subject to the stability provisions in
Section 3.3. This includes descriptions, recommended prefixes, Section 3.3. This includes descriptions; comments; deprecation
comments, deprecation of obsolete items, or the addition of script and preferred values for obsolete or withdrawn codes; or the
or extlang information to primary language subtags. addition of script or extlang information to primary language
subtags.
This document leaves the decision on what subtags or changes to This document leaves the decision on what subtags or changes to
subtags are appropriate (or not) to the registration process subtags are appropriate (or not) to the registration process
described in Section 3.4. described in Section 3.4.
Note: four character primary language subtags are reserved to allow Note: four character primary language subtags are reserved to allow
for the possibility of alpha4 codes in some future addition to the for the possibility of alpha4 codes in some future addition to the
ISO 639 family of standards. ISO 639 family of standards.
ISO 639 defines a maintenance agency for additions to and changes in ISO 639 defines a maintenance agency for additions to and changes in
skipping to change at page 33, line 20 skipping to change at page 34, line 18
Description: Description:
Comments: Comments:
Added: Added:
RFC: RFC:
Authority: Authority:
Contact_Email: Contact_Email:
Mailing_List: Mailing_List:
URL: URL:
%% %%
Figure 6: Format of Records in the Language Tag Extensions Registry Figure 7: Format of Records in the Language Tag Extensions Registry
'Identifier' contains the single letter subtag (singleton) assigned 'Identifier' contains the single letter subtag (singleton) assigned
to the extension. The Internet-Draft submitted to define the to the extension. The Internet-Draft submitted to define the
extension should specific which letter to use, although the IESG may extension should specific which letter to use, although the IESG may
change the assignment when approving the RFC. change the assignment when approving the RFC.
'Description' contains the name and description of the extension. 'Description' contains the name and description of the extension.
'Comments' is an optional field and may contain a broader description 'Comments' is an optional field and may contain a broader description
of the extension. of the extension.
skipping to change at page 34, line 24 skipping to change at page 35, line 23
most significant information be in the most significant (left-most) most significant information be in the most significant (left-most)
subtags, and that the specification gracefully handle truncated subtags, and that the specification gracefully handle truncated
subtags. subtags.
When a language tag is to be used in a specific, known, protocol, it When a language tag is to be used in a specific, known, protocol, it
is RECOMMENDED that that the language tag not contain extensions not is RECOMMENDED that that the language tag not contain extensions not
supported by that protocol. In addition, it should be noted that supported by that protocol. In addition, it should be noted that
some protocols may impose upper limits on the length of the strings some protocols may impose upper limits on the length of the strings
used to store or transport the language tag. used to store or transport the language tag.
3.7 Conversion of the RFC 3066 Language Tag Registry 3.7 Initialization of the Registry
Upon publication of this document as a BCP, the existing IANA Upon publication of this document as a BCP, the Language Subtag
language tag registry must be converted into the new subtag registry. Registry must be created and populated with the initial set of
This section defines the process for performing this conversion. subtags. This includes converting the entries from the existing IANA
language tag registry defined by RFC 3066 to the new format. This
section defines the process for defining the new registry and
performing the conversion of the old registry.
The impact on the IANA maintainers of the registry of this conversion The impact on the IANA maintainers of the registry of this conversion
will be a small increase in the frequency of new entries. The will be a small increase in the frequency of new entries. The
initial set of records represents no impact on IANA, since the work initial set of records represents no impact on IANA, since the work
to create it will be performed externally (as defined in this to create it will be performed externally (as defined in this
section). Future work will be limited to inserting or replacing section). Future work will be limited to inserting or replacing
whole records preformatted for IANA by the Language Subtag Reviewer. whole records preformatted for IANA by the Language Subtag Reviewer.
When this document is published, an email will be sent by the The initial registry will be created by the LTRU working group.
chair(s) of the LTRU working group to the LTRU and ietf-languages Using the instructions in this document, the working group will
mail lists advising of the impending conversion of the registry. In prepare an Informational RFC by creating a series of Internet-Drafts
that notice, the chair(s) will provide a URL whose referred content containing the prototype registry according to the rules in Sections
is the proposed IANA Language Subtag Registry following conversion. 4.2.2 and 4.2.3 and subject to IESG review as described in Section
There will be a Last Call period of not less than four weeks for 6.1.1 of RFC 2026 [8].
comments and corrections to be discussed on the
ietf-languages@iana.org mail list. Changes as a result of comments
will not restart the Last Call period. At the end of the period, the
chair(s) will forward the URL to IANA, which will post the new
registry on-line.
Tags that are currently deprecated will be maintained as When the Internet-Draft containing the prototype registry has been
grandfathered entries. The record for the grandfathered entry will approved by the IESG for publication as an RFC, the document will be
contain a 'Deprecated' field with the most appropriate date that can forwarded to IANA, which will post the contents of the new registry
be determined for when the record was deprecated. The 'Comments' on-line.
field will contain the reason for the deprecation. The 'Canonical'
field will contain the tag that replaces the value. For example, the
tag "art-lojban" is deprecated and will be placed in the
grandfathered section. It's 'Deprecated' field will contain the
deprecation date and 'Canonical' field the value "jbo".
Tags that are not deprecated that consist entirely of subtags that Tags in the RFC 3066 registry that are not deprecated that consist
are valid under this document and which have the correct form and entirely of subtags that are valid under this document and which have
format for tags defined by this document are superseded by this the correct form and format for tags defined by this document are
document. Such tags are placed in records of type 'redundant' in the superseded by this document. Such tags are placed in records of type
registry. For example, "zh-Hant" is now defined by this document. 'redundant' in the registry. For example, "zh-Hant" is now defined
by this document.
All other tags in the RFC 3066 registry that are deprecated will be
maintained as grandfathered entries. The record for the
grandfathered entry will contain a 'Deprecated' field with the most
appropriate date that can be determined for when the record was
deprecated. The 'Comments' field will contain the reason for the
deprecation. The 'Preferred-Value' field will contain the tag that
replaces the value. For example, the tag "art-lojban" is deprecated
and will be placed in the grandfathered section. It's 'Deprecated'
field will contain the deprecation date (in this case "2003-09-02")
and the 'Preferred-Value' field the value "jbo".
Tags that are not deprecated and which contain subtags which are Tags that are not deprecated and which contain subtags which are
consistent with registration under the guidelines in this document consistent with registration under the guidelines in this document
will have a new subtag registration created for each eligible subtag. will not automatically have a new subtag registration created for
If all of the subtags in the original tag are fully defined by the each eligible subtag. Interrested parties may use the registration
resulting registrations or by this document, then the original tag is process in Section 3.4 to register these subtags. If all of the
superseded by this document. Such tags are placed in the 'redundant' subtags in the original tag become fully defined by the resulting
section of the registry. For example, "en-boont" will result in a registrations, then the original tag is superseded by this document.
new subtag 'boont' and the RFC 3066 registered tag "en-boont" placed Such tags will have their record changed from type 'grandfathered' to
in the redundant section of the registry. type 'redundant' in the registry. For example, the subtag 'boont'
could be registered, resulting in the change of the grandfathered tag
"en-boont" to type redundant in the registry.
Tags that contain one or more subtags that do not match the valid Tags that contain one or more subtags that do not match the valid
registration pattern and which are not otherwise defined by this registration pattern and which are not otherwise defined by this
document will have records of type 'grandfathered' created in the document will have records of type 'grandfathered' created in the
registry. registry. These records cannot become type 'redundant', but may have
a 'Deprecated' and 'Prefered-Value' field added to them if a subtag
assignment or combination of assignments renders the tag obsolete.
There will be a reasonable period in which the community may comment There will be a reasonable period in which the community may comment
on the proposed list entries, which SHALL be no less than four weeks on the proposed list entries, which SHALL be no less than four weeks
in length. At the completion of this period, the chair(s) will in length. At the completion of this period, the chair(s) will
notify iana@iana.org and the ltru and ietf-languages mail lists that notify iana@iana.org and the ltru and ietf-languages mail lists that
the task is complete and forward the necessary materials to IANA for the task is complete and forward the necessary materials to IANA for
publication. publication.
Registrations that are in process under the rules defined in RFC 3066 Registrations that are in process under the rules defined in RFC 3066
MAY be completed under the former rules, at the discretion of the MAY be completed under the former rules, at the discretion of the
language tag reviewer. Any new registrations submitted after the language tag reviewer. Any new registrations submitted after the
request for conversion of the registry MUST be rejected. request for conversion of the registry MUST be rejected.
All existing RFC 3066 language tag registrations will be maintained All existing RFC 3066 language tag registrations will be maintained
in perpetuity. in perpetuity.
Users of tags that are grandfathered should consider registering Users of tags that are grandfathered should consider registering
appropriate subtags in the IANA subtag registry (but are not required appropriate subtags in the IANA subtag registry (but are not required
to). to).
Where two subtags have the same meaning, the priority of which to
make canonical SHALL be the following:
o As of the date of acceptance of this document as a BCP, if a code
exists in the associated ISO standard and it is not deprecated or
withdrawn as of that date, then it has priority.
o Otherwise, the earlier-registered tag in the associated ISO
standard has priority.
UN numeric codes assigned to 'macro-geographical (continental)' or UN numeric codes assigned to 'macro-geographical (continental)' or
sub-regions not associated with an assigned ISO 3166 alpha-2 code are sub-regions not associated with an assigned ISO 3166 alpha-2 code are
defined in the IANA registry and are valid for use in language tags. defined in the IANA registry and are valid for use in language tags.
These codes MUST be added to the initial version of the registry. These codes MUST be added to the initial version of the registry.
The UN numeric codes for 'economic groupings' or 'other groupings', The UN numeric codes for 'economic groupings' or 'other groupings',
and the alphanumeric codes in Appendix X of the UN document MUST NOT and the alphanumeric codes in Appendix X of the UN document MUST NOT
be added to the registry. be added to the registry.
When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49 When creating records for ISO 639, ISO 15924, ISO3166, and UN M.49
codes, the following criteria SHALL be applied to the inclusion, codes, the following criteria SHALL be applied to the inclusion,
canonical mapping, and deprecation of codes: preferred value, and deprecation of codes:
For each standard, the date of the standard referenced in RFC 1766 is For each standard, the date of the standard referenced in RFC 1766 is
selected as the starting date. Codes that were valid on that date in selected as the starting date. Codes that were valid on that date in
the selected standard are added to the registry. Codes that were the selected standard are added to the registry. Codes that were
previously assigned by were vacated or withdrawn before that date are previously assigned by but which were vacated or withdrawn before
not added to the registry. For each successive change to the that date are not added to the registry. For each successive change
standard, any additional assignments are added to the registry. to the standard, any additional assignments are added to the
Values that are withdrawn are marked as deprecated, but not removed. registry. Values that are withdrawn are marked as deprecated, but
Changes in meaning or assignment of a subtag are permitted during not removed. Changes in meaning or assignment of a subtag are
this process (cf. 'CS'). This continues up to the date that this permitted during this process (for example, the ISO 3166 code 'CS'
was originally assigned to 'Czechoslovakia' and is now assigned to
'Serbia and Montenegro'). This continues up to the date that this
document was adopted. The resulting set of records is added to the document was adopted. The resulting set of records is added to the
registry. Future changes or additions to this portion of the registry. Future changes or additions to this portion of the
registry are governed by the provisions of this document. registry are governed by the provisions of this document.
4. Formation and Processing of Language Tags 4. Formation and Processing of Language Tags
This section addresses how to use the registry with the language tag This section addresses how to use the registry with the language tag
format to choose, form and process language tags. format to choose, form and process language tags.
4.1 Choice of Language Tag 4.1 Choice of Language Tag
skipping to change at page 38, line 28 skipping to change at page 39, line 28
* For example, the subtag 'Latn' should not be used with the * For example, the subtag 'Latn' should not be used with the
primary language 'en' because nearly all English documents are primary language 'en' because nearly all English documents are
written in the Latin script and it adds no distinguishing written in the Latin script and it adds no distinguishing
information. However, if a document were written in English information. However, if a document were written in English
mixing Latin script with another script such as Braille mixing Latin script with another script such as Braille
('Brai'), then it may be appropriate to choose to indicate ('Brai'), then it may be appropriate to choose to indicate
both scripts to aid in content selection, such as the both scripts to aid in content selection, such as the
application of a stylesheet. application of a stylesheet.
3. If a subtag has a 'Canonical' field in its registry entry, the 3. If a tag or subtag has a 'Preferred-Value' field in its registry
canonical subtag SHOULD be used to form the language tag in entry, then the value of that field SHOULD be used to form the
preference to any of its aliases. language tag in preference to the tag or subtag in which the
preferred value appears.
* For example, use 'he' for Hebrew in preference to 'iw'. * For example, use 'he' for Hebrew in preference to 'iw'.
4. The 'und' (Undetermined) primary language subtag SHOULD NOT be 4. The 'und' (Undetermined) primary language subtag SHOULD NOT be
used to label content, even if the language is unknown. Omitting used to label content, even if the language is unknown. Omitting
the language tag altogether is preferred to using a tag with a the language tag altogether is preferred to using a tag with a
primary language subtag of 'und'. The 'und' subtag may be useful primary language subtag of 'und'. The 'und' subtag may be useful
for protocols that require a language tag to be provided. The for protocols that require a language tag to be provided. The
'und' subtag may also be useful when matching language tags in 'und' subtag may also be useful when matching language tags in
certain situations. certain situations.
skipping to change at page 39, line 11 skipping to change at page 40, line 11
6. The same variant subtag SHOULD NOT be used more than once within 6. The same variant subtag SHOULD NOT be used more than once within
a language tag. a language tag.
* For example, do not use "en-GB-scouse-scouse". * For example, do not use "en-GB-scouse-scouse".
To ensure consistent backward compatibility, this document contains To ensure consistent backward compatibility, this document contains
several provisions to account for potential instability in the several provisions to account for potential instability in the
standards used to define the subtags that make up language tags. standards used to define the subtags that make up language tags.
These provisions mean that no language tag created under the rules in These provisions mean that no language tag created under the rules in
this document will become obsolete. In addition, tags that are in this document will become obsolete.
canonical form will always be in canonical form.
4.2 Meaning of the Language Tag 4.2 Meaning of the Language Tag
The language tag always defines a language as spoken (or written, The language tag always defines a language as spoken (or written,
signed or otherwise signaled) by human beings for communication of signed or otherwise signaled) by human beings for communication of
information to other human beings. Computer languages such as information to other human beings. Computer languages such as
programming languages are explicitly excluded. programming languages are explicitly excluded.
If a language tag B contains language tag A as a prefix, then B is If a language tag B contains language tag A as a prefix, then B is
typically "narrower" or "more specific" than A. For example, "zh- typically "narrower" or "more specific" than A. For example, "zh-
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Since a particular language tag may be used in many processes, Since a particular language tag may be used in many processes,
language tags SHOULD always be created or generated in a canonical language tags SHOULD always be created or generated in a canonical
form. form.
A language tag is in canonical form when: A language tag is in canonical form when:
1. The tag is well-formed according the rules in Section 2.1 and 1. The tag is well-formed according the rules in Section 2.1 and
Section 2.2. Section 2.2.
2. None of the subtags in the language tag has a Canonical-Value 2. Subtags of type 'Region' that have a Preferred-Value mapping in
mapping in the IANA registry (see Section 3.1). Subtags with a the IANA registry (see Section 3.1) SHOULD be replaced with their
Canonical-Value mapping MUST be replaced with their mapping in mapped value.
order to canonicalize the tag.
3. If more than one extension subtag sequence exists, the extension 3. Redundant or grandfathered tags that have a Preferred-Value
mapping in the IANA registry (see Section 3.1) MUST be replaced
with their mapped value. These items are either deprecated
mappings created before the adoption of this document (such as
the mapping of "no-nyn" to "nn" or "i-klingon" to "tlh") or are
the result of later registrations or additions to this document
(for example, "zh-guoyu" might be mapped to a language-extlang
combination such as "zh-cmn" by some future update of this
document).
4. Other subtags that have a Preferred-Value mapping in the IANA
registry (see Section 3.1) MUST be replaced with their mapped
value. These items consist entirely of clerical corrections to
ISO 639-1 in which the deprecated subtags have been maintained
for compatibility purposes.
5. If more than one extension subtag sequence exists, the extension
sequences are ordered into case-insensitive ASCII order by sequences are ordered into case-insensitive ASCII order by
singleton subtag. singleton subtag.
Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz" is in canonical
form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in form, while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in
canonical form. canonical form.
Example: The language tag "en-NH" (English as used in the New Example: The language tag "en-NH" (English as used in the New
Hebrides) is not canonical because the 'NH' subtag has a canonical Hebrides) is not canonical because the 'NH' subtag has a canonical
mapping to 'VU' (Vanuatu). mapping to 'VU' (Vanuatu), although the tag "en-NH" maintains its
validity.
Canonicalization of language tags does not imply anything about the Canonicalization of language tags does not imply anything about the
use of upper or lowercase letters when processing or comparing use of upper or lowercase letters when processing or comparing
subtags (and as described in Section 2.1). All comparisons MUST be subtags (and as described in Section 2.1). All comparisons MUST be
performed in a case-insensitive manner. performed in a case-insensitive manner.
When performing canonicalization of language tags, processors MAY When performing canonicalization of language tags, processors MAY
optionally regularize the case of the subtags, following the case optionally regularize the case of the subtags, following the case
used in the registry. Note that this corresponds to the following used in the registry. Note that this corresponds to the following
casing rules: uppercase all non-initial two-letter subtags; titlecase casing rules: uppercase all non-initial two-letter subtags; titlecase
skipping to change at page 41, line 27 skipping to change at page 42, line 42
specific cases that are known to cause problems with this. In specific cases that are known to cause problems with this. In
particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is particular, the letter 'i' (U+0069) in Turkish and Azerbaijani is
uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE). uppercased to U+0130 (LATIN CAPITAL LETTER I WITH DOT ABOVE).
Implementers should specify a locale-neutral casing operation to Implementers should specify a locale-neutral casing operation to
ensure that case folding of subtags does not produce this value, ensure that case folding of subtags does not produce this value,
which is illegal in language tags. For example, if one were to which is illegal in language tags. For example, if one were to
uppercase the region subtag 'in' using Turkish locale rules, the uppercase the region subtag 'in' using Turkish locale rules, the
sequence U+0130 U+004E would result instead of the expected 'IN'. sequence U+0130 U+004E would result instead of the expected 'IN'.
Note: if the field 'Deprecated' appears in a registry record without Note: if the field 'Deprecated' appears in a registry record without
an accompanying 'Canonical' field, then that tag or subtag is an accompanying 'Preferred-Value' field, then that tag or subtag is
deprecated without a replacement. Validating processors SHOULD NOT deprecated without a replacement. Validating processors SHOULD NOT
generate tags that include these values, although the values are generate tags that include these values, although the values are
canonical when they appear in a language tag. canonical when they appear in a language tag.
An extension MUST define any relationships that may exist between the An extension MUST define any relationships that may exist between the
various subtags in the extension and thus MAY define an alternate various subtags in the extension and thus MAY define an alternate
canonicalization scheme for the extension's subtags. Extensions MAY canonicalization scheme for the extension's subtags. Extensions MAY
define how the order of the extension's subtags are interpreted. For define how the order of the extension's subtags are interpreted. For
example, an extension could define that its subtags are in canonical example, an extension could define that its subtags are in canonical
order when the subtags are placed into ASCII order: that is, "en-a- order when the subtags are placed into ASCII order: that is, "en-a-
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Section 3.6. In addition, there may be occasional requests from the Section 3.6. In addition, there may be occasional requests from the
maintaining authority for a specific extension to update the contact maintaining authority for a specific extension to update the contact
information or URLs in the record. These requests MUST include the information or URLs in the record. These requests MUST include the
complete, updated record. IANA is not responsible for validating the complete, updated record. IANA is not responsible for validating the
information provided, only that it is properly formatted. It should information provided, only that it is properly formatted. It should
reasonably be seen to come from the maintaining authority named in reasonably be seen to come from the maintaining authority named in
the record present in the registry. the record present in the registry.
6. Security Considerations 6. Security Considerations
The only security issue that has been raised with language tags since Language tags used in content negotiation, like any other information
the publication of RFC 1766 [21], which stated that "Security issues exchanged on the Internet, may be a source of concern because they
are believed to be irrelevant to this memo", is a concern with may be used to infer the nationality of the sender, and thus identify
language identifiers used in content negotiation - that they may be
used to infer the nationality of the sender, and thus identify
potential targets for surveillance. potential targets for surveillance.
This is a special case of the general problem that anything sent is This is a special case of the general problem that anything sent is
visible to the receiving party and possibly to third parties as well. visible to the receiving party and possibly to third parties as well.
It is useful to be aware that such concerns can exist in some cases. It is useful to be aware that such concerns can exist in some cases.
The evaluation of the exact magnitude of the threat, and any possible The evaluation of the exact magnitude of the threat, and any possible
countermeasures, is left to each application protocol (see BCP 72, countermeasures, is left to each application protocol (see BCP 72,
RFC 3552 [15] for best current practice guidance on security threats RFC 3552 [15] for best current practice guidance on security threats
and defenses). and defenses).
Although the specification of valid subtags for an extension MUST be Since there is no limit to the number of variant, private use, and
available over the Internet, implementations SHOULD NOT mechanically extension subtags, and consequently no limit on the possible length
depend on it being always accessible, to prevent denial-of-service of a tag, implementations need to guard against buffer overflow
attacks. attacks. See section Section 2.1.1 for details on language tag
truncation, which can occur as a consequence of defenses against
buffer overflow.
Although the specification of valid subtags for an extension (see:
Section 3.6) MUST be available over the Internet, implementations
SHOULD NOT mechanically depend on it being always accessible, to
prevent denial-of-service attacks.
7. Character Set Considerations 7. Character Set Considerations
The syntax in this document requires that language tags use only the The syntax in this document requires that language tags use only the
characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most
character sets, so the composition of language tags should not have character sets, so the composition of language tags should not have
any character set issues. any character set issues.
Rendering of characters based on the content of a language tag is not Rendering of characters based on the content of a language tag is not
addressed in this memo. Historically, some languages have relied on addressed in this memo. Historically, some languages have relied on
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region subtags respectively. region subtags respectively.
o Adds a well-defined extension mechanism. o Adds a well-defined extension mechanism.
o Defines an extended language subtag, possibly for use with certain o Defines an extended language subtag, possibly for use with certain
anticipated features of ISO 639-3. anticipated features of ISO 639-3.
Ed Note: The following items are provided for the convenience of Ed Note: The following items are provided for the convenience of
reviewers and will be removed from the final document. reviewers and will be removed from the final document.
Changes between draft-ietf-ltru-registry-01 and this version are: Changes between draft-ietf-ltru-registry-02 and this version are:
o Minor updates to the changes section (the text just above) to o Modified the title and some of the front matter of Section 3.7
reflect various updates in the WG drafts (A.Phillips) from "Conversion of the RFC 3066 Language Tag Registry"
(A.Phillips)
o Minor change to the section on the extensions registry (because o Modified the rules for registry creation so that no variant
there can be 35, not 25, entries maximum. (D.Ewell) registrations are created ab initio. (#922) (J.Cowan)
o Changed "SHOULD NOT permit a subtag to be divided" to MUST NOT. o Modified the document to replace 'Canonical' with 'Preferred-
(#944) (R.Presuhn) Value' and to implement the various design changes necessary to
deal with canonicalization. (#954) (F.Ellermann, A.Phillips, et
al)
o Added text to Section 3.1 and Section 4.1 describing the rationale o Corrected the ABNF so that 'lang' is defined as 2*4ALPHA (J.Cowan)
for Suppress-Script. Both sentences are slight rewordings of this
text suggested in the email thread: "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." (#954) (F.Ellermann,
A.Phillips)
o Added text about case folding during canonicalization. This also o Changed the requirement in Section 2.1.1 on truncation of tags
includes rules in Section 3.2 for casing of registry entries, as from MUST to SHOULD and added a sentence about the harm this may
well the insertion of the text permitting case normalization in cause. (F.Ellermann, D.Ewell)
Section 4.3 and the warning about locale-specific casing
operations in the same section. (#985) (F.Ellermann, J.Cowan,
A.Phillips)
o Fixed the reference to Canonical-Value in Section 4.3. o Changed "MUST be very compelling" to "must (etc.)" in Section 3.5.
(R.Presuhn)
o Changed "STRONGLY RECOMMENDED" to "strongly RECOMMENDED"
(R.Presuhn)
o Added sentences pertaining to the File-Date record to Section 3.1.
(#941) (R.Presuhn)
o Changed the process by which the prototype registry is created
from a mere document to an Informational RFC. (#838, #835) (??)
o Changed the Security Considerations (Section 6) and Length
Considerations (Section 2.1.1) sections to address potential
buffer overflow attacks and suggest a lower limit on buffer length
allocation (#944)(#965) (R.Presuhn, I.McDonald)
o Clarified a sentence in Security Considerations (Section 6) to
make clear that it refers to extensions and not the language
subtag registry. (#965) (I.McDonald)
o Added the limitation in the ABNF on the number of extlang subtags
(limited to three) (#965) (R.Presuhn, A.Phillips)
o Added notes to extlang and variant explaining that they should be
used with their Recommended-Prefixes. (A.Phillips)
o Changed the name of the 'Recommended-Prefix' field to 'Prefix' and
the requirements for validating processors to require the prefix
with variants and extlangs. (#1018) (J.Cowan, F.Ellerman)
o Added notes about when variants may be used together and the
relationship of the 'Prefix' field to this in Section 2.2.5
(A.Phillips) (A.Phillips)
o In Section 3.4, changed the reference from the subtag 'nv' to the
tag "nv" to be consistent with the wording in Section 3.1. (part
of #954) (D.Ewell)
o Added missing word 'that' in Section 3.6 (A.Phillips) o Specified that 'Prefix' fields may be added only to 'variant'
subtag records and not to 'extlang' records. (J.Cowan)
9. References 9. References
9.1 Normative References 9.1 Normative References
[1] International Organization for Standardization, "ISO 639- [1] International Organization for Standardization, "ISO 639-
1:2002, Codes for the representation of names of languages -- 1:2002, Codes for the representation of names of languages --
Part 1: Alpha-2 code", ISO Standard 639, 2002. Part 1: Alpha-2 code", ISO Standard 639, 2002.
[2] International Organization for Standardization, "ISO 639-2:1998 [2] International Organization for Standardization, "ISO 639-2:1998
skipping to change at page 59, line 6 skipping to change at page 60, line 6
Type: region Type: region
Subtag: 003 Subtag: 003
Description: North America Description: North America
Added: 2004-07-06 Added: 2004-07-06
%% %%
Type: variant Type: variant
Subtag: 1901 Subtag: 1901
Description: Traditional German Description: Traditional German
orthography orthography
Added: 2004-09-09 Added: 2004-09-09
Recommended-Prefix: de Prefix: de
Comment: <shows continuation> Comment: <shows continuation>
%% %%
Type: variant Type: variant
Subtag: 1996 Subtag: 1996
Description: German orthography of 1996 Description: German orthography of 1996
Added: 2004-09-09 Added: 2004-09-09
Recommended-Prefix: de Prefix: de
%% %%
Type: variant Type: variant
Subtag: boont Subtag: boont
Description: Boontling Description: Boontling
Added: 2003-02-14 Added: 2003-02-14
Recommended-Prefix: en Prefix: en
%% %%
Type: variant Type: variant
Subtag: gaulish Subtag: gaulish
Description: Gaulish Description: Gaulish
Added: 2001-05-25 Added: 2001-05-25
Recommended-Prefix: cel Prefix: cel
%% %%
Type: grandfathered Type: grandfathered
Tag: art-lojban Tag: art-lojban
Description: Lojban Description: Lojban
Added: 2001-11-11 Added: 2001-11-11
Canonical: jbo Canonical: jbo
Deprecated: 2003-09-02 Deprecated: 2003-09-02
%% %%
Type: grandfathered Type: grandfathered
Tag: en-GB-oed Tag: en-GB-oed
skipping to change at page 60, line 12 skipping to change at page 61, line 12
Tag: az-Arab Tag: az-Arab
Description: Azerbaijani in Arabic script Description: Azerbaijani in Arabic script
Added: 2003-05-30 Added: 2003-05-30
%% %%
Type: redundant Type: redundant
Tag: az-Cyrl Tag: az-Cyrl
Description: Azerbaijani in Cyrillic script Description: Azerbaijani in Cyrillic script
Added: 2003-05-30 Added: 2003-05-30
%% %%
Figure 7: Example of the Registry Format Figure 8: Example of the Registry Format
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 End of changes. 

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