WDIFF

draft-ietf-ltru-registry-00.txt --> draft-ietf-ltru-registry-01.txt

Network Working Group A. Phillips, Ed.
Internet-Draft Quest Software
Expires: September 11, October 28, 2005 M. Davis, Ed.
IBM
March 10,
April 26, 2005

Tags for Identifying Languages
draft-ietf-ltru-registry-00
draft-ietf-ltru-registry-01

Status of this Memo

This document is an Internet-Draft and is subject to all provisions
of Section 3 of RFC 3667.

By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
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aware will be disclosed, in accordance with
RFC 3668. Section 6 of BCP 79.

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Abstract

This document describes the structure, content, construction, and
semantics of language tags for use in cases where it is desirable to
indicate the language used in an information object. It also
describes how to register values for use in language tags and the
creation of user defined extensions for private interchange. This
document obsoletes RFC 3066 (which replaced RFC 1766).

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document obsoletes RFC 3066 (which replaced RFC 1766).

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Language Tag . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 Length Considerations . . . . . . . . . . . . . . . . 5 6
2.2 Language Subtag Sources and Interpretation . . . . . . . . 6 7
2.2.1 Primary Language Subtag . . . . . . . . . . . . . . . 7 8
2.2.2 Extended Language Subtags . . . . . . . . . . . . . . 9 10
2.2.3 Script Subtag . . . . . . . . . . . . . . . . . . . . 9 10
2.2.4 Region Subtag . . . . . . . . . . . . . . . . . . . . 10 11
2.2.5 Variant Subtags . . . . . . . . . . . . . . . . . . . 11 12
2.2.6 Extension Subtags . . . . . . . . . . . . . . . . . . 11 13
2.2.7 Private Use Subtags . . . . . . . . . . . . . . . . . 12 14
2.2.8 Pre-Existing RFC 3066 Registrations . . . . . . . . . 13 15
2.2.9 Possibilities for Registration Classes of Conformance . . . . . . . . . . . . . 13
2.2.10 Classes of Conformance . . . 15
3. Registry Format and Maintenance . . . . . . . . . . . . . 14
2.3 Choice of Language Tag . . 17
3.1 Format of the IANA Language Subtag Registry . . . . . . . 17
3.2 Maintenance of the Registry . . . . . . . . . 15
2.4 Meaning of the Language Tag . . . . . . 21
3.3 Stability of IANA Registry Entries . . . . . . . . . 16
2.4.1 Canonicalization of Language Tags . . . 22
3.4 Registration Procedure for Subtags . . . . . . . 17
2.5 Considerations for Private Use Subtags . . . . . 25
3.5 Possibilities for Registration . . . . . 18
3. IANA Considerations . . . . . . . . . 29
3.6 Extensions and Extensions Namespace . . . . . . . . . . . 20
3.1 Format 30
3.7 Conversion of the IANA RFC 3066 Language Subtag Tag Registry . . . . . 33
4. Formation and Processing of Language Tags . . 20
3.2 Stability of IANA Registry Entries . . . . . . . . 36
4.1 Choice of Language Tag . . . . 24
3.3 Registration Procedure for Subtags . . . . . . . . . . . . 27
3.4 Extensions and Extensions Namespace . . 36
4.2 Meaning of the Language Tag . . . . . . . . . 30
4. Security Considerations . . . . . . 38
4.3 Canonicalization of Language Tags . . . . . . . . . . . . 32
5. Character Set 39
4.4 Considerations for Private Use Subtags . . . . . . . . . . 40
5. IANA Considerations . . . . . . 33
6. Changes from RFC 3066 . . . . . . . . . . . . . . . 42
6. Security Considerations . . . . 34
7. References . . . . . . . . . . . . . . . 43
7. Character Set Considerations . . . . . . . . . . 36
Authors' Addresses . . . . . . . 44
8. Changes from RFC 3066 . . . . . . . . . . . . . . 38
A. Acknowledgements . . . . . . 45
9. References . . . . . . . . . . . . . . . . 39
B. Examples of Language Tags (Informative) . . . . . . . . . . 40
C. Conversion 50
9.1 Normative References . . . . . . . . . . . . . . . . . . . 50
9.2 Informative References . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 52
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53
B. Examples of the RFC 3066 Language Tag Tags (Informative) . . . . . . . . . . . 54
C. Example Registry . . . . . . 42 . . . . . . . . . . . . . . . . . 57
Intellectual Property and Copyright Statements . . . . . . . 44 . 61

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1. Introduction

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
language used when presenting or requesting information.

Information about a user's language preferences commonly needs to be
identified so that appropriate processing can be applied. For
example, the user's language preferences in a browser can be used to
select web pages appropriately. A choice of language preference can
also be used to select among tools (such as dictionaries) to assist
in the processing or understanding of content in different languages.

In addition, knowledge about the particular language used by some
piece of information content may be useful or even required by some
types of information processing; for example spell-checking,
computer-synthesized speech, Braille transcription, or high-quality
print renderings.

One means of indicating the language used is by labeling the
information content with a language identifier. These identifiers
can also be used to specify user preferences when selecting
information content, or for labeling additional attributes of content
and associated resources.

These identifiers can also be used to indicate additional attributes
of content that are closely related to the language. In particular,
it is often necessary to indicate specific information about the
dialect, writing system, or orthography used in a document or
resource, as these attributes may be important for the user to obtain
information in a form that they can understand, or important in
selecting appropriate processing resources for the given content.

This document specifies an identifier mechanism and a registration
function for values to be used with that identifier mechanism. It
also defines a mechanism for private use values and future extension.

This document replaces RFC 3066, which replaced RFC 1766. For a list
of changes in this document, see Section 6. 8.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119] [11]. [10].

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2. The Language Tag

2.1 Syntax

The language tag is composed of one or more parts: A primary language
subtag and a (possibly empty) series of subsequent subtags. Subtags
are distinguished by their length, position in the subtag sequence,
and content, so that each type of subtag can be recognized solely by
these features. This makes it possible to construct a parser that
can extract and assign some semantic information to the subtags, even
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
most searching and matching operations.

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The syntax of this tag in ABNF [RFC 2234] [13] [7] is:

Language-Tag = (lang
*("-" extlang)
["-" script]
["-" region]
*("-" variant)
*("-" extension)
["-" privateuse])
/ privateuse ; private-use tag
/ grandfathered ; grandfathered registrations

lang = 2*3ALPHA ; shortest ISO 639 code
/ registered-lang
extlang = 3ALPHA ; reserved for future use
script = 4ALPHA ; ISO 15924 code
region = 2ALPHA ; ISO 3166 code
/ 3DIGIT ; UN country number
variant = ALPHA (4*7alphanum) 5*8alphanum ; registered variants
/ ( DIGIT (3*7alphanum) 3alphanum )
extension = singleton 1*("-" (2*8alphanum)) ; extension subtag(s)
privateuse = ("x"/"X") 1*("-" (1*8alphanum)) ; private use subtag(s)
singleton = ("a"-"w" %x41-57 / %x59-5A / %x61-77 / %x79-7A / DIGIT
; "a"-"w" / "y"-"z" / "A"-"W" / "Y"-"Z") "Y"-"Z" / "0"-"9"
; Single letters: x/X is reserved for private use
registered-lang = 4*8ALPHA ; registered language subtag
grandfathered = 1*3ALPHA 1*2("-" (2*8alphanum))
; grandfathered registration
; Note: i is the only singleton
; that starts
; a grandfathered tag
alphanum = (ALPHA / DIGIT) ; letters and numbers

Figure 1: Language Tag ABNF

The character "-" is HYPHEN-MINUS (ABNF: %x2D). All subtags have a
maximum length of eight characters. Note that there is a subtlety in
the ABNF for 'variant': variants starting with a digit may consist of sequences

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of up to eight characters. be only
four characters long, while those starting with a letter must be at
least five characters long.

Whitespace is not permitted in a language tag. For examples of
language tags, see Appendix B.

Note that although [RFC 2234] [13] [7] refers to octets, the language tags described
in this document are sequences of characters from the US-ASCII
repertoire. Language tags may be used in documents and applications
that use other encodings, so long as these encompass the US-ASCII
repertoire. An example of this would be an XML document that uses

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the Unicode UTF-16LE encoding. [12] encoding of Unicode [20].

The tags and their subtags, including private-use and extensions, are
to be treated as case insensitive: there exist conventions for the
capitalization of some of the subtags, but these should not be taken
to carry meaning.

For example:

o [ISO 639] [1] recommends that language codes be written in lower
case ('mn' Mongolian).

o [ISO 3166] [4] recommends that country codes be capitalized ('MN'
Mongolia).

o [ISO 15924] [3] recommends that script codes use lower case with
the initial letter capitalized ('Cyrl' Cyrillic).

However, in the tags defined by this document, the uppercase US-ASCII
letters in the range 'A' (ABNF: %x41) through 'Z' (ABNF: %x5A) are considered equivalent and
mapped directly to their US-ASCII lowercase equivalents in the range
'a' (ABNF: %x61) through 'z' (ABNF: %x7A). 'z'. Thus the tag "mn-Cyrl-MN" is not distinct from "MN-cYRL-mn" "MN-
cYRL-mn" or "mN-cYrL-Mn" (or any other combination) and each of these
variations conveys the same meaning: Mongolian written in the
Cyrillic script as used in Mongolia.

For informative examples of language tags, see Appendix B at the end
of this document.

2.1.1 Length Considerations

Although neither the ABNF nor other guidelines in this document
provide a fixed upper limit on the number of size of subtags in a Language
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
practice these are rare because additional granularity in tags seldom
adds useful distinguishing information and because longer, more
granular tags interefere with the meaning, understanding, and
processing of language tags.

In particular, variant subtags SHOULD be used only with their
recommended prefix. This In practice, this limits most tags to a sequence
of four

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subtags subtags, and thus a maximum length of 26 characters
(excluding any extensions or private use sequences). This is because
subtags are limited to a length of eight characters and the extlang,
script, and region subtags are limited to even fewer characters. See
Section 2.3 4.1 for more information on selecting the most appropriate
Language Tag.

A conformant implementation need not MAY refuse to support the storage of
language tags which exceed a specified length. For an example, see

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[RFC 2231]
[12]. [22]. Any such a limitation MUST 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 SHOULD NOT permit a
subtag to be divided.

2.2 Language Subtag Sources and Interpretation

The namespace of language tags and their subtags is administered by
the Internet Assigned Numbers Authority (IANA) [17] [13] according to the
rules in Section 3 5 of this document. The registry maintained by IANA
is the source for valid subtags: other standards referenced in this
section provide the source material for that registry.

Terminology in this section:

o Tag or tags refers to a complete language tag, such as
"fr-Latn-CA". Examples of tags in this document are enclosed in
double-quotes ("en-US").

o Subtag refers to a specific section of a tag, separated delimited by hyphen,
such as the subtag 'Latn' in "fr-Latn-CA". Examples of subtags in
this document are enclosed in single quotes ('Latn').

o Code or codes refers to tags values defined in external standards (and
which are used as subtags in this document). For example, 'Latn'
is an [ISO 15924] [3] script code which was used to define the
'Latn' script subtag for use in a language tag. Examples of codes
in this document are enclosed in single quotes ('en', 'Latn').

The definitions in this section apply to the various subtags within
the language tags defined by this document, excepting those
"grandfathered" tags defined in Section 2.2.8.

Language tags are designed so that each subtag type has unique length
and content restrictions. These make identification of the subtag's
type possible, even if the content of the subtag itself is
unrecognized. This allows tags to be parsed and processed without
reference to the latest version of the underlying standards or the
IANA registry and makes the associated exception handling when
parsing tags simpler.

Subtags in the IANA registry that do not come from an underlying
standard can only appear in specific positions in a tag.
Specifically, they can only occur as primary language subtags or as

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variant subtags.

Note that sequences of private-use and extension subtags MUST occur

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at the end of the sequence of subtags and MUST NOT be interspersed
with subtags defined elsewhere in this document.

Single letter and digit subtags are reserved for current or future
use. These include the following current uses:

o The single letter subtag 'x' is reserved to introduce a sequence
of private-use subtags. The interpretation of any private-use
subtags is defined solely by private agreement and is not defined
by the rules in this section or in any standard or registry
defined in this document.

o All other single letter subtags are reserved to introduce
standardized extension subtag sequences as described in
Section 3.4. 3.6.

The single letter subtag 'i' is used by some grandfathered tags, such
as "i-enochian", where it always appears in the first position and
cannot be confused with an extension.

2.2.1 Primary Language Subtag

The primary language subtag is the first subtag in a language tag
(with the exception of private-use and certain grandfathered tags)
and cannot be empty. Except as noted, the primary subtag is the language
subtag. omitted. The following rules apply to the assignment and
interpretation of the primary
language subtag:

1. All 2-character two character language subtags were defined in the IANA
registry according to the assignments found in the standard ISO
639 Part 1, "ISO 639-1:2002, Codes for the representation of
names of languages -- Part 1: Alpha-2 code" [ISO 639-1] [1], or
using assignments subsequently made by the ISO 639 Part 1
maintenance agency or governing standardization bodies.
o

2. All 3-character three character language subtags were defined in the IANA
registry according to the assignments found in ISO 639 Part 2,
"ISO 639-2:1998 - Codes for the representation of names of
languages -- Part 2: Alpha-3 code - edition 1" [ISO 639-2] [2],
or assignments subsequently made by the ISO 639 Part 2
maintenance agency or governing standardization bodies.
o

3. The subtags in the range 'qaa' through 'qtz' are reserved for
private use in language tags. These subtags correspond to codes
reserved by ISO 639-2 for private use. These codes MAY be used
for non-registered primary-language subtags (instead of using
private-use subtags following 'x-'). Please refer to Section 2.5 4.4
for more information on private use subtags.

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4. All four character language subtags are reserved for possible
future standardization.

5. All language subtags of 4 5 to 8 characters in length in the IANA
registry were defined via the registration process in Section 3.3 3.4
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
subtag and future registrations of this type will be discouraged:
primary languages are STRONGLY RECOMMENDED for registration with
ISO 639 and subtags proposals rejected by ISO 639 639/RA will be closely
scrutinized before they are registered with IANA.
o

6. The single character subtag 'x' as the primary subtag indicates
that the language tag consists solely of subtags whose meaning is
defined by private agreement. For example, in the tag "x-fr-CH",
the subtags 'fr' and 'CH' should not be taken to represent the
French language or the country of Switzerland (or any other value
in the IANA registry) unless there is a private agreement in
place to do so. See Section 2.5.
o 4.4.

7. The single character subtag 'i' is used by some grandfathered
tags (see Section 2.2.8) such as "i-klingon" and "i-bnn". (Other
grandfathered tags have a primary language subtag in their first
position)

8. Other values MUST NOT be assigned to the primary subtag except by
revision or update of this document.

Note: For languages that have both an ISO 639-1 2-character two character code
and an ISO 639-2 3-character three character code, only the ISO 639-1 2-character two
character code is defined in the IANA registry.

Note: For languages that have no ISO 639-1 2-character two character code and for
which the ISO 639-2/T (Terminology) code and the ISO 639-2/B
(Bibliographic) codes differ, only the Terminology code is defined in
the IANA registry. At the time this document was created, all
languages that had both kinds of 3-character three character code were also
assigned a 2-character two character code; it is not expected that future
assignments of this nature will occur.

Note: To avoid problems with versioning and subtag choice as
experienced during the transition between RFC 1766 and RFC 3066, as
well as the canonical nature of subtags defined by this document, the
ISO 639 Registration Authority Joint Advisory Committee (ISO
639/RA-JAC) 639/
RA-JAC) has included the following statement in [6]: [16]:

"A language code already in ISO 639-2 at the point of freezing ISO
639-1 shall not later be added to ISO 639-1. This is to ensure

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consistency in usage over time, since users are directed in Internet
applications to employ the alpha-3 code when an alpha-2 code for that
language is not available."

In order to avoid instability of the canonical form of tags, if a
2-character two
character code is added to ISO 639-1 for a language for which a
3-character three
character code was already included in ISO 639-2, the 2-character two character
code will not be added as a subtag in the registry. See Section 3.2. 3.3.

For example, if some content were tagged with 'haw' (Hawaiian), which

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currently has no 2-character two character code, the tag would not be invalidated
if ISO 639-1 were to assign a 2-character two character code to the Hawaiian
language at a later date.

For example, one of the grandfathered IANA registrations is
"i-enochian". The subtag 'enochian' could be registered in the IANA
registry as a primary language subtag (assuming that ISO 639 does not
register this language first), making tags such as "enochian-AQ" and
"enochian-Latn" valid.

2.2.2 Extended Language Subtags

The following rules apply to the extended language subtags:

1. Three letter subtags immediately following the primary subtag are
reserved for future standardization, anticipating work that is
currently under way on ISO 639.
o

2. Extended language subtags MUST follow the primary subtag and
precede any other subtags.
o

3. There MAY be any additional number of extended language subtags.
o

4. Extended language subtags will not be registered except by
revision of this document.
o

5. Extended language subtags MUST NOT be used to form language tags
except by revision of this document.

Example: In a future revision or update of this document, the tag
"zh-gan" (registered under RFC 3066) might become a valid
non-grandfathered non-
grandfathered (that is, redundant) tag in which the subtag 'gan'
might represent the Chinese dialect 'Gan'.

2.2.3 Script Subtag

The following rules apply to the script subtags:

o All 4-character subtags were

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1. All four character subtags were defined according to ISO 15924
[3]--"Codes for the representation of the names of scripts":
alpha-4 script codes, or subsequently assigned by the ISO 15924
maintenance agency or governing standardization bodies, denoting
the script or writing system used in conjunction with this
language.
o

2. Script subtags MUST immediately follow the primary language
subtag and all extended language subtags and MUST occur before
any other type of subtag described below.
o

3. The script subtags 'Qaaa' through 'Qabx' are reserved for private
use in language tags. These subtags correspond to codes reserved
by ISO 15924 for private use. These codes MAY be used for non-registered non-
registered script values. Please refer to Section 2.5 4.4 for more
information on private-use subtags.

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4. Script subtags cannot be registered using the process in
Section 3.3 3.4 of this document. Variant subtags may be considered
for registration for that purpose.

Example: "de-Latn" represents German written using the Latin script.

2.2.4 Region Subtag

The following rules apply to the region subtags:

1. The region subtag defines language variations used in a specific
region, geographic, or political area. Region subtags MUST
follow any language, extended language, or script subtags and
MUST precede all other subtags.
o

2. All 2-character two character subtags following the primary subtag were
defined in the IANA registry according to the assignments found
in ISO 3166 [4]--"Codes for the representation of names of
countries and their subdivisions - Part 1: Country
codes"--alpha-2 country codes or assignments subsequently made by
the ISO 3166 maintenance agency or governing standardization
bodies.
o

3. All 3-character three character codes consisting of digit (numeric)
characters were defined in the IANA registry according to the
assignments found in UN Standard Country or Area Codes for
Statistical Use [5] or assignments subsequently made by the
governing standards body. Note that not all of the UN M.49 codes
are defined in the IANA registry:
*

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A. UN numeric codes assigned to 'macro-geographical
(continental)' or sub-regions not associated with an assigned
ISO 3166 alpha-2 code _are_ defined.
*

B. UN numeric codes for 'economic groupings' or 'other
groupings' are _not_ defined in the IANA registry and MUST
NOT be used to form language tags.
* Countries

C. UN numeric codes for countries with ambiguous ISO 3166
alpha-2 codes as defined in Section 3.2 3.3 are defined in the
registry and are canonical for the given country or region
defined.
*

D. The alphanumeric codes in Appendix X of the UN document are
_not_ defined and MUST NOT be used to form language tags.
(At the time this document was created these values match the
ISO 3166 alpha-2 codes.)
o

4. There may be at most one region subtag in a language tag.
o

5. The region subtags 'AA', 'QM'-'QZ', 'XA'-'XZ', and 'ZZ' are
reserved for private use in language tags. These subtags
correspond to codes reserved by ISO 3166 for private use. These
codes MAY be used for private use region subtags (instead of
using a private-use subtag sequence). Please refer to
Section 2.5 4.4 for more information on private use subtags.

"de-Latn-CH"

"de-CH" represents German ('de') written using the Latin script

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('Latn') as used in Switzerland ('CH').

"sr-Latn-CS" represents Serbian ('sr') written using Latin script
('Latn') as used in Serbia and Montenegro ('CS').

"es-419" represents Spanish ('es') as used in the UN-defined Latin
America and Caribbean region ('419').

2.2.5 Variant Subtags

The following rules apply to the variant subtags:

1. Variant subtags, as a collection in the IANA registry, subtags are not associated with any external standard.
Variant subtags and their meanings are defined by the
registration process defined in Section 3.3.
o 3.4.

2. Variant subtags MUST follow all of the other defined subtags, but
precede any extension or private-use subtag sequences.
o

3. More than one variant MAY be used to form the language tag.
o

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4. Variant subtags MUST be registered with IANA according to the
rules in Section 3.3 3.4 of this document before being used to form
language tags. In order to distinguish variants from other types
of subtags, registrations must meet the following length and
content restrictions:
*

1. Variant subtags that begin with a letter (a-z, A-Z) MUST be
at least five characters long.
*

2. Variant subtags that begin with a digit (0-9) MUST be at
least four characters long.
* The maximum length of a variant subtag is eight characters
long.

"en-boont"

"en-scouse" represents the Boontling Scouse dialect of English.

"de-CH-1996" represents German as used in Switzerland and as written
using the spelling reform beginning in the year 1996 C.E.

2.2.6 Extension Subtags

The following rules apply to extensions:

1. Extension subtags are separated from the other subtags defined
in this document by a single-letter subtag ("singleton"). The
singleton MUST be one allocated to a registration authority via
the mechanism described in Section 3.4 3.6 and cannot be the letter
'x', which is reserved for private-use subtag sequences.
o

2. Note: Private-use subtag sequences starting with the singleton
subtag 'x' are described below.

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3. An extension MUST follow at least a primary language subtag.
That is, a language tag cannot begin with an extension.
Extensions extend language tags, they do not override or replace
them. For example, "a-value" is not a well-formed language tag,
while "de-a-value" is.
o

4. Each singleton subtag MUST appear at most one time in each tag
(other than as a private-use subtag). That is, singleton
subtags MUST NOT be repeated. For example, the tag "en-a-bbb-a-ccc" "en-a-bbb-a-
ccc" is invalid because the subtag 'a' appears twice.
o Note that
the tag "en-a-bbb-x-a-ccc" is valid because the second
appearance of the singleton 'a' is in a private use sequence.

5. Extension subtags MUST meet all of the requirements for the
content and format of subtags defined in this document.
o

6. Extension subtags MUST meet whatever requirements are set by the
document that defines their singleton prefix and whatever

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requirements are provided by the maintaining authority.
o

7. Each extension subtag MUST be from two to eight characters long
and consist solely of letters or digits, with each subtag
separated by a single '-'.
o

8. Each singleton MUST be followed by at least one extension
subtag. For example, the tag "tlh-a-b-foo" is invalid because
the first singleton 'a' is followed immediately by another
singleton 'b'.
o

9. Extension subtags MUST follow all language, extended language,
script, region and variant subtags in a tag.
o

10. All subtags following the singleton and before another singleton
are part of the extension. Example: In the tag "fr-a-Latn", the
subtag 'Latn' does not represent the script subtag 'Latn'
defined in the IANA Language Subtag Registry. Its meaning is
defined by the extension 'a'.
o

11. In the event that more than one extension appears in a single
tag, the tag SHOULD be canonicalized as described in
Section 2.4.1. 4.3.

For example, if the prefix singleton 'r' and the shown subtags were
defined, then the following tag would be a valid example:
"en-Latn-GB-boont-r-extended-sequence-x-private" "en-Latn-
GB-boont-r-extended-sequence-x-private"

2.2.7 Private Use Subtags

The following rules apply to private-use subtags:

1. Private-use subtags are separated from the other subtags defined
in this document by the reserved single-character subtag 'x'.
o

2. Private-use subtags MUST follow all language, extended language,
script, region, variant, and extension subtags in the tag.
Another way of saying this is that all subtags following the
singleton 'x' MUST be considered private use. Example: The
subtag 'US' in the tag "en-x-US" is a private use subtag.
o Unlike Extensions, a

3. A tag MAY consist entirely of private-use subtags.

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4. No source is defined for private use subtags. Use of private use
subtags is by private agreement and SHOULD NOT be considered part
of this document. only.

For example: Users who wished to utilize SIL Ethnologue for
identification might agree to exchange tags such as
"az-Arab-x-AZE-derbend". "az-Arab-x-AZE-

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derbend". This example contains two private-use subtags. The first
is 'AZE' and the second is 'derbend'.

2.2.8 Pre-Existing RFC 3066 Registrations

Existing IANA-registered language tags from RFC 1766 and/or RFC 3066
that are not defined by additions to this document
maintain their validity. IANA will maintain these tags in the
registry under either the "grandfathered" or "redundant" type. For
more information see
Appendix C. Section 3.7.

It is important to note that all language tags formed under the
guidelines in this document were either legal, well-formed tags or
were valid for potential registration
could have been registered under RFC 3066.

2.2.9 Possibilities for Registration

Possibilities for registration Classes of subtags include:

o Primary language subtags for languages not listed in ISO 639 that
are not variants Conformance

Implementations may wish to express their level of any listed or registered language, can be
registered. At conformance with
the time rules and practices described in this document was created there were no
examples document. There are
generally two classes of this form conforming implementations: "well-formed"
processors and "validating" processors. Claims of subtag. Before attempting conformance SHOULD
explicitly reference one of these definitions.

An implementation that claims to register a check for well-formed language subtag, there MUST be an attempt tags
MUST:

o Check that the tag and all of its subtags, including extension and
private-use subtags, conform to register the language
with ISO 639. No language ABNF or that the tag is on the
list of grandfathered tags.

o Check that singleton subtags will be registered for codes that exist in ISO 639-1 or ISO 639-2, which are under
consideration by identify extensions do not
repeat. For example, the ISO 639 maintenance or registration
authorities, or which have never been attempted for registration
with those authorities. If ISO 639 has previously rejected a
language for registration, it tag "en-a-xx-b-yy-a-zz" is reasonable not well-
formed.

Well-formed processors are strongly encouraged to assume implement the
canonicalization rules contained in Section 4.3.

An implementation that there
MUST be additional very compelling evidence of need before it will claims to be registered in the IANA registry (to the extent validating MUST:

o Check that it the tag is very
unlikely that any subtags will be registered well-formed.

o Specify the particular registry date for which the implementation
performs validation of this type). subtags.

o Dialect or other divisions or variations within Check that either the tag is a language, its
orthography, writing system, regional variation, grandfathered tag, or historical
usage may be registered as that all
language, script, region, and variant subtags. An example is subtags consist of valid
codes for use in language tags according to the
'scouse' subtag (the Scouse dialect IANA registry as
of English).

This document leaves the decision on what subtags are appropriate or
not to particular date specified by the registration process described implementation.

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o Specify which, if any, extension RFCs as defined in Section 3.3.

ISO 639 defines a maintenance agency for additions to 3.6
are supported, including version, revision, and changes date.

o For any such extensions supported, check that all subtags used in
that extension are valid.

o If the processor generates tags, it MUST do so in canonical form,
including any supported extensions, as defined in Section 4.3.

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the list of languages in ISO 639.

3. Registry Format and Maintenance

This agency is:

International Information Centre for Terminology (Infoterm)
Aichholzgasse 6/12, AT-1120
Wien, Austria
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72

ISO 639-2 section defines a the Language Subtag Registry and the maintenance agency
and update procedures associated with it.

The language subtag registry will be maintained so that, except for additions
extension subtags, it is possible to and changes
in validate all of the list of languages subtags that
appear in ISO 639-2. This agency is:

Library of Congress
Network Development and MARC Standards Office
Washington, D.C. 20540 USA
Phone: +1 202 707 6237 Fax: +1 202 707 0115
URL: http://www.loc.gov/standards/iso639

The maintenance agency for ISO 3166 (country codes) is:

ISO 3166 Maintenance Agency
c/o International Organization for Standardization
Case postale 56
CH-1211 Geneva 20 Switzerland
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49
URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html

The registration authority for ISO 15924 (script codes) is:

Unicode Consortium Box 391476
Mountain View, CA 94039-1476, USA
URL: http://www.unicode.org/iso15924

The Statistics Division a language tag under the provisions of this document or its
revisions or successors. In addition, the United Nations Secretariat maintains meaning of the Standard Country or Area Codes for Statistical Use and can various
subtags will be
reached at:

Statistical Services Branch
Statistics Division
United Nations, Room DC2-1620
New York, NY 10017, USA

Fax: +1-212-963-0623
E-mail: statistics@un.org
URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm

2.2.10 Classes unambiguous and stable over time. (The meaning of Conformance

Implementations may wish to express their level
private-use subtags, of conformance with course, is not defined by the rules and practices described in IANA registry.)

The registry defined under this document. There are

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generally two classes of conforming implementations: "well-formed"
processors and "validating" processors. Claims of conformance SHOULD
explicitly reference one document contains a comprehensive
list of these definitions.

An implementation that claims to check for well-formed language tags
MUST:
o Check that the tag and all of its subtags, including extension and
private-use subtags, conform to the ABNF or that the tag is on subtags valid in language tags. This allows
implementers a straightforward and reliable way to validate language
tags.

3.1 Format of the
list IANA Language Subtag Registry

The IANA Language Subtag Registry ("the registry") will consist of grandfathered tags.
o Check that singleton subtags a
text file that identify extensions do not
repeat. For example, the tag "en-a-xx-b-yy-a-zz" is not
well-formed.

Well-formed processors are strongly encouraged to implement machine readable in the
canonicalization rules contained format described in Section 2.4.1.

An implementation that claims to be validating MUST:
o Check that this
section, plus copies of the tag is well-formed.
o Specify registration forms approved by the particular registry date for which
Language Subtag Reviewer in accordance with the implementation
performs validation process described in
Section 3.4. With the exception of subtags.
o Check that either the tag is a registration forms for
grandfathered tag, or that all
language, script, region, and variant subtags consist of valid
codes redundant tags, no registration records will be
maintained for use in language tags according to the IANA registry as initial set of the particular date specified by the implementation.
o Specify which, if any, extension RFCs as defined subtags.

The registry will be in Section 3.4 a modified record-jar format text file [17].
Lines are supported, limited to 72 characters, including version, revision, and date.
o For any such extensions supported, check that all subtags used in
that extension whitespace.

Records are valid.
o If separated by lines containing only the processor generates tags, it MUST do so in canonical form,
including any supported extensions, sequence "%%"
(%x25.25).

Each field can be viewed as defined in Section 2.4.1.

2.3 Choice a single, logical line of Language Tag

One may occasionally be faced with several possible tags for ASCII
characters, comprising a field-name and a field-body separated by a
COLON character (%x3A). For convenience, the same
body field-body portion of text.

Interoperability
this conceptual entity can be split into a multiple-line
representation; this is best served when all users use the same language
tag in order to represent the same language. If an application has
requirements that make called "folding". The format of the rules here inapplicable, then that
application risks damaging interoperability. It registry
is STRONGLY
RECOMMENDED that users not define their own rules for language tag
choice.

Standards, protocols and applications that reference this document
normatively but apply different rules to described by the ones given following ABNF (per [7]):

registry = record *("%%" CRLF record)
record = 1*( field-name *SP ":" *SP field-body CRLF )
field-name = *(ALPHA/NUM/"-")
field-body = *(ASCCHAR/LWSP)
ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26
UNICHAR = "&#x" 2*6HEXDIG ";"

The sequence '..' (%x2E.2E) in this
section MUST specify how the procedure varies from the one given
here. a field-body denotes a range of

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1. Use as precise a tag as possible, but no more specific than is
justified. For example, 'de' might suffice for tagging an email
written in German, while "de-CH-1996" is probably unnecessarily
precise for such

values. Such a task.
2. Avoid using range represents all subtags of the same length that
are not important for distinguishing
content in an application. For example, alphabetically within that range, including the script
subtag in "en-Latn-US" is generally unnecessary, since nearly all
English texts are written in values explicitly
mentioned. For example 'a..c' denotes the Latin script values 'a', 'b', and it is generally
not important to filter out those few that are not.
3. Use the canonical subtag 'c'.

Characters from outside the IANA registry US-ASCII repertoire, as well as the
AMPERSAND character ("&", %x26) when it occurs in preference to
any of its aliases. For example, you should use 'he' for Hebrew a field-body are
represented by a "Numeric Character Reference" using hexadecimal
notation in preference to 'iw'.
4. You SHOULD NOT use the 'UND' (Undetermined) language subtag to
label content, even if style used by XML 1.0 [18] (see
<http://www.w3.org/TR/REC-xml/#dt-charref>). This consists of the language is unknown. Omitting
sequence "&#x" (%x26.23.78) followed by a hexadecimal representation
of the tag
is preferred. Some protocols character's code point in ISO/IEC 10646 [6] followed by a
closing semicolon (%x3B). For example, the EURO SIGN, U+20AC, would
be represented by the sequence "&#x20AC;". Note that the hexadecimal
notation may force you to give have between two and six digits.

All fields whose field-body contains a date value for use the language tag and "full-date"
format specified in RFC 3339 [14]. For example: "2004-06-28"
represents June 28, 2004 in the 'UND' subtag may be useful when matching
language tags Gregorian calendar.

The first record in certain situations.
5. You SHOULD NOT use the 'MUL' (Multiple) subtag if file contains the protocol
allows you to use multiple languages, as single field whose field-
name is "File-Date" and whose field-body contains the case for last
modification date of the
Content-Language header registry:

File-Date: 2004-06-28
%%

Subsequent records represent subtags in HTTP.
6. You SHOULD NOT use the same variant subtag registry. Each of the
fields in each record MUST occur no more than once within
a language tag. For example, you should not use
"en-US-boont-boont".

To ensure consistent backward compatibility, this document contains
several provisions to account for potential instability in once, unless otherwise
noted below. Each record MUST contain the
standards used to define following fields:

o 'Type'

* Type's field-value MUST consist of one of the subtags that make up language tags.
These provisions mean that no language following
strings: "language", "extlang", "script", "region", "variant",
"grandfathered", and "redundant" and denotes the type of tag created under or
subtag.

o Either 'Subtag' or 'Tag'

* Subtag's field-value contains the rules in
this document will become obsolete. In addition, tags that are in
canonical form will always be subtag being defined. This
field MUST only appear in canonical form.

2.4 Meaning records of the Language Tag

The language tag always defines a language as spoken (or written,
signed or otherwise signaled) by human beings for communication whose Type has one of
information to other human beings. Computer languages such as
programming languages are explicitly excluded.

If a language tag B
these values: "language", "extlang", "script", "region", or
"variant".

* Tag's field-value contains language tag A as a prefix, then B is
typically "narrower" or "more specific" than A. For example,
"zh-Hant-TW" is more specific than "zh-Hant". complete language tag. This relationship is not guaranteed field
MUST only appear in all cases: specifically,
languages that begin with the same sequence records whose Type has one of subtags are NOT
guaranteed to be mutually intelligible, although they may be. For
example, the tag "az" shares a prefix with both "az-Latn"
(Azerbaijani written using the Latin script) and "az-Cyrl"
(Azerbaijani written using the Cyrillic script). A person fluent in these values:
"grandfathered" or "redundant".

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one script may not be able to read

o Description

* Description's field-value contains a non-normative description
of the other, even though subtag or tag.

o Added

* Added's field-value contains the text
might be identical. Content tagged as "az" most probably is written
in just one script and thus might not be intelligible date the record was added to a reader
familiar with
the other script. registry.

The relationship between field 'Description' MAY appear more than one time. The
'Description' field must contain a description of the tag and the information it relates to is
defined by the standard describing being
registered written or transcribed into the context in which Latin script; it appears.
Accordingly, this section can only give possible examples of its
usage.
o For may also
include a single information object, the associated language tags
might be interpreted as the set of languages that description in a non-Latin script. The 'Description' field
is required used for
a complete comprehension of the complete object. Example: Plain
text documents.
o For an aggregation of information objects, the associated language
tags could identification purposes and should not be taken as to
represent the set of languages used inside components actual native name of that aggregation. Examples: Document stores and libraries.
o For information objects whose purpose is to provide alternatives, the associated language tags could or variation or to
be regarded in any particular language. Most descriptions are taken directly
from source standards such as a hint that the
content is provided ISO 639 or ISO 3166.

Note: Descriptions in several languages, and registry entries that one has to
inspect each of the alternatives in order correspond to find its language ISO 639,
ISO 15924, ISO 3166 or
languages. In this case, UN M.49 codes are intended only to indicate
the presence meaning of multiple tags might not
mean that one needs to be multi-lingual to get complete
understanding of the document. Example: MIME
multipart/alternative.
o In markup languages, such identifier as HTML and XML, language information
can be defined in the source standard at
the time it was added to each part of the document identified by registry. The description does not
replace the markup
structure (including content of the whole document itself). For example, one
could write <span lang="FR">C'est la vie.</span> inside a
Norwegian document; the Norwegian-speaking user could then access
a French-Norwegian dictionary source standard itself. The descriptions
are not intended to find out what be the marked section
meant. If English localized names for the user were listening to that document through a
speech synthesis interface, subtags.
Localization or translation of language tag and subtag descriptions
is out of scope of this formation could be used to signal document.

Each record MAY also contain the synthesizer to appropriately apply French text-to-speech
pronunciation rules to that span following fields:

o Canonical

* For fields of text, instead type 'language', 'extlang', 'script', 'region',
and 'variant', a canonical mapping of this record to a subtag
record of misapplying the Norwegian rules.

2.4.1 Canonicalization same 'Type'.

* For fields of Language Tags

Since a particular language tag may be used in many processes,
language tags SHOULD always be created or generated in type 'grandfathered' and 'redundant', a canonical
form.

A
mapping to a complete language tag is in canonical form when:
1. The tag is well-formed according the rules in Section 2.1 and
Section 2.2.
2. None of tag.

o Deprecated

* Deprecated's field-value contains the subtags in date the record was
deprecated.

o Recommended-Prefix

* Recommended-Prefix's field-value contains a language tag has a canonical_value
mapping in the IANA registry (see Section 3.1). Subtags with a
canonical_value mapping MUST
which this subtag may be replaced with their mapping in used to form a new language tag,

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order to canonicalize

perhaps with other subtags as well. This field MUST only
appear in records whose 'Type' field-value is 'variant' or
'extlang'. For example, the tag.
3. If more than one extension subtag sequence exists, 'Recommended-Prefix' for the extension
sequences are ordered into case-insensitive ASCII order by
singleton subtag.

Example: The language tag "en-A-aaa-B-ccc-bbb-x-xyz"
variant 'scouse' is in canonical
form, 'en', meaning that the tags "en-scouse" and
"en-GB-scouse" might be appropriate while "en-B-ccc-bbb-A-aaa-X-xyz" is well-formed but not in
canonical form.

Example: The language the tag "en-NH" (English "is-scouse"
is not.

o Comments

* Comments contains additional information about the subtag, as used in
deemed appropriate for understanding the New
Hebrides) is not canonical because registry and
implementing language tags using the 'NH' subtag has or tag.

o Suppress-Script

* Suppress-Script contains a canonical
mapping script subtag that SHOULD NOT be
used to 'VU' (Vanuatu).

Note: Canonicalization of form language tags does not imply anything about with the use of upper or lowercase letter in subtags as described associated primary language
subtag. This field MUST only appear in records whose 'Type'
field-value is 'language'. See Section 2.1. All comparisons MUST 4.1.

The field 'Canonical' SHALL NOT be performed in a case-insensitive
manner.

Note: the value "--" added to any record already in the canonical_value
registry. The field 'Canonical' SHALL NOT be modified except for
records of the registry
indicates type "grandfathered": therefore a tag or subtag that has been deprecated and for which whose record
contains no
replacement or canonical equivalent has been assigned. Validating
processors SHOULD NOT generate tags that include these values.

An extension MUST define any relationships that may exist between mapping when the
various subtags record is created is a
canonical form and will remain so.

The 'Canonical' field in the extension records of type "grandfathered" and thus MAY define an alternate
canonicalization scheme
"redundant" contains whole language tags that are STRONGLY
RECOMMENDED for use in place of the extension's subtags. Extensions MAY
define how record's value. In many cases
the order mappings were created by deprecation of the extension's subtags are interpreted. For
example, an extension could define that its subtags are in canonical
order when tags during the subtags are placed into ASCII order: that is,
"en-a-aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension
might define that
period before this document was adopted. For example, the order tag "no-
nyn" was deprecated in favor of the subtags influences their semantic
meaning (so ISO 639-1 defined language code
'nn'.

Note that a record that "en-b-ccc-bbb-aaa" has a different value from
"en-b-aaa-bbb-ccc"). However, extension specifications SHOULD 'Canonical' field MUST have a
'Deprecated' field also (although the converse is not true).

The field 'Deprecated' MAY be
designed so that they are tolerant of added to any record via the typical processes maintenance
process described in Section 3.2 or via the registration process
described in Section 3.4.

2.5 Considerations for Private Use Subtags

Private-use subtags require private agreement between Usually the parties
that intend addition of a 'Deprecated'
field is due to use or exchange language tags that use them and great
caution should be used in employing them in content or protocols
intended for general use. Private-use subtags are simply useless for
information exchange without prior arrangement.

The value and semantic meaning the action of private-use tags and one of the subtags
used within standards bodies, such as
ISO 3166, withdrawing a language tag are code. In some historical cases it may not defined by this document.

The use of subtags defined
have been possible to reconstruct the original deprecation date.
For these cases, an approximate date appears in the IANA registry as having registry.
Although valid in language tags, subtags and tags with a specific 'Deprecated'
field are deprecated and validating processors SHOULD NOT generate
these subtags. Note that a record that contains a 'Deprecated' field
and no corresponding 'Canonical' field has no replacement mapping.

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private use meaning convey

The field 'Recommended-Prefix' MAY appear more information that a purely private use
tag prefixed by the singleton subtag 'x'. For applications than once per record.
Additional fields of this
additional information may be useful.

For example, the region subtags 'AA', 'ZZ' and in the ranges
'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) may type MAY be used added to form a record via the
registration process. The field-value of of this field consists of a
language tag. A tag such that is RECOMMENDED for use as "zh-Hans-XQ" conveys a
great deal of public, interchangeable information about prefix for this subtag.
For example, the language
material (that it is Chinese in variant subtag 'scouse' has a recommended prefix of
"en". This means that tags starting with the simplified Chinese script prefix "en-" are most
appropriate with this subtag, so "en-Latn-scouse" and is
suitable for some geographic region 'XQ'). While "en-GB-scouse"
are both acceptable, while the precise
geographic region tag "fr-scouse" is not known outside probably an
inappropriate choice.

The field of private agreement, the tag
conveys far type Recommended-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 information than an opaque tag such as "x-someLang",
which contains no information about the language subtag once per record. This
field MAY be inserted or script
subtag outside of changed via the private agreement.

However, in some cases content tagged with private use subtags may
interact with other systems in a different registration process and possibly unsuitable
manner compared to tags that use opaque, privately defined subtags,
so the choice no
guarantee of stability is provided. The content of this field is not
restricted, except by the best approach may depend on need to register the information, the
suitability of the request, and by reasonable practical size
limitations. Long screeds about a particular
domain subtag are frowned
upon.

The field 'Suppress-Script' MUST only appear in question.

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3. IANA Considerations records whose 'Type'
field-value is 'language'. This section deals with the processes and requirements necessary field may appear at most one time in
a record. This field indicates a script used to
maintain write the registry
overwhelming majority of subtags and extensions documents for use in language
tags as defined by this document and in accordance with the
requirements of RFC 2434 [15].

The given language subtag registry will be maintained so that, except for
extension subtags, it is possible and which
therefore adds no distinguishing information to validate a language tag. For
example, virtually all of Icelandic documents are written in the subtags that
appear Latin
script, making the subtag 'Latn' redundant in a language tag under the provisions tag "is-Latn".

For examples of registry entries and their format, see Appendix C.

3.2 Maintenance of this document or its
revisions or successors. In addition, the meaning Registry

Maintenance of the various
subtags registry requires that as new codes are assigned
by ISO 639, ISO 15924, and ISO 3166, the Language Subtag Reviewer
will be unambiguous evaluate each assignment, determine whether it conflicts with
existing registry entries, and stable over time. (The meaning of
private-use subtags, of course, is not defined by submit the information to IANA registry.)

The registry defined under for
inclusion in the registry. If an assignment takes place and the
Language Subtag Reviewer does not do this document contains in a comprehensive
list of all of timely manner, then
any interested party may use the subtags valid procedure in language tags. This allows
implementers a straightforward and reliable way Section 3.4 to validate language
tags.

3.1 Format of register
the IANA Language Subtag Registry appropriate update.

Note: The IANA Language Subtag Registry will consist redundant and grandfathered entries together are the
complete list of a text file tags registered under RFC 3066 [23]. The redundant
tags are those that is
machine readable in can now be formed using the format described subtags defined in this section, plus copies
of the registration forms approved by
the Language Subtag Reviewer in
accordance registry together with the process described rules of Section 2.2. The
grandfathered entries are those that can never be legal under those
same provisions. The items in both lists are permanent and stable,

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although grandfathered items may be deprecated over time. Refer to
Section 3.3. With 3.7 for more information.

RFC 3066 tags that were deprecated prior to the
exception adoption of this
document are part of the registration forms for list of grandfathered tags and redundant
tags, no registration records will be maintained their
component subtags were not included as registered variants (although
they remain eligible for registration). For example, the initial set
of subtags.

Each record tag "art-
lojban" was deprecated in the subtag registry will consist of a series favor of fields
separated by the symbol "|" (%x7D) and terminated by a newline. Text
appearing after language subtag 'jbo'.

The Language Subtag Reviewer MUST ensure that new subtags meet the symbol "#" (%x23) contains comments. Whitespace
surrounding fields
requirements in the file is ignored. Section 4.1 or submit an appropriate alternate subtag
as described in that section. If a field contains more
than one value, change or addition to the values are separated by semicolons (%x3B).

There
registry is required, the Language Subtag Reviewer will prepare the
complete record, including all fields, and forward it to IANA for
insertion into the registry. If this represents a single date new subtag, then
the message will indicate that this represents an INSERTION of a
record. If this represents a change to an existing subtag, then the
message must indicate that this represents a MODIFICATION, as shown
in the following example:

LANGUAGE SUBTAG MODIFICATION
File-Date: 2005-01-02
%%
Type: variant
Subtag: nedis
Description: Natisone dialect
Description: Nadiza dialect
Added: 2003-10-09
Recommended-Prefix: sl
Comments: This is a comment shown
as an example.
%%

Figure 4

Whenever an entry is created or modified in the registry, the 'File-
Date' record at the start of the file which
indicates registry is updated to reflect the
most recent modification date of the file. It has two
fields: the type field is "date", and the second field is the
modification date, in the "full-date" format specified in RFC 3339
[20]. For example: 2004-06-28 represents June 28, 2004 [14] "full-date"
format.

3.3 Stability of IANA Registry Entries

The stability of entries and their meaning in the
Gregorian calendar:
date | 2004-06-28 registry is
critical to the long term stability of language tags. The fields in each subtag record, rules in order, are:
type| subtag| description| date| canonical_value|
recommended_prefix # comments
this section guarantee that a specific language tag's meaning is
stable over time and will not change and that the choice of language
tag for specific content is also stable over time.

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o The character "vertical line" ("|", %x7D) delimits each

These rules specifically deal with how changes to codes (including
withdrawal and deprecation of codes) maintained by ISO 639, ISO
15924, ISO 3166, and UN M.49 are reflected in the
fields.
o Empty fields (and their separators) at the end of IANA Language
Subtag Registry. Assignments to the record may
be omitted. IANA Language Subtag Registry
MUST follow the following stability rules:

o Leading or trailing whitespace Values in each field is not part of the
content. fields 'Type', 'Subtag', 'Tag', 'Added' and
'Canonical' MUST NOT be changed and are guaranteed to be stable
over time.

o When the type is "grandfathered" or "redundant", then Values in the subtag 'Description' field is actually MUST NOT be changed in a whole tag.
o The "recommended_prefix" field is empty, except where way
that would invalidate previously-existing tags. They may be
broadened somewhat in scope, changed to add information, or
adapted to the type is
"variant" most common modern usage. For example, countries
occasionally change their official names: an historical example of
this would be "Upper Volta" changing to "Burkina Faso".

o The "comments" Values in the field is optional and appears only at 'Recommended-Prefix' MAY be added via the end of a
record, following a "number sign" ("#", %x23).
registration process.

o The sequence '..' denotes a range of values. Such a range
represents all subtags of Values in the same length that are alphabetically
within that range, including field 'Recommended-Prefix' MAY be modified, so long
as the values explicitly mentioned. For
example 'a..c' denotes modifications broaden the values 'a', 'b', and 'c'.

The field 'type' MUST consist set of recommended prefixes.
That is, a recommended prefix MAY be replaced by one of its own
prefixes. For example, the following strings:
"language", "extlang", "script", "region", "variant",
"grandfathered", and "redundant" and denotes prefix "en-US" could be replaced by
"en", but not by the type of subtag (or
tag, ranges "en-Latn", "fr", or "en-US-boont".

o Values in the case of "grandfathered" and "redundant").

The field 'subtag' contains the subtag being defined. 'Recommended-Prefix' MUST NOT be removed.

o The field 'description' contains a description of 'Comments' MAY be added, changed, modified, or removed
via the subtag
transcribed into ASCII.

Note: Descriptions registration process or any of the processes or
considerations described in registry entries that correspond to this section.

o The field 'Suppress-Script' MAY be added or removed via the
registration process.

o Codes assigned by ISO 639, ISO 15924, and 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 time it was added to do not
conflict with existing subtags of the registry. The description does associated type and whose
meaning is not
replace the content same as an existing subtag of the source standard itself. The descriptions same type are not intended to be
entered into the English localized names IANA registry as new records and their value is
canonical for the subtags
and localization meaning assigned to them.

o Codes assigned by ISO 639, ISO 15924, or translation of ISO 3166 that are
withdrawn by their respective maintenance or registration
authority remain valid in language tag and subtag
descriptions is out of scope of this document. tags. The field 'date' contains the date the record was added registration process
MAY be used to add a note indicating the
registry in withdrawal of the "full-date" format specified in RFC 3339 [20]. For
example: 2004-06-28 represents June code by
the respective standard.

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o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that do not
conflict with existing subtags of the Gregorian
calendar. associated type but which
represent the same meaning as an existing subtag of that type are
entered into the IANA registry as new records. The field
'canonical value' represents a canonical mapping of this for that record to a MUST contain the existing subtag record
of the same 'type', except for records meaning

Example If ISO 3166 were to assign the code 'IM' to represent the
value "Isle of
type "grandfathered" Man" (represented in the IANA registry by the UN
M.49 code '833'), '833' remains the canonical subtag and "redundant". This field SHALL NOT 'IM'
would be
modified (except for records of type "grandfathered"): therefore a
subtag whose record contains no canonical mapping when the record is
created is assigned '833' as a canonical form and will remain so. The 'canonical
value' field in records of type "grandfathered" and "redundant"

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contain whole language value. This prevents
tags that are STRONGLY RECOMMENDED for use in
place of the record's value. In many cases canonical form from becoming non-canonical.

Example If the mappings tag 'enochian' were created
by deprecation of the tags during the period before this document was
adopted. For example, registered as a primary
language subtag and ISO 639 subsequently assigned an alpha-3
code to the tag "no-nyn" was deprecated in favor of same language, the new ISO 639-1 defined language 639 code 'nn'.

The value "--" in the 'canonical value' field means that would be
entered into the tag or IANA registry as a subtag has been deprecated and that no replacement value has been
assigned. For example, the "region" with a canonical
mapping to 'enochian'. The new ISO code 'BQ' (British Antarctic
Territory) was withdrawn can be used, but it is
not canonical.

o Codes assigned by ISO 639, ISO 15924, or ISO 3166 in 1979. Although valid in
language tags, it is deprecated and validating processors SHOULD NOT
generate this subtag.

The field 'recommended prefix' is for use that conflict
with registered variants
and contains a semicolon separated list existing subtags of language-ranges considered
most appropriate for use with this subtag. Additional values can the associated type MUST NOT be
added to this field for variants only via entered
into the registry. The following additional registration.
Other modification of this field (such as removing or changing
values) considerations apply:

* For ISO 639 codes, if the newly assigned code's meaning is not permitted.

The field 'comments' may contain additional information about
represented by a subtag in the
subtag, IANA registry, the Language
Subtag Reviewer, as deemed appropriate described in Section 3.4, shall prepare a
proposal for understanding entering in the IANA registry and
implementing as soon as practical
a registered language tags using subtag as an alternate value for the various subtags. These values
can new
code. The form of the registered language subtag will be changed via at
the registration process and no guarantee discretion of
stability is provided.

# IANA the Language Subtag Registry
# This registry lists Reviewer and must conform
to other restrictions on language subtags in this document.

* For all valid subtags for language tags
# created under RFC XXXX.
date| 2004-08-07

# language codes: ISO 639 and registered codes

# whose meaning is derived from an external
standard (i.e. ISO 639-1 (alpha-2) codes
language| aa| Afar| 2004-07-06| |
language| ab| Abkhazian| 2004-07-06| |
language| ae| Avestan| 2004-07-06| |
language| he| hebrew| 2004-06-28| |
language| iw| hebrew| 2004-06-28| he | #note mapping
language| qaa..qtz| PRIVATE USE| 2004-07-06| |
language| raj| Rajasthani| 2004-07-06| |
language| seuss| Hypothetical Language| 2005-04-01 | |# registered language

# script codes: 639, ISO 15924

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# ISO 3166-1 alpha-2 codes

region| AA| PRIVATE USE| 2004-08-01| |
region| AD| Andorra| 2004-07-06| |
region| AE| United Arab Emirates| 2004-07-06| |
region| AF| Afghanistan| 2004-07-06| |
region| BQ| British Antarctic Territory | 2004-07-06 | -- | # deprecated 1979
region| CS| Serbia and Montenegro| 2003-07-23| |
region| YU| Yugoslavia| 2004-06-28| |

# United Nations M.49 numeric codes
region| 001| World| 2004-07-06| |
region| 002| Africa| 2004-07-06| |
region| 003| North America| 2004-07-06| |
region| 005| South America| 2004-07-06| |
region| 200| Czechoslovakia| 2004-07-06| | #formerly used M.49), if a
new meaning is assigned to an existing code CS

## registered variants

# grandfathered from RFC 3066

# redundant
# that code, then the meaning for the
associated subtag MAY be changed to match. The following codes were registered meaning of a
subtag MUST NOT be narrowed, however, as complete tags, but this can now be
# composed of registered subtags and do not require registration.

Figure 2: Example an
unknown proportion of the Registry Format

Maintenance existing uses of a subtag becoming
invalid. Note: ISO 639 MA/RA has adopted a similar stability
policy.

* For ISO 15924 codes, if the registry requires that as new codes are newly assigned code's meaning is
not represented by ISO 639, ISO 15924, and ISO 3166, a subtag in the IANA registry, the Language
Subtag Reviewer
will evaluate each assignment, determine whether it conflicts with
existing registry entries, and submit Reviewer, as described in Section 3.4, shall prepare a
proposal for entering in the information to IANA registry as soon as practical
a registered variant subtag as an alternate value for
inclusion in the registry. new

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Note:

code. The redundant and grandfathered entries together are the
complete list form of tags the registered under RFC 3066 [18]. The redundant
tags are those that can now variant subtag will be formed using at the
discretion of the Language Subtag Reviewer and must conform to
other restrictions on variant subtags defined in
Section 2.2. The grandfathered entries are those that can never be
legal under those same provisions. The items in both lists are
permanent and stable, although grandfathered items may be deprecated
over time. Refer to Appendix C for more information.

RFC 3066 tags that were deprecated prior to the adoption of this
document are part of the list of grandfathered tags and their
component subtags were not included as registered variants (although
they remain eligible for registration). document.

* For example, ISO 3166 codes, if the tag
"art-lojban" was deprecated in favor of newly assigned code's meaning is
associated with the language same UN M.49 code as another 'region'
subtag, then the existing region subtag 'jbo'.

The Language Subtag Reviewer MUST ensure remains as the
canonical entry for that region and no new subtags meet entry is created. A
comment MAY be added to the
requirements in Section 2.3 or submit an appropriate alternate existing region subtag
as described in that section. She or he will use indicating
the following form relationship to submit this information:

LANGUAGE SUBTAG REGISTRATION FORM (NEW RECORD)
Record Text:
Type:
Subtag:
Description:
Date:
Canonical Mapping:
Recommended Prefix:
Comments:

Figure 3

The field 'record text' contains the exact record new ISO 3166 code.

* For ISO 3166 codes, if the newly assigned code's meaning is
associated with a UN M.49 code that IANA is to
insert into not represented by an
existing region subtag, then then the Language Subtag Registry. The contents of the
remaining fields must exactly match those Reviewer,
as described in this field.

Whenever Section 3.4, shall prepare a proposal for
entering the appropriate numeric UN country code as an entry is created or modified in
the registry, the 'date'
record at the start of the registry IANA registry.

* For ISO 3166 codes, if there is updated to reflect no associated UN numeric code,
then the most
recent modification date in Language Subtag Reviewer SHALL petition the RFC 3339 [20] "full-date" format.

3.2 Stability of IANA Registry Entries

The stability UN to
create one. If there is no response from the UN within ninety
days of entries and their meaning the request being sent, the Language Subtag Reviewer
shall prepare a proposal for entering in the IANA registry is
critical to as
soon as practical a registered variant subtag as an alternate
value for the long term stability of language tags. new code. The rules in
this section guarantee that a specific language tag's meaning is
stable over time and form of the registered variant
subtag will not change and that be at the choice discretion of language
tag for specific content the Language Subtag
Reviewer and must conform to other restrictions on variant
subtags in this document. This situation is also stable over time.

These rules specifically deal with how changes very unlikely to codes (including

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withdrawal and deprecation
ever occur.

o Stability provisions apply to grandfathered tags with this
exception: should all of codes) maintained by ISO 639, ISO
15924, ISO 3166, and UN M.49 are reflected the subtags in a grandfathered tag become
valid subtags in the IANA Language
Subtag Registry. Assignments to registry, then the IANA Language Subtag Registry grandfathered tag
MUST follow be marked as redundant. Note that this will not affect
language tags that match the following stability rules:
o Values grandfathered tag, since these tags
will now match valid generative subtag sequences. For example, if
the subtag 'gan' in the fields 'type', 'subtag', 'date' and 'canonical
value' MUST NOT be changed and are guaranteed language tag "zh-gan" were to be stable over
time.
o Values in
registered as an extended language subtag, then the 'description' field MUST NOT be changed in a way
that grandfathered
tag "zh-gan" would invalidate previously-existing tags. They may be
broadened somewhat in scope, changed to add information, deprecated (but existing content or
adapted to the most common modern usage. For example, countries
occasionally change their official names: an historical example of
this
implementations that use "zh-gan" would remain valid).

3.4 Registration Procedure for Subtags

The procedure given here MUST be "Upper Volta" changing used by anyone who wants to "Burkina Faso".
o Values use a
subtag not currently in the field 'recommended prefix' MAY IANA Language Subtag Registry.

Only subtags of type 'language' and 'variant' will be added via the considered for

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independent registration process.
o Values in the field 'recommended prefix' MAY be modified, so long
as the modifications broaden the set of recommended prefixes.
That is, a recommended prefix MAY be replaced by one new subtags. Handling of its own
prefixes. For example, subtags
required for stability and subtags required to keep the prefix "en-US" could be replaced by
"en", but not by registry
synchronized with ISO 639, ISO 15924, ISO 3166, and UN M.49 within
the ranges "en-Latn", "fr", or "en-US-boont".
o Values limits defined by this document are described in the field 'recommended prefix' MUST NOT be removed.
o The field 'comments' Section 3.2.
Stability provisions are described in Section 3.3.

This procedure MAY also be added, changed, modified, used to register or removed
via alter the registration process or any of information
for the processes "Description", "Comments", "Deprecated", or
considerations "Recommended-
Prefix" fields in a subtag's record as described in this section.
o Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not
conflict with existing subtags of the associated type and whose
meaning is not Figure 7.
Changes to all other fields in the same as IANA registry are NOT permitted.

Registering a new subtag or requesting modifications to an existing
tag or subtag of starts with the same type are
entered into requster filling out the IANA registry as new records and their value registration
form reproduced below. Note that each response is
canonical for not limited in
size and should take the meaning assigned room necessary to them.
o Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are
withdrawn by their respective maintenance or registration
authority remain valid adequately describe the
registration. The fields in the "Record Requested" section SHOULD
follow the requirements in Section 3.1.

LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester:
2. E-mail address of requester:
3. Record Requested:

Type:
Subtag:
Description:
Recommended-Prefix:
Canonical:
Deprecated:
Suppress-Script:
Comments:

4. Intended meaning of the subtag:
5. Reference to published description
of the language tags. (book or article):
6. Any other relevant information:

Figure 5

The subtag registration process
MAY form MUST be used sent to add
<ietf-languages@iana.org> for a note indicating the withdrawal two week review period before it can
be submitted to IANA. (This is an open list. Requests to be added
should be sent to <ietf-languages-request@iana.org>.)

Variant subtags are generally registered for use with a particular
range of language tags. For example, the code by
the respective standard.
o Codes assigned by ISO 639, ISO 15924, or ISO 3166 subtag 'scouse' is intended
for use with language tags that do not
conflict start with existing subtags of the associated type but which
represent the same meaning as an existing primary language
subtag "en", since Scouse is a dialect of that type are
entered into the IANA registry as new records. The field
'canonical value' for that record MUST contain English. Thus the existing subtag
of

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'scouse' could be included in tags such as "en-Latn-scouse" or "en-
GB-scouse". This information is stored in the same meaning
Example If ISO 3166 were to assign "Recommended-Prefix"
field in the code 'IM' registry. Variant registration requests are REQUIRED to represent the
value "Isle of Man" (represented
include at least one "Recommended-Prefix" field in the IANA registry by the UN
M.49 code '833'), '833' remains the canonical registration
form.

Any subtag and 'IM'
would MAY be assigned '833' as incorporated into a canonical value. This prevents variety of language tags,
according to the rules of Section 2.1, including tags that are in canonical form from becoming non-canonical.

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Example If do not
match any of the recommended prefixes of the tag 'enochian' were registered as subtag.
(Note that this is probably a primary
language subtag poor choice.) This makes validation
simpler and ISO 639 subsequently assigned an alpha-3
code to thus more uniform across implementations, and does not
require the same language, registration of a separate subtag for the new ISO 639 code would same purpose
and meaning but a different recommended prefix.

The recommended prefixes for a given registered subtag will be
entered into
maintained in the IANA registry as a subtag with a canonical
mapping guide to 'enochian'. The new ISO code can be used, but usage. If it is
not canonical.
o Codes assigned by ISO 639, ISO 15924, or ISO 3166
necessary to add an additional prefix to that conflict
with list for an existing subtags of the associated type MUST NOT
language tag, that can be entered
into the registry. The following done by filing an additional considerations apply:
* For ISO 639 codes, if registration
form. In that form, the newly assigned code's meaning "Any other relevant information:" field
should indicate that it is not
represented by a subtag in the IANA registry, the Language
Subtag Reviewer, as described in Section 3.3, shall prepare addition of an additional recommended
prefix.

Requests to add a
proposal for entering in the IANA registry as soon as practical recommended prefix to a registered language subtag as an alternate value for the new
code. The form of the registered language subtag that imply a
different semantic meaning will probably be at
the discretion of the Language Subtag Reviewer and must conform
to other restrictions on language subtags in this document.
* rejected. For all subtags whose meaning is derived from an external
standard (i.e. ISO 639, ISO 15924, ISO 3166, or UN M.49), if example, a
new meaning is assigned
request to an existing code and add the new meaning
broadens prefix "de" to the meaning of subtag 'nedis' so that code, then the tag
"de-nedis" represented some German dialect would be rejected. The
'nedis' subtag represents a particular Slovenian dialect and the
additional registration would change the semantic meaning for assigned to
the
associated subtag. A separate subtag MAY should be changed to match. proposed instead.

The meaning of 'Description' field must contain a
subtag MUST NOT be narrowed, however, as this can result in an
unknown proportion description of the existing uses of a subtag becoming
invalid. Note: ISO 639 MA/RA has adopted a similar stability
policy.
* For ISO 15924 codes, if tag being
registered written or transcribed into the newly assigned code's meaning is
not represented by Latin script; it may also
include a subtag description in a non-Latin script. Non-ASCII characters
must be escaped using the IANA registry, the Language
Subtag Reviewer, as syntax described in Section 3.3, shall prepare a
proposal 3.1. The
'Description' field is used for entering in identification purposes and should
not be taken to represent the IANA registry as soon as practical
a registered variant subtag as an alternate value for actual native name of the new
code. The form language or
variation or to be in any particular language.

While the 'Description' field itself is not guaranteed to be stable
and errata corrections may be undertaken from time to time, attempts
to provide translations or transcriptions of entries in the registered variant subtag registry
itself will probably be at frowned upon by the
discretion community or rejected
outright, as changes of this nature may impact the provisions in
Section 3.3.

The Language Subtag Reviewer and must conform is responsible for responding to
other restrictions on variant
requests for the registration of subtags in this document.
* For ISO 3166 codes, if through the newly assigned code's meaning registration
process and is
associated with appointed by the same UN M.49 code as another 'region'
subtag, then IESG.

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When the existing region subtag remains as two week period has passed the
canonical entry for that region and no new entry is created. A
note MAY Language Subtag Reviewer
either forwards the record to be added inserted or modified to
iana@iana.org according to the existing region subtag indicating procedure described in Section 3.2, or
rejects the
relationship request because of significant objections raised on the
list or due to problems with constraints in this document (which
should be explicitly cited). The reviewer may also extend the new ISO 3166 code.
* For ISO 3166 codes, if review
period in two week increments to permit further discussion. The
reviewer must indicate on the newly assigned code's meaning list whether the registration has been
accepted, rejected, or extended following each two week period.

Note that the reviewer can raise objections on the list if he or she
so desires. The important thing is
associated with a UN M.49 code that the objection must be made
publicly.

The applicant is not represented free to modify a rejected application with
additional information and submit it again; this restarts the two
week comment period.

Decisions made by an
existing region subtag, then then the Language Subtag Reviewer,
as described in Section 3.3, shall prepare a proposal for
entering reviewer may be appealed to the appropriate numeric UN country code IESG [RFC 2028]
[9] under the same rules as an entry other IETF decisions [RFC 2026] [8].

All approved registration forms are available online in the IANA registry.
* For ISO 3166 codes, if there is no associated UN numeric code,
then directory
http://www.iana.org/numbers.html under "languages".

Updates or changes to existing records, including previous
registrations, follow the same procedure as new registrations. The
Language Subtag Reviewer SHALL petition the UN to

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create one. If decides whether there is no response from consensus to update
the UN within ninety
days of registration following the request being sent, two week review period; normally
objections by the Language Subtag Reviewer
shall prepare a proposal for entering original registrant will carry extra weight in the IANA registry as
soon as practical
forming such a registered variant subtag as an alternate
value for the new code. The form of the registered variant
subtag consensus.

Registrations are permanent and stable. Once registered, subtags
will not be at the discretion of removed from the Language Subtag
Reviewer registry and must conform will remain the canonical
method of referring to other restrictions on variant
subtags in this document. a specific language or variant. This situation is very unlikely to
ever occur.
o Stability provisions
provision does not apply to grandfathered tags with this
exception: should all tags, which may become
deprecated due to registration of subtags. For example, the subtags in a grandfathered tag become
valid subtags
"i-navajo" is deprecated in favor of the IANA registry, then the grandfathered tag
MUST be marked as redundant. Note that this will not affect
language tags that match the grandfathered tag, since these tags
will now match valid generative ISO 639-1 based subtag sequences. For example, if 'nv'.

Note: The purpose of the subtag 'gan' "published description" in the language tag "zh-gan" were registration
form is intended as an aid to be people trying to verify whether a
language is registered as or what language or language variation a
particular subtag refers to. In most cases, reference to an extended
authoritative grammar or dictionary of that language subtag, then the grandfathered
tag "zh-gan" would will be deprecated (but existing content useful;
in cases where no such work exists, other well known works describing
that language or
implementations in that use "zh-gan" would remain valid).

Language tags formed under RFC 3066 that use the region language may be appropriate. The subtag 'CS'
were ambiguous, since tags produced before 2003 used that code for
the (now dissolved) country Czechoslovakia. ISO 3166 assigned this
code
reviewer decides what constitutes "good enough" reference material.
This requirement is not intended to exclude particular languages or
dialects due to the country Serbia and Montenegro in 2003 and this draft
makes that size of the canonical value for this subtag. To form speaker population or lack of a

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standardized orthography. Minority languages will be considered
equally on their own merits.

3.5 Possibilities for Registration

Possibilities for registration of subtags or information about
subtags include:

o Primary language
tag subtags for the region Czechoslovakia, the UN M.49 code '200' is included languages not listed in the registry. As a practical matter, applications that encounter
the RFC 3066 tag "cs-CS" or "sk-CS" MAY wish to convert ISO 639 that to
"cs-200" or "sk-200" (or use one
are not variants of the successor region subtags,
such as 'CZ' any listed or 'SK'), since that is registered language can be
registered. At the most likely interpretation.

3.3 Registration Procedure for Subtags

The procedure given here time this document was created there were no
examples of this form of subtag. Before attempting to register a
language subtag, there MUST be used by anyone who wants an attempt to use a
subtag not currently in register the IANA Language Subtag Registry.

Only primary language and variant
with ISO 639. No language subtags will be considered for
independent registration. (Subtags required registered for stability and
subtags required to keep the registry synchronized with ISO 639, codes
that exist in ISO
15924, 639-1 or ISO 3166, and UN M.49 within the limits defined by this
document 639-2, which are under
consideration by the only exceptions to this. See Section 3.2.)

This procedure MAY also be used to register ISO 639 maintenance or alter the information
for the "description", "note", registration
authorities, or "recommended prefix" fields in which have never been attempted for registration
with those authorities. If ISO 639 has previously rejected a
subtag's record as described in Figure 2. Changes
language for registration, it is reasonable to all other
fields assume that there
MUST be additional very compelling evidence of need before it will
be registered in the IANA registry are NOT permitted.

If registering a new language subtag, the process starts by filling

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out (to the registration form reproduced below. Note extent that each response it is not limited in size and should take the room necessary to
adequately describe the registration.

LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester:
2. E-mail address of requester:
3. Subtag to very
unlikely that any subtags will be registered:
4. Type registered of Registration:
[ ] language
[ ] this type).

o Dialect or other divisions or variations within a language, its
orthography, writing system, regional or historical usage,
transliteration or other transformation, or distinguishing
variation may be registered as variant
5. Description of subtags. An example is the
'scouse' subtag (in English or transcribed into ASCII):
6. Intended meaning (the Scouse dialect of the subtag:
7. Recommended prefix(es) English).

o The addition or maintenance of subtag (for variants):
8. Native name fields (generally of the language an
informational nature) in Tag or variation (transcribed into ASCII):
9. Reference Subtag records as described in
Section 3.1 and subject to published description of the language (book or article):
10. Any other relevant information:

Figure 4

The subtag registration form MUST be sent to
<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
should be sent to <ietf-languages-request@iana.org>.)

Variant subtags are generally registered for use with a particular
range stability provisions in
Section 3.3. This includes descriptions, recommended prefixes,
comments, deprecation of language tags. For example, the subtag 'boont' is intended
for use with language tags that start with obsolete items, or the primary language
subtag "en", since Boontling is a dialect addition of English. Thus the
subtag 'boont' could be included in tags such as "en-Latn-boont" script
or
"en-US-boont". This extlang information is stored in the "recommended
prefix" field in to primary language subtags.

This document leaves the registry and MUST be provided in decision on what subtags or changes to
subtags are appropriate (or not) to the registration form.

Any subtag MAY be incorporated into a variety of process
described in Section 3.4.

Note: four character primary language tags,
according subtags are reserved to allow
for the rules of Section 2.1, including tags that do not
match any of the recommended prefixes possibility of alpha4 codes in some future addition to 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
ISO 639 family of standards.

ISO 639 defines a separate subtag maintenance agency for the same purpose additions to and meaning but a different recommended prefix.

The recommended prefixes for a given registered subtag will be
maintained changes in
the IANA registry as a guide to usage. If it is
necessary to add an additional prefix to that list for an existing
language tag, that can be done by filing an additional registration
form. In that form, the "Any other relevant information:" field
should indicate that it is the addition of an additional recommended languages in ISO 639. This agency is:

International Information Centre for Terminology (Infoterm)

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prefix.

Requests to add a recommended prefix to a subtag that imply a
different semantic meaning will probably be rejected. For example,

Aichholzgasse 6/12, AT-1120
Wien, Austria
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72

ISO 639-2 defines a
request to add the prefix "de" maintenance agency for additions to the subtag 'nedis' so that the tag
"de-nedis" represented some German dialect would be rejected. The
'nedis' subtag represents a particular Slovenian dialect and changes
in the
additional registration would change the semantic meaning assigned to
the subtag. A separate subtag should be proposed instead. list of languages in ISO 639-2. This agency is:

Library of Congress
Network Development and MARC Standards Office
Washington, D.C. 20540 USA
Phone: +1 202 707 6237 Fax: +1 202 707 0115
URL: http://www.loc.gov/standards/iso639

The Language Subtag Reviewer is responsible maintenance agency for responding to
requests ISO 3166 (country codes) is:

ISO 3166 Maintenance Agency
c/o International Organization for the Standardization
Case postale 56
CH-1211 Geneva 20 Switzerland
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49
URL: http://www.iso.org/iso/en/prods-services/iso3166ma/index.html

The registration authority for ISO 15924 (script codes) is:

Unicode Consortium Box 391476
Mountain View, CA 94039-1476, USA
URL: http://www.unicode.org/iso15924

The Statistics Division of subtags through the registration
process United Nations Secretariat maintains
the Standard Country or Area Codes for Statistical Use and is appointed can be
reached at:

Statistical Services Branch
Statistics Division
United Nations, Room DC2-1620
New York, NY 10017, USA

Fax: +1-212-963-0623
E-mail: statistics@un.org
URL: http://unstats.un.org/unsd/methods/m49/m49alpha.htm

3.6 Extensions and Extensions Namespace

Extension subtags are those introduced by single-letter subtags other
than 'x-'. They are reserved for the IESG.

When the two week period has passed the Language Subtag Reviewer
either forwards the request to iana@iana.org, or rejects it because generation of significant objections raised on the list or due to problems identifiers which
contain a language component, and are compatible with
constraints in applications
understand language tags. For example, they might be used to define
locale identifiers, which are generally based on language.

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The structure and form of extensions are defined by this document (which should so
that implementations can be explicitly cited). The
reviewer created that are forward compatible with
applications that may also extend the review period be created using single-letter subtags in two week increments the
future. In addition, defining a mechanism for maintaining single-
letter subtags will lend to
permit further discussion. The reviewer must indicate on the list
whether stability of this document by
reducing the registration has been accepted, rejected, likely need for future revisions or extended
following each two week period.

Note that updates.

Allocation of a single-letter subtag shall take the reviewer can raise objections on form of an RFC
defining the list if he or she
so desires. The important thing is that name, purpose, processes, and procedures for maintaining
the objection subtags. The maintaining or registering authority, including
name, contact email, discussion list email, and URL location of the
registry must be made
publicly. indicated clearly in the RFC. The applicant is free to modify a rejected application with
additional information RFC MUST specify
or include each of the following:

o The specification MUST reference the specific version or revision
of this document that governs its creation and submit it again; MUST reference this restarts the two
week comment period.

Decisions made
section of this document.

o The specification and all subtags defined by the reviewer may be appealed to the IESG [RFC 2028]
[10] under specification
MUST follow the same rules as ABNF and other IETF decisions [RFC 2026] [21].

All approved registration forms are available online in rules for the directory
http://www.iana.org/numbers.html under "languages".

Updates formation of registrations follow the same procedure tags and
subtags as registrations.
The subtag reviewer decides whether to allow a new registrant to
update a registration made by someone else; normally objections by
the original registrant would carry extra weight defined in such a decision.

Registrations are permanent this document. In particular it MUST
specify that case is not significant and stable. Once registered, that subtags
will not MUST NOT
exceed eight characters in length.

o The specification MUST specify a canonical representation.

o The specification of valid subtags MUST be removed from available over the registry
Internet and will remain at no cost.

o The specification MUST be in the canonical
method of referring to a specific language public domain or variant. This
provision does not apply to grandfathered tags, which may become
deprecated due available via a
royalty-free license acceptable to registration of subtags. For example, the tag
"i-navajo" is deprecated IETF and specified in favor the
RFC.

o The specification MUST be versioned and each version of the ISO 639-1 based subtag 'nv'.
specification MUST be numbered, dated, and stable.

o The specification MUST be stable. That is, extension subtags,
once defined by a specification, MUST NOT be retracted or change
in meaning in any substantial way.

o The specification MUST include in a separate section the
registration form reproduced in this section (below) to be used in
registering the extension upon publication as an RFC.

o IANA MUST be informed of changes to the contact information and
URL for the specification.

IANA will maintain a registry of allocated single-letter (singleton)

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Note: The purpose

subtags. This registry will use the record-jar format described by
the ABNF in Section 3.1. Upon publication of an extension as an RFC,
the "published description" maintaining authority defined in the RFC must forward this
registration form is intended as an aid to people trying to verify whether a
language is registered or what language or language variation a
particular subtag refers to. In most cases, reference iesg@ietf.org, who will forward the request to
iana@iana.org. The maintaining authority of the extension MUST
maintain the accuracy of the record by sending an
authoritative grammar or dictionary updated full copy
of that language will the record to iana@iana.org with the subject line "LANGUAGE TAG
EXTENSION UPDATE" whenever content changes. Only the 'Comments',
'Contact_Email', 'Mailing_List', and 'URL' fields may be useful; modified in cases where no such work exists, other well known works describing
that language
these updates.

Failure to maintain this record, the corresponding registry, or in that language meet
other conditions imposed by this section of this document may be appropriate. The subtag
reviewer decides what constitutes "good enough" reference material.
This requirement is not intended to exclude particular languages or
dialects due
appealed to the size of IESG [RFC 2028] [9] under the speaker population or lack of a
standardized orthography. Minority languages will be considered
equally on their own merits.

3.4 Extensions and Extensions Namespace

Extension subtags are those introduced by single-letter subtags same rules as other
than 'x-'. They are reserved for the generation of identifiers which
contain a language component, and are compatible with applications
that process language tags according to this specification. For
example, they might be used to define locale identifiers, which are
generally based on language.

The structure
IETF decisions (see [8]) and form of extensions are defined by this document so
that implementations can be created that are forward compatible with
applications that may be created using single-letter subtags result in the
future. In addition, defining a mechanism for maintaining
single-letter subtags will lend authority to maintain
the stability of this document extension being withdrawn or reassigned by
reducing the likely need for future revisions or updates.

IANA will maintain a registry IESG.
%%
Identifier:
Description:
Comments:
Added:
RFC:
Authority:
Contact_Email:
Mailing_List:
URL:
%%

Figure 6: Format of allocated single-letter subtags.
This registry Records in the Language Tag Extensions Registry

'Identifier' contains the following information: single letter identifier;
name; purpose; RFC defining the subtag namespace and its use; and (singleton) assigned
to the
name, URL, extension. The Internet-Draft submitted to define the
extension should specific which letter to use, although the IESG may
change the assignment when approving the RFC.

'Description' contains the name and email address description of the maintaining authority.

Allocation of extension.

'Comments' is an optional field and may contain a single-letter subtag shall take the form broader description
of an RFC
defining the name, purpose, processes, and procedures for maintaining extension.

'Added' contains the subtags. The maintaining or registering authority, including
name, contact email, discussion list email, and URL location of date the
registry must be indicated clearly RFC was published in the RFC. The "full-date"
format specified in RFC MUST specify
each of 3339 [14]. For example: 2004-06-28
represents June 28, 2004, in the following:
o The specification MUST reference Gregorian calendar.

'RFC' contains the specific version or revision
of this document that govern its creation and MUST reference this
section of this document.
o The specification and all subtags defined by RFC number assigned to the specification
MUST follow extension.

'Authority' contains the ABNF and other rules name of the maintaining authority for the formation of tags and
subtags as defined in this document. In particular it MUST
specify that case is not significant.
extension.

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o The specification MUST specify a canonical representation.
o The specification of valid subtags MUST be available over the
Internet and at no cost.
o The specification MUST be in

'Contact_Email' contains the public domain or available via a
royalty-free license acceptable email address used to contact the IETF and specified in
maintaining authority.

'Mailing_List' contains the
RFC.
o The specification MUST be versioned and each version URL or subscription email address of the
specification MUST be numbered, dated, and stable.
o The specification MUST be stable. That is, extension subtags,
once defined
mailing list used by a specification, MUST NOT be retracted or change
in meaning in any substantial way.
o IANA MUST be informed of changes to the contact information and maintaining authority.

'URL' contains the URL for of the specification. registry for this extension.

The determination of whether an Internet-Draft meets the above
conditions and the decision to grant or withhold such authority rests
solely with the IESG, and is subject to the normal review and appeals
process associated with the RFC process.

Extension authors are strongly cautioned that many (including most
well-formed) processors will be unaware of any special relationships
or meaning inherent in the order of extension subtags. Extension
authors SHOULD avoid subtag relationships or canonicalization
mechanisms that interfere with matching or with length restrictions
that may exist in common protocols where the extension is used. In
particular, applications may truncate the subtags in doing matching
or in fitting into limited lengths, so it is RECOMMENDED that the
most significant information be in the most significant (left-most)
subtags, and that the specification gracefully handle truncated
subtags.

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
supported by that protocol. In addition, it should be noted that
some protocols may impose upper limits on the length of the strings
used to store or transport the language tag.

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4. Security Considerations

The only security issue that has been raised with language tags since

3.7 Conversion of the RFC 3066 Language Tag Registry

Upon publication of RFC 1766, which stated that "Security issues are
believed to be irrelevant to this memo", is document as a concern with BCP, the existing IANA
language
identifiers used in content negotiation - that they may tag registry must be used to
infer converted into the nationality of new subtag registry.
This section defines the sender, and thus identify potential
targets process for surveillance.

This is performing this conversion.

The impact on the IANA maintainers of the registry of this conversion
will be a special case small increase in the frequency of new entries. The
initial set of records represents no impact on IANA, since the general problem that anything you send
is visible work
to create it will be performed externally (as defined in this
section). Future work will be limited to inserting or replacing
whole records preformatted for IANA by the receiving party. It Language Subtag Reviewer.

When this document is useful to published, an email will be aware that
such concerns can exist in some cases.

The evaluation of sent by the exact magnitude
chair(s) of the threat, and any possible
countermeasures, is left LTRU working group to each application protocol.

Although the specification LTRU and ietf-languages
mail lists advising of valid subtags for an extension MUST be
available over the Internet, implementations SHOULD NOT mechanically
depend on it being always accessible, to prevent denial-of-service
attacks. impending conversion of the registry. In
that notice, the chair(s) will provide a URL whose referred content

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5. Character Set Considerations

The syntax in this document requires that language tags use only

is the
characters A-Z, a-z, 0-9, and HYPHEN-MINUS, which are present in most
character sets, so presentation proposed IANA Language Subtag Registry following conversion.
There will be a Last Call period of language tags should not have any
character set issues.

Rendering of characters based less than four weeks for
comments and corrections to be discussed on the content of
ietf-languages@iana.org mail list. Changes as a language tag is result of comments
will not
addressed in this memo. Historically, some languages have relied on restart the use Last Call period. At the end of specific character sets or other information in order the period, the
chair(s) will forward the URL to
infer how IANA, which will post the new
registry on-line.

Tags that are currently deprecated will be maintained as
grandfathered entries. The record for the grandfathered entry will
contain a specific character should 'Deprecated' field with the most appropriate date that can
be rendered (notably this
applies to language determined for when the record was deprecated. The 'Comments'
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 culture specific variations of Han ideographs
as used will be placed in Japanese, Chinese, the
grandfathered section. It's 'Deprecated' field will contain the
deprecation date and Korean). When language tags 'Canonical' field the value "jbo".

Tags that are
applied to spans not deprecated that consist entirely of text, rendering engines may use subtags that information
in deciding
are valid under this document and which font to use in have the absence of other information,
particularly where languages with distinct writing traditions use the
same characters.

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6. Changes from RFC 3066

The main goals correct form and
format for this revision of language tags were the following:

*Compatibility.* All valid RFC 3066 language defined by this document are superseded by this
document. Such tags (including those are placed in the IANA registry) remain valid records of type 'redundant' in this specification. Thus
there the
registry. For example, "zh-Hant" is complete backward compatibility of now defined by this specification document.

Tags that are not deprecated and which contain subtags which are
consistent with
existing content. In addition, registration under the guidelines in this document defines language tags
in such as way as to ensure future compatibility, and processors
based solely on
will have a new subtag registration created for each eligible subtag.
If all of the RFC 3066 ABNF (such as those described subtags in XML
Schema version 1.0) will be able to process tags described the original tag are fully defined by the
resulting registrations or by this document, then the original tag is
superseded by this document.

*Stability.* Because Such tags are placed in the 'redundant'
section of the changes registry. For example, "en-boont" will result in underlying ISO standards, a
valid
new subtag 'boont' and the RFC 3066 language registered tag may become invalid (or have its meaning
change) at a later date. With so much "en-boont" placed
in the redundant section of the world's computing
infrastructure dependent on language tags, this is simply
unacceptable: it invalidates content registry.

Tags that may have an extensive
shelf-life. In this specification, once a language tag is valid, it
remains valid forever. Previously, there was no way to determine
when two tags were equivalent. This specification provides a stable
mechanism for doing so, through the use of canonical forms. These
are also stable, so contain one or more subtags that implementations can depend on do not match the use of
canonical forms to assess equivalency.

*Validity.* The structure of language tags valid
registration pattern and which are not otherwise defined by this
document
makes it possible to determine if a particular tag is well-formed
without regard for the actual content or "meaning" will have records of type 'grandfathered' created in the tag as a
whole. This is important because the registry and underlying
standards change over time. In addition, it must
registry.

There will be possible to
determine if a tag is valid (or not) for a given point in time reasonable period in
order to provide reproducible, testable results. This process must
not which the community may comment
on the proposed list entries, which SHALL be error-prone; otherwise even intelligent people no less than four weeks
in length. At the completion of this period, the chair(s) will generate
implementations
notify iana@iana.org and the ltru and ietf-languages mail lists that give different results. This specification
provides
the task is complete and forward the necessary materials to IANA for
publication.

Registrations that by having a single data file, with specific
versioning information, so that are in process under the validity of language tags at any
point rules defined in time can RFC 3066
MAY be precisely determined (instead completed under the former rules, at the discretion of interpolating
values from many separate sources).

*Extensibility.* It is important to be able to differentiate between
written forms of language -- for many implementations this is more
important than distinguishing between spoken variants of a language.
Languages are written in a wide variety of different scripts, so this
document provides for the generative use of ISO 15924 script codes.
Like the generative use of ISO language and country codes in RFC
3066, this allows combinations to be produced without resorting to
the registration process. The addition of UN codes provides for the
generation of language tags with regional scope, which is also

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required

language tag reviewer. Any new registrations submitted after the
request for information technology.

The recast conversion of the registry from containing whole language tags to
subtags is a key part of this. An important feature of MUST be rejected.

All existing RFC 3066 was
that it allowed generative use of subtags. This allows people to
meaningfully use generated tags, without the delays language tag registrations will be maintained
in perpetuity.

Users of tags that are grandfathered should consider registering
whole tags, and the burden on
appropriate subtags in the IANA subtag registry (but are not required
to).

Where two subtags have the same meaning, the priority of having which to supply all of
make canonical SHALL be the combinations that people may find useful.

Because following:

o As of the widespread use date of language tags, acceptance of this document as a BCP, if a code
exists in the associated ISO standard and it is potentially
disruptive to have periodic revisions not deprecated or
withdrawn as of that date, then it has priority.

o Otherwise, the core specification,
despite demonstrated need. The extension mechanism provides for a
way for independent RFCs to define extensions to language tags.
These extensions have a very constrained, well-defined structure earlier-registered tag in the associated ISO
standard has priority.

UN numeric codes assigned to
prevent extensions from interfering 'macro-geographical (continental)' or
sub-regions not associated with implementations of language
tags an assigned ISO 3166 alpha-2 code are
defined in this document. The document also anticipates
features of ISO 639-3 with the addition of the extlang subtags. The
use IANA registry and definition of private are valid for use tags has also been modified, to
allow people in language tags.
These codes MUST be added to move as much information as possible out the initial version of private
use tags, and into the regular structure. registry.
The goal is to
dramatically reduce UN numeric codes for 'economic groupings' or 'other groupings',
and the need to produce a revision of this document alphanumeric codes in Appendix X of the future.

The specific changes in this UN document MUST NOT
be added to meet these goals are:
o Defines the ABNF and rules registry.

When creating records for subtags so that ISO 639, ISO 15924, ISO3166, and UN M.49
codes, the category of all
subtags can following criteria SHALL be determined without reference applied to the registry.
o Adds the concept inclusion,
canonical mapping, and deprecation of well-formed vs. validating processors,
defining codes:

For each standard, the rules by which an implementation can claim to be one
or date of the other.
o Changes standard referenced in RFC 1766 is
selected as the IANA language tag registry to a language subtag
registry starting date. Codes that provides a complete list of were valid subtags on that date in
the
IANA selected standard are added to the registry. This allows for robust implementation and ease of
maintenance. The language subtag registry becomes the canonical
source for forming language tags.
o Provides a process Codes that guarantees stability of language tags, by
handling reuse of values were
previously assigned by ISO 639, ISO 15924, and ISO 3166 in
the event were vacated or withdrawn before that they register a previously used value for a new
purpose.
o Allows ISO 15924 script code subtags and allows them date are
not added to be used
generatively. Adds the concept registry. For each successive change to the
standard, any additional assignments are added to the registry.
Values that are withdrawn are marked as deprecated, but not removed.
Changes in meaning or assignment of a variant subtag and allows
variants are permitted during
this process (cf. 'CS'). This continues up to be used generatively. Adds the ability date that this
document was adopted. The resulting set of records is added to use a class the
registry. Future changes or additions to this portion of UN tags as regions.
o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166
as
registry are governed by the mechanism for creating private-use language, script, and
region subtags respectively.
o Adds a well-defined extension mechanism.
o Defines an extended language subtag, possibly for use with certain
anticipated features provisions of ISO 639-3. this document.

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Ed Note: The following items are provided for the convenience of
reviewers and will be removed from the final document.

Changes between draft-phillips-langtags-10

4. Formation and this version are:
o Expunged the terminology "language range", since that Processing of Language Tags

This section goes
with matching (A.Phillips, M.Davis)
o Added text describing addresses how to use the handling of existing RFC 3066 registry
entries that were deprecated prior to with the adoption language tag
format to choose, form and process language tags.

4.1 Choice of this
document. These Language Tag

One may occasionally be faced with several possible tags are now grandfathered. (A.Phillips,
D.Ewell)
o Modified the conversion rules for the registry (Appendix C) to
refer same
body of text.

Interoperability is best served when all users use the same language
tag in order to represent the same language. If an application has
requirements that make the rules here inapplicable, then that
application risks damaging interoperability. It is strongly
RECOMMENDED that users not define their own rules for language tag
choice.

Of particular note, many applications can benefit from the chairs, use of
script subtags in language tags, as long as the LTRU mail list use is consistent for
a given context. Script subtags were not formally defined in RFC
3066 and so forth (A.Phillips)
o Added text to allow tags their use may affect matching and subtag identification by
implementations of RFC 3066, as these subtags to be deprecated appear between the
primary language and region subtags. For example, if a user requests
content in an implementation of Section 2.5 of RFC 3066 [23] using
the
canonical value "--". This language range "en-US", content labeled "en-Latn-US" will not
match the request. Therefore it is applied important to codes withdrawn by ISO
639 MA know when script
subtags will customarily be used and ISO 3166 MA, for example. (F.Ellerman, D.Ewell)

7. References

[1] International Organization for Standardization, "ISO
639-1:2002, Codes when they should not be used.

Extended language subtags (type 'extlang' in the registry, see
Section 3.1) also appear between the primary language and region
subtags and are reserved for future standardization. Applications
may benefit from their judicious use in forming language tags in the representation of names of languages
-- Part 1: Alpha-2 code", ISO Standard 639, 2002.

[2] International Organization for Standardization, "ISO 639-2:1998
- Codes for
future and similar recommendations are expected to apply to their use
as apply to script subtags.

Standards, protocols and applications that reference this document
normatively but apply different rules to the representation of names of languages -- Part 2:
Alpha-3 code - edition 1", August 1988.

[3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for ones given in this
section MUST specify how the
representation of names of scripts", January 2004.

[4] International Organization for Standardization, "Codes for procedure varies from the
representation of names one given
here.

The choice of countries, 3rd edition",
ISO Standard 3166, August 1988.

[5] Statistical Division, United Nations, "Standard Country or Area
Codes for Statistical Use", UN Standard Country or Area Codes
for Statistical Use, Revision 4 (United Nations publication,
Sales No. 98.XVII.9, June 1999.

[6] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory
Committee: Working principles for ISO 639 maintenance", March
2000,
<http://www.loc.gov/standards/iso639-2/iso639jac_n3r.html>.

[7] Hardcastle-Kille, S., "Mapping between X.400(1988) / ISO 10021
and RFC 822", RFC 1327, May 1992.

[8] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail
Extensions) Part One: Mechanisms subtags used to form a language tag should be guided by
the following rules:

1. Use as precise a tag as possible, but no more specific than is
justified. Avoid using subtags that are not important for Specifying and Describing
distinguishing content in an application.

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the Format of Internet Message Bodies", RFC 1521, September
1993.

[9] Alvestrand, H., "Tags

* For example, 'de' might suffice for the Identification of Languages",
RFC 1766, March 1995.

[10] Hovey, R. and S. Bradner, "The Organizations Involved tagging an email written
in German, while "de-CH-1996" is probably unnecessarily
precise for such a task.

2. The script subtag SHOULD NOT be used to form language tags unless
the script adds some distinguishing information to the tag. The
field 'Suppress-Script' in the primary language record in the
registry indicates which script subtags do not add distinguishing
information for most applications.

* For example, the subtag 'Latn' should not be used with the
primary language 'en' because nearly all English documents are
written in the Latin script and it adds no distinguishing
information. However, if a document were written in English
mixing Latin script with another script such as Braille
('Brai'), then it may be appropriate to choose to indicate
both scripts to aid in content selection, such as the
application of a stylesheet.

3. If a subtag has a 'Canonical' field in its registry entry, the
canonical subtag SHOULD be used to form the language tag in
preference to any of its aliases.

* For example, use 'he' for Hebrew in preference to 'iw'.

4. The 'und' (Undetermined) primary language subtag SHOULD NOT be
used to label content, even if the language is unknown. Omitting
the language tag altogether is preferred to using a tag with a
primary language subtag of 'und'. The 'und' subtag may be useful
for protocols that require a language tag to be provided. The
'und' subtag may also be useful when matching language tags in
certain situations.

5. The 'mul' (Multiple) primary language subtag SHOULD NOT be used
whenever the protocol allows the separate tags for multiple
languages, as is the case for the Content-Language header in
HTTP. The 'mul' subtag conveys little useful information:
content in multiple languages should individually tag the
languages where they appear or otherwise indicate the actual
language in preference to the 'mul' subtag.

6. The same variant subtag SHOULD NOT be used more than once within
a language tag.

* For example, do not use "en-GB-scouse-scouse".

To ensure consistent backward compatibility, this document contains
several provisions to account for potential instability in the

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standards used to define the subtags that make up language tags.
These provisions mean that no language tag created under the rules in
this document will become obsolete. In addition, tags that are in
canonical form will always be in canonical form.

4.2 Meaning of the Language Tag

The language tag always defines a language as spoken (or written,
signed or otherwise signaled) by human beings for communication of
information to other human beings. Computer languages such as
programming languages are explicitly excluded.

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-
Hant-TW" is more specific than "zh-Hant".

This relationship is not guaranteed in all cases: specifically,
languages that begin with the same sequence of subtags are NOT
guaranteed to be mutually intelligible, although they may be. For
example, the tag "az" shares a prefix with both "az-Latn"
(Azerbaijani written using the Latin script) and "az-Cyrl"
(Azerbaijani written using the Cyrillic script). A person fluent in
one script may not be able to read the other, even though the text
might be identical. Content tagged as "az" most probably is written
in just one script and thus might not be intelligible to a reader
familiar with the other script.

The relationship between the tag and the information it relates to is
defined by the standard describing the context in which it appears.
Accordingly, this section can only give possible examples of its
usage.

o For a single information object, the associated language tags
might be interpreted as the set of languages that is required for
a complete comprehension of the complete object. Example: Plain
text documents.

o For an aggregation of information objects, the associated language
tags could be taken as the set of languages used inside components
of that aggregation. Examples: Document stores and libraries.

o For information objects whose purpose is to provide alternatives,
the associated language tags could be regarded as a hint that the
content is provided in several languages, and that one has to
inspect each of the alternatives in order to find its language or
languages. In this case, the presence of multiple tags might not
mean that one needs to be multi-lingual to get complete
understanding of the document. Example: MIME multipart/

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alternative.

o In markup languages, such as HTML and XML, language information
can be added to each part of the document identified by the markup
structure (including the whole document itself). For example, one
could write <span lang="fr">C'est la vie.</span> inside a
Norwegian document; the Norwegian-speaking user could then access
a French-Norwegian dictionary to find out what the marked section
meant. If the user were listening to that document through a
speech synthesis interface, this formation could be used to signal
the synthesizer to appropriately apply French text-to-speech
pronunciation rules to that span of text, instead of applying the
inappropriate Norwegian rules.

4.3 Canonicalization of Language Tags

Since a particular language tag may be used in many processes,
language tags SHOULD always be created or generated in a canonical
form.

A language tag is in canonical form when:

1. The tag is well-formed according the rules in Section 2.1 and
Section 2.2.

2. None of the subtags in the language tag has a canonical_value
mapping in the IANA registry (see Section 3.1). Subtags with a
canonical_value mapping MUST be replaced with their mapping in
order to canonicalize the tag.

3. If more than one extension subtag sequence exists, the extension
sequences are ordered into case-insensitive ASCII order by
singleton subtag.

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
canonical form.

Example: The language tag "en-NH" (English as used in the New
Hebrides) is not canonical because the 'NH' subtag has a canonical
mapping to 'VU' (Vanuatu).

Note: Canonicalization of language tags does not imply anything about
the use of upper or lowercase letter in subtags as described in
Section 2.1. All comparisons MUST be performed in a case-insensitive
manner.

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Note: if the field 'Deprecated' appears in a registry record without
an accompanying 'Canonical' field, then that tag or subtag is
deprecated without a replacement. Validating processors SHOULD NOT
generate tags that include these values, although the values are
canonical when they appear in a language tag.

An extension MUST define any relationships that may exist between the
various subtags in the extension and thus MAY define an alternate
canonicalization scheme for the extension's subtags. Extensions MAY
define how the order of the extension's subtags are interpreted. For
example, an extension could define that its subtags are in canonical
order when the subtags are placed into ASCII order: that is, "en-a-
aaa-bbb-ccc" instead of "en-a-ccc-bbb-aaa". Another extension might
define that the order of the subtags influences their semantic
meaning (so that "en-b-ccc-bbb-aaa" has a different value from "en-b-
aaa-bbb-ccc"). However, extension specifications SHOULD be designed
so that they are tolerant of the typical processes described in
Section 3.6.

4.4 Considerations for Private Use Subtags

Private-use subtags require private agreement between the parties
that intend to use or exchange language tags that use them and great
caution should be used in employing them in content or protocols
intended for general use. Private-use subtags are simply useless for
information exchange without prior arrangement.

The value and semantic meaning of private-use tags and of the subtags
used within such a language tag are not defined by this document.

The use of subtags defined in the IANA registry as having a specific
private use meaning convey more information that a purely private use
tag prefixed by the singleton subtag 'x'. For applications this
additional information may be useful.

For example, the region subtags 'AA', 'ZZ' and in the ranges
'QM'-'QZ' and 'XA'-'XZ' (derived from ISO 3166 private use codes) may
be used to form a language tag. A tag such as "zh-Hans-XQ" conveys a
great deal of public, interchangeable information about the language
material (that it is Chinese in the simplified Chinese script and is
suitable for some geographic region 'XQ'). While the precise
geographic region is not known outside of private agreement, the tag
conveys far more information than an opaque tag such as "x-someLang",
which contains no information about the language subtag or script
subtag outside of the private agreement.

However, in some cases content tagged with private use subtags may
interact with other systems in a different and possibly unsuitable

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manner compared to tags that use opaque, privately defined subtags,
so the choice of the best approach may depend on the particular
domain in question.

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5. IANA Considerations

This section deals with the processes and requirements necessary for
IANA to undertake to maintain the rsubtag and extension registries as
defined by this document and in accordance with the requirements of
RFC 2434 [11].

The impact on the IANA maintainers of the two registries defined by
this document will be a small increase in the frequency of new
entries or updates.

Upon adoption of this document, the process described in Section 3.7
will be used to generate the initial Language Subtag Registry. The
initial set of records represents no impact on IANA, since the work
to create it will be performed externally (as defined in that
section). The new registry will be listed under "Language Tags" at
<http://www.iana.org/numbers.html>. The existing directory of
registration forms and RFC 3066 registrations will be relabeled as
"Language Tags (Obsolete)" and maintained (but not added to or
modified).

Future work on the Language Subtag Registry will be limited to
inserting or replacing whole records preformatted for IANA by the
Language Subtag Reviewer as described in Section 3.2 of this
document. Each record will be sent to iana@iana.org with a subject
line indicating whether the enclosed record is an insertion (of a new
record) or a replacment of an existing record which has a Type and
Subtag (or Tag) field that exactly matches the record sent. Records
cannot be deleted from the registry.

The Language Tag Extensions registry will also be generated and sent
to IANA as described in Section 3.6. This registry may contain at
most 25 records and thus changes to this registry are expected to be
very infrequent.

Future work by IANA on the Language Tag Extensions Registry is
limited to two cases. First, the IESG may request that new records
be inserted into this registry from time to time. These requests
will include the record to insert in the exact format described in
Section 3.6. In addition, there may be occasional requests from the
maintaining authority for a specific extension to update the contact
information or URLs in the record. These requests MUST include the
complete, updated record. IANA is not responsible for validating the
information provided, only that it is properly formatted. It should
reasonably be seen to come from the maintaining authority named in
the record present in the registry.

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6. Security Considerations

The only security issue that has been raised with language tags since
the publication of RFC 1766 [21], which stated that "Security issues
are believed to be irrelevant to this memo", is a concern with
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.

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.
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
countermeasures, is left to each application protocol (see BCP 72,
RFC 3552 [15] for best current practice guidance on security threats
and defenses).

Although the specification of valid subtags for an extension MUST be
available over the Internet, implementations SHOULD NOT mechanically
depend on it being always accessible, to prevent denial-of-service
attacks.

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7. Character Set Considerations

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
character sets, so the composition of language tags should not have
any character set issues.

Rendering of characters based on the content of a language tag is not
addressed in this memo. Historically, some languages have relied on
the use of specific character sets or other information in order to
infer how a specific character should be rendered (notably this
applies to language and culture specific variations of Han ideographs
as used in Japanese, Chinese, and Korean). When language tags are
applied to spans of text, rendering engines may use that information
in deciding which font to use in the absence of other information,
particularly where languages with distinct writing traditions use the
same characters.

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8. Changes from RFC 3066

The main goals for this revision of language tags were the following:

*Compatibility.* All valid RFC 3066 language tags (including those
in the IANA registry) remain valid in this specification. Thus
there is complete backward compatibility of this specification with
existing content. In addition, this document defines language tags
in such as way as to ensure future compatibility, and processors
based solely on the RFC 3066 ABNF (such as those described in XML
Schema version 1.0 [19]) will be able to process tags described by
this document.

*Stability.* Because of the changes in underlying ISO standards, a
valid RFC 3066 language tag may become invalid (or have its meaning
change) at a later date. With so much of the world's computing
infrastructure dependent on language tags, this is simply
unacceptable: it invalidates content that may have an extensive
shelf-life. In this specification, once a language tag is valid, it
remains valid forever. Previously, there was no way to determine
when two tags were equivalent. This specification provides a stable
mechanism for doing so, through the use of canonical forms. These
are also stable, so that implementations can depend on the use of
canonical forms to assess equivalency.

*Validity.* The structure of language tags defined by this document
makes it possible to determine if a particular tag is well-formed
without regard for the actual content or "meaning" of the tag as a
whole. This is important because the registry and underlying
standards change over time. In addition, it must be possible to
determine if a tag is valid (or not) for a given point in time in
order to provide reproducible, testable results. This process must
not be error-prone; otherwise even intelligent people will generate
implementations that give different results. This specification
provides for that by having a single data file, with specific
versioning information, so that the validity of language tags at any
point in time can be precisely determined (instead of interpolating
values from many separate sources).

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required for information technology.

The recast of the registry from containing whole language tags to
subtags is a key part of this. An important feature of RFC 3066 was
that it allowed generative use of subtags. This allows people to
meaningfully use generated tags, without the delays in registering
whole tags, and the burden on the registry of having to supply all of
the combinations that people may find useful.

Because of the widespread use of language tags, it is potentially
disruptive to have periodic revisions of the core specification,
despite demonstrated need. The extension mechanism provides for a
way for independent RFCs to define extensions to language tags.
These extensions have a very constrained, well-defined structure to
prevent extensions from interfering with implementations of language
tags defined in this document. The document also anticipates
features of ISO 639-3 with the addition of the extended language
subtags, as well as the possibility of other ISO 639 parts becoming
useful for the formation of language tags in the future. The use and
definition of private use tags has also been modified, to allow
people to move as much information as possible out of private use
tags, and into the regular structure. The goal is to dramatically
reduce the need to produce a revision of this document in the future.

The specific changes in this document to meet these goals are:

o Defines the ABNF and rules for subtags so that the category of all
subtags can be determined without reference to the registry.

o Adds the concept of well-formed vs. validating processors,
defining the rules by which an implementation can claim to be one
or the other.

o Replaces the IANA language tag registry with a language subtag
registry that provides a complete list of valid subtags in the
IANA registry. This allows for robust implementation and ease of
maintenance. The language subtag registry becomes the canonical
source for forming language tags.

o Provides a process that guarantees stability of language tags, by
handling reuse of values by ISO 639, ISO 15924, and ISO 3166 in
the event that they register a previously used value for a new
purpose.

o Allows ISO 15924 script code subtags and allows them to be used
generatively. Adds the concept of a variant subtag and allows
variants to be used generatively. Adds the ability to use a class
of UN tags as regions.

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o Defines the private-use tags in ISO 639, ISO 15924, and ISO 3166
as the mechanism for creating private-use language, script, and
region subtags respectively.

o Adds a well-defined extension mechanism.

o Defines an extended language subtag, possibly for use with certain
anticipated features of ISO 639-3.

Ed Note: The following items are provided for the convenience of
reviewers and will be removed from the final document.

Changes between draft-ietf-ltru-registry-00 and this version are:

o Updated the ABNF for singleton to make it conform to RFC 2234 and
pass the Fenner parser (F.Ellermann)

o Split the references into informative and normative lists.
Eliminated dead references carried forward from previous versions
of this document. (A.Phillips)

o Added a reference to RFC 3552 (BCP 72) to the Security
Considerations section (I.McDonald)

o Modified the first sentence in Section 2.1.1 from "on the
IETF Standards Process", BCP 11, RFC 2028, October 1996.

[11] Bradner, S., "Key words for number
of size of subtags in a Language Tag" to be proper English and
convey more meaning. (A.Phillips)

o Various examples that used the variant 'boont' were changes to use
the variant 'scouse' instead. (J.Cowan)

o Added an additional example ("en-a-bbb-x-a-ccc") to the extension/
singleton rules in RFCs Section 2.2.6 to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.

[12] Freed, N. illustrate that singletons can
recur in private use sequences (A.Phillips)

o Modified the sentence describing the possibilities for variant
registration (see Section 3.5) to include transliterations and K. Moore, "MIME Parameter Value
other transformations per discussion on the list. (M.T. Carrasco
Benitez)

o Converted the format of the registry to record-jar format. This
subtantially replaces section 3.1 (R.Presuhn)

o Subtantially revised the rules for registry creation to reflect
the Date A/B boundaries on adopting ISO 3166 codes (J.Cowan)

o Modified the registration process section and Encoded Word
Extensions: Character Sets, Languages, form to deal with
both new additions and Continuations", revisions of records, as well as making

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life easier on the Subtag Reviewer by matching the fields to the
registry format. (A.Phillips)

o Changed the reference to RFC 2231, November 1997.

[13] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", 2234 to RFC 2234, November 1997.

[14] Berners-Lee, T., Fielding, R. 2234bis (recently
adopted). (S.Hollenbeck)

o Modifications to make this document conformant with RFC 3978
(recently adopted). (R.Presuhn)

o Added an informative reference to XML Schema 1.0 Part 2: Second
Edition in this section. (J.Morfin)

o Expanded the jargon-ish 'extlang' to "extended language" in this
section. (J.Morfin)

o Corrected an egregious error in the ABNF (%x6A -> %x5A in one of
the ranges) (A.Phillips)

o Split Maintenance of the Registry from Format of the Registry
(A.Phillips)

o Revision of section Section 3.4 to make it consistent with the new
section Section 3.2. (A.Phillips)

o Separated IANA Considerations section from the registry definition
and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August
1998.

[15] Narten, T. registration procedures. ()

o Added additional choice information dealing with scripts and H. Alvestrand, "Guidelines for Writing an
extlangs. These items were also moved to a new section following
the registry format because of interdependence.

o Updated the IANA Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.

[16] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.

[17] Carpenter, B., Baker, F. section.

o Added appeal and M. Roberts, "Memorandum maintenance requirements to the extensions
Section 3.6 section. (A.Phillips)

o Added an additional bullet point to Section 3.5 enumerating the
changes that can be registered to a record (previously we only
listed the options for new subtags). (A.Phillips)

o Added the phrase ", as well as the possibility of
Understanding Concerning other ISO 639
parts becoming useful for the Technical Work formation of language tags in the Internet
Assigned Numbers Authority", RFC 2860, June 2000.

[18] Alvestrand, H., "Tags
future" to this section in anticipation of revising the ABNF to
allow for the Identification possibility of Languages",
BCP 47, RFC 3066, January 2001.

[19] Yergeau, F., "UTF-8, ISO 639-6 being used in language tags
in a transformation format future revision of ISO 10646",
STD 63, RFC 3629, November 2003.

[20] Klyne, G. and C. Newman, "Date and Time on this document. (D.Garside)

o Added the Internet:
Timestamps", RFC 3339, July 2002.

[21] <http://www.ietf.org/rfc/rfc2026.txt>

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Authors' Addresses

Addison Phillips (editor)
Quest Software

Email: addison.phillips@quest.com

Mark Davis (editor)
IBM

Email: mark.davis@us.ibm.com concept of 'Suppress-Script' to Section 4.1, as well as
to the registry format in Section 3.1, Section 3.3 and

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Appendix A. Acknowledgements

Any list of contributors is bound to be incomplete; please regard

Section 3.2. (many)

o Added text requiring the
following as only I-D that defines an extension to choose a selection from
letter (and allowing the group of people who have
contributed IESG to make this document what change it is today.

The contributors to RFC 3066 and RFC 1766, if necessary).
(D.Ewell?)

o Removed the precursors of this
document, made enormous contributions directly or indirectly to this
document and are generally responsible for ABNF notes from the success of language
tags.

The following people (in alphabetical order) contributed text about case insensitivity
(F.Ellermann)

o Removed the second, rather repetitive reference to this
document or Appendix B in
Section 2.1 (A.Phillips)

o Fixed missing whitesapce in Section 2.1 (F.Ellermann)

o Changed "empty" to RFCs 1766 and 3066:

Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet,
Nathaniel Borenstein, Eric Brunner, Sean M. Burke, Jeremy Carroll,
John Clews, Jim Conklin, Peter Constable, John Cowan, Mark Crispin,
Dave Crocker, Martin Duerst, Frank Ellerman, Michael Everson, Doug
Ewell, Ned Freed, Tim Goodwin, Dirk-Willem van Gulik, Marion Gunn,
Joel Halpren, Elliotte Rusty Harold, Paul Hoffman, Richard Ishida,
Olle Jarnefors, Kent Karlsson, John Klensin, Alain LaBonte, Eric
Mader, Keith Moore, Chris Newman, Masataka Ohta, George Rhoten,
Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto Stolz, Tex
Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois Yergeau and
many, many others.

Very special thanks must go "omitted" in Section 2.2.1 (F.Ellermann)

o Changed the intro to Harald Tveit Alvestrand, who
originated RFCs 1766 and 3066, Section 2.2.1 and without whom this document would
not have been possible. Special thanks must go to Michael Everson,
who has served as otherwise tugged at that
section to deal with i-* grandfathered items. (F.Ellermann)

o Reserved alpha4 language tag reviewer subtags for almost future standardization.
(D.Garside)

o Incorporate changes to be consistent with RFC 3978, including the complete
period since
new xml2rfc processor. Note that this has an effect on the publication ABNF,
since some of RFC 1766. Special thanks the comments were too wide previously (comments were
revised to Doug
Ewell, fit the 72 character maximum). (S.Hollenbeck)

o Remove the Latin-1 restriction on the 'Description' field.
Provide guidance for his production registration of the first complete subtag registry, and
his work in producing content, including a test parser
requirement for verifying at least one representation in the Latin script.
(F.Ellermann, A.Phillips)

o Make the variant subtlety less so. (F.Ellermann)

o Various 'you' removals and cleanup (M.Davis)

o Inserted additional non-normative caveat about the 'MUL' subtag
(A.Phillips)

o Various editorial edits (J.Cowan)

o Use normative language tags. when giving permission to not store long
language tags in Section 2.1.1. (J.Cowan)

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Appendix B. Examples

9. References

9.1 Normative References

[1] International Organization for Standardization, "ISO 639-
1:2002, Codes for the representation of Language Tags (Informative)

Simple language subtag:
de (German)
fr (French)
ja (Japanese)
i-enochian (example names of a grandfathered tag)

Language subtag plus Script subtag:
zh-Hant (Traditional Chinese)
en-Latn (English written in Latin script)
sr-Cyrl (Serbian written with Cyrillic script)

Language-Script-Region:
zh-Hans-CN (Simplified Chinese languages --
Part 1: Alpha-2 code", ISO Standard 639, 2002.

[2] International Organization for Standardization, "ISO 639-2:1998
- Codes for the PRC)
sr-Latn-CS (Serbian, Latin script, Serbia and Montenegro)

Language-Script-Region-Variant:
en-Latn-US-boont (Boontling dialect representation of English)
de-Latn-CH-1996 (German written in Latin script names of languages -- Part 2:
Alpha-3 code - edition 1", August 1988.

[3] ISO TC46/WG3, "ISO 15924:2003 (E/F) - Codes for Switzerland
using the orthography
representation of 1996)

Language-Region:
de-DE (German names of scripts", January 2004.

[4] International Organization for Germany)
zh-SG (Chinese Standardization, "Codes for the
representation of names of countries, 3rd edition",
ISO Standard 3166, August 1988.

[5] Statistical Division, United Nations, "Standard Country or Area
Codes for Singapore)
cs-200 (Czech Statistical Use", UN Standard Country or Area Codes
for Czechoslovakia)
sr-CS (Serbian Statistical Use, Revision 4 (United Nations publication,
Sales No. 98.XVII.9, June 1999.

[6] International Organization for Serbia Standardization, "ISO/IEC 10646-
1:2000. Information technology -- Universal Multiple-Octet
Coded Character Set (UCS) -- Part 1: Architecture and Montenegro)
es-419 (Spanish for Latin America Basic
Multilingual Plane and Caribbean region using the
UN region code)

Other Mixtures:
en-boont (Boontling dialect of English)

private-use mechanism:
de-CH-x-phonebk
az-Arab-x-AZE-derbend

Extended language subtags (examples ONLY: extended languages must be
defined ISO/IEC 10646-2:2001. Information
technology -- Universal Multiple-Octet Coded Character Set
(UCS) -- Part 2: Supplementary Planes, as, from time to time,
amended, replaced by revision a new edition or update to this document):
zh-min
zh-min-nan-Hant-CN

Private-use subtags:
x-whatever (private use using expanded by the singleton 'x')
qaa-Qaaa-QM-x-southern (all private tags)

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of new parts", 2000.

[7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", draft-crocker-abnf-rfc2234bis-00 (work
in progress), March 2005

de-Qaaa (German, with a private script)
de-Latn-QM (German, Latin-script, private region)
de-Qaaa-DE (German, private script, 2005.

[8] Bradner, S., "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.

[9] Hovey, R. and S. Bradner, "The Organizations Involved in the
IETF Standards Process", BCP 11, RFC 2028, October 1996.

[10] Bradner, S., "Key words for Germany)

Tags that use extensions (examples ONLY: extensions must be defined
by revision or update to this document or by RFC):
en-US-u-islamCal
zh-CN-a-myExt-x-private
en-a-myExt-b-another

Some Invalid Tags:
de-419-DE (two region tags)
a-DE (use of a single character subtag in primary position; note
that there are a few grandfathered tags that start with "i-" that
are valid)
ar-a-aaa-b-bbb-a-ccc (two extensions with same single letter
prefix) RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.

[11] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434,

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Appendix C. Conversion

October 1998.

[12] Hoffman, P. and F. Yergeau, "UTF-16, an encoding of the ISO 10646",
RFC 3066 Language Tag Registry

Upon publication 2781, February 2000.

[13] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of this document as a BCP,
Understanding Concerning the existing IANA
language tag registry must be converted into Technical Work of the new subtag registry.
This section defines Internet
Assigned Numbers Authority", RFC 2860, June 2000.

[14] Klyne, G. and C. Newman, "Date and Time on the process Internet:
Timestamps", RFC 3339, July 2002.

[15] Rescorla, E. and B. Korver, "Guidelines for performing this conversion.

The impact Writing RFC Text on
Security Considerations", BCP 72, RFC 3552, July 2003.

9.2 Informative References

[16] ISO 639 Joint Advisory Committee, "ISO 639 Joint Advisory
Committee: Working principles for ISO 639 maintenance",
March 2000,
<http://www.loc.gov/standards/iso639-2/iso639jac_n3r.html>.

[17] Raymond, E., "The Art of Unix Programming", 2003.

[18] Bray (et al), T., "Extensible Markup Language (XML) 1.0",
02 2004.

[19] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2:
Datatypes Second Edition", 10 2004, <
http://www.w3.org/TR/xmlschema-2/>.

[20] Unicode Consortium, "The Unicode Consortium. The Unicode
Standard, Version 4.1.0, defined by: The Unicode Standard,
Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-
18578-1), as amended by Unicode 4.0.1
(http://www.unicode.org/versions/Unicode4.0.1) and by Unicode
4.1.0 (http://www.unicode.org/versions/Unicode4.1.0).",
March 2005.

[21] Alvestrand, H., "Tags for the IANA maintainers Identification of Languages",
RFC 1766, March 1995.

[22] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word
Extensions: Character Sets, Languages, and Continuations",
RFC 2231, November 1997.

[23] Alvestrand, H., "Tags for the registry Identification of Languages",
BCP 47, RFC 3066, January 2001.

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Authors' Addresses

Addison Phillips (editor)
Quest Software

Email: addison.phillips@quest.com

Mark Davis (editor)
IBM

Email: mark.davis@us.ibm.com

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Appendix A. Acknowledgements

Any list of this conversion
will contributors is bound to be incomplete; please regard the
following as only a small increase in selection from the frequency of new entries. The
initial set group of records represents no impact on IANA, since the work people who have
contributed to create it will be performed externally.

When make this document what it is published, an email will be sent by today.

The contributors to RFC 3066 and RFC 1766, the
chair(s) precursors of the LTRU working group this
document, made enormous contributions directly or indirectly to the LTRU this
document and ietf-languages
mail lists advising of are generally responsible for the impending conversion success of the registry. In
that notice, the chair(s) will provide a URL whose referred content
is the proposed IANA Language Subtag Registry language
tags.

The following conversion.
There will be a Last Call period of not less than four weeks for
comments people (in alphabetical order) contributed to this
document or to RFCs 1766 and 3066:

Glenn Adams, Harald Tveit Alvestrand, Tim Berners-Lee, Marc Blanchet,
Nathaniel Borenstein, Eric Brunner, Sean M. Burke, M.T. Carrasco
Benitez, Jeremy Carroll, John Clews, Jim Conklin, Peter Constable,
John Cowan, Mark Crispin, Dave Crocker, Martin Duerst, Frank
Ellerman, Michael Everson, Doug Ewell, Ned Freed, Tim Goodwin, Dirk-
Willem van Gulik, Marion Gunn, Joel Halpren, Elliotte Rusty Harold,
Paul Hoffman, Scott Hollenbeck, Richard Ishida, Olle Jarnefors, Kent
Karlsson, John Klensin, Alain LaBonte, Eric Mader, Ira McDonald,
Keith Moore, Chris Newman, Masataka Ohta, Randy Presuhn, George
Rhoten, Markus Scherer, Keld Jorn Simonsen, Thierry Sourbier, Otto
Stolz, Tex Texin, Andrea Vine, Rhys Weatherley, Misha Wolf, Francois
Yergeau and corrections many, many others.

Very special thanks must go to be discussed on the
ietf-languages@iana.org mail list. Changes as a result of comments
will Harald Tveit Alvestrand, who
originated RFCs 1766 and 3066, and without whom this document would
not restart the Last Call period. At the end of the period, the
chair(s) will forward the URL have been possible. Special thanks must go to IANA, which will post the new
registry on-line.

Tags that are currently deprecated will be maintained Michael Everson,
who has served as
grandfathered entries. The record language tag reviewer for almost the grandfathered entry will
contain a note indicating that complete
period since the entry is 'deprecated' and reason publication of RFC 1766. Special thanks to Doug
Ewell, for his production of the deprecation. For example, the tag "art-lojban" is deprecated first complete subtag registry, and will be placed
his work in the grandfathered section. producing a test parser for verifying language tags.

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Appendix B. Examples of Language Tags that are not deprecated that consist entirely (Informative)

Simple language subtag:

de (German)

fr (French)

ja (Japanese)

i-enochian (example of subtags that
are valid under this document and which have a grandfathered tag)

Language subtag plus Script subtag:

zh-Hant (Chinese written using the correct form and
format for tags defined by this document are superseded by this
document. Such tags are placed Traditional Chinese script)

zh-Hans (Chinese written using the Simplified Chinese script)

sr-Cyrl (Serbian written using the Cyrillic script)

sr-Latn (Serbian written using the Latin script)

Language-Script-Region:

zh-Hans-CN (Chinese written using the Simlified script as used in
mainland China)

sr-Latn-CS (Serbian written using the 'redundant' section Latin script as used in
Serbia and Montenegro)

Language-Variant:

en-boont (Boontling dialect of English)

en-scouse (Scouse dialect of English)

Language-Region-Variant:

en-GB-scouse (Scouse dialect of English as used in the
registry. For example, zh-Hant is now defined by this document.

Tags that contain subtags which are consistent with registration
under UK)

Language-Script-Region-Variant:

sl-Latn-IT-nedis (Nadiza dialect of Slovenian written using the guidelines
Latin script as used in Italy. Note that this document will have a new tag is not
recommended because subtag
registration created for each eligible subtag. If all 'sl' has a Suppress-Script value of the subtags
'Latn')

Language-Region:

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de-DE (German for Germany)

en-US (English as used in the original tag are fully United States)

es-419 (Spanish for Latin America and Caribbean region using the
UN region code)

Private-use subtags:

de-CH-x-phonebk

az-Arab-x-AZE-derbend

Extended language subtags (examples ONLY: extended languages must be
defined by the resulting registrations revision or by this document, then the original tag is superseded by update to this
document. Such tags are placed in the 'redundant' section of document):

zh-min

zh-min-nan-Hant-CN

Private-use registry values:

x-whatever (private use using the
registry. For example, en-boont will result in singleton 'x')

qaa-Qaaa-QM-x-southern (all private tags)

de-Qaaa (German, with a new subtag "boont" private script)

sr-Latn-QM (Serbian, Latin-script, private region)

sr-Qaaa-CS (Serbian, private script, for Serbia and the RFC 3066 registered tag 'en-boont' placed in the redundant
section of the registry. Montenegro)

Tags that contain one or more subtags that do not match the valid
registration pattern and which are not otherwise use extensions (examples ONLY: extensions must be defined
by revision or update to this document are marked as 'grandfathered' or by this document. RFC):

en-US-u-islamCal

zh-CN-a-myExt-x-private

en-a-myExt-b-another

Some Invalid Tags:

de-419-DE (two region tags)

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There will be

a-DE (use of a reasonable period in which the community may comment
on the proposed list entries, which SHALL be no less than four weeks single character subtag 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
the task is complete and forward the necessary materials to IANA for
publication.

Registrations primary position; note
that there are in process under the rules defined in RFC 3066
MAY be completed under the former rules, at the discretion of the
language tag reviewer. Any new registrations submitted after the
request for conversion of the registry MUST be rejected.

All existing RFC 3066 language tag registrations will be maintained
in perpetuity.

Users of a few grandfathered tags that start with "i-" that
are grandfathered should consider registering
appropriate subtags in the IANA subtag registry (but are not required
to).

Where two subtags have the valid)

ar-a-aaa-b-bbb-a-ccc (two extensions with 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 single letter
prefix)

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Appendix C. Example Registry

Example Registry

File-Date: 2005-04-18
%%
Type: language
Subtag: aa
Description: Afar
Added: 2004-07-06
%%
Type: language
Subtag: ab
Description: Abkhazian
Added: 2004-07-06
%%
Type: language
Subtag: ae
Description: Avestan
Added: 2004-07-06
%%
Type: language
Subtag: ar
Description: Arabic
Added: 2004-07-06
Suppress-Script: Arab
Comment: Arabic text is not deprecated or
withdrawn as of that date, then it has priority.
o Otherwise, the earlier-registered tag usually written in the associated ISO
standard has priority.

UN numeric Arabic script
%%
Type: language
Subtag: qaa..qtz
Description: PRIVATE USE
Added: 2004-08-01
Comment: Use private use codes assigned to 'macro-geographical (continental)' or
sub-regions not associated with an assigned ISO 3166 alpha-2 code are
defined in preference
to the IANA registry and are valid x- singleton for use in primary language tags.
These codes MUST be added to the initial version
Comment: This is an example of the registry. two comments.
%%
Type: script
Subtag: Arab
Description: Arabic
Added: 2004-07-06
%%
Type: script
Subtag: Armn
Description: Armenian
Added: 2004-07-06
%%
Type: script
Subtag: Bali

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Description: Balinese
Added: 2004-07-06
%%
Type: script
Subtag: Batk
Description: Batak
Added: 2004-07-06
%%
Type: region
Subtag: AA
Description: PRIVATE USE
Added: 2004-08-01
%%
Type: region
Subtag: AD
Description: Andorra
Added: 2004-07-06
%%
Type: region
Subtag: AE
Description: United Arab Emirates
Added: 2004-07-06
%%
Type: region
Subtag: AX
Description: &#xC5;land Islands
Added: 2004-07-06
Comments: The UN numeric codes description shows a Unicode escape
for 'economic groupings' or 'other groupings',
and the alphanumeric codes letter A-ring.
%%
Type: region
Subtag: 001
Description: World
Added: 2004-07-06
%%
Type: region
Subtag: 002
Description: Africa
Added: 2004-07-06
%%
Type: region
Subtag: 003
Description: North America
Added: 2004-07-06
%%
Type: variant
Subtag: 1901
Description: Traditional German

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orthography
Added: 2004-09-09
Recommended-Prefix: de
Comment: <shows continuation>
%%
Type: variant
Subtag: 1996
Description: German orthography of 1996
Added: 2004-09-09
Recommended-Prefix: de
%%
Type: variant
Subtag: boont
Description: Boontling
Added: 2003-02-14
Recommended-Prefix: en
%%
Type: variant
Subtag: gaulish
Description: Gaulish
Added: 2001-05-25
Recommended-Prefix: cel
%%
Type: grandfathered
Tag: art-lojban
Description: Lojban
Added: 2001-11-11
Canonical: jbo
Deprecated: 2003-09-02
%%
Type: grandfathered
Tag: en-GB-oed
Description: English, Oxford English Dictionary spelling
Added: 2003-07-09
%%
Type: grandfathered
Tag: i-ami
Description: 'Amis
Added: 1999-05-25
%%
Type: grandfathered
Tag: i-bnn
Description: Bunun
Added: 1999-05-25
%%
Type: redundant
Tag: az-Arab
Description: Azerbaijani in Appendix X Arabic script

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Added: 2003-05-30
%%
Type: redundant
Tag: az-Cyrl
Description: Azerbaijani in Cyrillic script
Added: 2003-05-30
%%

Figure 7: Example of the UN document MUST NOT
be added to the registry. Registry Format

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This document and the information contained herein are provided on an
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Copyright (C) The Internet Society (2005). This document is subject
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Acknowledgment

Funding for the RFC Editor function is currently provided by the
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