Subject: WG Review: Language Tag Registry Update (ltru)

From: The IESG <[email-masked]>
Date: Thu, 24 Feb 2005 14:16:50 -0500

A new IETF working group has been proposed in the Applications Area.  
The IESG has not made any determination as yet. The following description 
was submitted, and is provided for informational purposes only. Please send 
your comments to the IESG mailing list ([email-masked]) by March 2nd.

+++

Language Tag Registry Update (LTRU)
====================================

Current Status: Proposed Working Group

Description of Working Group:

RFC 3066 and its predecessor, RFC 1766, defined language tags for use
on the Internet. Language tags are necessary for many applications,
ranging from cataloging content to computer processing of text. The
RFC 3066 standard for language tags has been widely adopted in various
protocols and text formats, including HTML, XML, and CLDR, as the best
means of identifying languages and language preferences.  Since the
publication of RFC 3066, however, several issues have faced
implementors of language tags:

    * Stability and accessibility of the underlying ISO standards
    * Difficulty with registrations and their acceptance
    * Lack of clear guidance on how to identify script and region where 
      necessary
    * Lack of parseability and the ability to verify well-formedness.
    * Lack of specified algorithms, apart from pure prefix matching, 
      for operations on language tags.
 
This working group will address these issues by developing two
documents. The first is a successor to RFC 3066.  It will describe the
structure of the IANA registry and how the registered tags will relate
to the generative mechanisms (originally described in RFC 3066, but
likely to be updated by the document).  In order to be complete, it
will need to address each of the challenges set out above:

- For stability, it is expected that the document will describe how
the meaning of language tags remains stable, even if underlying
references should change, and how the structure is to remain stable in
the future. For accessibility, it is to provide a mechanism for easily
determining whether a particular subtag is valid as of a given date,
without onerous reconstruction of the state of the underlying standard
as of that time.

- For extensibility, it is expected that the document will describe
how generative mechanisms could use ISO 15924 and UN M.49 codes
without explicit registration of all combinations. The
current registry contains pairs like uz-Cyrl/uz-Latn and
sr-Cyrl/sr-Latn, but RFC 3066 contains no general mechanism or
guidance for how scripts should be incorporated into language tags;
this replacement document is expected to provide such a mechanism. 

- It is also expected to provide mechanisms to support the evolution 
of the underlying ISO standards, in particular ISO 639-3, mechanisms to
support variant registration and formal extensions, as well as
allowing generative private use when necessary.

- It is expected to specify a mechanism for easily identifying the role of 
each subtag in the language tag, so that, for example, whenever a script 
code or country code is present in the tag it can be extracted, even without 
access to a current version of the registry. Such a mechanism would clearly
distinguish between well-formed and valid language tags, to allow for
maximal compatibility between implementations released at different
times, and thus using different versions of the registry.

The second document will describe matching algorithms for use with
language tags.  Language tags are used in a broad variety of contexts
and it is not expected that any single matching algorithm will fit all
needs.  Developing a small set of common matching and sorting
algorithms does seem likely to contribute to interoperability,
however, as it seems likely that using protocols could reference these
well-known algorithms in their specifications.  

This working group will not take over the existing review function of 
the ietf-languages list.  The ietf-languages list will continue to review
tags according to RFC 3066 until the first document produced by the WG
is finished.  Then it will review according to whatever procedures the
first document specifies.

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