BCP 47 Extension U
RFC 6067

Document Type RFC - Informational (December 2010; Errata)
Was draft-davis-u-langtag-ext (individual in app area)
Last updated 2015-05-13
Stream IETF
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Stream WG state (None)
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IESG IESG state RFC 6067 (Informational)
Telechat date
Responsible AD Alexey Melnikov
Send notices to addison@lab126.com, mark@macchiato.com, yoshito_umaoka@us.ibm.com, draft-davis-u-langtag-ext@ietf.org
Internet Engineering Task Force (IETF)                          M. Davis
Request for Comments: 6067                                        Google
Category: Informational                                      A. Phillips
ISSN: 2070-1721                                                   Lab126
                                                               Y. Umaoka
                                                                     IBM
                                                           December 2010

                           BCP 47 Extension U

Abstract

   This document specifies an Extension to BCP 47 that provides subtags
   that specify language and/or locale-based behavior or refinements to
   language tags, according to work done by the Unicode Consortium.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6067.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Davis, et al.                 Informational                     [Page 1]
RFC 6067             BCP 47 Unicode Locale Extension       December 2010

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 2
   2.  BCP 47 Required Information . . . . . . . . . . . . . . . . . . 2
     2.1.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 4
       2.1.1.  Canonicalization  . . . . . . . . . . . . . . . . . . . 5
     2.2.  Registration Form . . . . . . . . . . . . . . . . . . . . . 6
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 7

1.  Introduction

   [BCP47] permits the definition and registration of language tag
   extensions "that contain a language component and are compatible with
   applications that understand language tags".  This document defines
   an extension for identifying Unicode locale-based variations using
   language tags.  The "singleton" identifier for this extension is 'u'.

1.1.  Requirements Language

   The key words "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 [RFC2119].

2.  BCP 47 Required Information

   Language tags, as defined by [BCP47], are useful for identifying the
   language of content.  They are also used as locale identifiers (or
   can be mapped to locales) in many operating environments and APIs.
   However, many locale identifiers also require additional "tailorings"
   or options for specific values within a language, culture, region, or
   other variation.  This extension provides a mechanism for using these
   additional tailorings within language tags for general interchange.

   The Unicode Consortium defines a standardized, structured set of
   locale data and identifiers for locale data in the "Common Locale
   Data Repository" or "CLDR".  The maintaining authority for the
   extension defined by this document is the Unicode Consortium:
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