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Versions: 00                                                            
Internet Draft                                    Marc Blanchet
<draft-blanchet-preflang-00.txt>                  Viagenie inc.
Expires in six months                             February 1998



                    Preferred Language Tag



                     Status of this Memo

This document is an Internet-Draft.  Internet-Drafts are
working documents of the Internet Engineering Task Force
(IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum of six
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than as a "working draft" or "work in progress".

To learn the current status of any Internet-Draft, please
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Internet-Drafts Shadow Directories on ds.internic.net (US East
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or munnari.oz.au (Pacific Rim).


1.  Abstract

This memo defines a new tag which will help users and servers
to determine the best language in their communications.
For example, error messages coming from SMTP servers or HTTP servers
can use this tag to send those error messages in the preferred
language for the user.


2.  Introduction

Messages sent by servers or applications to users are often in
the english language because the server or the application have
no prior knowledge of the preferred language of the end user.
Sometimes, servers or applications send messages in the proper
language of the user but they were preconfigured with a priori
knowledge of the end user.  In the context of internationalization
of the Internet and in the context of internationalization of the
protocols as discussed in [RFC-2277], it is much useful to know a
priori which language a user wants to interact with.

Since many protocols do not necessarily interact with
the user by some negociation, like two SMTP servers relaying a
email message, there is a need to give a list of preferred
languages in order inside the tag, so that if, for example,
a user is requesting french, swedish and then english as preferred
languages, the server who don't have french error messages, will
send the message in swedish or in english.


2.1. Other tags

HTTP [RFC-2068] defines the tag Accept-Language, which defines not only
a preferred language tag, but also a language quality factor assigned
to it.  Current work on LDAP[ldapextlang] defines an attribute type.


2.2.  Requirements notation

This document occasionally uses terms that appear in capital
letters. When the terms "MUST", "SHOULD", "MUST NOT", "SHOULD
NOT", and "MAY" appear capitalized, they are being used to
indicate particular requirements of this specification. A
discussion of the meanings of these terms appears in [RFC-
2119].


3.  Preferred Language Tag

Language tag mechanism has been described in RFC-1766. This memo
defines a new tag: Prefer-Language  to specify the list of preferred
languages that the user (or to be more general, the issuer of
this tag which can be a process, server, ...) wants to receive
when communicating with other parties.

The values and the syntax associated with this new tag are those
defined in RFC-1766.  The language strings are separated by
commas. The order of preference is from left to right, the first
in the left position being the most preferred one.

For example, this tag will specify that a user prefer french, if
not possible deutsh, if not possible english:

           Prefer-Language: fr, de, en

4. Processing the tag

This tag is optional.  A server or a client MAY ignore it.
But all proxies or forwarders MUST forward it.

5. Default language

This memo defines no implicit default language. Default language
is discussed in [RFC-2277].

6. Placement of the tag

This new tag will be normally placed in the headers of the protocols
that use them.  This memo do not attend to list protocols and
specify where to place them.

It is envisionned that software developers will put a config option, so
the user can fill his requirements and the client software will send
those tags in all communications.

7. ABNF

The ABNF for this new tag is:

preferred-language := "Prefer-Language" "=" language (separator language )

separator := ","

language := <registered language tag [RFC-1766]>


8.  Security Considerations

The knowledge of a user's preferred language can
help an attacker to impersonate the user by giving the receipient more
confidence on the sender of the message.

The applications that will process this tag should take care of
restricting the values read in the tag to the syntax, so that
if an attacker insert shell scripts or escapes in the
values of these tags, they will not be interpreted by the application.


9. Acknowledgments

Many thanks for the very constructive comments of:
Harald T. Alverstrand, Martin J. Duerst, John Myers, Francois Yergeau


10.  References

[ldapextlang]
     Whal, M. and Howes, T.,  "Use of Language Codes in LDAP",
     work in progress (draft-ietf-ldapext-lang-00.txt), January
     1998.

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

[RFC-2045]
     Freed, N. and Borenstein, N., "Multipurpose Internet Mail
     Extensions (MIME) Part One: Format of Internet Message
     Bodies", RFC 2045, Innosoft, First Virtual Holdings,
     December 1996.

[RFC-2119]
     Bradner, S., "Key words for use in RFCs to Indicate
     Requirement Levels", RFC 2119, March 1997.

[RFC-2130]
     Weider, C., Preston, C., Simonsen, K., Alvestrand, H.,
     Atkinson, R., Crispin, M., Svanberg, P., "Report from the
     IAB Character Set Workshop", RFC 2130, April 1997.

[RFC-2277]
     Alvestrand, H., "IETF Policy on Character Sets and Languages"
     RFC 2277, January 1998.


11.  Author Address

Marc Blanchet
Viagenie Inc.
3107 des hotels
Ste-Foy, Quebec, G1W 4W5
Canada
tel: +1 418 656-9254
fax: +1 418 656-0183
email: Marc.Blanchet@viagenie.qc.ca
Prefer-Language: fr, en



12. Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.






-----------------------------------------------------------
Marc Blanchet                   | Marc.Blanchet@viagenie.qc.ca
Viagenie inc.                   | http://www.viagenie.qc.ca
3107 des hotels         | tel.: 418-656-9254
Ste-Foy, Quebec         | fax.: 418-656-0183
Canada, G1W 4W5         | radio: VA2-JAZ
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Auteur du livre TCP/IP Simplifié, Editions Logiques, 1997
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