Network Working Group M. Gahrns, Microsoft
A. McCown, Mitsubishi Electric ITA
Internet Draft
Document: draft-gahrns-imap-language-00.txt November 1997
IMAP4 Language Extension
Status of this Memo
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1. Abstract
The Internet Message Access Protocol [RFC-2060] allows server
responses to include human-readable text that in many cases needs to
be presented to the user. This document specifies a way for a
client to negotiate which language the server should use when
sending human-readable text.
2. Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively. If such lines are wrapped without a new "C:"
or "S:" label, then the wrapping is for editorial clarity and is not
part of the command.
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].
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IMAP4 Language Extension November 1997
3. Requirements
IMAP4 servers that support this extension MUST list the keyword
LANGUAGE in their CAPABILITY response.
A server that supports this extension SHOULD use the language "i-
default" as described in [CHARSET-POLICY] as its default language
until another supported language is negotiated by the client. A
server MUST include "i-default" as one of its supported languages.
The LANGUAGE command is valid in the non-authenticated,
authenticated and selected state.
4. LANGUAGE Command
Arguments: Zero or one language tag as defined by [RFC-1766].
Response: A possible LANGUAGE response containing the list of
server supported languages.
A possible NAMESPACE response as defined by [IMAP-
NAMESPACE].
Result: OK - Command completed
NO - Could not complete command
BAD - arguments invalid
The LANGUAGE command requests that human-readable text emitted by
the server be localized to the language specified in the language
tag argument.
If the command succeeds, the server will return human-readable
responses in the specified language starting with the tagged OK
response to the LANGUAGE command. These responses will be in UTF-8
[RFC-2044].
If the command fails, the server will continue to return human-
readable responses in the language it was previously using.
Example 4.1
===========
< The server defaults to using English responses until the user
explicitly changes the language. >
C: A001 LOGIN KAREN PASSWORD
S: A001 OK LOGIN completed
< Once the client changes the language, all responses will be in
that language starting with the tagged OK to the LANGUAGE command. >
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IMAP4 Language Extension November 1997
C: A002 LANGUAGE FR
S: A002 OK La Language commande a ete executee avec success
< If a server does not support the requested language, responses
will continue to be returned in the current language the server is
using. >
C: A003 LANGUAGE DE
S: A003 NO Ce Language n'est pas supporte
If the language tag argument is omitted, the server SHOULD send an
untagged LANGUAGE response listing the languages it supports. If
the server is unable to enumerate the list of languages it supports
it MAY return a tagged NO response to the enumeration request.
Example 4.2
===========
< A LANGUAGE command with no arguments is a request to enumerate the
list of languages the server supports. >
C: A001 LANGUAGE
S: * LANGUAGE (EN DE IT i-default)
S: A001 OK Supported languages have been enumerated
C: A001 LANGUAGE
S: A002 NO Server is unable to enumerate supported languages
If the server supports the IMAP4 NAMESPACE command [IMAP-NAMESPACE],
the server SHOULD return an untagged NAMESPACE response if namespace
information changed as a result of the LANGUAGE command. Note that
the namespace prefix is to a mailbox and following IMAP4 convention,
any international string in the NAMESPACE response MUST be of
modified UTF-7 format as described in [RFC-2060].
Example 4.3
===========
< In this example a server supports the IMAP4 NAMESPACE command. It
uses no prefix to the user's Personal Namespace, a prefix of "Other
Users" to its Other Users' Namespace and a prefix of "Public
Folders" to its only Shared Namespace. Since a client will often
display these prefixes to the user, the server changes these based
on the language of the connecting client. >
C: A001 LANGUAGE FR-CA
S: * NAMESPACE (("" "/"))(("Autres Utilisateurs/" "/")) (("Dossiers
Publics" "/")
S: A001 OK La Language commande a ete executee avec success
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IMAP4 Language Extension November 1997
Note: A server should be aware that changing the namespace prefixes
based upon the language of the connecting client can invalidate
mailbox URLs that are shared by clients of various languages.
Addressing this issue is outside the scope of this document, and is
part of a much larger problem of how a client should share/send urls
to a particular mailbox that may be represented differently by the
server based upon the identity of the connected user.
5. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) as described in [ABNF].
LANGUAGE_Command = "LANGUAGE" [SP <language_tag>]
LANGUAGE_Response = "*" SP "LANGUAGE" SP "(" 1*<language_tag> ")"
; Note: the server is required to support the language i-default
; and as such i-default must appear in the language response.
; Although primarily English text, the "i-default" language may
; contain some non-English text.
; Any international characters in the "i-default" response
; text MUST be encoded as per <text_mime2> as defined in
; [RFC-2060] and not as <text_utf8>
<language_tag> = <language_tag> as defined in [RFC-1766]
; After the server is changed to a language other than English, the
resp_text as defined by [RFC-2060] becomes:
resp_text = ["[" <resp_text_code> "]" SP <text_utf8>
; <resp_text_code as defined in RFC-2060
; <text_utf8> any valid UTF-8 character as defined in [RFC-2044]
6. Security Considerations
This extension allows the negotiation of a language for the human-
readable text returned by a server. A user is able to query the
languages that a server supports.
7. References
[RFC-1766], Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766, UNINETT, March 1995
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IMAP4 Language Extension November 1997
[RFC-2044], Yergeau, F., " UTF-8, a transformation format of Unicode
and ISO 10646, RFC 2044, Alis Technologies, October, 1996
[RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 2060, University of Washington, December 1996.
[RFC-2119], Bradner, S, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997
[ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
Syntax Specifications: ABNF", draft-drums-abnf-04.txt (work in
progress), Internet Mail Consortium, September 1997
[CHARSET-POLICY], Alvestrand, H., "IETF Policy on Character Sets and
Languages", draft-alvestrand-charset-policy-02.txt (work in
progress), UNINETT, October 1997
[IMAP-NAMESPACE], Gahrns, M., "IMAP4 Namespace", draft-gahrns-imap-
namespace-05.txt (work in progress), Microsoft, November 1997
8. Acknowledgments
Many people have participated in discussions about an IMAP Language
extension in the various fora of the IETF and the internet working
groups, so any list of contributors is bound to be incomplete.
However, the authors would like to thank John Myers and Chris Newman
for their suggestions regarding the namespace issue and Larry
Osterman for his review of this document.
9. Author's Address
Mike Gahrns
Microsoft
One Microsoft Way
Redmond, WA, 98072
Phone: (425) 936-9833
Email: mikega@microsoft.com
Andrew McCown
Mitsubishi Electric ITA
1432 Main St.
Waltham MA, 02154
Email: andy@meitca.com
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