Dear Email Experts,
I have just submitted an update of the Archived-At proposal.
It should appear at
http://www.ietf.org/internet-drafts/draft-duerst-archived-at-02.txt
within a few days, and is also appended below.
I hope that this new draft, together with the various emails sent
out a moment ago, sufficiently addresses the comments that have
been made on previous versions of this proposal. Of course, I was
not able to fully take into account all of the comments made, because
there were some contradicting opinions as well as some interesting
ideas that however didn't match deployed usage.
I would highly appreciate any additional feedback and comments on
the draft. Please copy me directly, as I'm not subscribed to this list.
Regards, Martin.
=========================================================================
Network Working Group M. Duerst
Internet-Draft W3C/Keio University
Expires: April 25, 2005 October 25, 2004
The Archived-At Message Header Field
draft-duerst-archived-at-02
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This memo defines a new email header field, Archived-At:, to provide
a direct link to the archived form of an individual email message.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Syntax Definition . . . . . . . . . . . . . . . . . . . . . . 3
3. Multiple Archived-At Header Fields . . . . . . . . . . . . . . 4
4. Formats of Archived Message . . . . . . . . . . . . . . . . . 4
5. Implementation Considerations . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . 8
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1. Introduction
[RFC2369] defines a number of header fields that can be added to
email messages sent by email distribution lists. One of them is the
'List-Archive' header field that describes how to access archives for
the list. This allows to access the archives as a whole, but not the
individual message.
There is often a need or desire to refer to the archived form of a
single message. This memo defines a new header, 'Archived-At', to
refer to a single message at an archived location. This can help to
find a message to a mailing list in the archive of that mailing list
much more quickly and directly. It can also be used independently of
mailing lists, for example in connection with legal requirements to
archive certain messages.
2. Syntax Definition
The name of the header field is 'Archived-At'. The content of the
header field mostly consist of an URI [RFCXXXX] enclosed in angle
brackets ('<', '>'), with internal whitespace being ignored. MTAs
MUST NOT insert whitespace within the angle brackets, but client
applications should treat any whitespace, which might have been
inserted by poorly behaved MTAs, as characters to ignore. The URI
points to an archived version of the message. See Section 4 for some
more details.
This header field is subject to the encoding and character
restrictions for mail headers as described in [RFC2822].
Additionally, the URI content is further restricted to the set of URI
safe characters [RFCXXXX].
More formally, the header field is defined as follows in ABNF
according to [RFC2234]:
archived-at = "Archived-At:" '<' URI '>' CRLF ; URI not empty
where URI is defined in [RFCXXXX] and CRLF is defined in [RFC2234].
For backward-compatibility, the following MAY also be parsed (but
MUST not be generated):
obs-archived-at = "X-Archived-At:" URI CRLF ; URI not empty
This syntax is kept simple in that only one URI per header field is
allowed. In this point, the syntax is different from [RFC2369].
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3. Multiple Archived-At Header Fields
If a message is archived at several independent locations, several
header fields MUST be used. Multiple Archived-At header fields with
the same URI SHOULD be avoided. An Archived-At header field MUST
only be created if the message is actually being made available at
the URI given in the header field.
If a message is forwarded from a list to a sublist, and both lists
support adding the Archived-At header field, then the sublist SHOULD
add a new Archived-At header field without removing the already
existing one(s), unless the header field is exactly the same as an
already existing one, in which case the new header field SHOULD NOT
be added.
4. Formats of Archived Message
There is no restriction on the format used to serve the archived
message from the URI in the 'Archived-At' header field. It is
expected that in many cases, the archived message will be served as
(X)HTML, as plain text, or as message/rfc822 [RFC2046]. Some forms
of URIs may imply the format in which the archived message is served,
although this should not be relied upon. If the protocol used to
retrieve the message allows for content negotiation, then it is also
possible to serve the archived message in several different formats.
As an example, a HTTP URI in an 'Archived-At' header may allow to
serve the archived message both as text/html for human consumption in
a browser and as message/rfc822 for use by a mail user agent without
loss of information.
5. Implementation Considerations
This section shortly discusses some implementation considerations.
Mailing list expanders and email archives are often separate pieces
of software. It may therefore be difficult to create an
'Archived-At' header field in the mailing list expander software.
One way to address this difficulty is to have the mailing list
expander software generate an unambiguous URI, e.g. an URI based on
the message id of the incoming email, and to set up the archiving
system so that it redirects requests for such URIs to the actual
messages.
Such a system has been implemented and is in productive use at W3C.
As an example, the URI
"http://www.w3.org/mid/0I5U00G08DFGCR(_at_)mailsj-v1(_dot_)corp(_dot_)adobe(_dot_)com",
containing the message id
"0I5U00G08DFGCR(_at_)mailsj-v1(_dot_)corp(_dot_)adobe(_dot_)com",
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is redirected to the URI of this message in the W3C mailing-list
archive at http://lists.w3.org/Archives/Public/uri/2004Oct/0017.html.
Source code for this implementation is available at
http://dev.w3.org/cvsweb/search/, in particular
http://dev.w3.org/cvsweb/search/cgi/mid.pl and
http://dev.w3.org/cvsweb/search/bin/msgid-db.pl.
When using the message id to create an address for the archived mail,
care has to be taken to escape characters in the message id that are
not allowed in the URI.
6. Security Considerations
There are many potential security issues when activating and
dereferencing an URI. For more details, please see [RFCXXXX]. In
the context of this proposal, the following are particularly
relevant: An intruder may get access to the message transmission and
be able to insert an URI pointing to some malicious content. Also,
somebody may be able to construct a message that when received
directly is harmless, but that when accessed via the URI produces
some problems because in the format used in the archive, some content
has not been adequately escaped.
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7. IANA considerations
IANA is herewith requested to register the Archived-At header field
in the Message Header Fields Registry as follows:
Header field name:
Archived-At
Applicable protocol:
mail (RFC 2822), optionally also netnews (RFC 1036)
Status:
provisional
(Note to RFC Editor: Replace this with "standard")
Author/Change controller:
Martin Duerst, duerst(_at_)w3(_dot_)org, W3C/Keio University
(Note to RFC Editor: Replace this with "IETF")
Specification document(s):
Internet-Draft draft-duerst-archived-at-02.txt
(Note to RFC Editor: Replace this with
RFC YYYY (RFC number of this spec))
Related information:
none
8. Acknowledgements
The members of the W3C system team, in particular Gerald Oskoboiny,
Olivier Thereaux, and Jose Kahan, created the mid-based email archive
lookup system and the experimental form of the Archived-At header.
Pete Resnik provided the motivation for writing up this memo.
Discussion on the ietf-822(_at_)imc(_dot_)org mailing list, in particular
contributions by Arnt Gulbrandsen, Graham Klyne, Bruce Lilly, Charles
Lindsey, and Keith Moore, has led to further improvements of the
proposal.
9 Normative References
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2369] Baer, J. and G. Neufeld, "The Use of URLs as Meta-Syntax
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for Core Mail List Commands and their Transport through
Message Header Fields", RFC 2369, July 1998.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[RFC3864] Klyne, G., Nottingham, M. and J. Mogul, "Registration
Procedures for Message Header Fields", RFC 3864, BCP 90,
September 2004.
[RFCXXXX] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax",
draft-fielding-uri-rfc2396bis-07.txt (work in progress),
April 2004.
Author's Address
Martin Duerst (Note: Please write "Duerst" with u-umlaut wherever
possible, for example as "Dürst" in XML and HTML.)
World Wide Web Consortium/Keio University
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Phone: +81 466 49 1170
Fax: +81 466 49 1171
EMail: mailto:duerst(_at_)w3(_dot_)org
URI: http://www.w3.org/People/D%C3%BCrst/
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