Subject: Protocol Action: 'Sieve Extension: Variables' to Proposed Standard

From: The IESG <[email-masked]>
Date: Tue, 24 Jan 2006 17:19:18 -0500

The IESG has approved the following document:

- 'Sieve Extension: Variables '
   <draft-ietf-sieve-variables-08.txt> as a Proposed Standard

This document is the product of the Sieve Mail Filtering Language Working 
Group. 

The IESG contact persons are Scott Hollenbeck and Ted Hardie.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-sieve-variables-08.txt

Technical Summary

In advanced mail filtering rule sets, it is useful to keep state or
configuration details across rules.  This extension to the filtering
language Sieve changes the interpretation of strings, adds an action
to store data in variables, and supplies a new test so that the value
of a string can be examined.  This document updates RFC 3028.

Working Group Summary
 
The discussion about adding variables to the SIEVE mail filtering
language started 4-5 years ago during development of the IMAP flags
extension to SIEVE. The latter has been using a single implicit global
variable and several mailing list participants have expressed their wish
to have a more generic method of keeping state or configuration details
across rules. The ability to extract matching material from header fields
and perform further tests on it has also proven to be very useful. This
became even more apparent when the SIEVE regular expression draft was
written.

The document is minimalistic in its approach: several less used features
like automatically set current date/time variables got dropped from the 
document.

There was a discussion about having read-only variables automatically
set from different RFC 2822 message headers. There was no consensus to
add this to the document.

There was a discussion about having locally scoped variables. The
general feeling was that this feature complicates implementations quite
a bit for a feature very few Sieve scripts will find use for. So there
was no consensus to add this to the document, however, should the need
arise, it would be possible to add locally scoped variables as an 
extension.

Several WG members have proposed adding associative arrays. Some people
felt that this might be useful, but it will introduce extra implementation
complexity and could lead to implementation bugs. The WG has decided that
this can be postponed till later; the current "variables" document
doesn't prohibit this.
 
Protocol Quality

The WG asked the Security Area to perform a review of the document.
Two changes to the document has been done as the result of the review:
additional text in Security Considerations about silent truncation of
big values and an additional :quotewildcard modifier which gives a
convenient way to escape special matching characters in strings. Both
changes were discussed in details on the mailing list and have WG
consensus behind them.

There are already several implementations of the variables extension in
servers and more people have indicated that they are planning to 
implement it.
 
Scott Hollenbeck has reviewed this specification for the IESG.  Love
Hornquist Astrand and Jeffrey Hutzelman performed a security review
of the document.

Note to the RFC Editor

Please remove Section 0 from the document.

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