WITHIN Search extension to the IMAP
ProtocolBEA Systems, Inc.USAeric.burger@bea.comhttp://www.standardstrack.comexample
Applications
LemonadeThis document describes the WITHIN extension to IMAP SEARCH. IMAP
SEARCH returns messages whose internal date is within or outside a
specified interval. The mechanism described here, OLDER and YOUNGER,
differs from BEFORE and SINCE in that the client specifies an interval,
rather than a date. WITHIN is useful for persistent searches where
either the device does not have the capacity to perform the search at
regular intervals or the network is of limited bandwidth and thus there
is a desire to reduce network traffic from sending repeated requests and
redundant responses.This extension exposes two new search keys, OLDER and YOUNGER, each
of which takes a non-zero integer argument corresponding to a time
interval in seconds. The server calculates the time of interest by
subtracting the time interval the client presents from the
current date and time of the server. The server then either returns
messages older or younger than the resultant time and date, depending
on the search key used.In examples, "C:" and "S:" indicate lines sent by the client and
server, respectively.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.When describing the general syntax, we omit some definitions, as RFC 3501 defines them.An IMAP4 server that supports the capability described here MUST
return "WITHIN" as one of the server supported capabilities in the
CAPABILITY command.For both the OLDER and YOUNGER search keys, the server calculates a
target date and time by subtracting the interval, specified in seconds,
from the current date and time of the server. The server then compares
the target time with the INTERNALDATE of the message, as specified in
IMAP. For OLDER, messages match if the
INTERNALDATE is less recent than or equal to the target time. For
YOUNGER, messages match if the INTERNALDATE is more recent than or
equal to the target time.Both OLDER and YOUNGER searches always result in exact matching, to
the resolution of a second. However, if one is doing a dynamic
evaluation, for example, in a context, one
needs to be aware that the server might perform the evaluation periodically.
Thus, the server may delay the updates. Clients MUST be aware that
dynamic search results may not reflect the current state of the mailbox.
If the client needs a search result that reflects the current state of
the mailbox, we RECOMMEND that the client issue a new search.The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation. Elements not defined here can be found in the
formal syntax of ABNF and IMAP.This document extends RFC 3501 with two
new search keys: OLDER <interval> and YOUNGER
<interval>.Search for all unseen messages within the past 3 days, or 259200
seconds, according to the server's current time.The WITHIN extension does not raise any security considerations that
are not present in the base protocol. Considerations are the same as for
IMAP.Per the IMAP RFC, registration of a new
IMAP capability in the IMAP Capability registry requires the publication
of a standards-track RFC or an IESG approved experimental RFC. The
registry is currently located at
<http://www.iana.org/assignments/imap4-capabilities>. This
standards-track document defines the WITHIN IMAP capability.
IANA has added this extension to the IANA IMAP Capability registry.Key words for use in RFCs to Indicate Requirement
LevelsInternet Message Access Protocol - Version 4rev1University of WashingtonAugmented BNF for Syntax Specifications: ABNFContexts for IMAP4Isode LimitedIsode LimitedStephane Maes and Ray Cromwell wrote the original version of this
document as part of P-IMAP, as well as the first versions for the IETF.
From an attribution perspective, they are clearly authors.The authors want to thank all who have contributed key insight and
who have extensively reviewed and discussed the concepts of
LPSEARCH. They also thank the authors of its early introduction in P-IMAP.We also want to give a special thanks to Arnt Gilbrandsen, Ken
Murchison, Zoltan Ordogh, and most especially Dave Cridland for their
review and suggestions. A special thank you goes to Alexey Melnikov for
his choice submission of text.