Lemonade E. Burger, Ed.
Internet-Draft BEA Systems, Inc.
Intended status: Standards Track R. Cromwell
Expires: August 27, 2007 S. Maes
Oracle Corporation
February 23, 2007
WITHIN Search extension to the IMAP Protocol
draft-ietf-lemonade-search-within-04
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Copyright (C) The IETF Trust (2007).
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Abstract
This 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. We expect WITHIN to be most useful for
persistent searches from mobile devices.
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Conventions Used in this Document
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 [1].
When describing the general syntax, we omit some definitions as RFC
3501 [2] defines them.
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1. Introduction
This extension exposes two new search keys, OLDER and YOUNGER, each
of which takes a non-zero integer argument corresponding to a time
interval. The server calculates the time of interest by subtracting
the time interval presented by the client, and either returning
messages older or younger than the resultant time and date.
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2. Protocol Operation
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 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 [2].
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.
In some cases, the server may be unable, or unwilling, to use a
precision of a single second. This is expected to be the case
particularly for dynamically updated searches. In these cases,
servers are permitted to reduce the precision used for date
calulcations and comparisons, but SHOULD ensure that a precision of
no less than an hour (3600 seconds) is used. This might mean re-
running the search criteria only every hour for a dynamic search, for
example. Clients MUST be aware that search results, whether viewed
directly or through some other mechanism, MAY not be accurate as a
result.
For example, if the client requests messages that are younger than
4020 (67 minutes), but the server only performs searches with hourly
accuracy (as mandated above), the server performs the search as if
the client requested a 60-minute interval. Note the choice of
rounding up or down is at the discretion of the server. However,
rounding down to zero is NOT RECOMMENDED, as this may result in
searches for messages YOUNGER than a value being rounded to YOUNGER
0, which will always fail.
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3. Formal Syntax
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 [1], IMAP [2], and IMAP Extended ABNF [3]
This document extends RFC 3501 [2] with two new search keys: OLDER
<interval> and YOUNGER <interval>.
search-key /= ( "OLDER" | "YOUNGER" ) SP nz-number
; search-key defined in RFC 3501
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4. Example
C: a1 SEARCH UNSEEN YOUNGER 259200
S: a1 * SEARCH 4 8 15 16 23 42
Search for all unseen messages within the past 3 days (72 hours)
according to the server's current time.
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5. Security Considerations
The WITHIN extension does not raise any security considerations which
are not present in the base protocol. Considerations are the same as
for IMAP [2].
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6. IANA Considerations
None.
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7. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[2] Crispin, M., "Internet Message Access Protocol - Version 4rev1",
RFC 3501, March 2003.
[3] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 ABNF",
RFC 4466, April 2006.
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Appendix A. Acknowledgements
The authors want to thank all who have contributed key insight and
extensively reviewed and discussed the concepts of LPSEARCH and the
authors of its early introduction in P-IMAP.
We also want to give a special thanks to Arnt Gilbrandsen, Alexey
Melnikov, Ken Murchison, Zoltan Ordogh, and most especially Dave
Cridland for their review and suggestions.
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Authors' Addresses
Eric W. Burger (editor)
BEA Systems, Inc.
USA
Phone:
Fax:
Email: eric.burger@bea.com
URI:
Ray Cromwell
Oracle Corporation
500 Oracle Parkway
Redwood Shores, CA 94065
USA
Email: ray.cromwell@oracle.com
Stephane H. Maes
Oracle Corporation
500 Oracle Parkway, M/S 4op634
Redwood Shores, CA 94065
USA
Email: stephane.maes@oracle.com
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