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rfc:rfc5032

Network Working Group E. Burger, Ed. Request for Comments: 5032 BEA Systems, Inc. Updates: 3501 September 2007 Category: Standards Track

            WITHIN Search Extension to the IMAP Protocol

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

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.  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.

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 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.

1.1. 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 [RFC2119].

Burger Standards Track [Page 1] RFC 5032 Search Within September 2007

 When describing the general syntax, we omit some definitions, as RFC
 3501 [RFC3501] defines them.

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, 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 [RFC3501].  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 [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.

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 [RFC4234] and IMAP [RFC3501].
 This document extends RFC 3501 [RFC3501] with two new search keys:
 OLDER <interval> and YOUNGER <interval>.
 search-key =/ ( "OLDER" / "YOUNGER" ) SP nz-number
                ; search-key defined in RFC 3501

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, or 259200
 seconds, according to the server's current time.

Burger Standards Track [Page 2] RFC 5032 Search Within September 2007

5. Security Considerations

 The WITHIN extension does not raise any security considerations that
 are not present in the base protocol.  Considerations are the same as
 for IMAP [RFC3501].

6. IANA Considerations

 Per the IMAP RFC [RFC3501], 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.

7. References

7.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", RFC 2119, BCP 14, March 1997.
 [RFC3501]  Crispin, M., "Internet Message Access Protocol - Version
            4rev1", RFC 3501, March 2003.
 [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", RFC 4234, October 2005.

7.2. Informative References

 [CONTEXT]  Melnikov, D. and C. King, "Contexts for IMAP4", Work
            in Progress, May 2006.

Burger Standards Track [Page 3] RFC 5032 Search Within September 2007

Appendix A. Contributors

 Stephane 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.

Appendix B. Acknowledgements

 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.

Author's Address

 Eric W. Burger (editor)
 BEA Systems, Inc.
 USA
 EMail: eric.burger@bea.com
 URI:   http://www.standardstrack.com

Burger Standards Track [Page 4] RFC 5032 Search Within September 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

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 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
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 http://www.ietf.org/ipr.
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Burger Standards Track [Page 5]

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