Message Organization Working Group D. Karp
Internet-Draft Zimbra
Updates: 5256 (if approved) June 10, 2008
Intended status: Standards Track
Expires: December 12, 2008
Display-based Address Sorting for the IMAP4 SORT Extension
draft-karp-morg-sortdisplay-00
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Abstract
This document describes an IMAP protocol extension enabling server-
side message sorting based on the commonly-displayed portion of the
From header.
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Table of Contents
1. Conventions Used in This Document . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DISPLAYFROM Sort Key . . . . . . . . . . . . . . . . . . . 3
4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. Internationalization Considerations . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
8. Normative References . . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . . . 6
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1. Conventions Used in This Document
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 [RFC2119].
2. Introduction
The [SORT] extension to the [IMAP] protocol provides a means for
server-based sorting of messages. It defines a set of sort criteria
and the mechanism for determining the sort value of a message for
each such ordering.
The [SORT] extension's FROM ordering sorts messages lexically on the
[IMAP] addr-part of the first address in the From header. This
document provides an alternate ordering, DISPLAYFROM, which sorts
messages lexically based on the From address's [RFC2822] display-
name, when present.
A server that supports the DISPLAYFROM sort criterion indicates this
by returning "SORT=DISPLAYFROM" in its CAPABILITY response.
3. The DISPLAYFROM Sort Key
This document introduces a new [SORT] sort-key, DISPLAYFROM.
A message's sort value under the DISPLAYFROM ordering MUST be derived
from the first [RFC2822] mailbox in its From header as follows:
o If the From header is absent or if the header contains no
mailboxes, the message's sort value is the empty string.
o If the mailbox contains an [RFC2822] display-name, replace each
instance of [RFC2822] CFWS in the display-name with a single
space, trim all leading and trailing whitespace, and decode any
[RFC2047] encoded-words. If the resulting string is not the empty
string, use it as the sort value for the message.
o Otherwise, completely remove all [RFC2822] CFWS from the mailbox's
[RFC2822] addr-spec and use the resulting string as the message's
sort value.
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4. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [RFC2234]. [IMAP] defines the
non-terminal "capability" and [SORT] defines "sort-key".
capability =/ "SORT=DISPLAYFROM"
sort-key =/ "DISPLAYFROM"
5. Security Considerations
This document defines an additional IMAP4 capability. As such, it
does not change the underlying security considerations of [IMAP].
The author believes that no new security issues are introduced with
this additional IMAP4 capability.
6. Internationalization Considerations
DISPLAYFROM is a string-based sort criterion. As stated in [SORT],
the collations mandated by I18NLEVEL=1 or I18NLEVEL=2 from [RFC5255]
MUST be followed when sorting such strings.
The DISPLAYFROM ordering sorts on the full decoded [RFC2822] display-
name, when present. It does not attempt to parse this string in a
locale- or language-dependent manner in order to determine and sort
on some semantically meaningful substring such as the surname.
7. IANA Considerations
[IMAP] capabilities are registered by publishing a standards track or
IESG-approved experimental RFC. This document constitutes
registration of the SORT=DISPLAYFROM capability in the [IMAP]
capabilities registry.
8. Normative References
[IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC5255] Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet
Message Access Protocol Internationalization", RFC 5255,
June 2008.
[SORT] Crispin, M. and K. Murchison, "Internet Message Access
Protocol - SORT and THREAD Extensions", RFC 5256,
June 2008.
Author's Address
Dan Karp
Zimbra, a Yahoo! Company
701 First St.
Sunnyvale, CA 94089
USA
Email: dkarp@zimbra.com
URI: http://www.zimbra.com
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