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Versions: 00                                                            
Internet Draft                                               R. Gellens
Document: draft-gellens-imapext-regex-00                       QUALCOMM
Expires: September 2000                                      March 2000


               IMAP Regular Expressions SEARCH Extension


Status of this Memo:

    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
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    Internet-Drafts are draft documents valid for a maximum of six
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    The list of Internet-Draft Shadow Directories can be accessed at
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    A version of this draft document is intended for submission to the
    RFC editor as a Proposed Standard for the Internet Community.
    Discussion and suggestions for improvement are requested.


Copyright Notice

    Copyright (C) The Internet Society 2000.  All Rights Reserved.


















Gellens                 Expires September 2000                 [Page 1]Internet Draft   IMAP Regular Expressions SEARCH Extension   March 2000

Table of Contents

     1.  Abstract . . . . . . . . . . . . . . . . . . . . . . . . . .  2
     2.  Conventions Used in this Document . . . . . . . . . . . . . . 2
     3.  Comments . . . . . . . . . . . . . . . . . . . . . . . . . .  2
     4.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 2
     5.  REGEX Modifier to SEARCH (and UID SEARCH) Criteria . . . . .  3
     6.  Formal Syntax Changes . . . . . . . . . . . . . . . . . . . . 3
     7.  Regular Expression Details . . . . . . . . . . . . . . . . .  3
     8.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     9.  References . . . . . . . . . . . . . . . . . . . . . . . . .  4
    10.  Security Considerations . . . . . . . . . . . . . . . . . . . 5
    11.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  5
    12.  Author's Address  . . . . . . . . . . . . . . . . . . . . . . 5
    13.  Full Copyright Statement . . . . . . . . . . . . . . . . . .  5


1.  Abstract

    This memo describes a regular-expression search facility for the
    [IMAP] protocol.

    A server advertises support for this facility by the capability name
    REGEX.


2.  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 RFC 2119 [KEYWORDS].


3.  Comments

    Public comments can be sent to the IETF IMAP Extensions mailing
    list, <ietf-imapext@imc.org>.  To subscribe, send a message to
    <ietf-imapext-request@imc.org> with the word SUBSCRIBE as the body.
    Private comments should be sent to the author.


4.  Open Issues

    - Should the regular expression syntax be specified in a simple
    form, as is done here, or should it be a reference to a published,
    more complex form, such as POSIX 1003.2?

    - Should ^ and $ be used for token, line, or a message part (such as
    a header field)?





Gellens                 Expires September 2000                 [Page 2]Internet Draft   IMAP Regular Expressions SEARCH Extension   March 2000

    - Should REGEX come after the search key?

    - The current Formal Syntax allows for sillyness such as SEARCH
    REGEXP REGEXP CC "gork"


5.  REGEX Modifier to SEARCH (and UID SEARCH) Criteria

    This extension adds an additional optional REGEXP modifier to all
    SEARCH criteria which take strings.  When this modifier is present,
    the search criteria string is interpreted as a regular expression,
    as described in section 7.

    If the string supplied with the search criteria does not contain a
    valid regular expression, the server MUST return a BAD response.

    If the search criteria does not take a string, the server MUST
    return a BAD response.


6.  Formal Syntax Changes

    This section described the changes to the Formal Syntax of the IMAP
    protocol, using [ABNF]:

    search-key =/ REGEX SP search-key
                ; modifies existing IMAP search-key so
                ; that string values in search-key are treated
                ; as regular expressions for pattern matching


7.  Regular Expression Details

    The regular expression syntax described in this section is a subset
    of that used in many applications and systems.  It is however very
    simple and does not include the logical operators AND and OR.

    Searches using regular expressions are always substring matches
    except when the regular expression contains the characters '^' or
    '$'.

       Character                                Function
       ---------                                --------
        <any except those
        listed in this table>                   Matches itself
        .                                       Matches any character
        a*                                      Matches zero or more 'a's
        a+                                      Matches one or more 'a's
        [ab]                                    Matches 'a' or 'b'
        [a-c]                                   Matches 'a', 'b' or 'c'
        [^ab]                                   Matches any character
                                                    except 'a' or 'b'


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        ^                                       Matches beginning of
                                                    a token
        $                                       Matches end of a token
        \                                       Next character matches
                                                    itself

          Examples
          ---------

            String         Matches       Doesn't Match
            -------        -------       -------------
             hello          xhelloy          heello
             h.llo          hello            helio
             h.*o           hello            helloa
             h[a-f]llo      hello            hgllo
             ^he.*          hello            ehello
             .*lo$          hello            helloo
             hel+o          hello            helo


8.  Examples

    This example finds messages that have "MAKE*MONEY*FAST" in the
    subject, but not "MAKE!MONEY!FAST":

        C: Z SEARCH REGEX SUBJECT "MAKE[ _\-\*]+MONEY[ _\-\*]+FAST"
        S: * SEARCH 2 22 98 2048
        S: Z OK SEARCH Completed

    This example uses an invalid regular expression:

        C: Y SEARCH REGEX TO ".["
        S: Y BAD Invalid regular expression syntax

    This example uses REGEX with a search criteria that does not take a
    string:

        C: X SEARCH REGEX LARGER 10000
        S: X BAD Cannot use regular expressions with the LARGER criteria

    This example searches for messages without the \ANSWERED flag where
    the envelope from matches the regular expression "mump.*wump" and
    the text matches the substring "a[0-9]*" (note that the text
    criteria is not a regular expression):

        C: W SEARCH UNANSWERED REGEX FROM "mump.*wump" TEXT "a[0-9]*"
        S: * SEARCH 3
        S: W OK SEARCH Completed






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9.  References

    [ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
    ABNF", RFC 2234, Internet Mail Consortium, Demon Internet Ltd.,
    November 1997. <ftp://ftp.isi.edu/in-notes/rfc2234.txt>

    [IMAP4] Crispin, "Internet Message Access Protocol - Version 4rev1",
    RFC 2060, University of Washington, December 1996.

    [KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
    Requirement Levels", RFC 2119, Harvard University, March 1997.
    <ftp://ftp.isi.edu/in-notes/rfc2119.txt>


10.  Security Considerations

    This extension does not alter the security semantics of IMAP.


11.  Acknowledgments

    The table in section 7 is based on the one in RFC 1835.


12.  Author's Address

   Randall Gellens                    +1 858 651 5115
   QUALCOMM Incorporated              randy@qualcomm.com
   5775 Morehouse Drive
   San Diego, CA  92121-2779
   U.S.A.


13.  Full Copyright Statement

    Copyright (C) The Internet Society 2000.  All Rights Reserved.

    This document and translations of it may be copied and furnished to
    others, and derivative works that comment on or otherwise explain it
    or assist in its implementation may be prepared, copied, published
    and distributed, in whole or in part, without restriction of any
    kind, provided that the above copyright notice and this paragraph
    are included on all such copies and derivative works.  However, this
    document itself may not be modified in any way, such as by removing
    the copyright notice or references to the Internet Society or other
    Internet organizations, except as needed for the purpose of
    developing Internet standards in which case the procedures for
    copyrights defined in the Internet Standards process must be
    followed, or as required to translate it into languages other than
    English.




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    The limited permissions granted above are perpetual and will not be
    revoked by the Internet Society or its successors or assigns.

    This document and the information contained herein is provided on an
    "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
    TASK FORCE DISCLAIMS 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.













































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