Collected Extensions to IMAP4 ABNF
draft-melnikov-imap-ext-abnf-08

Versions: 00 01 02 03 04 05 06 07 08 rfc4466             Standards Track
Internet Draft                                             A. Melnikov
Document: draft-melnikov-imap-ext-abnf                      Isode Ltd.
Expires: July 2006                                         Cyrus Daboo
Updates: RFC 3501, RFC 2342, RFC 2088, RFC 3502 and RFC 3516
                                                          January 2006


                  Collected extensions to IMAP4 ABNF
                    draft-melnikov-imap-ext-abnf-08

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Abstract

   Over years many documents from IMAPEXT and LEMONADE working groups,
   as well as many individual documents have added syntactic
   extensions to many base IMAP commands described in RFC 3501. For
   ease of reference this document collects most of such ABNF changes
   in one place.

   This document also suggest a set of standard patterns for adding
   options and extensions to several existing IMAP commands defined in
   RFC 3501. The patterns provide for compatibility between existing
   and future extensions.

   This document updates ABNF in RFC 3501, RFC 2342, RFC 2088, RFC
   3502 and RFC 3516. It also includes part of the errata to RFC 3501.
   This document doesn't specify any semantic changes to the listed
   RFCs.


Table of Contents

  1. Introduction and Conventions Used                              3
     1.1 Purpose of this document                                   3
     1.2 Conventions Used in this document                          4
  2. IMAP ABNF extensions                                           4
     2.1 Optional parameters with the SELECT/EXAMINE commands       4
     2.2 Extended CREATE command                                    5
     2.3 Extended RENAME command                                    6
     2.4 Extensions to FETCH and UID FETCH Commands                 6
     2.5 Extensions to STORE and UID STORE Commands                 7
     2.6 Extensions to SEARCH Command                               8
     2.7 Extensions to APPEND Command                               9
  3. Formal Syntax                                                  9
  4. Security Considerations                                       14
  5. IANA Considerations                                           15
  6. References                                                    15
     6.1 Normative References                                      15
  7. Acknowledgments                                               16
  8. Authors' Addresses                                            16
  9. Full Copyright Statement                                      16
  10. Intellectual Property                                        17
  11. Appendix A. Editorial.                                       17
     11.1 Change Log                                               18


1.   Introduction and Conventions Used

1.1  Purpose of this document

   This document serves several purposes:
     1.   rationalize and generalize ABNF for some existing IMAP
          extensions;
     2.   collect the ABNF in one place in order to minimize cross
          references between documents;
     3.   define building blocks for future extensions so that they can
          be used together in a compatible way.

   It is expected that a future revision of this document gets
   incorporated into a revision of RFC 3501.

   This document updates ABNF in RFC 2342, 3501, RFC 2088, RFC 3502
   and RFC 3516. It also includes part of the errata to RFC 3501. This
   document doesn't specify any semantic changes to the listed RFCs.

   The ABNF in section 6 of RFC 2342 got rewritten to conform to the
   ABNF syntax as defined in RFC 4234 and to reference new non-
   terminals from RFC 3501. It was also restructured to allow for
   better readability. There were no changes "on the wire".

   Section 2 extends ABNF for SELECT, EXAMINE, CREATE, RENAME, FETCH
   /UID FETCH, STORE/UID STORE, SEARCH and APPEND commands in a
   consistent manner. Extensions to all the commands but APPEND have
   the same structure. Extensibility for the APPEND command was done
   slightly differently in order to preserve backward compatibility
   with existing extensions.
   Section 2 also defines a new ESEARCH response which purpose is to
   define a better version of the SEARCH response defined in RFC 3501.

   Section 3 defines the collected ABNF that replaces pieces of ABNF
   in the aforementioned RFCs. The collected ABNF got generalized to
   allow for easier future extensibility.


1.2  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", "SHOULD", "SHOULD NOT", and "MAY"
   in this document are to be interpreted as defined in "Key words for
   use in RFCs to Indicate Requirement Levels" [KEYWORDS].


2.   IMAP ABNF extensions

   This section is not normative. It provides some background on the
   intended use of different extensions and it gives some guidance
   about how future extensions should extend the described commands.


2.1  Optional parameters with the SELECT/EXAMINE commands

   This documents adds the ability to include one or more parameters
   with the IMAP SELECT (section 6.3.1 of [IMAP4]) or EXAMINE (section
   6.3.2 of [IMAP4]) commands, to turn on or off certain standard
   behaviours, or to add new optional behaviours required for a
   particular extension.

   There are two possible modes of operation:

   o  A global state change where a single use of the optional
      parameter will affect the session state from that time on,
      irrespective of subsequent SELECT/EXAMINE commands.

   o  A per-mailbox state change that will affect the session only for
      the duration of the new selected state.  A subsequent SELECT/
      EXAMINE without the optional parameter will cancel its effect
      for the newly selected mailbox.

   Optional parameters to the SELECT or EXAMINE commands are added as
   a parenthesised list of attribute/value pairs, and appear after the
   mailbox name in the standard SELECT or EXAMINE command.  The order
   of individual parameters is arbitrary. A parameter value is
   optional and may consist of atoms, strings or lists in a specific
   order.  If the parameter value is present, it always appears in
   parentheses (*).  Any parameter not defined by extensions that the
   server supports must be rejected with a BAD response.

      Example:

              C: a SELECT INBOX (ANNOTATE)
              S: ...
              S: a OK SELECT complete

      In the above example, a single parameter is used with the SELECT
      command.

      Example:

              C: a EXAMINE INBOX (ANNOTATE RESPONSES ("UID Responses")
                 CONDSTORE)
              S: ...
              S: a OK EXAMINE complete

      In the above example, three parameters are used with the EXAMINE
      command.  The second parameter consists of two items: an atom
      "RESPONSES" followed by a quoted string.

      Example:

              C: a SELECT INBOX (BLURDYBLOOP)
              S: a BAD Unknown parameter in SELECT command

      In the above example, a parameter not supported by the server is
      used. This results in the BAD response from the
      server.

   (*) - if a parameter has a mandatory value, which can always be
   represented as a number or a sequence-set, the parameter value does
   not need the enclosing (). See ABNF for more details.


2.2  Extended CREATE command

    Arguments:  mailbox name
                OPTIONAL list of CREATE parameters

    Responses:  no specific responses for this command

    Result:     OK - create completed
                NO - create failure: can not create mailbox with
                     that name
                BAD - argument(s) invalid

   This documents adds the ability to include one or more parameters
   with the IMAP CREATE command (see section 6.3.3 of [IMAP4]), to
   turn on or off certain standard behaviour, or to add new optional
   behaviours required for a particular extension.  No CREATE
   parameters are defined in this document.

   Optional parameters to the CREATE command are added as a
   parenthesised list of attribute/value pairs after the mailbox name.
   The order of individual parameters is arbitrary. A parameter value
   is optional and may consist of atoms, strings or lists in a
   specific order. If the parameter value is present, it always
   appears in parentheses (*). Any parameter not defined by extensions
   that the server supports must be rejected with a BAD response.

   (*) - if a parameter has a mandatory value, which can always be
   represented as a number or a sequence-set, the parameter value does
   not need the enclosing (). See ABNF for more details.


2.3  Extended RENAME command

    Arguments:  existing mailbox name
                new mailbox name
                OPTIONAL list of RENAME parameters

    Responses:  no specific responses for this command

    Result:     OK - rename completed
                NO - rename failure: can not rename mailbox with
                     that name, can not rename to mailbox with
                     that name, etc.
                BAD - argument(s) invalid

   This documents adds the ability to include one or more parameters
   with the IMAP RENAME command (see section 6.3.5 of [IMAP4]), to
   turn on or off certain standard behaviour, or to add new optional
   behaviours required for a particular extension. No RENAME
   parameters are defined in this document.

   Optional parameters to the RENAME command are added as a
   parenthesised list of attribute/value pairs after the new mailbox
   name. The order of individual parameters is arbitrary. A parameter
   value is optional and may consist of atoms, strings or lists in a
   specific order. If the parameter value is present, it always
   appears in parentheses (*). Any parameter not defined by extensions
   that the server supports must be rejected with a BAD response.

   (*) - if a parameter has a mandatory value, which can always be
   represented as a number or a sequence-set, the parameter value does
   not need the enclosing (). See ABNF for more details.


2.4  Extensions to FETCH and UID FETCH Commands

    Arguments:  sequence set
                message data item names or macro
                OPTIONAL fetch modifiers

    Responses:  untagged responses: FETCH

    Result:     OK - fetch completed
                NO - fetch error: can not fetch that data
                BAD - command unknown or arguments invalid

   This document extends the syntax of the FETCH and UID FETCH
   commands (see section 6.4.5 of [IMAP4]) to include optional FETCH
   modifiers.  No fetch modifiers are defined in this document.

   The order of individual modifiers is arbitrary. Each modified is
   an attribute/value pair. A modifier value is optional and may
   consist of atoms and/or strings and/or lists in a specific order.
   If the modifier value is present, it always appears in parentheses
   (*).  Any modifiers not defined by extensions that the server
   supports must be rejected with a BAD response.

   (*) - if a modifier has a mandatory value, which can always be
   represented as a number or a sequence-set, the modifier value does
   not need the enclosing (). See ABNF for more details.


2.5  Extensions to STORE and UID STORE Commands

   Arguments:  message set
               OPTIONAL store modifiers
               message data item name
               value for message data item

   Responses:  untagged responses: FETCH

   Result:     OK - store completed
               NO - store error: can not store that data
               BAD - command unknown or arguments invalid

   This document extends the syntax of the STORE and UID STORE
   commands (see section 6.4.6 of [IMAP4]) to include optional STORE
   modifiers.  No store modifiers are defined in this document.

   The order of individual modifiers is arbitrary. Each modified is
   an attribute/value pair. A modifier value is optional and may
   consist of atoms and/or strings and/or lists in a specific order.
   If the modifier value is present, it always appears in parentheses
   (*).  Any modifiers not defined by extensions that the server
   supports must be rejected with a BAD response.

   (*) - if a modifier has a mandatory value, which can always be
   represented as a number or a sequence-set, the modifier value does
   not need the enclosing (). See ABNF for more details.


2.6  Extensions to SEARCH Command


2.6.1      Extended SEARCH command

   Arguments:  OPTIONAL result specifier
               OPTIONAL [CHARSET] specification
               searching criteria (one or more)

   Responses:  REQUIRED untagged response: SEARCH (*)

   Result:     OK - search completed
               NO - search error: can not search that [CHARSET] or
                    criteria
               BAD - command unknown or arguments invalid


   This section updates definition of the SEARCH command described in
   section 6.4.4 of [IMAP4].

   The SEARCH command is extended to allow for result options. This
   document does not define any result options.

   The order of individual options is arbitrary.  Individual options
   may contain parameters enclosed in parentheses (**). If an option
   has parameters, they consist of atoms and/or strings and/or lists
   in a specific order. Any options not defined by extensions that the
   server supports must be rejected with a BAD response.

   (*) - An extension to the SEARCH command may require another
   untagged response, or no untagged response to be returned. Section
   2.6.2 defines a new ESEARCH untagged response, that replaces the
   SEARCH untagged response. Note that for a given extended SEARCH
   command the SEARCH and ESEARCH responses SHOULD be mutually
   exclusive, i.e. only one of them should be returned.

   (**) - if an option has a mandatory parameter, which can always be
   represented as a number or a sequence-set, the option parameter
   does not need the enclosing (). See ABNF for more details.


2.6.2      ESEARCH untagged response

   Contents:   one or more search-return-data pairs

   The ESEARCH response SHOULD be sent as a result of an extended
   SEARCH or UID SEARCH command specified in section 2.6.1.

   The ESEARCH response starts with an optional search correlator. If
   it is missing then the response was not caused by a particular IMAP
   command, whereas if it is present it contains the tag of the
   command that caused the response to be returned.

   The search correlator is followed by an optional UID indicator. If
   this indicator is present, all data in the ESEARCH response refers
   to UIDs, otherwise all returned data refers to message numbers.

   The rest of the ESEARCH response contains one or more search data
   pairs. Each pair starts with unique return item name, followed by a
   space and the corresponding data. Search data pairs may be returned
   in any order. Unless specified otherwise by an extension, any
   return item name SHOULD appear only once in an ESEARCH response.

   Example:    S: * ESEARCH UID COUNT 5 ALL 4:19,21,28

   Example:    S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28

   Example:    S: * ESEARCH COUNT 5 ALL 1:17,21


2.7  Extensions to APPEND Command

   The IMAP BINARY extension [BINARY] extends the APPEND command to
   allow a client to append data
   containing NULs by using the <literal8> syntax. The ABNF was
   rewritten to allow for easier extensibility by IMAP extensions.
   This document hasn't specified any semantical changes to the
   [BINARY] extension.

   In addition, the non-terminal "literal8" defined in [BINARY] got
   extended to allow for non-syncronizing literals if both [BINARY]
   and [LITERAL+] extensions are supported by the server.

   The IMAP MULTIAPPEND extension [MULTIAPPEND] extends the APPEND
   command to allow a client to append multiple messages atomically.
   This document defines a common syntax for the APPEND command that
   takes into considerations syntactic extensions defined by both
   [BINARY] and [MULTIAPPEND] extensions.


3.   Formal Syntax

   The following syntax specification uses the Augmented Backus-Naur
   Form (ABNF) notation as specified in [ABNF].

   Non-terminals referenced but not defined below are as defined by
   [IMAP4].

   Except as noted otherwise, all alphabetic characters are case-
   insensitive.  The use of upper or lower case characters to define
   token strings is for editorial clarity only.  Implementations MUST
   accept these strings in a case-insensitive fashion.


     append          = "APPEND" SP mailbox 1*append-message
                       ;; only a single append-message may appear
                       ;; if MULTIAPPEND [MULTIAPPEND] capability
                       ;; is not present

     append-message  = append-opts SP append-data

     append-ext      = append-ext-name SP append-ext-value
                       ;; This non-terminal define extensions to
                       ;; to message metadata.

     append-ext-name = tagged-ext-label

     append-ext-value= tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.


     append-data     = literal / literal8 / append-data-ext

     append-data-ext = tagged-ext
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions,
                       ;; i.e. a mandatory label followed
                       ;; by parameters.

     append-opts     = [SP flag-list] [SP date-time] *(SP append-ext)
                       ;; message metadata

     charset         = atom / quoted
                       ;; Exact syntax is defined in [CHARSET].

     create          = "CREATE" SP mailbox
                       [create-params]
                       ;; Use of INBOX gives a NO error.

     create-params   = SP "(" create-param *( SP create-param) ")"

     create-param-name = tagged-ext-label

     create-param      = create-param-name [SP create-param-value]

     create-param-value= tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.


     esearch-response  = "ESEARCH" [search-correlator] [SP "UID"]
                          *(SP search-return-data)
                        ;; Note that SEARCH and ESEARCH responses
                        ;; SHOULD be mutually exclusive,
                        ;; i.e. only one of the response types
                        ;; should be
                        ;; returned as a result of a command.


     examine         = "EXAMINE" SP mailbox [select-params]
                       ;; modifies the original IMAP EXAMINE command
                       ;; to accept optional parameters

     fetch           = "FETCH" SP sequence-set SP ("ALL" / "FULL" /
                       "FAST" / fetch-att /
                       "(" fetch-att *(SP fetch-att) ")")
                       [fetch-modifiers]
                       ;; modifies the original IMAP4 FETCH command to
                       ;; accept optional modifiers

     fetch-modifiers = SP "(" fetch-modifier *(SP fetch-modifier) ")"

     fetch-modifier  = fetch-modifier-name [ SP fetch-modif-params ]

     fetch-modif-params  = tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.

     fetch-modifier-name = tagged-ext-label

     literal8        = "~{" number ["+"] "}" CRLF *OCTET
                        ;; A string that might contain NULs.
                        ;; <number> represents the number of OCTETs
                        ;; in the response string.
                        ;; The "+" is only allowed when both LITERAL+
                        ;; and BINARY extensions are supported
                        ;; by the server.


     mailbox-data      =/ Namespace-Response /
                          esearch-response

     Namespace         = nil / "(" 1*Namespace-Descr ")"

     Namespace-Command = "NAMESPACE"

     Namespace-Descr   = "(" string SP
                            (DQUOTE QUOTED-CHAR DQUOTE / nil)
                             *(Namespace-Response-Extension) ")"

     Namespace-Response-Extension = SP string SP
                       "(" string *(SP string) ")"

     Namespace-Response = "NAMESPACE" SP Namespace
                          SP Namespace SP Namespace
           ;; This response is currently only allowed
           ;; if the IMAP server supports [RFC 2342].
           ;; The first Namespace is the Personal Namespace(s)
           ;; The second Namespace is the Other Users' Namespace(s)
           ;; The third Namespace is the Shared Namespace(s)

     rename          = "RENAME" SP mailbox SP mailbox
                       [rename-params]
                       ;; Use of INBOX as a destination gives
                       ;; a NO error, unless rename-params
                       ;; is not empty.

     rename-params     = SP "(" rename-param *( SP rename-param) ")"

     rename-param      = rename-param-name [SP rename-param-value]

     rename-param-name = tagged-ext-label

     rename-param-value= tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.


     response-data   = "*" SP response-payload CRLF

     response-payload= resp-cond-state / resp-cond-bye /
                       mailbox-data / message-data / capability-data

     search          = "SEARCH" [search-return-opts]
                       search-program


     search-correlator  = SP "(" "TAG" SP tag-string ")"

     search-program     = [SP "CHARSET" SP charset] 1*(SP search-key)
                          ;; CHARSET argument to SEARCH MUST be
                          ;; registered with IANA.

     search-return-data = search-modifier-name SP search-return-value
                          ;; Note that not every SEARCH return option
                          ;; is required to have the corresponding
                          ;; ESEARCH return data.

     search-return-opts = SP "RETURN" SP "(" [search-return-opt
                          *(SP search-return-opt)] ")"

     search-return-opt = search-modifier-name [SP search-mod-params]

     search-return-value = tagged-ext-val
                          ;; Data for the returned search option.
                          ;; A single "nz-number"/"number" value
                          ;; can be returned as an atom (i.e. without
                          ;; quoting). A sequence-set can be returned
                          ;; as an atom as well.

     search-modifier-name = tagged-ext-label

     search-mod-params = tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.


     select          = "SELECT" SP mailbox [select-params]
                       ;; modifies the original IMAP SELECT command to
                       ;; accept optional parameters

     select-params   = SP "(" select-param *(SP select-param) ")"

     select-param    = select-param-name [SP select-param-value]
                       ;; a parameter to SELECT may contain one or
                       ;; more atoms and/or strings and/or lists.

     select-param-name= tagged-ext-label

     select-param-value= tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.


     status-att-list = status-att-val *(SP status-att-val)
                       ;; Redefines status-att-list from RFC 3501.
                       ;; status-att-val is defined in RFC 3501 errata

     status-att-val  = ("MESSAGES" SP number) /
                       ("RECENT" SP number) /
                       ("UIDNEXT" SP nz-number) /
                       ("UIDVALIDITY" SP nz-number) /
                       ("UNSEEN" SP number)
                       ;; Extensions to the STATUS responses
                       ;; should extend this production.
                       ;; Extensions should use the generic
                       ;; syntax defined by tagged-ext.

     store           = "STORE" SP sequence-set [store-modifiers]
                       SP store-att-flags
                       ;; extend [IMAP4] STORE command syntax
                       ;; to allow for optional store-modifiers

     store-modifiers =  SP "(" store-modifier *(SP store-modifier)
                         ")"

     store-modifier  = store-modifier-name [SP store-modif-params]

     store-modif-params = tagged-ext-val
                       ;; This non-terminal shows recommended syntax
                       ;; for future extensions.

     store-modifier-name = tagged-ext-label

     tag-string         = string
                          ;; tag of the command that caused
                          ;; the ESEARCH response, sent as
                          ;; a string.

     tagged-ext          = tagged-ext-label SP tagged-ext-val
                            ;; recommended overarching syntax for
                            ;; extensions

     tagged-ext-label    = tagged-label-fchar *tagged-label-char
                           ;; Is a valid RFC 3501 "atom".

     tagged-label-fchar  = ALPHA / "-" / "_" / "."

     tagged-label-char   = tagged-label-fchar / DIGIT / ":"

     tagged-ext-comp     = astring /
                           tagged-ext-comp *(SP tagged-ext-comp) /
                           "(" tagged-ext-comp ")"
                            ;; Extensions that follow this general
                            ;; syntax should use nstring instead of
                            ;; astring when appropriate in the context
                            ;; of the extension.
                            ;; Note that a message set or a "number"
                            ;; can always be represented as an "atom".
                            ;; An URL should be represented as
                            ;; a "quoted" string.

     tagged-ext-simple   = sequence-set / number

     tagged-ext-val      = tagged-ext-simple /
                           "(" [tagged-ext-comp] ")"


4.   Security Considerations

   This document updates ABNF in RFC 3501, RFC 2342, RFC 2088, RFC
   3502 and RFC 3516. The updated documents must be consulted for
   security considerations for the extensions that they define.

   As a protocol gets more complex, parser bugs become more common
   including buffer overflow, denial of service and other common
   security coding errors. To the extent this document makes the
   parser more complex, it makes this situation worse. To this extent
   this document makes the parser more consistent and thus simpler,
   the situation is improved. The impact will depend on how many
   deployed IMAP extensions are consistent with this document.
   Implementers are encouraged to take care of these issues when
   extending existing implementations.  Future IMAP extensions should
   strive for consistency and simplicity to the greatest extent
   possible.

   Extensions to IMAP commands that are permitted in NOT AUTHENTICATED
   state are more sensitive to these security issues due to the larger
   possible attacker community prior to authentication, and the fact
   that some IMAP servers run with elevated privileges in that state.
   This document does not extend any commands permitted in NOT
   AUTHENTICATED state. Future IMAP extensions to commands permitted
   in NOT AUTHENTICATED state should favor simplicity over consistency
   or extensibility.


5.   IANA Considerations

   This document doesn't define any new IMAP extension, so no action
   from IANA is required.


6.   References

6.1  Normative References

   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", RFC 2119, March 1997.

   [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
   4rev1", RFC 3501, University of Washington, March 2003.

   [ABNF] Crocker, D. (Ed.) and P. Overell , "Augmented BNF for Syntax
   Specifications: ABNF", RFC 4234, October 2005.

   [CHARSET] Freed, N. and J. Postel, "IANA Character Set Registration
   Procedures", RFC 2978, October 2000.

   [MULTIAPPEND]  Crispin, M., "Internet Message Access Protocol
   (IMAP) - MULTIAPPEND Extension", RFC 3502, March 2003.

   [NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
   May 1998.

   [LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
   January 1997.

   [BINARY] Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516,
   April 2003


7.   Acknowledgments

   This documents is based on ideas proposed by Pete Resnick, Mark
   Crispin, Ken Murchison, Philip Guenther, Randall Gellens and Lyndon
   Nerenberg.

   However all errors and omissions must be attributed to the authors
   of the document.

   Thanks to Philip Guenther, Dave Cridland, Mark Crispin, Chris
   Newman, Elwyn Davies and Barry Leiba for comments and corrections.

   literal8 syntax was taken from RFC 3516.


8.   Authors' Addresses

   Alexey Melnikov
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex, TW12 2BX
   UK

   Email: Alexey.Melnikov@isode.com

   Cyrus Daboo

   EMail: cyrus@daboo.name


9.   Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   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 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.


10.  Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed
   to pertain to the implementation or use of the technology described
   in this document or the extent to which any license under such
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11.  Appendix A. Editorial.

11.1 Change Log

   00   Initial Revision.
   01   Added Cyrus as co-author. Added BINARY literals. Added section
        about APPEND. Clarified that the order of all
        parameters/modifiers is arbitrary. Unrecognized SELECT/EXAMINE
        parameter should cause the BAD, not the NO response.
   02   Updated boilerplate. Extended SEARCH modifiers to be consistent
        with STORE modifiers. Rewrote FETCH modifier syntax for
        consistency.
   03   Updated as per comments from Philip (ABNF suggestions, in
        particular addition of response-data; normative language).
        Incorporated RFC 3501 ABNF errata from Mark. Added extensions to
        CREATE and RENAME commands. Updated ABNF to use consistent
        grammer for all extension elements (this changed ABNF for
        SELECT/EXAMINE and FETCH).
   04   Added ESEARCH response. Added search-program from IMAP URL.
        Removed the partition parameter from CREATE/RENAME. Added
        NAMESPACE command/response.
   05   Added non-synchronizing literals (RFC 2088). Clarified generic
        syntax for STATUS responses.
   06   Updated reference to ABNF. Made CREATE/RENAME/SELECT parameter
        values optional (for consistency with other parameters and to
        make examples valid), but if a value is present, it must be in
        (), unless it is a number or a sequence. Updated description of
        CREATE/RENAME/SELECT parameters to match ABNF. Disallow a single
        astring parameter with not parentheses. Defined append-ext to be
        "atom SP value". Added a missing reference to RFC 3516. Added
        missing leading space in the search-return-opts non-terminal.
        Rewrote ABNF for STORE and FETCH options for consistency with
        others. Added Security Considerations, courtesy of Chris Newman.
        Added new non-terminal for charset (from Mark Crispin's RFC 3501
        errata). Describe exact syntax for future extensions (as per
        IETF LC comment from Mark Crispin).