One document matched: draft-ietf-imapext-condstore-00.txt
Internet Draft: IMAP Extension for Conditional STORE A. Melnikov
Document: draft-ietf-imapext-condstore-00.txt S. Hole
Expires: September 2003 ACI WorldWide/MessagingDirect
March 2003
IMAP Extension for Conditional STORE operation
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 other groups may also
distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
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at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
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Copyright Notice
Copyright (C) The Internet Society 2001-2003. All Rights Reserved.
0.1. Open issues
1). Should conditional STORE be atomic accross message set (i.e. either
all messages in message set weren't changed since and conditional
STORE succeeds or operation fails for all messages)?
This can be difficult to implement for some servers.
Is a server allowed to reply NO to a conditional STORE operation that
contains more than one message? Do we need a special response code
for this (probably yes).
0.2. Change History
Changes from draft-melnikov-imap-condstore-09:
1. Some text clarifications based on suggestions by Harrie Hazewinkel
2. Added paragraph about mailbox locking and DOS when conditional STORE
operation is performed on a large mailbox.
3. Fixed syntax of <entry-name> to match the ANNOTATE extention.
4. Added sentence that a system flag MUST always be considered existent,
when UNCHANGEDSINCE 0 is used. Is this a good idea?
5. Clarified client behavior upon receipt of MODIFIED response code.
6. Updated ABNF to clarify where 0 is allowed as mod-sequence and where
it is not.
7. Got rid of MODSEQ response code and return this data in the untagged
SEARCH/SORT responses.
8. Updated RFC number for the IMAP4rev1 document.
Changes from -08 to -09:
1. Added an extended example about reporting regular (non-conditional) flag
changes to other sessions.
2. Simplified FETCH MODSEQ syntax by removing per-metadata requests and
responses.
Changes from -07 to -08:
1. Added note saying the change to UIDVALIDITY also invalidates HIGHESTMODSEQ.
2. Fixed several bugs in ABNF for STATUS and STORE commands.
Changes from -06 to -07:
1. Added clarification that when a server does command reordering, the second
completed operation gets the higher mod sequence.
2. Renamed annotation type specifier "both" to "all" as per suggestion
from Minneapolis meeting.
3. Removed PERFLAGMODSEQ capability, as it doesn't buy anything: a client
has to work with both types of servers (i.e. servers that support per
message per flag modseqs and servers that support only per message
modseqs) anyway.
4. Per flag mod-sequences are optional for a server to return. Updated syntax.
5. Allow MODSEQ response code only as a result of SEARCH/SORT as suggested
by John Myers. MODSEQ response code is not allowed after FETCH or STORE.
Changes from -05 to -06:
1. Replaced "/message/flags/system" with "/message/flags" to
match ANNOTATE draft.
2. Extended FETCH/SEARCH/SORT syntax to allow for specifying
whether an operation should be performed on a shared or a private
annotation (or both).
3. Corrected some examples.
Changes from -04 to -05:
1. Added support for SORT extension.
2. Multiple language/spelling fixes by Randall Gellens.
Changes from -03 to -04:
1. Added text saying that MODSEQ fetch data items cause server
to include MODSEQ data response in all subsuquent unsolicited FETCH
responses.
2. Added "authors address" section.
Changes from -02 to -03:
1. Changed MODTIME untagged response to MODTIME response code.
2. Added MODTIME response code to the tagged OK response for SEARCH.
Updated examples accordingly.
3. Changed rule for sending untagged FETCH response as a result of
STORE when .SILENT prefix is used. If .SILENT prefix is used,
server doesn't have to send untagged FETCH response, because
MODTIME response code already contains modtime.
4. Renamed MODTIME to MODSEQ to make sure there is no confusion
between mod-sequence and ACAP modtime.
5. Minor ABNF changes.
6. Minor language corrections.
Changes from -01 to -02:
1. Added MODTIME data item to STATUS command.
2. Added OK untagged response to SELECT/EXAMINE.
3. Clarified that MODIFIED response code contains list of UIDs for
conditional UID STORE and message set for STORE.
4. Added per-message modtime.
5. Added PERFLAGMODTIME capability.
6. Fixed several bugs in examples.
7. Added more comments to ABNF.
Changes from -00 to -01:
1. Refreshed the list of Open Issues.
2. Changed "attr-name" to "entry-name", because modtime applies to
entry, not attribute.
3. Added MODTIME untagged response.
4. Cleaned up ABNF.
5. Added "Acknowledgments" section.
6. Fixed some spelling mistakes.
Table of Contents
1 Abstract .................................................. X
2 Conventions Used in This Document ......................... X
3 Introduction and Overview ................................. X
4 IMAP Protocol Changes ..................................... X
4.1 New OK untagged responses for SELECT and EXAMINE ......... X
4.1.1 HIGHESTMODSEQ response code ............................ X
4.2 STORE and UID STORE Commands ............................. X
4.3 MODSEQ message data item in FETCH Command ................ X
4.4 MODSEQ search criterion in SEARCH ........................ X
4.5 MODSEQ Sort Criterion .................................... X
4.6 Modified SEARCH and SORT untagged responses .............. X
4.7 HIGHESTMODSEQ status data items .......................... X
5 Formal Syntax ............................................. X
6 Security Considerations ................................... X
7 References ................................................ X
7.1 Normative References ..................................... X
7.2 Informative References ................................... X
8 Acknowledgments ........................................... X
9 Author's Addresses ........................................ X
10 Full Copyright Statement ................................. X
1. Abstract
Often, multiple IMAP clients need to coordinate changes to a common
IMAP mailbox. Examples include different clients for the same user,
and multiple users accessing shared mailboxes. These clients
need a mechanism to synchronize state changes for messages within the
mailbox. They must be able to guarantee that only one client can change
message state (e.g., message flags or annotations) at any time. An
example of such an application is use of an IMAP mailbox as a message
queue with multiple dequeueing clients.
The Conditional Store facility provides a protected update mechanism for
message state information that can detect and resolve conflicts between
multiple writing mail clients.
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].
In examples, lines beginning with "S:" are sent by the IMAP server, and
lines beginning with "C:" are sent by the client. Line breaks may appear
in example commands solely for editorial clarity; when present in
the actual message they are represented by "CRLF".
Formal syntax is defined using ABNF [ABNF] as modified by [IMAP4].
The term "metadata" or "metadata item" is used throughout this document.
It refers to any system or user defined keyword or an annotation
[ANNOTATE].
Some IMAP mailboxes are private, accessible only to the owning user.
Other mailboxes are not, either because the owner has set an ACL
[ACL] which permits access by other users, or because it is a
shared mailbox. Let's call a metadata item "shared" for the mailbox
if any changes to the metadata items are persistent and visible to all
other users accessing the mailbox. Otherwise the metadata item is called
"private". Note, that private metadata items are still visible to all
sessions accessing the mailbox as the same user. Also note, that different
mailboxes may have different metadata items as shared.
3. Introduction and Overview
The Conditional STORE extension is present in any IMAP4 implementation
which returns "CONDSTORE" as one of the supported capabilities in the
CAPABILITY command response.
Every IMAP message has an associated positive unsigned 64-bit value called a
modification sequence (mod-sequence). This is an opaque value updated by
the server whenever a metadata item is modified. The value is intended to
be used only for comparisons within a server. However, the server MUST
guarantee that each STORE command performed on the same mailbox, including
simultaneous stores to different metadata items from different connections,
will get a different mod-sequence value. Also, for any two successful
STORE operations performed in the same session on the same mailbox,
the mod-sequence of the second completed operation MUST be greater than
the mod-sequence of the first completed. Note that the latter rule disallows
the use of the system clock as a mod-sequence, because if system time changes
(e.g., a NTP [NTP] client adjusting the time), the next generated value might
be less than the previous one.
Mod-sequences allow a client that supports the CONDSTORE extension to
determine if a message metadata has changed since some known
moment. Whenever the state of a flag changes (i.e., the flag is added and
before it wasn't set, or the flag is removed and before it was set) the
value of the modification sequence for the message MUST be updated.
Adding the flag when it is already present or removing when it is not
present SHOULD NOT change the mod-sequence.
When a message is appended to a mailbox (via the IMAP APPEND command,
COPY to the mailbox or using an external mechanism) the server
generates a new modification sequence that is higher than the highest
modification sequence of all messages in the mailbox and assigns it to
the appended message.
When an annotation is added, modified or removed the corresponding message
mod-sequence MUST be updated.
The server MAY store separate (per message) modification sequence values for
different metadata items. If the server does so, per message mod-sequence is
the highest mod-sequence of all metadata items for the specified message.
This extension makes the following changes to the IMAP4 protocol:
a) extends the syntax of the STORE command to allow STORE
modifiers
b) adds the MODIFIED response code which should be used with
a NO response to the STORE command
c) adds a new MODSEQ message data item for use with the FETCH command
d) adds a new MODSEQ search criterion
e) extends syntax of untagged SEARCH and SORT responses to include
mod-sequence.
f) adds a new OK untagged responses for the SELECT and EXAMINE commands
g) adds the HIGHESTMODSEQ status data item to the STATUS command
h) adds a new MODSEQ sort criterion
The rest of this document describes the protocol changes more rigorously.
4. IMAP Protocol Changes
4.1. New OK untagged responses for SELECT and EXAMINE
4.1.1. HIGHESTMODSEQ response code
This document adds a new response code that is returned in the OK
untagged response for the SELECT and EXAMINE commands. A server
supporting the CONDSTORE extension MUST send the OK untagged
response including HIGHESTMODSEQ response code with every successful
SELECT or EXAMINE command:
OK [HIGHESTMODSEQ <mod-sequence-value>]
Where <mod-sequence-value> is the highest mod-sequence value of all
messages in the mailbox. When the server changes UIDVALIDITY for a
mailbox, it doesn't have to keep the same HIGHESTMODSEQ for the
mailbox.
A disconnected client can use the value of HIGHESTMODSEQ to check if
it has to refetch flags and/or annotations from the server. If the
UIDVALIDITY value has changed for the selected mailbox, the client
MUST delete the cached value of HIGHESTMODSEQ. If UIDVALIDITY for
the mailbox is the same and if the HIGHESTMODSEQ value stored in
the client's cache is less than the value returned by the server,
then some metadata items on the server have changed since the last
synchronization, and the client needs to update its cache. The client
MAY use SEARCH MODSEQ as described in section 4.4 to find out exactly
which metadata items have changed.
Example: C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: * OK [HIGHESTMODSEQ 20010715194045007]
S: A142 OK [READ-WRITE] SELECT completed
4.2. 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't 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 an optional STORE
modifier. The document defines the following modifier:
UNCHANGEDSINCE
If the mod-sequence of any metadata item specified in the STORE
operation for any message in the message set is greater than the
specified unchangedsince value, then the command fails.
On failure, a MODIFIED response code is returned which includes
the message set (for STORE) or set of UIDs (for UID STORE)
of all messages that failed the UNCHANGESINCE test.
Example:
C: a101 STORE 7,5,9 (UNCHANGEDSINCE 20000320162338)
+FLAGS.SILENT (\Deleted)
S: a101 NO [MODIFIED 7,9] Conditional STORE failed
In spite of the failure of the conditional STORE operation
for message 7, the server continues to process the conditional
STORE in order to find all messages which fail the test.
Use of UNCHANGEDSINCE with a modification sequence of 0
always fails if the metadata item exists. A system flag
MUST always be considered existent, whether it was set or not.
Example:
C: a102 STORE 12 (UNCHANGEDSINCE 0)
+FLAGS.SILENT ($MDNSent)
S: a102 NO [MODIFIED 12] Conditional STORE failed
Note: A client trying to atomically change the state of a particular
flag (or a set of flags) should be prepared to deal with the case
when the server returns MODIFIED response code if the state
of the flag being watched hasn't changed (but the state of some
other flag has). This is necessary, because some servers don't store
separate mod-sequences for different flags or annotations. However,
server implementations are discouraged from doing that, as it is
possible not to return spurious errors even when storing a single
mod-sequence per message.
Upon the receipt of MODIFIED response code the client SHOULD try to
figure out if the required flags have indeed changed. If they haven't
the client SHOULD retry the command.
Example:
C: a106 STORE 100:150 (UNCHANGEDSINCE 200212030000000)
+FLAGS.SILENT ($Processed)
S: a106 NO [MODIFIED 101] Conditional STORE failed
the flag $Processed was set on the message 101 ...
C: a107 NOOP
S: * 101 FETCH (MODSEQ (200303011130956) FLAGS ($Processed))
S: a107 OK
... so the client retries the operation for the rest of the messages
C: a108 STORE 100,102:150 (UNCHANGEDSINCE 200303011130956)
+FLAGS.SILENT ($Processed)
S: * 100 FETCH (MODSEQ (200303181230852))
S: * 102 FETCH (MODSEQ (200303181230852))
...
S: a108 OK Conditional Store completed
Or the flag hasn't changed ...
C: b107 NOOP
S: * 101 FETCH (MODSEQ (200303011130956) FLAGS (\Deleted \Answered))
S: b107 OK
... and the client retries the operation for all messages
C: b108 STORE 100:150 (UNCHANGEDSINCE 200212030000000)
+FLAGS.SILENT ($Processed)
S: * 100 FETCH (MODSEQ (200303181230852))
S: * 101 FETCH (MODSEQ (200303181230852))
S: * 102 FETCH (MODSEQ (200303181230852))
...
S: b108 OK Conditional Store completed
If the operation is successful the server MUST update the
mod-sequence attribute for every message that was changed.
Untagged FETCH responses MUST be sent (even if .SILENT is
specified) and each response MUST include MODSEQ message data
item if its mod-sequence has changed. This is required to
update clients cache with the correct mod-sequence values.
See section 4.3 for more details.
Example:
C: a103 UID STORE 6,4,8 (UNCHANGEDSINCE 200012121230045)
+FLAGS.SILENT (\Deleted)
S: * 1 FETCH (UID 4 MODSEQ (200012121231000))
S: * 2 FETCH (UID 6 MODSEQ (200012101230852))
S: * 4 FETCH (UID 8 MODSEQ (200012121130956))
S: a103 OK Conditional Store completed
Example:
C: a104 STORE * (UNCHANGEDSINCE 200012121230045) +FLAGS.SILENT
(\Deleted $Processed)
S: * 50 FETCH (MODSEQ (200012111230045))
S: a104 OK Store (conditional) completed
Note: If a message is specified multiple times in the message
set, and the server doesn't internally eliminate duplicates from
the message set, it MUST NOT fail the conditional STORE
operation for the second (or subsequent) occurrence of the message
if the operation completed successfully for the first occurrence.
For example, if the client specifies:
a105 STORE 7,3:9 (UNCHANGEDSINCE 200012121230045)
+FLAGS.SILENT (\Deleted)
the server must not fail the operation for message 7 as part of
processing "3:9" if it succeeded when message 7 was processed
the first time.
4.3. MODSEQ message data item in FETCH Command
This extension adds a MODSEQ message data item to the FETCH command.
The MODSEQ message data item allows clients to retrieve mod-sequence
values for a range of messages in the currently selected mailbox.
Once the client specified the MODSEQ message data item in a FETCH request,
the server MUST include the MODSEQ fetch response data items in all
subsequent unsolicited FETCH responses.
Syntax: MODSEQ
The MODSEQ message data item causes the server to return MODSEQ fetch
response data items.
Syntax: MODSEQ ( <permsg-modsequence> )
MODSEQ response data items contain per-message mod-sequences.
The MODSEQ response data item is returned if the client issued FETCH with
MODSEQ message data item. It also allows the server to notify the client
about mod-sequence changes caused by conditional STOREs (section 4.2) and/or
changes caused by external sources.
Example:
C: a FETCH 1:3 (MODSEQ)
S: * 1 FETCH (MODSEQ (20000624140003))
S: * 2 FETCH (MODSEQ (20000624140007))
S: * 3 FETCH (MODSEQ (20000624140005))
S: a OK Fetch complete
In this example the client requests per message mod-sequences for a
set of messages.
When a flag for a message is modified in a different session, the server
sends an unsolicited FETCH response containing the mod-sequence for the
message.
Example:
(Session 1, authenticated as a user "alex"). The user adds a shared
flag \Deleted:
C: A142 SELECT INBOX
...
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Answered \Deleted \Seen \*)] Limited
...
C: A160 STORE 7 +FLAGS.SILENT (\Deleted)
S: * 7 FETCH (MODSEQ (200012121231000))
S: A160 OK Store completed
(Session 2, also authenticated as the user "alex"). Any changes to flags
are always reported to all sessions authenticated as the same user as in
the session 1.
C: C180 NOOP
S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (200012121231000))
S: C180 OK Noop completed
(Session 3, authenticated as a user "andrew"). As \Deleted is a shared
flag, changes in the session 1 are also reported in the session 3:
C: D210 NOOP
S: * 7 FETCH (FLAGS (\Deleted \Answered) MODSEQ (200012121231000))
S: D210 OK Noop completed
The user modifies a private flag \Seen in the session 1 ...
C: A240 STORE 7 +FLAGS.SILENT (\Seen)
S: * 7 FETCH (MODSEQ (200012121231777))
S: A240 OK Store completed
... which is only reported in the session 2 ...
C: C270 NOOP
S: * 7 FETCH (FLAGS (\Deleted \Answered \Seen) MODSEQ (200012121231777))
S: C270 OK Noop completed
... but not in the session 3.
C: D300 NOOP
S: D300 OK Noop completed
And finally the user removes flags \Answered (shared) and \Seen (private)
in the session 1.
C: A330 STORE 7 -FLAGS.SILENT (\Answered \Seen)
S: * 7 FETCH (MODSEQ (200012121245160))
S: A330 OK Store completed
Both changes are reported in the session 2 ...
C: C360 NOOP
S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (200012121245160))
S: C360 OK Noop completed
... and only changes to shared flags are reported in session 3.
C: D390 NOOP
S: * 7 FETCH (FLAGS (\Deleted) MODSEQ (200012121245160))
S: D390 OK Noop completed
4.4. MODSEQ search criterion in SEARCH
The MODSEQ criterion for the SEARCH command allows a client to search
for the metadata items that were modified since a specified moment.
Syntax: MODSEQ [<entry-name> <entry-type-req>] <mod-sequence-valzer>
Messages that have modification values which are equal to or
greater than <mod-sequence-valzer>. This allows a client,
for example, to find out which messages contain metadata items
that have changed since the last time it updated its disconnected
cache. The client may also specify <entry-name> (name of metadata
item) and <entry-type-req> (type of metadata item) before
<mod-sequence-valzer>. <entry-type-req> can be one of "shared",
"private" or "all". The latter means that the server should use
the biggest value among "private" and "shared" modseqs for the
metadata item. If the server doesn't store internally separate
mod-sequences for different flags and annotations, it MUST ignore
<entry-name> and <entry-type-req>. Otherwise the server should
use them to narrow down the search.
For a flag <flagname> the corresponding <entry-name> has a form
"/message/flags/<flagname>" as defined in [ANNOTATE]. Note, that
the leading "\" character that denotes a system flag has to be
escaped as per Section 4.3 of [IMAP4], as the <entry-name> uses
syntax for quoted strings.
If client specifies a MODSEQ criterion in a SEARCH command and
the server returns a non-empty SEARCH result, the server MUST also
return a MODSEQ response code in the tagged OK response. The MODSEQ
response code covers all messages returned in the untagged SEARCH results.
See also section 4.6.
Example:
C: a SEARCH MODSEQ "/message/flags/draft" all 20010320162338
ANNOTATION "/message/comment" "value" "IMAP4"
S: * SEARCH 2 5 6 7 11 12 18 19 20 23 (MODSEQ 20010917162500)
S: a OK Search complete
In the above example, the message numbers of any messages
containing the string "IMAP4" in the "value" attribute of the
"/message/comment" entry and having a mod-sequence equal to or
greater than 20010320162338 for the "\Draft" flag are returned in
the search results.
Example:
C: a SEARCH OR NOT MODSEQ 20010320162338 LARGER 50000
S: * SEARCH
S: a OK Search complete, nothing found
4.5. MODSEQ Sort Criterion
If a server implementing CONDSTORE also implements the SORT
extension as defined by [SORT], it MUST also support sorting on
per-message mod-sequence.
Syntax: MODSEQ
If client specifies a MODSEQ search (as per section 4.4) or sort
criterion in the SORT command and the server returns a non-empty
SORT result, the server MUST also return a MODSEQ response
code in the tagged OK response which covers all messages returned
in untagged SORT responses. See also section 4.6.
Example:
C: A282 SORT (SUBJECT MODSEQ) UTF-8 SINCE 1-Feb-2001
S: * SORT 2 81 83 84 82 882 (MODSEQ 117)
S: A282 OK SORT completed
Example:
C: A283 SORT (SUBJECT REVERSE DATE) UTF-8 MODSEQ 21
S: * SORT 6 3 4 5 2 (MODSEQ 125)
S: A283 OK SORT completed
Example:
C: A284 SORT (MODSEQ) KOI8-R OR NOT MODSEQ 20010320162338
SUBJECT "Privet"
S: * SORT
S: A284 OK Sort complete, nothing found
4.6. Modified SEARCH and SORT untagged responses
Data: zero or more numbers
mod-sequence value (omitted if no match)
This document extends syntax of the untagged SEARCH and SORT responses
to include mod-sequence for all messages being returned.
If a client specifies a MODSEQ criterion in a SEARCH (or UID SEARCH)
command and the server returns a non-empty SEARCH result, the server
MUST also append (to the end of the untagged SEARCH response) the
highest mod-sequence for all messages being returned.
If client specifies a MODSEQ search or sort criterion in a SORT
(or UID SORT) command and the server returns a non-empty SORT result,
the server MUST also append (to the end of the untagged SORT response)
the highest mod-sequence for all messages being returned.
4.7. HIGHESTMODSEQ status data items
This document defines a new status data item:
HIGHESTMODSEQ
The highest mod-sequence value all messages
in the mailbox. This is the same value that is returned by the server
in the HIGHESTMODSEQ response code in OK untagged response
(see section 4.1.1).
Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES HIGHESTMODSEQ)
S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292
HIGHESTMODSEQ 200201011231777)
S: A042 OK STATUS completed
5. 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.
capability =/ "CONDSTORE"
status = "STATUS" SP mailbox SP
"(" status-att-req *(SP status-att-req) ")"
;; redefine STATUS command syntax defined in [IMAP4]
status-att-req = status-att / "HIGHESTMODSEQ"
mailbox-data =/ "STATUS" SP mailbox SP "("
[status-rsp-info *(SP status-rsp-info)] ")"
status-rsp-info = status-att SP number /
"HIGHESTMODSEQ" SP mod-sequence-value
store = "STORE" SP set store-modifiers SP store-att-flags
store-modifiers = [ SP "(" store-modifier *(SP store-modifier) ")" ]
store-modifier = "UNCHANGEDSINCE" SP mod-sequence-valzer
;; Only single "UNCHANGEDSINCE" may be specified
;; in a STORE operation
fetch-att =/ fetch-mod-sequence
;; modifies original IMAP4 fetch-att
fetch-mod-sequence = "MODSEQ"
fetch-mod-resp = "MODSEQ" SP "(" permsg-modsequence ")"
search-key =/ search-modsequence
;; modifies original IMAP4 search-key
search-modsequence = "MODSEQ" [search-modseq-ext] SP mod-sequence-valzer
search-modseq-ext = SP entry-name SP entry-type-req
resp-text-code =/ "HIGHESTMODSEQ" SP mod-sequence-value /
"MODIFIED" SP set
entry-name = '"' "/message/flags/" attr-flag '"'
;; each system or user defined flag <flag>
;; is mapped to "/message/flags/<flag>".
;;
;; <entry-name> follows the escape rules used
;; by "quoted" string as described in Section
;; 4.3 of [IMAP4], e.g. for the flag \Seen
;; the corresponding <entry-name> is
;; "/message/flags/\\seen", and for the flag
;; $MDNSent, the corresponding <entry-name>
;; is "/message/flags/$mdnsent".
entry-type-resp = "private" | "shared"
;; metadata item type
entry-type-req = entry-type-resp | "all"
;; perform SEARCH operation on private
;; metadata item, shared metadata item or both
permsg-modsequence = mod-sequence-value
;; per message mod-sequence
mod-sequence-value = 1*DIGIT
;; Positive unsigned 64-bit integer (mod-sequence)
;; (1 <= n < 18,446,744,073,709,551,615)
mod-sequence-valzer = "0" | mod-sequence-value
search_sort_mod_seq = "(" "MODSEQ" SP mod-sequence-value ")"
sort-key =/ "MODSEQ"
;;Borrowed from IMAP4rev1 and modified accordingly:
mailbox-data =/ "SEARCH" [SP nz-number *(SP nz-number) search_sort_mod_seq] /
"SORT" [SP nz-number *(SP nz-number) search_sort_mod_seq]
attr-flag = "\\Answered" / "\\Flagged" / "\\Deleted" /
"\\Seen" / "\\Draft" / attr-flag-keyword /
attr-flag-extension
;; Does not include "\Recent"
attr-flag-extension = "\\" atom
;; Future expansion. Client implementations
;; MUST accept flag-extension flags. Server
;; implementations MUST NOT generate
;; flag-extension flags except as defined by
;; future standard or standards-track
;; revisions of this specification.
attr-flag-keyword = atom
6. Security Considerations
As a conditional STORE operation must be atomic for a message set,
an implementation may choose to use some kind of message or even
mailbox level locking for the duration of the conditional STORE
operation. Such implementation may suffer from a Deny of Service
Attack when conditional STORE is executed on a large mailbox.
Other IMAP4 security issues can be found in Security Considerations
section of [IMAP4].
7. References
7.1. Normative References
[KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997.
[ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
ABNF", RFC 2234, Internet Mail Consortium, Demon Internet Ltd,
November 1997.
[IMAP4] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 3501, University of Washington, March 2003.
[ANNOTATE] Gellens, R., Daboo, C., "IMAP ANNOTATE Extension",
work in progress.
<http://www.ietf.org/internet-drafts/draft-ietf-imapext-annotate-xx.txt>
[SORT] Crispin, M., "Internet Message Access Protocol -- SORT
Extension", work in progress.
<http://www.ietf.org/internet-drafts/draft-crispin-imapext-sort-xx.txt>
7.2. Informative References
[ACAP] Newman, Myers, "ACAP -- Application Configuration Access
Protocol", RFC 2244, Innosoft, Netscape, November 1997.
<ftp://ftp.isi.edu/in-notes/rfc2244.txt>
[ACL] Myers, "IMAP4 ACL extension", RFC 2086, Carnegie Mellon,
January 1997.
<ftp://ftp.isi.edu/in-notes/rfc2086.txt>
[NTP] Mills, D, "Network Time Protocol (Version 3) Specification,
Implementation and Analysis", RFC 1305, March 1992.
<ftp://ftp.isi.edu/in-notes/rfc1305.txt>
8. Acknowledgments
Some text was borrowed from "IMAP ANNOTATE Extension" by Randall Gellens
and Cyrus Daboo, and "ACAP -- Application Configuration Access Protocol"
by Chris Newman and John Myers.
Many thanks to Randall Gellens for his comments on how CONDSTORE should
interact with ANNOTATE extension and for thorough review of the document.
Authors also acknowledge the feedback provided by Cyrus Daboo, Larry
Greenfield, Chris Newman, Harrie Hazewinkel, Arnt Gulbrandsen and Timo
Sirainen.
9. Author's Addresses
Alexey Melnikov
mailto: mel@messagingdirect.com
ACI WorldWide/MessagingDirect
59 Clarendon Road, Watford, Hertfordshire,
WD17 1FQ, United Kingdom
Steve Hole
mailto: Steve.Hole@messagingdirect.com
ACI WorldWide/MessagingDirect
#900, 10117 Jasper Avenue,
Edmonton, Alberta, T5J 1W8, CANADA
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