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rfc:rfc5257

Network Working Group C. Daboo Request for Comments: 5257 Apple Inc. Category: Experimental R. Gellens

                                                 QUALCOMM Incorporated
                                                             June 2008
       Internet Message Access Protocol - ANNOTATE Extension

Status of This Memo

 This memo defines an Experimental Protocol for the Internet
 community.  It does not specify an Internet standard of any kind.
 Discussion and suggestions for improvement are requested.
 Distribution of this memo is unlimited.

Abstract

 The ANNOTATE extension to the Internet Message Access Protocol
 permits clients and servers to maintain "meta data" for messages, or
 individual message parts, stored in a mailbox on the server.  For
 example, this can be used to attach comments and other useful
 information to a message.  It is also possible to attach annotations
 to specific parts of a message, so that, for example, they could be
 marked as seen, or important, or a comment added.
 Note that this document was the product of a WG that had good
 consensus on how to approach the problem.  Nevertheless, the WG felt
 it did not have enough information on implementation and deployment
 hurdles to meet all of the requirements of a Proposed Standard.  The
 IETF solicits implementations and implementation reports in order to
 make further progress.
 Implementers should be aware that this specification may change in an
 incompatible manner when going to Proposed Standard status.  However,
 any incompatible changes will result in a new capability name being
 used to prevent problems with any deployments of the experimental
 extension.

Daboo & Gellens Experimental [Page 1] RFC 5257 IMAP ANNOTATE Extension June 2008

Table of Contents

 1. Introduction and Overview .......................................3
 2. Conventions Used in This Document ...............................4
 3. Data Model ......................................................4
    3.1. Overview ...................................................4
    3.2. Namespace of Entries and Attributes ........................4
         3.2.1. Entry Names .........................................5
         3.2.2. Attribute Names .....................................7
    3.3. Private Versus Shared ......................................7
    3.4. Access Control .............................................8
    3.5. Access to Standard IMAP Flags and Keywords ................11
 4. IMAP Protocol Changes ..........................................11
    4.1. General Considerations ....................................11
    4.2. ANNOTATE Parameter with the SELECT/EXAMINE Commands .......12
    4.3. ANNOTATION Message Data Item in FETCH Command .............12
    4.4. ANNOTATION Message Data Item in FETCH Response ............14
    4.5. ANNOTATION Message Data Item in STORE .....................16
    4.6. ANNOTATION Interaction with COPY ..........................18
    4.7. ANNOTATION Message Data Item in APPEND ....................18
    4.8. ANNOTATION Criterion in SEARCH ............................19
    4.9. ANNOTATION Key in SORT ....................................20
    4.10. New ACL Rights ...........................................21
 5. Formal Syntax ..................................................21
 6. IANA Considerations ............................................23
    6.1. Entry and Attribute Registration Template .................23
    6.2. Entry Registrations .......................................24
         6.2.1. /comment ...........................................24
         6.2.2. /flags .............................................24
         6.2.3. /altsubject ........................................25
         6.2.4. /<section-part>/comment ............................25
         6.2.5. /<section-part>/flags/seen .........................26
         6.2.6. /<section-part>/flags/answered .....................26
         6.2.7. /<section-part>/flags/flagged ......................27
         6.2.8. /<section-part>/flags/forwarded ....................27
    6.3. Attribute Registrations ...................................28
         6.3.1. value ..............................................28
         6.3.2. size ...............................................28
    6.4. Capability Registration ...................................28
 7. Internationalization Considerations ............................29
 8. Security Considerations ........................................29
 9. References .....................................................29
    9.1. Normative References ......................................29
    9.2. Informative References ....................................30
 10. Acknowledgments ...............................................30

Daboo & Gellens Experimental [Page 2] RFC 5257 IMAP ANNOTATE Extension June 2008

1. Introduction and Overview

 The ANNOTATE extension is present in any IMAP [RFC3501]
 implementation that returns "ANNOTATE-EXPERIMENT-1" as one of the
 supported capabilities in the CAPABILITY response.
 This extension makes the following changes to the IMAP protocol:
   a.  adds a new ANNOTATION message data item for use in FETCH.
   b.  adds a new ANNOTATION message data item for use in STORE.
   c.  adds a new ANNOTATION search criterion for use in SEARCH.
   d.  adds a new ANNOTATION sort key for use in the SORT extension.
   e.  adds a new ANNOTATION data item for use in APPEND.
   f.  adds a new requirement on the COPY command.
   g.  adds a new ANNOTATE parameter for use with the SELECT/EXAMINE
       commands.
   h.  adds two new response codes to indicate store failures of
       annotations.
   i.  adds a new untagged response code for the SELECT or EXAMINE
       commands to indicate the maximum sized annotation that can be
       stored.
   j.  adds a new Access Control List (ACL) "bit" for use with the ACL
       extensions [RFC2086] and [RFC4314].
 The data model used for the storage of annotations is based on the
 Application Configuration Access Protocol [RFC2244].  Note that there
 is no inheritance in annotations.
 If a server supports annotations, then it MUST store all annotation
 data permanently, i.e., there is no concept of "session only"
 annotations that would correspond to the behavior of "session" flags
 as defined in the IMAP base specification.
 In order to provide optimum support for a disconnected client (one
 that needs to synchronize annotations for use when offline), servers
 SHOULD also support the Conditional STORE [RFC4551] extension.
 The rest of this document describes the data model and protocol
 changes more rigorously.

Daboo & Gellens Experimental [Page 3] RFC 5257 IMAP ANNOTATE Extension June 2008

2. Conventions Used in This Document

 The examples in this document use "C:" and "S:" to 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 [RFC2119].

3. Data Model

3.1. Overview

 The data model for annotations in ANNOTATE uses a uniquely named
 entry that contains a set of standard attributes.  Thus, a single
 coherent unit of "meta data" for a message is stored as a single
 entry, made up of several attributes.
 For example, a comment annotation added to a message has an entry
 name of "/comment".  This entry is composed of several attributes
 such as "value", "size", etc., that contain the properties and data
 of the entry.
 The protocol changes to IMAP, described below, allow a client to
 access or change the values of any attribute in any entry in a
 message annotation, assuming it has sufficient access rights to do so
 (see Section 3.4 for specifics).

3.2. Namespace of Entries and Attributes

 A message may contain zero or more annotations, each of which is a
 single uniquely named entry.  Each entry has a hierarchical name,
 with each component of the name separated by a slash ("/").  An entry
 name MUST NOT contain two consecutive "/" characters and MUST NOT end
 with a "/" character.
 Each entry is made up of a set of attributes.  Each attribute has a
 hierarchical name, with each component of the name separated by a
 period (".").  An attribute name MUST NOT contain two consecutive "."
 characters and MUST NOT end with a "." character.
 The value of an attribute is "NIL" (has no value), or is a string of
 zero or more octets.
 Entry and attribute names MUST NOT contain asterisk ("*") or percent
 ("%") characters, and MUST NOT contain non-ASCII characters or the
 NULL octet.  Invalid entry or attribute names result in a BAD
 response in any IMAP commands where they are used.

Daboo & Gellens Experimental [Page 4] RFC 5257 IMAP ANNOTATE Extension June 2008

 Attribute names MUST NOT contain any hierarchical components with the
 names "priv" or "shared", as those have special meaning (see Section
 3.3).
 Entry and attribute names are case-sensitive.
 Use of control or punctuation characters in entry and attribute names
 is strongly discouraged.
 This specification defines an initial set of entry and attribute
 names available for use in message annotations.  In addition, an
 extension mechanism is described to allow additional names to be
 added as needed.

3.2.1. Entry Names

 Entry names MUST be specified in a standards track or IESG approved
 experimental RFC, or fall under the vendor namespace.  See Section
 6.1 for the registration template.
 /
    Defines the top-level of entries associated with an entire
    message.  This entry itself does not contain any attributes.  All
    entries that start with a numeric character ("0" - "9") refer to
    an annotation on a specific body part.  All other entries are for
    annotations on the entire message.
 /comment
    Defines a comment or note associated with an entire message.
 /flags
    This entry hierarchy is reserved for future use.
 /altsubject
    Contains text supplied by the message recipient to be used by the
    client, instead of the original message Subject.
 /vendor/<vendor-token>
    Defines the top-level of entries associated with an entire message
    as created by a particular product of some vendor.  These sub-
    entries can be used by vendors to provide client-specific
    annotations.  The vendor-token MUST be registered with IANA, using
    the [RFC2244] vendor subtree registry.
 /<section-part>
    Defines the top-level of entries associated with a specific body
    part of a message.  This entry itself does not contain any
    attributes.  The section-part is a numeric part specifier.  Its

Daboo & Gellens Experimental [Page 5] RFC 5257 IMAP ANNOTATE Extension June 2008

    syntax is the same as the section-part ABNF element defined in
    [RFC3501].  The server MUST return a BAD response if the client
    uses an incorrect part specifier (either incorrect syntax or a
    specifier referring to a non-existent part).  The server MUST
    return a BAD response if the client uses an empty part specifier
    (which is used in IMAP to represent the entire message).
 /<section-part>/comment
    Defines a comment or note associated with a specific body part of
    a message.
 /<section-part>/flags
    Defines the top-level of entries associated with the flag state
    for a specific body part of a message.  All sub-entries are
    maintained entirely by the client.  There is no implicit change to
    any flag by the server.
        /<section-part>/flags/seen
           This is similar to the IMAP \Seen flag, except it applies
           to only the body part referenced by the entry.
        /<section-part>/flags/answered
           This is similar to the IMAP \Answered flag, except it
           applies to only the body part referenced by the entry.
        /<section-part>/flags/flagged
           This is similar to the IMAP \Flagged flag, except it
           applies to only the body part referenced by the entry.
        /<section-part>/flags/forwarded
           This is similar to the IMAP $Forwarded keyword, except it
           applies to only the body part referenced by the entry.
    Defines flags for a specific body part of a message.  The "value"
    attribute of each of the entries described above must be either
    "1", "0", or "NIL".  "1" corresponds to the flag being set.
 /<section-part>/vendor/<vendor-token>
    Defines the top-level of entries associated with a specific body
    part of a message as created by a particular product of some
    vendor.  This entry can be used by vendors to provide client
    specific annotations.  The vendor-token MUST be registered with
    IANA.

Daboo & Gellens Experimental [Page 6] RFC 5257 IMAP ANNOTATE Extension June 2008

3.2.2. Attribute Names

 Attribute names MUST be specified in a standards track or IESG
 approved experimental RFC.  See Section 6.1 for the registration
 template.
 All attribute names implicitly have a ".priv" and a ".shared" suffix
 that maps to private and shared versions of the entry.  Searching or
 fetching without using either suffix will include both.  The client
 MUST specify either a ".priv" or ".shared" suffix when storing an
 annotation or sorting on annotations.
 value
    A string or binary data representing the value of the annotation.
    To delete an annotation, the client can store "NIL" into the
    value.  If the client requests the value attribute for a non-
    existent entry, then the server MUST return "NIL" for the value.
    The content represented by the string is determined by the
    content-type used to register the entry (see Section 6.1 for entry
    registration templates).  Where applicable, the registered
    content-type MUST include a charset parameter.  Text values SHOULD
    use the utf-8 [RFC3629] character set.  Note that binary data
    (data which may contain the NULL octet) is allowed (e.g., for
    storing images), and this extension uses the "literal8" syntax
    element [RFC4466] to allow such data to be written to or read from
    the server.
 size
    The size of the value, in octets.  Set automatically by the
    server, read-only to clients.  If the client requests the size
    attribute for a non-existent entry, then the server MUST return
    "0" (zero) for the size.

3.3. Private Versus Shared

 Some IMAP mailboxes are private, accessible only to the owning user.
 Other mailboxes are not, either because the owner has set an ACL
 [RFC4314] that permits access by other users, or because it is a
 shared mailbox.
 This raises the issue of shared versus private annotations.
 If all annotations are private, it is then impossible to have
 annotations in a shared or otherwise non-private mailbox be visible
 to other users.  This eliminates what could be a useful aspect of
 annotations in a shared environment.  An example of such use is a
 shared IMAP folder containing bug reports.  Engineers may want to use

Daboo & Gellens Experimental [Page 7] RFC 5257 IMAP ANNOTATE Extension June 2008

 annotations to add information to existing messages, indicate
 assignments, status, etc.  This use requires shared annotations.
 If all annotations are shared, it is impossible to use annotations
 for private notes on messages in shared mailboxes.  Also, modifying
 an ACL to permit access to a mailbox by other users may
 unintentionally expose private information.
 There are also situations in which both shared and private
 annotations are useful.  For example, an administrator may want to
 set shared annotations on messages in a shared folder, which
 individual users may wish to supplement with additional notes.
 If shared and private annotations are to coexist, we need a clear way
 to differentiate them.  Also, it should be as easy as possible for a
 client to access both and not overlook either.  There is also a
 danger in allowing a client to store an annotation without knowing if
 it is shared or private.
 This document proposes two standard suffixes for all attributes:
 ".shared" and ".priv".  A SEARCH or FETCH command that specifies
 neither, uses both.  STORE, APPEND, and SORT commands MUST explicitly
 use ".priv" or ".shared" suffixes.
 If the ANNOTATE extension is present, support for shared annotations
 in servers is REQUIRED, while support for private annotations in
 servers is OPTIONAL.  This recognizes the fact that support for
 private annotations may introduce a significant increase in
 complexity to a server in terms of tracking ownership of the
 annotations, how quota is determined for users based on their own
 annotations, etc.  Clients that support the ANNOTATE extension MUST
 handle both shared and private annotations.

3.4. Access Control

 A user needs to have appropriate rights in order to read or write
 ".priv" or ".shared" annotation values.  How those rights are
 calculated depends on whether or not the ACL [RFC2086] extension or
 its update [RFC4314] is present.  If a client attempts to store or
 fetch an annotation to which they do not have the appropriate rights,
 the server MUST respond with a NO response.
 When the ACL extension is not present, access to annotation values is
 governed by the nature of the selected state, in particular whether
 the mailbox was SELECTED or EXAMINED in READ-ONLY or READ-WRITE mode.

Daboo & Gellens Experimental [Page 8] RFC 5257 IMAP ANNOTATE Extension June 2008

 When the ACL extension is present, the server MUST recognize the new
 ACL "n" right, in addition to the ones defined by the ACL extension
 itself.
 For ".priv" annotation values, the "r" right controls both read and
 write access.  When it is on, access to ".priv" annotations is
 allowed; when it is off, access to ".priv" annotations is disallowed.
 For ".shared" annotation values, the "r" right controls read access.
 When it is on, ".shared" annotations can be read; when it is off,
 ".shared" annotations cannot be read.
 For ".shared" annotation values, the "n" right controls write access.
 When it is on, ".shared" annotations can be changed or created
 through either a STORE or APPEND command; when it is off, ".shared"
 annotations cannot be changed or created.  The "n" right constitutes
 a "shared flag right" as defined in Section 6.2 of [RFC4314].

Daboo & Gellens Experimental [Page 9] RFC 5257 IMAP ANNOTATE Extension June 2008

 A summary of all the access control restrictions is tabulated below
 +---------------+---------------+-----------------------------------+
 |  Server Type  | Action on     | Type of mailbox                   |
 |               | annotation    |                                   |
 +===============+===============+===================================+
 |               |               |                                   |
 |               | read .priv    | Any mailbox that can be SELECTED  |
 |               | values        | or EXAMINED.                      |
 |               |               |                                   |
 |               +---------------+-----------------------------------+
 |               |               |                                   |
 |               | write .priv   | Any SELECTED [READ-WRITE] mailbox.|
 |               | values        | SELECTED [READ-ONLY] mailboxes MAY|
 | Server        |               | also permit writes.               |
 | without       |               |                                   |
 | ACL Extension +---------------+-----------------------------------+
 |               |               |                                   |
 |               | read .shared  | Any mailbox that can be SELECTED  |
 |               | values        | or EXAMINED.                      |
 |               |               |                                   |
 |               +---------------+-----------------------------------+
 |               |               |                                   |
 |               | write .shared | Any mailbox that can be SELECTED  |
 |               | values        | or EXAMINED and is [READ-WRITE].  |
 |               |               |                                   |
 +---------------+---------------+-----------------------------------+
 |               |               |                                   |
 |               | read .priv    | Any mailbox with the "r"          |
 |               | values        | ACL right.                        |
 |               |               |                                   |
 |               +---------------+-----------------------------------+
 |               |               |                                   |
 |               | write .priv   | Any mailbox with the "r"          |
 | Server        | values        | ACL right.                        |
 | with          |               |                                   |
 | ACL Extension +---------------+-----------------------------------+
 |               |               |                                   |
 |               | read .shared  | Any mailbox with the "r"          |
 |               | values        | ACL right.                        |
 |               |               |                                   |
 |               +---------------+-----------------------------------+
 |               |               |                                   |
 |               | write .shared | Any mailbox with the "n"          |
 |               | values        | ACL right.                        |
 |               |               |                                   |
 +---------------+---------------+-----------------------------------+

Daboo & Gellens Experimental [Page 10] RFC 5257 IMAP ANNOTATE Extension June 2008

3.5. Access to Standard IMAP Flags and Keywords

 Due to the ambiguity of how private and shared values would map to
 the base IMAP flag and keyword values, the ANNOTATE extension does
 not expose IMAP flags or keywords as entries.  However, the /flags
 annotation entry is reserved for future use and MUST NOT be used by
 clients or servers supporting this extension.
 Clients that need to implement shared and private "flags" can create
 their own annotation entries for those, completely bypassing the base
 IMAP flag/keyword behavior.

4. IMAP Protocol Changes

4.1. General Considerations

 Servers may be able to offer only a limited level of support for
 annotations in mailboxes, and it is useful for clients to be able to
 know what level of support is available.  Servers MUST return an
 ANNOTATIONS response code during the SELECT or EXAMINE command for a
 mailbox to indicate the level of support.  Possible data items used
 with the ANNOTATIONS response code are:
    "NONE" - this indicates that the mailbox being selected does not
    support annotations at all.  Clients MUST NOT attempt to use
    annotation extensions in commands for this mailbox.
    "READ-ONLY" - this indicates that the annotations supported by the
    mailbox cannot be changed by the client.  Clients MUST NOT attempt
    to store annotations on any messages in a mailbox with this
    response code.
    "NOPRIVATE" - this indicates that the server does not support
    private annotations on the mailbox.  Only shared annotations are
    supported.  Clients SHOULD only attempt to read or store
    annotations attributes with the ".shared" suffix.  If a client
    uses an attribute with the ".priv" suffix in a FETCH command, then
    servers should return the attribute value in the FETCH response as
    "NIL".  If a client uses an attribute with the ".priv" suffix in a
    STORE command (or an APPEND command targeted at the mailbox), then
    the server MUST return a NO response.
    numeric values - if servers support writable annotations, then the
    server MUST indicate the maximum size in octets for an annotation
    value by providing the maximum size value in the response code.
    Clients MUST NOT store annotation values of a size greater than
    the amount indicated by the server.  Servers MUST accept a minimum

Daboo & Gellens Experimental [Page 11] RFC 5257 IMAP ANNOTATE Extension June 2008

    annotation data size of at least 1024 octets if annotations can be
    written.
 In addition, the server MAY limit the total number of annotations for
 a single message.  However, the server MUST provide a minimum
 annotation count per message of at least 10.

4.2. ANNOTATE Parameter with the SELECT/EXAMINE Commands

 The ANNOTATE extension defines a single optional SELECT parameter
 [RFC4466] "ANNOTATE", which is used to turn on unsolicited responses
 for annotations as described in Section 4.4.  This optional parameter
 results in a per-mailbox state change, i.e., it must be used in each
 SELECT/EXAMINE command in order to be effective, irrespective of
 whether it was used in a previous SELECT/EXAMINE during the same
 session.
 Example:
       C: a SELECT INBOX (ANNOTATE)
       S: * FLAGS (\Answered \Flagged \Draft \Deleted \Seen)
       S: * OK [PERMANENTFLAGS (\Answered \Flagged \Draft
                                         \Deleted \Seen \*)]
       S: * 10268 EXISTS
       S: * 1 RECENT
       S: * OK [UNSEEN 10268]
       S: * OK [UIDVALIDITY 890061587]
       S: * OK [UIDNEXT 34643]
       S: * OK [ANNOTATIONS 20480 NOPRIVATE]
       S: a OK [READ-WRITE] Completed
    In the above example, a SELECT command with the ANNOTATE parameter
    is issued.  The response from the server includes the required
    ANNOTATIONS response that indicates that the server supports
    annotations up to a maximum size of 20480 octets, and does not
    support private annotations (only shared).

4.3. ANNOTATION Message Data Item in FETCH Command

 This extension adds an ANNOTATION message data item to the FETCH
 command.  This allows clients to retrieve annotations for a range of
 messages in the currently selected mailbox.
 ANNOTATION <entry-specifier> <attribute-specifier>
    The ANNOTATION message data item, when used by the client in the
    FETCH command, takes an entry specifier and an attribute
    specifier.

Daboo & Gellens Experimental [Page 12] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a FETCH 1 (ANNOTATION (/comment value))
         S: * 1 FETCH (ANNOTATION (/comment
                                     (value.priv "My comment"
                                      value.shared "Group note")))
         S: a OK Fetch complete
    In the above example, the content of the "value" attribute for the
    "/comment" entry is requested by the client and returned by the
    server.  Since neither ".shared" nor ".priv" was specified, both
    are returned.
 "*" and "%" wild card characters can be used in entry specifiers to
 match one or more characters at that position, with the exception
 that "%" does not match the "/" hierarchy delimiter.  Thus, an entry
 specifier of "/%" matches entries such as "/comment" and
 "/altsubject", but not "/1/comment".
 Example:
         C: a UID FETCH 1123 (UID ANNOTATION
                              (/* (value.priv size.priv)))
         S: * 12 FETCH (UID 1123 ANNOTATION
                (/comment (value.priv "My comment"
                                     size.priv "10")
                 /altsubject (value.priv "Rhinoceroses!"
                                     size.priv "13")
                 /vendor/foobar/label.priv
                                     (value.priv "label43"
                                      size.priv "7")
                 /vendor/foobar/personality
                                     (value.priv "Tallulah Bankhead"
                                      size.priv "17")))
         S: a OK Fetch complete
    In the above example, the contents of the private "value" and
    "size" attributes for any entries in the "/" hierarchy are
    requested by the client and returned by the server.

Daboo & Gellens Experimental [Page 13] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a FETCH 1 (ANNOTATION (/% value.shared))
         S: * 1 FETCH (ANNOTATION
            (/comment (value.shared "Patch Mangler")
             /altsubject (value.shared "Patches?  We don't
             need no steenkin patches!")))
         S: a OK Fetch complete
    In the above example, the contents of the shared "value"
    attributes for entries at the top level only of the "/" hierarchy
    are requested by the client and returned by the server.
 Entry and attribute specifiers can be lists of atomic specifiers, so
 that multiple items of each type may be returned in a single FETCH
 command.
 Example:
         C: a FETCH 1 (ANNOTATION
              ((/comment /altsubject) value.priv))
         S: * 1 FETCH (ANNOTATION
              (/comment (value.priv "What a chowder-head")
               /altsubject (value.priv "How to crush beer cans")))
         S: a OK Fetch complete
    In the above example, the contents of the private "value"
    attributes for the two entries "/comment" and "/altsubject" are
    requested by the client and returned by the server.

4.4. ANNOTATION Message Data Item in FETCH Response

 The ANNOTATION message data item in the FETCH response displays
 information about annotations in a message.
 ANNOTATION parenthesized list
    The response consists of a list of entries, each of which have a
    list of attribute-value pairs.

Daboo & Gellens Experimental [Page 14] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a FETCH 1 (ANNOTATION (/comment value))
         S: * 1 FETCH (ANNOTATION (/comment
                                    (value.priv "My comment"
                                     value.shared NIL)))
         S: a OK Fetch complete
    In the above example, a single entry with a single attribute-value
    pair is returned by the server.  Since the client did not specify
    a ".shared" or ".priv" suffix, both are returned.  Only the
    private attribute has a value (the shared value is "NIL").
 Example:
         C: a FETCH 1 (ANNOTATION
              ((/comment /altsubject) value))
         S: * 1 FETCH (ANNOTATION
              (/comment (value.priv "My comment"
                                   value.shared NIL)
               /altsubject (value.priv "My subject"
                                   value.shared NIL)))
         S: a OK Fetch complete
    In the above example, two entries, each with a single attribute-
    value pair, are returned by the server.  Since the client did not
    specify a ".shared" or ".priv" suffix, both are returned.  Only
    the private attributes have values; the shared attributes are
    "NIL".
 Example:
         C: a FETCH 1 (ANNOTATION
                         (/comment (value size)))
         S: * 1 FETCH (ANNOTATION
                         (/comment
                             (value.priv "My comment"
                              value.shared NIL
                              size.priv "10"
                              size.shared "0")))
         S: a OK Fetch complete
    In the above example, a single entry with two attribute-value
    pairs is returned by the server.  Since the client did not specify
    a ".shared" or ".priv" suffix, both are returned.  Only the
    private attributes have values; the shared attributes are "NIL".

Daboo & Gellens Experimental [Page 15] RFC 5257 IMAP ANNOTATE Extension June 2008

 Servers SHOULD send ANNOTATION message data items in unsolicited
 FETCH responses if an annotation entry is changed by a third-party,
 and the ANNOTATE select parameter was used.  This allows servers to
 keep clients updated with changes to annotations by other clients.
 Unsolicited ANNOTATION responses MUST NOT include ANNOTATION data
 values -- only the entry name of the ANNOTATION that has changed.
 This restriction avoids sending ANNOTATION data values (which may be
 large) to a client unless the client explicitly asks for the value.
 Example:
         C: a STORE 1 +FLAGS (\Seen)
         S: * 1 FETCH (FLAGS (\Seen))
                       ANNOTATION (/comment))
         S: a OK STORE complete
    In the above example, an unsolicited ANNOTATION response is
    returned during a STORE command.  The unsolicited response
    contains only the entry name of the annotation that changed, and
    not its value.

4.5. ANNOTATION Message Data Item in STORE

 ANNOTATION <parenthesized entry-attribute-value list>
    Sets the specified list of entries by adding or replacing the
    specified attributes with the values provided.  Clients can use
    "NIL" for values of attributes it wants to remove from entries.
 The ANNOTATION message data item used with the STORE command has an
 implicit ".SILENT" behavior.  This means the server does not generate
 an untagged FETCH in response to the STORE command and assumes that
 the client updates its own cache if the command succeeds.  Though
 note, that if the Conditional STORE extension [RFC4551] is present,
 then an untagged FETCH response with a MODSEQ data item will be
 returned by the server as required by [RFC4551].
 If the server is unable to store an annotation because the size of
 its value is too large, the server MUST return a tagged NO response
 with a "[ANNOTATE TOOBIG]" response code.
 If the server is unable to store a new annotation because the maximum
 number of allowed annotations has already been reached, the server
 MUST return a tagged NO response with a "[ANNOTATE TOOMANY]" response
 code.

Daboo & Gellens Experimental [Page 16] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a STORE 1 ANNOTATION (/comment
                                  (value.priv "My new comment"))
         S: a OK Store complete
    In the above example, the entry "/comment" is created (if not
    already present).  Its private attribute "value" is created if not
    already present, or replaced if it exists.  "value.priv" is set to
    "My new comment".
 Example:
         C: a STORE 1 ANNOTATION (/comment
                                  (value.shared NIL))
         S: a OK Store complete
    In the above example, the shared "value" attribute of the entry
    "/comment" is removed by storing "NIL" into the attribute.
 Multiple entries can be set in a single STORE command by listing
 entry-attribute-value pairs in the list.
 Example:
         C: a STORE 1 ANNOTATION (/comment
                                  (value.priv "Get tix Tuesday")
                                  /altsubject
                                  (value.priv "Wots On"))
         S: a OK Store complete
    In the above example, the entries "/comment" and "/altsubject" are
    created (if not already present) and the private attribute "value"
    is created or replaced for each entry.
 Multiple attributes can be set in a single STORE command by listing
 multiple attribute-value pairs in the entry list.

Daboo & Gellens Experimental [Page 17] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a STORE 1 ANNOTATION (/comment
                                  (value.priv "My new comment"
                                   value.shared "foo's bar"))
         S: a OK Store complete
    In the above example, the entry "/comment" is created (if not
    already present) and the private and shared "value" attributes are
    created if not already present, or replaced if they exist.

4.6. ANNOTATION Interaction with COPY

 The COPY command can be used to move messages from one mailbox to
 another on the same server.  Servers that support the ANNOTATION
 extension MUST, for each message being copied, copy all ".priv"
 annotation data for the current user only, and all ".shared"
 annotation data along with the message to the new mailbox.  The only
 exceptions to this are if the destination mailbox permissions are
 such that either the ".priv" or ".shared" annotations are not
 allowed, or if the destination mailbox is of a type that does not
 support annotations or does not support storing of annotations (a
 mailbox that returns a "NONE" or "READ-ONLY" response code in its
 ANNOTATIONS response), or if the destination mailbox cannot support
 the size of an annotation because it exceeds the ANNOTATIONS value.
 Servers MUST NOT copy ".priv" annotation data for users other than
 the current user.

4.7. ANNOTATION Message Data Item in APPEND

 ANNOTATION <parenthesized entry-attribute-value list>
    Sets the specified list of entries and attributes in the resulting
    message.
 The APPEND command can include annotations for the message being
 appended via the addition of a new append data item [RFC4466].  The
 new data item can also be used with the multi-append [RFC3502]
 extension that allows multiple messages to be appended via a single
 APPEND command.

Daboo & Gellens Experimental [Page 18] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a APPEND drafts ANNOTATION (/comment
              (value.priv "Don't send until I say so")) {310}
         S: + Ready for literal data
         C: MIME-Version: 1.0
         ...
         C:
         S: a OK APPEND completed
    In the above example, a comment with a private value is added to a
    new message appended to the mailbox.  The ellipsis represents the
    bulk of the message.

4.8. ANNOTATION Criterion in SEARCH

 ANNOTATION <entry-name> <attribute-name> <value>
 The ANNOTATION criterion for the SEARCH command allows a client to
 search for a specified string in the value of an annotation entry of
 a message.
 Messages that have annotations with entries matching <entry-name>,
 attributes matching <attribute-name>, and the specified string
 <value> in their values are returned in the SEARCH results.  The "*"
 character can be used in the entry name field to match any content in
 those items.  The "%" character can be used in the entry name field
 to match a single level of hierarchy only.
 Only the "value", "value.priv", and "value.shared" attributes can be
 searched.  Clients MUST NOT specify an attribute other than either
 "value", "value.priv", or "value.shared".  Servers MUST return a BAD
 response if the client tries to search any other attribute.
 Example:
         C: a SEARCH ANNOTATION /comment value "IMAP4"
         S: * SEARCH 2 3 5 7 11 13 17 19 23
         S: a OK Search complete
    In the above example, the message numbers of any messages
    containing the string "IMAP4" in the shared or private "value"
    attribute of the "/comment" entry are returned in the search
    results.

Daboo & Gellens Experimental [Page 19] RFC 5257 IMAP ANNOTATE Extension June 2008

 Example:
         C: a SEARCH ANNOTATION * value.priv "IMAP4"
         S: * SEARCH 1 2 3 5 8 13 21 34
         S: a OK Search complete
    In the above example, the message numbers of any messages
    containing the string "IMAP4" in the private "value" attribute of
    any entry are returned in the search results.

4.9. ANNOTATION Key in SORT

 ANNOTATION <entry-name> <attribute-name>
 The ANNOTATION criterion for the SORT command [RFC5256] instructs the
 server to return the sequence numbers or Unique Identifiers (UIDs) of
 messages in a mailbox, sorted using the values of the specified
 annotations.  The ANNOTATION criterion is available if the server
 returns both ANNOTATE-EXPERIMENT-1 and SORT as supported capabilities
 in the CAPABILITY command response.
 Messages are sorted using the values of the <attribute-name>
 attributes in the <entry-name> entries.
 Clients MUST provide either the ".priv" or ".shared" suffix to the
 attribute name to ensure that the server knows which specific value
 to sort on.
 Only the "value.priv" and "value.shared" attributes can be used for
 sorting.  Clients MUST NOT specify an attribute other than either
 "value.priv" or "value.shared".  Servers MUST return a BAD response
 if the client tries to sort on any other attribute.
 When either "value.priv" or "value.shared" is being sorted, the
 server MUST use the character set value specified in the SORT command
 to determine the appropriate sort order.
 Example:
         C: a SORT (ANNOTATION /altsubject value.shared) UTF-8 ALL
         S: * SORT 2 3 4 5 1 11 10 6 7 9 8
         S: a OK Sort complete
    In the above example, the message numbers of all messages are
    returned, sorted according to the shared "value" attribute of the
    "/altsubject" entry.

Daboo & Gellens Experimental [Page 20] RFC 5257 IMAP ANNOTATE Extension June 2008

 Note that the ANNOTATION sort key must include a fully specified
 entry -- wild cards are not allowed.

4.10. New ACL Rights

 As discussed in Section 3.4, this extension adds a new "n" right to
 the list of rights provided by the ACL extensions [RFC2086] and
 [RFC4314].

5. Formal Syntax

 The following syntax specification uses the Augmented Backus-Naur
 Form (ABNF) notation as specified in [RFC5234].
 Non-terminals referenced but not defined below are as defined by
 [RFC3501] with the new definitions in [RFC4466] superseding those in
 [RFC3501].
 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.
    ann-size          = "NONE" /
                         (("READ-ONLY" / nz-number)
                          [SP "NOPRIVATE"])
                         ; response codes indicating the level of
                         ; support for annotations in a mailbox
    append-ext        =/ att-annotate
                        ; modifies [RFC3501] extension behaviour
    att-annotate      = "ANNOTATION" SP
                             "(" entry-att *(SP entry-att) ")"
    att-search        = "value" / "value.priv" / "value.shared"
                        ; the only attributes that can be searched
    att-sort          = "value.priv" / "value.shared"
                        ; the only attributes that can be sorted
    att-value         = attrib SP value
    attrib            = astring
                        ; dot-separated attribute name
                        ; MUST NOT contain "*" or "%"

Daboo & Gellens Experimental [Page 21] RFC 5257 IMAP ANNOTATE Extension June 2008

    attribs           = attrib / "(" attrib *(SP attrib) ")"
                        ; one or more attribute specifiers
    capability        =/ "ANNOTATE-EXPERIMENT-1"
                        ; defines the capability for this extension
    entries           = entry-match /
                        "(" entry-match *(SP entry-match) ")"
    entry             = astring
                        ; slash-separated path to entry
                        ; MUST NOT contain "*" or "%"
    entry-att         = entry SP "(" att-value *(SP att-value) ")"
    entry-match       = list-mailbox
                        ; slash-separated path to entry
                        ; MAY contain "*" or "%" for use as wild cards
    fetch-att         =/ "ANNOTATION" SP "(" entries SP attribs ")"
                        ; modifies original IMAP fetch-att
    msg-att-dynamic   =/ "ANNOTATION" SP
                           ( "(" entry-att *(SP entry-att) ")" /
                             "(" entry *(SP entry) ")" )
                        ; extends FETCH response with annotation data
    resp-text-code    =/ "ANNOTATE" SP "TOOBIG" /
                         "ANNOTATE" SP "TOOMANY" /
                         "ANNOTATIONS" SP ann-size
                        ; new response codes
    search-key        =/ "ANNOTATION" SP entry-match SP att-search
                         SP value
                        ; modifies original IMAP search-key
    select-param      =/ "ANNOTATE"
                        ; defines the select parameter used with
                        ; ANNOTATE extension
    sort-key          =/ "ANNOTATION" SP entry SP att-sort
                        ; modifies original sort-key
    store-att-flags   =/ att-annotate
                        ; modifies original IMAP STORE command
    value             = nstring / literal8

Daboo & Gellens Experimental [Page 22] RFC 5257 IMAP ANNOTATE Extension June 2008

6. IANA Considerations

 Entry names MUST be specified in a standards track or IESG approved
 experimental RFC, or fall under the vendor namespace.  Vendor names
 MUST be registered.
 Attribute names MUST be specified in a standards track or IESG
 approved experimental RFC.
 Each entry registration MUST include a content-type that is used to
 indicate the nature of the annotation value.  Where applicable, a
 charset parameter MUST be included with the content-type.

6.1. Entry and Attribute Registration Template

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [] Entry        [] Attribute
 Name: ______________________________
 Description: _______________________
 ____________________________________
 ____________________________________
 Content-Type:_______________________
 Contact person: ____________________
         email:  ____________________

Daboo & Gellens Experimental [Page 23] RFC 5257 IMAP ANNOTATE Extension June 2008

6.2. Entry Registrations

 The following templates specify the IANA registrations of annotation
 entries specified in this document.

6.2.1. /comment

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /comment
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.2.2. /flags

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /flags
 Description: Reserved entry hierarchy.
 Content-Type: -
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

Daboo & Gellens Experimental [Page 24] RFC 5257 IMAP ANNOTATE Extension June 2008

6.2.3. /altsubject

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /altsubject
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.2.4. /<section-part>/comment

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /<section-part>/comment
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

Daboo & Gellens Experimental [Page 25] RFC 5257 IMAP ANNOTATE Extension June 2008

6.2.5. /<section-part>/flags/seen

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /<section-part>/flags/seen
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.2.6. /<section-part>/flags/answered

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /<section-part>/flags/answered
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

Daboo & Gellens Experimental [Page 26] RFC 5257 IMAP ANNOTATE Extension June 2008

6.2.7. /<section-part>/flags/flagged

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /<section-part>/flags/flagged
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.2.8. /<section-part>/flags/forwarded

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [X] Entry        [] Attribute
 Name: /<section-part>/flags/forwarded
 Description: Defined in IMAP ANNOTATE extension document.
 Content-Type: text/plain; charset=utf-8
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

Daboo & Gellens Experimental [Page 27] RFC 5257 IMAP ANNOTATE Extension June 2008

6.3. Attribute Registrations

 The following templates specify the IANA registrations of annotation
 attributes specified in this document.

6.3.1. value

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [] Entry        [X] Attribute
 Name: value
 Description: Defined in IMAP ANNOTATE extension document.
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.3.2. size

 To: iana@iana.org
 Subject: IMAP Annotate Registration
 Please register the following IMAP Annotate item:
 [] Entry        [X] Attribute
 Name: size
 Description: Defined in IMAP ANNOTATE extension document.
 Contact person: Cyrus Daboo
         email:  cyrus@daboo.name

6.4. Capability Registration

 This document registers "ANNOTATE-EXPERIMENT-1" as an IMAPEXT
 capability.

Daboo & Gellens Experimental [Page 28] RFC 5257 IMAP ANNOTATE Extension June 2008

7. Internationalization Considerations

 Annotations may contain values that include text strings, and both
 searching and sorting are possible with annotations.  Servers MUST
 follow standard IMAP text normalization, character set conversion,
 and collation rules when such operations are carried out, as would be
 done for other textual fields being searched or sorted on.

8. Security Considerations

 Annotations whose values are intended to remain private MUST be
 stored in ".priv" values instead of ".shared" values, which may be
 accessible to other users.
 Excluding the above issues, the ANNOTATE extension does not raise any
 security considerations that are not present in the base IMAP
 protocol; these issues are discussed in [RFC3501].

9. References

9.1. Normative References

 [RFC2086]  Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2244]  Newman, C. and J. Myers, "ACAP -- Application
            Configuration Access Protocol", RFC 2244, November 1997.
 [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
            4rev1", RFC 3501, March 2003.
 [RFC3502]  Crispin, M., "Internet Message Access Protocol (IMAP) -
            MULTIAPPEND Extension", RFC 3502, March 2003.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [RFC4314]  Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
            RFC 4314, December 2005.
 [RFC4466]  Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
            ABNF", RFC 4466, April 2006.
 [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
            Syntax Specifications: ABNF", STD 68, RFC 5234, January
            2008.

Daboo & Gellens Experimental [Page 29] RFC 5257 IMAP ANNOTATE Extension June 2008

 [RFC5256]  Crispin, M. and K. Murchison, "Internet Message Access
            Protocol - SORT and THREAD Extensions", RFC 5256, June
            2008.

9.2. Informative References

 [RFC4551]  Melnikov, A. and S. Hole, "IMAP Extension for Conditional
            STORE Operation or Quick Flag Changes Resynchronization",
            RFC 4551, June 2006.

10. Acknowledgments

 Many thanks to Chris Newman for his detailed comments on the first
 draft of this document, and to the participants at the ACAP working
 dinner in Pittsburgh.  The participants of the IMAPext working group
 made significant contributions to this work.

Authors' Addresses

 Cyrus Daboo
 Apple Inc.
 1 Infinite Loop
 Cupertino, CA  95014
 USA
 EMail: cyrus@daboo.name
 URI:   http://www.apple.com/
 Randall Gellens
 QUALCOMM Incorporated
 5775 Morehouse Dr.
 San Diego, CA  92121-2779
 USA
 EMail: randy@qualcomm.com

Daboo & Gellens Experimental [Page 30] RFC 5257 IMAP ANNOTATE Extension June 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 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

 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 rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Daboo & Gellens Experimental [Page 31]

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