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Versions: (draft-gellens-imapext-annotate) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 RFC 5257

IMAP Extensions Working Group                               R. Gellens
Internet Draft: IMAP ANNOTATE Extension                       C. Daboo
Document: draft-ietf-imapext-annotate-02.txt             November 2001

                        IMAP ANNOTATE Extension

Status of this Memo

    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.  Internet-Drafts are
    working documents of the Internet Engineering Task Force (IETF), its
    areas, and its working groups.  Note that other groups may also
    distribute working documents as Internet-Drafts.

    Internet-Drafts are draft documents valid for a maximum of six
    months and may be updated, replaced, or obsoleted by other documents
    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
    http://www.ietf.org/ietf/1id-abstracts.txt.  The list of Internet-
    Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.


Copyright Notice

     Copyright (C) The Internet Society 2001. All Rights Reserved.





























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                           Table of Contents
     1  Abstract  . . . . . . . . . . . . . . . . . . . . . . . . . .  2
     2  Discussion . . . . . . . . . . . . . . . . . . . . . . . . .   2
     3  Conventions Used in This Document . . . . . . . . . . . . . .  2
     4  Document Meta-Data . . . . . . . . . . . . . . . . . . . . .   3
       4.1  Open Issues . . . . . . . . . . . . . . . . . . . . . . .  3
       4.2  Change History . . . . . . . . . . . . . . . . . . . . .   3
     5  Introduction and Overview . . . . . . . . . . . . . . . . . .  4
     6  Data Model . . . . . . . . . . . . . . . . . . . . . . . . .   4
       6.1  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  4
       6.2  Namespace of Entries and Attributes  . . . . . . . . . .   5
         6.2.1  Entry Names . . . . . . . . . . . . . . . . . . . . .  5
         6.2.2  Attribute Names  . . . . . . . . . . . . . . . . . .   7
     7  Private versus Shared . . . . . . . . . . . . . . . . . . . .  8
     8  IMAP Protocol Changes  . . . . . . . . . . . . . . . . . . .   9
       8.1  ANNOTATION Message Data Item in FETCH Command . . . . . .  9
       8.2  ANNOTATION Message Data Item in FETCH Response . . . . .  10
       8.3  ANNOTATION Message Data Item in STORE . . . . . . . . . . 11
       8.4  ANNOTATION Message Data Item in APPEND . . . . . . . . .  13
       8.5  ANNOTATION Criterion in SEARCH  . . . . . . . . . . . . . 13
       8.6  ANNOTATION Key in SORT . . . . . . . . . . . . . . . . .  14
       8.7  ACL Rights  . . . . . . . . . . . . . . . . . . . . . . . 15
     9  Interaction with MODTIME . . . . . . . . . . . . . . . . . .  15
    10  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 15
    11  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  16
      11.1  Entry and Attribute Registration Template . . . . . . . . 16
    12  Security Considerations  . . . . . . . . . . . . . . . . . .  17
    13  References  . . . . . . . . . . . . . . . . . . . . . . . . . 17
    14  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  18
    15  Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . 18
    16  Full Copyright Statement . . . . . . . . . . . . . . . . . .  18

1 Abstract

    The ANNOTATE extension to the Internet Message Access Protocol
    [IMAP4] permits clients and servers to maintain "metadata" for
    messages stored in an IMAP4 mailbox.


2 Discussion

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


3 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].


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    Formal syntax is defined using ABNF [ABNF] as modified by [IMAP4].

    In examples, "C:" and "S:" indicate lines sent by the client and
    server respectively.  Line breaks not preceded by a "C:" or "S:" are
    for editorial clarity only.


4 Document Meta-Data

4.1 Open Issues

    At points in this document open issues are discussed, marked by the
    text "<<<OPEN-ISSUE>>>".  These are items which have not been
    finalized.  Discussion and comment is requested.  Please use the
    IETF IMAP Extensions mailing list, as described in section 2.

4.2 Change History

    Changes from -01 to -02:
     1.  Now require .pric or .shared on store operations.

    Changes from -00 to -01:
     1.  MODTIME moved to its own draft, which this draft now
         depends on.  Thus, Conditional Annotation STORE and
         related items deleted from this draft.
     2.  Private versus Shared Annotations: both are possible
         (separately addressable using ".priv" and ".shared"
         suffixes).  There is a per-mailbox setting for the
         default.  It is an open issue how this is viewed or
         changed by the client.
     3.  In ACLs, the "w" right is needed to updated shared state;
         the "s" right is needed to update private state.
     4.  Various clarifications and text modifications.
     5.  Added 'forwarded' flag for message parts.

    Changes from pre-imapext to -00:
     1.  Clarified text describing attributions, entries, and
         attributes.
     2.  Changed 'modifiedsince' to 'modtime'; referenced ACAP spec.
     3.  Deleted 'queued' flag.
     4.  Expanded and explained smtp-envelope entry.
     5.  Restricted including ANNOTATION data in unsolicited responses
         until the client uses it first.  (Open issue as to if needed).
     6.  Examples now only use valid entries and attributes.
     7.  Updated Security Considerations.
     8.  Content-Type now defaults to text/plain.
     9.  Open Issue: Shared vs. private annotations.
    10.  Open issue: Annotation Modtime untagged response or VALIDTIME
         FETCH data.
    11.  Open issue: Conditional annotation STORE.
    12.  ANNOTATION criterion available if both "ANNOTATE" and "SORT"
         in CAPABILITY command response.


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    13.  Prohibition on annotations in lieu of base spec functionality.
    14.  Specified required ACL rights.
    15.  ANNOTATION message data item in APPEND.
    16.  ANNOTATION-MODTIME message data item in STATUS.
    17.  Replaced ATOM_CHAR with utf8-char.
    18.  Updated other ABNF entries.


5 Introduction and Overview

    The ANNOTATE extension is present in any IMAP4 implementation which
    returns "ANNOTATE" as one of the supported capabilities in the
    CAPABILITY command response.

    The ANNOTATE extension adds a new message data item to the FETCH and
    STORE commands, as well as adding SEARCH and SORT keys and APPEND
    and STATUS modifiers.

    This extension makes the following changes to the IMAP4 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 SORT extension
        e) adds a new ANNOTATION data item for use in APPEND

    The data model used for the storage of annotations is based on that
    of the Application Configuration Access Protocol [ACAP].  Note that
    there is no inheritance in annotations.

    Clients MUST NOT use annotations in lieu of equivalent IMAP base
    specification facilities.  For example, use of a "seen" flag in the
    vendor namespace together with ".PEEK" in fetches.  Such behavior
    would significantly reduce IMAP interoperability.

        <<<OPEN-ISSUE>>>

    A possible exception to this rule is the potential use of annotation
    flags in lieu of or as an alternate means of accessing IMAP flags.

    The rest of this document describes the data model and protocol
    changes more rigorously.


6 Data Model

6.1 Overview

    The data model used in ANNOTATE is that of a uniquely named entry
    which contains a set of standard attributes.  A single coherent unit
    of "metadata" for a message is stored as a single entry, made up of
    several attributes.


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    For example, a comment added to a message has an entry name of
    "/message/comment".  This entry is composed of several attributes
    such as "value", "modtime", etc. which 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 attributes in any entries in a
    message annotation, assuming it has sufficient access rights to do
    so (see section 8.7 for specifics).


6.2 Namespace of Entries and Attributes

    Each message annotation is made up of a set of entries.  Each entry
    has a hierarchical name in UTF-8, with each component of the name
    separated by a slash ("/").

    Each entry is made up of a set of attributes.  Each attribute has a
    hierarchical name in UTF-8, with each component of the name
    separated by a period (".").

    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 be valid UTF-8 strings which do not
    contain the NULL octet.  Invalid entry or attribute names result in
    a BAD response in any IMAP commands where they are used.

    Use of non-visible UTF-8 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 for extensibility.


6.2.1 Entry Names

    Entry names MUST be specified in a standards track or IESG approved
    experimental RFC, or fall under the vendor namespace.  See section
    11.1 for the registration template.

    /message
        Defines the top-level of entries associated with an entire
        message.  This entry itself does not contain any attributes.

    /message/comment
        Defines a comment or note associated with an entire message.




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    /message/flags
        Defines the top-level of entries for client-use flags associated
        with an entire message.  All sub-entries are maintained entirely
        by the client.  There is no implicit change to any flag by the
        server.

    /message/flags/redirected
    /message/flags/forwarded
        Defines client-use flags for an entire message.  The "value"
        attribute of these entries must be either "1", "0" or NIL.  The
        'redirected' flag indicates that a message has been handed off
        to someone else, by resending the message with minimal
        alterations, and in such a way that a reply by the new recipient
        is addressed to the original author, not the user who performed
        the redirection.  The 'forwarded' flag indicates the message was
        resent to another user, embedded within or attached to a new
        message.

    /message/smtp-envelope
        Defines the top-level of entries which together describe the
        SMTP envelope used in delivery of the message.  There are no
        attributes at this level.  The client SHOULD NOT modify the
        /message/smtp-envelope entry or any sub-entries or any of their
        attributes, except in messages which have the DRAFT flag set.
    /message/smtp-envelope/from
    /message/smtp-envelope/to
    /message/smtp-envelope/orcpt
    /message/smtp-envelope/envid
        Contains the properties of the SMTP envelope: 'from' is the
        return-path of the message; 'to' is the recipient of the
        message. 'orcpt' and 'envid' contain the original recipient and
        envelope ID as specified in [SMTP-DSN].

    /message/subject
        Contains text supplied by the message recipient, to be used by
        the client instead of the original message Subject.

    /message/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 attributes.  The vendor-token MUST be registered
        with IANA.

    /body/<part-specifier>
        Defines the top-level of entries associated with a specific body
        part of a message.  This entry itself does not contain any
        attributes.  The part-specifier uses the same part specifier
        syntax as the BODY message data item in the FETCH command
        [IMAP4].




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    /body/<part-specifier>/comment
        Defines a comment or note associated with a specific body part
        of a message.

    /body/<part-specifier>/flags
        Defines the top-level of entries associated with 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.

    /body/<part-specifier>/flags/seen
    /body/<part-specifier>/flags/answered
    /body/<part-specifier>/flags/flagged
    /body/<part-specifier>/flags/forwarded
        Defines flags for a specific body part of a message.  The
        "value" attribute of these entries must be either "1", "0" or
        NIL.

    /body/<part-specifier>/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 attributes.  The vendor-token MUST be registered with
        IANA.


6.2.2 Attribute Names

    Attribute names MUST be specified in a standards track or IESG
    approved experimental RFC, or fall under the vendor namespace.  See
    section 11.1 for the registration template.

    All attribute names implicitly have a ".priv" and a ".shared" suffix
    which maps to private and shared versions of the entry.  Searching
    or fetching without using either suffix includes both.  Storing
    without using either suffix stores into the default.  The default is
    set per-mailbox.  See section 7 for more information.

    value
        The data value of the attribute.

    size
        The size of the value, in octets.  Set automatically by the
        server, read-only to clients.

    modtime
        An opaque value set by the server when this entry is modified.
        It can be used by the client to request notification of which
        entries have changed relative to that of a known entry.  In
        addition to its use in disconnected/synchronization operations,
        it can also be helpful in determining which entries have changed
        while a client is connected. (The value is intended to be used


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        only for comparisons within a server, not as an accurate
        timestamp.) It is described more fully in section 3.1.1 of
        [ACAP].

    content-type
        A MIME [MIME] content type and subtype that describes the nature
        of the content of the "value" attribute.  If not present, a
        value of "text/plain; charset=utf8" is assumed.

    vendor.<vendor-token>
        Defines an attribute associated with a particular product of
        some vendor.  This attribute can be used by vendors to provide
        client specific attributes.  The vendor-token MUST be registered
        with IANA.


7 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
    [ACL-EXT] which 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 impossible to set annotations
    in a shared or otherwise non-private mailbox that are 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 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, fetch, or sort which specifies
    neither uses both.  Store operations MUST explicitly use .priv or


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    .shared suffixes.


8 IMAP Protocol Changes

8.1 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.

    Example:
        C: a FETCH 1 (ANNOTATION ("/message/comment" "value"))
        S: * 1 FETCH (ANNOTATION ("/message/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 "/message/comment" entry is requested by the client
            and returned by the server.  Since neither ".shared" nor
            ".priv" was specified, both are returned.

    "*" and "%" wildcard characters can be used in either specifier to
    match one or more characters at that position, with the exception
    that "%" does not match the hierarchy delimiter for the specifier it
    appears in (that is, "/" for an entry specifier or "." for an
    attribute specifier).  Thus an entry specifier of "/message/%"
    matches entries such as "/message/comment" and "/message/subject",
    but not "/message/flags/redirected".

    Examples:
        C: a FETCH 1 (ANNOTATION ("/message/*" ("value.priv"
           "modtime.priv")))
        S: * 1 FETCH (ANNOTATION
               (("/message/comment" ("value.priv" "My comment"
                                    "modtime.priv" "20000704000001"))
                ("/message/subject" ("value.priv" "Rhinoceroses!"
                                    "modtime.priv" "19991231235959"))
                ("/message/vendor/eudora/label.priv"
                                    ("value.priv"   "label43"
                                     "modtime.priv" "20000705101502"))
                ("/message/vendor/eudora/personality"
                                    ("value.priv"   "Tallulah Bankhead"
                                     "modtime.priv" "20000705101558"))))
        S: a OK Fetch complete



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    In the above example, the contents of the private "value" and
    "modtime" attributes for any entries in the "/message" hierarchy are
    requested by the client and returned by the server.

        C: a FETCH 1 (ANNOTATION ("/message/%" "value.shared"))
        S: * 1 FETCH (ANNOTATION
           (("/message/comment" ("value.shared" "Patch Mangler"))
            ("/message/subject" ("value.shared" "Patches?  We don'
            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
            "/message" 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.

    Examples:
        C: a FETCH 1 (ANNOTATION
             (("/message/comment" "/message/subject") "value.priv"))
        S: * 1 FETCH (ANNOTATION
             (("/message/comment" ("value.priv" "What a chowder-head"))
              ("/message/subject" ("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 "/message/comment" and "/message/subject" are
    requested by the client and returned by the server.


8.2 ANNOTATION Message Data Item in FETCH Response

    The ANNOTATION message data item in the FETCH response displays
    information about annotations in a message.

    ANNOTATION parenthesised list

        The response consists of a list of entries, each of which has a
        list of attribute-value pairs.

    Examples:
        C: a FETCH 1 (ANNOTATION ("/message/comment" "value"))
        S: * 1 FETCH (ANNOTATION ("/message/comment"
                                   ("value.priv" "My comment"
                                    "value.shared" NIL)))
        S: a OK Fetch complete




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    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).

        C: a FETCH 1 (ANNOTATION
             (("/message/comment" "/message/subject") "value"))
        S: * 1 FETCH (ANNOTATION
             (("/message/comment" ("value.priv"   "My comment"
                                   "value.shared" NIL))
              ("/message/subject" ("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.

        C: a FETCH 1 (ANNOTATION
                        ("/message/comment" ("value" "modtime")))
        S: * 1 FETCH (ANNOTATION
                        (("/message/comment"
                            ("value.priv"     "My comment"
                             "value.shared"   NIL
                             "modtime.priv"   "19990203205432"
                             "modtime.shared" NIL))))
        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.

    Servers SHOULD send ANNOTATION message data items in unsolicited
    FETCH responses if an annotation entry is changed by a third-party.
    This allows servers to keep clients updated with changes to
    annotations by other clients.

    Servers MUST NOT include ANNOTATION data in unsolicited responses
    until the client has used ANNOTATION data in a FETCH command.  This
    restriction avoids sending ANNOTATION data to a client until the
    client has shown it is capable of handling it.

        <<<OPEN-ISSUE>>>
    Is this prohibition really necessary?

    * OK [ANNOTATIONS FLAGS MODTIME <modtime> <set>]


8.3 ANNOTATION Message Data Item in STORE



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    ANNOTATION <parenthesised 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.

    Examples:
        C: a STORE 1 ANNOTATION ("/message/comment"
                                 ("value.priv" "My new comment"))
        S: a OK Store complete

    In the above example, the entry "/message/comment" is created (if
    not already present) and the private attribute "value" with data set
    to "My new comment" is created if not already present, or replaced
    if it exists.

        C: a STORE 1 ANNOTATION ("/message/comment"
                                    ("value.shared" NIL))
        S: a OK Store complete

    In the above example, the shared "value" attribute of the entry
    "/message/comment" is removed.

    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 ("/message/comment" ("value.priv"
                                                     "Get tix Tuesday")
                                 "/message/subject" ("value.priv"
                                                     "Wots On"))
        S: a OK Store complete

    In the above example, the entries "/message/comment" and
    "/message/subject" are created (if not already present) and the
    private attribute "value" is created for each entry if not already
    present, or replaced if they exist.

    Multiple attributes can be set in a single STORE command by listing
    multiple attribute-value pairs in the entry list.

    Example:
        C: a STORE 1 ANNOTATION ("/message/comment"
                                 ("value.priv" "My new comment"
                                  "vendor.foobar.priv" "foo's bar"))
        S: a OK Store complete



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    In the above example, the entry "/message/comment" is created (if
    not already present) and the private attributes "value" and
    "vendor.foobar" are created if not already present, or replaced if
    they exist.


8.4 ANNOTATION Message Data Item in APPEND

    ANNOTATION <parenthesised entry-attribute-value list>
        Sets the specified list of entries and attributes in the
        resulting message.

    Example:
        C: a APPEND drafts ANNOTATION ("/message/comment"
             ("value.priv" "Don't send until we hear from Sally")) {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.


8.5 ANNOTATION Criterion in SEARCH

    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.
        ANNOTATION <entry-name> <attribute-name> <value>

    Messages that have annotations with entries matching <entry-name>
    and 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 or attribute name fields to match
    any content in those items.  The "%" character can be used in the
    entry or attribute name fields to match a single level of hierarchy
    only.

    Examples:
        C: a SEARCH ANNOTATION "/message/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
    "/message/comment" entry are returned in the search results.

        C: a SEARCH ANNOTATION "*" "*" "IMAP4"
        S: * SEARCH 1 2 3 5 8 13 21 34


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        S: a OK Search complete

    In the above example, the message numbers of any messages containing
    the string "IMAP4" in any attribute (public or private) of any entry
    are returned in the search results.

    A special case exists when the "modtime" attribute is used as the
    <attribute-name> parameter in the ANNOTATION search criterion.  In
    this case the server matches messages when the corresponding
    "modtime" value is greater than the value supplied in the ANNOTATION
    criterion.  This allows a client, for example, to find out which
    messages contain annotations that have changed since the last time
    it updated its disconnected cache.

    Example:
        C: a SEARCH ANNOTATION "*" "modtime" "1999101713283412"
        S: * SEARCH 1 3 6 10 15 21 28 36 45 55
        S: a OK Search complete

    In the above example, the message numbers of any messages whose
    "modtime" attribute of any entry exceeds the value
    "1999101713283412" are returned in the search results.  Both public
    and private attributes are searched.


8.6 ANNOTATION Key in SORT

    The ANNOTATION criterion for the SORT command [SORT-EXT] instructs
    the server to return the message numbers or UIDs of a mailbox,
    sorted using the values of the specified annotations.  The
    ANNOTATION criterion is available if the server returns both
    "ANNOTATE" and "SORT" as supported capabilities in the CAPABILITY
    command response.
        ANNOTATION <entry-name> <attribute-name>

    Messages are sorted using the values of the <attribute-name>
    attributes in the <entry-name> entries. (The charset argument
    determines sort order, as specified in the SORT extension
    description.)

    Examples:
        C: a SORT (ANNOTATION "/message/subject" "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
    "/message/subject" entry.

    Note that the ANNOTATION sort key must include a fully specified
    entry and attribute -- wildcards are not allowed.


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8.7 ACL Rights

    The "r" right, as specified in [ACL-EXT], is required to use
    annotations in any command other than STORE.

    The "w" right is needed to use shared annotations in the STORE
    command.

    The "s" right is needed to use private annotations in the STORE
    command.

        <<<OPEN-ISSUE>>>

    Should there be a special ACL bit to indicate if annotations are
    shared or private by default for a mailbox?


9 Interaction with MODTIME

    The [MODTIME-EXT] document defines an IMAP extension which allows
    clients to be supplied with an opaque value called a modtime.  The
    specific value is server dependent, but has the property that all
    such values issued by a server are numerically increasing with
    respect to the order of changes.  That is, for any two items, the
    one that was modified later has a greater modtime.


10 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 [SP flag-list] [SP date-time]
                       [SP "ANNOTATION" SP att-annotate]
                       SP literal
                       ; modifies original IMAP4 APPEND command

   att-annotate      = "(" entry-att *(SP entry-att) ")"

   fetch-att         =/ fetch-annotate
                       ; modifies original IMAP4 fetch-att

   fetch-annotate    = "ANNOTATION" SP "(" entries SP attribs ")"
   fetch-ann-resp    = "ANNOTATION" SP "(" entry-att *(SP entry-att) ")"


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   store-att-flags   =/ att-annotate
                       ; modifies original IMAP4 STORE command

   search-key        =/ search-annotate
                       ; modifies original IMAP4 search-key

   search-annotate   = "ANNOTATION" SP entry-match SP attrib-match
                       SP value

   sort-key          =/ sort-annotate
                       ; modifies original
                       ; draft-crispin-imapext-sort-xx.txt sort-key

   sort-annotate     = "ANNOTATION" SP entry SP attrib

   status            =/ "ANNOTATION-MODTIME"
                       ; modifies original IMAP4 STATUS command

   entries           = entry-match /
                       "(" entry-match *(SP entry-match) ")"
   attribs           = attrib-match /
                       "(" attrib-match *(SP attrib-match) ")"
   entry-att         = entry SP "(" att-value *(SP att-value) ")
   att-value         = attrib SP value

   utf8-char         =  %x01-FF
                       ; any character, excluding NUL
   atom-slash        = any utf8-char except "/"
   atom-dot          = any utf8-char except "."

   entry             = DQUOTE 1*atom-slash *("/" 1*atom-slash) DQUOTE
   entry-match       = DQUOTE 1*entry-match-atom
                       *("/" 1*entry-match-atom) DQUOTE
   entry-match-atom  = 1*(list-wildcards / atom-slash)
                       *(list-wildcards / atom-slash)

   attrib            = DQUOTE 1*atom-dot *("/" 1*atom-dot) DQUOTE
   attrib-match      = DQUOTE 1*attrib-match-atom
                       *("/" 1*attrib-match-atom) DQUOTE
   attrib-match-atom = 1*(list-wildcards / atom-dot)
                       *(list-wildcards / atom-dot)

   value             = nstring


11 IANA Considerations

    Both entry names and attribute names MUST be specified in a
    standards track or IESG approved experimental RFC, or fall under the
    vendor namespace.  Vendor names MUST be registered.



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11.1 Entry and Attribute Registration Template

    To: iana@iana.org
    Subject: IMAP Annotate Registration

    Please register the following IMAP Annotate item:

    [] Entry        [] Attribute
    [] Vendor       [] Open: RFC _______

    Name: ______________________________

    Description: _______________________

    ____________________________________

    ____________________________________

    Contact person: ____________________

            email:  ____________________

12 Security Considerations

    Care must be taken to ensure that annotations whose values are
    intended to remain private are not stored in mailboxes which are
    accessible to other users.  This includes mailboxes owned by the
    user by whose ACLs permit access by others as well as any shared
    mailboxes.


13 References

    [ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
    ABNF", RFC 2234, Internet Mail Consortium, Demon Internet Ltd,
    November 1997.

    [ACAP] Newman, Myers, "ACAP -- Application Configuration Access
    Protocol", RFC 2244, Innosoft, Netscape, November 1997.

    [ACL-EXT] Myers, "IMAP4 ACL extension", RFC 2086, Carnegie Mellon,
    January 1997.

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

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

    [MODTIME-EXT] Melnikov, "IMAP Conditional Store", work in progress.
    <http://www.ietf.org/internet-drafts/draft-melnikov-imap-condstore-03.txt>



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    [SMTP-DSN] Moore, "SMTP Service Extension for Delivery Status
    Notifications", RFC 1891, University of Tennessee, January 1996.

    [SORT-EXT] Crispin, "Internet Message Access Protocol -- SORT
    Extension", work in progress.
    <http://www.ietf.org/internet-drafts/draft-ietf-imapext-sort-07.txt>


14 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.


15 Authors' Addresses

    Randall Gellens
    QUALCOMM Incorporated
    5775 Morehouse Dr.
    San Diego, CA   92121-2779
    U.S.A.

    Email: randy@qualcomm.com


    Cyrus Daboo
    Cyrusoft International, Inc.
    Suite 780, 5001 Baum Blvd.
    Pittsburgh, PA 15213
    U.S.A.

    Email: daboo@cyrusoft.com

16 Full Copyright Statement

    Copyright (C) The Internet Society 2001.  All Rights Reserved.

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



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

    This document and the information contained herein is provided on an
    "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
    TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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