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Network Working Group C. Daboo
Internet-Draft Apple Computer
Intended status: Informational October 19, 2006
Expires: April 22, 2007
IMAP METADATA Extension
draft-daboo-imap-annotatemore-10
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
The METADATA extension to the Internet Message Access Protocol
permits clients and servers to maintain "annotations" or "meta data"
on IMAP servers. It is possible to have annotations on a per-mailbox
basis or on the server as a whole. For example, this would allow
comments about the purpose of a particular mailbox to be "attached"
to that mailbox, or a "message of the day" containing server status
information to be made available to anyone logging in to the server.
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Change History (to be removed prior to publication as an RFC)
Changes from -09 to -10:
1. Updated to rfc 4466 reference.
2. Reworded data model description.
3. Reworked LISTEXT so that responses have metadata items after the
mailbox info.
4. Various spelling fixes.
Changes from -08 to -09:
1. Remove content-language attribute and reference.
2. Changed capability and command names.
3. Revised abstract.
Changes from -07 to -08:
1. Changed 'string' formal syntax to 'list-mailbox' and 'astring'
for entry/attribute names.
2. Updated examples to match new astring syntax.
3. Changed CAPABILITY name due to incompatible syntax change.
4. Removed content-type attribute.
5. Added Content-type to IANA registration for entries.
6. Removed vendor attributes.
7. Fixed examples in section 3.3 for multi-mailbox and multi-entry
cases.
8. Removed wildcards for attributes.
9. Entry/attributes can now only be ASCII.
10. Tied up text wrt storing/fetching.
11. Added Conventions section
12. Entry/attributes MUST NOT contain consecutive or trailing '/' or
'.'.
13. Changed to use IMAP ABNF extensions document for some formal
syntax items.
Changes from -06 to -07:
1. Reworded /checkperiod item.
2. Clarified unsolicited response behavior.
Changes from -05 to -06:
1. Removed 'modifiedsince' attribute as there is currently no use
for it.
2. Added content-language attribute.
3. Changed access to allow .priv and .shared on any mailbox returned
by LIST/LSUB.
4. Added IANA registrations for items defined in this document.
5. Added latest IPR statement.
6. Updated references.
Changes from -04 to -05:
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1. Fix for valid IMAP state of commands.
2. Fix formatting, ID nits etc.
Changes from -03 to -04:
1. Allow retrieval of shared annotations for READ-ONLY mailbox.
2. Clarification of annotation loss on implicit removal of \Noselect
mailboxes.
3. Now requires roll-back of all changes to matching mailboxes if
there is a partial failure in SETANNOTATION.
Changes from -02 to -03:
1. Reworked entry naming scheme to split out mailbox name and use
empty string for server items.
Changes from -01 to -02:
1. SETANNOTATION lists use (..).
2. Explicitly state behavior of unsolicited responses.
3. Adding SHOULD behavior for rename/delete of mailboxes.
4. Added statement about supporting annotations on \Noselect
mailboxes.
5. Cleaned up formal syntax to use IMAP string type for entry and
attributes, with requirements on how the string is formatted.
6. Use of ACAP vendor subtree registry for vendor tokens.
Changes from -00 to -01:
1. Multiple entry-att responses are now simply delimited by spaces
in line with ANNOTATE spec. Adjusted examples to match.
2. Fixed entry-list formal syntax item to account for unsolicited
parenthesized list of entries.
3. Removed setentries formal syntax item for simplicity since its
only used once.
4. Removed reference to 'message annotation' in section 5.1.
5. Changed formal syntax to restrict top level entries to /server
and /mailbox/{...} only. Re-arranged entry names section to
account for this change.
6. Added comment and example for ANNOTATION response to allow
servers to return separate responses for each entry if desired.
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Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 5
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Namespace of entries and attributes . . . . . . . . . . . 6
3.2.1. Entry Names . . . . . . . . . . . . . . . . . . . . . 7
3.2.2. Attribute Names . . . . . . . . . . . . . . . . . . . 8
3.3. Private versus Shared and Access Control . . . . . . . . . 9
4. IMAP Protocol Changes . . . . . . . . . . . . . . . . . . . . 9
4.1. General Considerations . . . . . . . . . . . . . . . . . . 9
4.2. GETMETADATA Command . . . . . . . . . . . . . . . . . . . 10
4.3. Extended LIST Command Extensions . . . . . . . . . . . . . 12
4.3.1. Unsolicited LIST response . . . . . . . . . . . . . . 16
4.4. SETMETADATA Command . . . . . . . . . . . . . . . . . . . 16
4.5. METADATA Response . . . . . . . . . . . . . . . . . . . . 19
4.5.1. METADATA response with attributes and values . . . . . 19
4.5.2. Unsolicited METADATA response without attributes
and values . . . . . . . . . . . . . . . . . . . . . . 20
5. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 21
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
6.1. Entry and Attribute Registration Template . . . . . . . . 23
6.2. Server Entry Registrations . . . . . . . . . . . . . . . . 23
6.2.1. /comment . . . . . . . . . . . . . . . . . . . . . . . 24
6.2.2. /motd . . . . . . . . . . . . . . . . . . . . . . . . 24
6.2.3. /admin . . . . . . . . . . . . . . . . . . . . . . . . 25
6.3. Mailbox Entry Registrations . . . . . . . . . . . . . . . 25
6.3.1. /comment . . . . . . . . . . . . . . . . . . . . . . . 25
6.3.2. /sort . . . . . . . . . . . . . . . . . . . . . . . . 26
6.3.3. /thread . . . . . . . . . . . . . . . . . . . . . . . 26
6.3.4. /check . . . . . . . . . . . . . . . . . . . . . . . . 27
6.3.5. /checkperiod . . . . . . . . . . . . . . . . . . . . . 27
6.4. Attribute Registrations . . . . . . . . . . . . . . . . . 27
6.4.1. value . . . . . . . . . . . . . . . . . . . . . . . . 28
6.4.2. size . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.5. LISTEXT Registration . . . . . . . . . . . . . . . . . . . 28
7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.1. Normative References . . . . . . . . . . . . . . . . . . . 29
8.2. Informative References . . . . . . . . . . . . . . . . . . 30
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 30
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 30
Intellectual Property and Copyright Statements . . . . . . . . . . 31
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1. Introduction and Overview
The METADATA extension is present in any IMAP [RFC3501]
implementation which returns "METADATA" as one of the supported
capabilities in the CAPABILITY command response. The "LISTEXT"
[I-D.ietf-imapext-list-extensions] extension MUST also be present.
The goal of METADATA is to provide a means for clients to set and
retrieve "annotations" or "meta data" on an IMAP server. The
annotations can be associated with specific mailboxes or the server
as a whole.
The METADATA extension adds two new commands and one new untagged
response to the IMAP base protocol. It adds one new LISTEXT
"selection" [I-D.ietf-imapext-list-extensions] option type and one
new LISTEXT "return" [I-D.ietf-imapext-list-extensions] option type.
This extension makes the following changes to the IMAP protocol:
o adds a new SETMETADATA command
o adds a new GETMETADATA command
o adds a new METADATA untagged response
o adds a new METADATA response code
o adds a new METADATA LISTEXT selection option type
o adds a new METADATA LISTEXT return option typer
The data model used in METADATA is exactly the same as that used in
the ANNOTATE [I-D.ietf-imapext-annotate] extension to IMAP. This is
modeled after that of the Application Configuration Access Protocol
[RFC2244] with the exception of inheritance which is not deemed
necessary here.
The rest of this document describes the data model and protocol
changes more rigorously.
2. Conventions Used in This Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Data Model
3.1. Overview
Mailboxes or the server as a whole may have zero or more annotations
associated with them. An annotation contains a uniquely named entry
with a set of uniquely named attributes, each of which has a value.
Annotations can be added to mailboxes when a mailbox name is provided
as the first argument to the new commands, or to the server as a
whole when the empty string is provided as the first argument to the
new commands.
For example, a general comment being added to a mailbox may have an
entry name of "/comment". This entry could include named attributes
such as "value" and "size" etc to represent properties and data
associated with 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 an
annotation, assuming it has sufficient access rights to do so.
3.2. Namespace of entries and attributes
Each annotation has an entry that 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 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.
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
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is strongly discouraged.
This specification defines an initial set of entry and attribute
names available for use with mailbox and server annotations. In
addition an extension mechanism is described to allow additional
names to be added for extensibility.
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.
3.2.1.1. Server Entries
These entries are used when the mailbox name argument to the new
SETMATADATA command is the empty string or with the new GETMETADATA
command.
/comment
Defines a comment or note associated with the server.
/motd
Defines a "message of the day" for the server. This entry is
always read-only - clients cannot change it.
/admin
Indicates a method for contacting the server administrator. This
may be a URI (e.g. a mailto URL) or other contact information,
such as a telephone number. This entry is always read-only -
clients cannot change it.
/vendor/<vendor-token>
Defines the top-level of entries associated with the server as
created by a particular product of some vendor. This entry can be
used by vendors to provide server or client specific annotations.
The vendor-token MUST be registered with IANA, using the ACAP
[RFC2244] vendor subtree registry.
3.2.1.2. Mailbox Entries
These entries are used when the mailbox name argument to the new
SETMETADATA command is not the empty string, or with the new LISTEXT
selection option type.
/comment
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Defines a comment or note associated with a mailbox.
/sort
Defines the default sort criteria [I-D.ietf-imapext-sort] to use
when first displaying the mailbox contents to the user, or NIL if
sorting is not required.
/thread
Defines the default thread criteria [I-D.ietf-imapext-sort] to use
when first displaying the mailbox contents to the user, or NIL if
threading is not required. If both sort and thread are not NIL,
then threading should take precedence over sorting.
/check
Boolean value "true" or "false" that indicates whether this
mailbox should be checked at regular intervals by the client. The
interval in minutes is specified by the /checkperiod entry.
/checkperiod
Numeric value indicating a period of minutes that the client uses
to determine the interval of regular 'new mail' checks for the
corresponding mailbox.
/vendor/<vendor-token>
Defines the top-level of entries associated with a specific
mailbox 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, using
the ACAP [RFC2244] vendor subtree registry.
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
which maps to private and shared versions of the entry. Retrieving
an annotation without using either suffix includes both. The client
MUST specify either a ".priv" or ".shared" suffix when setting an
annotation.
value
A string or binary data representing the value of the annotation.
To delete an annotation, the client can store "NIL" into 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
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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 etc), 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.
3.3. Private versus Shared and Access Control
As discussed in the ANNOTATE [I-D.ietf-imapext-annotate] extension
there is a need to support both private and shared annotations. This
document adopts the scheme used in [I-D.ietf-imapext-annotate] that
adds two standard suffixes for all attributes: ".shared" and ".priv".
A GETMETADATA or extended LIST command which specifies neither uses
both. SETMETADATA commands MUST explicitly use .priv or .shared
suffixes.
A user can only set and retrieve private or shared annotations on a
mailbox which is returned to them via a LIST or LSUB command,
irrespective of whether they have read or write access to the actual
message content of the mailbox. If the client attempts to set or
retrieve annotations on other mailboxes, the server MUST respond with
a NO response.
If the METADATA extension is present, support for shared annotations
is REQUIRED, whilst support for private annotations is OPTIONAL.
This recognizes the fact that support for private annotations may
introduce significantly more 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
METADATA extension MUST handle both shared and private annotations.
4. IMAP Protocol Changes
4.1. General Considerations
The new SETMETADATA command and the METADATA response each have a
mailbox name argument, indicating that the annotations being referred
to are attached to the specified mailbox. An empty string can be
used for the mailbox name to signify server annotations.
Both "*" and "%" list wildcard characters MAY be used in the mailbox
name argument in the SETMETADATA command to match all possible
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occurrences of a mailbox name pattern. However, "*" or "%" by
themselves MUST NOT match the empty string (server) entries. Server
entries can only be accessed by explicitly using the empty string as
the mailbox name.
Servers SHOULD ensure that mailbox annotations are automatically
moved when the mailbox they refer to is renamed, i.e. the annotations
follow the mailbox. Servers SHOULD delete annotations for a mailbox
when the mailbox is deleted, so that a mailbox created with the same
name as a previously existing mailbox does not inherit the old
mailbox annotations. Servers SHOULD allow annotations on all 'types'
of mailbox, including ones reporting \Noselect for their LIST
response. Servers can implicitly remove \Noselect mailboxes when all
child mailboxes are removed, and as such any annotations associated
with the \Noselect mailbox SHOULD be removed.
The server is allowed to impose limitations on the size of any one
annotation or the total number of annotations for a single mailbox or
for the server as a whole. However, the server MUST accept a minimum
annotation data size of at least 1024 bytes, and a minimum annotation
count per server or mailbox of at least 10.
4.2. GETMETADATA Command
This extension adds the GETMETADATA command. This allows clients to
retrieve server annotations. Mailbox annotations are retrieved via
the extended LIST command described in the next section.
This command is only available in authenticated or selected state
[RFC3501].
Arguments: entry-specifier
attribute-specifier
Responses: required METADATA response
Result: OK - command completed
NO - command failure: can't access annotations on
the server
BAD - command unknown or arguments invalid
Example:
C: a GETMETADATA /comment value.priv
S: * METADATA /comment (value.priv "My comment")
S: a OK GETMETADATA complete
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In the above example, the contents of the "value.priv" attribute
for the "/comment" server entry is requested by the client and
returned by the server.
"*" and "%" wildcard characters can be used in the entry specifier to
match one or more characters at that position, with the exception
that "%" does not match the "/" hierarchy delimiter. Thus an entry
specifier of "/%" would match entries such as "/comment" and
"/version", but not "/comment/note".
Example:
C: a GETMETADATA /* value.priv
S: * METADATA /comment (value.priv "My comment")
/version (value.priv "1.1")
/motd/today (value.priv "Closed at 1 pm")
S: a OK GETMETADATA complete
In the above example, the contents of the "value.priv" attributes
for any server entries are requested by the client and returned by
the server.
Example:
C: a GETMETADATA /% value
S: * METADATA /comment (value.priv "My comment")
(value.shared "Your comment")
/motd (value.priv "Its sunny outside!"
(value.shared "Today is a Holiday")
S: a OK GETMETADATA complete
In the above example, the contents of the "value" attributes for
server entries at the top level of the entry hierarchy only, are
requested by the client and returned by the server. Both the
.priv and .shared values are returned, as neither were explicitly
requested.
Entry and attribute specifiers can be lists of atomic specifiers, so
that multiple items of each type may be returned in a single
GETMETADATA command.
Example:
C: a GETMETADATA (/comment /motd) value.priv
S: * METADATA /comment (value.priv "My comment")
/motd (value.priv "Its sunny outside!")
S: a OK GETMETADATA complete
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In the above example, the contents of the "value.priv" attributes
for the two server entries "/comment" and "/motd" are requested by
the client and returned by the server.
Example:
C: a GETMETADATA /comment (value.priv
size.priv)
S: * METADATA /comment (value.priv "My comment"
size.priv "1234")
S: a OK GETMETADATA complete
In the above example, the contents of the "value.priv" and
"size.priv" attributes for the "/comment" server entry are
requested by the client and returned by the server.
4.3. Extended LIST Command Extensions
This extension adds the METADATA LIST command selection and return
option types, extending the LISTEXT extension. This allows clients
to retrieve mailbox annotations.
The LISTEXT "METADATA" selection option type is used to request that
the extended LIST command match mailboxes which have an annotation
with a specific entry and value. It can also be used to test for the
existence of a particular annotation entry on a mailbox. This
selection option takes one or more entry/attribute/value triples to
use as tests. A mailbox matches this criteria if it has an entry,
attribute and value matching the ones specified. In the case of
multiple criteria being specified, mailbox MUST only match when all
criteria match ("and" operation). To test for the existence of an
entry, a test for the attribute "value" with the empty string "" as
the value argument can be used. To test for the absence of an entry,
a test for the attribute "value" with NIL as the value argument can
be used. If the COMPARATOR [I-D.ietf-imapext-i18n] extension is
present, then the active comparator MUST be used when doing text
comparisons of the value. Clients SHOULD only use entries defined
with a "text" Content-Type in the selection option arguments.
The LISTEXT "METADATA" return option type is used to request that the
extended LIST command return specific annotation entries for each
mailbox returned in the LIST responses. A list of entries and
attributes to return can be specified in a manner similar to the
GETMETADATA command.
Example:
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C: a LIST "" "INBOX" RETURN (METADATA /comment value.priv)
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment"))
S: a OK LIST complete
In the above example, the contents of the "value.priv" attribute
for the "/comment" entry for the mailbox INBOX is requested by the
client and returned by the server.
"*" and "%" wildcard characters can be used in the entry specifier to
match one or more characters at that position, with the exception
that "%" does not match the "/" hierarchy delimiter. Thus an entry
specifier of "/%" would match entries such as "/comment" and
"/version", but not "/comment/note".
Example:
C: a LIST "" "INBOX" RETURN (METADATA /* value.priv)
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment")
/version (value.priv "1.1")
/motd/today (value.priv "Closed at 1 pm"))
S: a OK LIST complete
In the above example, the contents of the "value.priv" attributes
for any entries for the mailbox INBOX are requested by the client
and returned by the server.
Example:
C: a LIST "" "INBOX" RETURN (METADATA /% value)
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment")
(value.shared "Your comment")
/motd (value.priv "Its sunny outside!"
(value.shared "Today is a Holiday"))
S: a OK LIST complete
In the above example, the contents of the "value" attributes for
entries for the mailbox INBOX at the top level of the entry
hierarchy only, are requested by the client and returned by the
server. Both the .priv and .shared values are returned, as
neither were explicitly requested.
Entry and attribute specifiers can be lists of atomic specifiers, so
that multiple items of each type may be returned in a single LIST
command.
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Example:
C: a LIST "" "INBOX" RETURN (METADATA (/comment /motd)
value.priv)
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment")
/motd (value.priv "Its sunny outside!"))
S: a OK LIST complete
In the above example, the contents of the "value.priv" attributes
for the two entries "/comment" and "/motd" for the mailbox INBOX
are requested by the client and returned by the server.
Example:
C: a LIST "" "INBOX" RETURN (METADATA /comment
(value.priv size.priv))
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment"
size.priv "1234"))
S: a OK LIST complete
In the above example, the contents of the "value.priv" and
"size.priv" attributes for the "/comment" entry for the mailbox
INBOX are requested by the client and returned by the server.
Example:
C: a LIST "" ("INBOX" "FOOBOX" "BARBOX") RETURN
(METADATA /comment value.priv)
S: * LIST "/" "INBOX"
(METADATA /comment (value.priv "My comment"))
S: * LIST "/" "FOOBOX"
(METADATA /comment (value.priv "Another comment"))
S: * LIST "/" "BARBOX"
(METADATA /comment (value.priv NIL))
S: a OK LIST complete
In the above example, the contents of the "value.priv" attribute
for the "/comment" entry for the mailboxes INBOX, FOOBOX and
BARBOX are requested by the client and returned by the server.
Note that the mailbox BARBOX does not contain the entry, hence NIL
is returned for the attribute value.
Example:
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C: a LIST (METADATA ("/comment" "value" "comm")
"" "*"
S: * LIST () "/" "INBOX"
S: * LIST (\NoInferiors) "/" "FOOBOX"
S: a OK LIST complete
In the above example, the client requests that any mailbox in the
entire hierarchy containing the text "comm" in any "value"
attribute of the "/comment" entry be returned. Two mailboxes are
returned in separate responses. Note that the client did not ask
for annotations to be returned in the responses.
Example:
C: a LIST (METADATA ("/comment" "value" "")
"" "*"
S: * LIST () "/" "INBOX"
S: * LIST (\NoInferiors) "/" "FOOBOX"
S: a OK LIST complete
In the above example, the client requests that any mailbox in the
entire hierarchy containing the "/comment" entry be returned. Two
mailboxes are returned in separate responses. Note that the
client did not ask for annotations to be returned in the
responses.
Example:
C: a LIST (METADATA ("/comment" "value" NIL)
"" "*"
S: * LIST (\NoInferiors) "/" "BARBOX"
S: a OK LIST complete
In the above example, the client requests that any mailbox in the
entire hierarchy that does not have a "/comment" entry be
returned. One mailbox is returned in a response. Note that the
client did not ask for annotations to be returned in the
responses.
Example:
C: a LIST (METADATA ("/comment" "value" "comm")
"" "*" RETURN (METADATA /comment size.priv)
S: * LIST "/" "INBOX"
(METADATA /comment (size.priv "10"))
S: * LIST "/" "FOOBOX"
(METADATA /comment (size.priv "15"))
S: a OK LIST complete
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In the above example, the client requests that any mailbox in the
entire hierarchy containing the text "comm" in any "value"
attribute of the "/comment" entry be returned. Two mailboxes are
returned in separate responses. The client also asked for
annotations to be returned in the responses.
4.3.1. Unsolicited LIST response
Servers SHOULD send unsolicited LIST responses if mailbox annotations
are changed by a third-party, allowing servers to keep clients
updated with changes. Unsolicited mailbox annotations MUST only be
returned for the currently selected mailbox.
Unsolicited LIST responses MUST only contain entry names, not the
attributes and values. If the client wants to update any cached
values it must explicitly retrieve those using a LIST command.
The LIST response can contain multiple entries in a single response,
but the server is free to return multiple responses for each entry or
group of entries if it desires.
Example:
C: a NOOP
S: * LIST "/" "INBOX" (METADATA /comment)
S: a OK NOOP complete
In the above example, the server sends an unsolicited LIST
response indicating that the "/comment" entry of the mailbox
"INBOX" has been changed.
4.4. SETMETADATA Command
This extension adds the SETMETADATA command. This allows clients to
set annotations.
This command is only available in authenticated or selected state
[RFC3501].
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Arguments: mailbox-name
entry
attribute-value
list of entry, attribute-values
Responses: no specific responses for this command
Result: OK - command completed
NO - command failure: can't set annotations,
or annotation too big or too many
BAD - command unknown or arguments invalid
This command 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 server MAY return a METADATA response containing the updated
annotation data. Clients MUST NOT assume that a METADATA response
will be sent, and MUST assume that if the command succeeds then the
annotation has been changed.
If the server is unable to set an annotation because the size of its
value is too large, the server MUST return a tagged NO response with
a "[METADATA TOOBIG]" response code.
If the server is unable to set a new annotation because the maximum
number of allowed annotations has already been reached, the server
MUST return a tagged NO response with a "[METADATA TOOMANY]" response
code.
If the server is unable to set a new annotation because it does not
support private annotations on one of the specified mailboxes, the
server MUST return a tagged NO response with a "[METADATA NOPRIVATE]"
response code.
If the server is unable to set the annotations for one or more
mailboxes matching the mailbox-name pattern, then the SETMETADATA
command MUST fail and there MUST NOT be any changes to any of the
matching mailboxes, even those for which annotations could have been
changed successfully.
Example:
C: a SETMETADATA INBOX /comment
(value.priv "My new comment")
S: a OK SETMETADATA complete
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In the above example, the entry "/comment" for the mailbox "INBOX"
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 previously exists.
Example:
C: a SETMETADATA INBOX /comment (value.priv NIL)
S: a OK SETMETADATA complete
In the above example, the private "value" attribute of the entry
"/comment" is removed from the mailbox "INBOX".
Annotations on multiple mailboxes can be set in a single SETMETADATA
command by using a wildcard specification for the mailbox name.
Example:
C: a SETMETADATA INBOX.% /comment
(value.priv "My new comment")
S: a OK SETMETADATA complete
In the above example, the entry "/comment" for all mailboxes at
the top-level of the "INBOX" hierarchy are created (if not already
present) and the private attribute "value" are created
respectively for each entry if not already present, or replaced if
they previously existed.
Multiple entries can be set in a single SETMETADATA command by
listing entry-attribute-value pairs in the list.
Example:
C: a SETMETADATA INBOX (/comment
(value.priv "My new comment")
/thread
(value.priv "REFERENCES ALL"))
S: a OK SETMETADATA complete
In the above example, the entries "/comment" and "/thread" for the
mailbox "INBOX" are created (if not already present) and the
"value.priv" attributes are created respectively for each entry if
not already present, or replaced if they previously existed.
Multiple attributes can be set in a single SETMETADATA command by
listing multiple attribute-value pairs in the entry list.
Example:
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C: a SETMETADATA INBOX /comment
(value.priv "My new comment"
value.shared "foo's bar")
S: a OK SETMETADATA complete
In the above example, the entry "/comment" for the mailbox "INBOX"
is created (if not already present) and the attributes
"value.priv" and "value.shared" are created if not already
present, or replaced if they previously existed.
Example:
C: a SETMETADATA INBOX /comment
(value.priv "My new comment")
S: a NO [METADATA TOOMANY] SETMETADATA failed
In the above example, the server is unable to set the requested
(new) annotation as it has reached the limit on the number of
annotations it can support on the specified mailbox.
4.5. METADATA Response
The METADATA response displays results of a GETMETADATA command, or
can be returned as an unsolicited response at anytime by the server
in response to a change in a server annotation.
Servers SHOULD send unsolicited METADATA responses if server
annotations are changed by a third-party, allowing servers to keep
clients updated with changes.
Unsolicited METADATA responses MUST only contain entry names, not the
attributes and values. If the client wants to update any cached
values it must explicitly retrieve those using a GETMETADATA command.
The METADATA response can contain multiple entries in a single
response, but the server is free to return multiple responses for
each entry or group of entries if it desires.
This response is only available in authenticated or selected state
[RFC3501].
4.5.1. METADATA response with attributes and values
The response consists of a list of entries each of which has a list
of attribute-value pairs.
Example:
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C: a GETMETADATA /comment value.priv
S: * METADATA /comment (value.priv "My comment")
S: a OK GETMETADATA complete
In the above example, a single entry with a single attribute-value
pair is returned by the server.
Example:
C: a GETMETADATA (/comment /motd) value.priv
S: * METADATA /comment (value.priv "My comment")
/motd (value.priv "Its sunny outside!")
S: a OK GETMETADATA complete
In the above example, two entries each with a single attribute-
value pair is returned by the server.
Example:
C: a GETMETADATA (/comment /motd) value.priv
S: * METADATA /comment (value.priv "My comment")
S: * METADATA /motd (value.priv "Its sunny outside!")
S: a OK GETMETADATA complete
In the above example, the server returns two separate responses
for each of the two entries requested.
Example:
C: a GETMETADATA /comment (value.priv size.priv)
S: * METADATA /comment (value.priv "My comment"
size.priv "10")
S: a OK GETMETADATA complete
In the above example, a single entry with two attribute-value
pairs is returned by the server.
4.5.2. Unsolicited METADATA response without attributes and values
The response consists of a parenthesized list of entries, each of
which have changed on the server.
Example:
C: a NOOP
S: * METADATA (/comment)
S: a OK NOOP complete
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In the above example, the server indicates that the "/comment"
server entry has been changed.
Example:
C: a NOOP
S: * METADATA (/comment /motd)
S: a OK NOOP complete
In the above example, the server indicates a change to two server
entries.
5. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [RFC2234].
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.
annotate-data = "METADATA" SP entry-list
att-select = "value" / "value.priv" / "value.shared"
; the only attributes that can be selected
att-value = attrib SP value
attrib = astring
; dot-separated attribute name
; MUST NOT contain "*" or "%"
attribs = attrib / "(" attrib *(SP attrib) ")"
; one or more attribute specifiers
capability =/ "METADATA"
; defines the capability for this extension
command-auth =/ setmetadata / getmetadata
; adds to original IMAP command
entries = entry-match /
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"(" entry-match *(SP entry-match) ")"
; entry specifiers that can include wildcards
entry = astring
; slash-separated path to entry
; MUST NOT contain "*" or "%"
entry-att = entry SP "(" att-value *(SP att-value) ")"
entry-list = entry-att *(SP entry-att) /
"(" entry *(SP entry) ")"
; entry attribute-value pairs list for
; GETMETADATA response, or
; parenthesised entry list for unsolicited
; notification of annotation changes
entry-match = list-mailbox
; slash-separated path to entry
; MAY contain "*" or "%" for use as wildcards
getmetadata = "GETMETADATA" SP entries SP attribs
list-select-base-opt =/ "METADATA" SP
"(" list-select-metadata
*(SP list-select-metadata) ")"
; adds a new selection option type to
; LISTEXT. When evaluating multiple entry,
; attribute, value combinations, a match to
; a mailbox must occur when all items match.
list-select-metadata = entry-match SP att-select SP value
; value set to the empty string means match
; if that entry and attribute exist.
; value set to NIL means match if that entry
; and attribute do not exist.
response-payload =/ annotate-data
; adds to original IMAP data responses
resp-text-code =/ "METADATA" SP ("TOOBIG" / "TOOMANY" /
"NOPRIVATE")
; new response codes for SETMETADATA
; failures
setmetadata = "SETMETADATA" SP list-mailbox
SP setentryatt
; empty string for list-mailbox implies
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; server annotation.
setentryatt = entry-att / "(" entry-att *(SP entry-att) ")"
value = nstring / literal8
6. IANA Considerations
Entry names MUST be specified in a standards track or IESG approved
experimental RFC, or fall under the vendor namespace. 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 METADATA Registration
Please register the following IMAP METADATA item:
[ ] Entry [ ] Attribute
[ ] Mailbox [ ] Server
Name: ______________________________
Description: _______________________
____________________________________
____________________________________
Content-type: ____________________
Contact person: ____________________
email: ____________________
6.2. Server Entry Registrations
The following templates specify the IANA registrations of annotation
entries specified in this document.
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6.2.1. /comment
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[ ] Mailbox [x] Server
Name: /comment
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.2.2. /motd
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[ ] Mailbox [x] Server
Name: /motd
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
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6.2.3. /admin
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[ ] Mailbox [x] Server
Name: /admin
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.3. Mailbox Entry Registrations
The following templates specify the IANA registrations of annotation
entries specified in this document.
6.3.1. /comment
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[x] Mailbox [ ] Server
Name: /comment
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
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6.3.2. /sort
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[x] Mailbox [ ] Server
Name: /sort
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.3.3. /thread
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[x] Mailbox [ ] Server
Name: /thread
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
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6.3.4. /check
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[x] Mailbox [ ] Server
Name: /check
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.3.5. /checkperiod
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[x] Entry [ ] Attribute
[x] Mailbox [ ] Server
Name: /checkperiod
Description: Defined in IMAP METADATA extension document.
Content-type: text/plain; charset=utf-8
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.4. Attribute Registrations
The following templates specify the IANA registrations of annotation
attributes specified in this document.
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6.4.1. value
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[ ] Entry [x] Attribute
[ ] Mailbox [ ] Server
Name: value
Description: Defined in IMAP METADATA extension document.
Content-type: -
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.4.2. size
To: iana@iana.org
Subject: IMAP METADATA Registration
Please register the following IMAP METADATA item:
[ ] Entry [x] Attribute
[ ] Mailbox [ ] Server
Name: size
Description: Defined in IMAP METADATA extension document.
Content-type: -
Contact person: Cyrus Daboo
email: cyrus@daboo.name
6.5. LISTEXT Registration
TBD: registration for select and return options.
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7. Security Considerations
Annotations whose values are intended to remain private MUST use
.priv values, and not .shared values which may be accessible to other
users.
Excluding the above issues the METADATA extension does not raise any
security considerations that are not present in the base IMAP
protocol, and these issues are discussed in [RFC3501].
8. References
8.1. Normative References
[I-D.ietf-imapext-i18n]
Newman, C., "Internet Message Access Protocol
Internationalization", draft-ietf-imapext-i18n-06 (work in
progress), March 2006.
[I-D.ietf-imapext-list-extensions]
Leiba, B. and A. Melnikov, "IMAP4 LIST Command
Extensions", draft-ietf-imapext-list-extensions-18 (work
in progress), September 2006.
[I-D.ietf-imapext-sort]
Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS
PROTOCOL - SORT AND THREAD EXTENSION",
draft-ietf-imapext-sort-17 (work in progress), May 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 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.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC4466] Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
ABNF", RFC 4466, April 2006.
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8.2. Informative References
[I-D.ietf-imapext-annotate]
Gellens, R. and C. Daboo, "IMAP ANNOTATE Extension",
draft-ietf-imapext-annotate-15 (work in progress),
March 2006.
Appendix A. Acknowledgments
The ideas expressed in this document are based on the message
annotation document that was co-authored by Randall Gellens. The
participants of the IMAPext working group made significant
contributions to this work.
Author's Address
Cyrus Daboo
Apple Computer, Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
Email: cyrus@daboo.name
URI: http://www.apple.com/
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Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Acknowledgment
Funding for the RFC Editor function is provided by the IETF
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