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rfc:rfc5259

Network Working Group A. Melnikov, Ed. Request for Comments: 5259 Isode Ltd Category: Standards Track P. Coates, Ed.

                                                      Sun Microsystems
                                                             July 2008
        Internet Message Access Protocol - CONVERT Extension

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 CONVERT defines extensions to IMAP allowing clients to request
 adaptation and/or transcoding of attachments.  Clients can specify
 the conversion details or allow servers to decide based on knowledge
 of client capabilities, on user or administrator preferences, or on
 server settings.

Melnikov & Coates Standards Track [Page 1] RFC 5259 IMAP CONVERT extension July 2008

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
 3.  Relation with Other IMAP Specifications  . . . . . . . . . . .  4
   3.1.  CAPABILITY Response  . . . . . . . . . . . . . . . . . . .  4
 4.  Scope of Conversions . . . . . . . . . . . . . . . . . . . . .  4
 5.  Discovery of Available Conversions . . . . . . . . . . . . . .  4
   5.1.  CONVERSIONS Command  . . . . . . . . . . . . . . . . . . .  4
   5.2.  CONVERSION Response  . . . . . . . . . . . . . . . . . . .  6
 6.  CONVERT and UID CONVERT Commands . . . . . . . . . . . . . . .  6
 7.  CONVERT Conversion Parameters  . . . . . . . . . . . . . . . . 12
   7.1.  Mandatory-to-Implement Conversions and Conversion
         Parameters . . . . . . . . . . . . . . . . . . . . . . . . 12
   7.2.  Additional Features for Mobile Usage . . . . . . . . . . . 13
 8.  Request/Response Data Items to CONVERT/UID CONVERT Commands  . 14
   8.1.  CONVERTED Untagged Response  . . . . . . . . . . . . . . . 14
   8.2.  BODYPARTSTRUCTURE CONVERT Request and Response Item  . . . 14
   8.3.  BINARY.SIZE CONVERT Request and Response Item  . . . . . . 15
   8.4.  AVAILABLECONVERSIONS CONVERT Request and Response Item . . 16
   8.5.  Implementation Considerations  . . . . . . . . . . . . . . 17
 9.  Status Responses and Response Code Extensions  . . . . . . . . 17
 10. Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . . . 20
 11. Manageability Considerations . . . . . . . . . . . . . . . . . 24
 12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
   12.1. Registration of unknown-character-replacement Media
         Type Parameter . . . . . . . . . . . . . . . . . . . . . . 25
 13. Security Considerations  . . . . . . . . . . . . . . . . . . . 26
 14. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27
 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
   15.1. Normative References . . . . . . . . . . . . . . . . . . . 28
   15.2. Informative References . . . . . . . . . . . . . . . . . . 29

Melnikov & Coates Standards Track [Page 2] RFC 5259 IMAP CONVERT extension July 2008

1. Introduction

 This document defines the CONVERT extension to IMAP4 [RFC3501].
 CONVERT provides adaptation and transcoding of body parts as needed
 by the client.  Conversion (adaptation, transcoding) may be requested
 by the client and performed by the server on a best effort basis or,
 when requested by the client, decided by the server based on the
 server's knowledge of the client capabilities, user or administrator
 preferences, or server settings.
 This extension is primarily intended to be useful to mobile clients.
 It satisfies requirements specified in [OMA-ME-RD].
 A server that supports CONVERT can convert body parts to other
 formats to be viewed (for example) on a mobile device.  The client
 can explicitly request a particular conversion or ask the server to
 select the best available conversion.  When allowed by the client,
 the server determines how to convert based on its own strategy (e.g.,
 based on knowledge of the client as discussed hereafter).  If the
 server knows the characteristics of the device (out of scope for
 CONVERT) or can determine them (for example, using a conversion
 parameter containing device type), converted body parts can also be
 optimized for capabilities of the device (e.g., form factor of
 pictures).  The client is able to control conversions using optional
 conversion (also referred to as "transcoding" in this document)
 parameters.
 This document relies on the registry of conversion parameters
 established by [MEDIAFEAT-REG].  The registry can be used to discover
 the underlying legal values that these parameters can take.
 Additional conversion parameters, such as those defined by [OMA-STI],
 are expected to be registered in the future.

2. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].
 In examples, "C:" and "S:" indicate lines sent by the client and
 server, respectively.  If a single "C:" or "S:" label applies to
 multiple lines, then the line breaks between those lines are for
 editorial clarity only and are not part of the actual protocol
 exchange.  The five characters [...] mean that something has been
 elided.

Melnikov & Coates Standards Track [Page 3] RFC 5259 IMAP CONVERT extension July 2008

 When describing the general syntax, some definitions are omitted as
 they are defined in [RFC3501].  In particular, the term "session" is
 used in this document as defined in Section 1.2 of [RFC3501].

3. Relation with Other IMAP Specifications

 Conversion of attachments during streaming is out of scope for the
 CONVERT extension and is described in a separate Lemonade WG document
 [LEM-STREAMING].
 A server claiming compliance with this specification MUST support the
 IMAP Binary specification [RFC3516].

3.1. CAPABILITY Response

 A server that supports the CONVERT extension MUST return "CONVERT"
 and "BINARY" in the CAPABILITY response or response code.  (Client
 and server authors are reminded that the order of tokens returned in
 the CAPABILITY response or response code is arbitrary.)
    Example: A server that implements CONVERT.
       C: a000 CAPABILITY
       S: * CAPABILITY IMAP4rev1 CONVERT BINARY [...]
       S: a000 OK CAPABILITY completed

4. Scope of Conversions

 Conversions only affect what is sent to the client; the original data
 in the message store MUST NOT be altered.  This document does not
 specify how the server performs conversions.
 Note: The requirement that original data be unaltered allows such
 data to remain accessible by other clients, permits replies or
 forwards of the original documents, permits signature verification
 (the converted body parts are not likely to contain any signatures),
 and preserves BODYSTRUCTURE and related information.

5. Discovery of Available Conversions

5.1. CONVERSIONS Command

 Arguments: source MIME type
            target MIME type
 Responses: untagged responses: CONVERSION

Melnikov & Coates Standards Track [Page 4] RFC 5259 IMAP CONVERT extension July 2008

 Result:    OK - CONVERSIONS command completed
            BAD - unrecognized syntax of an argument, unexpected extra
                  argument, missing argument, etc.
 The CONVERSIONS command is allowed in Authenticated and Selected IMAP
 states.
 The first parameter to the CONVERSIONS command is a source MIME type,
 the second parameter is the target MIME type.  Both parameters are
 partially (e.g., "text/*") or completely ("*") wildcardable.
 Conversions matching the source/target pair and their associated
 conversion parameters are returned in untagged CONVERSION responses.
 If source/target doesn't match any conversion supported by the
 server, no CONVERSION response is returned.
 Examples:
 For conversion information from GIF to JPEG image format (no untagged
 CONVERSION response would be returned if no conversion is possible):
     C: a CONVERSIONS "image/gif" "image/jpeg"
     S: * CONVERSION "image/gif" "image/jpeg" ("pix-y" "pix-x"
         "image-interleave")
     S: a OK CONVERSIONS completed
 For conversion information from GIF image format to anything:
     C: b CONVERSIONS "image/gif" "*"
     S: * CONVERSION "image/gif" "image/jpeg" ("pix-y" "pix-x"
         "image-interleave")
     S: * CONVERSION "image/gif" "image/png" ([...])
     [...]
     S: b OK CONVERSIONS completed
 For conversion of anything to JPEG:
     C: c CONVERSIONS "*" "image/jpeg"
     S: * CONVERSION "image/gif" "image/jpeg" ("pix-y" "pix-x"
         "image-interleave")
     S: * CONVERSION "image/png" "image/jpeg" (...)
     [...]
     S: c OK CONVERSIONS completed
 For conversions from all image formats to all text formats, the
 client can issue the following command:
     C: d CONVERSIONS "image/*" "text/*"

Melnikov & Coates Standards Track [Page 5] RFC 5259 IMAP CONVERT extension July 2008

5.2. CONVERSION Response

 Contents:  source MIME type
            target MIME type
            optional list of supported conversion parameters
 As a result of executing a CONVERSIONS command, the server can return
 one or more CONVERSION responses.  Each CONVERSION response specifies
 which source MIME type can be converted to the target MIME type, and
 also lists supported conversion parameters.

6. CONVERT and UID CONVERT Commands

 Arguments: sequence set
            conversion parameters
            CONVERT data item names
 Responses: untagged responses: CONVERTED
 Result:    OK - convert completed
            NO - convert error: can't fetch and/or convert that data
            BAD - unrecognized syntax of an argument, unexpected extra
                  argument, missing argument, etc.
 The CONVERT extension defines CONVERT and UID CONVERT commands that
 are used to transcode the media type of a MIME part into another
 media type, and/or the same media type with different encoding
 parameters.  These commands are structured and behave similarly to
 FETCH/UID FETCH commands as extended by [RFC3516]:
 o  A successful CONVERT/UID CONVERT command results in one or more
    untagged CONVERTED responses (one per message).  They are similar
    to the untagged FETCH responses.  Note that a single CONVERT/ UID
    CONVERT command can only perform a single type of conversion as
    defined by the conversion parameters.  A client that needs to
    perform multiple different conversions needs to issue multiple
    CONVERT/UID CONVERT commands.  Such a client MAY pipeline them.
 o  BINARY[...] data item requests conversion of a body part or of the
    whole message according to conversion parameters and requests that
    the converted message/body part be returned as binary.
 o  BINARY.SIZE data item is similar to RFC822.SIZE, but it requests
    size of a converted body part/message.
 o  BODYPARTSTRUCTURE data item is similar to BODYSTRUCTURE FETCH data
    item, but it returns the MIME structure of the converted body
    part.

Melnikov & Coates Standards Track [Page 6] RFC 5259 IMAP CONVERT extension July 2008

 o  BODY[...HEADER] encoded words in the requested headers are
    converted to the specified charset.  The CHARSET parameter is
    REQUIRED for this conversion.
 o  BODY[...MIME] encoded words in the requested headers are converted
    to the specified charset.  The CHARSET parameter is REQUIRED for
    this conversion.
 o  AVAILABLECONVERSIONS data item requests the list of target MIME
    types the specified body part (or the whole message) can be
    converted to.
 The CONVERT extension also adds one new response code.  See Section 9
 for more details.
 Typically clients will request conversion of leaf body parts.  In
 addition to support of leaf body part conversion, servers MAY offer
 conversion of non-leaf body parts (e.g., conversion from multipart/
 related).
 Instead of specifying the exact target MIME media type the client
 wants to convert to, the client MAY use a special marker NIL (also
 known as "default conversion") to request the server to pick a
 suitable target media type.  This document doesn't describe how
 exactly the server makes such a choice; however, some basic
 guidelines are described in this paragraph.  If the server knows
 characteristics of the device using an in-band (such as device type
 specified in a conversion parameter) or an out-of-band mechanism,
 then it should convert the request body part to a media type the
 device is likely to support and display/play successfully.  Unless
 specifically overridden by a conversion parameter, the server MAY
 also remove any unnecessary detail that exceeds the capabilities of
 the device (e.g., scaling images to just fit on the device's screen).
 In the absence of any in-band or out-of-band mechanism for
 determining device characteristics, the server should convert the
 request body part to the most standard or widely deployed media type
 available in that media category, for example, to convert to text/
 plain, image/jpeg.  In such case, the server should minimize quality
 loss.  Servers are REQUIRED to support "default conversion" requests.
 Server implementations that support conversions to multiple target
 MIME types SHOULD make the default conversion configurable.  Clients
 SHOULD avoid using the default conversion unless they provided a way
 (in-band or out-band) to signal their capabilities to the server, as
 there is no guaranty that the server would guess their capability
 correctly.  Client implementors should consider using
 AVAILABLECONVERSIONS CONVERT data item or CONVERSIONS command instead
 of the default conversion.

Melnikov & Coates Standards Track [Page 7] RFC 5259 IMAP CONVERT extension July 2008

 CONVERT's command syntax is modeled after the FETCH command syntax in
 [RFC3501], as extended by [RFC3516].  CONVERT data items are
 generally structured as:
     BINARY[section-part]<partial>
     BINARY.SIZE[section-part]
     BODYPARTSTRUCTURE[section-part]
     BODY[HEADER]
     BODY[section-part.HEADER]
     BODY[section-part.MIME]
     AVAILABLECONVERSIONS[section-part]
 The semantics of a partial CONVERT BINARY[...] command is the same as
 for a partial FETCH BODY[...] command, with the exception that the
 <partial> arguments refer to the TRANSCODED and DECODED section data.
 Note that unlike the FETCH command, the CONVERT command never sets
 the \Seen flag on converted messages.  A client wishing to mark a
 message with the \Seen flag would need to issue a STORE command
 (possibly pipelined with the CONVERT request) to do that.
 The UID CONVERT command is different from the CONVERT command in the
 same way as the UID FETCH command is different from the FETCH
 command:
 o  UID CONVERT takes as a parameter a sequence of UIDs instead of a
    sequence of message numbers.
 o  UID CONVERT command MUST result in the UID data item in a
    corresponding CONVERTED response.
 o  An EXPUNGE response MUST NOT be sent while responding to a CONVERT
    command.  This rule is necessary to prevent a loss of
    synchronization of message sequence numbers between client and
    server.  Note that an EXPUNGE response MAY be sent during a UID
    CONVERT command.

Melnikov & Coates Standards Track [Page 8] RFC 5259 IMAP CONVERT extension July 2008

 Example: The client fetches body part section 3 in the message with
 the message sequence number of 2 and asks to have that attachment
 converted to pdf format.
   C: a001 CONVERT 2 ("APPLICATION/PDF") BINARY[3]
   S: * 2 CONVERTED (TAG "a001") (BINARY[3] {2135}
      <the document in .pdf format>
      )
   S: a001 OK CONVERT COMPLETED
 Example: The client requests for conversion of a text/html body part
 to text/plain and asks for a charset of us-ascii.  The server cannot
 respect the charset conversion request because there are non-us-ascii
 characters in the text/html body part, so it fails the request by
 returning an ERROR phrase in place of the converted data (see
 Section 9).
   C: b001 CONVERT 2 ("text/plain" ("charset" "us-ascii")) BINARY[3]
   S: * 2 CONVERTED (tag "b001") (BINARY[3]
       (ERROR "Source text has non us-ascii" BADPARAMETERS
       "text/html" "text/plain" ("charset" "us-ascii")))
   S: b001 NO All conversions failed
 If the client also specified the "unknown-character-replacement"
 conversion parameter (see Section 12.1), the same example can look
 like this:
   C: b001 CONVERT 2 ("text/plain" ("charset" "us-ascii"
       "unknown-character-replacement" "?")) BINARY[3]
   S: * 2 CONVERTED (TAG "b001") (BINARY[3] {2135}
       <the document in text/plain format with us-ascii
        charset>
      )
   S: b001 OK CONVERT COMPLETED
 The server replaced non-us-ascii characters with a us-ascii character
 such as "?".
 Example: The client first requests the converted size of a text/html
 body part converted to text/plain:
   C: c000 CONVERT 2 ("TEXT/PLAIN" ("CHARSET" "us-ascii"))
       BINARY.SIZE[4]
   S: * 2 CONVERTED (TAG "c000") (BINARY.SIZE[4] 3135)
   S: c000 OK CONVERT COMPLETED

Melnikov & Coates Standards Track [Page 9] RFC 5259 IMAP CONVERT extension July 2008

 Later on, the client requests 1000 bytes from the converted body
 part, starting from byte 2001:
   C: c001 CONVERT 2 ("TEXT/PLAIN" ("CHARSET" "us-ascii"))
       BINARY[4]<2001.1000>
   S: * 2 CONVERTED (TAG "c001") (BINARY[4]<2001> {135}
        <bytes 2001 - 2135 of the document in text/plain format>
        )
   S: c001 OK CONVERT COMPLETED
 The server MUST respect the target MIME type and conversion
 parameters specified by the client in the transcoding request.  Note
 that some conversion parameters can restrict what kind of conversion
 is possible, while others can remove some restrictions.
 It is legal for a client to request conversion of a non-leaf body
 part, for example, to request conversion of a multipart/* into a PDF
 document.  However, servers implementing this extension are not
 required to support such conversions.  Servers that support such
 conversions MUST return one or more CONVERSION responses in response
 to a 'CONVERSIONS "multipart/*" "*"' command.  See Section 5.1 for
 more details.
 The client can request header conversions using the BODY[...HEADER]
 CONVERT request, for example
      C: D001 FETCH 2 BODY[HEADER]
      S: * 2 FETCH (BODY[HEADER] {158}
      S: Date: Mon, 20 Apr 2007 20:05:43 +0200
      S: From: Peter <peter@siroe.example.com>
      S: To: Alexey <alexey@siroe.example.com>
      S: Subject: =?KOI8-R?Q?why encode this?=
      S:
      S: )
      S: D001 OK
      C: D002 CONVERT 2 (NIL ("CHARSET" "utf-8")) BODY[HEADER]
      S: * 2 CONVERTED (TAG "d002") (BODY[HEADER] {157}
      S: Date: Mon, 20 Apr 2007 20:05:43 +0200
      S: From: Peter <peter@siroe.example.com>
      S: To: Alexey <alexey@siroe.example.com>
      S: Subject: =?UTF-8?Q?why encode this?=
      S:
      S: )
      S: D002 OK
 Any such request MUST include the CHARSET parameter.  Upon receipt of
 the request, the server MUST decode any encoded words (as described
 in [RFC2047]) in headers and return them re-encoded in the specified

Melnikov & Coates Standards Track [Page 10] RFC 5259 IMAP CONVERT extension July 2008

 charset.  (Note that encoded-words might not be needed if the result
 can be represented entirely in US-ASCII, so the server MAY replace
 the resulting encoded-words with their pure US-ASCII representation.)
 If the server can't decode any particular encoded word, for example,
 if the charset or encoding is not recognized, it MUST leave them as
 is.  Servers SHOULD also support decoding of any parameters as
 described in [RFC2231].  Support for RFC 2231 parameters might
 require reformatting of header fields during conversion.  Consider
 the following
      C: D011 FETCH 3 BODY[1.MIME]
      S: * 3 FETCH (BODY[1.MIME] {118}
      S: Content-Type: text/plain; charset=utf-8;
      S:  foo*0*=utf-8'fr'tr%c0;
      S:  foo*1*(very)=%03s_m%c0;
      S:  foo*2*=(nasty)%09chant
      S:
      S: D011 OK
 The server should preserve the headers during the conversion as much
 as possible.  In case the characters are split (legally!) between
 fragments of an encoded parameter, the server MUST consolidate the
 parameter fragments, and convert, emit, and re-fragment them as
 necessary in order to keep the line length less than 78.  Comments
 embedded like this SHOULD be preserved during conversion, but clients
 MUST gracefully handle the situation where comments are removed
 entirely.  If the comments are preserved, they MAY be moved after the
 parameter.  For example (continuing the previous example):
      C: D012 CONVERT 3 (NIL) BODY[1.MIME]
      S: * 3 CONVERTED (TAG "D012") (BODY[1.MIME] {109}
      S: Content-Type: text/plain; charset=utf-8;
      S:  foo*0*=utf-8'fr'tr%c0%03s_;
      S:  foo*1*=%m%c0%09chant (very)(nasty)
      S:
      S: D012 OK
 No destination MIME type MUST be specified with BODY[HEADER],
 BODY[section.HEADER], or BODY[section.MIME].  That is, BODY[HEADER],
 BODY[section.HEADER], or BODY[section.MIME] can only be used with the
 "default conversion".  When performing these conversions, the server
 SHOULD leave encoded words as encoded words.  A failure to do so may
 alter the semantics of structured headers.

Melnikov & Coates Standards Track [Page 11] RFC 5259 IMAP CONVERT extension July 2008

7. CONVERT Conversion Parameters

 The registry established by [MEDIAFEAT-REG] defines names of
 conversion parameters that can be used in the CONVERT command.
 Support for some conversion parameters is mandatory, as described in
 Section 7.1.
 According to [MEDIAFEAT-REG], conversion parameter names are case-
 insensitive.
 The following example illustrates how target picture dimensions can
 be specified in a CONVERT request using the PIX-X and PIX-Y
 parameters defined in [DISP-FEATURES].
      C: e001 UID CONVERT 100 ("IMAGE/JPEG" ("PIX-X" "128"
          "PIX-Y" "96")) BINARY[2]
      S: * 2 CONVERTED (TAG "e001") (UID 100 BINARY[2] ~{4182}
         <this part of a document is a rescaled image in
          JPEG format with width=128, height=96.>
         )
      S: e001 OK UID CONVERT COMPLETED

7.1. Mandatory-to-Implement Conversions and Conversion Parameters

 A server implementing CONVERT MUST support charset conversions for
 the text/plain MIME type, and MUST support charset conversions from
 iso-8859-1, iso-8859-2, iso-8859-3, iso-8859-4, iso-8859-5,
 iso-8859-6, iso-8859-7, iso-8859-8, and iso-8859-15 to utf-8.
 The server MUST list "text/plain" as an allowed destination
 conversion from "text/plain" MIME type (see Section 5.1).  A command
 'CONVERSIONS "text/plain" "text/plain"' MUST also return "charset"
 and "unknown-character-replacement" (see Section 12.1) as supported
 conversion parameters in the corresponding CONVERSION response.
 IMAP servers implementing the CONVERT extension MUST support
 recognition of the "charset" [CHARSET-REG] parameter for text/plain,
 text/html, text/css, text/csv, text/enriched, and text/xml MIME
 types.  Note, a server implementation is not required to support any
 conversion from the text MIME subtypes specified above, except for
 the mandatory-to-implement conversion described above.  That is, a
 server implementation MUST support the "charset" parameter for text/
 csv, only if it supports any conversion from text/csv.
 The server MUST support decoding of [RFC2047] headers and their
 conversion to UTF-8 as long as the encoded words are in one of the
 supported charsets.

Melnikov & Coates Standards Track [Page 12] RFC 5259 IMAP CONVERT extension July 2008

 Servers SHOULD offer additional character encoding conversions where
 they make sense, as character conversion libraries are generally
 available on many platforms.
 If the server cannot carry out the charset conversion while
 preserving all the characters (i.e., a source character can't be
 represented in the target charset), and the "unknown-character-
 replacement" conversion parameter is not specified, then the server
 MUST fail the conversion and MUST return the untagged ERROR
 BADPARAMETERS response (see Section 9).  If the value specified in
 the "unknown-character-replacement" conversion itself can't be
 represented in the target charset, then the server MUST also fail the
 conversion and MUST return the untagged ERROR BADPARAMETERS response
 (see Section 9).

7.2. Additional Features for Mobile Usage

 This section is informative.
 Based on the expected usage of CONVERT in mobile environments, server
 implementors should consider support for the following conversions:
 o  Conversion of HTML and XHTML documents to text/plain in ways that
    preserve at the minimum the document structure and tables.
 o  Image conversions among the types image/gif, image/jpeg, and
    image/png for at least the following parameters:
  • size limit (i.e., reduce quality)
  • width ("pix-x" parameter)
  • height ("pix-y" parameter)
  • resize directive (crop, stretch, aspect ratio)
    The support for "depth" may also be of interest.
 Audio conversion is also of interest but the relevant formats depend
 significantly on the usage context.

Melnikov & Coates Standards Track [Page 13] RFC 5259 IMAP CONVERT extension July 2008

8. Request/Response Data Items to CONVERT/UID CONVERT Commands

8.1. CONVERTED Untagged Response

 Contents:  convert correlator
            CONVERTED return data items
 The CONVERTED response may be sent as a result of a successful,
 partially successful, or unsuccessful CONVERT or UID CONVERT command
 specified in Section 6.
 The CONVERTED response starts with a message number, followed by the
 "CONVERTED" label.  The label is followed by a convert correlator,
 which contains the tag of the command that caused the response to be
 returned.  This can be used by a client to match a CONVERTED response
 against a corresponding CONVERT/UID CONVERT command.
 The convert correlator is followed by a list of one or more CONVERT
 return data items.  If the UID data item is returned, it MUST be
 returned as the first data item in the CONVERTED response.  This
 requirement is to simplify client implementations.  See Section 10
 and the remainder of Section 8 for more details.

8.2. BODYPARTSTRUCTURE CONVERT Request and Response Item

 BODYPARTSTRUCTURE[section-part]
 The CONVERT extension defines the BODYPARTSTRUCTURE CONVERT data
 item.  Data contained in the BODYPARTSTRUCTURE return data item
 follows the exact syntax specified in the [RFC3501] BODYSTRUCTURE
 data item, but only contains information for the converted part.  All
 information contained in BODYPARTSTRUCTURE pertains to the state of
 the part after it is converted, such as the converted MIME type, sub-
 type, size, or charset.  Note that the client can expect the returned
 MIME type to match the one it requested (as the server is required to
 obey the requested MIME type) and can treat mismatch as an error.
 The returned BODYPARTSTRUCTURE data MUST match the BINARY data
 returned for exactly the same conversion in the same IMAP "session".
 This requirement allows a client to request BODYPARTSTRUCTURE and
 BINARY data in separate commands in the same IMAP session.
 If the client lists a BODYPARTSTRUCTURE data item for a section-part
 before a BINARY data item for the same section-part, then, in the
 CONVERTED response, the server MUST return the BODYPARTSTRUCTURE data
 prior to the corresponding BINARY data.  Also, any BODYSTRUCTURE data

Melnikov & Coates Standards Track [Page 14] RFC 5259 IMAP CONVERT extension July 2008

 items MUST be after the UID data item if the UID data item is
 present.  Both requirements are to simplify handling of converted
 data in clients.
 Example:
       C: e002 CONVERT 2 (NIL ("PIX-X" "128" "PIX-Y" "96")) (BINARY[2]
           BODYPARTSTRUCTURE[2])
       S: * 2 CONVERTED (TAG "e002") (BODYPARTSTRUCTURE[2] ("IMAGE"
           "JPEG" () NIL NIL "8bit" 4182 NIL NIL NIL) BINARY[2]
           ~{4182}
          <this part of a document is a rescaled image in
           JPEG format with width=128, height=96.>
          )
       S: e002 OK CONVERT COMPLETED

8.3. BINARY.SIZE CONVERT Request and Response Item

 BINARY.SIZE[section-part]
 This item requests the converted size of the section (i.e., the size
 to expect in a response to the corresponding CONVERT BINARY request).
 The returned value MUST be exact and MUST NOT change during a
 duration of an IMAP "session", unless the message is expunged in
 another session (see below).  This allows a client to download a
 converted part in chunks (using "<partial>").  This requirement means
 that in most cases the server needs to perform conversion of the
 requested body part before returning its size.
 If the message is expunged in another session, then the server MAY
 return the value 0 in response to the BINARY.SIZE request item later
 in the same session.
 In order to allow for upgrade of server transcoding components,
 clients MUST NOT assume that repeating a particular body part
 conversion in another IMAP "session" would yield the same result as a
 previous conversion of the very same body part -- any characteristics
 of the converted body part might be different (format, size, etc.).
 In particular, clients MUST NOT cache sizes of converted messages/
 body parts beyond duration of any IMAP "session", or use sizes
 obtained in one connection in another IMAP connection to the same
 server.
 Historical note: Previous experience with IMAP servers that returned
 estimated RFC822.SIZE value shows that this caused interoperability
 problems.  If the server returns a value that is smaller than the
 actual size, this will result in data truncation if <partial>

Melnikov & Coates Standards Track [Page 15] RFC 5259 IMAP CONVERT extension July 2008

 download is used.  If the server returns a value that is bigger than
 the actual size, this might mislead a client to believe that it
 doesn't have enough storage to download a body part.
 Note for client implementors: client authors are cautioned that this
 might be an expensive operation for some server implementations.
 Requesting BINARY.SIZE for a large number of converted body parts or
 for multiple conversions of the same body part can result in slow
 performance and/or excessive server load and is discouraged.  Client
 implementors should consider implementation approaches that limit
 this request to only the most necessary cases and are encouraged to
 test the performance impact of BINARY.SIZE with multiple server
 implementations.

8.4. AVAILABLECONVERSIONS CONVERT Request and Response Item

 AVAILABLECONVERSIONS[section-part] allows the client to request the
 list of target MIME types the specified body part of a message or the
 whole message can be converted to.  This data item is only useful
 when the default conversion (see Section 6) is requested.
 This data item MUST return a list of target MIME types that is a
 subset of the list returned by the CONVERSIONS command for the same
 source and target MIME type pairs.  If specific conversion is
 requested, it MUST return the target MIME type as requested in the
 CONVERT command, or the ERROR phrase.
 For both specific or default conversion requests, if conversion
 parameters are specified, then the server must take them into
 consideration when generating the list of target MIME types.  For
 example, if one or more of the conversion parameters doesn't apply to
 a potential target MIME type, then such MIME type MUST be omitted
 from the resulting list.  If the server only had a single target MIME
 type candidate and it was discarded due to the list of conversion
 parameters, then the server SHOULD return the ERROR phrase instead of
 the empty list of the target MIME types.
 The AVAILABLECONVERSIONS request SHOULD be processed quickly if
 specified by itself.  Note that if a MIME type is returned in
 response to the AVAILABLECONVERSIONS, there is no guaranty that the
 corresponding BINARY/BINARY.SIZE/BODYPARTSTRUCTURE CONVERT request
 will not fail.
    Example:
          C: f001 CONVERT 2 (NIL) (AVAILABLECONVERSIONS[2])
          S: * 2 CONVERTED (TAG "f001") (AVAILABLECONVERSIONS[2]
                      (("IMAGE/JPEG" "application/PostScript"))
          S: f001 OK CONVERT COMPLETED

Melnikov & Coates Standards Track [Page 16] RFC 5259 IMAP CONVERT extension July 2008

8.5. Implementation Considerations

 Note that this section is normative.
 Servers MAY refuse to execute conversion requests that convert
 multiple messages and/or body parts at once, e.g., a conversion
 request that specifies multiple message numbers/UIDs.  If the server
 refuses a conversion because the request lists too many messages, the
 server MUST return the MAXCONVERTMESSAGES response code (see
 Section 9).  For example:
     C: g001 CONVERT 1:* ("text/plain" ("charset" "us-ascii"))
         BINARY[3]
     S: g001 NO [MAXCONVERTMESSAGES 1]
 If the server refuses a conversion because the request lists too many
 body parts, the server MUST return the MAXCONVERTPARTS response code
 (see Section 9).  For example:
    C: h001 CONVERT 1 ("text/plain" ("charset" "us-ascii"))
        (BINARY[1] BINARY[2])
    S: g001 NO [MAXCONVERTPARTS 1] You can only request 1 body part at
        any given time
 Note for server implementors: In order to improve performance,
 implementations SHOULD cache converted body parts.  For example, the
 server may perform a body part conversion when it receives the first
 BINARY.SIZE[...], BODYPARTSTRUCTURE[...], or BINARY[...] request and
 cache it until the client requests conversion/download of another
 body part, a different conversion of the same body part, or until the
 mailbox is closed.  In order to mitigate denial-of-service attacks
 from misbehaving or badly-written clients, a server SHOULD limit the
 number of converted body parts it can cache.  Servers SHOULD be able
 to cache at least 2 conversions at any given time.

9. Status Responses and Response Code Extensions

 A syntactically invalid MIME media type SHOULD generate a BAD tagged
 response from the server.  An unrecognized MIME media type generates
 a NO tagged response.
 Some transcodings may require parameters.  If a transcoding request
 with no parameters is sent for a format which requires parameters,
 the server will return an ERROR MISSINGPARAMETERS phrase in place of
 the data associated with the data items requested.  This is analogous
 to the NIL response in FETCH, but with structured data associated
 with the failure.

Melnikov & Coates Standards Track [Page 17] RFC 5259 IMAP CONVERT extension July 2008

 If the server is unable to perform the requested conversion because a
 resource is temporary unavailable (e.g., lack of disk space,
 temporary internal error, transcoding service down), then the server
 MUST return a tagged NO response that SHOULD contain the TEMPFAIL
 response code (see below), or an ERROR TEMPFAIL phrase.
 If the requested conversion cannot be performed because of a
 permanent error, for example, if a proprietary document format has no
 existing transcoding implementation, the server MUST return a
 CONVERTED response containing a ERROR BADPARAMETERS or ERROR
 MISSINGPARAMETERS phrase.
 The server MAY choose to return one ERROR phrase for a single
 conversion if several related data items are requested.  For
 instance:
   C: b002 CONVERT 2 ("text/plain" ("charset" "us-ascii"))
       (BINARY[3] BODYPARTSTRUCTURE[3])
   S: * 2 CONVERTED (tag "b002") (BODYPARTSTRUCTURE[3]
       (ERROR "Source text has non us-ascii" BADPARAMETERS
       "text/html" "text/plain" ("charset" "us-ascii")))
   S: b002 NO All conversions failed
 If at least one conversion succeeds, the server MUST return an OK
 response.  If all conversions fail, the server MAY return OK or NO.
 For instance:
   C: b002 CONVERT 2 ("text/plain" ("charset" "us-ascii"))
       (BINARY[3] BODYPARTSTRUCTURE[3] BINARY[4]
       BODYPARTSTRUCTURE[4])
   S: * 2 CONVERTED (tag "b002") (BODYPARTSTRUCTURE[3]
       (ERROR "Source text has non us-ascii" BADPARAMETERS
       "text/html" "text/plain" ("charset" "us-ascii"))
       BODYSTRUCTURE[4] ("TEXT" "PLAIN" (CHARSET US-ASCII)
       NIL NIL "8bit" 4182 NIL NIL NIL) BINARY[4] {4182}
         <body in text plain>
      )
   S: b002 OK Some conversions failed
 In general, the client can tell from the BODYPARTSTRUCTURE response
 whether or not its request was honored exactly, but may not know the
 reasons why.
 This document defines the following response codes that can be
 returned in the tagged NO response code.
 TEMPFAIL -  The transcoding request failed temporarily.  It might
       succeed later, so the client MAY retry.

Melnikov & Coates Standards Track [Page 18] RFC 5259 IMAP CONVERT extension July 2008

 MAXCONVERTMESSAGES <number> -  The server is unable or unwilling to
       convert more than <number> messages in any given CONVERT/UID
       CONVERT request.
 MAXCONVERTPARTS <number> -  The server is unable or unwilling to
       convert more than <number> body parts of a message at once in
       any given CONVERT/UID CONVERT request.
 The word ERROR is always followed by an informal human-readable
 descriptive text, which is followed by the convert-error-code.  The
 convert-error-code MUST be one of the following:
 TEMPFAIL mm -  The transcoding request failed temporarily.  It might
       succeed later, so the client MAY retry.  The client SHOULD wait
       for at least mm minutes before retrying.
 BADPARAMETERS  from-concrete-mime-type to-mime-type
 "(" transcoding-params ")" -
       The listed parameters were not understood, not valid for the
       source/destination MIME type pair, had invalid values or could
       not be honored for another reason noted in the human-readable
       text that was specified after the ERROR label.  The
       transcoding-params can be omitted, in which case, it means that
       the conversion from the from-concrete-mime-type to the to-mime-
       type is not possible.  If the from-concrete-mime-type is NIL,
       this means that the specified body part doesn't exist.  All
       unrecognized or irrelevant parameters MUST be listed in the
       transcoding-params.  It is not legal behavior to ignore
       irrelevant parameters.
       Note that if the client requested the "default conversion" (see
       Section 6), the to-mime-type contains the destination MIME type
       chosen by the server.
 MISSINGPARAMETERS  from-concrete-mime-type to-mime-type
 "(" transcoding-params ")" -
       The listed parameters are required for conversion of the
       specified source MIME type to the destination MIME type, but
       were not seen in the request.  Note that if the client
       requested the "default conversion" (see Section 6), the to-
       mime-type contains the destination MIME type chosen by the
       server.

Melnikov & Coates Standards Track [Page 19] RFC 5259 IMAP CONVERT extension July 2008

    Examples:
       C: b002 CONVERT 2 ("APPLICATION/PDF") BINARY[3]
       S: b002 NO [TEMPFAIL] All conversions failed
       C: b003 CONVERT 2 ("TEXT/PLAIN") BINARY[3]
       S: * 2 CONVERTED (tag "b003") (BINARY[3]
           (ERROR "CHARSET must be specified for text conversions"
           MISSINGPARAMETERS (CHARSET)))
       S: b003 NO All conversions failed
       C: b005 CONVERT 2 ("TEXT/PLAIN" (CHARSET "US-ASCII"
                 UNKNOWN-CHARACTER-REPLACEMENT "<badchar>")) BINARY[3]
       S: * 2 CONVERTED (tag "b005") (BINARY[3]
           (ERROR "UNKNOWN-CHARACTER-REPLACEMENT limited to 4
           bytes" BADPARAMETERS (UNKNOWN-CHARACTER-REPLACEMENT
           "<badchar>")))
       S: b005 NO All conversions failed

10. Formal Syntax

 The following syntax specification uses the augmented Backus-Naur
 Form (ABNF) notation as used in [ABNF], and incorporates by reference
 the core rules defined in that document.
 This syntax augments the grammar specified in [RFC3501] and
 [RFC3516].  Non-terminals not defined in this document can be found
 in [RFC3501], [RFC3516], [IMAPABNF], [MIME-MTSRP], and
 [MEDIAFEAT-REG].
     command-select  =/ convert
     uid             =/ "UID" SP convert
                   ; Unique identifiers used instead of message
                   ; sequence numbers
     convert         = "CONVERT" SP sequence-set SP convert-params SP
                       ( convert-att /
                         "(" convert-att *(SP convert-att) ")" )
     convert-att     = "UID" /
                       "BODYPARTSTRUCTURE" section-convert /
                       "BINARY" section-convert [partial] /
                       "BINARY.SIZE" section-convert /
                       "BODY[HEADER]" /
                       "BODY[" section-part ".HEADER]" /
                       "BODY[" section-part ".MIME]" /
                       "AVAILABLECONVERSIONS" section-convert

Melnikov & Coates Standards Track [Page 20] RFC 5259 IMAP CONVERT extension July 2008

                   ; <partial> is defined in [RFC3516].
                   ; <section-part> is defined in [RFC3501].
     convert-params = "(" (quoted-to-mime-type / default-conversion)
                      [SP "(" transcoding-params ")"] ")"
     quoted-to-mime-type = DQUOTE to-mime-type DQUOTE
     transcoding-params  = transcoding-param
                           *(SP transcoding-param)
     transcoding-param-names  = transcoding-param-name
                           *(SP transcoding-param-name)
     transcoding-param  = transcoding-param-name SP
                          transcoding-param-value
     transcoding-param-name = astring
              ; <transcod-param-name-nq> represented as a quoted,
              ; literal or atom.  Note that
              ; <transcod-param-name-nq> allows for "%", which is
              ; not allowed in atoms.  Such values must be
              ; represented as quoted or literal.
     transcod-param-name-nq = Feature-tag
              ; <Feature-tag> is defined in [MEDIAFEAT-REG].
     transcoding-param-value = astring
     default-conversion = "NIL"
     message-data   =/ nz-number SP "CONVERTED" SP convert-correlator
                        SP convert-msg-attrs
     convert-correlator = "(" "TAG" SP tag-string ")"
     tag-string = string
                   ; tag of the command that caused
                   ; the CONVERTED response, sent as
                   ; a string.
     convert-msg-attrs = "(" convert-msg-att *(SP convert-msg-att) ")"
                   ; "UID" MUST be the first data item, if present.
     convert-msg-att = msg-att-semistat / msg-att-conv-static
     msg-att-conv-static  = "UID" SP uniqueid
                   ; MUST NOT change for a message

Melnikov & Coates Standards Track [Page 21] RFC 5259 IMAP CONVERT extension July 2008

     msg-att-semistat =
                  ( "BINARY" section-convert ["<" number ">"] SP
                     (nstring / literal8 / converterror-phrase) ) /
                  ( "BINARY.SIZE" section-convert SP
                     (number / converterror-phrase) ) /
                  ( "BODYPARTSTRUCTURE" section-convert SP
                     (body / converterror-phrase) ) /
                  ( "AVAILABLECONVERSIONS" section-convert SP
                     (mimetype-list / converterror-phrase) )
                   ; MUST NOT change during an IMAP "session",
                   ; but not necessarily static in the long term.
     section-convert = section-binary
                   ; <section-binary> is defined in [RFC3516].
                   ;
                   ; Note that unlike [RFC3516], conversion
                   ; of a top level multipart/* is allowed.
     resp-text-code =/ "TEMPFAIL" /
                       "MAXCONVERTMESSAGES" SP nz-number /
                       "MAXCONVERTPARTS" SP nz-number
         ; <resp-text-code> is defined in [RFC3501].
     mimetype-and-params = quoted-to-mime-type
         [SP "(" transcoding-params ")"]
         ; always includes a specific MIME type
     mimetype-list = "(" "(" [quoted-to-mime-type
                              *(SP quoted-to-mime-type)] ")" ")"
         ; Unordered list of MIME types.  It can be empty.
         ;
         ; Two levels of parenthesis is needed to distinguish this
         ; data from <converterror-phrase>.
     converterror-phrase = "(" "ERROR" SP
          convert-err-descript SP convert-error-code ")"
     convert-error-code = "TEMPFAIL" [SP nz-number]
                        / bad-params
                        / missing-params
     convert-err-descript = string
          ; Human-readable text explaining the conversion error.
                  ; The default charset is US-ASCII, unless
                  ; the LANGUAGE command [IMAP-I18N] is called, when
                  ; the charset changes to UTF-8.
     quoted-from-mime-type = DQUOTE from-concrete-mime-type DQUOTE

Melnikov & Coates Standards Track [Page 22] RFC 5259 IMAP CONVERT extension July 2008

     bad-params = "BADPARAMETERS"
            1*(SP (quoted-from-mime-type / nil)
               SP mimetype-and-params)
         ; nil is only returned when the body part doesn't exist.
     missing-params = "MISSINGPARAMETERS"
            1*(SP quoted-from-mime-type SP
                  mimetype-and-missing-params)
     mimetype-and-missing-params = quoted-to-mime-type
         "(" transcoding-param-names ")"
         ; always includes a specific MIME type
     concrete-mime-type = type-name "/" subtype-name
                     ; i.e., "type/subtype".
                     ; type-name and subtype-name
                     ; are defined in [MIME-MTSRP].
     from-concrete-mime-type = concrete-mime-type
     to-mime-type = concrete-mime-type
     command-auth =/ conversions-cmd
     conversions-cmd = "CONVERSIONS" SP from-mime-type-req SP
                       to-mime-type-req
     from-mime-type-req = astring
       ; "mime-type-req" represented as IMAP <atom>,
       ; <quoted> or <literal>
     to-mime-type-req = astring
       ; <mime-type-req> represented as IMAP <atom>,
       ; <quoted> or <literal>.
       ; Note that <mime-type-req> allows for "*",
       ; which is not allowed in <atom>.  Such values must
       ; be represented as <quoted> or <literal>.
     any-mime-type  = "*"
     mime-type-req = any-mime-type /
                     (type-name "/" any-mime-type) /
                     concrete-mime-type
       ; '*', 'type/*' or 'type/subtype'.
       ; type-name is defined in [MIME-MTSRP].
     response-payload =/ conversion-data

Melnikov & Coates Standards Track [Page 23] RFC 5259 IMAP CONVERT extension July 2008

     conversion-data = "CONVERSION" SP quoted-from-mime-type SP
                       quoted-to-mime-type
                       [SP "(" transcoding-param-name
                        *(SP transcoding-param-name) ")"]

11. Manageability Considerations

 The monitoring of CONVERT operation is similar to monitoring of the
 IMAP FETCH operation.
 At the time of writing this document, there is no standard IMAP MIB
 defined.  Similarly, a standard MIB for monitoring CONVERT operations
 and their failures does not exist.  However, the authors believe that
 in the absence of such a MIB, server implementations SHOULD provide
 operators with tools to report the following information:
 o  which conversions (source and target MIME types and possibly
    conversion parameters used) are invoked more frequently and how
    long they take,
 o  information about conversion errors and which error condition
    caused them (see Section 9), and
 o  information about users which invoke conversion operation.
 This information can help operators to detect client abuse of this
 extension and scalability issues that might arise from its use.
 Standardizing these tools may be the subject of future work.

12. IANA Considerations

 IMAP4 capabilities are registered by publishing a Standards Track or
 IESG-approved Experimental RFC.  This document defines the CONVERT
 IMAP capability.  IANA has added this extension to the IANA IMAP
 Capability registry.
 IANA has performed registrations as defined in the following
 subsections.

Melnikov & Coates Standards Track [Page 24] RFC 5259 IMAP CONVERT extension July 2008

12.1. Registration of unknown-character-replacement Media Type

     Parameter
 IANA has added the following registration to the registry established
 by RFC 2506.
 To: "Media feature tags mailing list"
     <media-feature-tags@apps.ietf.org>
 Subject: Registration of media feature tag
          unknown-character-replacement
 Media feature tag name:
    unknown-character-replacement
 ASN.1 identifier associated with feature tag:
    1.3.6.1.8.1.33
 Summary of the media feature indicated by this feature tag:
     Allows servers that can perform charset conversion for text/plain
     text/html, text/css, text/csv, text/enriched, and text/xml MIME
     types to replace characters not supported by the target charset
     with a fixed string, such as "?".
     This feature tag is also applicable to other conversions
     to text, e.g., conversion of images using OCR (optical
     character recognition).
 Values appropriate for use with this feature tag:
     The feature tag contains a UTF-8 string used to replace any
     characters from the source media type that can't be
     represented in the target media type.
 The feature tag is intended primarily for use in the following
 applications, protocols, services, or negotiation mechanisms:
     IMAP CONVERT extension [RFC5259]
 Examples of typical use:
    C: b001 CONVERT 2 BINARY[3 ("text/plain" ("charset"
        "us-ascii" "unknown-character-replacement" "?"))]
 Related standards or documents:
    [RFC5259]
    [CHARSET-REG]
 Considerations particular to use in individual applications,
 protocols, services, or negotiation mechanisms:
    None

Melnikov & Coates Standards Track [Page 25] RFC 5259 IMAP CONVERT extension July 2008

 Interoperability considerations: None
 Security considerations: None
 Additional information:
    This media feature only make sense for MIME types that
    also support the "charset" media type parameter
    [CHARSET-REG].
 Name(s) & email address(es) of person(s) to contact for further
 information:
    Alexey Melnikov <alexey.melnikov@isode.com>
 Intended usage:
    COMMON
 Author/Change controller:
    IETF
 Requested IANA publication delay:
    None
 Other information:
    None

13. Security Considerations

 It is to be noted that some conversions may present security threats
 (e.g., converting a document to a damaging executable, exploiting a
 buffer overflow in a media codec/parser, or a denial-of-service
 attack against a client or a server such as requesting an image be
 scaled to extremely large dimensions).  Server SHOULD refuse to
 execute CPU-expensive conversions.  Servers should avoid dangerous
 conversions if possible.  Whenever possible, servers should perform
 verification of the converted attachments before returning them to
 the client.  Clients should be careful when requesting conversions or
 processing transformed attachments.  Clients SHOULD use mutual Simple
 Authentication and Security Layer (SASL) authentication and the SASL/
 TLS integrity layer, to make sure they are talking to trusted
 servers.
 When the client requests a server-side conversion of a signed body
 part (e.g., a part inside multipart/signed), there is no way for the
 client to verify that the converted content is authentic.  A client
 not trusting the server to perform conversion of a signed body part
 can download the signed object, verify the signature, and perform the
 conversion itself.

Melnikov & Coates Standards Track [Page 26] RFC 5259 IMAP CONVERT extension July 2008

 A client can create a carefully crafted bad message with the APPEND
 command followed by the CONVERT command to attack the server.  If the
 server's conversion function or library has a security problem (such
 as vulnerability to a buffer overflow), this could result in
 privilege escalation or denial of service.  In order to mitigate such
 attacks, servers SHOULD log the client authentication identity on
 APPEND and/or CONVERT operations in order to facilitate tracking of
 abusive clients.  Also server implementors SHOULD isolate the
 conversion function or library from the privileged mailstore, perhaps
 by running it within a distinct process.
 Deployments in which the actual transcoding is done outside the IMAP
 server in a separate server are recommended to keep the servers in
 the same trusted domain (e.g., subnet).

14. Acknowledgments

 Stephane H. Maes and Ray Cromwell from Oracle edited several earlier
 versions of this document.  Their contribution is gratefully
 acknowledged.
 The authors want to specifically acknowledge the excellent criticism
 and comments received from Randall Gellens (Qualcomm), Arnt
 Gulbrandsen (Oryx), Zoltan Ordogh (Nokia), Ben Last (Emccsoft), Dan
 Karp (Zimbra), Pete Resnick (Qualcomm), Chris Newman (Sun), Ted
 Hardie (Qualcomm), Larry Masinter (Adobe), Philip Guenther
 (Sendmail), Greg Vaudreuil (Alcatel-Lucent), David Harrington
 (Comcast), Dave Cridland (Isode), Pasi Eronen (Nokia), Magnus
 Westerlund (Ericsson), and Jari Arkko (Ericsson), which improved the
 quality of this specification considerably.
 The authors would also like to specially thank Dave Cridland for the
 MEDIACAPS command proposal and Dan Karp for the CONVERSIONS command
 proposal.
 The authors also want to thank all who have contributed key insight
 and extensively reviewed and discussed the concepts of CONVERT and
 its predecessor P-IMAP.  In particular, this includes the authors of
 the LCONVERT document: Rafiul Ahad (Oracle Corporation), Eugene Chiu
 (Oracle Corporation), Ray Cromwell (Oracle Corporation), Jia-der Day
 (Oracle Corporation), Vi Ha (Oracle Corporation), Wook-Hyun Jeong
 (Samsung Electronics Co. LTF), Chang Kuang (Oracle Corporation),
 Rodrigo Lima (Oracle Corporation), Stephane H. Maes (Oracle
 Corporation), Gustaf Rosell (Sony Ericsson), Jean Sini (Symbol
 Technologies), Sung-Mu Son (LG Electronics), Fan Xiaohui (China
 Mobile Communications Corporation (CMCC)), and Zhao Lijun (China
 Mobile Communications Corporation (CMCC)).

Melnikov & Coates Standards Track [Page 27] RFC 5259 IMAP CONVERT extension July 2008

15. References

15.1. Normative References

 [ABNF]           Crocker, D., Ed. and P. Overell, "Augmented BNF for
                  Syntax Specifications: ABNF", STD 68, RFC 5234,
                  January 2008.
 [CHARSET-REG]    Hoffman, P., "Registration of Charset and Languages
                  Media Features Tags", RFC 2987, November 2000.
 [IMAPABNF]       Melnikov, A. and C. Daboo, "Collected Extensions to
                  IMAP4 ABNF", RFC 4466, April 2006.
 [MEDIAFEAT-REG]  Holtman, K., Mutz, A., and T. Hardie, "Media Feature
                  Tag Registration Procedure", BCP 31, RFC 2506,
                  March 1999.
 [MIME-MTSRP]     Freed, N. and J. Klensin, "Media Type Specifications
                  and Registration Procedures", BCP 13, RFC 4288,
                  December 2005.
 [RFC2047]        Moore, K., "MIME (Multipurpose Internet Mail
                  Extensions) Part Three: Message Header Extensions
                  for Non-ASCII Text", RFC 2047, November 1996.
 [RFC2119]        Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2231]        Freed, N. and K. Moore, "MIME Parameter Value and
                  Encoded Word Extensions:
                  Character Sets, Languages, and Continuations",
                  RFC 2231, November 1997.
 [RFC3501]        Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL -
                  VERSION 4rev1", RFC 3501, March 2003.
 [RFC3516]        Nerenberg, L., "IMAP4 Binary Content Extension",
                  RFC 3516, April 2003.

Melnikov & Coates Standards Track [Page 28] RFC 5259 IMAP CONVERT extension July 2008

15.2. Informative References

 [DISP-FEATURES]  Masinter, L., Wing, D., Mutz, A., and K. Holtman,
                  "Media Features for Display, Print, and Fax",
                  RFC 2534, March 1999.
 [IMAP-I18N]      Newman, C., Gulbrandsen, A., and A. Melnikov,
                  "Internet Message Access Protocol
                  Internationalization", RFC 5255, June 2008.
 [LEM-STREAMING]  Cook, N., "Streaming Internet Messaging
                  Attachments", Work in Progress, June 2008.
 [OMA-ME-RD]      OMA, "Open Mobile Alliance Mobile Email Requirement
                  Document", OMA 55.919 3.0.0, December 2007.
 [OMA-STI]        OMA, "Open Mobile Alliance, Standard Transcoding
                  Interface Specification", OMA OMA-STI-V1_0,
                  December 2005.

Authors' Addresses

 Alexey Melnikov (editor)
 Isode Ltd
 5 Castle Business Village
 36 Station Road
 Hampton, Middlesex  TW12 2BX
 UK
 EMail: Alexey.Melnikov@isode.com
 Peter Coates (editor)
 Sun Microsystems
 185 Falcon Drive
 Whitehorse, YT  Y1A 6T2
 Canada
 EMail: peter.coates@Sun.COM

Melnikov & Coates Standards Track [Page 29] RFC 5259 IMAP CONVERT extension July 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.

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 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
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 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.

Melnikov & Coates Standards Track [Page 30]

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