rfc1872.txt

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RFC 1872                   Multipart/Related               December 1995


     Content-ID: <[e-mail]>

     T2xkIE1hY0RvbmFsZCBoYWQgYSBmYXJtCkUgSS
     BFIEkgTwpBbmQgb24gaGlzIGZhcm0gaGUgaGFk
     IHNvbWUgZHVja3MKRSBJIEUgSSBPCldpdGggYS
     BxdWFjayBxdWFjayBoZXJlLAphIHF1YWNrIHF1
     YWNrIHRoZXJlLApldmVyeSB3aGVyZSBhIHF1YW
     NrIHF1YWNrCkUgSSBFIEkgTwo=
     --example-1
     Content-Type: Application/X-FixedRecord
     Content-ID: <[e-mail]>

     25
     10
     34
     10
     25
     21
     26
     10
     --example-1--

4.2 Text/X-Okie

The Text/X-Okie is an invented markup language, similar to
HTML, that permits the inclusion of images with text.  A
feature of this example is the inclusion of two additional
body parts, both picture. They are referred to internally by
the encapsulated document via each picture's body part
content-ID.  Usage of "cid:", as in this example, may be
useful for a variety of compound objects.  It is not, however,
a part of the Multipart/Related specification.

     Content-Type: Multipart/Related; boundary=example-2;
             start="<[e-mail]>"
             type="Text/x-Okie"

     --example-2
     Content-Type: Text/x-Okie; charset=iso-8859-1;
             declaration="<[e-mail]>"
     Content-ID: <[e-mail]>
     Content-Description: Document

     {doc}
     This picture was taken by an automatic camera mounted ...
     {image file=cid:[e-mail]}
     {para}
     Now this is an enlargement of the area ...



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RFC 1872                   Multipart/Related               December 1995


     {image file=cid:[e-mail]}
     {/doc}
     --example-2
     Content-Type: image/jpeg
     Content-ID: <[e-mail]>
     Content-Transfer-Encoding: BASE64
     Content-Description: Picture A

     [encoded jpeg image]
     --example-2
     Content-Type: image/jpeg
     Content-ID: <[e-mail]>
     Content-Transfer-Encoding: BASE64
     Content-Description: Picture B

     [encoded jpeg image]
     --example-1--

5.  User Agent Requirements

   User agents that do not recognize Multipart/Related shall, in
   accordance with [MIME], treat the entire entity as Multipart/Mixed.
   MIME User Agents that recognize Multipart/Related entities but are
   unable to process the given type shall either suppress the entire
   Multipart/Related body part or process the root alone.  In either
   case the user should be notified of the MUA's action.

   Handling Multipart/Related differs from other media types in that
   processing cannot be reduced to handling the individual entities.
   Existing media types are handled by MIME-capable MUAs handle in a
   straightforward manner.  For basic media types (e.g., text, image,
   etc.) the body of the entity can be directly passed to a display
   process.  Composite media types can be reduced to handing one or more
   discrete types.

   Multipart/Related provides an irreducible composite media type.

   The following sections discuss what information the processing
   application requires.

   It is possible that an application specific "receiving agent" will
   manipulate the entities, after initial processing by the MIME User
   Agent, prior to invoking actual application process.  From the
   viewpoint of the MUA, the receiving agent is the application.  Okie,
   above, demonstrates this; it may need a receiving agent to parse the
   document and substitute local file names for the originator's file
   names.  Other applications may just require a table showing the
   correspondence between the local file names and the originator's.



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RFC 1872                   Multipart/Related               December 1995


   The receiving agent takes responsibility any for such processing.

5.1 Data Requirements

   MIME-capable MUAs are required to provide the application:

   (a)  the bodies of the MIME entities and the entity Content-*
        headers,

   (b)  the parameters of the Multipart/Related Content-type
        header, and

   (c)  the correspondence between each body's local file name,
        that body's header data, and, if present, the body part's
        content-ID.

5.2 Storing Multipart/Related Entities

   The Multipart/Related media type will be used for objects that have
   internal linkages between the body parts.  When the objects are
   stored the linkages may require processing by the application or its
   receiving agent.

5.3 Recursion

   MIME is a recursive structure.  Hence one must expect a
   Multipart/Related entity to contain other Multipart/Related entities.
   When a Multipart/Related entity is being processed for display or
   storage, any enclosed Multipart/Related entities shall be processed
   as though they were being stored.  It shall be the responsibility of
   the application handling the outermost Multipart/Related to insure
   the appropriate processing of embedded Multipart/Related entities.

5.5 Configuration Considerations

   It is suggested that MUAs that use configuration mechanisms, see
   [CFG] for an example, refer to Multipart/Related as
   Multipart/Related/<type>, were <type> is the value of the "type"
   parameter.

6.  Security Considerations

   Security considerations relevant to Multipart/Related are identical
   to those of the underlying content-type.







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RFC 1872                   Multipart/Related               December 1995


7.  Acknowledgments

   This proposal is the result of conversations the author has had with
   many people.  In particular, similar work was described by Harald A.
   Alvestrand (early drafts of Multipart/Related), Dave Crocker
   (Multipart/Families), and Keith Moore (Multipart/References). In
   addition, James Clark, Charles Goldfarb, Gary Houston, Ned Freed, Ray
   Moody, and Don Stinchfield, provided both encouragement and
   invaluable help.  The author, however, take full responsibility for
   all errors contained in this document.

8.  References

   [822]       Crocker, D., "Standard for the Format of ARPA
               Internet Text Messages", STD 11, RFC 822, UDEL,
               August 1982.

   [CFG]       Borenstein, N., "A User Agent Configuration
               Mechanism For Multimedia Mail Format Information",
               RFC 1524, Bellcore, September 1993.

   [MIME]      Borenstein, N. and and N. Freed, "MIME (Multipurpose
               Internet Mail Extensions) Part One: Mechanisms for
               Specifying and Describing the Format of Internet Message
               Bodies", RFC 1521, Bellcore, Innosoft, September 1993.

9.  Author's Address

   Edward Levinson
   Accurate Information Systems, Inc.
   2 Industrial Way
   Eatontown, NJ  07724-2265
   USA

   Phone: [phone]
   EMail: [e-mail]















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