draft-ietf-mhtml-related-00.txt   rfc2112.txt 
MIMESGML Working Group E. Levinson Network Working Group E. Levinson
Internet Draft: Multipart/Related XIson, Inc. Request for Comments: 2112 XIson, Inc.
<draft-ietf-mhtml-related-00.txt> 13 May 1996 Category: Standards Track March 1997
Obsoletes: 1872
The MIME Multipart/Related Content-type The MIME Multipart/Related Content-type
This draft document is being circulated for comment. Please send your
comments to the author or to the ietf-types and mhtml mail lists <ietf-
types@uninett.no> and <mhtml@segate.sunet.se>. If consensus is reached,
this document may be submitted to the RFC editor as a Proposed Standard
protocol specification for use with MIME.
Status of this Memo Status of this Memo
This document is an Internet Draft; Internet Drafts are working docu- This document specifies an Internet standards track protocol for the
ments of the Internet Engineering Task Force (IETF) its Areas, and Work- Internet community, and requests discussion and suggestions for
ing Groups. Note that other groups may also distribute working docu- improvements. Please refer to the current edition of the "Internet
ments as Internet Drafts. Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Internet Drafts are draft documents valid for a maximum of six months.
They may be updated, replaced, or obsoleted by other documents at any
time. It is not appropriate to use Internet Drafts as reference mate-
rial or to cite them other than as a "working draft" or "work in
progress".
Please check the abstract listing in each Internet Draft directory for
the current status of this or any other Internet Draft.
Abstract Abstract
The Multipart/Related content-type provides a common mechanism for rep- The Multipart/Related content-type provides a common mechanism for
resenting objects that are aggregates of related MIME body parts. This representing objects that are aggregates of related MIME body parts.
document defines the Multipart/Related content-type and provides exam- This document defines the Multipart/Related content-type and provides
ples of its use. examples of its use.
0. Changes from RFC 1872
Described the interaction between Multipart/Related and the Content-
Disposition headers. This document will obsolete RFC 1872.
Behavior for unknown types changed from "shall suppress" to "should give
user the option ...".
1. Introduction 1. Introduction
Several applications of MIME, including MIME-PEM, and MIME-Macintosh and Several applications of MIME, including MIME-PEM, and MIME-Macintosh
other proposals, require multiple body parts that make sense only in the and other proposals, require multiple body parts that make sense only
aggregate. The present approach to these compound objects has been to in the aggregate. The present approach to these compound objects has
define specific multipart subtypes for each new object. In keeping with been to define specific multipart subtypes for each new object. In
the MIME philosophy of having one mechanism to achieve the same goal for keeping with the MIME philosophy of having one mechanism to achieve
different purposes, this document describes a single mechanism for such the same goal for different purposes, this document describes a
aggregate or compound objects. single mechanism for such aggregate or compound objects.
The Multipart/Related content-type addresses the MIME representation of
Internet Draft Multipart/Related
compound objects. The object is categorized by a "type" parameter. The Multipart/Related content-type addresses the MIME representation
Additional parameters are provided to indicate a specific starting body of compound objects. The object is categorized by a "type"
part or root and auxiliary information which may be required when parameter. Additional parameters are provided to indicate a specific
unpacking or processing the object. starting body part or root and auxiliary information which may be
required when unpacking or processing the object.
Multipart/Related MIME entities may contain Content-Disposition headers Multipart/Related MIME entities may contain Content-Disposition
that provide suggestions for the storage and display of a body part. headers that provide suggestions for the storage and display of a
Multipart/Related processing takes precedence over Content-Disposition; body part. Multipart/Related processing takes precedence over
the interaction between them is discussed in section 4. Content-Disposition; the interaction between them is discussed in
section 4.
Responsibility for the display or processing of a Multipart/Related's Responsibility for the display or processing of a Multipart/Related's
constituent entities rests with the application that handles the com- constituent entities rests with the application that handles the
pound object. compound object.
2. Multipart/Related Registration Information 2. Multipart/Related Registration Information
The following form is copied from RFC 1590, Appendix A. The following form is copied from RFC 1590, Appendix A.
To: IANA@isi.edu To: IANA@isi.edu Subject: Registration of new Media Type content-
Subject: Registration of new Media Type content-type/subtype type/subtype
Media Type name: Multipart Media Type name: Multipart
Media subtype name: Related Media subtype name: Related
Required parameters: Type, a media type/subtype. Required parameters: Type, a media type/subtype.
Optional parameters: Start Optional parameters: Start
Start-info Start-info
Encoding considerations: Multipart content-types cannot have Encoding considerations: Multipart content-types cannot have
encodings. encodings.
Security considerations: Depends solely on the referenced type. Security considerations: Depends solely on the referenced type.
Published specification: RFC-REL (this document). Published specification: RFC-REL (this document).
Person & email address to contact for further information: Person & email address to contact for further information:
Edward Levinson Edward Levinson
Accurate Information Systems, Inc. 47 Clive Street
2 Industrial Way Metuchen, NJ 08840-1060
Eatontown, NJ 07724 +1 908 494 1606
+1 908 389 5550 XIson@cnj.digex.net
+1 908 389 5556 (fax)
ELevinson@Accurate.com
3. Intended usage 3. Intended usage
The Multipart/Related media type is intended for compound The Multipart/Related media type is intended for compound objects
objects consisting of several inter-related body parts. For a consisting of several inter-related body parts. For a
Multipart/Related object, proper display cannot be achieved by Multipart/Related object, proper display cannot be achieved by
individually displaying the constituent body parts. The con- individually displaying the constituent body parts. The content-type
tent-type of the Multipart/Related object is specified by the of the Multipart/Related object is specified by the type parameter.
Internet Draft Multipart/Related The "start" parameter, if given, points, via a content-ID, to the
body part that contains the object root. The default root is the
type parameter. The "start" parameter, if given, points, via first body part within the Multipart/Related body.
a content-ID, to the body part that contains the object root.
The default root is the first body part within the Multi-
part/Related body.
The relationships among the body parts of a compound object The relationships among the body parts of a compound object
distinguishes it from other object types. These relationships distinguishes it from other object types. These relationships are
are often represented by links internal to the object's compo- often represented by links internal to the object's components that
nents that reference the other components. Within a single reference the other components. Within a single operating
operating environment the links are often file names, such environment the links are often file names, such links may be
links may be represented within a MIME message using content- represented within a MIME message using content-IDs or the value of
IDs or the value of some other "Content-" headers. some other "Content-" headers.
3.1. The Type Parameter 3.1. The Type Parameter
The type parameter must be specified and its value is the MIME The type parameter must be specified and its value is the MIME media
media type of the "root" body part. It permits a MIME user type of the "root" body part. It permits a MIME user agent to
agent to determine the content-type without reference to the determine the content-type without reference to the enclosed body
enclosed body part. If the value of the type parameter and part. If the value of the type parameter and the root body part's
the root body part's content-type differ then the User Agent's content-type differ then the User Agent's behavior is undefined.
behavior is undefined.
3.2. The Start Parameter 3.2. The Start Parameter
The start parameter, if given, is the content-ID of the com- The start parameter, if given, is the content-ID of the compound
pound object's "root". If not present the "root" is the first object's "root". If not present the "root" is the first body part in
body part in the Multipart/Related entity. The "root" is the the Multipart/Related entity. The "root" is the element the
element the applications processes first. applications processes first.
3.3. The Start-Info Parameter 3.3. The Start-Info Parameter
Additional information can be provided to an application by Additional information can be provided to an application by the
the start-info parameter. It contains either a string or start-info parameter. It contains either a string or points, via a
points, via a content-ID, to another MIME entity in the mes- content-ID, to another MIME entity in the message. A typical use
sage. A typical use might be to provide additional command might be to provide additional command line parameters or a MIME
line parameters or a MIME entity giving auxiliary information entity giving auxiliary information for processing the compound
for processing the compound object. object.
Applications that use Multipart/Related must specify the Applications that use Multipart/Related must specify the
interpretation of start-info. User Agents shall provide the interpretation of start-info. User Agents shall provide the
parameter's value to the processing application. Processes parameter's value to the processing application. Processes can
can distinguish a start-info reference from a token or quoted- distinguish a start-info reference from a token or quoted-string by
string by examining the first non-white-space character, "<" examining the first non-white-space character, "<" indicates a
indicates a reference. reference.
3.4. Syntax 3.4. Syntax
related-param := [ ";" "start" "=" cid ] related-param := [ ";" "start" "=" cid ]
[ ";" "start-info" "=" [ ";" "start-info" "="
( cid-list / value ) ] ( cid-list / value ) ]
[ ";" "type" "=" type "/" subtype ] [ ";" "type" "=" type "/" subtype ]
; order independent ; order independent
cid-list := cid cid-list cid-list := cid cid-list
Internet Draft Multipart/Related
cid := msg-id ; c.f. [822] cid := msg-id ; c.f. [822]
value := token / quoted-string ; c.f. [MIME] value := token / quoted-string ; c.f. [MIME]
; value cannot begin with "<" ; value cannot begin with "<"
Note that the parameter values will usually require quoting. Note that the parameter values will usually require quoting. Msg-id
Msg-id contains the special characters "<", ">", "@", and per- contains the special characters "<", ">", "@", and perhaps other
haps other special characters. If msg-id contains quoted- special characters. If msg-id contains quoted-strings, those quote
strings, those quote marks must be escaped. Similarly, the marks must be escaped. Similarly, the type parameter contains the
type parameter contains the special character "/". special character "/".
4. Handling Content-Disposition Headers 4. Handling Content-Disposition Headers
Content-Disposition Headers [DISP] suggest presentation styles Content-Disposition Headers [DISP] suggest presentation styles for
for MIME body parts. [DISP] describes two presentation MIME body parts. [DISP] describes two presentation styles, called
styles, called the disposition type, INLINE and ATTACHMENT. the disposition type, INLINE and ATTACHMENT. These, used within a
These, used within a multipart entity, allow the sender to multipart entity, allow the sender to suggest presentation
suggest presentation information. [DISP] also provides for an information. [DISP] also provides for an optional storage (file)
optional storage (file) name. Content-Disposition headers name. Content-Disposition headers could appear in one or more body
could appear in one or more body parts contained within a Mul- parts contained within a Multipart/Related entity.
tipart/Related entity.
Using Content-Disposition headers in addition to Multi- Using Content-Disposition headers in addition to Multipart/Related
part/Related provides presentation information to User Agents provides presentation information to User Agents that do not
that do not recognize Multipart/Related. They will treat the recognize Multipart/Related. They will treat the multipart as
multipart as Multipart/Mixed and they may find the Content- Multipart/Mixed and they may find the Content-Disposition information
Disposition information useful. useful.
With Multipart/Related however, the application processing the With Multipart/Related however, the application processing the
compound object determines the presentation style for all the compound object determines the presentation style for all the
contained parts. In that context the Content-Disposition contained parts. In that context the Content-Disposition header
header information is redundant or even misleading. Hence, information is redundant or even misleading. Hence, User Agents that
User Agents that understand Multipart/Related shall ignore the understand Multipart/Related shall ignore the disposition type within
disposition type within a Multipart/Related body part. a Multipart/Related body part.
It may be possible for a User Agent capable of handling both It may be possible for a User Agent capable of handling both
Multipart/Related and Content-Disposition headers to provide Multipart/Related and Content-Disposition headers to provide the
the invoked application the Content-Disposition header's invoked application the Content-Disposition header's optional
optional filename parameter to the Multipart/Related. The use filename parameter to the Multipart/Related. The use of that
of that information will depend on the specific application information will depend on the specific application and should be
and should be specified when describing the handling of the specified when describing the handling of the corresponding compound
corresponding compound object. Such descriptions would be object. Such descriptions would be appropriate in an RFC registering
appropriate in an RFC registering that object's media type. that object's media type.
5. Examples 5. Examples
5.1 Application/X-FixedRecord 5.1 Application/X-FixedRecord
The X-FixedRecord content-type consists of one or more octet- The X-FixedRecord content-type consists of one or more octet-streams
streams and a list of the lengths of each record. The root, and a list of the lengths of each record. The root, which lists the
which lists the record lengths of each record within the record lengths of each record within the streams. The record length
streams. The record length list, type Application/X- list, type Application/X-FixedRecord, consists of a set of INTEGERs
FixedRecord, consists of a set of INTEGERs in ASCII format, in ASCII format, one per line. Each INTEGER gives the number of
one per line. Each INTEGER gives the number of octets from octets from the octet-stream body part that constitute the next
Internet Draft Multipart/Related "record".
the octet-stream body part that constitute the next "record".
The example below, uses a single data block. The example below, uses a single data block.
Content-Type: Multipart/Related; boundary=example-1 Content-Type: Multipart/Related; boundary=example-1
start="<950120.aaCC@XIson.com>"; start="<950120.aaCC@XIson.com>";
type="Application/X-FixedRecord" type="Application/X-FixedRecord"
start-info="-o ps" start-info="-o ps"
--example-1 --example-1
Content-Type: Application/X-FixedRecord Content-Type: Application/X-FixedRecord
Content-ID: <950120.aaCC@XIson.com> Content-ID: <950120.aaCC@XIson.com>
skipping to change at page 5, line 44 skipping to change at page 6, line 7
BFIEkgTwpBbmQgb24gaGlzIGZhcm0gaGUgaGFk BFIEkgTwpBbmQgb24gaGlzIGZhcm0gaGUgaGFk
IHNvbWUgZHVja3MKRSBJIEUgSSBPCldpdGggYS IHNvbWUgZHVja3MKRSBJIEUgSSBPCldpdGggYS
BxdWFjayBxdWFjayBoZXJlLAphIHF1YWNrIHF1 BxdWFjayBxdWFjayBoZXJlLAphIHF1YWNrIHF1
YWNrIHRoZXJlLApldmVyeSB3aGVyZSBhIHF1YW YWNrIHRoZXJlLApldmVyeSB3aGVyZSBhIHF1YW
NrIHF1YWNrCkUgSSBFIEkgTwo= NrIHF1YWNrCkUgSSBFIEkgTwo=
--example-1-- --example-1--
5.2 Text/X-Okie 5.2 Text/X-Okie
The Text/X-Okie is an invented markup language permitting the The Text/X-Okie is an invented markup language permitting the
inclusion of images with text. A feature of this example is inclusion of images with text. A feature of this example is the
the inclusion of two additional body parts, both picture. They inclusion of two additional body parts, both picture. They are
are referred to internally by the encapsulated document via referred to internally by the encapsulated document via each
each picture's body part content-ID. Usage of "cid:", as in picture's body part content-ID. Usage of "cid:", as in this example,
this example, may be useful for a variety of compound objects. may be useful for a variety of compound objects. It is not, however,
It is not, however, a part of the Multipart/Related specifica- a part of the Multipart/Related specification.
tion.
Content-Type: Multipart/Related; boundary=example-2; Content-Type: Multipart/Related; boundary=example-2;
start="<950118.AEBH@XIson.com>" start="<950118.AEBH@XIson.com>"
type="Text/x-Okie" type="Text/x-Okie"
--example-2 --example-2
Content-Type: Text/x-Okie; charset=iso-8859-1; Content-Type: Text/x-Okie; charset=iso-8859-1;
Internet Draft Multipart/Related
declaration="<950118.AEB0@XIson.com>" declaration="<950118.AEB0@XIson.com>"
Content-ID: <950118.AEBH@XIson.com> Content-ID: <950118.AEBH@XIson.com>
Content-Description: Document Content-Description: Document
{doc} {doc}
This picture was taken by an automatic camera mounted ... This picture was taken by an automatic camera mounted ...
{image file=cid:<950118.AECB@XIson.com>} {image file=cid:<950118.AECB@XIson.com>}
{para} {para}
Now this is an enlargement of the area ... Now this is an enlargement of the area ...
{image file=cid:<950118:AFDH@XIson.com>} {image file=cid:<950118:AFDH@XIson.com>}
skipping to change at page 6, line 36 skipping to change at page 7, line 7
Content-Type: image/jpeg Content-Type: image/jpeg
Content-ID: <950118.AECB@XIson.com> Content-ID: <950118.AECB@XIson.com>
Content-Transfer-Encoding: BASE64 Content-Transfer-Encoding: BASE64
Content-Description: Picture B Content-Description: Picture B
[encoded jpeg image] [encoded jpeg image]
--example-2-- --example-2--
5.3 Content-Disposition 5.3 Content-Disposition
In the above example each image body part could also have a In the above example each image body part could also have a Content-
Content-Disposition header. For example, Disposition header. For example,
... ...
--example-2 --example-2
Content-Type: image/jpeg Content-Type: image/jpeg
Content-ID: <950118.AECB@XIson.com> Content-ID: <950118.AECB@XIson.com>
Content-Transfer-Encoding: BASE64 Content-Transfer-Encoding: BASE64
Content-Description: Picture B Content-Description: Picture B
Content-Disposition: INLINE Content-Disposition: INLINE
[encoded jpeg image] [encoded jpeg image]
--example-2-- --example-2--
User Agents that recognize Multipart/Related will ignore the User Agents that recognize Multipart/Related will ignore the
Content-Disposition header's disposition type. Other User Content-Disposition header's disposition type. Other User Agents
Agents will process the Multipart/Related as Multipart/Mixed will process the Multipart/Related as Multipart/Mixed and may make
and may make use of that header's information. use of that header's information.
6. User Agent Requirements 6. User Agent Requirements
User agents that do not recognize Multipart/Related shall, in User agents that do not recognize Multipart/Related shall, in
accordance with [MIME], treat the entire entity as Multi- accordance with [MIME], treat the entire entity as Multipart/Mixed.
part/Mixed. MIME User Agents that do recognize Multi- MIME User Agents that do recognize Multipart/Related entities but are
part/Related entities but are unable to process the given type unable to process the given type should give the user the option of
Internet Draft Multipart/Related suppressing the entire Multipart/Related body part shall be.
should give the user the option of suppressing the entire Mul-
tipart/Related body part shall be.
Existing MIME-capable mail user agents (MUAs) handle the Existing MIME-capable mail user agents (MUAs) handle the existing
existing media types in a straightforward manner. For dis- media types in a straightforward manner. For discrete media types
crete media types (e.g. text, image, etc.) the body of the (e.g. text, image, etc.) the body of the entity can be directly
entity can be directly passed to a display process. Similarly passed to a display process. Similarly the existing composite
the existing composite subtypes can be reduced to handing one subtypes can be reduced to handing one or more discrete types.
or more discrete types. Handling Multipart/Related differs in Handling Multipart/Related differs in that processing cannot be
that processing cannot be reduced to handling the individual reduced to handling the individual entities.
entities.
The following sections discuss what information the processing The following sections discuss what information the processing
application requires. application requires.
It is possible that an application specific "receiving agent" It is possible that an application specific "receiving agent" will
will manipulate the entities for display prior to invoking manipulate the entities for display prior to invoking actual
actual application process. Okie, above, is an example of application process. Okie, above, is an example of this; it may need
this; it may need a receiving agent to parse the document and a receiving agent to parse the document and substitute local file
substitute local file names for the originator's file names. names for the originator's file names. Other applications may just
Other applications may just require a table showing the corre- require a table showing the correspondence between the local file
spondence between the local file names and the originator's. names and the originator's. The receiving agent takes responsibility
The receiving agent takes responsibility for such processing. for such processing.
6.1 Data Requirements 6.1 Data Requirements
MIME-capable mail user agents (MUAs) are required to provide MIME-capable mail user agents (MUAs) are required to provide the
the application: application:
(a) the bodies of the MIME entities and the entity Content-* (a) the bodies of the MIME entities and the entity Content-*
headers, headers,
(b) the parameters of the Multipart/Related Content-type (b) the parameters of the Multipart/Related Content-type
header, and header, and
(c) the correspondence between each body's local file name, (c) the correspondence between each body's local file name,
that body's header data, and, if present, the body part's that body's header data, and, if present, the body part's
content-ID. content-ID.
5.1 Storing Multipart/Related Entities 6.2 Storing Multipart/Related Entities
The Multipart/Related media type will be used for objects that The Multipart/Related media type will be used for objects that have
have internal linkages between the body parts. When the internal linkages between the body parts. When the objects are
objects are stored the linkages may require processing by the stored the linkages may require processing by the application or its
application or its receiving agent. receiving agent.
6.3 Recursion 6.3 Recursion
MIME is a recursive structure. Hence one must expect a Multi- MIME is a recursive structure. Hence one must expect a
part/Related entity to contain other Multipart/Related enti- Multipart/Related entity to contain other Multipart/Related entities.
ties. When a Multipart/Related entity is being processed for When a Multipart/Related entity is being processed for display or
display or storage, any enclosed Multipart/Related entities storage, any enclosed Multipart/Related entities shall be processed
shall be processed as though they were being stored. as though they were being stored.
Internet Draft Multipart/Related
6.4 Configuration Considerations 6.4 Configuration Considerations
It is suggested that MUAs that use configuration mechanisms, It is suggested that MUAs that use configuration mechanisms, see
see [CFG] for an example, refer to Multipart/Related as Multi- [CFG] for an example, refer to Multipart/Related as
part/Related/<type>, were <type> is the value of the "type" Multipart/Related/<type>, were <type> is the value of the "type"
parameter. parameter.
7. Security considerations 7. Security considerations
Security considerations relevant to Multipart/Related are Security considerations relevant to Multipart/Related are identical
identical to those of the underlying content-type. to those of the underlying content-type.
8. Acknowledgments 8. Acknowledgments
This proposal is the result of conversations the author has This proposal is the result of conversations the author has had with
had with many people. In particular, Harald A. Alvestrand, many people. In particular, Harald A. Alvestrand, James Clark,
James Clark, Charles Goldfarb, Gary Houston, Ned Freed, Ray Charles Goldfarb, Gary Houston, Ned Freed, Ray Moody, and Don
Moody, and Don Stinchfield, provided both encouragement and Stinchfield, provided both encouragement and invaluable help. The
invaluable help. The author, however, take full responsibil- author, however, take full responsibility for all errors contained in
ity for all errors contained in this document. this document.
9. References 9. References
[822] Crocker, D., "Standard for the Format of ARPA [822] Crocker, D., "Standard for the Format of ARPA
Internet Text Messages", August 1982, University Internet Text Messages", August 1982, University
of Delaware, RFC 822. of Delaware, RFC 822.
[CID] E. Levinson, J. Clark, "Message/External-Body Con-
tent-ID Access Type", 12/26/1995, RFC 1873 Levin-
son, E., "Message/External-Body Content-ID Access
Type", work in progress,
ftp://ds.internic.net/internet-drafts/draft-ietf-
mimesgml-access-cid-01.txt.
[CFG] Borenstein, N., "A User Agent Configuration Mecha- [CID] E. Levinson, J. Clark, "Message/External-Body
nism For Multimedia Mail Format Information", Content-ID Access Type", 12/26/1995, RFC 1873
September 23, 1993, RFC 1524 Levinson, E., "Message/External-Body Content-ID
Access Type", February 1997, RFC 2111.
[DISP] R. Troost, S. Dorner, "Communicating Presentation [CFG] Borenstein, N., "A User Agent Configuration
Information in Internet Messages: The Content- Mechanism For Multimedia Mail Format
Disposition Header", June 7, 1995, RFC 1806 Information", September 23, 1993, RFC 1524
[MIME] Borenstein, N. and Freed, N., "MIME (Multipurpose [DISP] R. Troost, S. Dorner, "Communicating Presentation
Internet Mail Extensions): Mechanisms for Specify- Information in Internet Messages: The Content-
ing and Describing the Format of Internet Message Disposition Header", June 7, 1995, RFC 1806
Bodies", June 1992, RFC 1341.
9. Author's address [MIME] Borenstein, N. and Freed, N., "MIME (Multipurpose
Internet Mail Extensions): Mechanisms for
Specifying and Describing the Format of Internet
Message Bodies", June 1992, RFC 1341.
Edward Levinson 9. Author's Address
XIson, Inc.
47 Clive Street
Internet Draft Multipart/Related
Metuchen, NJ 08840-1060 Edward Levinson
USA XIson, Inc.
+1 908 549 3716 47 Clive Street
<XIson@cnj.digex.com> Metuchen, NJ 08840-1060
USA
+1 908 549 3716
<XIson@cnj.digex.com>
 End of changes. 57 change blocks. 
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