RFC 2112 (rfc2112) - Page 3 of 9
The MIME Multipart/Related Content-type
Alternative Format: Original Text Document
RFC 2112 MIME Multipart/Related Content-type March 1997
The relationships among the body parts of a compound object
distinguishes it from other object types. These relationships are
often represented by links internal to the object's components that
reference the other components. Within a single operating
environment the links are often file names, such links may be
represented within a MIME message using content-IDs or the value of
some other "Content-" headers.
3.1. The Type Parameter
The type parameter must be specified and its value is the MIME media
type of the "root" body part. It permits a MIME user agent to
determine the content-type without reference to the enclosed body
part. If the value of the type parameter and the root body part's
content-type differ then the User Agent's behavior is undefined.
3.2. The Start Parameter
The start parameter, if given, is the content-ID of the compound
object's "root". If not present the "root" is the first body part in
the Multipart/Related entity. The "root" is the element the
applications processes first.
3.3. The Start-Info Parameter
Additional information can be provided to an application by the
start-info parameter. It contains either a string or points, via a
content-ID, to another MIME entity in the message. A typical use
might be to provide additional command line parameters or a MIME
entity giving auxiliary information for processing the compound
object.
Applications that use Multipart/Related must specify the
interpretation of start-info. User Agents shall provide the
parameter's value to the processing application. Processes can
distinguish a start-info reference from a token or quoted-string by
examining the first non-white-space character, "