RFC 1872 (rfc1872) - Page 3 of 8
The MIME Multipart/Related Content-type
Alternative Format: Original Text Document
RFC 1872 Multipart/Related December 1995 represented within a MIME message using content-IDs or the value of some other "Content-" header. 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. Note: Constraining the "type" parameter's value to an existing media type allows the appropriate processing to be identified without creating yet another hierarchy of registered types. A possible default action would have the MIME mail User Agent (MUA) to display the "start" entity alone when it could process the media type as a basic type but not as Multipart/Related. 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 application processes first. In the case of a Multipart/Alternative body part containing several entities with identical content-IDs the start entity should be selected using the Multipart/Alternative rules. Note: The "start" parameter allows for types in which the root element gets generated by the sending application, perhaps on the fly. Such an application can create the "start" content-id when processing begins and then insert the body part when it is complete. 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, "<" indicates a Levinson Experimental
