Practical Internet Groupware

Email: Semistructured Documents

The notion that messages carry semistructured data is central to this book. RFC934 (January 1985, Proposed Standard for Message Encapsulation) introduces the idea of a message body that is logically divided into regions separated by an “encapsulation boundary.” This idea was elaborated in a series of MIME RFCs, from RFC1341 (June 1992, MIME (Multipurpose Internet Mail Extensions) to RFC2045 (November 1996, MIME (Multipurpose Internet Mail Extensions) Part One: Format of Internet Message Bodies).

This series spells out the basic idea of MIME: a Content-Type: header can specify that a message body contains structured text, image data, other application-specific data, or a composite of these types.

The author of RFC1049 (March 1988, A Content-Type Header Field for Internet Messages) wrote, “A standardized Content-Type field allows mail reading systems to automatically identify the type of a structured message body and to process it for display accordingly.” This idea would become central not only to mailers and newsreaders, which use the Content-Type: header to identify and process rich content and attachments, but also to browsers. RFC2046 (November 1996, Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types) extended and revised RFC1049.

RFC2048 (November 1996, Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures) describes rules and procedures for registering new MIME content types.

A series beginning with RFC1872 ...