RFC 1873 (rfc1873) - Page 1 of 4

Message/External-Body Content-ID Access Type

Network Working Group                                        E. Levinson
Request for Comments: 1873            Accurate Information Systems, Inc.
Category: Experimental                                          J. Clark
                                                           December 1995


              Message/External-Body Content-ID Access Type

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Abstract

   When using MIME [MIME] to encapsulate a structured object that
   consist of many elements, for example an SGML [SGML] document, a
   single element may occur several times.  An encapsulation normally
   maps each of the structured objects elements to a MIME entity.  It is
   useful to include elements that occur multiple time exactly once.  To
   accomplish that and to preserve the object structure it is desirable
   to unambiguously refer to another body part of the same message.

   The existing MIME Content-Type Message/External-Body access-types
   allow a MIME entity (body-part) to refer to an object that is not in
   the message by specifying how to access that object.  The Content-ID
   access method described in this document provides the capability to
   refer to an object within the message.

1. Introduction

   Consider a MIME multipart entity several of whose body parts contain
   the same data (body) but different parameters or Content-* headers.
   Representing those body parts without duplicating the data in each
   one promotes efficient use of resources (bandwidth and storage
   space).  To achieve these benefits an access-type is defined that
   permits one message part to refer to another one in the same message.












Levinson & Clark              Experimental