[RFC Home] [TEXT|PDF|HTML] [Tracker] [IPR] [Info page]

Tweet
This is a modified version of the Internet RFC suitable for machine-translating. Original version is available here: RFC1873
Ad

EXPERIMENTAL
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                      [Page 1]

RFC 1873                Access Type Content-ID             December 1995
2. The Content-ID Access Type

2.1 Registration Information
MIME access-type name: content-id

Required parameters: none

Optional parameters: none

Published specification: this document

Person & email address to contact for further information: Ed Levinson <ELevinson@accurate.com>

Additional requirements:

The content-id header of the access-type=content-id MIME entity must match (be identical to) exactly one content-id in the same message, excluding other access-type=content-id entities. Thus, the content-id access type can only occur within a multipart message and can refer to another body part anywhere in the same message.

A MIME User Agent (MUA) constructs the resultant MIME body part as described below. We call the access-type=content-id MIME entity the referring body part and the MIME body part to which it refers, the one with the matching content-id, the referenced body part. The MIME entity that results from content-id access type consists of:

(a) the referenced body part's content-type header,

(b) the referring body part's headers except its content-type header,

(c) any headers in the referenced body part not in the referring one,

(d) the line separating the headers from the body, and

(e) the referenced body part's body.
Levinson & Clark              Experimental                      [Page 2]

RFC 1873                Access Type Content-ID             December 1995
2.2 Example Usage
The following example shows a message that consists of two identical images.

MIME-Version: 1.0 Content-Type: Multipart/Mixed;
boundary=tiger-lily

--tiger-lily Content-Type: image/jpeg Content-ID: <950323.1552@XIson.com>

AAAcdb... --tiger-lily Content-type: Message/External-Body;
access-type=content-id
Content-ID: <950323.1552@XIson.com> Content-Description:
This body part is duplicated by reference

--tiger-lily--

The equivalent MIME entity for the second body part is:

--tiger-lily Content-Type: image/jpeg Content-ID: <950323.1552@XIson.com> Content-Description:
This body part is duplicated by reference

AAAcdb... --tiger-lily
3. Security Considerations
The content-id access-type does not impact the security of messages or systems. The referenced MIME entity may have security implications.
Levinson & Clark              Experimental                      [Page 3]

RFC 1873                Access Type Content-ID             December 1995
4. References
[822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, UDEL, August 1982.

[SGML] ISO 8879:1988, Information processing -- Text and office
systems -- Standard Generalized Markup Language (SGML).

[MIME] Borenstein, N., and N. Freed, "MIME (Multipurpose
Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, Bellcore, Innosoft, September 1993.
5. Authors' Addresses
Edward Levinson Accurate Information Systems, Inc.
2 Industrial Way
Eatontown, NJ 07724-2265 USA

Phone: +1 908 389 5550 EMail: <ELevinson@Accurate.com>


James Clark
90 Clarendon Road
London W11 2HR UK

EMail: <jjc@jclark.com>


















Levinson & Clark Experimental [Page 4]

Ad
Translate documents to 日本語, svenska, Nederlands, Deutsch, français, русский, italiano, español, Tiếng Việt, polski, português, 中文, українська, català, norsk, فارسی, suomi, Bahasa Indonesia, العربية, čeština, 한국어, Bahasa Melayu, magyar, română, српски and other languages.
inserted by FC2 system