Using Unicode with MIME (RFC1641)
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
D. Goldsmith: AUTHOR [+1]
This document specifies the usage of Unicode within MIME. This memo defines an Experimental Protocol for the Internet community.
Network Working Group D. Goldsmith Request for Comments: 1641 M. Davis Category: Experimental Taligent, Inc. July 1994
Using Unicode with MIME
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. Distribution of this memo is unlimited.
The Unicode Standard, version 1.1, and ISO/IEC 10646-1:1993(E) jointly define a 16 bit character set (hereafter referred to as Unicode) which encompasses most of the world’s writing systems. However, Internet mail (STD 11, RFC 822) currently supports only 7- bit US ASCII as a character set. MIME (RFC 1521 and RFC 1522) extends Internet mail to support different media types and character sets, and thus could support Unicode in mail messages. MIME neither defines Unicode as a permitted character set nor specifies how it would be encoded, although it does provide for the registration of additional character sets over time.
This document specifies the usage of Unicode within MIME.
Since Unicode is starting to see widespread commercial adoption, users will want a way to transmit information in this character set in mail messages and other Internet media. Since MIME was expressly designed to allow such extensions and is on the standards track for the Internet, it is the most appropriate means for encoding Unicode. RFC 1521 and RFC 1522 do not define Unicode as an allowed character set, but allow registration of additional character sets.
In addition to allowing use of Unicode within MIME bodies, another goal is to specify a way of using Unicode that allows text which consists largely, but not entirely, of US-ASCII characters to be represented in a way that can be read by mail clients who do not understand Unicode. This is in keeping with the philosophy of MIME. Such an encoding is described in another document, "UTF-7: A Mail Safe Transformation Format of Unicode" [UTF-7].
Goldsmith & Davis [Page 1]
RFC 1641 Using Unicode with MIME July 1994
Several ways of using Unicode are possible. This document specifies both guidelines for use of Unicode within MIME, and a specific usage. The usage specified in this document is a straightforward use of Unicode as specified in "The Unicode Standard, Version 1.1".
This encoding is intended for situations where sender and recipient do not want to do a lot of processing, when the text does not consist primarily of characters from the US-ASCII character set, or when sender and receiver are known in advance to support Unicode.
Another encoding is intended for situations where the text consists primarily of US-ASCII, with occasional characters from other parts of Unicode. This encoding allows the US-ASCII portion to be read by all recipients without having to support Unicode. This encoding is specified in another document, "UTF-7: A Mail Safe Transformation Format of Unicode" [UTF-7].
Finally, in keeping with the principles set forth in RFC 1521, text which ca...