Network Working Group H. Nussbacher
Request for Comments: 1556
Category: Informational Computer Center
Handling of Bi-directional Texts in MIME
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
This document describes the format and syntax of the "direction"
keyword to be used with bi-directional texts in MIME.
The MIME standards (RFC 1521
and 1522) defined methods for
transporting non-ASCII data via a standard RFC822
Specifically, the Content-type field allows for the inclusion of any
ISO language such as Arabic (ISO-8859-6) or Hebrew (ISO-8859-8). The
problem is that the these two languages are read from right to left
and can have bi-directional data such as mixed Hebrew and English on
the same line.
Fortunately, ECMA (European Computer Manufacturers Association) has
tackled this problem previously and has issued a technical report
called "Handling of Bi-Directional Texts". ECMA TR/53, as it is
called, was used to update the Standard ECMA-48 which in turn was
used as the basis for ISO/IEC 6429 which was adopted under a special
"fast track procedure". It is based on this information that a new
character set is being defined which will indicate that the bi-
directional message is either encoded in implicit mode or explicit
mode. The default is visual mode which requires no special character
set other than the standard ones previously defined by ISO-8859.
Examples of new character sets for bi-directionality support:
Content-type: text/plain; charset=ISO-8859-6-e
Content-type: text/plain; charset=ISO-8859-6-i
Content-type: text/plain; charset=ISO-8859-8-e
Content-type: text/plain; charset=ISO-8859-8-i
[ISO-8859] Information Processing -- 8-bit Single-Byte Coded
Graphic Character Sets, Part 8: Latin/Hebrew alphabet,
ISO 8859-8, 1988.
] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822
, UDEL, August 1982.
] Borenstein N., and N. Freed, "MIME (Multipurpose
Internet Mail Extensions) Part One: Mechanisms for
Specifying and Describing the Format of Internet
Message Bodies", Bellcore, Innosoft, September 1993.
] Moore K., "MIME Part Two: Message Header Extensions for
Non-ASCII Text", University of Tennessee,
Security issues are not discussed in this memo.
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