RFC 1556 (rfc1556) - Page 1 of 3

Handling of Bi-directional Texts in MIME

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Network Working Group                                      H. Nussbacher
Request for Comments: 1556                      Israeli Inter-University
Category: Informational                                  Computer Center
                                                           December 1993


                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.

Abstract

   This document describes the format and syntax of the "direction"
   keyword to be used with bi-directional texts in MIME.

Description

   The MIME standards (RFC 1521 and 1522) defined methods for
   transporting non-ASCII data via a standard RFC 822 e-mail system.
   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





Nussbacher
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