X.400 Use of Extended Character Sets (RFC1502)
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
Since 1988, X.400 has had the capacity for carrying a large number of different character sets in a message by using the body part "GeneralText" defined by ISO/IEC 10021-7.
Network Working Group H. Alvestrand
Request for Comments: 1502 SINTEF DELAB
X.400 Use of Extended Character Sets
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
Since 1988, X.400 has had the capacity for carrying a large number of
different character sets in a message by using the body part
"GeneralText" defined by ISO/IEC 10021-7.
Since 1992, the Internet also has the means of passing around
messages containing multiple character sets, by using the mechanism
defined in RFC-MIME.
This RFC defines a suggested method of using "GeneralText" in order
to harmonize as much as possible the usage of this body part.
2. General principles
The target of this memo is to define a way of using existing
standards to achieve:
(1) in the short term, a standard for sending E-mail in the
European languages (Latin letters with European accents,
Greek and Cyrillic)
(2) in the medium term, extending this to cover the Hebrew and
Arabic character sets
(3) in the long term, opening up true international E-mail by
allowing the full character set specified in ISO-10646 to be
The author believes that this document gives a specification that can
easily accomodate the use of any character set in the ISO registry,
and, by giving guidance rules for choosing character sets, will help
2.2. Families of character sets
2.2.1. ISO 6937/T.61
ISO 6937 is a code technique used and recommended in T.51 and T.101
(Teletex and Videotex service) and in X.500, providing a repertoire
of 333 characters from the Latin script by use of non- spacing
diacritical marks. It corresponds closely to CCITT recommendation
The problem with that technique is that the character stream comes in
two modes, i.e., some characters are coded with one byte and some
with two (composite characters). This makes information processing
systems such as an E-mail UA or GW more complex.
It is also not extensible to other languages like Korean or Chinese,
or even Greek, without invoking the character set switching
techniques of ISO 2022.
2.2.2. ISO 8859
ISO 8859 defines a set of character sets, each suitable for use in
some group of languages. Each character in ISO 8859 is coded in a
There are currently 11 parts of ISO 8859, plus a "supplementary" set,
registered as ISO IR 154. Most languages using single-byte characters
can be written in one or another of the ISO 8859 sets. There are
sets covering ...