Folks,
A new draft of the iso-2022-jp document has been prepared and is
included below. I have added "diff marks" on the right to indicate
changes since the previous draft: "!" means modification, "+" means
addition, and "-" means deletion. The review period is another two
weeks (also on the Japanese newsgroup fj.kanji).
Regards,
Erik
Network Working Group Jun Murai
Internet Draft Mark Crispin
Erik van der Poel
10th September 1992
Japanese Character Encoding for Internet Messages
Status of this Memo
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts.
Internet Drafts are draft documents valid for a maximum of six
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draft" or "work in progress."
Please check the I-D abstract listing contained in each Internet
Draft directory to learn the current status of this or any other
Internet Draft.
This draft document will be submitted to the RFC editor as an
informational document. This document will expire before 10th March
1993. Distribution of this memo is unlimited. Please send comments
to ietf-822(_at_)dimacs(_dot_)rutgers(_dot_)edu(_dot_)
Introduction
This document describes the encoding used in the bodies of electronic !
mail and network news messages in several Japanese networks. It was !
first specified by and used in JUNET [JUNET]. The encoding is now
also widely used in Japanese IP communities.
This document provides a name for the encoding which is intended to
be used in the "charset" parameter field of MIME [MIME] messages and !
RFC 1342 [RFC1342] headers. !
This document only describes the encoding of plain text. The encoding
of other subtypes of text, such as rich text, is not discussed here.
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Description !
The message body starts in ASCII, and switches to Japanese characters
through an escape sequence. For example, the escape sequence ESC $ B
(three bytes, hexadecimal values: 1B 24 42) indicates that the bytes !
following this escape sequence are Japanese characters, which are
encoded in two bytes each. To switch back to ASCII, the escape
sequence ESC ( B is used.
The following table gives the escape sequences and the character sets
used in JUNET messages.
ESC ( B ASCII
ESC ( J JIS X 0201-1976 ("Roman" set) !
ESC $ @ JIS X 0208-1978
ESC $ B JIS X 0208-1983
The "Roman" character set of JIS X 0201-1976 is identical to ASCII !
except for backslash (\) and tilde (~). The backslash is replaced by
the Yen sign, and the tilde is replaced by macron (overline). This
set is Japan's national variant of ISO 646.
The JIS X 0208 character sets consist of Kanji, Hiragana, Katakana
and some other symbols and characters. Each character takes up two
bytes.
For further details about the JIS Japanese national character set
standards, refer to the JIS standards themselves. For further
information about the escape sequences, see ISO 2022 [ISO2022].
If there are JIS X 0208 characters on a line, there must be a switch
to ASCII or to the "Roman" set of JIS X 0201 before the end of the !
line (i.e. before the CRLF). This means that the next line starts in
the character set that was switched to before the end of the previous
line. Other restrictions are given in the Formal Syntax below. !
Formal Syntax !
-
The notational conventions used here are identical to those used in
RFC 822 [RFC822].
The * (asterisk) convention is as follows:
l*m something
meaning at least l and at most m somethings, with l and m taking
default values of 0 and infinity, respectively.
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line = *text *1( *segment single-byte-seq *text ) CRLF
segment = single-byte-segment / double-byte-segment
single-byte-segment = single-byte-seq 1*text
double-byte-segment = double-byte-seq 1*( one-of-94 one-of-94 )
single-byte-seq = ESC "(" ( "B" / "J" )
double-byte-seq = ESC "$" ( "@" / "B" )
; ( Octal, Decimal.)
ESC = <ISO 2022 ESC, escape> ; ( 33, 27.)
SI = <ISO 2022 SI, shift-in> ; ( 17, 15.) +
SO = <ISO 2022 SO, shift-out> ; ( 16, 14.) +
one-of-94 = <any char in 94-char set> ; (41-176, 33.-126.)
CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
text = <any CHAR, including bare CR & bare LF, but NOT !
including CRLF, and not including ESC, SI, SO> !
-
MIME and RFC 1342 Considerations !
The name given to the JUNET character encoding is "ISO-2022-JP". This
name is intended to be used in MIME messages as follows:
Content-Type: text/plain; charset=iso-2022-jp
The JUNET encoding is already in 7-bit form, so it is not necessary
to use a Content-Transfer-Encoding header. It should be noted that
applying the Base64 or Quoted-Printable encoding will render the
message unreadable in current JUNET software.
The name ISO-2022-JP may also be used in RFC 1342 headers, though in +
this case, the text should be encoded using either the "B" or "Q" +
encoding, to avoid getting damaged by header-processing software. As +
ISO-2022-JP text often contains many bytes that have a special +
meaning in headers, it is probably easier to use the "B" encoding, +
rather than trying to determine which particular byte values need "Q" +
encoding. +
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Background Information
The JUNET encoding was described in the JUNET User's Guide [JUNET]
(JUNET Riyou No Tebiki Dai Ippan).
The encoding is based on the particular usage of ISO 2022 announced !
by 4/1 (see [ISO2022] for details). However, the escape sequence !
normally used for this announcement is not included in JUNET
messages.
The so-called half-width (hankaku) Katakana, that is, the Kana set of +
JIS X 0201-1976, are not used in JUNET messages. +
In the past, some systems erroneously used the escape sequence ESC ( +
H in JUNET messages. This escape sequence is officially registered +
for a Swedish character set, and should not be used in JUNET +
messages. +
Some systems do not distinguish between ESC ( B and ESC ( J or +
between ESC $ @ and ESC $ B for display. However, when relaying a +
message to another system, the escape sequences must not be altered +
in any way. +
The human user (not implementor) should try to keep lines within 80 +
display columns, or, preferably, within 75 (or so) columns, to allow +
insertion of ">" at the beginning of each line in excerpts. Each JIS +
X 0208 character takes up two columns, and the escape sequences do +
not take up any columns. The implementor is reminded that JIS X 0208 +
characters take up two bytes and should not be split in the middle to +
break lines for displaying, etc. +
The JIS X 0208 standard was revised in 1990, to add two characters at +
the end of the table. Although ISO 2022 specifies special additional +
escape sequences to indicate the use of revised character sets, it is +
suggested here not to make use of this special escape sequence in +
ISO-2022-JP text, even if the two characters added to JIS X 0208 in +
1990 are used. +
References
[ISO2022] International Organization for Standardization (ISO),
"Information processing -- ISO 7-bit and 8-bit coded character sets
-- Code extension techniques", International Standard, 1986, Ref. No.
ISO 2022-1986 (E)
[JUNET] JUNET Riyou No Tebiki Sakusei Iin Kai (JUNET User's Guide
Drafting Committee), "JUNET Riyou No Tebiki (Dai Ippan)" ("JUNET
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User's Guide (First Edition)"), February 1988
[MIME] Nathaniel Borenstein and Ned Freed, "MIME (Multipurpose
Internet Mail Extensions): Mechanisms for Specifying and Describing
the Format of Internet Message Bodies", Proposed (Internet) standard,
June 1992, rfc1341
[RFC822] David H. Crocker, "Standard for the Format of ARPA Internet
Text Messages", Internet standard, August 1982, rfc822
[RFC1342] Keith Moore, "Representation of Non-ASCII Text in Internet +
Message Headers", Proposed (Internet) standard, June 1992, rfc1342 +
Security Considerations
Security considerations are not discussed in this memo.
Acknowledgements
Many people assisted in drafting this document. The authors wish to
thank in particular Akira Kato, Masahiro Sekiguchi and Ken'ichi
Handa.
Authors' Addresses
Jun Murai
Keio University
5322 Endo, Fujisawa
Kanagawa 252 Japan !
Fax: +81 (466) 49-1101
EMail: jun(_at_)wide(_dot_)ad(_dot_)jp
Mark Crispin
Panda Programming
6158 Lariat Loop NE
Bainbridge Island, WA 98110-2098
USA
Phone: +1 (206) 842-2385
EMail: MRC(_at_)PANDA(_dot_)COM
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Erik M. van der Poel
A-105 Park Avenue
4-4-10 Ohta, Kisarazu
Chiba 292 Japan
Phone: +81 (438) 22-5836
Fax: +81 (438) 22-5837
EMail: erik(_at_)poel(_dot_)juice(_dot_)or(_dot_)jp
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