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Network Working Group Jun Murai |
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Internet Draft Mark Crispin |
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Erik van der Poel |
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25th August 1992 |
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Japanese Character Encoding for Internet Messages |
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Status of this Memo |
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This document is an Internet Draft. Internet Drafts are working |
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documents of the Internet Engineering Task Force (IETF), its Areas, |
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and its Working Groups. Note that other groups may also distribute |
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working documents as Internet Drafts. |
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Internet Drafts are draft documents valid for a maximum of six |
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months. Internet Drafts may be updated, replaced, or obsoleted by |
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other documents at any time. It is not appropriate to use Internet |
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Drafts as reference material or to cite them other than as a "working |
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draft" or "work in progress." |
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Please check the I-D abstract listing contained in each Internet |
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Draft directory to learn the current status of this or any other |
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Internet Draft. |
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This draft document will be submitted to the RFC editor as an |
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informational document. This document will expire before 2nd March |
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1993. Distribution of this memo is unlimited. Please send comments |
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to ietf-822@dimacs.rutgers.edu. |
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Introduction |
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This document describes the encoding used in plain text electronic |
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mail and network news in several Japanese networks. It was first |
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specified by and used in JUNET [JUNET]. The encoding is now also |
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widely used in Japanese IP communities. |
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This document provides a name for the encoding which is intended to |
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be used in the "charset" parameter field of MIME [MIME] messages. |
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This document only describes the encoding of plain text. The encoding |
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of other subtypes of text, such as rich text, is not discussed here. |
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Murai et al Expires 2nd March 1993 [Page 1] |
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Internet Draft Updated 25th August 1992 |
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Informal Description |
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The message body starts in ASCII, and switches to Japanese characters |
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through an escape sequence. For example, the escape sequence ESC $ B |
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(three bytes) indicates that the bytes following this escape sequence |
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are Japanese characters, which are encoded in two bytes each. To |
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switch back to ASCII, the escape sequence ESC ( B is used. |
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The following table gives the escape sequences and the character sets |
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used in JUNET messages. |
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ESC ( B ASCII |
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ESC ( J JIS X 0201-1976 (left-hand part) |
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ESC $ @ JIS X 0208-1978 |
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ESC $ B JIS X 0208-1983 |
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The left-hand part of JIS X 0201-1976 is identical to ASCII except |
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for backslash (\) and tilde (~). The backslash is replaced by the Yen |
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sign, and the tilde is replaced by macron (overline). This set is |
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Japan's national variant of ISO 646. |
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The JIS X 0208 character sets consist of Kanji, Hiragana, Katakana |
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and some other symbols and characters. Each character takes up two |
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bytes. |
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For further details about the JIS Japanese national character set |
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standards, refer to the JIS standards themselves. For further |
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information about the escape sequences, see ISO 2022 [ISO2022]. |
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If there are JIS X 0208 characters on a line, there must be a switch |
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to ASCII or to the left-hand part of JIS X 0201 before the end of the |
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line (i.e. before the CRLF). This means that the next line starts in |
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the character set that was switched to before the end of the previous |
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line. Other restrictions are given in the Formal Description below. |
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Formal Description |
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This section provides a formal description of the JUNET encoding. In |
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the event that this description is not consistent with the above |
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informal description, this formal description shall take precedence. |
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The notational conventions used here are identical to those used in |
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RFC 822 [RFC822]. |
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The * (asterisk) convention is as follows: |
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l*m something |
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Murai et al Expires 2nd March 1993 [Page 2] |
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Internet Draft Updated 25th August 1992 |
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meaning at least l and at most m somethings, with l and m taking |
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default values of 0 and infinity, respectively. |
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line = *text *1( *segment single-byte-seq *text ) CRLF |
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segment = single-byte-segment / double-byte-segment |
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single-byte-segment = single-byte-seq 1*text |
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double-byte-segment = double-byte-seq 1*( one-of-94 one-of-94 ) |
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single-byte-seq = ESC "(" ( "B" / "J" ) |
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double-byte-seq = ESC "$" ( "@" / "B" ) |
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; ( Octal, Decimal.) |
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ESC = <ISO 2022 ESC, escape> ; ( 33, 27.) |
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one-of-94 = <any char in 94-char set> ; (41-176, 33.-126.) |
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CHAR = <any ASCII character> ; ( 0-177, 0.-127.) |
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text = <any CHAR, including bare |
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CR & bare LF, but NOT |
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including CRLF> |
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Additional restrictions that are difficult to describe in the above |
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are as follows. |
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Adjacent segments should have different escape sequences. For |
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example, the following is not recommended: |
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ESC $ B .... ESC $ B .... |
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MIME Considerations |
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The name given to the JUNET character encoding is "ISO-2022-JP". This |
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name is intended to be used in MIME messages as follows: |
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Content-Type: text/plain; charset=iso-2022-jp |
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The JUNET encoding is already in 7-bit form, so it is not necessary |
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to use a Content-Transfer-Encoding header. It should be noted that |
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applying the Base64 or Quoted-Printable encoding will render the |
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Murai et al Expires 2nd March 1993 [Page 3] |
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Internet Draft Updated 25th August 1992 |
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message unreadable in current JUNET software. |
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Background Information |
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The JUNET encoding was described in the JUNET User's Guide [JUNET] |
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(JUNET Riyou No Tebiki Dai Ippan). |
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The encoding is based on the particular usage of ISO 2022 [ISO2022] |
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announced by 4/1. However, the escape sequence normally used for this |
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announcement is not included in JUNET messages. |
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References |
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[ISO2022] International Organization for Standardization (ISO), |
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"Information processing -- ISO 7-bit and 8-bit coded character sets |
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-- Code extension techniques", International Standard, 1986, Ref. No. |
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ISO 2022-1986 (E) |
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[JUNET] JUNET Riyou No Tebiki Sakusei Iin Kai (JUNET User's Guide |
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Drafting Committee), "JUNET Riyou No Tebiki (Dai Ippan)" ("JUNET |
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User's Guide (First Edition)"), February 1988 |
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[MIME] Nathaniel Borenstein and Ned Freed, "MIME (Multipurpose |
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Internet Mail Extensions): Mechanisms for Specifying and Describing |
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the Format of Internet Message Bodies", Proposed (Internet) standard, |
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June 1992, rfc1341 |
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[RFC822] David H. Crocker, "Standard for the Format of ARPA Internet |
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Text Messages", Internet standard, August 1982, rfc822 |
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Security Considerations |
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Security considerations are not discussed in this memo. |
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Acknowledgements |
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Many people assisted in drafting this document. The authors wish to |
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thank in particular Akira Kato, Masahiro Sekiguchi and Ken'ichi |
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Handa. |
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Murai et al Expires 2nd March 1993 [Page 4] |
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Internet Draft Updated 25th August 1992 |
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Authors' Addresses |
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Jun Murai |
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Keio University |
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5322 Endo, Fujisawa |
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Fujisawa 252 Japan |
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Fax: +81 (466) 49-1101 |
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EMail: jun@wide.ad.jp |
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Mark Crispin |
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Panda Programming |
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6158 Lariat Loop NE |
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Bainbridge Island, WA 98110-2098 |
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USA |
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Phone: +1 (206) 842-2385 |
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EMail: MRC@PANDA.COM |
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Erik M. van der Poel |
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A-105 Park Avenue |
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4-4-10 Ohta, Kisarazu |
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Chiba 292 Japan |
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Phone: +81 (438) 22-5836 |
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Fax: +81 (438) 22-5837 |
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EMail: erik@poel.juice.or.jp |
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Murai et al Expires 2nd March 1993 [Page 5] |
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