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Network Working Group                                            M. OhtaRequest for Comments: 1554                 Tokyo Institute of TechnologyCategory: Informational                                         K. Handa                                                                     ETL                                                           December 1993ISO-2022-JP-2: Multilingual Extension of ISO-2022-JPStatus 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.Introduction   This memo describes a text encoding scheme: "ISO-2022-JP-2", which is   used experimentally for electronic mail [RFC822] and network news   [RFC1036] messages in several Japanese networks.  The encoding is a   multilingual extension of "ISO-2022-JP", the existing encoding for   Japanese [2022JP].  The encoding is supported by an Emacs based   multilingual text editor: MULE [MULE].   The name, "ISO-2022-JP-2", is intended to be used in the "charset"   parameter field of MIME headers (see [MIME1] and [MIME2]).Description   The text with "ISO-2022-JP-2" starts in ASCII [ASCII], and switches   to other character sets of ISO 2022 [ISO2022] through limited   combinations of escape sequences.  All the characters are encoded   with 7 bits only.   At the beginning of text, the existence of an announcer sequence:   "ESC 2/0 4/1 ESC 2/0 4/6 ESC 2/0 5/10" is (though omitted) assumed.   Thus, characters of 94 character sets are designated to G0 and   invoked as GL.  C1 control characters are represented with 7 bits.   Characters of 96 character sets are designated to G2 and invoked with   SS2 (single shift two, "ESC 4/14" or "ESC N").   For example, the escape sequence "ESC 2/4 2/8 4/3" or "ESC $ ( C"   indicates that the bytes following the escape sequence are Korean KSC   characters, which are encoded in two bytes each.  The escape sequence   "ESC 2/14 4/1" or "ESC . A" indicates that ISO 8859-1 is designated   to G2. After the designation, the single shifted sequence "ESC 4/14   4/1" or "ESC N A" is interpreted to represent a character "A with   acute".Ohta & Handa                                                    [Page 1]

RFC 1554         Multilingual Extension of ISO-2022-JP     December 1993   The following table gives the escape sequences and the character sets   used in "ISO-2022-JP-2" messages. The reg# is the registration number   in ISO's registry [ISOREG].                              94 character sets      reg#  character set      ESC sequence                designated to      ------------------------------------------------------------------      6     ASCII              ESC 2/8 4/2      ESC ( B    G0      42    JIS X 0208-1978    ESC 2/4 4/0      ESC $ @    G0      87    JIS X 0208-1983    ESC 2/4 4/2      ESC $ B    G0      14    JIS X 0201-Roman   ESC 2/8 4/10     ESC ( J    G0      58    GB2312-1980        ESC 2/4 4/1      ESC $ A    G0      149   KSC5601-1987       ESC 2/4 2/8 4/3  ESC $ ( C  G0      159   JIS X 0212-1990    ESC 2/4 2/8 4/4  ESC $ ( D  G0                              96 character sets      reg#  character set      ESC sequence                designated to      ------------------------------------------------------------------      100   ISO8859-1          ESC 2/14 4/1     ESC . A    G2      126   ISO8859-7(Greek)   ESC 2/14 4/6     ESC . F    G2   For further information about the character sets and the escape   sequences, see [ISO2022] and [ISOREG].   If there is any G0 designation in text, there must be a switch to   ASCII or to JIS X 0201-Roman before a space character (but not   necessarily before "ESC 4/14 2/0" or "ESC N ' '") or control   characters such as tab or CRLF.  This means that the next line starts   in the character set that was switched to before the end of the   previous line.  Though the designation to JIS X 0201-Roman is allowed   for backward compatibility to "ISO-2022-JP", its use is discouraged.   Applications such as pagers and editors which randomly seek within a   text file encoded with "ISO-2022-JP-2" may assume that all the lines   begin with ASCII, not with JIS X 0201-Roman.   At the beginning of a line, information on G2 designation of the   previous line is cleared.  New designation must be given before a   character in 96 character sets is used in the line.   The text must end in ASCII designated to G0.   As the "ISO-2022-JP", and thus, "ISO-2022-JP-2", is designed to   represent English and modern Japanese, left-to-right directionality   is assumed if the text is displayed horizontally.   Users of "ISO-2022-JP-2" must be aware that some common transport   such as old Bnews can not relay a 7-bit value 7/15 (decimal 127),   which is used to encode, say, "y with diaeresis" of ISO 8859-1.Ohta & Handa                                                    [Page 2]

RFC 1554         Multilingual Extension of ISO-2022-JP     December 1993   Other restrictions are given in the Formal Syntax section below.Formal Syntax   The notational conventions used here are identical to those used in   STD 11,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.   message             = headers 1*(CRLF text)                                          ; see also [MIME1] "body-part"                                          ; note: must end in ASCII   text                = *(single-byte-char /                           g2-desig-seq /                           single-shift-char)                          [*segment                           reset-seq                           *(single-byte-char /                             g2-desig-seq /                             single-shift-char ) ]                                          ; note: g2-desig-seq must                                          ; precede single-shift-char   headers             = <see [RFC822] "fields" and [MIME1] "body-part">   segment             = single-byte-segment / double-byte-segment   single-byte-segment = single-byte-seq                         *(single-byte-char /                           g2-desig-seq /                           single-shift-char )   double-byte-segment = double-byte-seq                         *((one-of-94 one-of-94) /                           g2-desig-seq /                           single-shift-char )   reset-seq           = ESC "(" ( "B" / "J" )   single-byte-seq     = ESC "(" ( "B" / "J" )   double-byte-seq     = (ESC "$" ( "@" / "A" / "B" )) /Ohta & Handa                                                    [Page 3]

RFC 1554         Multilingual Extension of ISO-2022-JP     December 1993                         (ESC "$" "(" ( "C" / "D" ))   g2-desig-seq        = ESC "." ( "A" / "F" )   single-shift-seq    = ESC "N"   single-shift-char   = single-shift-seq one-of-96   CRLF                = CR LF                                                    ; ( 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.)   CR                  = <ASCII CR, carriage return>; (    15,      13.)   LF                  = <ASCII LF, linefeed>       ; (    12,      10.)   one-of-94           = <any one of 94 values>     ; (41-176, 33.-126.)   one-of-96           = <any one of 96 values>     ; (40-177, 32.-127.)   7BIT                = <any 7-bit value>          ; ( 0-177,  0.-127.)   single-byte-char    = <any 7BIT, including bare CR & bare LF, but NOT                          including CRLF, and not including ESC, SI, SO>MIME Considerations   The name given to the character encoding is "ISO-2022-JP-2". This   name is intended to be used in MIME messages as follows:      Content-Type: text/plain; charset=iso-2022-jp-2   The "ISO-2022-JP-2" 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 non-MIME-compliant software.   "ISO-2022-JP-2" may also be used in MIME headers.  Both "B" and "Q"   encoding could be useful with "ISO-2022-JP-2" text.Ohta & Handa                                                    [Page 4]

RFC 1554         Multilingual Extension of ISO-2022-JP     December 1993References   [ASCII] American National Standards Institute, "Coded character set           -- 7-bit American national standard code for information           interchange", ANSI X3.4-1986.   [ISO2022] International Organization for Standardization (ISO),             "Information processing -- ISO 7-bit and 8-bit coded             character sets -- Code extension techniques",             International Standard, Ref. No. ISO 2022-1986 (E).   [ISOREG] International Organization for Standardization (ISO),            "International Register of Coded Character Sets To Be Used            With Escape Sequences".   [MIME1] Borenstein, N., and N. Freed, "MIME  (Multipurpose Internet           Mail Extensions) Part One: Mechanisms for Specifying and           Describing the Format of Internet Message Bodies",RFC 1521,           September 1993.   [MIME2] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part           Two: Message Header Extensions for Non-ASCII Text",RFC 1522,           September 1993.   [RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text            Messages", STD 11,RFC 1522, UDEL, August 1982.   [RFC1036] Horton M., and R. Adams, "Standard for Interchange of             USENET Messages",RFC 1036, AT&T Bell Laboratories, Center             for Seismic Studies, December 1987.   [2022JP] Murai, J., Crispin, M., and E. van der Poel, "Japanese            Character Encoding for Internet Messages",RFC 1468, June            1993.   [MULE] Nishikimi, M., Handa, K., and S. Tomura, "Mule: MULtilingual          Enhancement to GNU Emacs", Proc. of INET'93, August, 1993.Acknowledgements   This memo is the result of discussion between various people in a   news group: fj.kanji and is reviewed by a mailing list: jp-msg   @iij.ad.jp.  The Authors wish to thank in particular Prof. Eiichi   Wada for his suggestions based on profound knowledge in ISO 2022 and   related standards.Ohta & Handa                                                    [Page 5]

RFC 1554         Multilingual Extension of ISO-2022-JP     December 1993Security Considerations   Security issues are not discussed in this memo.Authors' Addresses   Masataka Ohta   Tokyo Institute of Technology   2-12-1, O-okayama, Meguro-ku,   Tokyo 152, JAPAN   Phone: +81-3-5499-7084   Fax: +81-3-3729-1940   EMail: mohta@cc.titech.ac.jp   Ken'ichi Handa   Electrotechnical Laboratory   Umezono 1-1-4, Tsukuba,   Ibaraki 305, JAPAN   Phone: +81-298-58-5916   Fax: +81-298-58-5918   EMail: handa@etl.go.jpOhta & Handa                                                    [Page 6]