rfc2231.txt

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RFC 2231         MIME Value and Encoded Word Extensions    November 1997


    (4)   The first segment of a continuation MUST be encoded if
          language and character set information are given.

    (5)   If the first segment of a continued parameter value is
          encoded the language and character set field delimiters
          MUST be present even when the fields are left blank.

5.  Language specification in Encoded Words

   RFC 2047 provides support for non-US-ASCII character sets in RFC 822
   message header comments, phrases, and any unstructured text field.
   This is done by defining an encoded word construct which can appear
   in any of these places.  Given that these are fields intended for
   display, it is sometimes necessary to associate language information
   with encoded words as well as just the character set.  This
   specification extends the definition of an encoded word to allow the
   inclusion of such information.  This is simply done by suffixing the
   character set specification with an asterisk followed by the language
   tag.  For example:

          From: =?US-ASCII*EN?Q?Keith_Moore?= <[e-mail]>

6.  IMAP4 Handling of Parameter Values

   IMAP4 [RFC-2060] servers SHOULD decode parameter value continuations
   when generating the BODY and BODYSTRUCTURE fetch attributes.

7.  Modifications to MIME ABNF

   The ABNF for MIME parameter values given in RFC 2045 is:

   parameter := attribute "=" value

   attribute := token
                ; Matching of attributes
                ; is ALWAYS case-insensitive.

   This specification changes this ABNF to:

   parameter := regular-parameter / extended-parameter

   regular-parameter := regular-parameter-name "=" value

   regular-parameter-name := attribute [section]

   attribute := 1*attribute-char





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RFC 2231         MIME Value and Encoded Word Extensions    November 1997


   attribute-char := <any (US-ASCII) CHAR except SPACE, CTLs,
                     "*", "'", "%", or tspecials>

   section := initial-section / other-sections

   initial-section := "*0"

   other-sections := "*" ("1" / "2" / "3" / "4" / "5" /
                          "6" / "7" / "8" / "9") *DIGIT)

   extended-parameter := (extended-initial-name "="
                          extended-value) /
                         (extended-other-names "="
                          extended-other-values)

   extended-initial-name := attribute [initial-section] "*"

   extended-other-names := attribute other-sections "*"

   extended-initial-value := [charset] "'" [language] "'"
                             extended-other-values

   extended-other-values := *(ext-octet / attribute-char)

   ext-octet := "%" 2(DIGIT / "A" / "B" / "C" / "D" / "E" / "F")

   charset := <registered character set name>

   language := <registered language tag [RFC-1766]>

   The ABNF given in RFC 2047 for encoded-words is:

   encoded-word := "=?" charset "?" encoding "?" encoded-text "?="

   This specification changes this ABNF to:

   encoded-word := "=?" charset ["*" language] "?" encoded-text "?="

8.  Character sets which allow specification of language

   In the future it is likely that some character sets will provide
   facilities for inline language labeling. Such facilities are
   inherently more flexible than those defined here as they allow for
   language switching in the middle of a string.







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RFC 2231         MIME Value and Encoded Word Extensions    November 1997


   If and when such facilities are developed they SHOULD be used in
   preference to the language labeling facilities specified here. Note
   that all the mechanisms defined here allow for the omission of
   language labels so as to be able to accommodate this possible future
   usage.

9.  Security Considerations

   This RFC does not discuss security issues and is not believed to
   raise any security issues not already endemic in electronic mail and
   present in fully conforming implementations of MIME.

10.  References

   [RFC-822]
        Crocker, D., "Standard for the Format of ARPA Internet
        Text Messages", STD 11, RFC 822 August 1982.

   [RFC-1766]
        Alvestrand, H., "Tags for the Identification of
        Languages", RFC 1766, March 1995.

   [RFC-2045]
        Freed, N., and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message
        Bodies", RFC 2045, December 1996.

   [RFC-2046]
        Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046,
        December 1996.

   [RFC-2047]
        Moore, K., "Multipurpose Internet Mail Extensions (MIME)
        Part Three: Representation of Non-ASCII Text in Internet
        Message Headers", RFC 2047, December 1996.

   [RFC-2048]
        Freed, N., Klensin, J. and J. Postel, "Multipurpose
        Internet Mail Extensions (MIME) Part Four: MIME
        Registration Procedures", RFC 2048, December 1996.

   [RFC-2049]
        Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Five: Conformance Criteria and
        Examples", RFC 2049, December 1996.





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RFC 2231         MIME Value and Encoded Word Extensions    November 1997


   [RFC-2060]
        Crispin, M., "Internet Message Access Protocol - Version
        4rev1", RFC 2060, December 1996.

   [RFC-2119]
        Bradner, S., "Key words for use in RFCs to Indicate
        Requirement Levels", RFC 2119, March 1997.

   [RFC-2130]
        Weider, C., Preston, C., Simonsen, K., Alvestrand, H.,
        Atkinson, R., Crispin, M., and P. Svanberg, "Report from the
        IAB Character Set Workshop", RFC 2130, April 1997.

   [RFC-2183]
        Troost, R., Dorner, S. and K. Moore, "Communicating
        Presentation Information in Internet Messages:  The
        Content-Disposition Header", RFC 2183, August 1997.

11.  Authors' Addresses

   Ned Freed
   Innosoft International, Inc.
   1050 Lakes Drive
   West Covina, CA 91790
   USA

   Phone: [phone]
   Fax:   [phone]
   EMail: [e-mail]


   Keith Moore
   Computer Science Dept.
   University of Tennessee
   107 Ayres Hall
   Knoxville, TN 37996-1301
   USA

   EMail: [e-mail]












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RFC 2231         MIME Value and Encoded Word Extensions    November 1997


12.  Full Copyright Statement

   Copyright (C) The Internet Society (1997).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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