12. Changes from RFC 2279

o Restricted the range of characters to 0000-10FFFF (the UTF-16 accessible range).

o Made Unicode the source of the normative definition of UTF-8, keeping ISO/IEC 10646 as the reference for characters.

o Straightened out terminology. UTF-8 now described in terms of an encoding form of the character number. UCS-2 and UCS-4 almost disappeared.

o Turned the note warning against decoding of invalid sequences into a normative MUST NOT.

o Added a new section about the UTF-8 BOM, with advice for protocols.

o Removed suggested UNICODE-1-1-UTF-8 MIME charset registration.

o Added an ABNF syntax for valid UTF-8 octet sequences

o Expanded Security Considerations section, in particular impact of Unicode normalization

13. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[ISO.10646] International Organization for Standardization, "Information Technology - Universal Multiple-octet coded Character Set (UCS)", ISO/IEC Standard 10646, comprised of ISO/IEC 10646-1:2000, "Information technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane", ISO/IEC 10646-2:2001, "Information technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 2: Supplementary Planes" and ISO/IEC 10646- 1:2000/Amd 1:2002, "Mathematical symbols and other characters".

[UNICODE] The Unicode Consortium, "The Unicode Standard -- Version 4.0", defined by The Unicode Standard, Version 4.0 (Boston, MA, Addison-Wesley, 2003. ISBN 0-321-18578-1), April 2003, <http://www.unicode.org/unicode/standard/ versions/enumeratedversions.html#Unicode_4_0_0>.

14. Informative References

[CESU-8] Phipps, T., "Unicode Technical Report #26: Compatibility Encoding Scheme for UTF-16: 8-Bit (CESU-8)", UTR 26, April 2002, <http://www.unicode.org/unicode/reports/tr26/>.

[FSS_UTF] X/Open Company Ltd., "X/Open Preliminary Specification -- File System Safe UCS Transformation Format (FSS-UTF)", May 1993, <http://wwwold.dkuug.dk/jtc1/sc22/wg20/docs/ N193-FSS-UTF.pdf>.

[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.

[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997.

[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration Procedures", BCP 19, RFC 2978, October 2000.

[UAX15] Davis, M. and M. Duerst, "Unicode Standard Annex #15: Unicode Normalization Forms", An integral part of The Unicode Standard, Version 4.0.0, April 2003, <http:// www.unicode.org/unicode/reports/tr15>.

[US-ASCII] American National Standards Institute, "Coded Character Set - 7-bit American Standard Code for Information Interchange", ANSI X3.4, 1986.

15. URIs

[1] <http://www.unicode.org/unicode/standard/policies.html>

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17. Author's Address

Francois Yergeau Alis Technologies 100, boul. Alexis-Nihon, bureau 600 Montreal, QC H4M 2P2 Canada

Phone: +1 514 747 2547 Fax: +1 514 747 2561 EMail: fyergeau@alis.com

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