- From: Francois Yergeau <yergeau@alis.com>
- Date: Wed, 05 Feb 1997 21:52:36 -0500
- To: David Goldsmith <goldsmith@apple.com>
- Cc: IETF Charsets Mailing List <ietf-charsets@INNOSOFT.COM>, Unicode Core List <unicore@Unicode.ORG>
À 11:29 05-02-97 -0800, David Goldsmith a écrit : >FYI > >If there are no objections I will try to advance this to RFC >(Experimental) status in two weeks, then register "UTF-7". Good. Some comments: >Abstract > >... > This document describes a transformation format of Unicode that > contains only 7-bit ASCII characters and ... This is misleading. UTF-7 encodes UCS *characters* using only 7-bit ASCII-valued *octets*. >Overview > > UTF-7 encodes Unicode characters as US-ASCII, together with... Same remark. > UTF-7 should normally be used only in the context of 7 bit > transports, such as mail and news. In other contexts, straight > Unicode or UTF-8 is preferred. Great! Please remove "and news", however. News are in effect 8-bit clean; many newsgroups use 8-bits charsets routinely, and all widespread implementations are 8-bit clean. Even the IAB charset workshop report (draft-weider-iab...) recognizes that. >UTF-7 Definition > > A UTF-7 stream represents 16-bit Unicode characters in 7-bit US-ASCII > as follows: Sugg.: "represents ... using 7-bit ASCII-valued octets as follows" > Unicode is encoded using Modified Base64 by first converting > Unicode 16-bit quantities to an octet stream (with the most > significant octet first). Surrogate pairs (UTF-16) are converted > by treating each half of the pair as a separate 16 bit quantity > (i.e., no special treatment). Text with an odd number of octets is > ill-formed. Since the draft refers to 10646 as well as Unicode, it might be worth saying that UCS-4 characters outside of the range accessible through UTF-16 cannot be transformed by UTF-7. > 2. Most non-European alphabet-based languages (e.g., Greek)... The Greek will sure be surprised to learn that they are not Europeans :-) Regards, -- François Yergeau <yergeau@alis.com> Alis Technologies Inc., Montréal Tél : +1 (514) 747-2547 Fax : +1 (514) 747-2561 --Boundary (ID uEbHHWxWEwCKT9wM3evJ5w)
Received on Wednesday, 5 February 1997 18:52:43 UTC