Re: Unicode 4.0 in ICU demos

From: "Roozbeh Pournader" <roozbeh@xxxxxxxxxx>
> On Mon, 28 Apr 2003, Mark Davis wrote:
> 
> > BTW, the ICU demos have been all upgraded to Unicode 4.0, on 
> > http://oss.software.ibm.com/icu/demo/.
> > They include:
> > 
> > [...]
> >
> > IDNA Demo
> > This simple demo performs IDNA transformations as described in RFC 3490.
> 
> But isn't the IDNA repertoire limited to Unicode 3.2?!

Probably for now, until new characters are accepted in IDNA, which has always 
used only a approved subset of the Unicode/ISO10646 defined set, even with 
Unicode 3.2. IDNA defines, for security reasons, some other equivalences that 
are normative for use in domain names, even if they are not included in NFC/D 
and NFKC/KD data. (Look for exemple the additional equivalences for dashes, and 
Unicode standard characters whose usage is forbidden within IDNA, or 
equivalences added between similar letters belonging to distinct scripts within 
Unicode).

IDNA really adds restrictions based on the fact that two Unicode characters 
that are not canonically equivalent or compatibility equivalent, still have too 
similar glyphs in most fonts, and thus must be "unified" with additional 
equivalences.

A domain name is not an unrestricted general text, so it has additonal 
constraints that are out of scope of the Unicode standard which does not 
consider the security requirements for each application that uses it as a base 
standard.

Unicode 4.0 is still too new for IDNA. Give some time to IDNA authors to study 
the additions in Unicode 4, and publish a new subset of acceptable characters 
and new IDNA-canonical equivalences, or prohibitions.

There's nothing wrong however in the ICU announcement (IDNA is not a Unicode 
specification but a separate IETF/IEC technical standard), because it lists all 
demos that have been upgraded to the latest versions of each specification.



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