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Re: IDN (was Did anyone tell Microsoft yet?)

2002-05-02 09:12:48

In <200205011656(_dot_)g41Gu1e19565(_at_)astro(_dot_)cs(_dot_)utk(_dot_)edu> 
Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu> writes:


The chief problem with using IDNA in any User Agent is the Nameprep
operation (see my message to this list a couple of days ago). It requires
the presence of large tables of Unicode transformations and forbidden
characters. These tables may well change over time as Unicode evolves. 

this problem isn't specific to IDNA. it exists with any use of Unicode 
to represent strings that need to be compared for equivalence.

Not necessarily. We are dealing with twp forms of normalization in
Nameprep. One to Normalization Form C or KC, and one from upper case to
lower case. Generally speaking, there are two schools of thought as to
when Normalization should be done: Early and Late.

The official advice of the Unicode people is to do it Early (see
draft-duerst-i18n-norm-04.txt). My view is that that should be as early as
the keyboard driver in the operating system, so that applications can
assume, without further testing, that textual data is already normalized.
However, that is not appropriate for upper to lower case normalization.

The view of the IDNA people seems to be to do it Late, i.e. just before
the call of gethostbyname, or even inside gethostbyname eventually.

The point is that "ordinary applications" are not supposed to care. IMO
User Agents are ordinary applications. However, that may me too simplistic,
but the only way to move forward is to look at particular cases and see
which approaches appear to have the best chance of success. The view I
have been trying to put across is that the point where normalization
occurs is the weakest link in the system, and that therefore such points
should be concentrated so that they are few in number and easily fixed.
From that POV, User Agents fail on both counts.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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