Re: Matching and comparison

[Paul Hoffman / IMC <phoffman@imc.org>]

At 05:26 PM 1/18/00 +0900, Martin J. Duerst wrote:
>At 16:22 00/01/17 +0800, James Seng wrote:
> > Paul Hoffman / IMC wrote:
> > > I think you are trying to mandate case-insensitivity here. That's good
> > > in theory and bad in practice for international characters. There are
> > > examples of letters whose case conversion are different for different
> > > written languages. If we want to require case-insensitivity, we
> > > have to point to a single conversion table for all characters.
> >
> > Preciesly why we need to discuss this further. I am sure there are 
> people who
> > has different view on case sensitivity. It can get very religous.
>
>There is no need to have a single conversion table if this is
>handled e.g. at the client. The Microsoft I-D proposed that.

Maybe I am misunderstanding your intention here, but this seems like a 
recipe for breaking the uniqueness rule. If my client coverts case 
differently than your client does, and we both try to resolve a domain 
name, the resolver will get two different queries and thus will give two 
different answers.

Any conversion (case, ligature folding, punctuation folding, ...) from what 
the user enters into a client to what the client asks for resolution MUST 
be done identically on all requests. Thus, it must be specified in the 
protocol, not in the requirements document. The requirements document might 
list the kinds of conversions we might expect, but should not mandate where 
the converstions happen.

> > >      If a canonicalisation algorithm is proposed, the algorithm must be
> > >      easily upgradable as new languages/writing systems are added.
> > > I disagree. We can't have a moving target for canonicalization. It must
> > > be fixed *before* any internationalization of the DNS occurs.
> >
> > But canonicalisation is a on going process, unless you can define a
> > caonicalisation which is flexible enough to handle every languages already
> > known to the computer world and in future.
>
>Again, the question is where canonicalization occurs.

Quite right.

--Paul Hoffman, Director
--Internet Mail Consortium