Re: [idn] Re: Is space allowed in a hostname?

[Dan Oscarsson <Dan.Oscarsson@trab.se>]

>From: John C Klensin <klensin@jck.com>


>That said, I claim that I do understand the issues and that
>several other people in the WG also understand them and have
>understood them more or less all along.  And, based on that
>understanding, I don't believe that revisiting NFKC is going to
>get us anywhere.  That isn't because NFKC is right or wrong, but
>because its selection involves tradeoffs, that _no_ alternative
>is without similar tradeoffs, and that there are no rational
>criteria for selecting one set of tradeoffs over another.  

It may be to late to do something about NFKC. NFKC is difficult and
at least I have never gotten any answer from those I have asked what
NFKC changed compared to NFC. I have therefore tried to read the
Unicode tables to see what it means, and I do think it goes to
far for domain names.

As IDNA combines this with lower caseing using the Unicode "full
lower casing" which results in for example German s sharp into ss,
we get an even worse situation.

While it could be OK for IDNA to use this definition of
domain names and matching of them, I is bad if makes it
impossible to use a standard based on NFC and rules
allowing for example German s sharp to not match ss, in
a new class or other technique to get UCS into DNS.

I have seen drafts refering to IDNA/NAMEPREP to define
what characters are allowed in a domain name. That is bad as
it makes it difficult for us to change things later on.

    Dan