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

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

>To: Dan Oscarsson <Dan.Oscarsson@kiconsulting.se>
>Cc: dewell@adelphia.net, klensin@jck.com, idn@ops.ietf.org
>Subject: Re: Is space allowed in a hostname?
>X-Hashcash: 020709:Dan.Oscarsson@trab.se:6a0136bb72edce86
>X-Hashcash: 020709:dewell@adelphia.net:43f94292c523c78c
>X-Hashcash: 020709:klensin@jck.com:4f511128bbb871d5
>X-Hashcash: 020709:idn@ops.ietf.org:ed630ef750c2ac24
>From: Simon Josefsson <simon+idn@josefsson.org>

>Since NFKC is used in stringprep too, this is not only for domain
>names but internationalized strings in many environments (such as
>authentication identities and passwords).  The use of NFKC is optional
>in stringprep though, but the alternative is to use no normalization
>at all.
>
>Stringprep furthermore warns profile authors against using the
>no-normalization alternative because it may confuse users.  In all
>honesty, I think stringprep should also say that using NFKC may also
>confuse users, altough perhaps different users and different kind of
>confusion.
>

I do not know why stringprep only have NFKC or unnormalised as possible
choices. NFC is a very suitable choice to use for UCS.
It is the choice of W3C and is the required choice in IRI/URIs.
NFC have the nice properties that it preserves all information and is
compact. It is a very good choice to use for interoperability.
Unnormalised is only useful locally on a system, never for
interoperability.
NFKC is a possible choice when matching text but may go to far when
related to identifiers (names).

   Dan