Re: [idn] Determining equivalence in Unicode DNS names

[Patrik Fältström <paf@cisco.com>]

--On 2002-01-14 11.57 -0800 Stuart Cheshire <cheshire@apple.com> wrote:

> It seems to me that one of the great problems of IDN is one that is=20
> fundamentally unsolvable: an attempt to determine, once and for all
time, =

> a single global set of rules for deciding if two strings are "equal"
or=20
> "equivalent".

In the DNS system, there is a general rule (as you point out) that the
same
matching rule is to be used for a label regardless of from where the
query
is sent, to what server, and in what domain the label exists.

Reason for this is to prevent confusion, and to secure the in DNS needed
global uniqueness.

Example: If a.com and b.com is considered equal, why should not a.se and
b.se be equal? If a.com and b.com is equal, why is not a.a.com and
b.a.com?

Basically, you ask for context specific matching rules, and that is
something which is impossible to handle in the DNS protocol, because the
client and server can not exchange context. Yes, you point out the only
context that is available, the name of the parent domain. But, how is
the
client able to know what rules exists in a specific domain? Further, is
not
the matching rule more depending on what language the registrant of the
domain and the one querying is using than what parent domain the domain
is
registered in? I would as a swedish-speaking person claim that 'a'
followed
by combining diaeresis be a different character than adiaeresis, while
someone using some other language might think they should be equal. The
same way, I would like having the 'o' with slash and the odiaeresis be
considered the same, while others disagree. All of this because of _my_
culture.

So, this wg decided that we will use one and only one matching rule,
just
like we decided to use only one character set. Both of these (the rule
and
the charset) are created in the Unicode Consortium.

You also talk about "evolving matching rules over time". That is a very
bad
thing.

Let's say that we have registered apple.com and =E4pple.com. They are
considered different. One day the equivalence rule change, and they are
considered being the same. Who is calling Steve Jobs saying that
apple.com
have to give back it's domain name and pick something else? You? ICANN?
The
registry for .com?

    paf