xd- with C/DNAME (was: Re: The Two Lookups Approach (was Re: Parsing the issuesand finding a middle ground -- another attempt))

[John C Klensin]

Erik,

I'm not going to comment further on this until I see one or more
specific proposals.  I hope those proposals will respond to the
issues Andrew has raised as well as the ones I have.  However...

--On Monday, March 16, 2009 09:54 -0700 Erik van der Poel
<erikv at google.com> wrote:

> Also, if it is true that the current expectation is that
> CNAME/DNAME are typically hidden from the user, I think that
> might be an argument for a new prefix, which basically says
> "this is an exceptional circumstance, please process according
> to special rule set R".

This is one of the specific areas in which I'm having a problem
forming a mental picture of what you are actually suggesting.
Certainly it would be no problem for a registry to analyze an
incoming non-ASCII string and say, "this is odd, give it a
different prefix when it is stuffed into the zone".  

But to look up such a label, the application needs to start with
an arbitrary string of Unicode characters and decide how to
encode it and what prefix it gets.  Is your expectation that
each application, as part of IDNAx processing, will maintain a
table of odd characters, potentially with different mapping
rules and prefixes for each group?  I suppose that would be
possible, but it is the sort of thing that experience indicates
that people routinely get wrong, leading to the sort of
interoperability problems that cannot be predicted or easily
diagnosed.

     john