Q2: What mapping function should be used in a revised IDNA2008 specification?

[John C Klensin]

--On Tuesday, March 31, 2009 12:07 -0400 Vint Cerf
<vint at google.com> wrote:

> What characters should be mapped into what other characters in
> a   revised IDNA2008 specification?
> 
> Can we describe succinctly and precisely what these mappings
> are? How?   What should they be?

I actually don't believe we can do that, as the recent
discussions that suggest that "mapping" actually implies
restoration of all IDNA2003 relationships and characters,
elimination of the requirement to reject (rather than looking
up) strings containing DISALLOWED or UNASSIGNED characters, etc.
Under no circumstances should mapping be used as a mechanism for
undoing those decisions, i.e., mapping should be permitted only
when the result is a PVALID character.