MVALID (was Re: M-Label or MVALID, and dangers with mappings?)

Vint Cerf vint at
Mon Apr 13 22:34:12 CEST 2009

john, andrew, et al,
we are not in any disagreement that the WG must take responsibility for
defining the lookup mapping function. Context and framework for this
function needs to be specified as do the rules/principles that govern its

If there are additional mappings that are pursuant to user interface issues,
these would need to be applied independent of the common mapping under
discussion which seems to me to be intended to reduce the scope of the
IDNA2003 mapping regime while also seeking to reduce (I don't say minimize
here) the degree of adjustment needed to accommodate conflicting IDNA2003
registration and lookup behavior in comparison with a strict application of
an unmapped IDNA2008 lookup.

I hope I didn't say that too badly.


On 4/13/09, John C Klensin <klensin at> wrote:
> --On Monday, April 13, 2009 15:42 -0400 Vint Cerf
> <vint at> wrote:
> > if this is to be a separate document, this document still
> > needs to be considered a part of the specifications because
> > that is what we agreed to do in the last face/face working
> > group meeting: ie. to map on lookup while not mapping on
> > registration.
> I would still argue for a separate document on the grounds that
> we should define the canonical forms and protocol is a way
> calculated to be as stable as possible with as much opportunity
> for conformity as possible.  The mapping activity appears to me
> to be likely to be appreciably less stable.  We've had multiple
> examples on the list of situations in which implementations may
> wish to apply alternate mappings and, if we subdivide
> compatibility mappings as my earlier note suggested, it seems to
> me that, unless  the mappings are compatibility-only, they will
> need much more review with new versions of Unicode than the
> basic rules.
> > In other words this mapping function is not distinct from the
> > IDNA2008 spec at least that is how I read our conclusion at
> > the meeting.
> I didn't make quite that inference, but I don't think it makes
> very much difference and will happily accept your judgment.  It
> is clear to me that, if we are going to have standardized
> mapping, the WG must take some responsibility for its context
> and framework.
>     john
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