MVALID (was Re: M-Label or MVALID, and dangers with mappings?)
Pete Resnick
presnick at qualcomm.com
Sun Apr 12 21:34:24 CEST 2009
On 4/11/09 at 8:26 AM +0200, Patrik Fältström wrote:
>I have seen the discussions regarding M-Label, and my say that as an
>editor of the tables document, I think it might be "more
>interesting" to define MVALID as a property that is calculated in
>the tables document.
>
>Suggestion:
>
>MVALID would be a codepoint that is mapped, according to the
>standardized mapping function, to something that is not DISALLOWED.
I really hated M-label. The suggestion of MVALID (which I also don't
like so much) finally crystallized in my head why I thought this was
such a bad idea: MVALID is only definable in terms of characters that
are "mapable" to "not DISALLOWED". But *anything* is mapable: A
mapping function could choose to map U+2022 (bullet) to U+002D
(hyphen-minus), and for some input methods in some contexts, that
might make perfect sense; in others, it might be best rejected as
"illegal input". But, as I tried to say before (and was summarily
ignored), a mapping function of this sort is an input method/user
interface issue, not a protocol issue. In all cases, a mapping is a
best guess at what U-label string the user intended. We are already
in the land of "let's make a mapping function that preserves
IDNA2003, except for a particular set of characters". Mappings are
going to change, and for some contexts (whether different locales or
using them for web browsers vs. an application for registration)
mappings might reasonably be different.
If we're going to deal with mappings, I want it to be a separate
document. I am fine with that document saying, "Use this mapping for
maximal compatibility with IDNA2003". I am reluctantly OK with that
mapping document laying out a full mapping instead of being
rule-based or having a reference to an external algorithm. But I
strongly object to any such mapping (or the definition of M-label or
MVALID) appearing in the current documents.
pr
--
Pete Resnick <http://www.qualcomm.com/~presnick/>
Qualcomm Incorporated - Direct phone: (858)651-4478, Fax: (858)651-1102
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