Mapping (was: Issues lists and the "preprocessing" topic)

Andrew Sullivan ajs at commandprompt.com
Tue Aug 19 15:47:12 CEST 2008


I've changed the subject line because I am responding to just one
issue in John's mail.

On Mon, Aug 18, 2008 at 08:48:04PM -0400, John C Klensin wrote:

> The implications of the above are that we not only aren't
> encouraging extensive local-option mapping, we are encouraging
> no mapping at all except for backward compatibility when
> necessary and as a user interface convenience.   For the latter,
> the expectation is that one will make the mappings as early as
> possible and use only the mapped (U-label or A-label) form in
> files; storing anything else in a file or sending it across the
> network is strongly discouraged.   Also, even when mappings are
> done, the rule that is now present in the documents still
> stands, i.e., one must not map a PVALID or CONTEXT character
> into anything else -- mapping is permitted only for DISALLOWED
> characters.

For me, the nagging worry is that you can pack just about anything you
like into "user interface convenience".  Why not just say that
local-option mapping SHOULD NOT be used except when required for
compatibility with IDNA2003?  I get that this could make some
interfaces clunkier.  But it seems to me that local mapping on the
grounds of convenience surely just means "map when you like", so we
should expect that every DISALLOWED character ends up mapped somehow,
in different ways depending on local policy.  Such a situation seems
to me to have a great potential for surprising results.

A

-- 
Andrew Sullivan
ajs at commandprompt.com
+1 503 667 4564 x104
http://www.commandprompt.com/


More information about the Idna-update mailing list