On 4/21/14, 5:12 AM, "Martin J. Dürst" wrote:
[Sorry for the top-posting, but it's way easier for those who want to
see just the next bit of the argument.]
On 2014/04/19 11:13, Peter Saint-Andre wrote:
>>>>
I'm still worried about foot-guns. Part of what we've tried to do in
PREICS is to actively prevent people who don't necessarily know much
about internationalization from shooting themselves in the foot. Yes, we
could tell those folks "it's fine to allow whatever mix of RTL and LTR
characters you like, as long as you don't care how they're presented" -
but we know that could cause serious confusion if more than one actor in
said protocol might view the same string. Do we really think that's a
good idea?
>>>>
Even strings without a mix of RTL and LTR characters can lead to
confusing display, e.g. if they contain digits at the start or at the
end. Don't remember to what extent they are excluded in IDNs.
As long as Precis strings are displayed only in isolation, the
restrictions may not be that important, but the moment any of these
strings is displayed with something else, maybe with an entervening
punctuation, these restrictions will be very helpful, although not
perfect (they aren't perfect for IDNs, either).
So I think the restrictions are a good thing.
I still agree.
Looking back at the text, I think Pete might have a point. I suggest the
following change.
###
OLD
The directionality rule of a profile specifies which strings are to
be considered left-to-right (LTR) and right-to-left (RTL), and the
allowable sequences of characters in LTR and RTL strings (see Unicode
Standard Annex #9 [UAX9]); note that mixed-direction strings are not
supported, since there is currently no widely accepted and
implemented solution for the processing and display of mixed-
direction strings. Possible rules include, but are not limited to,
(a) considering any string that contains a right-to-left code point
to be a right-to-left string, or (b) applying the "Bidi Rule" from
[RFC5893].
NEW
The directionality rule of a profile specifies which strings are to
be considered left-to-right (LTR) and right-to-left (RTL), and the
allowable sequences of characters in LTR and RTL strings (see Unicode
Standard Annex #9 [UAX9]). Possible rules include, but are not
limited to, (a) considering any string that contains a right-to-left
code point to be a right-to-left string, or (b) applying the "Bidi
Rule" from [RFC5893].
Mixed-direction strings are not directly supported by the PRECIS
framework itself, since there is currently no widely accepted and
implemented solution for the processing and safe display of mixed-
direction strings. An application protocol that uses the PRECIS
framework (or an extension to the framework) could define methods for
handling mixed-direction strings; however, such methods are outside
the scope of the framework.
###
Peter
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