Definition of Values of Property Vertical_Orientation

[Markus Scherer]

On Tue, Aug 23, 2022 at 11:32 AM Richard Wordingham via Unicode <
unicode at corp.unicode.org> wrote:

> > Where multiple @missing lines are used, you will no longer see
> > explicit listing of default values for reserved code points.
>
> Which will *silently* damage some parsers' output.  The damage should
> show as Unicode 16.0 comes out.
>

Unicode *15*, in a few weeks.

Depending on the parser, you might see it getting confused about
multiple @missing lines, or getting incorrect property values for
unassigned code points.

We have had one prominent data file with multiple @missing lines since
before the start of Unicode 15 beta, and we emphasized this on the beta
review page <https://www.unicode.org/versions/beta-15.0.0.html>.

Starting with Version 15.0, some data files in the UCD may contain multiple
@missing lines defined for the same property. This is currently the case
for DerivedBidiClass.txt. UCD file parsers will need to be updated to treat
the additional @missing lines like data lines. See UAX #44 Section 4.2.10,
@missing Conventions
<https://www.unicode.org/reports/tr44/tr44-29.html#Missing_Conventions> for
details.


Some weeks later we added multiple @missing lines to a couple more data
files.

We are trying to innovate on Unicode data files in the gentlest way
possible...

Best regards,
markus
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