Definition of Values of Property Vertical_Orientation

[Richard Wordingham]

On Tue, 23 Aug 2022 05:51:26 -0700
Asmus Freytag via Unicode <unicode at corp.unicode.org> wrote:

> For unassigned code points, a "default" means the most likely future 
> value. In a few cases, that's not a single value across the entire
> code space, but there may be regions set aside for encoding
> characters that require different values than the default and where
> it makes sense to "future proof" some algorithms by picking a
> different value as the most likely one.

> Whether the actual value will later correspond to the default value
> is left open and there will be some exceptions, but generally these
> values are chosen to minimize disruptions.

Reality is a cheap version of this.  And I'm not sure that choosing the
most likely value minimises the disruption to be expected when new
characters arrive before the new UCD; other values may do better.

> 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.

Richard.