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<div class="moz-cite-prefix">On 8/23/2022 10:12 AM, Sławomir Osipiuk
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1661273955452.2394519965.3855422546@gmail.com">
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<span class="viv-signature"></span>On Tuesday, 23 August 2022,
08:51:26 (-04:00), Asmus Freytag via Unicode wrote:<br>
<br>
<blockquote style="margin: 0 0 0.80ex; border-left: #0000FF 2px
solid; padding-left: 1ex">
<div class="moz-cite-prefix"><span style="font-family: Candara;">For
compatibility with older parsers, all @missing directives
are wrapped in comments.</span></div>
</blockquote>
<div><br>
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If @missing directives are meaningful but ignored by older
parsers, doesn't that result in incorrect values? Is that
preferable to the parser simply failing on a new syntax?</blockquote>
<p>In principle, yes, and we've backed out of some suggested
solutions at one point because there was the danger that a parser
might not read a field.</p>
<p>However, this train has left the station with Unicode 15.0; we're
committed to moving to the new scheme for non-binary properties
and will finish implementing it. That VO hasn't been moved over
was a resource issue, not a policy one.</p>
<p>@missing directives simply provide machine readable information
where originally we had human-readable comments. Old parsers were
supposed to implement the default values via the human readable
description of the properties.<br>
</p>
<blockquote type="cite"
cite="mid:1661273955452.2394519965.3855422546@gmail.com">
<div><br>
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<div>Would it only give incorrect values to unassigned code
points?<br>
</div>
</blockquote>
<p>90% of properties have a single "all other code points" value,
which is the same for code points not listed as well as not
assigned. And in most cases, there's a value like "No" or "Other"
that's the obvious value to choose. Those are relatively
straightforward to build into a parser (or an API returning
property data). But it's better to be explicit as we now are with
the @missing directives.<br>
</p>
<blockquote type="cite"
cite="mid:1661273955452.2394519965.3855422546@gmail.com">
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<div><br>
<blockquote style="margin: 0 0 0.80ex; border-left: #0000FF
2px solid; padding-left: 1ex">
<p><font face="Candara">For some properties, such as derived
bidi class, the full scheme will be present in 15.0,
but vertical orientation missed the cutoff, so that will
be taken care of in the next version(s).</font></p>
<p><font face="Candara">Where multiple @missing lines are
used, you will no longer see explicit listing of default
values for reserved code points.</font></p>
</blockquote>
<div><br>
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Then, from a parsing perspective, Vertical_Orientation is not
currently complex (it has one default and all other values are
explicit) but it will be complex (multiple defaults) in the
next version.</div>
</div>
</blockquote>
<p>No, it does have complex "defaults" in the second sense of
default (value for unassigned code point) but not for the first
sense of default ("omitted value in the listing").</p>
<p>Past time we got this all moved to a single scheme.</p>
<p>A./<br>
</p>
<p><br>
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