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Subject: Re: Agenda for the 2021-03-24 SG16 telecon
From: Tom Honermann (tom_at_[hidden])
Date: 2021-03-18 17:12:47

On 3/17/21 4:18 PM, Corentin Jabot via SG16 wrote:
> On Wed, Mar 17, 2021, 21:09 Tom Honermann via SG16
> <sg16_at_[hidden] <mailto:sg16_at_[hidden]>> wrote:
> On 3/17/21 10:45 AM, Steve Downey via SG16 wrote:
>> On Wed, Mar 17, 2021 at 9:22 AM Tom Honermann via SG16
>> <sg16_at_[hidden] <mailto:sg16_at_[hidden]>> wrote:
>> On 3/17/21 5:23 AM, Corentin Jabot wrote:
>>> On Tue, Mar 16, 2021 at 3:59 PM Tom Honermann via SG16
>>> <sg16_at_[hidden] <mailto:sg16_at_[hidden]>> wrote:
>>> * P1628 <https://wg21.link/p1628>: Unicode character
>>> properties
>>> As the author I do not expect to do further work on this in
>>> the 23 cycle
>> That matches my expectations, thanks for confirming.
>> Not that we have a paper, or that I'm asking for anyone to do
>> work, but without access to the UCD, all the other algorithms are
>> off the table. In theory it's an implementation detail, in
>> practice it would be an ABI break to change the APIs for property
>> lookup, and having two or more mechanisms in a std library
>> implementation seems like a bad idea.
>> Expectation setting is important. It's not clear to everyone how
>> the Unicode layers work, even if the explanations are
>> straight-forward.
> We don't have proposals for any algorithms yet.  I would feel some
> concern about trying to standardize access to the UCD without
> algorithms to go with it; at least reference implementations
> showing what is possible.
> Perhaps something that might be helpful is an audit of the
> algorithms and which UCD properties they each depend on.  That
> might help to prioritize which UCD properties to expose first,
> which ones we can guarantee stability for, etc...
> Properties and algorithms are related in that some algorithms depend
> on some properties, but that doesn't inform the design of the
> properties paper.
> At all.
I only mentioned algorithms as a means for determining priority. The
paper details choices made in terms of which properties are exposed and
how they are named.  It will likely require a fair amount of discussion
to get consensus on those choices.  We may be able to make progress more
quickly by prioritizing subsets of properties.
> For example, the XID_ properties are useful to write a compiler
> independently of Unicode algorithms.
> Ignoring diatrics from search is something browsers and other
> applications implement by looking at properties without it being a
> Unicode defined mechanism.
> Etc.
> I can definitely offer more use cases in the paper.
> Some algorithms (notably regexes) may need the data presented in
> slightly different form.
> We should have Unicode properties if we believe Unicode algorithms do
> not cover the set of use cases for Unicode, not because we want to
> implement Unicode algorithms

I think both perspectives make sense.  In general it is useful to
provide the underlying capabilities to implement something outside the
standard even if it is offered by the standard.


> Tom.
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