Re: [EXTERNAL] Re: Minutes: MathML Core meeting July 27, 2020

Hello,

I am trying to follow the discussion, and would love to ask for help
with clarifying the terminology/use cases here.
Paging through the TeXbook, it appears to me vertical bars are given
three independent treatments - 1) simple symbol |, 2) middle fence,
e.g. \middle|, \bigm| and 3) relation: \mid. I'm attaching a tiny PDF
file that shows the (indeed visible!) differences between the four,
when there is a proper 2D object to delimit.

So, I think I am reading Murray's examples as if separator=true in the
Dirac notation maps onto \middle|, i.e. "a middle fence", and
fence=true for bra and ket maps onto \right| and \left|.

As someone who had to learn the meanings of "fence", "separator" and
"delimiter" as a second language, I will confess to having undergone
some significant confusion in building a mental image where the three
words aren't outright synonyms. In colloquial English it appears that
fences were used very early on to separate fields, and hence delimit
them. On the other hand, I will also confess I have never had any
confusion with understanding "left", "middle" and "right" as distinct
concepts.

I think it's quite reasonable that the various uses of vertbar should
be expressible in (normative) presentation MathML, as Murray suggests,
so there should either be 1) an alternative representation with
spacing/sizing directives, or 2) the a11y attributes would need to
become normative (which is unlikely from what I understand), or 3) the
status quo must be maintained.

Greetings,
Deyan

On Mon, Jul 27, 2020 at 7:41 PM Murray Sargent
<murrays@exchange.microsoft.com> wrote:
>
> The fence and separator attributes are useful in Dirac notation. For example, in the expectation value , the vertical bars are separators (not absolute-value fences), while in the bra , the vertical bar is a closing fence. So separator=“true” conveys the former and fence=”true” conveys the latter. Both LaTeX and OfficeMath have these distinctions, so it’s important that they don’t get lost in Presentation MathML.
>
> At some point, I’d like to offer the richness of OfficeMath on the web and MathML is the obvious storage format for that. So I really don’t want to deprecate MathML to the point where we can’t speak and display it correctly. An even more ambitious goal is to be able to compute with Presentation MathML, a goal that wants more attributes rather than less. Browsers need to be able to speak math correctly and so even if the display of a vertical bar is the same for absolute value and the expectation value above, it isn’t spoken the same way. So we need the distinction and should fix the description in the MathML spec.
>
> Thanks,
>
> Murray
>
>
>
> From: David Carlisle
> Sent: Monday, July 27, 2020 3:58 PM
> To: public-mathml4@w3.org
> Subject: [EXTERNAL] Re: Minutes: MathML Core meeting July 27, 2020
>
>
>
>
>
> on fence= and separator=  the mathml3 spec says
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> This attribute generally has no direct effect on the visual rendering, but may be useful in specific cases, such as non-visual renderers.
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> I think the proposed semantic attributions would be giving much better non-visual clues here and suggest we just drop both of these from full
>
> (we could potentially keep them in the schema as legacy ignored attributes)
>
>
>
> David
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>
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