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Re: rendering entities

From: <juanrgonzaleza@canonicalscience.com>
Date: Tue, 25 Apr 2006 02:21:05 -0700 (PDT)
Message-ID: <3100.217.124.88.235.1145956865.squirrel@webmail.canonicalscience.com>
To: <www-math@w3.org>

Quote about &InvisibleTimes;

</blockquote>They are especially important new additions to the UCS
because they provide textual clues which can increase the quality of print
rendering, permit correct audio rendering, and allow the unique recovery
of mathematical semantics from text which is visually
ambiguous.</blockquote>

I do not agree with "The choice of notation to use for the "d" is at
exactly the same level as the choice of notation to use for (say) the
tangent function." We can see special entity for former but there is not
special entity for "tan" or "tg". Why?

Encoding <mo>d</mo> or <mi>d</mi>, computer does not know if it is a
differential, is the operator d, or the variable d. Aural rendering is
also different and if searching for &dd; then a search engine would not
return pages containing two first encodings.

However, writing <mo>tg</mo> or <mo>tan</mo> computer cannot confound with
sequences "t" "g" or with "t" "a" "n". And I do not know nobody using tg
or tan for denoting a single variable (whereas d as variable is very
popular, e.g. ax^4 + bx^3 + cx^2  + dx).

The aural rendering of something as old presentational HTML

<span alt="differential of x">d<i>x</i></span>

is better than next MathML

<mrow><mo>d</mo><mi>x</mi></mrow>

and one of reasons for the existence of &Differential;. From the MathML
specification:

<blockquote>
However, the elements are medium-independent in the sense that they have
been designed to contain enough information for good spoken renderings as
well.

[...]

Certain MathML characters are used to name operators or identifiers that
in traditional notation render the same as other symbols, such as
&DifferentialD;, &ExponentialE;, or
&ImaginaryI;, or operators that usually render invisibly, such as
&InvisibleTimes;,
&ApplyFunction;, or &InvisibleComma;.  These are distinct notational
symbols or objects, as evidenced by their distinct spoken renderings and
in some cases by their effects on linebreaking and spacing in visual
rendering, and as such should be represented by the appropriate specific
entity references.</blockquote>

"as such should be represented". Of course, it is not obligatory use them
and some folks are focusing on this. Well also the own MathML
specification is just a recommendation and nobody is obligated to use
it...

David added,

> That isn't what is happening, the entity dd is a reference to a specific
> Unicode character and that character has default rendering as a double
struck d. If you
> do not want a double struck d then you should not use that character.

Then from the point of view of Presentation MathML, either one uses
<mo>d</mo> (acceptable visual rendering, incorrect aural rendering) or
uses <mo>&Differential;</mo> (non-standard visual rendering, correct aural
rendering). Is that?

Like comparison I would say that in XML-Maiden Math the solution is easy
and would be similar (I am not an expert on) to

<group role= "differential">d</group>

Of course with possibility for using any other letter or symbol, or roman,
italic, or bold, font if desired via CSS.

In the old CanonMath, I carefully introduced an empty tag for
differentials (<diff/>) after was visually rendered as a roman d by
default (but authors could change rendering to anything that they want, of
course) but aurally recognized as a proper differential.

It is clear one can disambiguate d via MathML <semantics>, but many tools
just are focusing on presentational markup. E.g. I do not know any browser
supporting content markup.

Also it is interesting see the point from the perspective of final users.
Take Distler’s blog as illustration, how can my computer know that the
some of the d in <mi>d</mi> in Distler’s blog webpages x are differentials
whereas others are the variable d?

Finalize doing some remarks on the Unicode standard 3.2.

First, d in <mo>d<mo> or <mi>d</mi> is a letter. The &Differential; is not
a letter, it is a letterlike symbol of specific usage for mathematics.
Unicode standard adds

<blockquote>
These stylized mathematical symbols are used in some documents to
distinguish special mathematical usages from ordinary variables.
</blockquote>

Unicode also remarks that 2146 (differential) is *not* equal to the d
latin small letter d.


Juan R.

Center for CANONICAL |SCIENCE)
Received on Tuesday, 25 April 2006 09:21:20 GMT

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