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Re: rendering entities

From: Bruce Miller <bruce.miller@nist.gov>
Date: Mon, 24 Apr 2006 09:10:54 -0400
Message-ID: <444CCE5E.7040607@nist.gov>
To: www-math@w3.org

David Carlisle wrote:
> Juan wrote:
>>In my opinion to use <mo>d</mo> instead of the entity because last is not
>>rendering adequately 
> 
> 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 dounle
> struck d.

I think it's slightly messier than that, in that there
seems to have developed a slight mismatch between what
MathML intended and the resulting Unicode tables.

MathML specifies &DifferentialD; (along with &ExponentialE;
&ImaginaryI; &CapitalDifferentalD;)  "for use in differentials"...
without addressing the appearance.  David is certainly right
that there is no requirement that they be used --- nor should
there be --- however, it comes across as strongly preferred
for the reasons that several people have noted.

At the other end, the Unicode codepoints for these entities
ended up with descriptions like:
   DOUBLE-STRUCK ITALIC SMALL D
   * sometimes used for the differential
In other words, the "d" is primarily double-struck, and only
secondarily "differential".

In other words, it seems to have been another historical development
that we're kinda stuck with.  As David says below: "That's life"

> If you do not want a double struck d then you should not use
> that character. See also the arabic examples for summation in
> http://www.w3.org/TR/arabic-math/
> In some examples a character more in keeping with the Arabic script than
> the "Sigma-like" summation sign is used. Using multiple characters for
> summation obviously complicates some things, but the solution is not to
> tell everyone to use the same character. Solutions involve a mixture of
> authors using Content Markup in addition to Presentation markup, in
> order to make the meaning clear and software just learning to cope by
> recognising a wider set of notational conventions. Neither is entirely
> trivial to achieve, but that's life.

This is all certainly correct, but I'd agree with Juan in the sense 
of changing "If you do not want a double struck d" to "If you strongly
object to ...";   There are potential benefits, and these glyphs look
only _slightly_ odd (so far my Editors haven't objected :> ).

That said, there're often enough other "Special" characters
in a formula that parallel content markup would be needed anyway;
In that case, the loss (due to not using entities) is small.

-- 
bruce.miller@nist.gov
http://math.nist.gov/~BMiller/
Received on Monday, 24 April 2006 13:11:09 GMT

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