W3C home > Mailing lists > Public > www-math@w3.org > April 2006

Re: rendering entities

From: David Carlisle <davidc@nag.co.uk>
Date: Mon, 24 Apr 2006 11:19:15 +0100
Message-Id: <200604241019.k3OAJFET032583@edinburgh.nag.co.uk>
To: Stephan.Semirat@ac-grenoble.fr
CC: www-math@w3.org


Stephan,

> Thank you. Is that what you mean : &DifferentialD; and d are just
> characters with no "content" meaning ? 

You need to be a bit careful about the terminology. The entity reference
&DifferentialD;
has no significance at all in MathML. In many systems it is completely
resolved by the XML parser before the MathML processor even sees the
input.

So the question is really not about entities but rather on whether the
choice of character with Unicode number 8518 or number 100 has any
"content" significance. As Stan has already indicated this depends a lot
on what process is reading the MathML. 

The primary purpose of Presentation MathML is to express the
presentation (that is, the layout forms used, although in a sufficiently
general way that the same  description can be used in different visual
settings and aural renderings etc.) Of course it is possible for a system
to read the presentation form and infer semantics, just as it is
possible to read a printed page and infer semantics, but typically to do
so you need to know some more context such as the subject area and
notations used. So it may be that some processors find it easier to
recognise an integral using character 8518 as the "d"  but some may not.

If you want to unambiguously mark up that your expression is an integral
over a certain bound variable, then that is precisely the purpose of
Content MathML.

This is a general feature about mathematical notations, and nothing
special about differential-d.  Obviously some aspects such as searching
might be simplified if everyone used the same notation for everything,
but a) in practice that isn't going to happen and b) there would be some
loss of cultural heritage and linguistic differences if it did.
Again, Content MathML is there precisely to allow the mathematical
meaning to be marked up while still allowing differences in notation.
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. If
everyone used "tan" for tangent then I, as a native English speaker, might
find it a bit easier to search to find occurrences of the tangent
function but MathML does not enforce this notation on the world.
Have a look at the examples in
http://www.w3.org/TR/arabic-math/
where tangent is expressed (in Presentation MathML) in four different
ways, depending on the cultural notational style being used.
tan, tg, and two different Arabic words. Just as Presentation MathML
does not force you to use "tan" for tangent, it does not force you to
use a double struck d in integrals, and the method of choosing your
preferred notation is the same in either case, you put whichever
characters that you want to use inside an mi element.


> However, if for instance i want to translate my xhtml+mathml files to
> tex, then &DifferentialD will be translated to \dd while d will be translated to d. 
> So i need to encode these two letter differently, no ?

Not necessarily. If your \dd macro is a non-italic d then you could
either use a mathvariant on the mi to specify roman, or just simply make
your convertor detect the idiom of an mrow that starts with an integral
sign and ends with d _something_  and convert it to whatever TeX markup
you need.


David

________________________________________________________________________
This e-mail has been scanned for all viruses by Star. The
service is powered by MessageLabs. For more information on a proactive
anti-virus service working around the clock, around the globe, visit:
http://www.star.net.uk
________________________________________________________________________
Received on Monday, 24 April 2006 10:23:37 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Saturday, 20 February 2010 06:12:58 GMT