W3C home > Mailing lists > Public > www-math@w3.org > April 2002

Re: MathML-Presentation specs criticized.

From: David Carlisle <davidc@nag.co.uk>
Date: Mon, 15 Apr 2002 23:49:08 +0100
Message-Id: <200204152249.XAA25033@penguin.nag.co.uk>
To: jimbofc@yahoo.com
CC: www-math@w3.org


> (5) For instance, the mathvariant, mathsize, mathcolor and
> mathbackground attributes can be set by equivalents in CSS.  I think the
> spec mentions this, but I can't find it.

This is not true unless CSS were extended to support mathematics (which
is a possibility) The whole point of the style/content separation
in CSS is that the style is essentially cosmetic and can be changed
according to the preferences of the reader. The reason for having
separate mathvariant attribute to control the math font is that this
does not work for mathematics. A textual heading may be switched from
bold to sans serif to italic, at the discretion of the house style for
the document, but you can't do that if it contains mathematics. It is
important that the expression encodes these math alphabets in a way that
is immune to external font changes from stylesheets. (An external
stylesheet can still change fonts but only using this information from
the markup in the document, ie choice of fraktur font, roman font etc,
but it can't be allowed to make arbitrary characters bold, as can a
normal stylesheet for text.


c) However, as context changes from document to
   document and culture to culture, MMLP can become irreverent despite
   extension mechanisms built into MathML.

No, the primary purpose of presentation markup is to specify the layout
this layout specification does not become irrelevant just because the
meaning of that layout varies in different contexts.

> It is ambiguous whether or not the number 2 is a index or an exponent.
> A more descriptive way of describing the situation is:

MathML already has the content elements to make this distinction, 
I don't see how having invisible operators in the presentation markup
makes this distinction any clearer (and in general I don't see how it
would work at all, you insert an invisible ^ to distinguish one out of
the many uses of superscript, but how would you distinguish thehundreds
of different notations that use a fraction-like layout. There is no
clear place in the mfrac scheme where you could put invisible operators.
MathML as currently defined lets you separate the semantics and the
layout, using mfrac for the layout (or msup or whatever other notation
is desirable) but specifying the semantics using <apply> from the
content markup which is, in the main just an expression of the 
tree structure of the mathematical expression <apply><power/>....


David


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Received on Monday, 15 April 2002 18:49:55 GMT

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