unrecognised entities & mathvariant

Hello,

I am trying to produce XHTML+MathML version of math research articles
in latex. For this I use a very nice tool which I recommend : tralics
http://www-sop.inria.fr/apics/tralics/.

Anyway, the difficulty here is to find code working as well in mozilla
and IE+MathPlayer, and hopefully in their near-future competitors. I'd
like to get advice on these two precise issues, for a start:

1. I can say <mi>&Sfr;</mi> or <mi mathvariant="fraktur">S</mi> or
<mi>&#x1D516;</mi> :
I'd tend to think that the latter is the less prone to interpretation
on the part of the browser, but as the second plane support in unicode
is low, I have high risks to get a box or a ? in place of the expected
char. the first one is OK but could be more obscure to a browser
without full MathML support. Hence I'd be inclined to opt for the mid
one, thinking that, at least an S would be shown in any context.

But currently, though the 3 versions are equivalent in MP 2.1, only
the first one displays the right glyph in mozilla 2.0. Are there plans
to support other math-variants that the 4 basic weights in mozilla?

2. the MathML DTD defines quite many entities and aliases. I would
expect that a MathML aware tool would treat any alias as equivalent.
this is not the case with current mozilla. For instance, hbar and
emptyset are unknown to mozilla, while hslash and empty are: is this a
bug or a feature and, in any case, where is the info why some of them
are supported and who they are? (my feeling is that the official ISO
name is implemented, and aliases, even part of the mathml DTD, are
left apart: right ? --but is this mathml support?)

Well, enough questions for a start!

Th. B.