[XeTeX] Could JK provide a little backgound on how OpenType MATH tables are handled?

[Vasile Gaburici]

Will Robertson has this sentence in the documentation for
unicode-math: "Turns out that XƎTEX is clever enough to deal with big
operators for us automatically with \XeTeXmathchardef. Amazing!".

1) I've been looking at the MATH OpenType tables with fontforge, which
supports editing them [http://fontforge.sourceforge.net/math.html],
and the automation seems to be based on the lists provided by the font
inside "Hor. Variants", etc. Could JK confirm that this is indeed the
case, i.e. those lists are understood and used by XeTeX.

2) There's also a bunch of stuff in the MATH sub-tables that I don't
see how it could be used in the world of TeX. For instance, the
complex way in which math accents are defined (axis, etc.) I presume
that this stuff is just ignored, i.e. there's no MATH table rendering
as such in XeTeX (since freetype doesn't support it AFAIK), but
information is converted into what the olde TeX math code can handle.
Correct?