Should mathbackground have (and default to) a transparent value?

The mathbackground attribute is defined in
http://www.w3.org/TR/2003/REC-MathML2-20031021/chapter3.html#presm.commatt
to default to 'inherited'.  Yet it is allegedly similar to the CSS
background-color property, which is not inherited.  If it is
inherited, how does it work (particularly when mixing with
non-MathML)?  If not, should it have a transparent value like the
background attribute on mstyle:
http://www.w3.org/TR/2003/REC-MathML2-20031021/chapter3.html#id.3.3.4.2
and default to that value?

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/