Rendering primes/learning MathML

Hi, I'm new to this group and to MathML. It looks like this is a
pretty low-traffic group
and I'm not sure if anybody is still reading it.

The first post I read was the one about rendering primes, but it's too
old for me to
reply to, hence the new post. I'm basically trying to learn MathML by
reading the
MathML 2.0 spec. It isn't designed as a tutorial, but it seems to be
the most complete
reference available. Pointers to other materials welcome.

Anyway, for primes I ended up using this construction:

<mrow>
   <mi>a</mi><mo accent="true">'</mo>
</mrow>

It seemed from my reading that this was what I was supposed to do, to
tell
the renderer that the prime was an operator and to set the "accent"
flag.
So unlike the original poster, I didn't use the superscript
construction.
The result appeared in Firefox to be OK. I haven't yet had a chance to
see
how my page looks in any other browser (IE is the only one that can
support
MathML, correct?).

Comments on this construction? It bothers me that the prime
is treated this way, as a separate entity. That seems somehow to me to
violate the spirit of MathML. I was looking for a construction that
told it that
"a-prime" was a single entity, a variable in its own right. So my
first attempt
was

   <mi>a'</mi>

which didn't work, but I can't recall what I got in that case. Using
the <mrow>
was my alternate attempt to convey this. As I notice the examples make
liberal use of nested <mrow>s, that seems to be the generally-
recommended
style.

                     Randy