Linking (chapter 6.4.3) probably underspecified

Dear MathML designers,

  I have just filed a bug with Mozilla's Gecko rendering engine, which may
have a deeper impact on the Presentation MathML spec.  I would like to link
Presentation MathML symbols to their definitions in OpenMath Content
Dictionaries.  With <mo> that works fine, using @xlink:href (Gecko does not
yet support @href.)  But with <mfrac> I have a problem:  The @xlink:href
applies to the whole subtree and therefore also overrides links from operators
inside the fraction that point somewhere else.  Please see
https://bugzilla.mozilla.org/show_bug.cgi?id=559042 and the attached test
case at https://bugzilla.mozilla.org/attachment.cgi?id=438750&action=edit.

What _I_ would prefer in this situation is that the link in mfrac/@xlink:href
only affects the fraction stroke.  On the other hand, with other "parent"
elements (e.g. <mrow>) it is common that links on them override all links
given on children, which makes sense in a way.  On the other hand, why
shouldn't the outer link in

<mrow xlink:href="outer">ooooo<mrow xlink:href="inner">iii</mrow>ooo</mrow>

only affect the "oooo" text and allow the "iii" text to link somewhere else?

Or is there an <mo>-like alternative for <mfrac>, of which I have not yet been
aware?

I had hoped that the spec would clarify the intended linking behavior, but it
does not.  (http://www.w3.org/TR/MathML3/chapter6.html#interf.link)

Any ideas?

Cheers, and thanks in advance,

Christoph

-- 
Christoph Lange, Jacobs Univ. Bremen, http://kwarc.info/clange, Skype duke4701