Overconstraint alignment

Dear Editors,

With respect to line areas there can be conflicting or overconstraint
alignment specifications. I couldn't find a reference to that situation in
the specification. Example: 

<fo:block font-size="32pt">Big
  <fo:inline font-size=".25em"
      dominant-baseline="reset-size"
      alignment-baseline="before-edge">top
    <fo:inline font-size="2em">alpha
    </fo:inline>
  </fo:inline>
</fo:block>

Here we want "top" at the before-edge of the line area but the nested inline
"alpha" wants to be aligned at the alphabetic baseline of "top". Because
"alpha" uses a bigger font than "top" these two conditions cannot be
satisfied simultaneously. It is unclear to me how this is to be resolved. 

Thank you very much

Manuel Mall