[xsl] spirit an xml element away and bring it back

[Frank Marent <frank.marent@xxxxxxxxxxx>]

hello.

we are trying (for a rountripping of xml documents between arbortext  
editor and adobe framemaker) to spirit mathml code away from xml  
arbortext editor documents (to open in adobe framemaker) and let the  
mathml code reappear again when returning to xml arbortext editor.

the best would be to hide the mathml code in an attribute and let it  
also reappear again from that, but we could only make *one* way  
(hiding the code) and only in a *processing instruction* by this xslt  
fragment:

  ...
  <xsl:template match="FormulaEntity">
    <FormulaEntity>
      <xsl:text disable-output-escaping="yes">&lt;?MATH </xsl:text>
      <xsl:apply-templates/>
      <xsl:text disable-output-escaping="yes"> ?&gt;</xsl:text>
    </FormulaEntity>
  </xsl:template>
  ...

i wonder if there is any way to to spirit an xml element with all  
descendants away, hiding it in an attribute and bring it back to  
stage after that. our xml input code would be like:

<FormulaEntity>
  <m:math>
    <m:mrow>
      <m:mroot>
        <m:mrow>
          <m:mn>5</m:mn>
        </m:mrow>
        <m:mrow>
          <m:mn>2</m:mn>
        </m:mrow>
      </m:mroot>
    </m:mrow>
  </m:math>
</FormulaEntity>

we have to store the <m:math> element and the best would be to have  
after that something like:

<FormulaEntity  
MathML="&lt;m:math&gt;&lt;m:mrow&gt;&lt;m:mroot&gt;&lt;m:mrow&gt;&lt;m:m 
n&gt;5&lt;/m:mn&gt;&lt;/m:mrow&gt;&lt;m:mrow&gt;&lt;m:mn&gt;2&lt;/ 
m:mn&gt;&lt;/m:mrow&gt;&lt;/m:mroot&gt;&lt;/m:mrow&gt;&lt;/m:math&gt;">

and bringing the code back to the input code.

is there any solution in xslt for that? for tips many thanks in advance.

frank