> we have a problem within mathml
impossible!

> This is my concrete problem: we have  
> to change by xslt all m:mo elements that consist of one special  
> character (entity reference) to symbol font for output. the input is  
> coming from design science mathflow on arbortext editor:
> 
>    <m:mo>&divide;</m:mo>

Hey they're my entities you know:-)

So here you definitely do not want to test for an entity reference as
you want &divide; &#247; &#xf7; and the w character all to work the
same way.

The parser makes them all into a single character before XSLT starts and
you can match on that character

<xsl:template match="m:mo[.='&#247;']">... stuff....</xsl:template>

So you just need a load of these (it's often useful to generate all the
needed templates by using a different xsl stylesheet)

If you are using xslt2 then an alternative approach is to use character
maps:
  <xsl:character-map name="toc">
    <xsl:output-character character="&#177;" string="+/-"/>
    <xsl:output-character character="&#8211;" string="-"/>
    <xsl:output-character character="&#8467;" string="l"/>
    <xsl:output-character character="&#967;" string="chi"/>
....

David