> Most of it I can generate, but how can I fill the parentid? 
> If there is no
> ancestor-element named <somenode> then the parent_id should 
> be 0, else the
> parent_id should be the group_id of the ancestor.

<xsl:attribute name="parent_id">
  <xsl:choose>
   <xsl:when test="ancestor::somenode">
     <xsl:value-of select="ancestor::somenode[1]/@group_id"/>
   </xsl:when>
   <xsl:otherwise>0</...

Mike Kay
Software AG

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