How can I test if the variable $xsd_node was assigned a value?
In some cases the node-set expression to fill this variable might copy
nothing.

...
<xsl:variable name="xsd_node">
  <xsl:copy-of select="$xsd_doc//xs:element[@name = $name and
count(child::node()) = 0]"/>
</xsl:variable>

<xsl:if test="???">
...

Is there something like empty($xsd_node)?

Cheers,

R.