What version of xmllint do you have ?
This works for me, from the top source dir with libxml version 20913 (xmllint --version):
xmllint --xpath "/config/tags/para[@role='tag_Z_support']" doc/xsl-config.xml
It returns:
<para role="tag_Z_support">
<inlinemediaobject conformance="3d">
<imageobject>
<imagedata fileref="images/check.png"/>
</imageobject>
</inlinemediaobject>
This function supports 3d and will not drop the z-index.
</para>
Maybe we can implement what we need (extracting a tag by an XPath expression) via xsltproc, given we are already using that for other things ?
