<its:rules xmlns:its="http://www.w3.org/2005/11/its" xmlns:h="http://www.w3.org/1999/xhtml"  version="2.0">
 <its:param name="externalresourceParam">1</its:param>
 <its:externalResourceRefRule selector="//h:p[@id=$externalresourceParam]/h:video" externalResourceRefPointer="@poster"/>
</its:rules>