test/XInclude/docs/fallback.xml

<x xmlns:xinclude="http://www.w3.org/2001/XInclude">
   <!-- Simple test of a fallback on unavailable URI -->
   <xinclude:include href="something.xml">
     <xinclude:fallback><warning>Inclusion failed</warning></xinclude:fallback>
   </xinclude:include>
</x>