<x xmlns:xi="http://www.w3.org/2001/XInclude"> <a><xi:include xpointer="xpointer(//b)"/></a> <b><xi:include xpointer="xpointer(//a)"/></b> </x>
<x xmlns:xi="http://www.w3.org/2001/XInclude"> <a><xi:include xpointer="xpointer(//b)"/></a> <b><xi:include xpointer="xpointer(//a)"/></b> </x>