<book xmlns:x="http://x" xmlns:y="http://y">
  <x:title>Test Book</x:title>
  <chapter>
    <y:title>Ch1</y:title>
    <para>p1.1</para>
    <para>p1.2</para>
    <para>p1.3</para>
  </chapter>
  <x:chapter>
    <y:title>Ch2</y:title>
    <x:para>p2.1</x:para>
    <y:para>p2.2</y:para>
  </x:chapter>
</book>