<t:root xmlns:t="test"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="test test.xsd">

  <t:base><a>a1</a></t:base>
  <t:derived><a>a2</a></t:derived>
  <t:base xsi:type="t:base"><a>a3</a></t:base>
  <t:derived xsi:type="t:base"><a>a4</a></t:derived>

</t:root>
