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

  <!-- all combinations -->
  <all>
    <a>a</a>
    <b>b</b>
    <c>c</c>
  </all>

  <all>
    <a>a</a>
    <c>c</c>
    <b>b</b>
  </all>

  <all>
    <b>b</b>
    <a>a</a>
    <c>c</c>
  </all>

  <all>
    <b>b</b>
    <c>c</c>
    <a>a</a>
  </all>

  <all>
    <c>c</c>
    <a>a</a>
    <b>b</b>
  </all>

  <all>
    <c>c</c>
    <b>b</b>
    <a>a</a>
  </all>

  <!-- optional c is not present -->
  <all>
    <a>a</a>
    <b>b</b>
  </all>

  <all>
    <a>a</a>
    <b>b</b>
  </all>

</t:root>
