Example XML

      <exam paper="cs203">
      <student>
      Fred Smith
      </student>
      <qapair>
      <question>Who is the last King of England</question>
      <answer>George VI</answer>
      </qapair>
      <qapair>
      <question>How many queens were named Elizabeth </question>
      <answer>Two</answer>
      </qapair>
      </exam>
    

The possible tags are defined by a DTD (Document Type Definition)