<element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0" xmlns:a="http://www.example.com/annotation">
  <zeroOrMore>
    <element name="card">
      <a:documentation>Information about a single email address.</a:documentation>
      <element name="name">
        <text/>
      </element>
      <element name="email">
        <text/>
      </element>
    </element>
  </zeroOrMore>
</element>