<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>