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