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