<element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0">

  <zeroOrMore>

    <element name="card">

      <choice>

	<element name="name">

	  <text/>

	</element>

	<attribute name="name">

	  <text/>

	</attribute>

      </choice>

      <choice>

	<element name="email">

	  <text/>

	</element>

	<attribute name="email">

	  <text/>

	</attribute>

      </choice>

    </element>

  </zeroOrMore>

</element>