<grammar xmlns="http://relaxng.org/ns/structure/1.0">

  <start>

    <element name="addressBook">

      <zeroOrMore>

	<element name="card">

	  <ref name="card.attlist"/>

	</element>

      </zeroOrMore>

    </element>

  </start>

  <define name="card.attlist">

    <group>

      <attribute name="name">

	<text/>

      </attribute>

      <attribute name="email">

	<text/>

      </attribute>

    </group>

  </define>

</grammar>