<element name=“addressBook” xmlns=“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>