1  <element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0">
 2    <zeroOrMore>
 3      <element name="card">
 4        <element name="name">
 5          <text/>
 6        </element>
 7        <element name="email">
 8          <text/>
 9        </element>
10        <optional>
11  	<element name="note">
12  	  <externalRef href="inline.rng"/>
13  	</element>
14        </optional>
15      </element>
16    </zeroOrMore>
17  </element>