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