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>
18