1<element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0">
2  <zeroOrMore>
3    <element name="card">
4      <choice>
5	<element name="name">
6	  <text/>
7	</element>
8	<attribute name="name">
9	  <text/>
10	</attribute>
11      </choice>
12      <choice>
13	<element name="email">
14	  <text/>
15	</element>
16	<attribute name="email">
17	  <text/>
18	</attribute>
19      </choice>
20    </element>
21  </zeroOrMore>
22</element>
23