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