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>