<element name="addressBook" xmlns="http://relaxng.org/ns/structure/1.0">
<zeroOrMore>
<element name="card">
<attribute name="name">
<text/>
</attribute>
<attribute name="email">
<text/>
</attribute>
<optional>
<attribute name="note">
<text/>
</attribute>
</optional>
</element>
</zeroOrMore>
</element>