1<element name="card" xmlns="http://relaxng.org/ns/structure/1.0">
2 <attribute name="name"/>
3 <attribute name="email"/>
4 <attribute name="preferredFormat">
5 <choice>
6 <value type="string">html</value>
7 <value type="string">text</value>
8 </choice>
9 </attribute>
10</element>
11