1<grammar xmlns="http://relaxng.org/ns/structure/1.0">
2  <start>
3    <ref name="top"/>
4  </start>
5  <define name="empty">
6    <empty/>
7  </define>
8  <define name="top">
9    <element name="top">
10	<ref name="empty"/>
11	<element name="a">
12	  <text/>
13	</element>
14    </element>
15  </define>
16</grammar>
17