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| <grammar xmlns="http://relaxng.org/ns/structure/1.0">
| <start>
| <ref name="top"/>
| </start>
| <define name="empty">
| <empty/>
| </define>
| <define name="top">
| <element name="top">
| <choice>
| <ref name="empty"/>
| <element name="a">
| <text/>
| </element>
| </choice>
| </element>
| </define>
| </grammar>
|
|
