I found the answer..
Below is the answer.
<xs:element name="Book">
<xs:annotation>
<xs
ocumentation>Root Element</xs
ocumentation>
</xs:annotation>
<xs:complexType>
<xs:choice>
<xs:element name="AuthorName"/>
<xs:element name="AuthorID"/>
</xs:choice>
</xs:complexType>
</xs:element>
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