<case_expression xmlns="http://www.sqlparser.com/xml/ansi2003"> <case_abbreviation>{1,1}</case_abbreviation> <case_specification>{1,1}</case_specification> </case_expression>
<xs:element name="case_expression"> <xs:complexType> <xs:choice> <xs:element ref="case_abbreviation"/> <xs:element ref="case_specification"/> </xs:choice> </xs:complexType> </xs:element>