<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="ex-a" >
  <xs:complexType mixed="true" >
    <xs:sequence> 
     <xs:element name="heading" type="xs:string" /> 
    </xs:sequence> 
  </xs:complexType>
</xs:element>
</xs:schema>