<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault
="qualified" attributeFormDefault="unqualified">
  <xs:redefine schemaLocation="a.xsd">
     <xs:attributeGroup name="ab">
       <xs:attributeGroup ref="ab"/>
       <xs:attribute name="c"/>
       <xs:attribute name="d"/>
     </xs:attributeGroup>
  </xs:redefine>
  <xs:element name="rut">
     <xs:annotation>
       <xs:documentation>Comment describing your root
element</xs:documentation>
     </xs:annotation>
     <xs:complexType>
       <xs:attributeGroup ref="ab"/>
     </xs:complexType>
  </xs:element>
</xs:schema>