<xs:complexType name="group" abstract="true" >
  <xs:annotation>
    <xs:documentation>
   group type for explicit groups, named top-level groups and
   group references</xs:documentation>
  </xs:annotation>
  <xs:complexContent mixed="false">
    <xs:extension base="xs:annotated">
      <xs:group minOccurs="0" maxOccurs="unbounded" ref="xs:particle"/>
      <xs:attributeGroup ref="xs:defRef"/>
      <xs:attributeGroup ref="xs:occurs"/>
    </xs:extension>
  </xs:complexContent>
</xs:complexType>