<xs:attribute name="lang">
  <xs:annotation>
    <xs:documentation>
      <div>
        <h3>lang (as an attribute name)</h3>
        <p>denotes an attribute whose value is a language code for the natural language of the content of any element; its value is inherited. This name is reserved by virtue of its definition in the XML specification.</p>
      </div>
      <div>
        <h4>Notes</h4>
        <p>Attempting to install the relevant ISO 2- and 3-letter codes as the enumerated possible values is probably never going to be a realistic possibility.</p>
        <p>See BCP 47 at
          <a href="http://www.rfc-editor.org/rfc/bcp/bcp47.txt">http://www.rfc-editor.org/rfc/bcp/bcp47.txt</a>and the IANA language subtag registry at
          <a href="http://www.iana.org/assignments/language-subtag-registry">http://www.iana.org/assignments/language-subtag-registry</a>for further information.</p>
        <p>The union allows for the 'un-declaration' of xml:lang with the empty string.</p>
      </div>
    </xs:documentation>
  </xs:annotation>
  <xs:simpleType>
    <xs:union memberTypes="xs:language">
      <xs:simpleType>
        <xs:restriction base="xs:string">
          <xs:enumeration value=""/>
        </xs:restriction>
      </xs:simpleType>
    </xs:union>
  </xs:simpleType>
</xs:attribute>