W3C xml.xsd schema

Hi,

I'm a newbie at XML Schema and I don't understand all the stuff about namespaces.

In the schema joined to this mail (a simplified version of http://www.w3.org/2001/xml.xsd),
are the attributes contained by specialAttrs referencing the one that are defined
in the same schema ?

If it is the case, why isn't there an xmlns:xml="http://www.w3.org/XML/1998/namespace" 
attribute for the schema ?

<?xml version='1.0'?>
<xs:schema targetNamespace="http://www.w3.org/XML/1998/namespace" xmlns:xs="http://www.w3.org/2001/XMLSchema" xml:lang="en">

 <xs:attribute name="lang" type="xs:language"/>

 <xs:attribute name="space" default="preserve">
  <xs:simpleType>
   <xs:restriction base="xs:NCName">
    <xs:enumeration value="default"/>
    <xs:enumeration value="preserve"/>
   </xs:restriction>
  </xs:simpleType>
 </xs:attribute>

 <xs:attribute name="base" type="xs:anyURI"/>

 <xs:attributeGroup name="specialAttrs">
  <xs:attribute ref="xml:base"/>
  <xs:attribute ref="xml:lang"/>
  <xs:attribute ref="xml:space"/>
 </xs:attributeGroup>

</xs:schema>

Thanks.

--
Michaël Marchegay, Stagiaire France Telecom R&D du 11/02/2002 au 26/07/2002
Sous la responsabilité d'Olivier Dubuisson
DTL/TAL - 22307 Lannion Cedex - France