2001-02-22: Thomas Wason initial creation
In namespace-aware XML processors, the "xml"
prefix is bound to the namespace name http://www.w3.org/XML/1998/namespace.
Do not reference this file in XML instances
Schawn Thropp: Changed the uriReference type to string type
2001-07-26: S Thropp: Changed the XSD namespace to point to
Schema of schemas for the 5/2/2001 W3C Recommendation
Changed the XSD types for base and link to xsd:anyURI
Refers to universal XML 1.0 lang attribute
Refers to XML Base: http://www.w3.org/TR/xmlbase