This presentation: http://www.ibiblio.org/xml/slides/xmldevcon2000sanjose/advancedxml/
W3C Schema Primer: http://www.w3.org/TR/xmlschema-0/
XML Schema Part 1: Structures: http://www.w3.org/TR/xmlschema-1/
XML Schema Part 2: Datatypes: http://www.w3.org/TR/xmlschema-2/