To conclude the discussion of XML basics, the following are links to useful documents to help you work with XML and understand it better:
http://www.w3c.org/xml: The official Web site of XML
http://www.w3c.org/TR/REC-xml: The W3C XML 1.0 recommendation
http://www.w3c.org/DOM/: The W3C Document Object Model
http://www.w3.org/TR/REC-xml: The formal rules for DTDs in XML 1.0
http://www.w3.org/TR/xmlschema-0/: XML Schema Part 0: Primer
http://www.w3.org/TR/xmlschema-1/: XML Schema Part 1: Structures
http://www.w3.org/TR/xmlschema-2/: XML Schema Part 2: Datatypes
http://www.xml.com: A site dedicated to providing XML resources, discussions, and so on
http://msdn.microsoft.com/xml/tutorial/default.asp: Microsoft’s XML tutorial