Schema Design Patterns: Avoiding Complexity

http://www.xml.com/pub/a/2002/11/20/schemas.html

Using W3C XML Schema

http://www.xml.com/pub/a/2000/11/29/schemas/part1.html
(printed version: http://www.xml.com/lpt/a/691)

And from Oracle:

• XML Schema: Understanding Namespaces
  
• XML Schema: Understanding Datatypes
  
• XML Schema: Understanding Structures
  

And from WebReference:

• The XML Schema Companion. Chapter 15: Patterns
  
• 15.9 Character Class Escapes