XSD "simpleType" validation for strings

Hi.

Most of the tutorials for schema validation libraries are in terms of 
validating an entire document.  I'm interested in just validating text 
strings against an xsd simple type.

Are there any good open source libraries out there that would give me 
hooks to do this in either C or Java?

Thanks!
  -jimbo

Excelsior! XML Marshaller for Cocoa
http://www.homepage.mac.com/jimbokun/Excelsior.html