Brighten Your Career Path This Diwali - Invest in Yourself! 
An XML Schema is a language for expressing constraints about XML documents. There are several different schema languages in widespread use, but the main ones are Document Type Definitions (DTDs), Relax-NG, Schematron and W3C XSD (XML Schema Definitions). From this page you can find out more about DTDs and W3C XSD, since those are the primary schema languages defined at W3C.
XML Schema
