With the exception of the basic XML syntax, XML Schema is without a doubt the single most important technology in the XML family. In the Web services world, XML Schema is the key technology for enabling interoperation.
XML Schema is a W3C recommendation that provides a type system for XML-based computing systems. XML Schema is an XML-based language that provides a platform-independent system for describing types and interrelations between those types. Another aspect of XML Schema is to provide structuring for XML documents.
Document Type Definitions (or DTDs) were the precursor to XML Schema, and are a text- (not XML-) based format designed to convey ...