The World Wide Web Consortium (W3C) issued XML Schema as a W3C Recommendation. XML Schemas define shared markup vocabularies, the structure of XML documents that use those vocabularies, and provide hooks to associate semantics with them. By bringing datatypes to XML, XML Schema increases XML’s power and utility to the developers of electronic commerce systems, database authors and anyone interested in using and manipulating large volumes of data on the Web. By providing better integration with XML Namespaces, it makes it easier than it has ever been to define the elements and attributes in a namespace, and to validate documents that use multiple namespaces defined by different schemas. The XML Schema specification consists of three parts. One part defines a set of simple datatypes, which can be associated with XML element types and attributes; this allows XML software to do a better job of managing dates, numbers, and other special forms of information. The second part of the specification proposes methods for describing the structure and constraining the contents of XML documents, and defines the rules governing schema-validation of documents. The third part is a primer, which explains what schemas are, how they differ from DTDs, and how someone builds a schema. XML Schema are XML documents themselves, they may be managed by XML authoring tools, or through XSLT. XML Schema Tools Include Validator and Test Suite Collection W3C, with the University of Edinburgh has co-developed XSV, the XML Schema Validator. The validator has been revised at each stage of XML Schema development and now provides validation against the XML Schema Recommendation. In addition, W3C invites developers to send in sample schemas for a test suite library, to be reviewed and managed by the W3C XML Schema Working Group.