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World Wide Web Consortium Issues XML Schema

A few weeks after agreeing on XHTML interoperability standards, the World Wide Web Consortium (W3C) Wednesday issued XML Schema as a W3C recommendation to help developers improve the functionality of e-commerce systems.

XML schemas define shared markup vocabularies, the structure of XML documents which use said vocabularies, and provide hooks to associate semantics with them. And as W3C spokesperson Janet Daly has said in the past, a W3C recommendation is as good as done as it has fulfilled stability requirements by the group.

Two years in the making, the schemas were created by bringing data types to XML to increase its performance for developers of e-commerce systems, database authors, or anyone who is in the business of managing copious amounts of data on the Web. Using tighter integration, the Schemas make it easier to define the elements and attributes in a namespace, and to validate documents.

The XML Schema specification consists of three parts: the first part defines a set of basic datatypes, which can be associated with XML element types and attributes to help software do a better job of managing dates, numbers, and other forms of information; the second part poses methods for describing the structure and constraining the contents of XML documents, and defines the rules governing validation of documents; the third is a primer, which explains what schemas are, how they differ from DTDs, and how someone builds a schema.

One of the interesting features of an XML Schema is that a Web developer can build a schema that borrows from a previous schema, but overrides it where new unique features are needed. This is similar to the behavior of Cascading Style Sheets and allows the user to develop XML Schemas that best suit their needs, without building an new vocabulary.

"XML Schema makes good on the promises of extensibility and power at the heart of XML," said Tim Berners-Lee, W3C director and father of HTML. "In conjunction with XML Namespaces, XML Schema is the language for building XML applications."

Supporters of XML Schema include Sun Microsystems Inc., Commerce One Inc. and IBM Corp.

Oracle Corp., too, stood up for XML Schema. In a public statement Wednesday, the software giant said its Oracle9i Database will be the first production database to implement the final recommendation for the standard. The firm said it gave Java, XML and SQL developers early access to each new version of the specifications.

XML Schema tools include Validator and Test Suite Collection W3C. W3C invites developers to send in sample schemas for a test, to be reviewed and managed by the W3C XML Schema Working Group.