W3C XML Schema (WXS), a grammar-based XML schema language, is used to define and limit XML vocabularies. It is the foundation of some other standards in areas from XML messaging to data binding. Learn about its relationship to other schema language technologies.
XML Schema Part 1: Structures Second Edition and XML Schema Part 2: Datatypes Second Edition [W3C Recommendations] define another schema language for XML. The first part allows you to constrain the structure of the document, and the second part allows you to constrain the contents of simple elements and attributes. WXS has faced criticism for complexity and a lack of expressiveness; the result is competition from other languages such as RELAX NG. Increasingly, people are just using whatever schema language suits them best and turning to an impressive crop of emerging tools to convert from one form to another according to need. Many other specifications have used the WXS Datatypes specification, although there have been calls to develop alternative data type systems. The working group has started work on WXS 1.1 -- XML Schema 1.1 Part 1: Structures and XML Schema 1.1 Part 2: Datatypes [in development]. These look to fix some of the much-reported problems with the 1.0 versions while retaining maximum backward compatibility.
Work is also winding down on Basic XML Schema Patterns for Databinding Version 1.0 [in development], which provides Schema usage advice for users of data binding systems. Data binding is a method of converting XML instances into application objects of a certain structure, and vice versa.
- Nicholas Chase's tutorial, Validating XML, covers both Document Type Definition (DTD) and WXS (developerWorks, August 2003).
- The W3C XML Schema working group offers a thorough and prosaic introduction to the technology in XML Schema Part 0: Primer Second Edition.
- The official W3C XML Schema includes lists of tools and other specifications that use WXS.
- ZVON offers a WXS reference.
- W3Schools has a WXS Elements Reference.
- Read about other XML standards: Index of XML standards.
- Participate in any of several XML-centered forums: XML zone discussion forums.
- Get involved in the developerWorks community: developerWorks blogs
- Find out how you can become an IBM-Certified Developer in XML and related technologies at IBM XML certification.
- See the developerWorks XML Zone for a wide range of technical articles and tips, tutorials, standards, and IBM Redbooks at XML technical library.
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