XML Schemas express shared vocabularies and allow machines to carry out rules made by people. They provide a means for defining the structure, content and semantics of XML documents. in more detail. XML Schema was approved as a W3C Recommendation on 2 May 2001 and a second edition incorporating many errata was published on 28 October 2004; see reference list for pointers.

The XML Schema Working Group, part of the XML Activity, is responsible for the W3C's work on this topic -- for details see the Working Group's charter. W3C Members can also participate in the W3C XML Schema Interest Group, a forum for the discussion of technical issues relating to the development of XML Schema. It also has a charter.

The Bugzilla system should also be used to report errors with XML Schema 1.0.