With XML Schema you can describe (in XML) how a certain XML
documents have to look like. It is similar to doctype definitions,
but it is much mightier. With XML Schema you can not only describe
the structure of a document, you can also define XML datatypes.
Links
http://www.w3.org/TR/xmlschema-0/
Title:
Primer
Description:
Part 0 of the XML Schema specification: Primer (non-normative)
http://www.w3.org/TR/xmlschema-1/
Title:
Structures
Description:
Part 1 of the XML Schema specification: Structures
http://www.w3.org/TR/xmlschema-2/
Title:
Datatypes
Description:
Part 2 of the XML Schema specification: Datatypes
http://www.w3.org/XML/Schema
Title:
XML Schema at W3C
Description:
Homepage of XML Schema at the W3C.