Schema Language For XML
Program-Transformation.Org: The Program Transformation Wiki
DocumentTypeDefinition was introduced in the XML standard as the schema language for XML. Because of the limited power of DTD and because it cannot handle XMLNamespaces in an acceptable way a lot of alternative schema languages have been developed.
The schema languages that are currently used have been compared using a formal framework in TaxonomyOfXMLSchemaLanguagesUsingFormalLanguageTheory.
-- MartinBravenboer - 30 May 2002