The schema corresponding to this document is normative, with respect to the syntactic constraints it expresses in the XML Schema language. The documentation (within <documentation> elements) below, is not normative, but rather highlights important aspects of the W3C Recommendation of which this is a part Now the derived primitive types pattern specifies the content of section 2.12 of XML 1.0e2 and RFC 1766 pattern matches production 7 from the XML spec pattern matches production 5 from the XML spec pattern matches production 4 from the Namespaces in XML spec A utility type, not for public use #all or (possibly empty) subset of {restriction, union, list} A utility type, not for public use Can be restricted to required or forbidden Required at the top level Forbidden when nested We should use a substitution group for facets, but that's ruled out because it would allow users to add their own, which we're not ready for yet. base attribute and simpleType child are mutually exclusive, but one or other is required itemType attribute and simpleType child are mutually exclusive, but one or other is required memberTypes attribute must be non-empty or there must be at least one simpleType child