Will be restricted to required or forbidden This is for the top-level datatype element, as ref'ed in <schema Required at the top level This is for the nested datatype element, as used in <element Forbidden when nested schema/datatype @name each (8-bit) byte is encoded as a sequence of 2 hexidecimal digits value is encoded in Base64 as defined in the MIME RFC pattern matches production 8 from the XML spec pattern matches production 7 from the XML spec pattern matches production 5 from the XML spec values of this datatype must be unique within a document pattern matches production 6 from the XML spec (modified as required by the Conformance section in Namespaces in XML (http://www.w3.org/TR/REC-xml-names#conformance)) values of this datatype must have occured within a document as the value of some component of type ID pattern matches production 4 from the Namespaces in XML spec values of this datatype must have occured within a document as the value of some component of type ID pattern matches production 6 from the XML spec (modified as required by the Conformance section in Namespaces in XML (http://www.w3.org/TR/REC-xml-names#conformance)) values of this datatype must match the name of an unparsed entity declared in the schema pattern matches production 4 from the Namespaces in XML spec values of this datatype must match the name of an unparsed entity declared in the schema pattern matches production 4 from the Namespaces in XML spec pattern matches production 6 from the Namespaces in XML spec