defines possible
values for a data node, usually as part of an attribute's datatypesupplies the name of a predefined datatype in the datatype library specified by the
source attributepoints to the datatype library in which the name specified by the name attribute is defined
http://www.w3.org/2001/XMLSchema-datatypes
The default source is the list of datatypes provided by XML Schema schema for XML Schemas: Part 2: Datatypes
supplies a string representing a regular expression providing additional constraints
on the strings used to represent values conforming to this datatype