If the document's schema is an XML Schema [XML Schema Part 1] , this constant represents the derivation by restriction if complex types are involved, or a restriction if simple types are involved.
The reference type definition is derived by restriction from the other type definition if the other type definition is the same as the reference type definition, or if the other type definition can be reached recursively following the {base type definition} property from the reference type definition, and all the derivation methods involved are restriction.