[DFDL-WG] checkConstraints example?

Can you please supply an example of using checkConstraints to valid an enumeration? There's not one in the spec, and none of the tutorials I have demo this. Suppose I have this DFDL: <xsd:element name="DayOfTheWeek"...> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="Mon" /> <xsd:enumeration value="Tue" /> <xsd:enumeration value="Wed" /> ... </xsd:restriction> </xsd:simpleType> </xsd:element> TIA