The up-down-stop type is used for octave-change elements, indicating the direction of the shift from their true pitched values because of printing difficulty.
<xs:simpleType name="up-down-stop"><xs:annotation><xs:documentation>The up-down-stop type is used for octave-change elements, indicating the direction of the shift from their true pitched values because of printing difficulty.</xs:documentation></xs:annotation><xs:restriction base="xs:token"><xs:enumeration value="up"/><xs:enumeration value="down"/><xs:enumeration value="stop"/></xs:restriction></xs:simpleType>