<xs:attributeGroup name="cellvalign">
    <xs:annotation>
        <xs:documentation>
      vertical alignment attributes for cell contents
      </xs:documentation>
    </xs:annotation>
    <xs:attribute name="valign">
        <xs:simpleType>
            <xs:restriction base="xs:token">
                <xs:enumeration value="top" />
                <xs:enumeration value="middle" />
                <xs:enumeration value="bottom" />
                <xs:enumeration value="baseline" />
            </xs:restriction>
        </xs:simpleType>
    </xs:attribute>
</xs:attributeGroup>