<xs:attribute name="frame">
    <xs:simpleType>
        <xs:restriction base="xs:token">
            <xs:enumeration value="all" />
            <xs:enumeration value="bottom" />
            <xs:enumeration value="none" />
            <xs:enumeration value="sides" />
            <xs:enumeration value="top" />
            <xs:enumeration value="topbot" />
            <xs:enumeration value="void" />
            <xs:enumeration value="above" />
            <xs:enumeration value="below" />
            <xs:enumeration value="hsides" />
            <xs:enumeration value="lhs" />
            <xs:enumeration value="rhs" />
            <xs:enumeration value="vsides" />
            <xs:enumeration value="box" />
            <xs:enumeration value="border" />
        </xs:restriction>
    </xs:simpleType>
</xs:attribute>