<simpleType name="NilReasonEnumeration">
    <union>
        <simpleType>
            <restriction base="string">
                <enumeration value="inapplicable" />
                <enumeration value="missing" />
                <enumeration value="template" />
                <enumeration value="unknown" />
                <enumeration value="withheld" />
            </restriction>
        </simpleType>
        <simpleType>
            <restriction base="string">
                <pattern value="other:\w{2,}" />
            </restriction>
        </simpleType>
    </union>
</simpleType>