<attribute name="context" use="optional">
    <annotation>
        <documentation>An indication of whether this line is a current line, or a repeat of a special-interest line from the past.</documentation>
    </annotation>
    <simpleType>
        <restriction base="string">
            <enumeration value="opening" />
            <enumeration value="closing" />
            <enumeration value="current" />
        </restriction>
    </simpleType>
</attribute>