for what it's worth, this (as an xml file) does not seem to work:

<query xmlns="http://labkey.org/data/xml/query">
    <metadata>
        <tables xmlns="http://labkey.org/data/xml">
            <table tableName="Datasets" tableDbType="NOT_IN_DB">
                <titleColumn>Label</titleColumn>
            </table>
        </tables>
    </metadata>
</query>