 and
an item named <code>scale</code>, which is a string describing the measurement scale.
If the string ends in <code>" unit"</code>, e.g.  <code>x[["temperature unit"]]</code> (note the
space), then just the expression is returned, and if it ends in <code>" scale"</code>,
then just the scale is returned.</p></li>
<li><p>If <code>i</code> is a string ending in <code>"Flag"</code>, then the corresponding data-quality
flag is returned (or <code>NULL</code> if there is no such flag).</p></li>
<li><p>If the ob