  <li>the class is explicitly "registered" in the archive
  </ul>
</ul>

<p>
The default behavior is almost always the most convenient one.  However,
there a few cases where it would be desirable to override the
default.  One case is that of a virtual base class. In a diamond
heritance structure with a virtual base class, object tracking
will prevent redundant save/load invocations.  So here is one
case where it might be convenient to override the default tracking
trait. <i>(Note: in a future version the de