ng objects through a pointer in order to be sure
that multiple identical objects are not created when an archive is loaded.
This "tracking behavior" is controlled by the type trait defined in the header
file <a href="../../../boost/serialization/tracking.hpp" target="tracking_hpp">tracking.hpp</a>
which defines the following:
<pre><code>
// names for each tracking level
enum tracking_type
{
    // never track this type
    track_never = 0,
    // track objects of this type if the object is serialized throug