may have been disabled in order to speed execution
or for some other reason.  Some applications, E.G. runtime linking
of plug-in modules, can't depend on C++ RTTI to determine the
true derived class.  RTTI only returns the correct type for polymorphic
classes - classes with at least one virtual function.  If any of these
situations applies, one may substitute his own implementation of
<code style="white-space: normal">extended_type_info</code>
<p>
The interface to facilities required to implement serializat