Type information (polymorphism) is required so that objects of the proper type are created when the object stream is read back.

The Serialization package uses the standard C++ runtime type identification (RTTI) mechanism to provide type information. Because the names given to the various types differ depending on the compiler, the type name is captured as it appears in the source and then transformed into a canonical type name common to all compilers. This canonical name is used in the object stream interfaces.