The implemented persistent storage system just performs the fundamental operations of storage allocation, and do not do any more. It provides the C++ language with a simple mechanism for persistent storage and pointers.
The SimpleTree class (See Section 4.1) demonstrates the missing functions of the persistent storage. There must be a set of Generalized Collection Classes for all the persistent objects. Sets, bags, trees, tables, lists, stacks, queues, dictionaries, etc. - the list will go on and on.
These collection classes must also support the run-time type information for the persistent objects to contain a mixture of elements with different types in a single collection. Class derivation will be integral to the implementation. Compatibility with virtual functions will be sought in spite of the portability obstacles (See Section 3.3.10).
The interfaces to the classes must be simple, general, and flexible. Combination of collections must also be supported.