The persistent pointer object represents a unique location in the address space of the persistent storage. It also represents the identity of an object in the persistent storage. Therefore, each object in the persistent storage has a unique persistent pointer representation to indicate the location of the object in the persistent storage.
Every persistent pointer object except null pointers which point nowhere is generated by the allocation mechanisms. Thus, direct manipulation of the contents of the pointer object must be forbidden for the users. The necessary public operations for pointer objects are as follows:
These properties mean that the contents of the pointer objects are unchangeable by the user except assignment with null or another pointer.