Resolution of Type Mismatches in a Persistent Object System Alok Mehta David L. Spooner Martin Hardwick Many applications of object-oriented systems benefit from the ability to make objects persistent. To be fully effective, this persistence must be provided in such a way as to allow both the database of persistent objects and the applications to evolve. As they evolve, upward compatibility must be maintained so that new versions of applications can continue to use existing persistent objects and vice versa. This implies that a persistent object system must be able to handle type mismatches between objects in secondary storage and objects in an application program. In this paper, we formalize some of the categories of type mismatches that can occur as a result of application program and database evolution. We show how the concept of an object manager can be used to resolve many of the mismatches in these categories. Finally, we discuss how object managers have been incorporated into a particular persistent object system under development at Rensselaer Polytechnic Institute. Department of Computer Science, Rensselaer Polytechnic Institute, Troy, NY cs-92-08
Resolution of Type Mismatches in a Persistent Object System
Alok Mehta
David L. Spooner
Martin Hardwick
Many applications of object-oriented systems benefit from the ability to make objects persistent. To be fully effective, this persistence must be provided in such a way as to allow both the database of persistent objects and the applications to evolve. As they evolve, upward compatibility must be maintained so that new versions of applications can continue to use existing persistent objects and vice versa. This implies that a persistent object system must be able to handle type mismatches between objects in secondary storage and objects in an application program. In this paper, we formalize some of the categories of type mismatches that can occur as a result of application program and database evolution. We show how the concept of an object manager can be used to resolve many of the mismatches in these categories. Finally, we discuss how object managers have been incorporated into a particular persistent object system under development at Rensselaer Polytechnic Institute.
Department of Computer Science, Rensselaer Polytechnic Institute, Troy, NY
cs-92-08