Quality-based flexibility in distributed objects

The paper discusses how to make a distributed object system flexible so as to satisfy the application´s requirement in the change of the system environment. Each object supports other objects with quality of service (QoS). The change of the system is modeled to be the change of not only types of service but also QoS supported by the objects. We discuss equivalency and compatibility relations among operations with respect to QoS. By using the QoS based relations, we discuss a QoS based compensating way to recover the object from the less qualified state. Finally, we discuss QoS based replication of objects to make required QoS available even if some replicas get less qualified; here, the replicas may not necessarily be the same