Quality-Based Flexibility in Distributed Objects

This paper discusses how to make a distributed object system exible 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 newly discuss a QoS-based compensating way to recover the object from the less quali ed state. Finally, we discuss QoS-based replication of objects to make required QoS available even if some replicas get less quali ed. Here, the replicas may not necessarily be the same.