Realizing a Adaptable Distributed Object-Oriented Computing Environment by Using Reconfigurable Object

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In large scale open distributed computing environments, runtime environments, such as performance and reliability, are continuously changing. If a user wants the system to preserve some level of performance and reliability in spite of change of runtime environments, the system should adapt itself to change of runtime environments. These changes are not predictable in the life time of systems or applications.In this research, we proposed a reconfigurable object that can reconfigure itself according to change of the runtime environment. The reconfigurable object consists of some functional meta-objects as well as a user defined meta-object. When the reconfigurable object detects a change of runtime environment, it exchanges some functional meta-objects to another one to adapt itself to the change. To make it easy for a reconfigurable object to exchange its meta-objects, we adopted loosely-coupled communication between meta-objects. Thus the distributed system that is composed of the reconfigurable objects has an ability to adapt to its runtime environment.We confirmed that our ideas can be realized by implementing the proto-type of reconfigurable objects and an environment change detection mechanism. Moreover, we showed following four application areas of the system. The first one is adaptable fault tolerance, which adapts the system to change of the underlying system's reliability and user required level of reliability. The second one is adaptable remote access, which solves the trade-off between cost and quality of data on accessing remote data, according to change of system performance. The third one is a quorum reconfiguration on the occasion of change of mutual exclusion group members. The last one is adaptable message ordering protocols, which selects the cost effective protocols even if system performance changes. Through these examples, we confirmed that reconfigurable objects are useful to realize a cost effective, robust and reliable distributed system.