Middleware such as CORBA-based products provides the commutlication infiûucture and inter-operability in a heterogeneous distributed environment. To achieve a high performance middleware software, the system architecture should be carefuüy considered. This thesis proposes an adaptive middleware architecture. which is called adaptive ORB, for CORBA-based systems. nie agent of the adaprive ORB that maps an object name to the object reference has two modes of operatioas. In the hanâle-dnven mode

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... retums a semer's handle to the client which uses this handle to send the request to the server. in the forwarding mode the agent forwards the entire client request to the semer which retums the result to the client The adaptive ORB dyniunically switches between these two modes depending on the cument system load. Based on measuremeats made on a network of workstations and a synthetic workload. we observe that the adaptive ORB can produce a significant benefit in performance in cornparison to a purely handle-dnven or a purely forwarding ORB. As a part time student, 1 would like to say it is really challenging to get this degree, particularly wîth thesis. 1 appreciate the strong support from my supervisor Professor, Shikharesh Majumdar, the informative suggestions frorn Istabrak N. Abdul-Fatah, and the friendship from the members of the RADS lab in Depanment of Systems and Cornputer Engineering. FinaUy, 1 would lüre to give my speciai thanks to my wife, ShuChuan Tsou. Without her support and encouragement, 1 could have never gone this far.