Exploiting temporal and spatial constraints on distributed shared objects

Gigabit network technologies have made it possible to combine workstations into a distributed, massively-parallel computer system. Middleware, such as distributed shared objects (DSO), attempts to improve programmability of such systems, by providing globally accessible `object´ abstractions. Researchers have developed consistency protocols for replicated `memory´ objects. These protocols are well suited to scientific applications but less suited to multimedia or groupware applications. We address the state sharing needs of complex distributed applications with: high-frequency symmetric accesses to shared objects; unpredictable and limited locality of accesses; dynamically changing sharing behavior; and potential data races. We show that a DSO system exploiting application-level temporal and spatial constraints on shared objects can outperform shared object protocols which do not exploit application-level constraints. We compare our S(emantic) DSO against entry consistency using a sample application having the four properties mentioned above