View - Centric Reasoning in Modern Computing Systems

The development of distributed applications has not progressed as rapidly as its enabling technologies. In part, this is due to the difficulty of reasoning about such complex systems. One reason for the added complexity is the need for communication within modern computing systems. In contrast to sequential systems, parallel systems give rise to parallel events (communications), and the resulting uncertainty of the observed order of these events. Loosely coupled distributed systems complicate this even further by introducing the element of multiple imperfect observers of these parallel events. To address these challenges, we introduce view-centric reasoning, an approach to thinking about modern computing systems that directly supports multiple, inconsistent and imperfect views of computation. While view-centric reasoning is general enough to apply to any communication model, the focus of this paper is on computing systems that employ generative communication, a middleware-based distributed shared memory manipulated by a coordination (communication) language. In particular, we apply view-centric reasoning to tuple space based systems and the Linda coordination language. View-centric reasoning helps us resolve a potential ambiguity in the semantics of Linda predicate operations found in commercial implementations of tuple space, such as Sun's JavaSpaces and IBM's T Spaces.