On the Duality of Fault Tolerant System Structures
SK Shrivastava, LV Mancini, Brian Randell · 1987
An examination of the structure of fault tolerant systems incorporating error recovery, and in particular backward error recovery, indicates a partitioning into two broad classes. Two canonical models, each representing a particular class of systems have been constructed. The first model incorporates objects and actions as the entities for program construction while the second model employs communicating processes. Applications in the areas such as office information and database systems typically use the first model while applications in the area of real time process control are usually based on the second model. The paper claims that the two models are duals of each other and presents arguments and examples to substantiate this claim, which is in effect, an extension of the earlier duality argument presented by Lauer and Needham. An interesting conclusion to be drawn from this study is that there is no inherent reason for selecting one model over the other, but that the choice is governed by the architectural features of the layer over which the system is to be constructed. A pleasing consequence has been the recognition that the techniques which have been developed for one model, turn out to have interesting and hitherto unexplored duals in the other model.