Quantitative evaluation of a transaction facility for knowledge base management system

Abstract

Large knowledge bases that are intended for applications such as CAD, corporate repositories or process control will have to be shared by multiple users. For these systems to scale up, to give acceptable performance and to exhibit consistent behavior, it is mandatory to synchronize user transactions using a concurrency control algorithm. In this paper, we examine a novel concurrency control policy called Dynamic Directed Graph (or DDG) policy that effectively exploits the rich semantic structure of a knowledge base.Our analysis is carried out in the context of a real knowledge based system application from which knowledge base structure and workload parameters are computed. These serve as a basis for studying the implementation alternatives that arise as a result of knowledge base characteristics. The implementation alternatives that we consider include selection of portions of the knowledge base structure to be exploited for concurrency control, and also the dependence of concurrency on the traversal strategy used to search through the knowledge base. We analyze the effects of various workload parameters and conclude that the DDG policy improves substantially the response time for short transactions when there is heavy data contention.