Some Issues in Design of Distributed Deductive Databases

The design of a distributed deductive database system differs from the design of conventional non-distributed deductive database systems in that it requires design of distribution of both the database and rulebase. In this paper, we address the rule allocation problem. We consider minimisation of data communic& tion cost during rule execution as a primary basis for rule allocation. The rule allocation problem can be stated in terms of a directed acyclic graph, where nodes represent rules or relations, and edges represent either dependencies between rules or usage of relations by rules. The arcs are given weights representing volume of data that need to flow between the connected nodes. We show that rule allocation problem is NP-complete. Next, we propose a heuristic for nonreplicated allocation based on successively combining adjacent nodes for placement at same site which are connected by highest weight edge, and study its performance vib*vis the enumerative algorithm for optimal allocation. Our result8 show that the heuristic produces acceptable allocations. We also extend our heuristic for partially replicated allocation. Pelmiahm to wpu without jee all ot pall of this material ir punted pfwided that tbs copier are not made or didributd for direct commercial advantage, the VLDB copy+At notice and tbc title of the pmbliwtimI and it8 d&8 a-r, 8nd notiw i8 IivcntAoiwWing~~~~8iorroftAc Ve+lLwyc DdaBcuc Endowment. To copg othc&e, or to republish, rquimo o jce and/or special penniation jkom the Endowment. Proceedings of the 20th VLDB Conference Santiago, Chile, 1984 N. L. Sarda Dept. of Computer Science and Engg. Indian Institute of Technology, Bombay 400 076, INDIA nlsOcse.iitb.ernet .in