Parallel management of large deductive databases in a multi-processor environment

This paper describes a parallel deductive database system, built on top of Prolog. The system is based on the TOP-DOWN evaluation of logic programs. Parallelism is provided at the rule level, by transforming the query AND/OR tree into Disjunctive Normal Form. The clauses of the transformed formula are executed independently in parallel, on a transputer multi-processor machine, using the processor-farm algorithm. Both main-memory consultation and direct disk access have been implemented and tested. The measurement of the system performance shows speed improvement over the sequential Prolog interpreter, for large rule bases, but also exhibits implementation-dependent drawbacks that cause under-linear speed-up