“…One of the issues involved in coupling a logic programming system and a database system is to resolve the mismatch between the tuple oriented access of the logic programming system and the set oriented retrieval of the database system. From the performance point of view, supporting partial match queries, join and other operations has been one of the major concerns in the back end (Gonzalez-Rubio et al, 1987;Sakai et al, 1986) since these operations are expected to occur more frequently than in conventional database systems. Consider, for example, the query <-p(a,X),q(c,b,c), and suppose that p and q are base relations (facts).…”