Unification of Bounded Simple Set Terms in Deductive Databases

In this paper we consider the problem of uniication of bounded simple set terms in the eld of deductive databases. Simple set terms are of the form fe 1 ; : : : ; e n g, where e i is a constant or a variable and are much used in deductive database systems such as LDL and Coral. In this paper we consider a restricted form of uniication, called \weak uniication", which is mainly used in the eld of deductive databases where the database may contain both constants and variables and the program is \safe". The main results are: (a) the detailed complexity analysis of the weak uniication problem by providing a formula for determining the number of weak uniiers, and (b) the invention of an optimal weak uniication algorithm.