Progress report on the disjunctive deductive database system dlv

dlv is a deductive database system, based on disjunctive logic programming, which offers front-ends to several advanced KR formalisms. The system has been developed since the end of 1996 at Technische Universität Wien in an ongoing project funded by the Austrian Science Funds (FWF). Recent comparisons have shown that dlv is nowadays a state-of-the-art implementation of disjunctive logic programming. A major strength of dlv are its advanced knowledge modelling features. Its kernel language extends disjunctive logic programming by strong negation (a la Gelfond and Lifschitz) and integrity constraints; furthermore, front-ends for the database language SQL3 and for diagnostic reasoning are available. Suitable interfaces allow dlv users to utilize base relations which are stored in external commercial database systems. This paper provides an overview of the dlv system and describes recent advances in its implementation. In particular, the recent implementation of incremental techniques for program evaluation, as well as the use of relational join optimization strategies appear particularly relevant for deductive database applications. These techniques are suitably extended in dlv for the efficient instantiation of nonmonotonic programs. Benchmarks on problems from different domains are also reported to give a feeling of the current system performance.