DLP and FaCT

DLP [Patel-Schneider(1998)] and FaCT [Horrocks(1998)] are two recent description logic systems that contain sound and complete reasoners for expressive description logics. Due to the equivalences between expressive description logics and propositional modal logics, both DLP and FaCT can be used as satisfiability checkers for propositional modal logics. FaCT is a full-featured system that contains a highly-optimized satisfiability checker for a superset of K4(m). FaCT has an interface to allow the direct satisfiability checking of propositional modal formulae. FaCT is available from http://www.cs.man.ac.uk/~horrocks. DLP is an experimental system, designed to investigate various optimization techniques for description logic systems, including many of the optimizations pioneered in FaCT. DLP is available from http://www.bell-labs.com/user /pfps/dlp. DLP contains a highly-optimized satisfiability checker for a superset of Propositional Dynamic Logic (PDL), and includes a simple interface for the direct checking of the satisfiability of formulae in PDL. Both DLP and FaCT have performed very well on several comparisons of modal provers [Horrocks and Patel-Schneider(1998a),Horrocks and Patel-Schneider(1998b)]. The remainder of this submission will concentrate on DLP, as it is somewhat faster than FaCT. Significant differences from FaCT will be noted.