Solving the Incremental Satisfiability Problem

Given a set of clauses in propositional logic that have been found satisfiable, we wish to check whether satisfiability is preserved when the clause set is incremented with a new clause. We describe an efficient implementation of the Davis-Putnam-Loveland algorithm for checking the satisfiability of the original set. We then show how to modify the algorithm for efficient solution of the incremental problem, which is NP-complete. We also report computational results.