Unsatisfiability-based optimization in clasp

Answer Set Programming (ASP) features effective optimization capacities based on branch-andbound algorithms. Unlike this, in the area of Satisfiability Testing (SAT) the finding of minimum unsatisfiable cores was put forward as an alternative approach to solving Maximum Satisfiability (MaxSAT) problems. We explore this alternative approach to optimization in the context of ASP. To this end, we extended the ASP solver clasp with optimization components based upon the computation of minimal unsatisfiable cores. The resulting system, unclasp, is based on an extension of the well-known algorithmsmsu1 andmsu3 and tailored to the characteristics of ASP. We evaluate our system on multi-criteria optimization problems stemming from realistic Linux package configuration problems. In fact, the ASP-based Linux configuration system aspuncud relies on unclasp and won four out of seven tracks at the 2011 MISC competition. 1998 ACM Subject Classification I.2.8 Problem Solving, Control Methods, and Search