Answer Set Solving in Practice

Answer Set Programming (ASP) is a declarative problem solving approach, combining a rich yet simple modeling language with high-performance solving capacities. ASP is particularly suited for modeling problems in the area of Knowledge Representation and Reasoning involving incomplete, inconsistent, and changing information. From a formal perspective, ASP allows for solving all search problems in NP (and NP ) in a uniform way (being more compact than SAT). Applications of ASP include automatic synthesis of multiprocessor systems, decision support systems for NASA shuttle controllers, reasoning tools in systems biology, and many more. The versatility of ASP is also reflected by the ASP solver clasp, developed at the University of Potsdam, and winning first places at international ASP, PB, and SAT competitions. The tutorial aims at acquainting the participant with ASP’s modeling and solving methodology, enabling her/him to independent problem solving using ASP systems. To this end, the tutorial starts with an introduction to the essential formal concepts of ASP, needed for understanding its semantics and solving technology. In fact, ASP solving rests on two major components: A grounder turning specifications in ASP’s modeling language into propositional logic programs and a solver computing a requested number of answer sets of the given program. Building on the aforementioned formal concepts, we provide a characterization of ASP’s inference schemes that are in turn mapped into algorithms relying on advanced Boolean Constraint technology. Similarly, ASP’s grounding inferences are discussed in conjunction with (deductive) database techniques. The remainder of the tutorial is dedicated to applying ASP, involving an introduction to ASP’s modeling language, its solving methodology, and advanced techniques fostering scalability. The latter is illustrated via some real-world applications, taken from bio-informatics. All involved ASP systems are freely available from http://potassco.sourceforge.net.