40 research outputs found
Approximating Operators and Semantics for Abstract Dialectical Frameworks
We provide a systematic in-depth study of the semantics of abstract dialectical frameworks (ADFs), a recent generalisation of Dung\''s abstract argumentation frameworks. This is done by associating with an ADF its characteristic one-step consequence operator and defining various semantics for ADFs as different fixpoints of this operator. We first show that several existing semantical notions are faithfully captured by our definition, then proceed to define new ADF semantics and show that they are proper generalisations of existing argumentation semantics from the literature. Most remarkably, this operator-based approach allows us to compare ADFs to related nonmonotonic formalisms like Dung argumentation frameworks and propositional logic programs. We use polynomial, faithful and modular translations to relate the formalisms, and our results show that both abstract argumentation frameworks and abstract dialectical frameworks are at most as expressive as propositional normal logic programs
Proving Non-Termination via Loop Acceleration
We present the first approach to prove non-termination of integer programs
that is based on loop acceleration. If our technique cannot show
non-termination of a loop, it tries to accelerate it instead in order to find
paths to other non-terminating loops automatically. The prerequisites for our
novel loop acceleration technique generalize a simple yet effective
non-termination criterion. Thus, we can use the same program transformations to
facilitate both non-termination proving and loop acceleration. In particular,
we present a novel invariant inference technique that is tailored to our
approach. An extensive evaluation of our fully automated tool LoAT shows that
it is competitive with the state of the art
Modal logics of sabotage revisited
Sabotage modal logic was proposed in 2003 as a format for analysing games that modify graphs they are played on. We investigate some model-theoretic and proof-theoretic aspects of sabotage modal logic, which has come to be viewed as an early dynamic logic of graph change. Our first result is a characterization theorem for sabotage modal logic as a fragment of first-order logic which is invariant with respect to a natural notion of âsabotage bisimulationâ. Next, we offer a sound and complete tableau method and its associated labelled sequent calculus for analysing reasoning in sabotage modal logic. Finally, we identify and briefly explore a number of open research problems concerning sabotage modal logic that illuminate its complexity, placing it within the current landscape of modal logics that analyse model update, and, returning to the original motivation of sabotage, fixed-point logics for network games
Proceedings of the 11th Workshop on Nonmonotonic Reasoning
These are the proceedings of the 11th Nonmonotonic Reasoning Workshop. The aim of this series is to bring together active researchers in the broad area of nonmonotonic reasoning, including belief revision, reasoning about actions, planning, logic programming, argumentation, causality, probabilistic and possibilistic approaches to KR, and other related topics. As part of the program of the 11th workshop, we have assessed the status of the field and discussed issues such as: Significant recent achievements in the theory and automation of NMR; Critical short and long term goals for NMR; Emerging new research directions in NMR; Practical applications of NMR; Significance of NMR to knowledge representation and AI in general