Systems of defeasible reasoning are characterized by defeasible proofs, called arguments. I claim that sensible criteria of defeat among arguments in those systems are feasible, be it to a certain extent. As defeat eventually becomes unenforceable, the only option left is to pursue both arguments concurrently. This paper tries to confine the reach of defeat among arguments by means of several case studies, some of which are taken from the literature. 1. INTRODUCTION Reasoning beyond the information enclosed in the premises is a tempting but risky activity. It is tempting, because sheer deductive reasoning brings us no more than what was already recorded in the premises. And it is risky, because we might jump to the wrong conclusions. This is, very briefly, the issue of ampliative inference mechanisms. Ampliative inference can be defined as the result of rational non-deterministic non-monotonic reasoning (Loui, 1990). The term itself is suggested by the American philosopher Peirce (183...

This article discusses the problems and difficulties, the results so far, and some improvements in logic and logical languages that may be required to formalize common sense. Fundamental conceptual advances are almost certainly required. The object of the paper is to get more help for AI from philosophical logicians. Some of the requested help will be mostly philosophical and some will be logical. Likewise the concrete AI approach may fertilize philosophical logic as physics has repeatedly fertilized mathematics.

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We address the experiences of the DARPA High Performance Knowledge Bases (HPKB) (Cohen et al., 1998) project in practical knowledge representation. The purpose of the HPKB project was to develop new techniques for rapid development of knowledge bases. The goal of this paper is to describe several technical issues that arose in creation of practical KB content.

In this paper we extend Gelfond and Lifschitz' action description language A with concurrent actions and observation propositions to describe the predicted behaviour of domains of (concurrent) actions and actually observed behaviour, respectively, without requiring that the actually observed behaviour of a domain of actions be consistent with its predicted behaviour. We present a translation from domain descriptions and observations in the new action language to abductive normal logic programs. The translation is shown to be both sound and complete. From the stand-point of model-based diagnosis, in particular, we discuss the temporal explanation of inferring actions from fluent changes at two different levels, namely, at the domain description level and at the abductive logic programming level. The method is applicable to the temporal projection problem with incomplete information, as well as to the temporal explanation of inferring actions from fluent changes. 1 Introduction There ha...

Abstract. The event calculus is a powerful and highly usable formalism for reasoning about action and change. The discrete event calculus limits time to integers. This paper shows how discrete event calculus problems can be encoded in first-order logic, and solved using a first-order logic automated theorem proving system. The following techniques are discussed: reification is used to convert event and fluent atoms into first-order terms, uniqueness-of-names axioms are generated to ensure uniqueness of event and fluent terms, predicate completion is used to convert second-order circumscriptions into first-order formulae, and a limited first-order axiomatization of integer arithmetic is developed. The performance of first-order automated theorem proving is compared to that of satisfiability solving. 1