Fundamenta Informaticae - Volume 21, issue 1-2

Authors: Etherington, David | Kautz, Henry | Konolige, Kurt

Article Type: Other

DOI: 10.3233/FI-1994-211210

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 1-5, 1994

Authors: Stalnaker, Robert

Article Type: Research Article

Abstract: This paper is an attempt to articulate and respond to a philosophical problem about the general idea of a nonmonotonic consequence relation. The problem concerns the clarification of the target notion that various particular nonmonotonic theories, both model-theoretic and proof- theoretic, are attempting to explicate. Two different general conceptions are contrasted. The first is based on an idea of implicit content. According to this idea, a semantic interpretation assigns to the sentences of a language an explicit content in the usual way, and also an implicit content as a function of the explicit content, ψ is a nonmonotonic consequence of …φ if ψ is a consequence in the classical sense of the implicit content of the implicit content of φ. On this interpretation, nonmonotonic consequence is a deductive relation. According to the second idea, nonmonotonic reasoning concerns belief revision; to say that ψ is a nonmonotonic .consequence of φ is to say that ψ should be accepted in a belief state that is revised to accommodate the acceptance of φ. Some specific nonmonotonic theories, and some principles of nonmonotonic consequence, are considered from these two points of view. Show more

DOI: 10.3233/FI-1994-21121

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 7-21, 1994

Authors: Boddy, Mark | Goldman, Robert P. | Kanazawa, Keiji | Stein, Lynn Andrea

Article Type: Research Article

Abstract: Selman and Kautz's paper on the logic of model-preference defaults introduced a new language and tractability results. This paper assesses the contributions of that work, including the properties of the logic itself, its relationship to some previous logics, and its applicability to some known tractable problems.

DOI: 10.3233/FI-1994-21122

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 23-38, 1994

Authors: Besnard, Philippe | Schaub, Torsten

Article Type: Research Article

Abstract: We introduce a uniform semantical framework for various default logics in terms of Kripke structures. This possible worlds approach provides a simple but meaningful instrument for comparing existing default logics in a unified setting. The possible worlds semantics is introduced by means of constrained default logic. Also, it easily deals with Brewka's cumulative default logic. The semantics is then extended to Reiter's original default logic as well as Łukaszewicz' variant. The possible worlds approach remedies several difficulties encountered in former proposals aiming at individual default logics. Notably, it provides the first pure model-theoretic semantics for Łukaszewicz' variant of default logic. …Since the semantical framework is presented from the perspective of “commitment to assumptions” we also obtain a very natural modal interpretation of the notion of commitment. Show more

DOI: 10.3233/FI-1994-21123

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 39-66, 1994

Authors: Przymusinska, Halina | Przymusinski, Teodor

Article Type: Research Article

DOI: 10.3233/FI-1994-21124

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 67-87, 1994

Authors: Schwind, Camilla | Siegel, Pierre

Article Type: Research Article

Abstract: Hypothesis theory for nonmonotonic reasoning expresses notions of hypotheses and of known information. In this paper, we define these notions in the framework of a new modal system with two modalities, one for exprressing known information and the other for expressing possible hypotheses. A complete characterization of the new logic is given in terms of Kripke semantics. Moreover, our logic allows to characterize completely default logic, including a necessary and sufficient criterium for the existence and the non-existence of extensions. We also present a notion of nonmonotonic inference which is cumulative.

DOI: 10.3233/FI-1994-21125

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 89-101, 1994

Authors: Cadoli, Marco | Schaerf, Marco

Article Type: Research Article

Abstract: We propose a technique for dealing with the high complexity of reasoning under propositional default logic and circumscription. The technique is based on the notion of approximation: A logical consequence relation is computed by means of sound and progressively “more complete” relations, as well as complete and progressively “more sound” ones. Both sequences generated in this way converge to the original consequence relation and are easier to compute. Moreover they are given a clear semantics based on multivalued logic. With this technique unsoundness and incompleteness are introduced in a controlled way and precisely characterized.

DOI: 10.3233/FI-1994-21126

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 103-112, 1994

Authors: Bertossi, Leopoldo E. | Reiter, Raymond

Article Type: Research Article

Abstract: We investigate the possibility of using circumscription for characterizing the concept of a generic object in the context of a formalized mathematical theory. We show that conventional circumscriptive policies do not give the intuitively expected results for elementary geometry, and that there is a common explanation for this failure and the failure of circumscription in some standard instances of commonsense reasoning. It turns out, however, that scoped circumscription does provide the right mechanism for this task.

DOI: 10.3233/FI-1994-21127

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 113-123, 1994

Authors: McCarty, L. Thorne

Article Type: Research Article

Abstract: This paper combines a system of deontic logic with a system for default reasoning to analyze a notorious philosophical problem: Chisholm's Paradox. The basic approach is to write deontic rules with explicit exceptions, but we also consider the extent to which a set of implicit exceptions can be derived from the underlying deontic semantics.

DOI: 10.3233/FI-1994-21128

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 125-148, 1994

Authors: Ginsberg, Matthew L. | Holbrook, Hugh W.

Article Type: Research Article

Abstract: This paper extends existing work on the use of default information to describe planning hierarchies in two ways. First, we present a completeness result showing that all hierarchical planners can be described using defaults. Second, we show that if the planning hierarchy is situation-dependent, the default description is likely to have substantial computational advantages over a more conventional approach.

DOI: 10.3233/FI-1994-21129

Citation: Fundamenta Informaticae, vol. 21, no. 1-2, pp. 149-159, 1994