A Default Logic Patch for Default Logic
نویسندگان
چکیده
This paper is about the fusion of multiple information sources represented using default logic. More precisely, the focus is on solving the problem that occurs when the standard-logic knowledge parts of the sources are contradictory, as default theories trivialize in this case. To overcome this problem, it is shown that replacing each formula belonging to Minimally Unsatisfiable Subformulas by a corresponding supernormal default allows appealing features. Moreover, it is investigated how these additional defaults interact with the initial defaults of the theory. Interestingly, this approach allows us to handle the problem of default theories containing inconsistent standard-logic knowledge, using the default logic framework itself.
منابع مشابه
A Proof Theoretical Approach to Default Reasoning I: Tableaux for Default Logic
We present a general proof theoretical methodology for default systems. Given a default theory 〈W, D〉, the default rules D are simply understood as restrictions on the tableaux construction of the logic. Different default approaches have their own way of understanding these restrictions and executing them. For each default approach (such as Reiter, Brewka or Lukaszewicz), the allowable default ...
متن کاملExpressing Default Logic Variants in Default Logic
Reiter’s default logic is one of the best known and most studied of the approaches to nonmonotonic reasoning. Several variants of default logic have subsequently been proposed to give systems with properties differing from the original. In this paper, we examine the relationship between default logic and its major variants. We accomplish this by translating a default theory under a variant inte...
متن کاملDefaults as restrictions on classical Hilbert-style proofs
Since the earliest formalisation of default logic by Reiter many contributions to this appealing approach to nonmonotonic reasoning have been given. The diierent formalisations are here presented in a general framework that gathers the basic notions, concepts and constructions underlying default logic. Our view is to interpret defaults as special rules that impose a restriction on the juxtaposi...
متن کاملFour-Valued Semantics for Default Logic
Reiter’s default logic suffers the triviality, that is, a single contradiction in the premise of a default theory leads to the only trivial extension which everything follows from. In this paper, we propose a default logic based on fourvalued semantics, which endows default logic with the ability of handling inconsistency without leading to triviality. We define four-valued models for default t...
متن کاملThe Modal Logic S4F, the Default Logic, and the Logic Here-and-There
The modal logic S4F provides an account for the default logic of Reiter, and several modal nonmonotonic logics of knowledge and belief. In this paper we focus on a fragment of the logic S4F concerned with modal formulas called modal defaults, and on sets of modal defaults — modal default theories. We present characterizations of S4F-expansions of modal default theories, and show that strong and...
متن کامل