The lexicographic closure as a revision process

The connections between nonmonotonic reasoning and belief revision are well-known. A central problem in the area of nonmonotonic reasoning is the problem of default entailment, i.e., when should an item of default information representing "if A is true then, normally, B is true" be said to follow from a given set of items of such information. Many answers to this question have been proposed but, surprisingly, virtually none have attempted any explicit connection to belief revision. The aim of this paper is to give an example of how such a connection can be made by showing how the lexicographic closure of a set of defaults may be conceptualised as a process of iterated revision by sets of sentences. Specifically we use the revision process of Nayak.Comment: 7 pages, Nonmonotonic Reasoning Workshop 2000 (special session on belief change), at KR200

Modifying Is Better Than Deleting: A New Approach To Base Revision

We present three approaches to belief base revision, which are examined also in the case in which the sentences in the base are partitioned between those which can and those which cannot be changed; the approaches are shown to be semantically equivalent. A new approach is then presented, based on the modification of individual rules, instead of deletion. The resulting base is semantically equivalent to that generated by the other approaches, in the sense that it has the same models, but the rule part alone has less models, that is, is subjected to a smaller change

Unanimous Consensus Against AGM?

Given the role consensus is supposed to play in the social aspects of inquiry and deliberation, it is important that we may always identify a consensus as the basis of joint inquiry and deliberation. However, it turns out that if we think of an agent revising her beliefs to reach a consensus, then, on the received view of belief revision, AGM belief revision theory, certain simple and compelling consensus positions are not always available

Multiple Revision on Horn Belief Bases

In logic programming, Horn clauses play a basic role, and in many logical constructs their consideration is important. In this paper we study the multiple revision of a belief base where the underlying logic is composed by Horn clauses. The main di culties as to restricting to the Horn fragment for revision operators by a single sentence are analyzed, and general results are presented about multiple revision operators on belief bases. We de ne prioritized multiple revision operators under a more restricted logic than classical propositional logic, i.e. Horn logic. We propose a set of postulates and representation theorems for each operation. This work is relevant for multiple revision in areas that employ Horn clauses, such as logic programming and deductive databases applications.XVII Workshop Agentes y Sistemas Inteligentes (WASI).Red de Universidades con Carreras en Informática (RedUNCI

Multiple Revision on Horn Belief Bases

In logic programming, Horn clauses play a basic role, and in many logical constructs their consideration is important. In this paper we study the multiple revision of a belief base where the underlying logic is composed by Horn clauses. The main di culties as to restricting to the Horn fragment for revision operators by a single sentence are analyzed, and general results are presented about multiple revision operators on belief bases. We de ne prioritized multiple revision operators under a more restricted logic than classical propositional logic, i.e. Horn logic. We propose a set of postulates and representation theorems for each operation. This work is relevant for multiple revision in areas that employ Horn clauses, such as logic programming and deductive databases applications.XVII Workshop Agentes y Sistemas Inteligentes (WASI).Red de Universidades con Carreras en Informática (RedUNCI

Analytic Modal Revision For Multi-Agent Systems

We present two models of hierarchical structured multi-agents, and we describe how to obtain a modal knowledge base from distributed sources. We then propose a computationally oriented revision procedure for modal knowledge bases. This procedure is based on a labelled tableaux calculi supplemented with a formalism to record the dependencies of the formulae. The dependencies are then used to reconstruct the minimal inconsistent sets, and the sub-formulae responsible for the inconsistencies are revised according to well-defined chains of modal functions

Overriding subsuming rules

International audienceThis paper is concerned with intelligent agents that are able to perform nonmonotonic reasoning, not only with, but also about general rules with exceptions. More precisely, the focus is on enriching a knowledge base Γ with a general rule that is subsumed by another rule already there. Such a problem is important because evolving knowledge needs not follow logic as it is well-known from e.g. the belief revision paradigm. However, belief revision is mainly concerned with the case that the extra information logically conflicts with Γ. Otherwise, the extra knowledge is simply doomed to extend Γ with no change altogether. The problem here is different and may require a change in Γ even though no inconsistency arises. The idea is that when a rule is to be added, it might need to override any rule that subsumes it: preemption must take place. A formalism dedicated to reasoning with and about rules with exceptions is introduced. An approach to dealing with preemption over such rules is then developed