Well-Founded Semantics for Extended Logic Programs with Dynamic Preferences

The paper describes an extension of well-founded semantics for logic programs with two types of negation. In this extension information about preferences between rules can be expressed in the logical language and derived dynamically. This is achieved by using a reserved predicate symbol and a naming technique. Conflicts among rules are resolved whenever possible on the basis of derived preference information. The well-founded conclusions of prioritized logic programs can be computed in polynomial time. A legal reasoning example illustrates the usefulness of the approach.Comment: See http://www.jair.org/ for any accompanying file

A comparison between non-monotonic formalisms

It is interesting and important to compare, analyze and assess the alternative tools that could be used in the area of Knowledge Representation. In this paper we present a reasearch line associated to this goal: to formally establish the relation among Knowledge Representation formalisms in order to make a sensible use of them. As a part of this main task, we present a comparison between Normal Default Theory and Defeasible Logic Programming. This comparison is achieved introducing a DELP variant, called DELP;, which allows to associate the answers of a DELP interpreter to the consequences, credulous and skeptical, of a Normal Default Theory.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

A comparison between non-monotonic formalisms

It is interesting and important to compare, analyze and assess the alternative tools that could be used in the area of Knowledge Representation. In this paper we present a reasearch line associated to this goal: to formally establish the relation among Knowledge Representation formalisms in order to make a sensible use of them. As a part of this main task, we present a comparison between Normal Default Theory and Defeasible Logic Programming. This comparison is achieved introducing a DELP variant, called DELP;, which allows to associate the answers of a DELP interpreter to the consequences, credulous and skeptical, of a Normal Default Theory.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

Computing Preferred Answer Sets by Meta-Interpretation in Answer Set Programming

Most recently, Answer Set Programming (ASP) is attracting interest as a new paradigm for problem solving. An important aspect which needs to be supported is the handling of preferences between rules, for which several approaches have been presented. In this paper, we consider the problem of implementing preference handling approaches by means of meta-interpreters in Answer Set Programming. In particular, we consider the preferred answer set approaches by Brewka and Eiter, by Delgrande, Schaub and Tompits, and by Wang, Zhou and Lin. We present suitable meta-interpreters for these semantics using DLV, which is an efficient engine for ASP. Moreover, we also present a meta-interpreter for the weakly preferred answer set approach by Brewka and Eiter, which uses the weak constraint feature of DLV as a tool for expressing and solving an underlying optimization problem. We also consider advanced meta-interpreters, which make use of graph-based characterizations and often allow for more efficient computations. Our approach shows the suitability of ASP in general and of DLV in particular for fast prototyping. This can be fruitfully exploited for experimenting with new languages and knowledge-representation formalisms.Comment: 34 pages, appeared as a Technical Report at KBS of the Vienna University of Technology, see http://www.kr.tuwien.ac.at/research/reports

A Parameterised Hierarchy of Argumentation Semantics for Extended Logic Programming and its Application to the Well-founded Semantics

Argumentation has proved a useful tool in defining formal semantics for assumption-based reasoning by viewing a proof as a process in which proponents and opponents attack each others arguments by undercuts (attack to an argument's premise) and rebuts (attack to an argument's conclusion). In this paper, we formulate a variety of notions of attack for extended logic programs from combinations of undercuts and rebuts and define a general hierarchy of argumentation semantics parameterised by the notions of attack chosen by proponent and opponent. We prove the equivalence and subset relationships between the semantics and examine some essential properties concerning consistency and the coherence principle, which relates default negation and explicit negation. Most significantly, we place existing semantics put forward in the literature in our hierarchy and identify a particular argumentation semantics for which we prove equivalence to the paraconsistent well-founded semantics with explicit negation, WFSX$_p$. Finally, we present a general proof theory, based on dialogue trees, and show that it is sound and complete with respect to the argumentation semantics.Comment: To appear in Theory and Practice of Logic Programmin

Nonmonotonic Integrity Constraints

Abstract. Semantics of multidimensional dynamic logic programming is traditionally based on the causal rejection principle: if there is a conflict between rules then the rule from a less preferred program is rejected. However, sometimes it is useful to solve a conflict between the heads of rules by blocking the body of a rule. Moreover, semantics based on the causal rejection principle, is not able to recognize conflicts, which are not manifested as conflicts between the heads of rules. Nonmonotonic integrity constraints are discussed in this paper. They provide alternative solutions of conflicts (as compared with solutions based on causal rejection principle). Conceptual apparatus introduced in this paper enables also to distinguish more preferred interpretations and, consequently, it is relevant for logic programming with preferences. Nonmonotonic integrity constraints and other notions introduced in the paper (falsified assumptions, more preferred assumptions) contribute to bridging the gap between research in fields as belief revision or preference handling on the one hand and multidimensional dynamic logic programming on the other hand

Psychiatric Diagnosis from the Viewpoint of Computational Logic

While medical information systems have become common in the United States present systems have mostly addressed clerical aspects of medicine such as billing, record managementand similar tasks. Deeper problems, such as aiding the process of diagnosis, have largely remmained unexplored for commercial systems. This is not surprising since automating diagnosisrequires considerable sophistication both in the understanding of psychiatric epidemeology andin knowledge representation techniques. This paper is an interdisciplinary study of how recent results in logic programming, non-monotonic reasoning, and knowledge representation can aidin psychiatric diagnosis. We argue that to logically represent psychiatric diagnosis as codified in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition requires abduction over programs that include both explicit and non-stratified default negation, as well as dynamic preference rules. We show how such programs can be translated into abductive frameworks over normal logic programs and implemented using recently introduced logic programming techhniques. Finally, we describe how such programs are used in a commercial product Diagnostica.authorsversionpublishe