Logic Programs with Ordered Disjunction

Logic programs with ordered disjunction (LPODs) contain a new connective which allows representing alternative, ranked options for problem solutions in the heads of rules: A × B intuitively means that if possible A , but if A is not possible, then at least B . The semantics of logic programs with ordered disjunction is based on a preference relation on answer sets. We show how LPODs can be implemented using answer set solvers for normal programs. The implementation is based on a generator, which produces candidate answer sets and a tester which checks whether a given candidate is maximally preferred and produces a better candidate if it is not. We also discuss the complexity of reasoning tasks based on LPODs and possible applications.     

带函数析取逻辑程序的无基集及其应用

基于回答集（也称稳定模型）语义的带函数析取逻辑程序是一种重要的知识表示和推理方法。由于判定一个析取逻辑程序是否有回答集是困难的（Σ2完全的）,目前还没有有效的方法来计算带函数析取逻辑程序的回答集,主要原因之一是检查一个集合是否是回答集是coNP完全的。提出了带函数析取逻辑程序无基集（unfounded sets）的概念,发现了空无基集（unfounded-free sets）与稳定模型之间的一一对应关系,在此基础上,证明了一个逻辑程序的模型是该程序的稳定模型当且仅当它们对应的一个命题公式是不可满足的,从而在理论上为计算带函数析取逻辑程序的回答集提供了一种有效的途径。     

Equilibrium logic

Equilibrium logic is a general purpose nonmonotonic reasoning formalism closely aligned with answer set programming (ASP). In particular it provides a logical foundation for ASP as well as an extension of the basic syntax of answer set programs. We present an overview of equilibrium logic and its main properties and uses.Partially supported by CICyT project TIC-2003-9001-C02, URJC project PPR-2003-39 and WASP (IST-2001-37004).     

描述逻辑程序系统的设计与实现

Eiter等人为语义网提出的回答集程序和描述逻辑相结合的描述逻辑程序,获得了本体上的非单调表达和推理能力。王以松等人证明了描述逻辑程序的完备化和环公式可以精确刻画描述逻辑程序的回答集。在此基础上,进一步证明了若完备化公式的模型不是回答集则一定存在终止环公式反例,它们是多项式时间可计算的。设计并实现了借助SAT求解器MiniSAT以及描述逻辑推理机RacerPro计算描述逻辑强回答集的原型DLP_SAT。实验结果表明,该原型能有效地计算一些熟知的描述逻辑程序的强回答集。     

人工智能中的推理方法

人工智能的一个重要目的就是用计算机实现推理,而对推理规律符号化必须使用命题逻辑和阶逻辑,本文介绍了关于命题逻辑的集合论解释,并对矢列演绎系统规则的有效性进行了证明。     

多Agen t 协商行为的效用分析

给出多Agent协商行为的一种统计模型以及效用函数的表达式,从统计的角度分析了多Agent协商行为的行为效用,并给出了相关参数的定性分析,从而为更好地设计多Agent系统的协商组织规则和协商策略提供了效用依据．     

约束逻辑程序的良基模型研究

在介绍约束逻辑程序的定义、可满足性及其稳定模型等概念的基础上,研究约束逻辑程序的正文字展开方法和约束原子的正文字前缀幂集方法,对展开前后逻辑程序的等价特性进行逻辑证明。分析正规逻辑程序良基模型的构建方法,以求得经展开得到的等价正规逻辑程序的最小不动点为切入,给出简单约束逻辑程序交替不动点的良基语义模型。经推理证明,该良基模型是合理的,用该模型的构建方法将约束逻辑程序转化为正规逻辑程序也是可行的。     

一个带破圈启发方法的回答集编程系统

回答集编程(answer set programming,ASP)是一种回答集语义下的逻辑编程范例,可应用于非单调推理,叙述式问题求解等领域.本文为ASP提出并实现了一种破圈启发方法与一种基部限制式前向搜索过程,所得到的系统称为LPS.实验结果显示,相对于其他经典的ASP系统,LPS能够有效地解决处于相变难区域中的逻辑程序,通常这些程序被认为是计算困难的.除此以外,通过使用被称为动态变元过滤(dynamic variable filtering,DVF)的技术,LPS可以在计算过程中极大地缩小搜索树的尺寸.     

从经典逻辑知识构建ASP知识库的新方法

回答集程序设计(ASP)是一种主流的非单调知识表示工具。为了能够在利用ASP求解问题过程中使用现有的以经典逻辑表示的知识,给出了一种把以谓词逻辑公式表示的约束型知识和定义型知识转化为ASP程序或知识库的新方法,并以实例说明了其有效性。该方法满足转化后ASP程序的回答集与原公式集的模型具有一一对应关系。在实际应用中,该方法提供了一项从现存的以谓词逻辑为表示语言的知识库,构建以ASP为知识表示语言的非单调知识库的技术。     

Logic, probability theory, and artificial intelligence - Part I: the probabilistic foundations of logic

Many AI researchers have come to be dissatisfied with approaches to their discipline based on formal logic. Various alternatives are often suggested, including probability theory. This paper investigates the intimate connection between probability theory and various logics. We show that probability theory, broadly conceived, may be used as a formal semantics for virtually any monotonic logic. Thus, rather than being seen as competing, it is more appropriate to view formal logics as very special cases of probability theory, usually special cases that are computationally more tractable than the more general theory. Thus, probability theory and logic should be seen as complementary. Viewing probability theory in this abstract way may help to shed light on various recalcitrant problems in AI. De nombreux chercheurs dans le domaine de l'intelligence artificielle manifestent une certaine insatisfaction vis-à-vis certaines approches basées sur la logique formelle. Diverses solutions sont souvent proposées, y compris la théorie des probabilityés. Cet article analyse la relation intime entre la théorie des probabilités et diverses logiques. Il est démontré que la théorie des probabilityés, conçue de manière générale, peut ětre utilisée comme une sémantique formelle pour presque toute logique monotonique. Au lieu de percevoir les logiques formelles comme étant en opposition, il est plus approprié de les considérer comme des cas trés spéciaux de la théorie des probabilityés, habituellement plus traitables au niveau calcul que la théorie plus générate. Par conséquent, la théorie des probabilityés et la logique doivent ětre percues comme des éléments complémentaires. Le fait de considérer la théorie des probabilityés d'une manière abstraite peut contribuer à la compréhension de divers problèmes ardus dans le domaine de l'intelligence artificielle.     

Intelligent control

A framework for intelligent control is presented and different approaches to intelligent control are reviewed in light of this framework. The topics discussed include knowledge-based control, fuzzy control, neural networks, fault diagnosis, single loop control and distributed control. The key ideas behind these approaches are outlined and it is indicated how they may be used to make control systems with significantly improved capabilities.     

从C. S. Peirce的存在图表到John F. Sowa的概念图表的形成来看人工智能的应用和发展

John F.Sowa的概念图表在现代人工智能的研究中得到了广泛的应用。本文从符号记号学和语言学的角度分析了从C.S.Peirce存在逻辑图表到John F.Sowa概念图表形成的过程。文章指出,存在图表是概念图表形成的基础,而概念图表是在存在图表的基础上对高阶图形逻辑的完善和发展。在分析过程中同时得出语言学和符号记号学的研究在人工智能发展中起到了重要作用;而在人工智能的研究和发展中跨学科研究是至关重要的。     

Towards a Logic of Perishable Propositions

Reasoning with uncertain information is a central issue for Artificial Intelligence and Information Systems. Consequently, a vast amount of studies and results devoted to this issue can be found in the literature.Curiously, reasoning with information whose uncertaintyvaries along time cannot be found so much in the literature. Dynamic reliability is a feature found rather frequently in many problems, e.g. in financial markets, meteorology and demographics.In this article we consider propositions whose information about truth evaluation is gradually lost with time. Our motivation has come from the information system under development within the project SIDAM—Distributed Information Systems for Mobile Agents (supported by FAPESP, grant 98/06138-2)—to provide citizens with information about urban automotive traffic in a large city.We propose functions of loss of information, and show how they can be used to characterize the obsolescence of propositional information in a logical system.     

Answer set based design of knowledge systems

The aim of this paper is to demonstrate that A-Prolog is a powerful language for the construction of reasoning systems. In fact, A-Prolog allows to specify the initial situation, the domain model, the control knowledge, and the reasoning modules. Moreover, it is efficient enough to be used for practical tasks and can be nicely integrated with programming languages such as Java. An extension of A-Prolog (CR-Prolog) allows to further improve the quality of reasoning by specifying requirements that the solutions should satisfy if at all possible. The features of A-Prolog and CR-Prolog are demonstrated by describing in detail the design of USA-Advisor, an A-Prolog based decision support system for the Space Shuttle flight controllers.