Embedding Defeasible Logic into Logic Programming

Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recently attracted considerable interest and that has found various applications. Defeasible logic and its variants are an important family of defeasible reasoning methods. So far no relationship has been established between defeasible logic and mainstream nonmonotonic reasoning approaches. In this paper we establish close links to known semantics of logic programs. In particular, we give a translation of a defeasible theory D into a meta-program P(D). We show that under a condition of decisiveness, the defeasible consequences of D correspond exactly to the sceptical conclusions of P(D) under the stable model semantics. Without decisiveness, the result holds only in one direction (all defeasible consequences of D are included in all stable models of P(D)). If we wish a complete embedding for the general case, we need to use the Kunen semantics of P(D), instead.Comment: To appear in Theory and Practice of Logic Programmin

Essays on impact of information technology

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.The five essays in this dissertation look at how specific information technologies (such as Electronic Document Management (EDM), Semantic Web and RuleML) and IT in general can be used to automate and standardize data and processes, enable faster and more accurate information flow, and improve individual as well as firm performance. The first essay is an analytical review-type study in which we provide a comprehensive survey of research literature about different complementary organizational assets that when coupled with IT can lead to higher firm performance. In the second essay, we study the causal effects of digitizing work on information workers' time- use and performance at a large insurance firm. We make causal inferences and obtain unbiased estimates by exploiting a quasi-experiment: the phased introduction of Electronic Document Management (EDM) across multiple offices at different dates. In addition to large changes in time-use and performance, we find that digitization leads to a decline in the substitutable routine labor input and an increase in complementary non-routine cognitive labor input at the information worker level. We also uncover a new micro-level mechanism, "IT-enabled slack", that explains how exactly IT can lead to payoff in terms of information worker productivity. In the third essay, we examine the IT productivity relationship using a large primary source firm-level dataset about IT investments that spans the 2003-2005 period. Given results from previous studies, we present evidence of an inverted U-shaped returns curve, with returns now close to what they were in pre-Internet era. The fourth essay explores what high-performing firms specifically do to gain the greatest benefits from their IT investments.(cont.) Through a set of matched interviews with multiple respondents at 138 firms, we find that data/process standardization and systems integration, level of application integration and several IT-specific cultural elements are positively correlated with IT impact on customer satisfaction. The fifth essay shows the first detailed realistic e-business application scenario that exploits capabilities of the SweetRules V2.1 toolset for e-contracting using the SweetDeal approach. SweetRules is a powerful integrated set of tools for semantic web rules and ontologies. SweetDeal is a rule-based approach to representation of business contracts.by Sumit Milap Bhansali.Ph.D

Dialogue Games in Defeasible Logic

In this paper we show how to capture dialogue games in Defeasible Logic. We argue that Defeasible Logic is a natural candidate and general representation formalism to capture dialogue games even with requirements more complex than existing formalisms for this kind of games. We parse the dialogue into defeasible rules with time of the dialogue as time of the rule. As the dialogue evolves we allow an agent to upgrade the strength of unchallenged rules. The proof procedures of (Antoniou, Billington, Governatori, Maher 2001) are used to determine the winner of a dialogue game

Ontology-based infrastructure for intelligent applications

Ontologies currently are a hot topic in the areas of knowledge management and enterprise application integration. In this thesis, we investigate how ontologies can also be used as an infrastructure for developing applications that intelligently support a user with various tasks. Based on recent developments in the area of the Semantic Web, we provide three major contributions. We introduce inference engines, which allow the execution of business logic that is specified in a declarative way, while putting strong emphasis on scalability and ease of use. Secondly, we suggest various solutions for interfacing applications that are developed under this new paradigm with existing IT infrastructure. This includes the first running solution, to our knowledge, for combining the emerging areas of the Semantic Web Services. Finally, we introduce a set of intelligent applications, which is built on top of onologies and Semantic Web standards, providing a proof of concept that the engineering effort can largely be based on standard components.Ontologien sind derzeit ein viel diskutiertes Thema in Bereichen wie Wissensmanagement oder Enterprise Application Integration. Diese Arbeit stellt dar, wie Ontologien als Infrastruktur zur Entwicklung neuartiger Applikationen verwendet werden können, die den User bei verschiedenen Arbeiten unterstützen. Aufbauend auf den im Rahmen des Semantischen Webs entstandenen Spezifikationen, werden drei wesentliche Beiträge geleistet. Zum einen stellen wir Inferenzmaschinen vor, die das Ausführen von deklarativ spezifizierter Applikationslogik erlauben, wobei besonderes Augenmerk auf die Skalierbarkeit gelegt wird. Zum anderen schlagen wir mehrere Lösungen zum Anschluss solcher Systeme an bestehende IT Infrastruktur vor. Dies beinhaltet den, unseres Wissens nach, ersten lauffähigen Prototyp der die beiden aufstrebenden Felder des Semantischen Webs und Web Services verbindet. Schließlich stellen wir einige intelligente Applikationen vor, die auf Ontologien basieren und somit großteils von Werkzeugen automatisch generiert werden können