This monograph provides a thorough analysis of two important formalisms for nonmonotonic reasoning: default logic and modal nonmonotonic logics. It is also shown how they are related to each other and how they provide the formal foundations for logic programming. The discussion is rigorous, and all main results are formally proved. Many of the results are deep and surprising, some of them previously unpublished. The book has three parts, on default logic, modal nonmonotonic logics, and connections and complexity issues, respectively. The study of general default logic is followed by a discussion of normal default logic and its connections to the closed world assumption, and also a presentation of related aspects of logic programming. The general theory of the family of modal nonmonotonic logics introduced by McDermott and Doyle is followed by studies of autoepistemic logic, the logic of reflexive knowledge, and the logic of pure necessitation, and also a short discussion of algorithms for computing knowledge and belief sets. The third part explores connections between default logic and modal nonmonotonic logics and contains results on the complexity of nonmonotonic reasoning. The ideas are presented with an elegance and unity of perspective that set a new standard of scholarship for books in this area, and the work indicates that the field has reached a very high level of maturity and sophistication. The book is intended as a reference on default logic, nonmonotonic logics, and related computational issues, and is addressed to researchers, programmers, and graduate students in the Artificial Intelligence community.

When I first participated in exploring theories of nonmonotonic reasoning in the late 1970s, I had no idea of the wealth of conceptual and mathematical results that would emerge from those halting first steps. This book by Wiktor Marek and Miroslaw Truszczynski is an elegant treatment of a large body of these results. It provides the first comprehensive treatment of two influen tial nonmonotonic logics - autoepistemic and default logic - and describes a number of surprising and deep unifying relationships between them. It also relates them to various modal logics studied in the philosophical logic litera ture, and provides a thorough treatment of their applications as foundations for logic programming semantics and for truth maintenance systems. It is particularly appropriate that Marek and Truszczynski should have authored this book, since so much of the research that went into these results is due to them. Both authors were trained in the Polish school of logic and they bring to their research and writing the logical insights and sophisticated mathematics that one would expect from such a background. I believe that this book is a splendid example of the intellectual maturity of the field of artificial intelligence, and that it will provide a model of scholarship for us all for many years to come. Ray Reiter Department of Computer Science University of Toronto Toronto, Canada M5S 1A4 and The Canadian Institute for Advanced Research Table of Contents 1 1 Introduction ........."

This book constitutes the thoroughly revised and refereed post-workshop documentation of two international workshops held in conjunction with the Pacific Rim International Conference on Artificial Intelligence, PRICAI'96, in Cairns, Australia, in August 1996.
The volume presents 14 revised full papers togehter with two invited contributions and two introductory surveys particularly commissioned for this book. Among the topics addressed are computational learning, commonsense reasoning, constraint logic programming, fuzzy reasoning, vague data, inductive inference, belief revision, action theory, uncertainty, and probabilistic diagnosis.

This volume contains the refereed proceedings of the 13th International Conference on Logic Programming and Nonmonotonic Reasoning, LPNMR 2015, held in September 2015 in Lexington, KY, USA. The 290long and 11 short papers presented together with 3 invited talks, the paper reporting on the Answer Set Programming competition, and four papers presented by LPNMR student attendees at the doctoral consortium were carefully reviewed and selected from 60 submissions. LPNMR is a forum for exchanging ideas on declarative logic programming, nonmonotonic reasoning, and knowledge representation. The aim of the LPNMR conferences is to facilitate interactions between researchers interested in the design and implementation of logic-based programming languages and database systems, and researchers who work in the areas of knowledge representation and nonmonotonic reasoning.

This Festschrift is published in honor of Gerhard Brewka on the occasion of his 60th birthday and contains articles from fields reflecting the breadth of Gerd's work. The 24 scientific papers included in the book are written by close friends and colleagues and cover topics such as Actions and Agents, Nonmonotonic and Human Reasoning, Preferences and Argumentation.

The publication of the seminal special issue on nonmonotonic logics by the Artificial Intelligence Journal in 1980 resulted in a new area of research in knowledge representation and changed the mainstream paradigm of logic that originated in antiquity. It led to discoveries of connections between logic, knowledge representation and computation, and attracted not only computer scientists but also logicians, mathematicians and philosophers. Nonmonotonic reasoning concerns situations when information is incomplete or uncertain. Thus, conclusions drawn lack iron-clad certainty that comes with classical logic reasoning. New information, even if the original one is retained, may change conclusions. Formal ways to capture mechanisms involved in nonmonotonic reasoning, and to exploit them for computation as in the answer set programming paradigm are at the heart of this research area. The conference NonMon@30 - Thirty Years of Nonmonotonic Reasoning, held in Lexington, KY, USA, October 22-25, 2010, aimed to sum up the experience of the first 30 years of nonmonotonic logics and to map paths into the future. It comprised eighteen invited talks and several technical presentations. The present volume consists of the texts based on twelve of the invited presentations. These papers offer unique insights into the key questions that have been driving the development of nonmonotonic reasoning and suggest problems worthy of consideration in the future. They paint the picture of the field that has a well-established tradition, and remains vibrant and relevant to long-term goals of artificial intelligence.