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 Many of the results are deep and surprising, some of them previously unpublished.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.

The participation of such diverse scientific and technical disciplines as meteorology, astronomy, atmospheric electricity, ionospheric and magnetospheric physics, electromagnetic wave propagation, and radio techniques in the research of atmospherics means that results are published in scientific papers widely spread throughout the literature. This Handbook collects the latest knowledge on atmospherics and presents it in two volumes. Each chapter is written by an expert in his or her field. Topics include the physics of thunderclouds, thunder, global atmospheric electric currents, biological aspects of sferics, and various space techniques for detecting lightning within our own atmosphere as well as in the atmospheres of other planets. Up-to-date applications and methodology are detailed. Volumes I and II offer a comprehensive discussion that together will serve as an important resource for practitioners, professionals, and students alike.

The participation of such diverse scientific and technical disciplines as meteorology, astronomy, atmospheric electricity, ionospheric and magnetospheric physics, electromagnetic wave propagation, and radio techniques in the research of atmospherics means that results are published in scientific papers widely spread throughout the literature. This Handbook collects the latest knowledge on atmospherics and presents it in two volumes. Each chapter is written by an expert in his or her field. Topics include the physics of thunderclouds, thunder, global atmospheric electric currents, biological aspects of sferics, and various space techniques for detecting lightning within our own atmosphere as well as in the atmospheres of other planets. Up-to-date applications and methodology are detailed. Volumes I and II offer a comprehensive discussion that together will serve as an important resource for practitioners, professionals, and students alike.

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 ........."

These Proceedings are published to give a full account of the Fifth International Conference on Atmospheric Electricity held in September 1974 in Garmisch-Partenkirchen in the Bavarian Alps in Germany. Traditionally, the Proceedings of these Conferences have served as reference books updating the textbooks and monographs on Atmospheric Electricity. As treated by these Conferences, Atmos pheric Electricity covers all aspects of this science, including the processes and problems which reach out into the Earth's environment as well as analogous processes on other planets and on the Moon. A history of these Conferences, an account of their purpose, and an outline of the scope and the preparation is to be found at the end of these Proceedings. There, also the Business Meetings of the involved organizations are mentioned. The Proceedings closely follow the original program and are accordingly organized into "Sessions." The papers printed in each "Session" in this book are the ones which were accepted for the sessions of the Conference with the same numbers and titles. Only the two "Special Sessions" have been given different numbers in the Proceedings, i.e. 2a and 10. In principle, all papers which were accepted by the Executive Panel either for full oral presentation or for printing in the Proceedings only, have in fact been included in these Proceedings, whether they were presented or not. In the latter case, a special note is made to explain the absence of a discussion."

Die alten Vorstellungen, wonach die Erdatmosphare lediglich infolge der darin enthaltenen Gase, die sich an den Atmungsvorgangen in den lebenden Organismen beteiligen, fUr die Aufrechterhaltung und den un- gestarten Ablauf des menschlichen Lebens von Bedeutung ist, haben sich durch die Ergebnisse der wissenschaftlichen Forschung in unserem Jahr- hundert nicht unwesentlich geandert. Die Erdatmosphare wird nicht mehr als eine Mischung der fur die Atmung notwendigen Gase betrachtet, sondern als ein kompliziert zusammengesetzter Karper, in dem auBer den grundsatzlichen Gaskomponenten auch andere Komponenten in flussiger llnd fester Phase vorhanden sind. Diese letztgenannten Bestandteile der Atmosphare stellen zwar, mengenmaBig gesehen, nur verhaltnis- maBig kleine und kleinste Beimischungen dar, kannen aber bei ge- gebenen Verhaltnissen eine wesentliche Bedeutung fur den Ablauf der Lebensprozesse gewinnen. In erster Linie mussen hierbei die geladenen und ungeladenen Aerosole, die "Luft, ionen", Kondensationskerne und graBere Partikel bis zu den Staub en und radioaktiven Teilchen - besser gesagt: verschiedene Trager der Radioaktivitat - genannt werden. Ab- gesehen davon ist die Erdatmosphare als Tragerin elektrischer und akustischer Felder zu betrachten, die ebenfalls den Ablauf der Lebens- prozesse beeinflussen kannen. So entstand ein weites Gebiet der bio- physikalischen Erforschung der Erdatmosphare, die Biometeorologie u. a. m. Verstandlicherweise sind mit diesen Forschungsrichtungen die ein- schlagigen Problemstellungen der Klimatologie und Balneologie eng ver- bunden. Seit Beginn der Atomkernenergie-Epoche haben die einschlagigen Forschungsarbeiten an Bedeutung gewonnen und sind sehr aktuell ge- worden. Das vorliegende Werk von Herrn Dr.