Preface

Journal of Artificial Intelligence Research

The publication of the seminal issue on nonmonotonic logics by the Art ificial Intelligence Journal in 1980 resulted in a new area of research in kno wledge representation and changed the mainstream paradigm of logic that originated in antiquity. It established an important area of mathematical logic a nd led to discoveries of connections between logic, knowledge representat ion and computation which attracted not only computer scientists but also logician s, mathematicians and philosophers. Importantly, it also changed the pers pective on applications of logic. Nonmonotonic reasoning concerns situations when information is inc om-plete or uncertain. Thus, conclusions drawn lack ironclad certaint y that comes with classical logic reasoning.


A Review of Nonmonotonic Reasoning

AI Magazine

Once the topic has become well enough understood that it can be explained easily to paying customers, and stable enough that anyone teaching it is not likely to have to update his/her teaching materials every few months as new developments are reported, it can be considered to have arrived. Another reasonable indicator of the maturity of a subject, a milestone along the road to academic respectability, is the publication of a really good book on the subject--not another research monograph but a book that consolidates what is already known, surveys and relates existing ideas, and maybe even unifies some of them. Grigoris Antoniou's Nonmonotonic Reasoning is just such a milestone--well written, informative, and a good source of information on an important and complex subject. Neither is it surprising nor unreasonable that he devotes a lot of space to Reiter's (1980) default logic, which, along with Mc-Carthy's (1980) circumscription and Moore's (1985) autoepistemic logic, is one of the holy trinity of nonmonotonic reasoning. AI Magazine Volume 20 Number 3 (1999) ( AAAI) and it has been the basis of a number of different variants, all with their own strengths and weaknesses.


A Review of Nonmonotonic Reasoning

AI Magazine

It is possible to argue, relatively convincingly, that any research topic only begins to become mature when it appears on a syllabus somewhere. Once the topic has become well enough understood that it can be explained easily to paying customers, and stable enough that anyone teaching it is not likely to have to update his/her teaching materials every few months as new developments are reported, it can be considered to have arrived. Another reasonable indicator of the maturity of a subject, a milestone along the road to academic respectability, is the publication of a really good book on the subject -- not another research monograph but a book that consolidates what is already known, surveys and relates existing ideas, and maybe even unifies some of them. Grigoris Antoniou's Nonmonotonic Reasoning is just such a milestone -- well written, informative, and a good source of information on an important and complex subject. Since the idea was first mooted



Preferences and Nonmonotonic Reasoning

AI Magazine

We give an overview of the multifaceted relationship between nonmonotonic logics and preferences. We discuss how the nonmonotonicity of reasoning itself is closely tied to preferences reasoners have on models of the world or, as we often say here, possible belief sets. Selecting extended logic programming with answer-set semantics as a generic nonmonotonic logic, we show how that logic defines preferred belief sets and how preferred belief sets allow us to represent and interpret normative statements. Conflicts among program rules (more generally, defaults) give rise to alternative preferred belief sets. We discuss how such conflicts can be resolved based on implicit specificity or on explicit rankings of defaults.