The present introduction to the Fluent Calculus is intended as an ETAI reference article. It summarizes basic definitions and concepts in the Fluent Calculus, and is intended as a reference for future articles where the calculus is used.

As a contribution to the challenge of building game-playing AI systems, we develop and analyse a formal language for representing and reasoning about strategies. Our logical language builds on the existing general Game Description Language and extends it by a standard modality for linear time along with two dual connectives to express preferences when combining strategies. The semantics of the language is provided by a standard state-transition model. As such, problems that require reasoning about games can be solved by the (...) standard methods for reasoning about actions and change. We also endow the language with a specific semantics by which strategy formulas are understood as move recommendations for a player. To illustrate how our formalism supports automated reasoning about strategies, we demonstrate two example methods of implementation: first, we formalise the semantic interpretation of our language in conjunction with game rules and strategy rules in the Situation Calculus; second, we show how the reasoning problem can be solved with Answer Set Programming. (shrink)

As an extension of the well-known Action Description Language A introduced by M. Gelfond and V. Lifschitz [8] C. Baral and M. Gelfond recently defined the diafect AC which supports the description of concurrent actions [1]. Also, a sound but incomplete encoding of AC by means of an extended logic program was presented there. In this paper, we work on interpretations of contradictory inferences from partial action descriptions. Employing an interpretation different from the one implicitly used in AC, we present (...) a new dialect which allows to infer sound information from contradictory descriptions and to describe non-determinism and uncertainty. Furthermore, we give the first sound and complete encoding of AC, using equational logic programming, and extend it to as well. (shrink)

A general game player automatically learns to play arbitrary new games solely by being told their rules. For this purpose games are specified in the general Game Description Language (GDL), a variant of Datalog with function symbols that uses a few game-specific keywords. A recent extension of basic GDL allows the description of nondeterministic games with any number of players who may have incomplete, asymmetric information. In this paper, we analyse the epistemic structure and expressiveness of this language in terms (...) of modal epistemic logic and prove two main results: (1) The operational semantics of GDL entails that the situation at any stage of a game can be characterised by a multi-agent epistemic (i.e., S5-) model; (2) GDL is sufficiently expressive to model any situation that can be described by a (finite) multi-agent epistemic model. (shrink)

A logic-based approach to the design of computing systems would, undoubtedly, offer many advantages over the imperative paradigm most commonly applied so far for programming and hardware design and, consequently, logic, again and again, has been heralded as the basis for the next generation of computer systems. While logic and formal methods are indeed gaining ground in many areas of computer science and artificial intelligence the expected revolution has not yet happened. In this book the author offers a convincing solution (...) to the ramification problem and qualification problem associated with the frame problem and thus contributes to a satisfactory solution of the core problem and related challenges. Thielscher bases his approach on the fluent calculus, a first-order Prolog-like formalism allowing for the description of actions and change. (shrink)