This paper proposes a new logic programming language called GOLOG whose interpreter automatically maintains an explicit representation of the dynamic world being modeled, on the basis of user supplied axioms about the preconditions and effects of actions and the initial state of the world. This allows programs to reason about the state of the world and consider the effects of various possible courses of action before committing to a particular behavior. The net effect is that programs may be written at a much higher level of abstraction than is usually possible. The language appears well suited for applications in high level control of robots and industrial processes, intelligent software agents, discrete event simulation, etc. It is based on a formal theory of action specified in an extended version of the situation calculus. A prototype implementation in Prolog has been developed.

This paper describes a novel approach to high-level robot programming based on a highly developed logical theory of action. The user provides a specification of the robot's basic actions (their preconditions and effects on the environment) as well as of relevant aspects of the environment, in an extended version of the situation calculus. He can then specify robot behaviors in terms of these actions in a programming language that allows references to world conditions (e.g. if 9c(Pop can(c) On table(c)) then pick up(c)). The programs can be executed to drive the robot. The interpreter automatically maintains the world model required to execute programs based on the specification. The theoretical framework includes a solution to the frame problem and is very general --- it handles dynamic and incompletely known worlds, as well as perception actions. Given this kind of domain specification, it is also possible to support more sophisticated reasoning, such as task planni...

One way to think about STRIPS is as a mapping from databases to databases, in the following sense: Suppose we want to know what the world would be like if an action, represented by the STRIPS operator ff, were done in some world, represented by the STRIPS database D 0 . To find out, simply perform the operator ff on D 0 (by applying ff's elementary add and delete revision operators to D 0 ). We describe this process as progressing the database D 0 in response to the action ff. In this paper, we consider the general problem of progressing an initial database in response to a given sequence of actions. We appeal to the situation calculus and an axiomatization of actions which addresses the frame problem (Reiter [21]). This setting is considerably more general than STRIPS. Our results concerning progression are mixed. The (surprising) bad news is that, in general, to characterize a progressed database we must appeal to second order logic. The good news is that there are many useful spec...

This paper describes in general terms the particular forms of forgetting used in (Lin and Reiter [2; 3]). Specifically, we propose a logical theory to account for: forgetting about a fact (forget that John is a student), and forgetting about a relation (forget the student relation). We then apply our notion of forgetting in defining various notion of relevance.

This paper describes a novel approach to high-level agent programming based on a highly developed logical theory of action. The user provides a specification of the agents' basic actions (preconditions and effects) as well as of relevant aspects of the environment, in an extended version of the situation calculus. He can then specify behaviors for the agents in terms of these actions in a programming language where one can refer to conditions in effect in the environment. When an implementation of the basic actions is provided, the programs can be executed in a real environment; otherwise, a simulated execution is still possible. The interpreter automatically maintains the world model required to execute programs based on the specification. The theoretical framework includes a solution to the frame problem, allows agents to have incomplete knowledge of their environment, and handles perceptual actions. The theory can also be used to prove programs correct. A simple meeting sc...

. At a workshop held in Toulouse, France in 1977, Gallaire, Minker and Nicolas stated that logic and databases was a field in its own right (see [131]). This was the first time that this designation was made. The impetus for this started approximately twenty years ago in 1976 when I visited Gallaire and Nicolas in Toulouse, France, which culminated in a workshop held in Toulouse, France in 1977. It is appropriate, then to provide an assessment as to what has been achieved in the twenty years since the field started as a distinct discipline. In this retrospective I shall review developments that have taken place in the field, assess the contributions that have been made, consider the status of implementations of deductive databases and discuss the future of work in this area. 1 Introduction As described in [234], the use of logic and deduction in databases started in the late 1960s. Prominent among the developments was the work by Levien and Maron [202, 203, 199, 200, 201] and Kuhns [1...

this paper we extend the language A and its translation to allow reasoning about the effects of concurrent actions. The logic programming formalization of situation calculus with concurrent actions presented in the paper is of independent interest and may serve as a test bed for the investigation of various transformations and logic programming inference mechanisms. ! 1. INTRODUCTION

this paper. Similarly, we have shown that integrity constraints can apply to temporal conditions, but that there is no one uniform approach to handling temporal databases. Many areas of the use of integrity constraints still need investigating. Below, we discuss some aspects associated with this topic that require additional work. ffl Implement semantic query optimization and cooperative answering systems. Current relational and deductive database systems do not provide these capabilities, but the current 30 April 1997 ICs: Semantics and Applications---Godfrey, Grant, Gryz, & Minker p. 36 of 46 standards for SQL provide for the incorporation of some aspects of integrity constraints.

Ever since STRIPS was first introduced (Fikes and Nilsson [2]), its logical semantics has been problematic. There have been many proposals in the literature (e.g. Lifschitz [3], Pednault [7], Bacchus and Yang [1]). These all have in common a reliance on meta-theoretic operations on logical theories in order to capture the add and delete lists of STRIPS operators, but it has never been clear exactly what these operations correspond to declaratively, especially when they are applied to logically incomplete theories. In this paper we provide a semantics for STRIPS-like systems in terms of a purely declarative situation calculus axiomatization for actions and their effects. On our view, STRIPS is a mechanism for computing the progression (Lin and Reiter [5]) of an initial situation calculus database under the effects of an action. We illustrate this idea by specifying two different versions of STRIPS in the situation calculus. 1 Fellow of the Canadian Institute for Advanced Research 1 P...

The notion of computational agents has become very fashionable lately [24, 32]. Building such agents seems to be a good way of congenially providing services to users in networked computer systems. Typical applications are information retrieval over the internet, automation of common user activities, smart user interfaces,