This article introduces a class of incremental learning procedures specializedfor prediction that is, for using past experience with an incompletely knownsystem to predict its future behavior. Whereas conventional prediction-learningmethods assign credit by means of the difference between predicted and actual outcomes,tile new methods assign credit by means of the difference between temporallysuccessive predictions. Although such temporal-difference method~ have been used inSamuel's checker player, Holland's bucket brigade, and the author's Adaptive HeuristicCritic, they have remained poorly understood. Here we prove their convergenceand optimality for special cases and relate them to supervised-learning methods. Formost real-world prediction problems, telnporal-differenee methods require less memoryand less peak computation than conventional methods and they produce moreaccurate predictions. We argue that most problems to which supervised learningis currently applied are really prediction problemsMachine Learning 3: 9-44, erratum p. 377

Kvetoslav "Slava" Prazdny, who died September 19, 1987 in a hang-gliding accident in the California mountains, was recognized internationally as an expert in many aspects of human and machine perception. He had published over 60 articles reporting research in human perception, stereo vision, image processing, robotics, perceptual reasoning and learning, adaptive neural networks, and psychophysics. A redwood tree in Big Basin State Park is dedicated in his memory.

Sargur N. Srihari is a professor and acting chairman of the Department of Computer Science, State University of New York (SUNY) at Buffalo. The author of "Recognizing Address Blocks on Mail Pieces," Srihari is an associate editor of the journal Pattern Recognition and is chairman of the technical committee on text-processing applications of the International Mike Baird, who coauthored the tribute to Kvetoslav Prazdny, is manager of Association for Pattern Recognition. Srihari is also currently directing two Intelligence Center 1185 Coleman Avenue, Santa Clara, California 95052. Jeffrey Stone is a consultant who watches the computer industry and Jonathan J. Hull is a research assistant Digital Equipment Corporation that reports new developments and trends. The opinions expressed "Recognizing Address Blocks on Mail address is Knowledge Systems Corporation, in his article are his own. Jeffrey Stout is on the research staff of computer vision, and artificial intelligence. An Expert Elevator report on AI and education, is an Buffalo, where he is also currently Designer that Uses Knowledge-Based associate professor in the Department working on his Ph.D. His research Backtracking." of Mathematics and Computer Science interests include image processing, at Millersville University, computer graphics, and computer segmentation Jay M. Tenenbaum, who coauthored Millersville, Pennsylvania 1755 1. Palumbo is a the tribute to Kvetoslav Prazdny, is a coauthor of "Recognizing Address Schlumberger Fellow at the Schlumberger John McDermott is a principal scientist Blocks on Mail Pieces."

He then the Sempervirens Fund Anyone wishing Kvetoslav "Slava" Prazdny died in a completed a Ph.D. in Computer Science to make a tribute can do so in Slava's hang-gliding accident, Saturday, at the University of Essex. His name to The Sempervirens Fund, P 0 September 19th, 1987, in the California work reflected the marriage of these Drawer BE, Los Altos, California 94023 mountains. He is survived by his disciplines, as he strove to develop wife, Dagmar Dolan, and his 15 year formal computational models of old daughter Bronja Prazdny. During He was a member of American his prolific career, he had published Association for Advancement of Science, over 60 journal articles reporting American Association for Artificial research in human perception, Intelligence, The Cognitive Science stereo vision, image processing, Society, The Psychonomic Soci-robotics, perceptual reasoning and ety, International Society for Ecological learning, adaptive neural networks, Psychology, Society for Information and psychophysics. Display, SPIE, and a Fellow of the Slava derived his greatest pleasure New York Academy of Sciences.

As Soloway attracted over 400 pnrticipants from all of Pittsburgh, Pittsburgh, Penn., described the changes in what he felt over the world who gathered to present 8-10 May 1987. The conference the construction of mechanisms and concerning AI and education This article cochairmen, Stellan Ohlsson and explanations last year to the design of presents a synopsis of the major Jeff Bonar, also gave brief welcomes to artifacts today, he was clearly giving presentations and an overview the participants. With so about transference, leading Soloway many attendees from abroad (The to conclude that transference is not Netherlands, Japan, Canada, West the ultimate goal for teaching and Germany, England, Sweden, France, tutoring programming. Instead, the and Hong Kong were all represented concern should be for the development by speakers), the international flavor of synthesis skills and "highorder of the conference was well established. The obvious disappointment This model does not vary significantly of the audience could be from standard software engineering felt. However, instead of giving the opening address, "Programming requiring these steps be followed in a as Artifact Design." This change strict order, Soloway contends that worked out well because Soloway the way real programmers work best acted like a cheerleader, getting the is to bounce from one stage to another crowd fired up about the subject of AI as the need arises. WINTER 1987 97 Andy di Sessa, in his talk "Social much rigidity has recently been the differences between beginner and Niches for Future Software," focused imposed on programmers by the engi-expert. Finally, Wender suggested that on the need to provide a medium neering approach. He demonstrated him, one could easily mistake him for teacher. Some of the kinds of software he felt should ... He considers current applications to be "the He also suggested that "current programming is to synthesis as a hammer is to a thumb. Each is as likely to challenge to the computer science der was echoed by Ben du Boulay in cause pain as [it is] to get the job community to develop higher-level "What Should a Programming Environment done." The Like?" Bonar's comment in his opening Beyond the usual categories supplied emphasis should be on synthesis welcome that we are "on the verge by the conference structure, several skills for designing, generating, and of a breakthrough" in developing themes linked many of the papers evaluating alternative artifacts that tutoring systems concerned du and presentations.

A number of tools that support the development, execution, and maintenance of knowledge-based systems are marketed commercially. Many of these tools, however, are designed for applications that can be executed on personal computers and are not suitable for building large knowledge-based systems. The market for knowledge engineering tools designed for applications that require the computational power of a Lisp machine or an engineering workstation is dominated by a few vendors. This article is an assessment of the current state of tools used to build large knowledge-based systems. This assessment is based on the collective strengths and weaknesses of several tools that have been evaluated. In addition, an estimate is made of the features that will be required in the next generation of tools.

In the restaurant script, notated as $RESTAURANT, the roles might directly to the United Press International Yale researchers explored intentionality include customer, waitress, and cook; news wire and could skim news One of the earliest programs to the props could be a menu, table, and stories in dozens of different domains, embody goals and plans within the silverware; the locations could be the and produce summaries in several languages. CD paradigm was Jim Meehan's bar, dining area, and kitchen; and the On the DEC-20 (which by TALESPIN, which made up stories events would include arriving, seating, 1978 had replaced the PDP-101, similar to the fables of Aesop.

VT (vertical transportation) is an expert system for handling the design of elevator systems that is currently in use at Westinghouse Elevator Company. Although VT tries to postpone each decision in creating a design until all information that constrains the decision is known, for many decisions this postponement is not possible. In these cases, VT uses the strategy of constructing a plausible approximation and successively refining it. VT uses domain-specific knowledge to guide its backtracking search for successful refinements. The VT architecture provides the basis for a knowledge representation that is used by SALT, an automated knowledge-acquisition tool. SALT was used to build VT and provides an analysis of VT's knowledge base to assess its potential for convergence on a solution.

We offer a simple mechanism, that of metalingual definition (D. G. Hays, The Meaning of a Term is a Function of the Theory in Which It Occurs, SIGLASH Newsletter, 1973, 6, 4:S-11).

The (CSCW '86) was held in Austin, participants). The three-day report introduces the field of computersupported Texas, on 3-5 December 1986. It was event included nine paper sessions: cooperative work, describes the sponsored by the Microelectronics supporting face-to-face groups, empirical CSCW '86 program, and discusses the significance and Computer Technology Corporation studies, supporting distributed of the conference results An (MCC) Software Technology Program groups, hypertext systems, underlying introduction to the follow-on conference, in cooperation with the Association technology for collaborative systems, CSCW '88, is also provided for Computing Machinery (ACM) collaboration research, multimedia and its special interest groups on software and multiuser interfaces, industrial engineering (SIGSOFT), human experiences with CSCW, and coordination computer interaction (SIGCHI), and and decision making. There office information systems (SIGOIS); were also four panel sessions; the topics the Institute for Electrical and Electronic were collaboration and offices, collaborative Engineers (IEEE) Computer design studies, from theories Society; the American Association for to systems, and trends and markets Artificial Intelligence (AAAI); The for computer-supported group Information Management Society work. As the invited dinner speaker, (TIMS); and the Software Psychology Robert Howard, noted author on the Society.