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.

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.

The first step in the development of an expert system is the extraction and characterization of the knowledge and skills of an expert. This step is widely regarded as the major bottleneck in the system development process. To assist knowledge engineers and others who might be interested in the development of an expert system, I offer (1) a working classification of methods for extracting an expert's knowledge, (2) some ideas about the types of data that the methods yield, and (3) a set of criteria by which the methods can be compared relative to the needs of the system developer. The discussion highlights certain issues, including the contrast between the empirical approach taken by experimental psychologists and the formalism-oriented approach that is generally taken by cognitive scientists.

We note with sorrow the passing of Don Waterman, who died on January 4, 1987. Don was one of the pioneers of our field, whose early research built the foundation for the area that would later come to be labeled "knowledge based systems" (and still later "expert systems").

Letters to the Editor

Letters to the Editor

Letters to the Editor

Letters to the Editor

Jim Kornell, Robert Park, Christopher Dungan, Joop Schopman, David Drager, Nils J. Nilsson, Marty Kalin, John Gavin, Bernard Meltzer, Robert Salmansohn, Keith McCammon, Loren Martindale Abstract Subjects include AI's impact on employment, the AAAI conference, a response to McCarthy's Presidential Message, AI going public, and computerless expert systems. Subjects include AI's impact on employment, the AAAI conference, a response to McCarthy's Presidential Message, AI going public, and computerless expert systems.