A survey of early work exploring how AI can be used in medicine, with somewhat more technical expositions than in the complementary volume Artificial Intelligence in Medicine."Each chapter is preceded by a brief introduction that outlines our view of its contribution to the field, the reason it was selected for inclusion in this volume, an overview of its content, and a discussion of how the work evolved after the article appeared and how it relates to other chapters in the book.

JANICE S. AIKINS Dr. Aikins received her Ph.D. in computer science from Stanford University in 1980. She is currently a research computer scientist at IBM's Palo Alto Scientific Center. She specializes in designing systems with an emphasis on the explicit representation of control knowledge in expert systems. ROBERT L. BLUM Dr. Blum received his M.D. from the University of California Medical School at San Francisco in 1973. From 1973 to 1976 he did an internship and residency in the Department of Internal Medicine at the Kaiser Foundation Hospital in Oakland, California, where he was chief resident in 1976.

Edward H. Shortliffe Chapter 6 Details of the Revised Therapy Algorithm

Identifying generic, domain-independent tasks, formalizing task representation, elucidating the role of the task in eliciting domain-specific knowledge, and standardizing the design and development of expert systems then became the major research problems of the field. Knowledge specification, includes the task decomposition and the specification of the domain information types and knowledge bases. The task decomposition can be guided by selecting to reuse some of the previously identified task templates. Finally, during knowledge refinement, the models are validated through simulation on paper or with prototyping, and the knowledge bases are refined. Depending on how familiar the analyst is with the domain, these activities might have to be performed repeatedly, and subsequent activities might provide feedback for corrections or extensions to the products of earlier ones.

Editor The article "IJCAI Policy on Multiple Publication of Papers," by Alan Bundy in the Spring 1989 issue, misses one of the most important functions of IJCAI (or any other conference for that matter): The opportunity to present research to a wide audience of one's peers in person. No journal article can wholly replace the valuable give-and-take discussions that occur after a paper session. The proposed policy would deny this opportunity to researchers who have successfully published their results in a journal. Should AI researchers delay journal submissions until portions of their papers have been accepted by IJCAI or other major AI conferences? Given the vicissitudes of peer review in a methodologicallydivided field, the proposed policy seems like an excellent way to prevent dissemination of recent results Also, as much as the AI community might regard the IJCAI proceedings as an archival publication, the same thing can hardly be said of university tenure and promotion review committees, which in general prefer refereed journal articles over conference papers of whatever kind.

This issue marks the end of volume 12 and my last issue as editor in chief. In 1981 when Lee Erman (then chairman of the Publications Committee) asked me to take over the editorship of a fledgling magazine, I assumed it would be a Z-or 3-year responsibility. I never expected to still be doing it 10 years later. I also never expected it to be such a pleasurable avocation. The pleasure comes from several directions: sitting in an honored position to observe developments in AI all over the world by being the recipient of dozens of papers every year; working with an excellent supporting staff of coeditors, assistants, and production people; and receiving compliments from colleagues for doing a good job.

Design has long been an area of particular interest for AI researchers. Herbert Simon's 1968 Karl Taylor Compton lectures on the sciences of the artificial included substantial material on design. However, only recently have design researchers embraced paradigms from AI and AI researchers chosen design as a domain to study. Design research is a relatively new field, commencing in the 1960s with developments in design theories and methodologies. Although the results of the early design research produced domainindependent approaches to understanding and structuring design, the designers themselves were more comfortable with research that was specific to their own discipline.

In the lead article, Paul Cohen analyzes over 1.50 papers that were presented at the national conference last summer. Based on this analysis, he makes some interesting observations on the types of research in which we currently engage. Most research (or at least most research considered worthy of presentation by the AAAI-90 Program Committee) follows one of two strategies, according to Cohen's statistical analysis. One strategy is model oriented; that is, formal models of symbolic problem solving are hypothesized to be applicable to particular situations and then often tested on toy problems. The second strategy is system oriented; that is, it emphasizes the building of systems to solve difficult real-world problems.

During the past year we have been receiving reports of AAAIsponsored symposia and workshops faster than we can publish them. We also received two substantial bibliographies for which we did not have adequate space in any single issue. Peter Patel-Schneider and I agreed that these articles contained a great deal of useful and up-to-date information on the current state of the art in many different subdomains of AI, and should be distributed to all AAAI members. However, given the time value of these documents, we simply could not just put them in the queue for publication sometime in the dim future. Contained herein are reports from three of the 1990 Spring symposia that link AI with other disciplines: molecular biology, education, and minimallength encoding.

I am pleased to present this issue, most of which is devoted to a single subject-Spatial Reasoning. Our guest editor is Avi Kak, of Purdue University. Avi called me in the Summer of 1987, very enthused about a workshop he had recently attended. The idea of a "theme issue" on spatial reasoning sounded like a winner to me. I asked Avi to take the responsibility for selecting and editing the articles, and he agreed.