We implement and study a computational model of Stevens' [19921 theory of the pathogenesis of schizophrenia. This theory hypothesizes thatthe onset of schizophrenia is associated with reactive synaptic regeneration occurring in brain regions receiving degenerating temporallobe projections. Concentrating on one such area, the frontal cortex, we model a frontal module as an associative memory neural network whose input synapses represent incoming temporal projections. We analyze how, in the face of weakened external input projections, compensatory strengthening of internal synaptic connections and increased noise levels can maintain memory capacities(which are generally preserved in schizophrenia). However, These compensatory changes adversely lead to spontaneous, biasedretrieval of stored memories, which corresponds to the occurrence of schizophrenic delusions and hallucinations without anyapparent external trigger, and for their tendency to concentrate onjust few central themes. Our results explain why these symptoms tend to wane as schizophrenia progresses, and why delayed therapeuticalintervention leads to a much slower response.

Understanding the response of neural nets to structural/functional damage is important fora variety of reasons, e.g., in assessing the performance of neural network hardware, and in gaining understanding of the mechanisms underlying neurological andpsychiatric disorders. Recently, there has been a growing interest in constructing neuralmodels to study how specific pathological neuroanatomical and neurophysiological changes can result in various clinical manifestations, and to investigate thefunctional organization of the symptoms that result from specific brain pathologies (reviewed in [1, 2]). In the area of associative memory models specifically, earlystudies found an increase in memory impairment with increasing lesion severity (in accordance with Lashley's classical'mass action' principle), and showed that slowly developing lesions have less pronounced effects than equivalent acute lesions [3]. Recently, it was shown that the gradual pattern of clinical deterioration manifested in the majority of Alzheimer's patients can be accounted for, and that different synaptic compensation rates can account for the observed variation in the severity and progression rate of this disease [4]. However, this past work is limited in that model elements have no spatial relationships to one another (all elements are conceptually equidistant).

Daewoo Shipbuilding Company, one of the largest shipbuilders in the world, has experienced great deal of trouble with the planning and scheduling of its production process. To solve the problems, from 1991 to 1993, Korea Advanced Institute of Science and Technology (KAIST) and Daewoo jointly conducted the Daewoo Shipbuilding Scheduling (das) Project. To integrate the scheduling expert systems for shipbuilding, we used a hierarchical scheduling architecture. To automate the dynamic spatial layout of objects in various areas of the shipyard, we developed spatial scheduling expert systems. For reliable estimation of person-hour requirements, we implemented the neural network-based person-hour estimator. In addition, we developed the paneled-block assembly shop scheduler and the long-range production planner. For this large-scale project, we devised a phased development strategy consisting of three phases: (1) vision revelation, (2) data-dependent realization, and (3) prospective enhancement. The DAS systems were successfully launched in January 1994 and are actively being used as indispensable systems in the shipyard, resulting in significant improvement in productivity and visible and positive effects in many areas.

Randy Davis announced the appointment of six new program managers at ARPA. At IJCAI-95, Randall Davis assumed the office of president of the American For many attending the Fourteenth for consideration this year," noted Association for Artificial Intelligence International Joint Conference on Ray Perrault of SRI International, (AAAI). Davis is a professor of Artificial Intelligence (IJCAI-95), the chair of the conference. "This is more electrical engineering and computer most difficult problem was choosing than at IJCAI-93 and at recent science and associate director of the which session to attend in the rich, National Conferences on AI in the AI Lab at the Massachusetts Institute varied program. Davis succeeds data-mining application from rate was under 25 percent, showing Barbara Grosz, Gordon McKay professor the U.S. Department of the Treasury that there is a great deal of work of computer science in the Division that identifies potential money laundering going on, and the scientific standard of Applied Sciences at Harvard to a small mobile LEG0 robot of IJCAI matches or exceeds that of University.

Daewoo Heavy Industries, in conjunction with the Korean Advanced Institute of Science and Technology, integrated applicability and limitations of various five separate schedulers based on different several papers from the AI techniques. IAAI has been held annually that are addressed at the conference. Mita Industrial Co., Ltd., said Japan's troubleshooting expert system proceedings were published in book Seventeen applications represent this has been supplied as an embedded form through 1992. Since 1993, a year's award winners: 11 were from component of its photocopiers conference proceedings volume has the United States, 4 from the Pacific since April 1994. It uses new reasoning been published, and selected papers Rim, 1 from Europe, and 1 from the methods based on virtual cases have been republished as articles in Middle East.

This paper presents an approach to learning from situated, interactive tutorial instruction within an ongoing agent. Tutorial instruction is a flexible (and thus powerful) paradigm for teaching tasks because it allows an instructor to communicate whatever types of knowledge an agent might need in whatever situations might arise. To support this flexibility, however, the agent must be able to learn multiple kinds of knowledge from a broad range of instructional interactions. Our approach, called situated explanation, achieves such learning through a combination of analytic and inductive techniques. It combines a form of explanation-based learning that is situated for each instruction with a full suite of contextually guided responses to incomplete explanations. The approach is implemented in an agent called Instructo-Soar that learns hierarchies of new tasks and other domain knowledge from interactive natural language instructions. Instructo-Soar meets three key requirements of flexible instructability that distinguish it from previous systems: (1) it can take known or unknown commands at any instruction point; (2) it can handle instructions that apply to either its current situation or to a hypothetical situation specified in language (as in, for instance, conditional instructions); and (3) it can learn, from instructions, each class of knowledge it uses to perform tasks.

This paper studies the problem of ergodicity of transition probability matrices in Markovian models, such as hidden Markov models (HMMs), and how it makes very difficult the task of learning to represent long-term context for sequential data. This phenomenon hurts the forward propagation of long-term context information, as well as learning a hidden state representation to represent long-term context, which depends on propagating credit information backwards in time. Using results from Markov chain theory, we show that this problem of diffusion of context and credit is reduced when the transition probabilities approach 0 or 1, i.e., the transition probability matrices are sparse and the model essentially deterministic. The results found in this paper apply to learning approaches based on continuous optimization, such as gradient descent and the Baum-Welch algorithm.

This book review examines Artificial Intelligence: A Modern Approach, by Stuart Russell and Peter Norvig, Prentice Hall, Englewood Cliffs, New Jersey, 1995, 932 pp., $62.90, ISBN 0-13-103805-2.

Prizes were awarded to students to encourage improved research. Michel Wermelinger, Universidade Nova de Lisboa, Portugal, was the winner of the best paper award for his work "Basic Conceptual Structure Theory," which provided a significant In "Representations Technology, Bangkok, Thailand, won Papers were presented by a number interest in the use of conceptual he Second International Conference (ICCS'94) was held at the of individuals and groups from graphs. The funds were made available University of Maryland, College several countries on the development through a grant from the American Park, Maryland, on August 16 to 20. and use of the conceptual Association for Artificial Intelligence The conference marked the tenth graph representational language. Sponsors included the University of Graph Workbench," chaired by Gerard vice-president of academic affairs, Paradigm Development Corp. in Urbana, Illinois, was the second She received her Ph.D. from the introduction, "Aristotelian and

The first session aimed to set the component being tested. The stage for the day's discussion by focusing variation in all three of these contexts on the issues surrounding the will lead to different types of and Verification of Knowledge-use of formal specification techniques The first paper, by Formal Specifications to Design Intelligence (AAAI-94) in Seattle, Lance Miller of SAIC, was entitled Verifiable Hybrid KBS" by Rose Gamble, Washington, marked the seventh This paper provided a with its specification, and (2) the The 1994 workshop was significant basis for the comparison of validation refinement of formal specifications in that there was a definitive move in and verification techniques to for their implementation. O'Leary, from the lows the possibility of constraining techniques for validating certain University of Southern California, the experts' choices to ensure that properties of KBSs. A paper by presented a paper on the relationship any new knowledge added is valid Alun Preece, Cliff Gossner, and T. between errors and size in KBSs. This and that the knowledge base structure Radhakrishnan (all from the University paper is among the first to address ensures the knowledge is of Aberdeen, Scotland) considered this important issue.