NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the steering committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

Support for this project was provided by the Defense Advanced Research Projects Agency (Grant No. N00014-87-J-1110), the National Science Foundation (Grant No. CDA-9121558), and the Association for Computing Machinery, the Computer and Business Equipment Manufacturers Association, the Information Technology Association of America, and the Institute of Electrical and Electronics Engineers (under unnumbered contracts).

Library of Congress Catalog Card Number 92-85596

B-030