For more than 40 years, Jeffrey Buzen has been a leader in performance prediction of computer systems and networks. His first major contribution was an algorithm, known now as Buzen's Algorithm, that calculated the throughput and response time of any practical network of servers in a few seconds. Prior algorithms were useless because they would have taken months or years for the same calculations. Buzen's breakthrough opened a new industry of companies providing performance evaluation services, and laid scientific foundations for designing systems that meet performance objectives. Along the way, he became troubled by the fact that the real systems he was evaluating seriously violated his model's assumptions, and yet the faulty models predicted throughput to within 5 percent of the true value and response time to within 25 percent. He began puzzling over this anomaly and invented a new framework for building computer performance models, which he called operational analysis. Operational analysis produced the same formulas, but with assumptions that hold in most systems. As he continued to understand this puzzle, he formulated a more complete theory of randomness, which he calls observational stochastics, and he wrote a book Rethinking Randomness laying out his new theory. We talked with Jeff Buzen about his work.
Peter J. Denning
Editor in Chief
With all the growing interest in automated cars and driverless cars and recent accidents involving them, we thought we would turn to Risks founder Peter G. Neumann for perspective. Neumann has been moderating the ACM Risks Forum (risks.org) since 1985, and has accumulated a vast trove of experience in the ways that automated systems can not only provoke but enable mishaps. Here he offers an inventory of how automotive automation systems can fail and concludes that the greatest threats to safety come from human tendencies such as being distracted at the moment the system needs an intervention, or having their skills as operators grow rusty over time because the automation is pretty good most of the time.