LAUSR

P H O T O C O U R T E S Y O F C A R N E G I E M E L L O N U N I V E R S I T Y E D MUN D ME LS ON CLARKE, JR., a celebrated American academic who developed methods for mathematically proving the correctness of computer systems, died on December 22, 2020 at the age of 75 from complications of COVID-19. Clarke was awarded the A.M Turing Award in 2008 with his former student E. Allen Emerson and the French computer scientist Joseph Sifakis, for their work on model checking. “I’ve never liked to fly, although I’ve done my share of it. I wanted to do something that would make systems like airplanes safer,” Clarke said in a 2014 video produced by the Franklin Institute when he was awarded their 2014 Bower Award and Prize for Achievement in Science “For his leading role in the conception and development of techniques for automatically verifying the correctness of a broad array of computer systems, including those found in transportation, communications, and medicine.” Model checking is a practical approach for machine verification of mathematical models of hardware, software, communications protocols, and other complex computing systems. The technique is used to formally validate all of the states that a system can possibly reach, even when the number of states seems impossibly large—for example, more than the number of stars in the universe. These techniques, first developed when he was an assistant professor at Harvard University in 1981, are now widely used in the design of computing hardware and safety-critical systems and are increasingly being used for protocol validation and computer security. Clarke grew up in rural Virginia and was the first person in his family to graduate from college. He earned a bachelor’s degree in mathematics in 1967 at the University of Virginia, a master’s degree in mathematics the following year at Duke University, and a Ph.D.