E. Allen Emerson was the first graduate student of Edmund M. Clarke at Harvard University. After discussing several ideas for Allen's dissertation, they identified a promising candidate: verifying a finite-state system against a formal specification. According to Martha Clarke, Edmund's widow, it was during a walk across Harvard Yard that they decided to call it "model checking." Emerson received his Ph.D. in applied mathematics for this work in 1981. Twenty-five years later, he and Clarke (along with Joseph Sifakis) shared the ACM A.M. Turing Award in 2007 for this and related work.

Generations of computing professionals may remember Frederick P. Brooks, Jr., as the author of the seminal text on system engineering, The Mythical Man-Month: Essays on Software Engineeringa and his essays such as No Silver Bullet--Essence and Accident in Software Engineering.b Those who worked with Brooks, winner of the 1999 ACM A.M. Turing Award "for landmark contributions to computer architecture, operating systems, and software engineering," may also remember him as the lead designer of IBM's System/360, as an innovator in graphics and virtual reality, and as the founder of the University of North Carolina's computer science department. Brooks was born on April 19, 1931, in Greenville, North Carolina. He received his A.B. in Physics from Duke University in 1953. As a freshman, he saw an article in the January 23, 1950 issue of Time Magazine entitled "The Thinking Machine" that sparked his interest in computing.

In January 2015, Stephen Hawking, Elon Musk, and dozens of artificial intelligence experts signed an open letter on artificial intelligence calling for research on the societal impacts of AI. The letter affirmed that society can reap great potential benefits from artificial intelligence, but called for concrete research on how to prevent certain potential "pitfalls": artificial intelligence has the potential to eradicate disease and poverty, but researchers must not create something which cannot be controlled. The four-paragraph letter, titled "Research Priorities for Robust and Beneficial Artificial Intelligence: An Open Letter", lays out detailed research priorities in an accompanying twelve-page document.

He married Patricia Enderson in 1950, and they raised five children. He received his Ph.D. in psychology in 1954 from the University of Southern California. His dissertation was entitled "The Prediction of Accident Rates from Basic Design Features of USAF Aircraft." His first job after graduation was with Douglas Aircraft Corporation in Santa Monica, California, where he developed computerized methods for statistical forecasting of labor costs for building newly designed airplanes. He began work in 1955 at RAND Corporation and continued in 1957 at its offshoot, the System Development Corporation (SDC), also in Santa Monica, where he was head of the Language Processing Research Program until 1968.

Raymond Reiter, a professor of computer science at the University of Toronto, a fellow of the Royal Society of Canada, and winner of the International Joint Conference on Artificial Intelligence 1993 Outstanding Research Scientist Award, died September 16, 2002, after a yearlong struggle with cancer. Reiter, known throughout the world as "Ray," made foundational contributions to artificial intelligence, knowledge representation and databases, and theorem proving. Reiter, known throughout the world as "Ray," made foundational contributions to artificial intelligence, knowledge representation and databases, and theorem proving. Ray was born in Toronto, Canada, in 1939 to immigrant parents who came from Poland. He received a B.S. in mathematics from the University of Toronto in 1961 and an M.S. degree in mathematics in 1963 from the University of Toronto.

The fall of 2002 marked the passing of Ray Reiter, for whom a memorial article by Jack Minker appears in this issue. As the issue was going to press, AI lost Saul Amarel, Norm Nielsen, and Charles Rosen. We thank Tom Mitchell and Casimir Kulikowski for their memorial to Saul Amarel, Ray Perrault for his remembrance of Norm Nielsen, and Peter Hart and Nils Nilsson for their tribute to Charles Rosen. The AI community mourns our lost colleagues and gratefully remembers their contributions, which meant so much to so many and to the advancement of artificial intelligence as a whole. The foundation of Charlie's creativity was his broad knowledge.

Arthur Samuel (1901-1990) was a pioneer of artificial intelligence research. From 1949 through the late 1960s, he did the best work in making computers learn from their experience. His vehicle for this work was the game of checkers. Programs for playing games often fill the role in artificial intelligence research that the fruit fly Drosophila plays in genetics. Drosophilae are convenient for genetics because they breed fast and are cheap to keep, and games are convenient for artificial intelligence because it is easy to compare a computer's performance on games with that of a person.

Daniel G. Bobrow (1935-2017) was a research fellow at Xerox's Palo Alto Bobrow was born in 1935 in New York City. AAI Fellow and AAAI past-president Daniel G. attended the Bronx School of Science along with Danny completed his Ph.D. dissertation in 1964 at the The thesis described STUDENT, a revolutionary program that could solve algebra word problems stated in English as found in highschool algebra textbooks. Danny's was one the first theses on natural language understanding -- a topic that would remain a central interest of his throughout his long career. He also was one of the first students at what would later become the MIT AI Lab. The technical report describing his thesis was the first in a series of illustrious research results: Project MAC technical report: MAC-TR-1.

John Gaschnig was best known lately for his work on expert systems, notably the PROSPECTOR geological exploration system developed at SRI Internation.

Push Singh, one of em IEEE Intelligent Systems /em "AI Ten to Watch" recipients this year, died 28 February 2006. He was slated to begin a position as a faculty member in the MIT Media Laboratory. His PhD advisor, Marvin Minsky, was one of many people who will miss him and his work, which was based partly on Marvin's society-of-minds approach, exploring what common sense was and how it could develop. This article is part of a special issue on the Future of AI.