CS community mourns death of Kanellakis

By Members of the Brown University Department of Computer Science.

Paris Kanellakis, his wife, Maria Teresa Otoya, and their two children, Alexandra and Stefanos, died Dec. 20, 1995, in the American Airlines crash outside Cali, Columbia. Paris's tragic death has created a void both at Brown University and in computer science as a whole.

Paris was born in Athens, Greece; he received his undergraduate education at the National Technical University of Athens, where he was first in his class. He then went to the Massachusetts Institute of Technology, where he received his master's and Ph.D. degrees and came to Brown as an assistant professor in 1981. He became a US citizen in 1988 and a full professor here in 1990.

Paris's research area was theoretical computer science. His contributions were unique both in the breadth of his interests and in his ability to carve out research programs in which his keen mathematical insight could be put to the service of practical issues.

Broadly put, Paris was interested in how the formal language in which a problem is expressed affects the class of problems one can use it to attack. Most of us who have written programs feel intuitively that some problems are easier to express in one language than another. Paris worked at a more fundamental level: The languages he explored were deliberately kept simple, to make mathematical analysis possible. And the choice of language could decide not just ease of expression but whether or not a problem could be expressed at all.

Furthermore, he recognized that the more expressive a language, the wider the class of problems it can solve. It also follows that more expressive languages are less likely to admit efficiency--some of the programs expressed cannot be solved efficiently. Because this trade-off is inevitable, one is always searching for languages that best balance these concerns.

Within this broad area, Paris attacked a variety of issues. For example, computer databases require a language in which to express one's query. More recently the area of constraint programming languages attracted his attention. In a constraint language one says not merely that a particular variable is always an integer but that, say, it is an integer between certain values. Concerning efficiency, some of Paris' most important papers showed that language features previously thought unexceptionable--unification and type checking, to cite what are probably among his most important results--in fact contain pitfalls that require careful negotiation.

Also, because in many cases one is interested in efficiency when using not just a single computer but rather a large collection of computers, Paris made fundamental contributions to the area of parallel processing. In all these cases Paris worked closely with practitioners in the area here at Brown and elsewhere to ensure that his work was grounded in reality. For this and related work, Paris was viewed as a leader in theoretical computer science, particularly among those with a taste for practice.

Paris was not only an intellectual leader in his field but a professional leader as well, through his willingness to organize conferences, mentor students and generally work for the betterment of his intellectual community. Paris put his great energy and commitment at the service of our department and the university as well. He assumed many tasks for the department and performed them with skill, devotion and good spirits. But occasionally this caused small problems. For many years, our department has operated in two time zones: regular time and Kanellakis time, which uniformly ran about 12 minutes behind.

Paris had great insight into human nature and was fiercely honest. He was one of the people always consulted on tricky departmental issues because we respected his opinions and valued his insights. He also had a fine sense of humor, a wonderfully wholehearted laugh and an outgoing, energy-filled personality that drew everyone to him. He turned 42 just two weeks before his death. His accomplishments were immense even in the time he had, and we grieve for the loss of what he would have accomplished had he had more.