Barbara Liskov

Barbara Liskov (born Barbara Jane Huberman on November 7, 1939) is an American computer scientist known for foundational work in programming languages and distributed computing. She introduced abstract data types and the principle of data abstraction, and formulated the Liskov substitution principle, which applies these ideas to object-oriented programming, subtyping, and inheritance. In 2008, she received the Turing Award, the highest honor in computer science. Liskov was one of the earliest women in the United States to earn a Ph.D. in computer science and the second woman to receive the Turing Award. She currently holds the titles of Institute Professor and Ford Professor of Engineering at the Massachusetts Institute of Technology.

Born in Los Angeles, California, Liskov was the eldest of four children. She earned a bachelor’s degree in mathematics with a minor in physics from the University of California, Berkeley in 1961, where she was one of only two women in her major. After being rejected from Princeton’s mathematics graduate program because it did not admit women, she worked at the MITRE Corporation, where she became interested in computers. She later worked at Harvard on language translation before returning to graduate school. In March 1968, she earned a Ph.D. from Stanford University’s computer science department, one of the first women in the U.S. to do so. At Stanford, she worked with John McCarthy on artificial intelligence, and her thesis developed a chess endgame program that introduced the killer heuristic.

After Stanford, Liskov returned to MITRE as a research staff member. She led major projects including the Venus operating system, the CLU programming language, Argus (the first high-level language for distributed programs, demonstrating promise pipelining), and Thor, an object-oriented database system. With Jeannette Wing, she defined the Liskov substitution principle. She leads MIT’s Programming Methodology Group, focusing on Byzantine fault tolerance and distributed computing. Her work on CLU and Argus influenced languages such as Java, C++, C#, and Ada. The Liskov substitution principle became a foundational concept in software engineering education, taught as a formal criterion for subtype correctness in object-oriented design.

Liskov is a member of the National Academy of Engineering, the National Academy of Sciences, and a fellow of the American Academy of Arts and Sciences and the Association for Computing Machinery. In 2002, she was named one of the top women faculty at MIT and among the top 50 U.S. science faculty; that year, *Discover* magazine listed her among the 50 most important women in science. She received the John von Neumann Medal in 2004, honorary doctorates from ETH Zurich (2005, with Donald Knuth), the University of Lugano (2011), and Universidad Politécnica de Madrid (2018). The ACM awarded her the 2008 Turing Award for contributions to programming language and system design, especially data abstraction, fault tolerance, and distributed computing. She was inducted into the National Inventors Hall of Fame in 2012 and received the Benjamin Franklin Medal from the Franklin Institute in 2023.

As of February 2023, Liskov has authored five books and over one hundred technical papers. Her books include *CLU: Reference Manual* (1981), *Distributed Systems: Methods and Tools for Specification* (1985), *Abstraction and Specification in Program Development* (1986, with John Guttag), and *Program Development in Java: Abstraction, Specification, and Object-Oriented Design* (2000).