Her programming language, called CLU, had a huge influence on a new crop of language designers. It was the first to provide support for data abstraction, a technique Liskov invented that has become essential to advanced programming (see “Theory and Practice,” p. M21), and introduced several other features, such as a way for generalizing programs so they could handle iterations. Indeed, it was crucial in the development of object-oriented programming, the predominant approach in use today.
In the 1980s, Liskov got interested in supporting applications that work on the Internet. To that end, she began thinking about how a program could be split up so that parts of it run on many interconnected machines. Among other things, she figured out a new protocol that could take advantage of redundant hardware so that a distributed system could sustain damage–the inevitable failure of computers, communication links, and storage disks–without breaking down altogether. Her work helps account for why a system like Google’s search engine can keep working as people simultaneously add, modify, and delete data all over the world.
“A lot of people developed stuff that worked fine for the systems of the ’80s, but it’s no good for the systems of the 2000s,” says Guttag. “Barbara managed to develop stuff in the ’80s that’s still relevant or even more relevant today than it was then.” In fact, he says, “I think one of the reasons people can be demanding about these complex systems is that Barbara helped show the world how to build systems that work reliably.”
These days, Liskov says, she’s interested in the security of information stored online–specifically, personal information, such as medical records. As always, she’s finding ways to design systems that will encourage good programming habits. “What can you put into a platform that will make it easier for programmers to build programs that don’t inadvertently leak information?” she says.
Information can leak in many ways–so many that the problem can seem hopeless, Liskov acknowledges. Her current research focuses on protecting data in the event of the most flagrant breaches, such as cases in which users lose laptops or accidentally e-mail sensitive information to an unauthorized recipient. As policymakers and advocates debate the future of online privacy, Liskov is quietly working to ensure that the technological solutions will be there when the world wants them. “You’re talking about new technology, and you know that it takes a while for the political process to catch up,” she says.
Liskov has always encouraged and helped female students and in recent years has devoted considerable attention to making computer science a more welcoming field. As associate provost for faculty equity at MIT, she works to recruit more women and minority faculty members and to help them manage and advance their careers. Today, the Institute is a very different place from the one she encountered in the early 1970s, when there were only a handful of women on the faculty. Back then, Liskov says, she didn’t encounter much deliberate prejudice, but she did run up against ingrained assumptions. At a party at the president’s house to welcome the year’s new hires, for example, one important guest approached Liskov’s husband with his hand out, saying, “Welcome to MIT.” Students sometimes mistook her for a secretary, and she says she went through “a certain amount of testing” in classes.
Being a woman in the early days of computer science would have been difficult for someone who paid more attention to such obstacles, Liskov says. And even though those barriers didn’t much bother her, societal expectations prevented her from acknowledging the importance of her career until her own research interests began to mature.