For decades we've thought of computers as centralized intelligences; our model was the human brain. But lately, a growing number of researchers have been talking about a shift in the core metaphor for computing, from the notion of "artificial intelligence" to something that might be called "artificial biology." Forget about the dream of creating bug-free software. Just as bugs regularly affect any biological system-I have a cold as I write this-they should also be expected in software. So software needs to be designed to survive the bugs. It should have the biological properties of redundancy and regeneration: parts should be able to "die off" without affecting the whole.

This shift is not only transforming the research of leading academic groups at places like Stanford University, the University of California, Berkeley, and the University of Virginia but also influencing the development of commercial products: IBM and Oracle have both introduced products such as Web servers and database programs that they describe as "self-healing," a term typically applied to biological organisms. In 2001 Paul Horn, head of IBM Research, wrote a widely read white paper describing the notion of "autonomic computing" and calling on the computing research community to begin thinking of ways to design systems that could anticipate problems and heal themselves.

The point of autonomic computing-and by extension, of self-healing software-is to give networks and computer systems the ability to regulate and repair things that now require human thought and intervention. For example, servers need to be rebooted now and then to keep them working. That can happen because of "memory leaks" created by software bugs, explains Steve White, who heads up IBM's autonomic-computing research from the T. J. Watson Research Center in Hawthorne, NY. "A program will take up more and more memory to run," he says, "so eventually it breaks. Start over, and it will work." At the moment, users need to recognize problems themselves and physically reboot their systems. But with autonomic computing, "You can make it possible to reboot a system easily and automatically," says White.

In the future, the biological metaphor may even affect the way we program to begin with. Software could eventually "heal" some of its own bugs, supplementing catch-all fixes-like automatic rebooting-that don't get at the core problem. But that will require an entirely new approach to programming.