One of science fiction's best stories about robots was Jack Williamson's "With Folded Hands," later incorporated into his novel, "The Humanoids."

Williamson's robots were the ultimate nannies. They were here to protect us from harm, but pretty soon you couldn't do anything. No swimming: You might drown. No cooking: Stoves can be dangerous. A revolt against robot domination became inevitable.

It's a great story, but growing up in the 1950s, I thought that robots would be too useful to revolt against. Because they'd be programmed to serve, they would take over all the chores nobody wanted to do. Life in the future would be a matter of doing what you wanted while household robots took on all the dirty work.

Fifty years later, we've learned that building robots is trickier than once thought. The all-purpose robot has given way to specialized devices that do only a few things.

Take the Roomba, a fat disc that chugs along the floor, vacuuming and sweeping along the way. The creation of Massachusetts-based iRobot (www.irobot.com), the Roomba has been sold into more than 1.5 million homes. The surprisingly successful company completed its initial public offering in November.

Roombas aren't likely to inspire revolts against robot domination. In fact, they're sort of lovable. The eerie thing about them is that, with their built-in "intelligence," they seem to acquire personalities in the eyes of the people who own them. IRobot founder Helen Greiner says the Roomba reminds people of a pet as it finds its way around the house, using bleeps and bloops to communicate. Many users name their Roombas: Greiner's is named Arnold.

The success of the Roomba inspired iRobot to create the Scooba, which does floors using a cleaning fluid the company developed with Clorox.

It's easy to see why these products are taking off. They take a cumbersome job off your hands, they're relatively cheap (Roomba models range from $150 to $330) and they're too cute to take over the world. They're also being manufactured by a company with a vision, and part of that is making robots that people can work on themselves.

For iRobot was smart enough to build an open interface into the Roomba, which basically means that those with ideas about how to make a robot behave can tinker with the device. Out of this comes hybrid systems as hackers figure out new and exotic uses for the things, from mounting Webcams to track Roombas on the Internet, to figuring out how they can move houseplants to keep them in the sun.

We've learned from computers over the past 30 years that open systems spur innovation. Let people hack into technology to create their own solutions, and you've jump-started an industry as myriad new ideas begin to appear. The hackable robot is an educator's dream -- the kids who master it are going to build a new generation of hardware with ideas we haven't begun to imagine.

But even now, robots do far more than clean floors. IRobot's Packbot is deployed by the hundreds in Iraq and Afghanistan, detonating terrorist ordnance and tackling dangerous jobs such as land-mine clearance that would otherwise require soldiers.

Another major niche for robotics vendors will be in health care. Understaffed nursing homes could use a boost from robots that may one day dispense medication and provide basic personal care.

Numerous challenges have to be met before robots become the all-purpose devices they're pictured as in science fiction, but fascinating breakthroughs are being made. RunBot is a two-legged robot built by European researchers that models biological systems to walk more swiftly than any previous mechanical device.

And in Texas, chemistry professor Ray Baughman has created artificial muscles whose fibers can double as fuel cells for future androids. No more gears and pulleys, and no more plugging into a wall socket to recharge power-hungry batteries.

The next generation of hackable robots will make use of developing technologies such as these. R2D2 they're not, but what emerges from tomorrow's robotics labs may be far more interesting.

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