Tim Berners-Lee must feel like he's in a time warp. In the early 1990s, he spent a frustrating year trying to get people to grasp the power and beauty of his idea for a scheme known as an Internet hypertext system, to which he gave the beguiling name the World Wide Web. But since the Web didn't yet exist, most people couldn't imagine the implications of what he was talking about. Berners-Lee persevered, and with the help of the few people who shared his vision, his invention became the fastest-growing media distribution system in history.

A decade later, Berners-Lee is struggling with the same problem-only this time, he's trying to articulate his dream of a Semantic Web. The idea is to weave a Web that not only links documents to each other but also recognizes the meaning of the information in those documents-a task that people can ordinarily do quite well but is a tall order for computers, which can't tell if "head" means the leader of an organization or the thing on top of a body. "The Semantic Web is really data that is processable by machine," says Berners-Lee, who is director of the MIT-based World Wide Web Consortium. "That's what the fuss is about."