Editor's Note: The World Wide Web went live 20 years ago this month, on a single computer in Geneva, Switzerland. For the anniversary, the Web's inventor, Tim Berners-Lee, has written an exclusive article for Scientific American. In it, he confronts various threats that could ruin the Web, and explains why preserving the basic principles that have allowed the Web to flourish is essential to preventing its destruction.

While preparing the article, Berners-Lee also spoke to
Scientific American about emerging Web capabilities that could change how the online and physical worlds work. This four-part series covers some of the most intriguing, including the power of linked data, social machines, free bandwidth to the masses and Web science.

Indeed, the Web is thriving—a recent cover story in
Wired magazine to the contrary notwithstanding. Scientific American editor Mark Fischetti tackles the differences between the two magazine's treatments in his blog, "The Web is (Not) Dead."

Putting raw data on the Web and linking it to other data is bringing powerful new research and analysis capabilities to Web users—capabilities that far exceed what's created by the hyper-linked documents we are all familiar with. "Twenty years ago I had to encourage people to put their documents on the Web and make links to other documents," says Tim Berners-Lee, who invented the Web, which went live in December 1990. "We have to now do it again, with linked data."

Examples of the power of linked data arise daily. In Britain, The Times picked up raw, linked data about bicycle accidents from DirectGov and published a mashup map showing where bicycle accidents had occurred, so cyclists could be aware of the many dangerous spots along the city's roads.

In Zanesville, Ohio, a civil rights attorney for a nonprofit group created a mashup map showing which houses were connected to town water lines and which houses were occupied by black or white families, according to census data. It revealed that the local utility was discriminating against blacks, and a judge imposed damages.

The U.S. and U.K. governments have promised to post all sorts of data online—on www.data.gov and www.data.gov.uk. "I'd like to see a kind of competition develop—who can put up more data publicly," says Berners-Lee, a chief consultant to Britain's effort. "In the U.K., you can drill down to see how the government is spending your money, in great detail. Putting non-personal data on the Web helps make the government more transparent and can also make operations run more efficiently." Similarly, by opening such data, scientists and journalists could report on original climate change figures, unfiltered by pundits who have preconceived opinions.

Individuals everywhere are contributing tiny bits of information to OpenStreetMap.org, a free world map that anyone can add to or edit, building up geographical data in a collaborative way. At the end of 2009, the OpenStreetMap of Port-au-Prince, Haiti, showed very few specifics about the city. But just after the massive earthquake hit in January 2010, a company called GeoEye released satellite imagery of Haiti, with a license that allowed people to use it.

Immediately, individuals from all over the world who wanted to help Haiti scrutinized the imagery—zoomed in and peered into it—and added to the OpenStreetMap all sorts of details about the devastated area. The online map had an immediate impact on rescue efforts, as teams accessed the information via portable navigation devices, as Berners-Lee pointed out about four minutes into the presentation below from a 2010 Technology, Entertainment, Design (TED) conference.

"They marked which roads were blocked, which buildings were damaged," Berners-Lee said with excitement. They plotted where the refugee camps were growing. They tracked when incoming medical ships were reaching ports and docks. "The site rapidly became the map to use on the ground if you were doing relief work," he adds.

Linked data can also keep corporations honest. It could, for example, indicate details about a company's carbon footprint. Some retail corporations are reportedly considering whether to require companies in their supply chain to post such data. Consumers could then look up carbon emissions, energy use and water use in the chain. A new company called SourceMap.org is accumulating similar information for a growing number of consumer products.

Several sites have arisen specifically to help people post and link data. Linked Data offers tools to make the task easy and presents sites that are heavily data driven. The Linked Open Data project provides tutorials and forums for people seeking to link data with others who have similar interests.

For more from Berners-Lee on the promise of linked data, see "Long Live the Web."