Do the Time Warp

Researchers at Los Alamos National Laboratory have made a fundamental breakthrough in time travel—on the Internet, that is—by building a bridge to the World Wide Web as it existed in the past.

Herbert Van de Sompel and his team of computer and information scientists at the Los Alamos Research Library and Old Dominion University have written a new technical specification that embeds the concept of time within the global explosion of information that we call the Web. The new specification is part of the team's recently proposed information framework, dubbed Memento, which endows the Web with a built-in mechanism for version control of Web pages, databases, and other digital resources. In practice, Memento turns the Web into an online playground for would-be time travelers.

Hitching a time ride with Memento is easy, thanks to a new plug-in that the team has developed. When installed in a Web browser, the Memento plug-in provides a drop-down calendar for selecting a time destination. Want to relive the excitement of the 2004 World Series? Turn the Memento calendar back to October 27, 2004, click on a link to The Boston Globe, and away you go. After transporting you to an archived version of a Web page, Memento maintains the illusion of the past: hyperlinks embedded within the destination page send you to archived Web pages from the same time period.

Before this seemingly simple idea could be implemented, the Memento developers had to teach the Web how to keep track of time. As it turns out, the Web has a bad case of amnesia. When a Web page is updated with new information, the updated version typically inherits the address of its previous incarnation. This is a sensible idea, one that avoids breaking all the existing links to the page from the Web at large. But the cost of this stability is memory loss—older versions are too often left unlinked, abandoned on Web servers to the forces of bit rot and digital obsolescence.

""Memento solves this problem by adopting the notion of time as a version indicator and inserting it into the process of content negotiation, the behind-the-scenes digital exchange that takes place between a browser requesting a Web page and the server on which the page resides. This approach allows the version of the page returned to the browser to be matched as closely as possible to the user's time preference. The processes underlying the Memento framework are executed using HTTP primitives, the basic elements of the standard Web protocol. While the scope of other versioning approaches is limited by their use of proprietary syntax, Memento speaks a global language that opens the entire Web to version control.

Time travel with Memento works only when someone has had the foresight to archive a requested Web page. Pockets of memory exist throughout the Web, for example, in the version histories maintained by Wikipedia and the snapshots of the Web kept as cultural records by preservation groups such as the Internet Archive and the Library of Congress. Memento provides a direct path between a current Web page and earlier versions stored in these repositories, thus eliminating the detective work of clicking through a cascade of links to find archived information.

Tim Berners-Lee, who invented the Web in the early 1990s, and other Web luminaries have taken notice of Memento and offered encouragement. And the archivists love it. The Library of Congress provided the initial seed funding for Memento and has contributed an additional $1 million for further research, development, and outreach. Memento team member Robert Sanderson recently met with the General Assembly of the International Internet Preservation Consortium in Singapore, where he received commitments to implement Memento from the national Web archives of several countries. The entire team recently beat out stiff international competition to win the 2010 Digital Preservation Award.

Van de Sompel believes that Memento has the potential to profoundly alter the way we perceive and interact with the Web. "By increasing awareness of the Web of the past, Memento will help expand our collective digital memory," he says. It can also be a lot of fun. See for yourself by downloading the free Memento plug-in for the Mozilla Firefox browser at An application for Android phones is available through the same site, and an iPhone application is on the way.

—Craig Carmer


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