Web-Users Beware: That Link May be Rotten

"LINK ROT" HAMPERS WEB'S USEFULNESS IN EDUCATION

The use of Internet resources in college classes has blossomed in the last several years. But as the practice has grown, so too has an accompanying problem known colloquially as link rot.

Link rot is the decay of World Wide Web links as the sites they connect to change or disappear. It's a problem educators have been aware of for some time, but no one really knew its extent until two exasperated University of Nebraska-Lincoln professors started tracking it.

John Markwell, professor of biochemistry in the Institute of Agriculture and Natural Resources, and David Brooks, professor of chemistry education in Teachers College, had spent the summer of 2000 putting together three one-credit, graduate-level biochemistry courses for distance delivery to high school science teachers. But even before they had finished preparing the courses, they saw that some of their Web links had disappeared, or rotted.

"It was very frustrating," Markwell said. "I talked to some of my colleagues about this and they all seemed to concur that, yes, there is this difficulty. But nobody had anything other than anecdotal information and we couldn't find any hard evidence to document it. So we decided we would start to follow it with these three courses and try to quantify it."

Beginning in November 2000, Brooks and Markwell made systematic mid-month checks of the 515 nonredundant Web sites used in the courses, making their checks during the workweek to avoid weekends when periods of server down-time are commonly scheduled. What they found surprised them.

By mid-September 2001, nearly one in six (16.5 percent) of the links that had been viable 13 months earlier had disappeared or were nonviable because the content had changed, sometimes drastically. Moreover, they found that the links rotted at a steady month-to-month rate.

"We expected we would have a slight die-off and we anticipated that maybe we would see a lot of the educational links disappear at the end of the academic year in May or June, only to reappear in the fall when school started again," Markwell said. "But much to our surprise, there has been a steady, progressive decrease in the accessibility of the hyperlinks."

In a paper to be published in the June issue of the Journal of Science Education and Technology, Brooks and Markwell likened the rate of link rot to the type of "extinction equation" commonly used to describe natural processes such as radioactive decay. They wrote that the hyperlinks in their study had an expected "half-life" of 55 months. In other words, one-half of the original 515 links would no longer be viable after 55 months, half of the remaining links would no longer be viable after another 55 months, and so on.

Educational (.edu) links were the most unstable, with 17.5 percent of links lost in 13 months, followed by commercial (.com) links at 16.5 percent and nonprofit organization (.org) links at 11.6 percent. The most-stable links were to government (.gov) Web sites, where just two of 53 links (4 percent) were lost in 13 months. Markwell said that wasn't surprising because most of the links were to well-maintained sites at federal agencies, including the National Science Foundation, which supported the study through a grant.

"Three years ago, I was a big proponent of putting hyperlinks into the class notes that I put on line for students, but I've stopped using them as much," Markwell said. "I tend now to only pick the ones that look to me like they will be most stable."

The two scholars said a solution to the problem would be for professional academic societies to act as hosts for the best Internet resources.

"A professional society interested in education could play a valuable role by actively reviewing and archiving (mirroring) the best and most relevant educational materials developed by its members," Brooks and Markwell wrote. "Such peer-reviewed hosting could prove useful to educators by providing documentation of authentic scholarship in science education."

Brooks and Markwell continue to track link rot at the sites for the three courses and updated data can be found on the Web (http://www-class.unl.edu/biochem/url/broken_links.html).Markwell said he guarantees that the link will be there.

Contact: John Markwell, Professor, Biochemistry -- (402) 472-2924 ([email protected]); Kelly Bartling, University Communications ? (402) 472-2059

(News release Web site: http://www.unl.edu/pr/releases.html)

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