Wednesday, April 10, 2002

Nebraska Researchers Measure the Extent of 'Link Rot' in Distance Education By VINCENT KIERNAN Anyone who has surfed the Web knows the frustration caused by hyperlinks to Web pages that have moved or ceased to exist. For apparently the first time, two researchers at the University of Nebraska at Lincoln have measured the impact of this "link rot" on online education -- and it's not pretty. Nineteen percent of the 515 hyperlinks contained in online materials for three graduate-level biochemistry courses at the university expired sometime between August 2000, when the course materials were created, and last month, the researchers found. "The progressive disappearance of materials presents a major problem for courses developed to utilize these resources extensively," say the scholars, John Markwell and David W. Brooks, in an article to be published in June's issue of the Journal of Science Education and Technology. Mr. Markwell is a professor of biochemistry at the university, and Mr. Brooks is a professor in its Center for Curriculum and Instruction. A summary of their research is also available online. The two researchers found that the rate of link rot is similar to that of the decay of radioactive substances. The links in the three courses had a half-life of 55 months: Half of the links would be expected to have died in 55 months, half of the remaining links would be expected to have died in another 55 months, and so forth. Both researchers were traveling Tuesday and could not be reached for comment; Mr. Markwell is scheduled to present the results of the study today at a meeting of the Society for Experimental Biology, in Wales. Kent J. Crippen, an assistant professor of educational computing and technology at the University of Nevada at Las Vegas, said he believes that the study is the first to measure the extent of link rot. The study's results are not merely of theoretical interest for distance educators, said Mr. Crippen, who also is an assistant editor at the Journal of Science Education and Technology. The results illustrate the extent of a practical problem with offering courses online. Because of link rot, someone must periodically check an online course's links and remove or update any that have expired, he said. Academic departments often do not budget for such maintenance costs or consider in tenure-and-promotion evaluations how much time such maintenance takes, he said. "People think about start-up costs, but they never think about maintenance costs." Link rot is particularly problematic for a course that is offered repeatedly, said Daniel Cane, senior vice president of research and development at Blackboard Inc., which produces software used for offering online courses. The company recently started offering its users a program that checks all the links on a Blackboard-based online course and can hide any that no longer work. "We do see it as a growing issue," Mr. Cane said of link rot. To avoid link rot, Mr. Markwell and Mr. Brooks wrote in their paper, instructors should consider making their own online copies of materials used in their courses that are posted elsewhere on the Web -- with the permission of the creators of those materials -- and linking to the copies rather than the originals. Scholarly societies also could consider compiling archives of the best online material for educational use, the two scholars wrote. Easy-to-print version E-mail this article

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