School of Information Sciences, University of Pittsburgh, 135 North Belle¢eld Ave., Pittsburgh, PA 15260, U.S.A., E-mail: firstname.lastname@example.org Abstract. Adaptive hypermedia is a relatively new direction of research on thecrossroads of hypermedia and user modeling. Adaptive hypermedia systems build a model of the goals, preferences and knowledge of each individual user, and use this model throughout the interaction with the user, in order to adapt to the needs of that user. The goal of this paper is to present the state of the art in adaptive hypermedia at the eve of the year 2000, and to highlight some prospects forthe future. This paper attempts to serve both the newcomers and the experts in the area of adaptive hypermedia by building on an earlier comprehensive review (Brusilovsky, 1996; Brusilovsky, 1998). Key words: hypertext, hypermedia, user model, user pro¢le, adaptive presentation, adaptive navigation support,Web-based systems, adaptation
Adaptive hypermedia is a relatively newdirection of research on the crossroads of hypermedia and user modeling. One limitation of traditional ``static'' hypermedia applications is that they provide the same page content and the same set of links to all users. If the user population is relatively diverse, a traditional system will suffer from an inability to be ``all things to all people''. For example, a traditional educational hypermediasystem will present the same static explanation and suggest the same next page to students with widely differing educational goals and knowledge of the subject. Similarly, a static electronic encyclopedia will present the same information and same set of links to related articles to readers with different knowledge and interests. A Web bookstore might also offer the same selection of``bestsellers'' to customers with different reading preferences. Finally, a static virtual museum will offer the same ``guided tour'' and the same narration to visitors with very different goals and background knowledge. Adaptive hypermedia is an alternative to the traditional ``one-size-¢ts-all'' approach in the development of hypermedia systems. Adaptive hypermedia systems build a model of the goals,preferences and knowledge of each individual user, and use this model throughout the interaction with the user, in order to adapt to the needs of that user. For example, a student in an adaptive educational hypermedia system will be given a presentation that is adapted speci¢cally to his or her knowledge of the subject (De Bra and Calvi, 1998), and a suggested set of most relevant links to proceedfurther (Brusilovsky et al. 1998a). An adaptive
electronic encyclopedia will personalize the content of an article to augment the user's existing knowledge and interests (Milosavljevic, 1997). A virtual museum will adapt the presentation of every visited object to the user's individual path through the museum (Oberlander et al., 1998). These are just a few recent examplesof the use of adaptive hypermedia.
2. Adaptive Hypermedia Research Before and After 1996
Adaptive Hypermedia research can be traced back to the early 1990s. At that time, the two main parent areas ^ Hypertext and User Modeling ^ had achieved a level of maturity that allowed for the cross-fertilization of research ideas. A number of research teams had recognized the problems of static hypertextin different application areas, and had begun to explore various ways to adapt the output and behavior of hypertext systems to individual users (Bocker et al. 1990; Brusilovsky « et al. 1993; de La Passardiere and Dufresne, 1992; Fischer et al., 1990; Kaplan et al. 1993). The ¢rst research efforts were independent and the early researchers were generally not aware about each other's work. The...