Customizing Multimedia with Multi-Trees

The majority of multimedia applications rely on hypermedia technologies, such as HTML, XML, or PHP (cf. Lang, 2005, for a review on design issues of hypermedia systems). These technologies enable the presentation of any content such as entries in a digital encyclopedia or products on a company’s homepage. In contrast to database queries, the hypermedia has to be navigated interactively. The navigation process frequently fails, and the user gets lost in hyperspace. This widespread phenomenon (Shneiderman & Plaisant, 2005) is caused mainly by an inadequate navigational design of the hypermedia. Making up an adequate navigational design becomes even more challenging if groups of users differ with respect to their knowledge of a topic’s structure and if they have overlapping interests. The navigational design comprises two components: the structure of the hypermedia and the layout of user interfaces. The latter aspect is the focus of usability studies (e.g., Falk & Sockel, 2005); whereas, the former is less frequently discussed in the literature and is given scent mention in lectures at universities or business schools. This article is mainly devoted to the former aspect, and: • outlines the graph theoretic foundations for structuring hypermedia, • introduces multi-trees for customizing hypermedia with respect to different user groups, and • provides an overview of metrics to assess the navigational efforts of the user. The approach presented herein differs from wellestablished human-computer interaction studies (e.g., Arroyo, Selker, & Wei, 2006), because it aims at quantifying the users’ navigational efforts with respect to the structure of hypermedia systems rather than the interface design. This article presents a modeling approach, and all results are derived by a deductive analysis. The remainder of this conceptual article is structured as follows: subsequently, the opportunities of structuring hypermedia are outlined. Then components of users’ navigation efforts are discussed, and metrics for the assessment of navigational burdens are presented. Afterward, advantages of multi-trees are highlighted using a numerical example. Starting from a discussion of the limitations of this approach, avenues of future research are pinpointed. The final section provides the conclusions of this study.