Representation still matters: cognitive engineering and user interface design

With the increased utilization of cognitive models for designing user inter faces several disciplines started to contribute to acquiring and representi ng knowledge about users, artifacts, and tasks. Although a wealth of studie s already exists on modeling mental processes, and although the goals of co gnitive engineering have become quite clear over the last decade, essential epistemological and methodological issues in the context of developing use r interfaces have remained untouched. However, recent challenging tasks, na mely designing information spaces for distributed user communities, have le d to a revival of well known problems concerning the representation of know ledge and related issues, such as abstraction, navigation through informati on spaces, and visualization of abstract knowledge. All of these issues are associated with mental processes and thus, might become part of cognitive models. In this paper we reveal epistemological and methodological assumptions in t he field of cognitive modeling as well as their implications for user inter face design. It turns out that in order to achieve the goal of developing h uman-oriented (in contrast to technology-driven) human-computer interfaces developers have to develop knowledge of the structure and the representatio nal dynamics of the cognitive systems which are interacting with the comput er. We show that in a first step it is necessary to study and investigate t he different levels and forms of representation that are involved in the in teraction processes between computers and human cognitive systems. We propo se a hybrid user modeling approach as part of the task-based development pr ocedure in TADEUS (Task Analysis/Design/End User Systems). The hybrid appro ach does not only enable the representation of functional roles end users h ave to perform, but also how end users perform these roles, i.e. the repres entation and reflection, if not prediction of their behavior. This way, hol istic system development that equally takes into account the organizational requirements and the end user reality at work places is facilitated.