Gerhard Fischer 1 UMUAI: 10th Anniversary IssueContribution to the 10th Anniversary Issue of the Journal ÒUser Modeling and User-AdaptedInteraction (UMUAI)ÓUser Modeling in Human-Computer InteractionGerhard FischerCenter for LifeLong Learning & Design (L3D)Department of Computer Science and Institute of Cognitive ScienceAbstractA fundamental objective of human-computer interaction research is to make systems moreusable, more useful, and to provide users with experiences fitting their specific backgroundknowledge and objectives. The challenge in an information-rich world is not only to makeinformation available to people at any time, at any place, and in any form, but specifically to saythe ÒrightÓ thing at the ÒrightÓ time in the ÒrightÓ way. Designers of collaborative human-computer systems face the formidable task of writing software for millions of users (at designtime) while making it work as if it were designed for each individual user (only known at usetime).User modeling research has attempted to address these issues. In this article, I will first reviewthe objectives, progress, and unfulfilled hopes that have occurred over the last ten years, andillustrate them with some interesting computational environments and their underlyingconceptual frameworks. A special emphasis is given to high-functionality applications and theimpact of user modeling to make them more usable, useful, and learnable. Finally, an assessmentof the current state of the art followed by some future challenges is given.Keywordsuser modeling, human computer interaction, collaborative human-computer systems, highfunctionality applications, adaptive and adaptable systems, active help systems, critiquingsystems, design environmentsGerhard Fischer 2 UMUAI: 10th Anniversary IssueTable of ContentsIntroduction...................................................................................................................3The Evolution of Human-Computer Interaction ...........................................................3User Modeling in HCI....................................................................................................6How the West Was Won — An Early Success Example of User Modeling..............................6High-Functionality Applications.....................................................................................................7Knowledge-Based Help Systems.....................................................................................................9Design Environments and Critiquing Systems...........................................................................10Assessment of Progress................................................................................................ 12Future Challenges .......................................................................................................13Conclusions.................................................................................................................. 14References.................................................................................................................... 15List of FiguresFigure 1: The Human-Computer Dyad _____________________________________________________ 4Figure 2: Knowledge-Based HCI__________________________________________________________ 4Figure 3: Design and Use time ___________________________________________________________ 5Figure 4: Levels of Users' Knowledge about a High-Functionality Application ______________________ 7Figure 5: Functionality and its Relevance to the Task at Hand ___________________________________ 8Figure 6: Distributed Expertise in HFAs ____________________________________________________ 9Figure 7: An Example of a Specific Plan Specialist___________________________________________ 10Figure 8: Adaptation Mechanism to Control Different Critiquing Rule Sets and Different InterventionStrategies___________________________________________________________________________ 12List of TablesTable 1: A Comparison between Adaptive and Adaptable Systems _______________________________ 11Gerhard Fischer 3 UMUAI: 10th Anniversary IssueIntroductionUser modeling is one of a number of research areas that intuitively seem to be winningpropositions and worthwhile investments based on their obvious need and potential payoff.Other domains comparable to user modeling are (1) software reuse (e.g., reuse can be justified bythe fact that complex systems develop faster if they can build on stable subsystems), and (2)organizational memories and organizational learning (e.g., creating socio-technical environmentsthat help to transcend the limitation of the individual human mind). These approaches seem to beappealing, natural, theoretically justifiable, desirable, and needed. But in reality, progress in theseareas has been slow and difficult, and success stories are rare.In this article I first analyze the evolution of human-computer interaction (HCI) as a research areaover the last 15 years and briefly characterize problems for HCI for which user modeling mayprovide some answers. I describe a set of selected themes and examples illustrating usermodeling approaches in HCI. I conclude by giving a brief assessment of the present state of usermodeling and by enumerating a few challenges for the future. This paper is closely related to twoother contributions in this volume: ÒLearner ControlÓ by Judy Kay [Kay, 2000] and ÒAdaptiveTechniques for Universal AccessÓ by Constantine Stephanidis [Stephanidis, 2000].The Evolution of Human-Computer InteractionHCI studies the interactions and the relationships between humans and computers. HCI is morethan user interfaces and more than Òscreen-deepÓ[Computer Science and Technology Board -National Research Council, 1997]; it is a multidisciplinary field covering many areas [Helander etal., 1997]. In the first ten to fifteen years of its history, HCI has focused on interfaces (particularlyon the possibilities and design criteria for graphical user interfaces (GUIs) using windows, icons,menus, and pointing devices (WIMPs)) to create more usable systems. As interface problemswere better understood, the primary HCI concerns started to shift beyond the interface (torespond to observations as articulated by D. Engelbart: ÒIf ease of use was the only valid criterion,people would stick to tricycles and never try bicyclesÓ). More recent HCI research objectives [Fischer,1993a] are concerned with tasks, with shared