Modeling Complex Work Systems - Method meets Reality Gerrit C. van der Veer Machteld Hoeve Bert F. Lenting Dep. of Computer Science Dep. of Computer Science CTIT Vrije Universiteit, Amsterdam, NL Vrije Universiteit, Amsterdam, NL Twente University, Enschede, NL gerrit@cs.vu.nl mhoeve@cs.vu.nl lenting@ctit.utwente.nl ABSTRACT Modeling an existing task situation is often a first phase in the (re)design of information systems. For complex systems design, this model should consider both the people and the organization involved, the work, and situational aspects. Groupware Task Analysis (GTA) as part of a method for the design of complex systems, has been applied in a situation of redesign of a Dutch public administration system. The most feasible method to collect information in this case was ethnography, the resulting task model needed the GTA formalism to be adjusted to situational aspects of the work. The study shows that GTA as an approach is feasible in complex design cases, and that the formalism allows adjustment to cover situational aspects, while still keeping its cognitive ergonomic value for design. Keywords Ethnography, Groupware, GTA, Task analysis INTRODUCTION Various design approaches currently exist in Cognitive Ergonomics. The common characteristic is attention to users and user relevant aspects of the system to be developed. The implementation of this attention, however, is very divers. In this introductory section we will briefly mention some viewpoints. In current user interface design practice, different viewpoints and approaches are often combined or integrated. First of all, some approaches are based on user participation (Mumford, 1987). Attention to the user and his task situation is not based on systematic analysis and representation of task knowledge, but on the availability of the users during the design process. These methods allow users, who are not professional designers, to influ- ence design decisions in a very direct and explicit way. A different viewpoint can be found in design methods that stress the importance of systematic knowledge of existing task situations. Many approaches are based on cognitive psychological theory. TKS (Johnson, 1989), the Hierarchical Planning method (Sebillotte, 1988), and MAD (Scapin & Pierret-Golbreich 1989) present a method where design starts mainly with investigating current task knowledge. Methods of this type apply a conceptual framework that is derived from psychological notions on human memory and human planning. The prospective system users provide the knowledge that is subsequently represented in task models that feature as the main source for subsequent design activities. The design requirements and decisions are strongly based on these task models, where the (professional) users only indirectly contribute to this. Again, a different perspective may be found in the mainstream of CSCW design methods. Here, again, the existing task situation is the primary source for design. However, not the psychological basis of expert knowledge is considered, but the task-knowledge that can be experienced in current work situations and in "communities of practice". Activity Theory (Nardi, 1995) and ethnographic approaches (Jordan, 1996) are the main theoretical foundations for methods that aim at acquiring insight in current situated task domains. Design is based on this insight. Different from the previous type of approaches, however, the analysis of the current task situation is not guided by an a priory conceptual framework, nor is it followed by a formal representation of the task structure. Many approaches (though mainly the knowledge oriented views) apply representation-techniques, conceptual frameworks or models to accommodate user- oriented viewpoints: CLG (Moran, 1981), GOMS (Card, Moran & Newell, 1983), CCT (Kieras & Polson, 1985), TAG (Payne & Green, 1986) and ETAG (Tauber, 1990) each provide methods to explicitly consider user related characteristics in design, mostly based on cognitive psychological theories. In these types of approaches, it is the designer who evaluates human aspects as part of design specifications, systematically considered with the help of the model or framework, in order to optimize the design. The framework provides a model of cognitive aspects of the user, in the form of a competence model or a performance model (de Haan, van der Veer & van Vliet, 1991). The approach that we will present in this contribution is an attempt to integrate several viewpoints: we start our design by investigating knowledge of the current task situation. We apply different methods for this, related to the complexity of the human-machine system to be designed - both knowledge elicitation and ethnographic methods may be needed depending on the current task situation. We apply a conceptual framework that is based on a priory notions of human cognition and on our vision on situated tasks, as well as on our vision of the further design of complex systems. Finally, we apply a formal modeling approach. In this way we interpret and model the task world, as far as it is relevant for the designer, NOT as a complete account of the world as it exists for the people living in it. Part of our approach will be illustrated in this paper. Our complete view on design considers several phases of design decisions, guided by explicit design rationale, which will not be discussed in detail (Van der Veer, van Vliet and Lenting, 1995). In the next section we elaborate our task analysis method GTA, which may be considered the first phase of design in this view (other