Bridging software design and usability analysis through task modelling

A user-centred approach to systems design and evaluation is presented. In particular task modelling is proposed as a bridging technology for understanding users' needs, feeding this understanding into design and evaluating the usability of design choices. The approach is proposed as a general methodological framework for the design, the development and the evaluation of interactive systems. We discuss the beneficial bridging effects of task modelling throughout the development life cycle presenting the experience of the Esprit Project CHARADE, an integrated system for handling environmental emergencies. The main aspects of our experience are reported highlighting how the system life cycle has been characterized by an early and continual involvement of the final user and how task analysis and modelling are shared resources for the entire development process. Key-words : task analysis, task model, human factors, user-centered design, dialog management, software engineering, usability evaluation.