Task-related principles for user interface design

1. Introduction HCI research and design practice has long recognized that interactive systems are useless if they do not support users in performing their work tasks. To this end, the representation and modeling of users' task knowledge is a major concern. In particular, a key concern is how to make informed design decisions based upon that knowledge and how to predict the effects of design solutions upon the people who will use them, i.e. the usability consequences of the design. Many existing task analysis (TA) approaches provide descriptive models of the work task knowledge people possess. It is assumed that a description of existing knowledge can be used in the design of interactive systems. The underlying principle behind this assumption is knowledge transfer: carrying over task structure and content from the current work situation to the new (i.e. designed) work system is assumed to support learning. However, we believe that a move from this descriptive and analytical input to design to a more prescriptive and predictive form of HCI design is desirable. To this extent we are developing principles to enable designers to be guided by task-related principles and to predict the consequences of their design decisions.