The field of HCI is gradually achieving sound theoretical descriptions of the activities, context and cognition of computer system users. How do these research results get applied by the people who design new user interfaces? Although we have theoretical descriptions of the activities of system users, we have fewer descriptions of the design activities of user interface designers. There are certainly theory-based design methods prescribing the things that designers ought to do. Almost all of these have been developed from the perspective of descriptions of the user, rather than from consideration of the needs of designers – the current vogue for “user-centred design ” clearly expresses this emphasis on the user. According to this perspective, if user interface designers are to apply research into user needs, those designers must be able (and interested) to interpret and apply theoretical results. Alternatively, there are also many popular approaches to user interface design that have minimal theoretical grounding. Such design methodologies generally attempt to present designers with a checklist (Nielsen & Molich 1990) or a procedural list of design activities (Wharton, Rieman et. al. 1994) that will generate a good design. The reduction of design to a checklist or a predefined procedure is widely proposed in other areas of software development,