Exploring usability: design for dynamic and diverse use situations

This thesis discusses the relationship between the usability of products and the dynamics and diversity of use situations, and how this can be dealt with in product design processes. The usability of products is influenced by the situation in which the product is used. Consequently, when products are used in dynamic and diverse use situations (DDUS) the level of usability is diverse as well. For designers it could be difficult to predict these use situations and their consequences for usability. A study in design practice showed that designers often use knowledge of personal experiences or previous design projects for this purpose. However, this knowledge is often not shared between members of a product development team. This can negatively influence decision making with regard to choosing the best solution proposal or choosing the use situations which the product should accommodate. Moreover, it can negatively influence the external validity and focus of usability evaluations. Therefore a set of design guidelines was developed aimed at guiding designers in creating an explicit frame of reference of DDUS and the consequences for usability, and applying this frame of reference in decision making and usability evaluations. Furthermore, the Envisioning Use workshop technique was developed, which is aimed at sharing implicit and explicit knowledge of DDUS in a product development team, by jointly creating a first explicit frame of reference. Both the workshop and the guidelines were developed iteratively by applying and evaluating these supports in multiple design projects in both design practice and student projects. The evaluations showed that the workshop not only led to an explicit frame of reference of DDUS, but to a `shared vision¿ on product use as well. This shared vision was experienced as valuable in decision making processes. The application of the guidelines furthermore showed that working with an explicit frame of reference indeed leads to more focus in usability evaluations, and can improve their external validity. Finally the studies showed that `exploring usability¿ is a valuable approach in creating the explicit frame of reference. This approach combines exploring with verifying the connections between DDUS and usability issues.