Reasoning About Interactive Systems in Dynamic Situations of Use

Interactive software, systems and devices are typically designed for a specific (set of) purpose(s) and the design process used ensures that they will perform satisfactorily when used as specified. In many cases users will use these systems in unintended and unexpected ways where it seems appropriate, which can lead to problems as the differing usage situations have unintended effects on use. We have previously introduced a method of combining formal models of interactive systems with models of usage scenarios to allow reasoning about the effects that this unintended use may have. We now extend this approach to consider how such models might be used when considering deliberately extending the usage scenarios of existing interactive systems to support other activities, for example in emergency situations. This chapter explores a methodology to identify the effect of properties of emergency scenarios on the interactivity of interactive systems and devices. This then enables us to consider when, and how, we might utilise such devices in such emergencies.