Privacy and proportionality

We argue that an analytic proportionality assessment balancing usefulness and burden on individual or group privacy must be conducted throughout the design process to create acceptable ubiquitous computing (ubicomp) applications and services. We introduce the principle of proportionality, which originates within the legal and data protection communities. Inspired by this principle, we develop a design method for ubicomp applications, based on our own experience, and aimed at HCI practitioners and designers. We discuss the method in relation to real-world examples, user inquiry techniques and requirements engineering models. Finally, we report a sample application of the method, involving a ubiquitous, personal memory aid tool.