Designing for "a" user: Stephen Hawking's UI

We present the Assistive Context Aware Toolkit (ACAT), a software platform that was designed for Professor Stephen Hawking to enable him to control his PC and communicate with others. While typical design practices focus on the needs of a large number of users, designing ACAT was an exploration targeted for a single user. We focused on understanding the needs of Professor Hawking, his assistants, and care-givers; explored his existing system, and its shortcomings; and iteratively designed and implemented a solution to address these needs and gaps. To support this iterative design and implementation, we designed and developed a configurable system that allowed us to explore different designs with minimal implementation effort. As a result, while ACAT was meant to address a single user, it turned into a tool that can easily be configured to support a wider range of disabilities and constraints. We will walk through our design journey, explain how ACAT evolved over time to serve Stephen's needs, and how it can be extended to support many others.