MODIFIER: Improving an End-User Modifiable System Through User Studies

End-user modifiability allows different users to tailor a system to pursue different tasks, to have different preferences, and to adapt it to changing needs over time. User studies were performed with a system called MODIFIER, an end-user modification component for design environments. These studies helped refine previously hypothesized principles of end-user modifiability and identify new principles. The studies provided new insights about the requirements for system explanations. It also became apparent that system-maintained task agendas and critics can guide users through modification tasks. Unsolved problems were discovered and will be used as a guideline for future research.