The claim of this paper is that reuse on the Web - if sensibly facilitated - can be achieved in a much more intuitive and efficient fashion than today. The idea is to invert the current perspective on reuse by moving away from programmer-oriented artifacts, such as APIs, web services and data feeds, and focusing on user-oriented artifacts, i.e., graphical user interfaces (UIs). The paper defines a new kind of API, the interactive API (iAPI), which reconciles the intuitiveness of interactive UIs with the power of programmable APIs and enables (i) programmatic access to UIs and (ii) interactive, live programming. The paper discusses use cases and implementation options and lays the foundation for UI-oriented computing as a discipline. © Sprin...