Extending Programming by Demonstration with Hierarchical Event Histories

Programming by Demonstration, or PBD, is an exciting and developing branch of HCI research. With PBD techniques, end-users can add functionality to their environments without programming in the conventional sense. Virtually all research into PBD, however, presumes that the event history is a linear sequence of user actions. This paper challenges that notion by introducing Hierarchical Event Histories, a new approach which represents some of the end-user's task structure directly in the event history. PBD systems can then take advantage of this structure to operate more correctly and in more situations. To assist programmers in generating structured histories, we also present Hieractors, a new model that provides a simple and clear syntax for describing arbitrary, high-level application behaviors.