Thespian: a decision-theoretic framework for interactive narratives

With the rapid development of computer technology, a new form of media – interactive narrative has received increasing attention. Interactive narrative allows the user to participate in a dynamically unfolding story, by playing a character or by exerting directorial control. By allowing the user to interact, interactive narrative provides a richer and potentially more engaging experience than traditional narrative. Moreover, because different choices of the user lead to different paths through the story, the author of interactive narrative can tailor the experience for the user or user groups. The design of interactive narrative faces many challenges. The central challenge comes from the integration of interactivity into the narrative. Instead of presenting one well-crafted static story, the author has to design the characters' behaviors along many paths through the story in response to possible user interactions. The amount of work can easily overwhelm an author. In this thesis, I present a multi-agent approach to modeling and simulating interactive narrative, implemented as the Thespian framework. Thespian utilizes a two-layer runtime system to drive the characters' interactions with the user. At the base is a multi-agent system comprised of goal-oriented autonomous agents that realize the characters in the story. Above this layer is a proactive director agent that continuously monitors the progress of the story and directs the characters toward the author's plot design goals. In addition to the two-layer runtime system, Thespian contains offline authoring procedures to facilitate the author in configuring the characters. The evaluation of the Thespian framework has been performed at different levels. Various components within Thespian have been individually evaluated or validated. In addition, Thespian's generality in practice for authoring a range of stories has been demonstrated through its many applications in different domains.