Andrew Stern's response (excerpt)
Both Thespis and Façade are making unexpected, "exotic" departures from their respective fields [for more on Façade, see Michael Mateas's First Person essay]. On the spectrum between hypertext and the Holodeck, Thespis offers hypertext rich in character; Façade offers an animated virtual world rich in dialog and introspection. Just as Bernstein and Greco are careful to point out about Thespis, Façade is not a game, it is not about realism. It is drama. The goal is not to "win" but to experience a compelling story, which in Façade 's case does not have a happy ending. And although we employ AI techniques, we too are only after the appearance of intentionality and individuality -- the core tenet of the believable agent approach to artificial intelligence (Bates, Loyall, and Reilly 1992). Façade 's simple models of psychology, emotion, and language understanding are customized to the requirements of our story; they are no more than sophisticated ways of keeping track of the story state that matters theatrically. That is, we are using AI techniques for artistic purposes; we are not creating realistic cognitive models.
Bernstein and Greco propose cards, each containing a brief, focused passage of text and annotated with constraints on the context in which they can be used and modifications they make to the reading context. The cards are played out using a simple set of rules by a single reader (Card Shark) or potentially by multiple readers (Social Shark). They say, "Rather than create complex actors, we create simple automata that say interesting things about important matters."
Like Card Shark cards, Façade 's story beats are annotated with preconditions and effects. The Façade beat manager runs a set of rules that decides which beat to play next, by searching for authored story beats with preconditions that match the player's current interactions and the story memory (what has happened so far). When multiple beats are available to play at any one time, the system may look at the effects of each beat and choose the one that best matches the dramatic arc the author is trying to achieve.