Exploring regression-based narrative planning

A valid and believable narrative plan must often meet at least two requirements: the author's goal must be satisfied by the end, and every action taken must make sense based on the goals and beliefs of the characters who take them. Many narrative planners are based on progression, or forward search through the space of possible states. When reasoning about goals and beliefs, progression can be wasteful, because either the planner needs to satisfy the author's goal first and then explain actions, backtracking when an explanation cannot be found, or explain actions as they are taken, which may waste effort explaining actions that are not relevant to the author's goal. We propose that regression, or backward search from goals, can address this problem. Regression ensures that every action sequence is intentional and only reasons about the agent beliefs needed for a plan to make sense.