Planning-based systems can be integrated into any of the above approaches to ensure narrative cohesion. The system does this by anticipating potential holes in the plot and repairing them by introducing new information and events. Two such systems include Automated Story Director (ASD), which forms narrative repairs based on plot points predefined by the author, and Player-Specific Automated Storytelling (PAST), which chooses from several possible repairs according to the player's previous behaviors. PAST characterizes a player along five vectors of style based on Robin Laws' work on player types—fighter, power gamer, storyteller, method actor, and tactician—and may choose to solve a broken plot point for a fighter by adding a battle with a new character, or for a storyteller by adding new background information that justifies the break.