In the GDC talk Emergent Storytelling Techniques in the Sims, Matt Brown discusses how the Sims create story trees using DAGs.
Each node in the DAG is an unrealized desire of the sim. For example, a sim wants to star gaze. If the player has them star gaze 3 times, that unlocks the desire in the sim to have a telescope. If the player gets the sim a telescope that unlocks the desire in the sim to discover a planet.
Chain-able desires can be used to create emergent narrative. Most of these desires are hidden by the player.
In the GDC talk Emergent Storytelling Techniques in the Sims, Matt Brown discusses how the Sims create story trees using DAGs.
Each node in the DAG is an unrealized desire of the sim. For example, a sim wants to star gaze. If the player has them star gaze 3 times, that unlocks the desire in the sim to have a telescope. If the player gets the sim a telescope that unlocks the desire in the sim to discover a planet.
Chain-able desires can be used to create emergent narrative. Most of these desires are hidden by the player.