From AIGPG Wiki
A behavior tree is an architecture for selecting contextually-appropriate actions for a given situation.
Behavior trees rose to use in the mid-2000s with prominent usage in games such as Halo 2
Games That Use This Architecture
(Too numerous to list)
- Handling Complexity in the Halo 2 AI, Damián Isla, GDC, 2005
- Decision Making and Knowledge Representation in Halo 3, Max Dyckhoff, NIPS, 2007