Behavior tree

A behavior tree is a structured visual modeling technique used in systems engineering and software engineering to represent system behavior. It uses a hierarchical tree diagram of nodes and connectors to show control flow and system actions, replacing ambiguous natural language requirements with standardized boxes, arrows and symbols. Requirements are first translated one by one into requirement behavior trees, which keep the vocabulary of the original requirements, and these are then composed into an integrated behavior tree that gives a single view of the behavior the requirements imply. Once defects found in the integrated tree are corrected, it becomes a model behavior tree that serves as a formal specification, and parts of it can be made executable. Because the notation has formal semantics given through a process algebra, behavior trees can be simulated, model checked and used for failure mode and effects analysis. The technique was developed by Geoff Dromey, with the first publication of key ideas in 2001, and is applied in the process called behavior engineering. The article is about this requirements modeling technique and notes that the behavior trees popular in computer game artificial intelligence are very different from it.