Behavior Trees: From Systems Engineering to Software Engineering

Geoff Dromey's Behavior Engineering method provides a vital link between systems engineering processes and software engineering processes. It has proven particularly effective in industry when applied to large complex systems, to help understand the problem space and clarify system and software requirements. In this paper we compare the method with some of the most widely used system design methods, including State Transition Diagrams, Functional Flow Block Diagrams, Object Oriented Design, IDEF0, UML and SysML. The comparison draws on the Design-Methods Comparison Project undertaken by Bahill et al in 1998, and uses their Traffic Lights case study. We show that the methods are roughly equivalent in terms of what they can express, but that Behavior Trees come closest to natural language specification, which we contend makes them easier for non-formal methods experts to understand.