In this paper we provide a formal framework for comparing the expressive power of Behavior Trees (BTs) to other action selection architectures. Taking inspiration from the analogous comparisons of structural programming methodologies, we formalise the concept of `expressiveness'. This leads us to an expressiveness hierarchy of control architectures, which includes BTs, Decision Trees (DTs), Teleo-reactive Programs (TRs) and Finite State Machines (FSMs). By distinguishing between BTs with auxiliary variables and those without, we demonstrate the existence of a trade-off in BT design between readability and expressiveness. We discuss what this means for BTs in practice.

翻译：在本文中,我们为比较行为树与其他行动选择结构的表达力提供了一个正式框架。我们从结构方案编制方法的类似比较中得到启发,正式确定了“表现性”的概念。这导致我们形成控制结构的表达性等级,包括BT、决策树、Teleo-反应方案(TRs)和Finite State Sydoms(FSMs)。通过区分具有辅助变量的BT和没有辅助变量的BT和没有变量的,我们表明在BT设计中存在着可读性和表达性之间的权衡。我们讨论了这对BT在实践中意味着什么。