Behavior Trees with Dataflow: Coordinating Reactive Tasks in Lingua Franca

TL;DR

This paper introduces a dataflow extension to Behavior Trees, explicitly modeling data relations to improve reusability and determinism, implemented and validated within the Lingua Franca coordination language.

Contribution

It presents a novel dataflow extension to Behavior Trees, enhancing their expressiveness and integration in Lingua Franca for reactive task coordination.

Findings

Extended BTs explicitly model data relations.

Validated approach improves modularity and determinism.

Implemented in Lingua Franca for reactive task coordination.

Abstract

Behavior Trees (BTs) provide a lean set of control flow elements that are easily composable in a modular tree structure. They are well established for modeling the high-level behavior of non-player characters in computer games and recently gained popularity in other areas such as industrial automation. While BTs nicely express control, data handling aspects so far must be provided separately, e. g. in the form of blackboards. This may hamper reusability and can be a source of nondeterminism. We here present a dataflow extension to BTs that explicitly models data relations and communication. We provide a combined textual/graphical approach in line with modern, productivity-enhancing pragmatics-aware modeling techniques. We realized and validated that approach in the recently introduced polyglot coordination language Lingua Franca (LF).