Sequencing formally defined reactions for robotic activity: integrating RAPS and GAPPS

Construction of robots which operate in unstructured environments has of late produced a number of approaches for transforming sensor readings into activity in the world. Most of these approaches provide no formal semantics for discussing the way in which the internal state of the robot maps to the desired state of the world. We have been investigating the use of the GAPPS programming language as a mechanism for defining robotic reactions. This work has resulted in the creation of reactive modules which mediate between discrete statements about world states to achieve or maintain and the required continuous activity. While relatively complex goals have been achieved with this approach, the syntax and semantics of the GAPPS language is inappropriate for complicated dynamically changing goals. As a result, we have begun investigating the use of Reactive Action Packages (RAPs) as a mechanism for sequencing the activation of GAPPS-based reactive skills. The motivation for using RAPs is twofold. First, the syntax and semantics of the RAPs language integrates smoothly with a traditional non-linear planning system, allowing the construction and execution of plans for increasingly complex tasks. Second, GAPPS-based reactions fulfill a missing component of a RAPs-based controller system, namely the transformation of discrete RAP primitives (e.g., (maintain grasp ?thing)) into continuous physical activity. This paper presents the approach we are taking and discusses some of the issues involved in integrating these two systems.