Planning with Action Abstraction and Plan Decomposition Hierarchies

Useful and suitable action representations, with accompanying planning algorithms are crucial for the task performance of many agent systems, and thus a core issue of research on intelligent agents. An efficient and expressive representation of actions and plans can allow planning systems to retrieve relevant knowledge faster and to access and use suitable actions more effectively. Two general approaches have been pursued in the past; STRIPS-based planners, which construct plans from scratch, based on primitive action descriptions and planners using pre-defined Plan Decompositions Hierarchies, also known as Hierarchical Task Networks. In our research, we integrated both an inheritance hierarchy of actions, using STRIPS-like action descriptions, with a plan decomposition hierarchy, which consists of pre-defined plan schemata. This combination is suitable for a richer action and plan representation, and thus an improved planning algorithm. We implemented and tested this approach for a prototypical example application: the travel planning domain.