PDDL2.1: An Extension to PDDL for Expressing Temporal Planning Domains

In recent years research in the planning community has moved increasingly towards application of planners to realistic problems involving both time and many types of resources. For example, interest in planning demonstrated by the space research community has inspired work in observation scheduling, planetary rover exploration and spacecraft control domains. Other temporal and resource-intensive domains including logistics planning, plant control, and manufacturing have also helped to focus the community on the modeling and reasoning issues that must be confronted to make planning technology meet the challenge of application. The International Planning Competitions have acted as an important motivating force behind the progress that has been made in planning since 1998. the third competition (held in 2002) set the planning community the challenge of handling time and numeric resources. This necessitated the development of a modeling language capable of expressing temporal and numeric properties of planning domains. In this paper, we describe the language, PDDL2.1, that was used in the competition. We describe the syntax of the language, its formal semantics, and the validation of concurrent plans. We observe that PDDL2.1 has considerable modeling power $exceeding the capabilities of current planning technology - and presents a number of important challenges to the research community