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

TLDR

Planning research has shifted toward realistic problems involving time and resources, driven by domains such as space exploration, logistics, and manufacturing, and motivated by the International Planning Competitions since 1998. The authors aimed to create a modelling language capable of expressing temporal and numeric properties of planning domains. They introduced PDDL2.1, detailing its syntax, formal semantics, and plan validation procedures. PDDL2.1 offers substantial modelling power beyond current planners and highlights significant research challenges.

Abstract

In recent years research in the planning community has moved increasingly toward s application of planners to realistic problems involving both time and many typ es of resources. For example, interest in planning demonstrated by the space res earch community has inspired work in observation scheduling, planetary rover ex ploration 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 modelling and reasoning issues that must be confronted to make planning technology meet the challenges of application. The International Planning Competitions have acted as an important motivating fo rce behind the progress that has been made in planning since 1998. The third com petition (held in 2002) set the planning community the challenge of handling tim e and numeric resources. This necessitated the development of a modelling langua ge 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 modelling power --- exceeding the capabilities of current planning technology --- and presents a number of important challenges to the research community.