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

TL;DR

PDDL2.1 extends the Planning Domain Definition Language to better model and reason about temporal and resource constraints in realistic planning problems, advancing the capabilities of automated planning systems.

Contribution

This paper introduces PDDL2.1, a new language extension that enhances the expressiveness of planning models for temporal and numeric domains, used in international competitions.

Findings

PDDL2.1 has greater modeling power than previous languages.

It formalizes syntax and semantics for temporal planning.

The language presents new challenges for planning research.

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.