PDDL+ : Modelling Continuous Time-dependent Effects

The adoption of a common formalism for describing planning domains fosters far greater reuse of research and allows more direct comparison of systems and approaches, and therefore supports faster progress in the field. A common formalism is a compromise between expressive power (in which development is strongly driven by potential applications) and the progress of basic research (which encourages development from well-understood foundations). The role of a common formalism as a communication medium for exchange demands that it is provided with a clear semantics. This paper describes extensions of PDDL2.1 (used in the 3rd International Planning Competition) that support the modelling of continuous time-dependent effects and illustrates why they can play a critical role in modelling real domains.