SAPA: A Multi-objective Metric Temporal Planner

TL;DR

SAPA is a domain-independent heuristic planner capable of handling durative actions, resource constraints, and multiple objectives, with novel heuristic derivation and plan optimization techniques demonstrated in competitive settings.

Contribution

The paper introduces new heuristic methods for multi-objective metric temporal planning and a post-processing technique to enhance plan flexibility.

Findings

SAPA performed well in the third International Planning Competition.

Heuristic derivation methods improve planning efficiency.

Post-processing enhances plan execution flexibility.

Abstract

SAPA is a domain-independent heuristic forward chaining planner that can handle durative actions, metric resource constraints, and deadline goals. It is designed to be capable of handling the multi-objective nature of metric temporal planning. Our technical contributions include (i) planning-graph based methods for deriving heuristics that are sensitive to both cost and makespan (ii) techniques for adjusting the heuristic estimates to take action interactions and metric resource limitations into account and (iii) a linear time greedy post-processing technique to improve execution flexibility of the solution plans. An implementation of SAPA using many of the techniques presented in this paper was one of the best domain independent planners for domains with metric and temporal constraints in the third International Planning Competition, held at AIPS-02. We describe the technical details of extracting the heuristics and present an empirical evaluation of the current implementation of SAPA.