Planning with Numerical Expressions in LPG

We present some techniques for handling planning problems with numerical expressions that can be specified using the standard planning language PDDL. These techniques are implemented in LPG, a fully-automated planner based on local search that was awarded at the third international planning competition (2002). First, we present a plan representation for handling numerical expressions called Numerical Action Graph (NA-graph). Then, we propose some extensions of LPG to guide a search process where the search states are NA-graphs. Finally, we give some experimental results showing that our techniques are very effective in terms of CPU-time or plan quality, and that they significantly improve the previous version of the planner.