A Planning Approach to Deal with Numeric Variables in Multiobjective Planning

Planning problems have been traditionally expressed by a propositional representation. However, this representation is not adequate to express numeric variables when modeling realworld continuous resources, such as fuel consumption, energy level, profit, etc. This paper presents our ongoing work to build a planner with capabilities for numeric variables, including duration on actions, and multiobjective optimisation to manage level 3 durative actions of PDDL2.1. Our approach consists of two stages. First, a spike construction process estimates the values of the variables associated to propositions/actions. Unlike other approaches, we do not relax numeric effects in the calculus of the estimation, but only numeric conditions. Second, a heuristic search process generates a relaxed plan according to the estimations of the first stage, and then performs search in a plan space. The relaxed plan and the heuristic estimations help the process find a plan while trying to optimise the multiobjective criterion.