An Interactive Environment for Plan Visualization and Generation: InLPG∗

Introduction In the last years, the field of fully-automated plan generation has significantly advanced. However, in a real-world application it is likely that the plans synthesized by planning systems are not directly executable without an inspection of the user, who might require that some changes be performed in order to make the plan more suitable, robust or more preferable, or to update the problem specification, which could have evolved during the planning process. Moreover, for problems that are computationally hard, in order to effectively find a solution, it could be useful that a human interacted with the planner during search to help it. In the literature, several mixing initiative approaches to plan generation have been proposed (e.g., (Myers et al. 2003; Veloso, Mulvehill, & Cox 1997)). In this work, we present a planning environment, called InLPG, supporting plan visualization and mixed-initiative plan generation, in which the user interact with the state-of-the-art planner LPG. The human knowledge and requirements that are interactively handled by InLPG concern some aspects of: the plan under construction (e.g., the request of particular start times for some actions or the addition/removal of certain actions), the planning problem under consideration (e.g., the addition/removal of a problem goal), and the plan generation process (e.g., the introduction of landmarks or the modification of choices made by the automated search heuristics). Our system is an implementation of a more general approach aiming at: (i) providing a framework for domainindependent plan generation and visualization; (ii) supporting human interaction with a planner through some tools for effective plan visualizations and inspection; (iii) facilitating the use of planning technology to domain experts that are not planning experts; (iv) exploiting human advices during planning in order to help the planner to solve hard problems or to compute high quality solutions satisfying the user requirements.