A theory of conflict resolution in planning

Abstract

Conflict resolution in planning is the process of constraining a plan to remove harmful interactions that threaten its correctness. It has been a major contributing factor to the complexity of classical planning systems. Traditional planning methods have dealt with the problem of conflict resolution in a local and incremental manner, by considering and resolving conflicts individually. This paper presents a theory of conflict resolution that supports a global consideration of conflicts. The theory enables one to formally represent, reason about and resolve conflicts using an extended framework of constraint satisfaction. The computational advantage of the theory stems from its ability to remove inconsistencies early in a search process, to detect dead ends with low computational overhead, to remove redundancies in a search space, and to guide the search by providing an intelligent order in which to resolve conflicts. The paper also presents empirical results showing the utilities of the theory, by investigating the characteristics of problem domains where the theory is expected to work well, and the types of planning systems for which the theory can offer a marked computational advantage.