Planning while Executing: A Constraint-Based Approach

We propose a planning architecture where the planner and the executor interact with each other in order to face dynamic changes of the application domain. According to the deferred planning strategy proposed in [14], a plan schema is produced off-line by a generative constraint based planner and refined at execution time by retrieving up-to-date information when that available is no longer valid. In this setting, both planning and execution can be seen as search processes in the space of partial plans. We exploit the Interactive Constraint Satisfaction framework [12] which represents an extension of the Constraint Satisfaction paradigm for dealing with incomplete knowledge. Given the uncertainty of the plan execution in dynamic environments, a backup and recovery mechanism is necessary in order to allow backtracking at execution time.