Plan decoupling of agents with qualitatively constrained tasks

In many task-planning domains, assemblies of autonomous agents need to construct plans and schedules for executing their assigned sets of tasks in order to complete them. Often, there will be dependencies between tasks to be executed by different agents. In such a situation, a plan-coordination problem arises when the joint plan is required to be feasible, whatever locally-feasible plans the individual agents come up with. This problem can be solved by plan decoupling, which is to add a minimum number of constraints such that each agent can make a plan for its set of tasks independently of the others while still joint-plan feasibility is guaranteed. Previous work on plan decoupling concentrated on a coordination framework where the only dependencies between tasks are precedence constraints. In this paper, an extension of the framework is discussed where not only precedence constraints, but also synchronisation constraints can be used in order to express qualitative temporal constraints between tasks. It is shown that adding synchronisation constraints does not add any complexity to the plan-decoupling problem, and that a previously-developed approximation algorithm for plan decoupling can be extended to cope with synchronisation constraints as well.