Should Heuristics refer to PlanManager?

We decided earlier that each Cost is fixed by one particular CostCenter - this mapping is statically defined. While this decision simplifies the workflow of Cost Repair, it creates new problems.

Take the case of Logistics domain. We have actions of LoadTruck, UnloadTruck and MoveTruck that modify the location of a packet. We have a goal to move a certain packet_1 from one location to another. According to our decision, this goal is a Cost to be repaired by the location attribute of packet_1.

The location attribute of packet_1 knows about the actions that alter its value. The actions LoadTruck and UnloadTruck do. However, for repair of the Cost, a truck is needed (on which the packet will be loaded). Now the location attribute of packet_1 does not know anything about a good truck to instantiate LoadTruck.

There are two options here: 1) the location attribute instantiates LoadTruck with a random truck (in the hope that the resultant cost will be fixed later), or 2) the location attribute asks the PlanManager about a good truck.

In the first option, we need to introduce a heuristic changeParameter to change a parameter of the LoadTruck action later. Also, probably it is better for the PlanManager to remember (and not lose the information) that a random truck was used to instantiate the LoadTruck action and fix the associated cost in this manner. One simple way to implement this is by using a dummy truck (which is a placeholder for a real truck) to instantiate LoadTruck. Cost due to dummy truck will be fixed by a new changeParameter heuristic.

The second option is quite intrusive change, more unpredictable and thus more difficult to parallelize. It is more unpredictable because the PlanManager may be busy with other tasks when the request for a good truck came, in which case the requesting location attribute would have to wait. However, it is noted that the second option may be needed to be used in more complex repairs, but not in the simple case we are dealing with right now.

Another thing: Note that in the first option, we would like to call changeParameter heuristic (and no other heuristic) whenever the Cost is on the dummy object. Therefore, in general a CostCenter must perform some pre-inspection to select an appropriate class of heuristics to fix a particular cost (this pre-inspection right now includes looking at the type of cost - whether it is a goal cost of condition cost).