Vehicles and their drivers may occasionally need resources that can be considered "external" to the delivery process itself. For example, there may be handling resources such as people, cranes, or docking bays at a depot that are necessary to load the trucks, or there may be trailers (shared between vehicles) that are used for the deliveries. External resources can be modeled with IBM ILOG Scheduler and incorporated into your Dispatcher program, thus increasing your ability to model various delivery problems.

This lesson demonstrates the use of external resources by starting with a standard Pickup and Delivery Problem (PDP) and adding the requirement to use one of a limited number of depot docking bays to load the trucks. Three docking bays are used to load up to 15 vehicles. There is a break on each docking bay, which represents a break for the people loading the vehicles.

The first step is to write a natural language description of the problem. A good way to start this process is to analyze the constraints and objectives.

What are the constraints in this problem?

The objective is to minimize the cost of the delivery of all the parcels.