Let us consider an OPL program defining a transportation model. A certain set of products are manufactured and consumed in a set of cities. Data describing the supply is given specifying how much of each product is manufactured at each city, how much of each product is consumed at each city, and how much it costs per unit of product to be shipped from each city to each city. We want to establish how much of each good to transport between cities in such a way as to meet the demand within the supply and minimize the total cost.
The complete listing of an OPL program defining a model for a transportation problem is given in Appendix Section B. I will refer to the line numbers of that listing in the following discussion.