It may be noted that this solution corresponds to the schedule shown in Figure 3 (and Figure 7); it can also be determined that this schedule is most optimal in terms of resource requirements if time step constraint is 4.

Now a question arises, if FDS can do the same schedule (Figure 7) then why we need the complex ILP based solution. The answer to this question lies in the fact that FDS may not always lead to optimal solution while ILP guarantees to generate the most optimal solution. In the question and answer section of this lecture, we illustrate a situation when FDS may not generate an optimal solution.