For example, at first glance a POL system may seem to have nothing to do with air defense. However, an air defense fighter aircraft at an airfield with no POL can defend nothing. There are three types of links that we may encounter when we study target systems. The ability to recognize the nature of the coupling and its implications can prove very valuable to our targeting efforts. We need to be able to recognize them.
Targets share common resources but are otherwise independent from each other.
In general, the targets in a pooled coupling tend to resemble one another, decreasing the probability of uniqueness. Critical nodes may tend to be more scarce in a set of pool-coupled targets. One might think of an army that does its basic training in a number of different places. Each of the basic training sites gets part of its input in the form of people from the population at large. Each site receives its program of instruction from the same higher authority.