Gap analysis consists of defining the present state, the desired or `target' state and hence the gap between them. In the later stages of problem solving the aim is to look at ways to bridge the gap defined and this may often be accomplished by backward-chaining logical sequences of actions or intermediate states from the desired state to the present state. In other words, asking the question:
"What (b) must be in place, or must have happened in order that this desired state (a) can exist?"
- then -
"What (c) must be in place, or must have happened in order that this desired state (b) can exist?"
Gap analysis alone however is not adequate for all problem situations as goals may evolve and emerge during the course of problem solving, "what ought to be" can be a highly variable target. Also, some problems have many alternative solutions, in which case backward-chaining search strategies will have little practical use.