The method on which we depend here is the notion of means-ends analysis. We consider the means at our disposal to achieve our goals by reducing the difference between our current state and the goal state by as much as possible. Hence if I want to get to Paris I should first consider which operator will take me nearest to Paris with one operator application.
We discuss this in terms of ann influential way of doing means-ends analysis: planning. We introduce this in the framework of a system known as STRIPS (STanford Research Institute Problem Solver). Though this has been around for about 25 years it still provides a very popular representation for planning. The STRIPS planner was developed to control a robot called SHAKEY. SHAKEY lived in a world with a number of rooms and various boxes. SHAKEY would be given the goal to push a box from one place to another (for example).
There are problems with this approach. For example, problems are not always solved by moving `closer' to the goal. Sometimes, the goal may be achieved by apparently moving away from the goal (c.f. the `unnatural' move required to solve the missionaries and cannibals problem).