This series of pages shows the steps in a means-ends search for finding a plan for key steps in managing a fire team for firefighting on a Navy ship. The team starts out in a repair locker, and returns their after the fire is extinguished. The goal of the team is to put the fire out, remove smoke and water, test the gases, return to the locker, and store their equipment. Before extinguishing, they must deenergize (turn the power off) and set boundaries. After extinguishing, they must test the gases, desmoke, and dewater. The possible actions in this simulation are extinguish, desmoke, dewater, set(boundaries), test(gases), estimate(water), go(fire), go(locker), equip, and store(equpiment). At each step in the demonstration, you are asked to figure out what it will do next.
The means-ends search algorithm is a form of hierarchical planning. It works "top-down", reasoning about goals and what is necessary to achieve them. It can be described as a form of recursive search decomposition. A prioritized list of actions (operators) is checked; the highest-priority action for the difference between the current goals and the current state is selected. Search is then decomposed into two subsearches: (1) a search to achieve the preconditions of the recommended action (which can be null if the preconditions are already achieved); (2) a search to achieve the original goals after the recommended action is done (which can be null if the postconditions did achieve all the original goals). Backtracking can be used if the first-recommended action cannot lead to achieving the goals.