Overview of Part III: Decision-Theoretic Planning

Planning Under Uncertainty

As in Part II, it also seems appropriate to give two names to Part III. It is officially called decision-theoretic planning, but it can also be considered as planning under uncertainty. All of the concepts in Parts I and II avoided models of uncertainties. Chapter 8 considered plans that can overcome some uncertainties, but there was no explicit modeling of uncertainty.

In this part, uncertainties generally interfere with two aspects of planning:

1. Predictability: Due to uncertainties, it is not known what will happen in the future when certain actions are applied. This means that future states are not necessarily predictable.

2. Sensing: Due to uncertainties, the current state is not necessarily known. Information regarding the state is obtained from initial conditions, sensors, and the memory of previously applied actions.

These two kinds of uncertainty are independent in many ways. Each has a different effect on the planning problem.

Making a single decision

Chapter 9 provides an introduction to Part III by presenting ways to represent uncertainty in the process of making a single decision. The view taken in this chapter is that uncertainty can be modeled as interference from another decision maker. A special decision maker called nature will be introduced. The task is to make good decisions, in spite of actions applied by nature. Either worst-case or probabilistic models can be used to characterize nature's decision-making process. Some planning problems might involve multiple rational decision makers.