In the next several chapters we discuss the application of the methodology for representing knowledge about dynamic domains and ASP programming to the design of intelligent agents capable of acting in a changing environment. The design is based on the agent architecture from Section 1.1. In this chapter we address planning — one of the most important and well studied tasks that an intelligent agent should be able to perform (see step 3 of the agent loop from Section 1.1).

Classical Planning with a Given Horizon

We start with classical planning in which a typical problem is defined as follows:

1. • A goal is a set of fluent literals that the agent wants to become true.

2. • A plan for achieving a goal is a sequence of agent actions that takes the system from the current state to one that satisfies this goal.

3. • Problem: Given a description of a deterministic dynamic system, its current state, and a goal, find a plan to achieve this goal.

A sequence α of actions is called a solution to a classical planning problem if the problem's goal becomes true at the end of the execution of α.

In this chapter we show how to use ASP programming techniques to solve a special case of the classical planning problem in which the agent has a limit on the length of the allowed plans. The limit is often referred to as the horizon of the planning problem.