Situated Agents Can Have Plans

Abstract

Much of our everyday activity is not made up of solving isolated problems with single clear-cut goals, but rather dedicated to the ongoing maintenance of many goals or policies such as eating when hungry and maintaining a comfortable personal space. Furthermore, in many complex, dynamic worlds, an agent must maintain many goals at the same time and be able to act quickly and flexibly, because some decisions are time critical and the world is not perfectly predictable. The domain of SimCity requires this kind of behavior. In the simulation, you are never finished repairing the roads or fighting crime, because disasters and evolution will always require more work in the future. Survival depends on deciding what you should work on now, and by what you will allow yourself to be interrupted. In short, playing SimCity requires a robust theory of attention. Situated agents are built to address problems of timely activity in complex, dynamic worlds. (Maes) Such systems stress that competent behavior can arise out of continually selecting primitive actions based on information about the environment. Situated activity theories propose that resource conflicts can be avoided by noticing conflicts at compile time. Most situated agents, however, are not required to accomplish long-term activities such as building an industrial complex. Memory-based planning (Hammond), on the other hand, contends that in some interesting worlds an episodic memory of plans can adequately cover the longer-term problems an agent will face, thus providing an alternative to the intractability of exhaustive search. How do we arbitrate between memory-based, long-term behavior, and reactive, short-term maintenance? The Problem of Interruption in SimCity Imagine that in response to the problem of unemployment in the city, you decide to build an industrial park on the outskirts of town. You develop a plan for this, and you have the funds to execute it. Such a project could take three simulator months, but during the execution of this plan, an earthquake strikes. If you continue to carry out your plan, half the city may be destroyed by fires. Since you can only do one thing at a time, you must interrupt your industrial development plan and deal with the earthquake.