On the behavior-based architectures of autonomous agency

A number of autonomous robots with varying degrees of reactive functionality have been built, based on different architectures. We review the foundations, limitations, and achievements of a number of architectures of such autonomous agents from the three categories: (1) reactive; (2) deliberative; and (3) hybrid. Most of these architectures contain behaviors. The principle of avoiding an explicit representation of goals in the purely behavior-based robots has limited their achievements to simple tasks like box pushing, pipe inspection, and navigation. This paper makes two contributions: (1) reviewing autonomous agent architectures and (2) proposing a new class of architectures where behaviors are coupled and/or markers are introduced in environment, without a planner or sequencer and without an explicit representation of goals and investigating tradeoffs in these architectures. We develop a model of behaviors, environmental modification and goals and then show how the behavior-based robots can be made goal-directed. The tradeoffs in increasing their goal directedness are examined. Defining the notion of coupling that captures dependency within the internal structure of a behavior space, it is shown that more complex goals demand higher coupling or more behaviors or a modification to the environment. These novel tradeoffs show a new spectrum of architectures for integrating goals and the behavior-based reactive functionality.