Textbook of AI

The subsumption architecture, introduced by Rodney Brooks in 1986, is a layered control architecture for robotics in which higher-level behaviours subsume (override) lower-level ones, with no central representation of the world or central reasoner. Each layer is a finite-state machine wired to specific sensors and actuators; the topmost layer that has a relevant input wins control. Layer 0 might handle obstacle avoidance; layer 1, wandering; layer 2, exploration; layer 3, mapping; each adding capability without disturbing lower layers.

Brooks's 1991 essay Intelligence Without Representation elaborated the philosophical claim: real-world intelligent behaviour is best produced by tightly coupling perception to action through specialised reactive systems, not by manipulating internal models. The slogan was that "the world is its own best model", robots should not maintain elaborate symbolic representations but sense the relevant features of the world directly when they need them.

Brooks's robots, Allen, Herbert, Genghis the six-legged walker, Cog the humanoid, demonstrated robust behaviour in cluttered real-world environments where contemporaneous symbolic-planning robots stalled. The behaviour-based tradition Brooks founded influenced an entire generation of robotics including iRobot's Roomba (which Brooks co-founded). Modern deep-learning robotics has moved back towards learned representations, but Brooks's emphasis on tight perception-action coupling and the "ghosts of representation" remains influential.