The model of agent systems is based on the constraint nets of Zhang and Mackworth [1995] and Rosenschein and Kaelbling [1995]. The hierarchical control is based on Albus [1981] and the subsumption architecture of Brooks [1986]. Turtle Geometry, by Abelson and DiSessa [1981], investigates mathematics from the viewpoint of modeling simple reactive agents. Luenberger [1979] is a readable introduction to the classical theory of agents interacting with environments. Simon [1996] argues for the importance of hierarchical control. Kahneman [2011] provides compelling evidence for distinguishing two modes of human thought: fast, instinctive and emotional, versus slow, deliberate and rational, which he calls Systems 1 and 2 to avoid oversimplification.

For more detail on agent control see Dean and Wellman [1991], Latombe [1991], and Agre [1995]. The methodology for building intelligent agents is discussed by Haugeland [1985], Brooks [1991], Kirsh [1991b], and Mackworth [1993].

Qualitative reasoning is described by Forbus [1996] and Kuipers [2001]. Weld and de Kleer [1990] contains many seminal papers on qualitative reasoning. See also Weld [1992] and related discussion in the same issue. For a more recent review see J. [2006].