The chapter begins with a general introduction to integrative architectures that review their various components; this discussion is couched in terms of a stage model of information processing. Next we review 10 such architectures, describing the purpose, assumptions, architecture and functionality, operation, current implementation, support environment, validation, and applicability of each. The following section compares these architectures across a number of dimensions. This is followed by a brief discussion of hybrid architectures as a possible research path. The final section presents conclusions and goals in the area of integrative architectures.

A general assumption underlying most if not all of the integrative architectures and tools reviewed in this chapter is that the human can be viewed as an information processor, or an information input/output system. In particular, most of the models examined are specific instantiations of a modified stage model of human information processing. The modified stage model is based on the classic stage model of human information processing (e.g., Broadbent, 1958). The example given here is adapted from Wickens (1992:17). Such a stage model is by no means the only representation of human information processing as a whole, but it is satisfactory for our purposes of introducing the major elements of the architectures to be discussed.

In the modified stage model, sensing and perception models transform representations of external stimulus energy into internal representations that can be operated on by cognitive processes (see Figure 3.1).

Memory consists of two components. Working memory holds information temporarily for cognitive processing (see below). Long-term memory is the functional component responsible for holding large amounts of information for long periods of time. (See also Chapter 5.)

Cognition encompasses a wide range of information processing functions. Situation awareness refers to the modeled individual combatant's state of knowledge about the environment, including such aspects as terrain, the combatant's own position, the position and status of friendly and hostile forces, and so on (see also Chapter 7). Situation assessment is the process of achieving that state of knowledge. A mental model is the representation in short- and long-term memory of information obtained from the environment. Multitasking models the process of managing multiple, concurrent tasks (see also Chapter 4). Learning models the process of altering knowledge, factual or procedural (see also Chapter 5). Decision making models the process of generating and selecting alternatives (see also Chapter 6).

Motor behavior, broadly speaking, models the functions performed by the neuromuscular system to carry out the physical actions selected by the above-mentioned processes. Planning, decision making, and other "invisible" cognitive