This view is often expressed by saying that the the neurophysiological hardware of the brain implements a ``cognitive processor'', a simple symbol-manipulating machine, and that this is a production system. For a statement of this view, see Foundations of Cognitive Science edited by Posner (Springer-Verlag 1989; PSY BH:P 084), Chapter 3. For what Newell and Simon believed to be the eight main architectural features of the mind, see Computer Models of Mind by Boden (CUP 1988; PSY KD:B 063), page 164.
But there can be many different types of production system. Here's a list of some of the ways they could differ:
_for example, might match any set of symbols starting with and ending in . Can the conditions check how many of some symbol there are?
Different theorists have proposed different types of cognitive processor. The ways in which one differs from another: the complexity of its rules, the capacity of STM and so on, these define its functional architecture. In the same way, a VAX, a PC, and an Apple Mac are all computers, with the same general design. But the details of their functional architecture - the maximum size of number that can be stored, the memory capacity, and so on - are all different.