Central to the architecture is the ability to search its knowledge for sequences of actions (plans) in order to reach a given goal from the current state. Control knowledge is central to such architectures so the search space can be limited, and therefore the performance of such an architecture improves with the acquisition of new or improved control knowledge. Hence, such architectures tend to incorporate the ability to learn. The prototypical architecture of this type is Prodigy Icarus (P. Langly), which is centered around a specific organization of memory