the art of bringing the principles and tools of AI research to bear on difficult applications problems requiring experts' knowledge for their solutions. The technical issues of acquiring this knowledge, representing it and using it appropriately to construct and explain lines of reasoning are important problems in the design of knowledge-based systems. The art of constructing intelligent agents is both part of and an extension of the programming art. It is the art of builidng complex computer programs that represent and reason with knowledge of the world.

from Feigenbaum, E., and P. McCorduck. (1983). The Fifth Generation. Reading, MA: Addison-Wesley.