The Knowledge Level

As the first AAAI Presidential Address, this paper focuses on a basic substantive problem: the nature of knowledge and representation. There are ample indications that artificial intelligence is in need of substantial work in this area, e.g., a recent SIGART special issue on Knowledge Representation edited by Ron Brachman and Brian Smith. The paper proposes a theory of the nature of knowledge, namely, that there is another computer system level immediately above the symbol (or program) level. The nature of computer system levels is reviewed, the new level proposed, and its definition is treated in detail. Knowledge itself is the processing medium at this level and the principle of rationality plays a central role. Some consequences of the existence of the knowledge level and some relations to other fields are discusse