Meta-knowledge and Cognition

In Al knowledge representation schemes, structures that describe other structure:: are said to represent "meta-knowledge." Knowledge about other knowledge can be either about the form of the representation scheme itself (e.g., its syntax) or about the "facts" that are represented (their origin, reliability, Importance, etc.). After reviewing the use of explicit meta-knowledge In several systems, some studies of human behavior that Indicate people's ability to reason about what they know and about how they reason are described. The concept of meta-level knowledge captures intrinsic, commonplace properties of human cognition that are central to an understanding of memory and Intelligence. The use of meta-knowledge In Al systems like MYCIN, which have reached humanexpert-level performance In complex domains, Is a key breakthrough In the design of "knowledge-based" Intelligent systems. Meta-level knowledge has been used in these systems primarily in the implementation of "introspective" processes: Acquisition of new knowledge and explanation of the system's reasoning to users. The usefulness of meta-level descriptions for these and other functions has prompted proposals for their incorporation in several new general-purpose representation schemes, like KRL, as described In the next section.