1. in cognitive psychology, a set of parameters defining either a particular mental schema or the wider cognitive structure by which an individual perceives and evaluates the world. See also conceptual system; perceptual set.

2. in artificial intelligence, a knowledge representation scheme, much like an object system, used to represent and structure knowledge for a computational system. [first proposed in 1981 by U.S. mathematician and computer scientist Marvin Minsky (1927–  )]

3. in education, see programmed instruction; linear program.