chapter  3
Pages 30

The term schema has been used in the psychological and AI literature to mean many different things; in fact, the term has been used so widely and variously that Alba and Hasher (1983) have noted that it has no fixed definition, but rather is used to refer to any organized collection of information used for encoding, storing, and retrieving knowledge. For our purposes, a schema is defined as follows:

Definition 3.1: A schema is an explicit, declarativelyrepresented packet of knowled~e representing either a pattern encountered (or expected) in the world or a pattern of action for the reasoner to take. A schema can be either provided to a reasoner by another agent or learned from experience.