A knowledge base is a form of database where the facts and rules of captured knowledge are stored. This might be network-based, frames or soem form of formal logic. As well as storage, the knowledge base needs suitable organisation and indexing to support reasoning.
Used on Chap. 2: pages 17, 22, 28, 31, 33; Chap. 6: page 122; Chap. 16: page 380; Chap. 18: page 431