A knowledge-rich search uses some form of semantic or structured understanding of the problem space in order to improve the accureacy or speed of search. For example, if the problem space is a graph of direct road-travel times between cities, then a knowledege-rich serach might use the crow-flies distance between the cities as a heuristic to guide the search for a shortest path between two locations. In contrast a low-knowledge or knowledge-poor approach would just take the distances as path costs without taking into account their geographic nature.
Defined on page 77
Used on pages 77, 220, 339