< information science > An information resource that contains references to other resources, categorised by subject, usually in a hierarchy .
Yahoo is the most popular Internet subject index. Like most other subject indices , Yahoo is arranged ontologically .
Subject indices are not to be confused with search engines , which are based not on subject, but instead on relevance , although (1) this difference is often (possibly rightly) hidden from the unsophisticated user, and (2) future integration of knowledge representation into relevance ranking algorithms will make this a hazy distinction.
(1997-04-09)