Redundancy and Uniqueness of Subject Access Points in Online Catalogs

Abstract

An analysis of 205 records selected at random from the OCLC Online Computer Library Center, Inc. Online Union Catalog showed considerable overlap (duplication) among the subject access points provided by the title, subject heading, and classification number fields. Little more than four unique (unduplicated) access points were found, on average, per record. While title and class number fields do add some access points not provided by subject headings, the increase is less than many librarians might have expected. It is suggested that the online catalog might outperform the card catalog more in precision than in recall.