Classification experts and librarians have long recognized the potential of library classification schemes for improving subject access to information. In a 1983 article, Svenonius describes several uses for classification in online retrieval systems, including the following, (1) to improve precision or recall, (2) to provide context for search terms, (3) to enable browsing, and (4) to serve as a mechanism for switching between languages. In the Dewey Decimal Classification (DDC) Online Project (Markey and Demeyer 1986), Markey demonstrated the first implementation of a library classification scheme for end-user subject access, browsing, and display. Although many online catalogs provide call number browsing, few employ classification in the manner described by Svenonius or explored by Markey in her innovative use of the DDC in an experimental online catalog which enabled users to search and browse online classification data. Only recently, some ten years after Markey's pioneering research, is online classification data once again being seriously viewed as a tool for providing advanced browsing and retrieval capabilities in online systems.