How much do subject headings help keyword searches? : the effect of Library of Congress Subject Headings on keyword relevance search results in the National Library of New Zealand's National Bibliographic Database :

Abstract

The popularity of Internet search engines means library users are increasingly using keyword searches to seek items through web-based online public access catalogues (OPACs). Previous studies have found that library users find subject searching in OPACs difficult. It is important for libraries to explore ways to improve subject access through OPACs in light of continuing technological developments. This research project aims to assess the usefulness of Library of Congress Subject Headings (LCSH) when National Library of New Zealand National Bibliographic Database (NBD) users carry out keyword relevance searches to seek information on a particular subject area. In theory, the addition of LCSH to a catalogue should increase the number of relevant records retrieved, since the subject headings provide more access points for document retrieval and control synonyms and homographs. To evaluate the theoretical benefits, this study used real search terms drawn from the transaction logs of searches conducted by NBD users. Their searches were then replicated by the author and the retrieved records examined to assess to what extent LCSH helps improve subject access. The findings indicate that LCSH helps users find relevant records in NBD, but its effects are inconsistent, thus limited. Possible improvements to the subject access mechanism of NBD OPAC are suggested, including automatic truncation of search terms and online thesaurus based on LCSH authority records.