Content area
The purpose of this study is to examine to what extent the classification number, title, and subject heading fields in catalog records overlap each other in providing subject access points (SAPs), to determine the unique SAPs existing in these fields, and to explore the relationship of the three subject-rich fields and four Dewey Decimal Classification classes--300s (Social Sciences), 500s (Natural Sciences and Mathematics), 600s (Technology (Applied Sciences)), and 700s (the Arts--Fine and Decorative Arts) at the "concept" or "subject idea" level.
205 sample bibliographic records, representing monographs in English and published in the period 1990-1994, were randomly drawn from the OCLC Online Union Catalog. Repeated measures designs were used to test whether there are significant differences in the average number of overlapping SAPs in classification number (CN) and title (TI) fields, CN and subject heading (SH) fields, and TI/SH; whether there are significant differences in the average number of unique SAPs provided by CN, TI, and SH or CN/TI, CN/SH, and TI/SH; which class areas have more overlapping or unique SAPs; and whether the distribution of overlapping or unique SAPs in three or every pair of fields depends on the four class areas.
It was found that, in typical catalog records, the average number of overlapping subject access points in CN/TI is significantly less than the overlapping SAPs in CN/SH and TI/SH fields; the average number of overlapping subject access points provided by each pair of fields is affected by class areas. The average number of unique subject access points is highest in the SH and lowest in the CN field; four class areas are significantly different with respect to the number of unique subject access points with most in the 300s Social Sciences and least in the 500s Natural Sciences; the mean distributions of unique subject access points provided by CN, TI, and SH, or CN/TI, or TI/SH are closely associated with class areas. In short, the SH field is the major source of subject access points and unique subject access points. However, adding subject ideas from CN and/or TI will in theory improve search retrievability although mainly in recall rather than precision.