Identifying Barriers to Effective Subject Access in Library Catalogs

Lancaster, F. W., Connell, Tschera Harkness, Bishop, Nancy, McCowan, Sherry, Library Resources & Technical Services

Identifying Barriers to Effective Subject Access in Library Catalogs

The replacement of the card catalog by the online catalog brought with it a great resurgence of interest in the problems of subject access in general. This is hardly surprising in view of the fact that the online catalog promised to offer subject search capabilities that were substantially better than those offered by its predecessor.

Many studies on how to improve subject searching in online catalogs have already been performed. The approaches most frequently investigated can be grouped into five broad categories:

1. Those that rely on improved or more

flexible approaches to the searching of

elements (e.g., subject headings)

already commonly searched.

2. Those that extend search capabilities

to more elements in existing bibliographic

records.

3. Those that would enhance existing

bibliographic records by adding further

searchable elements.

4. Those that would make further

searching aids available to the library

user.

5. Those concerned with usefully limiting

the number of records retrieved in

simple search approaches (e.g., single

keyword in title) that would otherwise

cause an unacceptably large retrieval

from a database of any significant size.

Examples of the first group include studies involving improved word-stemming, techniques for the approximate matching of words (e.g., phonetic spelling), and the ability to perform keyword searches on subject headings (e.g., Walker,[1] Walker and Jones,[2] and Lester[3]). The second group, also exemplified by Lester,[4] looks at complete bibliographic records and determines how much retrieval would be improved were all fields equally searchable.

The third group recognizes that subject access might be improved considerably were existing bibliographic records enhanced by the addition of further access points taken, for example, from tables of contents or back-of-the-book indexes. This approach can be traced back some years (e.g., Atherton,[5] Wormell[6]. Recently, Byrne and Micco discovered, not surprisingly, that greatly improved recall could be obtained when MARC records in a database were enhanced by adding to each an average of twenty-one multiword terms drawn from indexes and tables of contents.[7] Using a somewhat different approach, Diodato confirmed that terms used by readers to described books do tend to match terms occurring in indexes and tables of contents.[8]

The fourth group of studies looks at the effect of making additional searching aids available to catalog users. Bates proposes two such tools that could be used in existing catalogs based on Library of Congress Subject Headings (LCSH) (an end-user thesaurus - basically a vast entry vocabulary - and a semantic network, incorporating the entry terms, that allows a searcher to select from a variety of methods for generating semantic associations), but she does not actually test them.[9] The most obvious searching aid would be a subject authority file, incorporating cross-references. Lester found that such an authority file had relatively little effect on the ability of catalog users to match their subject terms with LCSH headings, while Van Pulis and Ludy found that subject authority files are little used even when made available online.[10],[11] Jamieson et al. have compared the value of the authority control approach with the ability to perform keyword searches in complete bibliographic records.[12]

Many keyword searches in large online catalogs would be successful in the sense that they would retrieve relevant items. But they would also retrieve substantial numbers of irrelevant items, and would bring out so many records that the user would be discouraged from proceeding further. The fifth group of studies, exemplified by work now proceeding at the OCLC Online Computer Library Center, looks at ways in which such large retrievals can be successfully limited - by date, language, or other characteristics.

In addition to these studies, many others have looked at the possibility of building some form of user-friendly interface to allow a library user to perform a subject search without understanding search strategy or search logic, perhaps by entering a narrative statement of an information need. This approach is exemplified by the work of Salton and McGill,[13] Doszkocs,[14] Biswas et al.,[15] Clemencin,[16] and Pollitt,[17] among others.

Finally, one can identify studies that seek to apply artificial intelligence or expert system approaches to the library subject-access problem. For example, Micco et al. describe work designed to produce an expert system capable of searching for and providing access to knowledge at the same level as a skilled reference librarian.[18]

Limitations of Earlier Studies

It is encouraging to see so much activity in this important area, and the studies performed in the last several years have added significantly to out store of knowledge on the behavior of catalog users and the performance of the subject catalog in libraries.

In general, however, almost all of the studies suffer from the fact that they rely on rather crude or simplistic measures of searching success. This is a problem that has always bedeviled catalog-use studies (e.g., Lancaster[19],[20]). It is comparatively easy to evaluate a "known item" search in a library catalog: either a user finds the item or does not. A subject search cannot be evaluated on such a simple binary scale. Instead, one needs a measure of the degree of success of a search.

While excellent catalog-use studies have been performed in the past (e.g., Lipetz,[21] and Tagliacozzo and Kochen [22]), such studies have been weak in methodologies used for the evaluation of subject searches. The simplest approach (and the one still most commonly used - see Lester[23]) is to judge a search successful if the user is able to match subject terminology with the terminology of the catalog (examples) of this approach can be found in the work of Bates[24],[25]). Clearly, this is a crude measure of success, since it gives no indication of whether or not a user would find anything useful in this way, much less whether the most relevant items would be located.

In a somewhat more sophisticated approach, a subject search is judged successful if the catalog user selects one or more items (and presumably borrows them) as the result of a search. This is an improvement, certainly, but the evaluation criterion is still very unsatisfactory.

The quality of subject access in library catalogs cannot be improved from the results of studies based on such imperfect criteria. A subject search in the catalog of a library cannot be considered fully successful unless the user is able to locate the material that is, in some sense, the "best" i.e., the most complete, the most up-to-date, or the most authoritative. No previous studies of subject searching in library catalogs have used such a stringent criterion.

The study reported here used a series of simulations to determine the probability that a skilled catalog user would retrieve "the best" materials available in a library on some subject and, if they are unable to retrieve the best materials, to determine what changes would be needed to ensure that future catalogs would allow more successful subject searching (i.e., searching that produces more of the better materials).[26]

Methods

Fifty-one bibliographies representing …

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Publication information: Article title: Identifying Barriers to Effective Subject Access in Library Catalogs. Contributors: Lancaster, F. W. - Author, Connell, Tschera Harkness - Author, Bishop, Nancy - Author, McCowan, Sherry - Author. Journal title: Library Resources & Technical Services. Volume: 35. Issue: 4 Publication date: October 1991. Page number: 377+. © 1989 American Library Association. COPYRIGHT 1991 Gale Group.

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