Authority control is about consistency. It seeks to insure that the name, uniform title, and subject headings used on bibliographic records are unique, uniform, and correctly formulated. It accomplishes these tasks by distinguishing terms, identifying relationships between terms, formulating headings and references for these terms in accordance with established rules, and then documenting this work by creating authority records containing the authorized or "established" heading, any references, and supporting information. In addition to these intellectual activities, authority control also involves editing headings on existing bibliographic and authority records to achieve consistency. Authority control advances both the fmding and collocating functions of the catalog-the former by providing references from alternate forms of names and by introducing a degree of certainty into searches; the latter by bringing together under one heading all works associated with a given person, body, uniform title, or subject.l
Achieving the objectives of authority control is difficult even for current cataloging in a single library. Heading uniformity may suffer due to carelessness on the part of catalogers. Since topical subject headings are drawn from authorized lists, they at least should always be unique; but this is not necessarily the case with name headings. Name headings are based on actual usage, and, when the names of different persons or works are identical, uniqueness can only be achieved by adding a qualifying term. H such terms are unavailable, undifferentiated name headings must be tolerated.2 Formulating headings correctly means applying the proper rules, such as those found in the second edition of Anglo-American Cataloguing Rules (AACR2) or Le's Subject Cataloging Manual. Even where this is a requirement for new cataloging, catalog managers
may balk at refonnulating existing headings to bring them into compliance with current rules. ImpiementingAACR2 was especially challenging in this respect, since this code's rules for name and title headings vary greatly in principle and detail from those of earlier ones.3 Library of Congress Subject Headings (LCSH) has not experienced as drastic a transfonnation, but the ongoing addition, deletion, and replacement of individual subject headings and subdivisions necessitate a good deal of catalog maintenance. As costly as this maintenance may be, failing to update headings can have serious consequences for users, especially with regard to subject headings, since failing to follow current LC practice threatens the integrity of the catalog's syndetic structure.