"In 2006, the Director for Acquisitions and Bibliographic Access (ABA) at the Library of Congress (LC) requested the Cataloging Policy and Support Office to review the pros and cons of pre- versus post-coordination of Library of Congress Subject Headings (LCSH). The final report recommended, and the ABA Management accepted, that LC catalogers continue to apply pre-coordination of LCSH terms.
Unsolicited comments were received from Lois Chan, Arlene Taylor, and Danny Joudrey, who are all professors of cataloging. They wrote to support the continuation of LCSH and spoke to the benefits of pre-coordination. The benefits include precision of searching, improved browsability, disambiguation of concepts, and suggestibility. By having pre-coordinated strings, users can infer context of the concepts, and the terms can be parsed by machines to take advantage of post-coordinated searching when that is desirable – getting the best of both worlds in a sense. In combination with complementary vocabularies from social tagging, a user can be led to the structured, controlled vocabulary to improve recall and precision of searching.
The LC report documents the recommendations approved in June 2007, regarding further automation of the assignment of subject heading strings, the expansion of machine validation of strings, further simplification of practices including the fixed order of subdivisions, exploration into LC’s use of the current generation of sophisticated search engines, the enabling of more social tagging additions to the LC records, and encouragement of Web applications that take advantage of LCSH. On this latter point, LC intends to make LCSH freely available on the Web in a SKOS (Simple Knowledge Organization Schema) format for the world at large. "
Read more and link to report at: http://www.loc.gov/catdir/cpso/pre_vs_post.html