Form subdivisions - Their identification and use in LCSH

Form subdivisions have always been an important part of the Library of Cong ress Subject Headings. However when the MARC format was developed, no separ ate subfield code to identify form subdivisions was defined. Form and topic al subdivisions were both included within a general subdivision category. I n 1995, the USMARC Advisory Group approved a proposal defining subfield $up silon for form subdivisions, and in 1999 the Library of Congress (LC) began identifying form subdivisions with the new code. However there are millions of older bibliographic records lacking the expli cit form subdivision coding. Identifying form subdivisions retrospectively is not a simple task. An algorithmic method was developed to identify form subdivisions coded as general subdivisions. The algorithm was used to ident ify 2,563 unique form subdivisions or combinations of form subdivisions in OCLC's WorldCat. The algorithm proved to be highly accurate with an error r ate estimated to be less than 0.1%. The observed usage of the form subdivis ions was highly skewed with the 100 most used form subdivisions or combinat ions of subdivisions accounting for 90% of the assignments.