postcoordinate indexing

(also called postcombination indexing), n. A method of indexing materials that creates separate entries for each concept in an item, allowing the item to be retrieved using any combination of those concepts in any order.


In postcoordinate indexing, complex subjects are represented by several different headings rather than a single heading. For example, a history of Arizona might be assigned the headings 'Arizona' and 'History'. In precoordinate indexing, the work might be given a single heading, 'Arizona - History'. Searching in a postcoordinate system typically relies on Boolean operators to combine the separate headings, such as "Search (subject = Arizona) and (subject = history)."


Lancaster 1998, p. 32 Postcoordinate systems emerged in the 1940s, when they were implemented through the use of various types of cards. A modern computer-based system, operated online, can be considered to be a direct descendant of those manual systems. Lancaster 1998, p. 44 The flexibility associated with postcoordinate systems is lost when index terms must be printed out on paper or on conventional catalog cards. Printed indexes and card catalogs are precoordinate; they have the following characteristics: 1. The multidimensionality of the term relationship is difficult to depict. 2. Terms can only be listed in a particular sequence, which implies that the first term is more important than the others. 3. It is not easy (if not completely impossible) to combine terms at the time a search is performed.