Abstract
Engineering Information, Inc. recently developed a thesaurus for use in indexing its databases. The concepts in the former, highly precoordinate, indexing vocabulary were converted into postcoordinate descriptors, and a full set of thesaurus relationships developed. Issues to be resolved in developing the vocabulary included the degree of postcoordination that was appropriate, the need to make the thesaurus usable with retrospective indexing that could not be converted, and the demands on in-house staff during the development and conversion process.