RETRIEVAL TECHNIQUES.

This paper reviews the literature on research in retrieval techniques for information retrieval systems, from about 1980 to date, within the framework of an original classification of retrieval techniques. By retrieval techniques it is meant that the comparison of representations of queries of problems with representations of texts, for the purpose of identifying, retrieving, and/or ranking texts that might be relevant to a query or problem. The review stresses the contradictions between operational and experimental techniques, considers the issues of tailoring techniques to queries and using multiple techniques for single queries, and discusses the place of retrieval techniques in expert information systems and integrated information systems. The authors conclude with suggestions from research in retrieval techniques.