MONO91 Automatic Indexing chapter Mary Elizabeth Stevens National Bureau of Standards (6) Appraisal of the current prospects for further research and development. Certain difficulties of organization are evident. Thus many proposals precede actual tests of techniques to which they are akin. Other proposals have been engendered as by- products of or incidental to investigations of other techniques, such as those of text pro- cessingto derive by machine selected sentences which together may serve as automati- cally generated "abstracts", more properly extracts. 1/ This related subject of automatic abstracting, i.e., the application of machine- usable rules to the extraction or generation of textual information representing in con- densed form that carried in the document as a whole, will not be of primary concern. However, it will be noted that most of the automatic abstracting techniques so far pro- posed are potentially usable as tools for automatic indexing, especially in the trivial sense that the automatic selection of index terms co[OCRerr][OCRerr]d be based solely upon the substan- tive words found in the machine-prepared extract. - Further, since we are presuming that a state-of-the-art review of automatic indexing techniques is in some sense appro- priate at this time, we shall emphasize the actual results of machine compilation and machine generation of indexes and those investigations of assignment-indexing techniques for which experimental or comparative data have been reported, rather than theoretical approaches. 1/ See, for example, Luhn, 1959 [384], p. 4: "The principle of abstracting in- formation by extracting certain portions or elements from the full text of a document is particularly suitable to mechanization"; Becker, 1960 [44], p. 13: "Perhaps `extracting' would have been a better word than `abstracting'"; Edmundson and Wyllys, 1961, [181], p. 227: "All proposed methods for making an automatic abstract of a document involve using the author's own words by selecting complete sentences, thereby reducing abstraction to the simple task of extraction." 2/ See Wyllys, 1963 [653 A1 p 22: "Automatic indexing is an area that seems to us to be especially close to automatic abstracting, since the words and word groups found to be most representative of a document for automatic abstracting purposes are obvious candidates for entries in an automatic index for the documents." See also Tanimoto, 1961 [594 3] , p. 235: "Thus after ex- tracting k sentences which are a predetermined small fraction of the document, we have an `abstract'. To find the indexes to the document we take these k sentences and the corresponding sets of the canonical elements and consider terms versus sentences instead of sentences versus terms. . . The same analysis is then applied to this `transposed' problem to produce the index terms"; Yakushin, 1963 [654], p.17: "If some method can be employed for the automatic compilation of abstracts, it can as well be used for the subject index." 12