An Information-Theoretic Approach to Text Searching in Direct Access Systems Using direct access computer files of bibliographic information, an attempt is made to overcome one of the problems often associated with information retrieval, namely, the maintenance and use of large dictionaries, the greater part of which is used only infrequently. A novel method is presented, which maps the hyperbolic frequency distribution. This is more suited to implementation on storage devices. This method treats text as a string of characters rather than words bounded by spaces, and chooses subsets of strings such that their frequencies of occurrence are more even than those of word types. The members of this subset are then used as index keys for retrieval. The rectangular distribution of key frequencies results in a much simplified file organization and promises considerable cost advantages. CACM June, 1974 Barton, I. J. Creasey, S. E. Lynch, M. F. Snell, M. J. text searching, information theory, file organization, direct access, information retrieval, character string, bit vector 3.42 3.70 3.73 3.74 5.6 CA740615 JB January 17, 1978 2:07 PM 2532 4 2631 2631 4 2631 2631 4 2631 2746 4 2631 3001 4 2631 2139 5 2631 2532 5 2631 2631 5 2631 2631 5 2631 2631 5 2631