ISR11 Relevance Feedback in an Information Retrieval System chapter W. Riddle T. Horwitz R. Dietz Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. vi-i4 because the search time is not included in the investigation. The investigation indicates two specific areas where more research is possible. Of primary importance, since it is now known that negative weights are useful in the relevance feedback process, is a more specific investigation of negative relevance weighting factors using relevance judgments given by an actual user population. Also, the number of iterations needed to obtain the best possible recall and precision should be studied. In addition to its use in document retrieval, the relevance feedback process provides an efficient method for testing the efficiency of docu- ment indexing schemes, since external disturbances, such as incorrect formulations of queries, are minimized. Theoretically, one could possibly develop an indexing scheme which would eliminate the need to use relevance feedback information. However, the present investigation has shown how a rather simple use of relevance feedback information can greatly improve the recall achieved by the document retrieval system. Thus, it would seem more practical to use the best of the present indexing schemes, and direct further investigation to the area of retrieval improvement by the efficient and optimal empl[OCRerr]rment of user relevance feedback information.