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. v'-13 ieedback process is studied in detail, the validity of this assumption is demonstrated repeatedly; for practically every query tested, the recall is eventually increased. The explicit assumption basic to this investigation is that the relevance feedback and query modification proccesses can be optimized in some sense. Although the analysis demonstrates that no uniformly best process exists, the investigation of the relevance weighting factors, the search correlation function, and the iteration strategy shows that same combinations of these parameters produce methods that work well in many cases. Specifically, the follo[OCRerr]ng choices of the parameters constitute an optimal system since[OCRerr]each optimizes that part of the modification process which it affects most directly. First, the sL[OCRerr]le vector matching correlation function is optimal in that it retrieves more relevant documents on the initial search than do either the cosine or co-occurrence correlation functions. Second, the iteration strategy in which [OCRerr] is increased `[OCRerr]th every iteration is optimal in the sense that the scale of the query updating information is effectively equal to the scale of the current query. Finally, the use of zero and one as relevance weighting factors, including the negative relevance weighting factor heuristic method, is optimal in the sense that it adequately describes the feedback information provi[OCRerr]ded by the user. Therefore, this combination of parameters yields a retrieval system which is optimized for high precision and recall through the use of relevance feedback information. Of course, it can be argued that some of these choices for the parameters may lead to inefficiencies in the retrieval process, but this objection is of no consequence in this investigation