IRS13 Search Matching Functions chapter E. M. Keen Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. 111-7 Figure 2 also gives the postings of the nine Mesh terms used in the search formulation plus two more terms from the request not used in the search for- mulation. Assuming that the search formulation included all the terms likely to be connected with the requestort 5 need, it can be seen that, ignoring the logical combinations asked for in the search formulation, 8,ooo to 10,000 documents in the file are associated with the search term chosen, or, `i[OCRerr]re simply still, regarding `tCerbrospinal fluid11 as an essential notion, 1162 associated items are in the file. The user' 5 second need would almost certainly be satisfied by some of these 1162 items, but it might have been possible to have satisfied both the user's first and second needs in a single search in the following manner: with `tcerbrospinal f1[OCRerr]id1' identified as a key notion, all the ll62 documents posted with that term would be retrieved, and would then be presented to the user in some `1ranked'1 order of probable relevance. A satisfactory result for this process would be obtained if the U references found in the Medlars search were to appear at the front of this ranked list (the user identified 10 of these ll as relevant). [OCRerr]f such a system could be provided, the user' 5 second need could have been satisfied merely by an examination of more than the first 11 documents in the search output. A second example of problems of this type lies at the opposite extreme: a request on the effects of drugs and pesticides on the bone marrow of man and animals resulted in 1,235 retrieved documents. Since the set almost certainly contains too many items, a ranked output would again provide a solution, allowing the requestor to examine only as many documents as he desired. Searches in Medlars are frequently made in three matching strengths in an attempt to meet this latter problem.