IRS13 Thesaurus, Phrase and Hierarchy Dictionaries 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. Stem(s) versus Thesaurus(t) Input, Matching Function Precision at Recall Normalized No. Collection and Thesaurus Type .2 .5 .8 Rec. Pre. 3 Title, Cosine Numeric, Thes-2 T T T T 4 IRE-3 Title, Cosine Numeric, Thes-3 T []T T [[OCRerr]j 5 34 Abstract, Cosine Logical, r£hes[OCRerr]3 T T T T T 6 Requests Abstract, Overlap Logical, Thes-2 S S T T S 7 Abstract, Overlap Logical, Thes-3 T T T T T 11 Cran-l Title, Cosine Numeric, Thes-3 S S flT T T 14 42 Abstract, Cosine Logical, Thes-3 T flT T []T 15 Requests Abstract, Overlap Logical, Thes-3 T T T 17 Text, Cosine Numeric, Thes-SAl S S S 19 Abstract, Cosine Numeric, Thes-SAl S S S S S The difference of one dictionary merit over the other is smaller than 0.05 alone appears, and larger than 0.05 when letters [OCRerr]re circled. when a letter Table Summarizing 18 Precision Versus Recall Plots not Presented, Comparing Stem and Thesaurus Dictionaries on Three Collections. Fig. 17