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. A THESAURUS-I ½ 0½0 STEM o STEM ½ 0 A THESAURUS-I ½ PRECISION PRECISION 1.0 1.0 A A 0[OCRerr]A 0.8 \OA\A 0.E - [OCRerr]0[OCRerr]\A0 [OCRerr] [OCRerr]0[OCRerr]A 0.6 - ONA [OCRerr]0[OCRerr]O[OCRerr]\A OA - N0[OCRerr]A 0[OCRerr]A 0.2 - 0.2 - 0 I I I I I I I I `[OCRerr]RECALL 0 0.2 0.4 0.6 0.8 1.0 I I i I I - j I I a 0 0.2 0.4 0.6 0.8 1'0~~RECALL Comparison 18 Comparison 16 ADI, Abstracts, 35 Requests ADI, Full Text, 35 Requests Performance Curves Comparing Stem and Thesaurus Dictionaries on the ADI Abstracts and Test Collection Fig. 12