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. vill-il Input and Type Evaluation Stem Thesaurus No. Collection of Thesaurus Measure Dictionary Dictionary 1 Abstract Normed. Recall .8954 .9191 (Thesaurus-2) Normed. Precision .6746 .7072 2 IRE-3 Abstract Normed. Recall .8954 .9268 (Thesaurus-3) Normed. Precision .6746 .7382 34 3 Title Normed. Recall .8145 .8436 Requests (Thesaurus-2) Normed. Precision .5547 .5945 4 Title Normed. Recall .8145 .8430 (Thesaurus-3) Normed. Precision .5547 .6068 8 Abstract Normed. Recall .8644 .8602 (Thesaurus-i) Normed. Precision .6704 .6319 9 Abstract Normed. Recall .8644 .8864 (Thesaurus-2) Normed. Precision .6704 .6864 Cran-1 10 Abstract Normed. Recall .8644 .8837 42 (Thesaurus-3) Normed. Precision .6704 .6952 Requests 11 Title Normed. Recall .8112 .8374 (Thesaurus-3) Normed. Precision .6185 .6420 12 Indexing Normed. Recall .8897 .8629 (Thesaurus-i) Normed. Precision .6831 .6335 13 Indexing Normed. Recall .8897 .8992 (Thesaurus-2) Normed. Precision .6831 .7094 16 Text Normed. Recall .7779 .8206 (Thesaurus-i) Normed. Precision .5573 .6273 17 Text Normed. Recall .7779 .7774 (Thesaurus-SAl) Normed. Precision .5573 .5441 18 ADI Abstract Normed. Recall .7601 .8016 35 (Thesaurus-i) Normed. Precision .5326 .6069 19 Requests Abstract Normed. Recall .7601 .7548 (Thesaurus-SAl) Normed. Precision .5326 .5190 20 Title Normed. Recall .6722 .7324 (Thesaurus-i) Normed. Precision .4537 .5462 21 Title Normed. Recall .6722 .6877 (Thesaurus-SAl) Normed. Precision .4537 .4649 Performance Results Comparing Stem and Thesaurus Dictionaries for Sixteen Results using Cosine Numeric on three Collections, and Normalized Recall and Precision Fig. 5