ISR11 Table of Contents table of contents Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. TABLE OF CONTENTS (continued) [OCRerr]ge SECTION VII LESSER, V. R.: :!A Modified Two-Level Search Algorithm Using Request Clusteringt' 1. Introduction VII-l 2. A Modified Clustering Algorithm and a Corresponding Two-Level Search Strategy v'I-3 3. Advantages of the [OCRerr]ery Clustering System [OCRerr]. Design of an Experiment to Compare the Modified with the Normal Two-Level Search Scheme VII-5 VII-7 A) Problem Areas v'I-7 B) Tests.to Compare the Effectiveness of Each Search Procedure . v'I-7 C) Implementation of the Normal and Modified Two-Level Search Schemes v'I-9 D) Test Data Base VII-12 5. Actual Comparisons of the Modified versus the Normal Two-Level Searches . . v'I-13 A) Data Generated for Two-Level Search Algorithm . . . . v'I-13 B) Data Generated for Modified Two-Level Search Algorithm . . . VII-l[OCRerr] C) Experimental Evaluation v'I-16 D) Evaluation Results VII-25 6. A New Criterion for Search Effectiveness v'I-27 7. Conclusions . . . . . . VII-28 Appendix A VII- 30 x