ISR11 An Experimental Investigation of Automatic Hierarchy Generation chapter G. Blomgren A. Goodman L. Kelly Harvard University Gerard Salton Use, reproduction, or publication, in whole or in part, is permitted for any purpose of the United States Government. VIII-13 relations do occur, as illustrated by sample outputs in Appendix A. These outputs are presented in descending order of cutoff value. Although it is possible to examine the ordinary hierarchies and identify the various ranges for each pair of concepts in the actual term- term matrix, a set of composite hierarchies is not constructed. The authors believe that composite hierarchies shor':ild be constructed by examining the relations between each pair of concepts as K varies from o to 1 (method b) on page 8); this approach is more direct and requires less time and less memory in the computer. To do this, a composite- hierarchy generating program must be written. The usefulness of composite hierarchies is best evaluated in actual information-retrieval system. In any event the composite hierarchies must be constructed for the entire set of concepts. Then standard evaluation procedures may be used to compare system performance with composite hierarchies to system performance without them.