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. vill-lo are connected by a parent-son relation. The resulting hierarchy is: II[OCRerr] [OCRerr]\\\\\ [OCRerr]1 In a similar fashion the hierarchy for number 3 is constructed: I [OCRerr]` [OCRerr] The curved, dotted lines denote `1grandfather-grandson" relations, which are parent-son relations spanning one or more other levels. Such relations complicate the level structure and obscure ordinary parent-son and brother-brother relations. The authors recommend that grandfather- grandson relations be deleted from each composite hierarchy. For the same reasons, brother-brother relations between concepts on different levels should be deleted. The composite hierarchies are used as follows. Suppose that the concept numbers represent these concepts: T1 library T2 dictionary T3 information