iv-66

         subbranches;

     3)  if all words in a given word group are bei~ng placed in the same
         branch with the high-frequency word, this word belongs one level
         up as a parent of all the remaining words.


     Consider again the vocabulary of Fig. 19.    The highest frequency word

is  computer11 (frequency 508), and two classes are first formed of words

like ttcomputer1, and of the 1other'1 words (see Fig. 21).  The high frequency

class is the one containing the term 1tcomputer11, so that it is subdivided

again using the word `Tcomputer't as a criterion.  This produces  two

classes consisting respectively of 1computer, program, digital, memory'

and "~ystem, circuit, data'1; the term "machine" which is generic to the

whole class is left on the second level.   The ori~inal "other'1 category can

also be subdivided, using the included high-frequency word "operate" as a

guide, and producing the complete hierarchy shown in Fig. 21.

     A comparison of the hierarchies of Figs. 20 and 21 reveals that the

word groups produced by the thesaurus question method of Fig. 20 may be

more reasonable; however, the frequency procedure is more systematic and

may conceivably be easier to apply.

     The last hierarchy formation process is also based on a term-do~ment

or a term-property matrix.   In this case, however, the process of forming

the hierarchy is completely automatic, even though the original property

matrix may have been constructed by hand.   Consider two arbitrary terms

identified by weighted property vectors.   The following conditions may

then obtain:


     1)  terms A and B are identified by different properties, and as
         such are not related;

     2)  terms A and B are identified by the same properties, and the