Creation of Bibliographic Search Codes for Hash‐addressing using the Variety‐generator Method

The application of the variety‐generation technique to the construction of truncated author‐title search keys for data bases of monograph records is described. Instead of the usual fixed‐length keys (e.g. three characters of the author's surname, and the first three filing characters of the title) the method uses strings of characters which vary in length according to the statistical characteristics of author names and titles in BNB MARC files. The number of these strings is variable within wide limits. By choice of appropriate sets of keys, bibliographic search codes with a higher resolving power than the 3,3 key can be produced. The codes also show favourable distributions for direct construction of hash addresses.