A PROBABILISTIC SEARCH STRATEGY FORMEDLARS

One technique for searching a Co‐ordinate Index is to compare each reference with a Boolean expression of index terms. This divides the file into retrieved and not‐retrieved references. An alternative is to assign each reference a score calculated from its index terms and to retrieve the N highest scoring references in the file. This scoring technique has several advantages in theory, and it performed slightly better in a retrieval test with N equal to the number of references retrieved by the corresponding Boolean search. In the test a minimum value of N = 10 was used, and when less than this number of references matched the Boolean search requirement, the Scoring technique successfully widened the scope of the search and retrieved twice as many relevant references as the Boolean searches.