Entry point depth and online search using a controlled vocabulary

The depth of indexing, the number of terms assigned on average to each document in a retrieval system as entry points, has a significant effect on the standard retrieval performance measures in modern commercial retrieval systems, just as it did in previous experimental work. Tests of the effect of basic index search, as opposed to controlled vocabulary search, in these real systems are quite different than traditional comparisons of free text searching with controlled vocabulary searching. In modern commercial systems the controlled vocabulary serves as a precision device, since the structure of the default for unqualified search terms in these systems requires that it do so. © 1989 John Wiley & Sons, Inc.