A comparison of two systems of weighted boolean retrieval

Abstract A major deficiency of traditional Boolean systems is their inability to represent the varying degrees to which a document may be written on a subject. In this article we isolate a number of criteria that should be met by any Boolean system generalized to have a weighting capability. It is proven that only one weighting rule satisfies these conditions—that associated with fuzzy‐set theory—and that this weighting scheme satisfies most of the other properties associated with Boolean algebra as well. Probabilistic weighting is then introduced as an alternative approach and the two systems compared. In the limit of zero/one weights, all systems considered converge to traditional Boolean retrieval.