Boolean interpretation of conjunctions for document retrieval

It is generally recognized that the conjunction “and” plays an ambiguous role in natural language. When considered within the domain of Boolean document retrieval, this ambiguity makes the automatic Boolean interpretation of statements representing information needs a difficult task. The human analyst is able to resolve this ambiguity with relative ease. However, the processes employed appear complex and are not well understood. This article examines a semantic property of the conjunction, i.e., the semantic similarity between the conjuncts with a view to automatically resolving this ambiguity. Specifically, the idea examined is that if the two conjuncts are semantically similar then the conjunction is best interpreted as a Boolean OR, otherwise as an AND. The study resulted in an algorithm which utilizes semantic information and some syntactic information (both of which are derivable from a standard dictionary) to obtain the appropriate Boolean interpretation. The algorithm was successful when evaluated against human decisions. In addition to contributing the algorithm, this article draws attention to the effects of this ambiguity on the derivation of appropriate Boolean search specifications from natural‐language statements representing information needs. © 1987 John Wiley & Sons, Inc.