Integrating Logical Operators in Query Expansion in Vector Space Model

Query expansion is an effective way to extend the coverage of retrieval to the related documents. Various approaches have been proposed and many of them are based o vector space model. The expansion process consists of simply adding expansion terms into the original vector. In this paper we argue that this simplistic expansion method can bias the focus of the original query, because the expanded terms add additional emphasis to the original term. Instead of adding expansion terms into the vector, we propose to combine them with the original terms by means of a logical OR operator. In this way, the expansion terms are considered as alternatives to the original terms, and the focus of the whole query remain the unchanged. Our experiments on a REC collection show that this expansion approach is more effective than simple addition approach.