Studying Query Expansion Effectiveness

Query expansion is an effective technique in improving the retrieval performance for ad-hoc retrieval. However, query expansion can also fail, leading to a degradation of the retrieval performance. In this paper, we aim to provide a better understanding of query expansion by an empirical study on what factors can affect query expansion, and how these factors affect query expansion. We examine how the quality of the query, measured by the first-pass retrieval performance, is related to the effectiveness of query expansion. Our experimental results only show a moderate relation between them, indicating that the first-pass retrieval has only a moderate impact on the effectiveness of query expansion. Our results also show that the feedback documents should not only be relevant, but should also have a dedicated interest in the topic.