Effective query expansion for federated search

While query expansion techniques have been shown to improve retrieval performance in a centralized setting, they have not been well studied in a federated setting. In this paper, we consider how query expansion may be adapted to federated environments and propose several new methods: where focused expansions are used in a selective fashion to produce specific queries for each source (or a set of sources). On a number of different testbeds, we show that focused query expansion can significantly outperform the previously proposed global expansion method, and - -contrary to earlier work - -show that query expansion can improve performance over standard federated retrieval. These findings motivate further research examining the different methods for query expansion, and other forms of system and user interaction, in order to continue improving the performance of interactive federated search systems.