DCU at CLEF 2006: Robust cross language track

The main focus of the DCU group’s participation in the CLEF 2006 Robust Track in CLEF 2006 was not to identify and handle difficult topics in the topic set per se, but rather to explore a new method of re-ranking a retrieved document set. The initial query is used to re-rank documents retrieved using a query expansion method. The intention is to ensure that the query drift that might occur as a result of the addition of expansion terms chosen from irrelevant documents in pseudo relevance feedback (PRF) is minimised. By re-ranking using the initial query, the relevant set is forced to mimic the initial query more closely while not removing the benefits of PRF. Our results show that although our PRF is consistently effective for this task, the application of our re-ranking method generally has little effect on the ranked output