HITS and Misses: Combining BM25 with HITS for Expert Search

This paper describes the participation of Dublin City University in the CriES (Cross-Lingual Expert Search) pilot challenge. To realize expert search, we combine traditional information retrieval (IR) using the BM25 model with reranking of results using the HITS algorithm. The experiments were performed on two indexes, one containing all questions and one containing all answers. Two runs were submitted. The first one contains the combination of results from IR on the questions with authority values from HITS; the second contains the reranked results from IR on answers with authority values. To investigate the impact of multilinguality, additional experiments were conducted on the English topic subset and on all topics translated into English with Google Translate. The overall performance is moderate and leaves much room for improvement. However, reranking results with authority values from HITS typically improved results and more than doubled the number of relevant and retrieved results and precision at 10 documents in many experiments.