IXE at the TREC 2005 TeraByte task

The TREC Terabyte task provides an opportunity to analyze scalability issues in document retrieval systems. I describe how to overcome some of these issues and in particular improvements to the IXE search engine in order to achieve higher precision while maintaining good retrieval performance. A new algorithm has been introduced to handle OR queries efficiently. A proximity factor is also computed and added to the relevance score obtained by the PL2 document weighting model: several experiments have been performed to tune its parameters. By tuning also other parameters used in relevance ranking, IXE achieved second best overall P@10 score, combined with the fastest reported retrieval speed