PRIS at TREC 2013 Microblog Track.

This paper described the real-time search system we built for TREC 2013 microblog track. We focused on query expansion and ranking algorithm and employed different strategies. For query expansion, we implied pseudo-relevance feedback using WAF algorithms and a refined tf ∗ idf formula. For re-ranking part, our system makes use of various tweets’ features, such as expansion terms, URL information, and incorporate them in a learning–to-rank framework to improve the final ranking results.