http://www2009.eprints.org/52/ Online Expansion of Rare Queries for Sponsored Search Sponsored search systems are tasked with matching queries to relevant advertisements. The current state-of-the-art matching algorithms expand the user’s query using a variety of external resources, such as Web search results. While these expansion-based algorithms are highly effective, they are largely inefficient and cannot be applied in real-time. In practice, such algorithms are applied offline to popular queries, with the results of the expensive operations cached for fast access at query time. In this paper, we describe an efficient and effective approach for matching ads against rare queries that were not processed offline. The approach builds an expanded query representation by leveraging offline processing done for related popular queries. Our experimental results show that our approach significantly improves the effectiveness of advertising on rare queries with only a negligible increase in computational cost. Broder, Andrei Ciccolo, Peter Gabrilovich, Evgeniy Josifovski, Vanja Metzler, Donald Riedel, Lance Yuan, Jeffrey Online Expansion of Rare Queries for Sponsored Search 2009-04-06T19:09:56Z Broder, Andrei <http://www2009.eprints.org/view/author/Broder=3AAndrei=3A=3A.html> and Ciccolo, Peter <http://www2009.eprints.org/view/author/Ciccolo=3APeter=3A=3A.html> and Gabrilovich, Evgeniy <http://www2009.eprints.org/view/author/Gabrilovich=3AEvgeniy=3A=3A.html> and Josifovski, Vanja <http://www2009.eprints.org/view/author/Josifovski=3AVanja=3A=3A.html> and Metzler, Donald <http://www2009.eprints.org/view/author/Metzler=3ADonald=3A=3A.html> and Riedel, Lance <http://www2009.eprints.org/view/author/Riedel=3ALance=3A=3A.html> and Yuan, Jeffrey <http://www2009.eprints.org/view/author/Yuan=3AJeffrey=3A=3A.html> (2009) Online Expansion of Rare Queries for Sponsored Search. In: 18th International World Wide Web Conference, April 20th-24th, 2009, Madrid, Spain. application/pdf application/pdf