Passage Retrieval with Vector Space and Query-Level Aspect Models

This report describes the joint work by Kyoto University and the University of Melbourne for the TREC Genomics Track in 2007. As with 2006, the task for this year was the retrieval of passages from a biomedical document collection. The overall framework of our system from 2006 remains unchanged and is comprised of two parts: a paragraph-level retrieval system and a passage extraction system. These two systems are based on the vector space model and a probabilistic word-based aspect model, respectively. This year, we have adopted numerous changes to our 2007 system which we believe corrected some problems.