Japanese Probabilistic Information Retrieval Using Location and Category   Information
  Robertson's 2-poisson information retrieve model does not use location and category information. We constructed a framework using location and category information in a 2-poisson model. We submitted two systems based on this framework to the IREX contest, Japanese language information retrieval contest held in Japan in 1999. For precision in the A-judgement measure they scored 0.4926 and 0.4827, the highest values among the 15 teams and 22 systems that participated in the IREX contest. We describe our systems and the comparative experiments done when various parameters were changed. These experiments confirmed the effectiveness of using location and category information. 
Masaki Murata, Qing Ma, Kiyotaka Uchimoto, Hiromi Ozaku, Masao Utiyama   and Hitoshi Isahara