Selecting Expansion Terms in Automatic Query Expansion Hiroko Mano Software Research Center Ricoh Company, Ltd. 1-1-17 Koishikawa, Bunkyo-ku Tokyo 112-0002 JAPAN mano@src.ricoh.co.jp Yasushi Ogawa Software Research Center Ricoh Company, Ltd. 1-1-17 Koishikawa, Bunkyo-ku Tokyo 112-0002 JAPAN yogawa@src.ricoh.co.jp 1. INTRODUCTION 2. EXPERIMENT Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SIGIR’01, September 9-12, 2001, New Orleans, Louisiana, USA. Copyright 2001 ACM 1-58113-331-6/01/0009 ... 5.00. 2.1 Term Selection Value functions 390