1. College of Information StudiesUniversity of Maryland, College Park MD 20742‐4345 USA
2. College of Information Studies & Robert H. Smith School of BusinessUniversity of Maryland, College Park MD 20742‐4345 USA
3. Department of Library Science, Graduate School of Integrated Frontier SciencesKyushu University Fukuoka 812‐8581 Japan
4. ollege of Information Studies & University of Maryland Institute for Advanced Computer Studies (UMIACS)University of Maryland, College Park MD 20742‐4345 USA