... Concepts¹¹

Correspondence may be directed to the following addresses: C. S. Jensen, Aalborg University, Datalogi, Fr. Bajers Vej 7E, DK–9220 Aalborg ├ÿ, Denmark, csj@iesd.auc.dk, J. Clifford, Information Systems Dept., Stern School of Business, 613 Tisch Hall, 40 W. 4th Street, New York, NY 10003, jcliffor@is-4.stern.nyu.edu, S. K. Gadia, Iowa State University, Computer Science Dept., 226 Computer Science Building, Ames, IA 50010, gadia@cs.iastate.edu, A. Segev, University of California, School of Business Adm. and Computer Science Research Dept., Lawrence Berkeley Laboratory, 350 Barrows Hall, Berkeley, CA 94720, segev@csr.lbl.gov, and R. T. Snodgrass, University of Arizona, Computer Science Dept., Tucson, AZ 85721, rts@cs.arizona.edu.