An extended abstract of this paper appeared in Proceedings of the 15th ACM SIGACT-SIGMODSIGART Symposium on Principles of Database Systems [1]. 2 E-mail: pankaÄcs.duke.edu; httpÂÂwww.cs.duke.edu pankaj. Supported in part by National Science Foundation Research Grants EIA-9870724 and CCR-9732787, by Army Research Office MURI Grant DAAH04-96-1-0013, by a Sloan fellowship, by a National Science Foundation NYI award, and matching funds from Xerox Corporation, and by a grant from the U.S. Israeli Binational Science Foundation. 3 E-mail: largeÄcs.duke.edu; http:ÂÂwww.cs.duke.edu large. Supported in part by U.S. Army Research Office MURI Grant DAAH04-96-1-0013 and by National Science Foundation Research Grant ESS EIA-9870724. 4 E-mail: jeffeÄcs.unic.edu; http:ÂÂwww.uiuc.edu jeffe. Supported in part by National Science Foundation Grant DMS-9627683 and by U.S. Army Research Office MURI Grant DAAH04-96-1-0013. Part of this work was done while this author was at Duke University as ...
Pankaj K. Agarwal, Lars Arge, Jeff Erickson, Paolo