Query Strategies for Priced Information

’ A preliminary version of this paper appeared in “Proceedings of the 32nd Annual ACM Symposium on Theory of Computing,,” Portland, OR, May 2000. ‘Current affiliation: Department of Computer Science, Princeton University, Princeton, NJ 08544. Most of this work was done while the author was at Stanford University and was visiting IBM Almaden Research Center. Research at Stanford was supported by the Pierre and Christine Lamond Fellowship, NSF Grant IIS-9811904.. and NSF Award CCR-9357849, with matching funds from ,IBM, Mitsubishi, Schlmberger Foundation, Shell Foundation, and Xerox Corporation. ’ Most of this work was done while the author was visiting the IBM Almaden Research Center. ‘Supported in part by a David and Lucile Packard Foundation Fellowship, an Alfred P. Sloan Research Fellowship, an ONR Young Investigator Award, and NSF Faculty Early Career Development Award CCR-9701399. 5 Current atEit.ion: Verity, Inc. Work was done while the author was at the IBM Ahnaden Research Center. 6Cutrent affiliation: Department of Computer Science, Princeton University, Princeton, NJ 08544. Most of this work was done while the author was visiting the IBM Ahxiaden Research Center.