Approximating Sensor Network Queries with In- Network Summaries Alexandra Meliou Carlos Guestrin Joseph M. Hellerstein Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2008-137 http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-137.html October 21, 2008