Database applications in wireless sensor networks very often demand data collection from sensor nodes of specific target regions.\nDesign and development of spatial query expressions and energy-efficient query processing strategy are important issues for sensor\nnetwork database systems. The existing sensor network database systems lack the needed sophistication for the space calculation\nof the target sensor nodes; hence, unnecessary query/data transmissions are required between the sensor nodes and the server.\nThis paper describes our spatial operations and energy-efficient query processing methods that are designed and implemented\nin our sensor network database system called SNQL+????. With a set of spatial operators based on geometric parameters, such as\nEnvelope, NearBy, Distance, Direction, and set theoretic operators, SNQL+???? allows sensor network applications to easily specify the\ntarget space of interest. Our energy-efficient query processing strategy implements an in-network querymanagement based on the\nlowest common ancestor (LCA) algorithm, so that the query processing cost for calculating the target spaces is greatly reduced by\navoiding the need of heavy query/data transmissions between the base-station and target nodes. Performance evaluation shows that\nour proposed design and implementation of spatial query expressions and processing strategy achieve improved energy efficiency\nfor database operations in the wireless sensor network.
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