Date Added: Sep 2010
In the last decade, several large-scale wireless sensor networks have been deployed to monitor a variety of environments. The declarative nature of the database approach for accessing sensor data has gained great popularity because of both its simplicity and its energy-efficient implementation. At the same time another declarative abstraction made its way into mainstream sensor network deployments: user-defined groups of nodes. By restricting the set of nodes that participate in a task to such a group, the overall network lifetime can be prolonged. It is straightforward to see that integrating these two approaches that is, restricting a query's scope to a group of sensor nodes, is beneficial.