Pervasive applications, such as location-based services and natural habitat monitoring, have attracted plenty of research interest. These applications make use of a large number of remote positioning devices like Global Positioning System (GPS) for collecting users’ physical locations. Generally, these devices have battery power limitation. They also cannot report very accurate position values. In this paper, we consider the evaluation of a long-standing (or continuous) query over inaccurate location data collected from positioning devices. Our goal is to develop an energy-efficient protocol, which provides some degree of confidence on the query answers evaluated on imperfect data. In particular, we propose the
, which governs GPS devices to decide upon whether location values collected should be reported to the server. We further discuss how these filters can be developed. This scheme reduces the cost of transmitting location updates, and hence the energy spent by the GPS devices. It also allows some portion of query processing to be deployed to the devices, thereby alleviating the processing burden of the server.