Combining the functionality of personal locator technologies, wireless and cellular telephone technologies, and information technologies enables new environments where virtually all objects of interest can determine their locations. The PLACE (Pervasive Location Aware Computing Environments) project focuses on the efficient support of location-aware services in such a new environment. A key feature of the architecture underlying PLACE is the ability of mobile users to issue queries whose responses depend not only on static data but also on data continuously collected by servers from other objects. We refer to these as continuous queries.
The technical challenges for providing services based on continuous queries include scalability, real-timeliness of responses, and effective use of limited resources such as bandwidth, memory and battery life at objects. Mobile objects in PLACE know their own location and have profiles which can include the identity and current interests. Examples of objects include mobile users with handhelds, GPS-enabled vehicles, and stationary establishments such as restaurants. PLACE makes use of off-the-shelf technologies. This includes commercial forms of location-reporting and tracking technologies, wireless and cell phone technologies, and database technologies.
The current PLACE prototype consists of a small-scale, GPS-based system which makes use of the campus's wireless service areas. A server tracks, monitors, and responds to queries of objects moving on the Purdue campus. The combination of off-the-shelve GPS devices (from Garmin, Magellan, and Pharos), mobile handheld devices (including HP-Jornada's and Compaq-iPAQ's) and web-based map servers support the execution of simple spatio-temporal queries.