An adaptive query management technique for real-time monitoring of spatial regions in mobile database systems

This paper presents a technique for real-time monitoring of mobile objects in user-defined spatial regions. We refer to such regions as range-monitoring queries. Unlike conventional queries, which are based on an instant of the database at some moment in time, range-monitoring queries are continuous for monitoring purposes. Such queries can last for an extended period of time; and many can be active simultaneously. We present an efficient technique for managing such continuous queries. This capability is not available in conventional database management systems which are designed to manage data, not queries. In our environment, each mobile object is associated with a resident domain and is made aware of the monitoring areas inside it. When an object moves, it monitors its spatial relationship with its known monitoring areas. If it crosses any query boundaries, it reports server and the server updates the affected query results accordingly. When an object moves out of its resident domain, the server will determine a new one for the object. This process is supported efficiently with our new index structure called Domain tree. Our simulation results indicate that our technique is many times better than a recent method in terms of communication cost and server processing cost.