On processing spatial queries in mobile client/server environments

With the emergence of wireless communication, portable computing and location sensing technologies, location-based data-intensive applications have been developed in various areas. Location-based applications make use of location information to support spatial queries (e.g., finding the nearest hotel for a user or displaying all restaurants in the geographic area around him). In this thesis, we study the processing of spatial queries in mobile environments, where users can issue spatial queries to the server while they are moving. Due to the mobility of users, the server must have the ability not only to produce results that are valid with respect to their current locations but to update the results as the users move to new locations. Coupled with the large number of users anticipated in mobile environments, the server should be able to handle high workload and as such calls for efficient query processing methods. Considering the uniqueness of mobile client/server environments, this thesis (i) studies the region in which the user can move without affecting the result of a window query, thus eliminating the expensive communication cost between the user and the server in checking the result validity; (ii) introduces top-k spatial join and proposes an efficient query processing algorithm for it; (iii) studies the problem of continuous monitoring k-closest pair query over moving objects, aiming at reducing the communication cost and speeding up the monitoring process; (iv) discusses the real-time parallel processing of window queries on server.