User mobility and data exchange through wireless communication give Location Based Search Engine some unique characteristics that the traditional spatial query processing in centralized databases. In a mobile environment, a typical Location Based Search Engine is of the form “find the top-three nearest hospitals.” The result of the query depends on the location of its requester. Caching and sharing of query results must take into consideration the location of the query issuer. The database resides in a centralized server, which typically serves a large mobile user community through wireless communication.
Due to user mobility, answers to an LBSE will lose their relevancy if there is a long delay in query processing or in communication. For example, answers to the query “find the top-three nearest hospitals” received After 5 minutes of high-speed driving will become meaningless. Instead, a prompt, albeit approximate, answer, telling the user right away the approximate top-three nearest hospitals, may serve the user much better. The wireless environment and the communication constraints play an important role in determining the strategy for processing Location Based Search Engine.