A query processing mechanism based on the broadcast queue for broadcast database systems

In recent years, there has been an increasing interest in the broadcast database system, where the server periodically broadcasts contents of a database to mobile clients such as PDAs. There are three query processing methods in the broadcast database system: (i) the server processes a query and then broadcasts the query result to the client; (ii) the client stores all data that are necessary in processing the query and then processes it locally; and (iii) the server and the client collaborate in processing the query. Since the performance of each method changes according to the situation, such as the interval of query generation and the size of query results, it is difficult to decide the optimal method among them statically. In this paper, we propose a new query processing method which dynamically changes the order of queries submitted in the queue at the server and also changes processing methods for the queries according to the deadline of queries and the system situation. Our method not only improves the response time but also increases the success rate of query processing compared with the traditional methods.