Abstract
In recent years, there has been an increasing interest in the database broadcasting system where the server periodically broadcasts contents of a database to mobile clients such as portable computers and PDAs. There are three query processing methods in the database broadcasting 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 to process 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 choose the optimal method among them statically. In this paper, we propose new query processing methods which dynamically change the order of queries submitted in the queue at the server and also change processing methods for the queries according to the deadline of queries and the system situation. These methods improve the success rate as well as reduce the response time in most cases. ยฉ 2007 Wiley Periodicals, Inc. Syst Comp Jpn, 38(2): 21โ 31, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20689