Transmission of continuous query results in mobile computing systems

In a mobile computing environment, a user with a wireless connection to the information network can access data via submitting queries to data servers . As the mobility is the most distinguishing feature of the mobile computin g paradigm, location becomes an important piece of information for the so-c alled location-dependent queries, where the answer to a query depends on th e current location of the user who issued the query. A location-dependent q uery submitted by a mobile user can become more difficult to process when i t is submitted as a continuous query (CQ) for which the answer changes as t he user moves. The answer to a location-dependent CQ can be provided as a s et of tuples [S, begin, end] indicating that object S is the answer of the query from time begin to time end. Once the tuples in the answer set are de termined, the next step is to determine the transmission time of these tupl es to the user. Transmission time of tuples is critical in the sense that i t can have a considerable impact on both the communication overhead imposed on the wireless network and the availability of tuples in case of disconne ctions. In this paper, we propose three tuple transmission approaches that can be used to determine the transmission time of tuples in the answer set of a location-dependent CQ. We also evaluate the relative performance of th e proposed approaches under different settings of environmental parameters. (C) 2000 Elsevier Science Inc. All rights reserved.