The mobile computing paradigm introduces new technical issues in the area of database systems. Fspecially, mobility of hists engenders a new kind of locality that migrates as hosts move. In mobile computing environment, the location of user is a frequently changing piece of data. Due to this nature, problems can occur when locations become subjects of queries, such as in aggregate location dependent queries. In this paper, we propose the position locking mechanism, a technique to overcome such problems. Using position locking, the aggregate location dependent query can be guaranteed to get the consistent result. We also propose some techniques that can improve the performance of position locking and reduce its network bandwidth consumption.
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