Strategies for Cache Invalidation of Location Dependent Data in Mobile Environment

摘要

Mobile computing as compared to traditional computing paradigms enables clients to have unrestricted mobility while maintaining network connections. Data management in this paradigm poses new challenging problems to the data base community. Location Dependent Information Services (LDIS) is an emergent application in this area where information provided to users depends on their current locations. Data caching at mobile clients play a key role in data management due to its ability to improve system performance and overcome availability limitations. Spatial data cached in the mobile clients may become invalid because of the movement of the client. Cache Invalidation schemes aims to keep data consistency between the client's cache and the server. To maintain consistency ofLDD in cache, valid scope of that data item is identified and stored along with it in the client's cache. In this paper, we study the selection procedure of finding best suitable candidate for valid scope (i.e., best suitable sub polygon of a given polygon) and propose a generalized algorithm which selects the best suitable candidate for valid scope. We compare its performance with the existing algorithms. More over, we also introduced new algorithm CEFAB_G which tries to improve the performance by considering the user movement pattern and speculation about its future access.