| Summary: | 碩士 === 國立東華大學 === 資訊工程研究所 === 85 === For effective and adaptive information access in mobile
environment, we investigate the feasibility of applying active
database concept as a foundation for mobile information systems.
Mobile environment is characterized by the resource limited
nature of mobile hosts as well as the dynamically changing
environment. To overcome availability, latency, bandwidth, and
other resource restrictions, we design an active rule processing
algorithm which can execute efficiently and correctly in mobile
environment. The design is based on a cross analysis of mobile
network and active database rule processing semantics. The
principle strategies and design approach are the identification
of execution modes, execution phases, as well as intelligent
caching and prefetching of data. A combination of static
analysis and dynamic analysis is used for predicative caching.
The static analysis method employs a technique to generate view
definition from rules and profile. Dynamic analysis is intended
to be used for adapting view definition and materialization
strategies. The effectiveness of our approach is evaluated by
both an analytical model and simulation. Experimentation results
indicate that the performance of mobile information systems can
be significantly improved when the cache size is large enough to
hold all data that are designated for prefetching. When the
cache size is not large enough to hold all designated data,
proper cache replacement strategies can still result in
considerable performance improvement.
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