| Summary: | 碩士 === 中華大學 === 資訊管理學系 === 95 === Data broadcast is an efficient method for disseminating data items in a mobile computing environment. With the data broadcast methods, data items are broadcasted periodically according to a predetermined schedule. And therefore, the problem for the scale of mobile clients is overcome by data broadcasting. To ensure users execute an application correctly, the criterion usually follows mutual consistency. For this reason, the mobile client spent large cost on data validation. However, many real life applications don’t need so restricted criterion. Therefore, we relax the criterion from mutual consistency to consistency, that is, the mobile client may not access the up-to-date contents of the required data items in its application.
To relax the consistency criterion, we had designed the new caching method. In the method, caching data are kept in three different version sets – current version set, new version set and invalid version set. Further, we analyze the performance of the caching method through discrete event simulation. The performance results show that the access time of the version sets caching method is shorter than that of its counterparts, even when network disconnection is common or disconnection time is long.
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