Weak Cache Coherency in Mobile Environments

Under mobile environments, client caching provides an effective way to improve client-server database system performance. How to maintain cache coherency is an important issue in caching research. Because of the low bandwidth and high expense of wireless network, it will cost a lot to maintain strong cache coherency. Furthermore, considering the factors of bandwith, overhead and reliability, the client may allow the cache to maintain weak coherency. That is to say, the client allows a divergence between the cache and the data of the server. Based on semantic cache, this paper presents a way to define the allowed divergence, and proposes a cache coherence algorithm based on the period of validity.