Scalable Consistency Maintenance for Edge Query Caches

Abstract

Semantic database caching is a self-managing approach to dynamic materialization of “semantic” slices of back-end databases on servers at the edge of the network. It can be used to enhance the performance of distributed Web servers, information integration applications, and Web applications of oaded to edge servers. Such semantic caches often rely on update propagation protocols to maintain consistency with the back-end database system. However, the scalability of such update propagation protocols continues to be a major challenge. In this paper, we focus on the scalability of update propagation from back-end databases to the edge server caches. In particular, we propose a publish-subscribe like scheme for aggregating cache subscriptions at the back-end site to enhance the scalability of the ltering step required to route updates to the target caches. Our proposal exploits the template-rich nature of Web applications and promises signicantly better scalability. In this paper, we describe our approach, discuss the tradeoffs that arise in its implementation, and estimate its scalability compared to naive update propagation schemes.