Exploiting Result Equivalence in Caching Dynamic Web Content

Caching is currently the primary mechanism for reducing the latency as well as bandwidth requirements for delivering Web content. Numerous techniques and tools have been proposed, evaluated and successfully used for caching static content. Recent studies show that requests for dynamic web content also contain substantial locality for identical requests. In this paper, we classify locality in dynamic web content into three kinds: identical requests, equivalent requests, and partially equivalent requests. Equivalent requests are not identical to previous requests but result in generation of identical dynamic content. The documents generated for partially equivalent requests are not identical but can be used as temporary place holders for each other while the real document is being generated. We present a new protocol, which we refer to as Dynamic Content Caching Protocol (DCCP), to allow individual content generating applications to exploit query semantics and specify how their results should be cached and/or delivered. We illustrate the usefulness of DCCP for several applications and evaluate its effectiveness using traces from the Alexandria Digital Library and NASA Kennedy Center as case studies.