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WPI-CS-TR-01-03 March 2001 Change and Relationship-Driven Content Caching, Distribution and Assembly 1 by Mikhail Mikhailov Craig E. Wills Computer Science Technical Rep ort Series W ORCESTER POLYTECHNIC INSTITUTE Computer Science Department 100 Institute Road, Worcester, Massachusetts 01609-2280 1 This work is partially supp orted by the National Science Foundation Grant CCR-9988250. Abstract Web caching and Content Distribution Networks (CDNs) seek to reduce retrieval latency, lower bandwidth usage and reduce load on the origin servers by moving the oered content closer to the end users. Historically, the content replicated to the edges of the network in this way has b een mostly static, such as images. As more dynamic and p ersonalized content is b eing oered on the Web, there is a growing need for mechanisms capable of caching and replicating content that changes frequently and is user-sp ecic. In addition, existing caches heuristically estimate ob ject freshness lifetimes, which results in unnecessary validation traÆc b etween caches and origin servers, and do es not prevent caches from serving stale ob jects to their clients. In this work we describ e a mechanism that makes caching of Web ob jects more deterministic, reduces validation traÆc, increases the amount of content that may b e cached, and reduces the amount of dynamic content that must b e retrieved from the origin server. Our mechanism uses a numb er of techniques in concert. First, ob jects that constitute a page