Maintaining page coherence for dynamic HTML pages

Fueled largely by the gaining popularity of World Wide Web (web) servers and browsers, more and more sites have published their databases to the Internet/Intranet. This allows users to retrieve and explore database items as "dynamic" HTML pages. Existing dynamic HTML pages are passive. When the content of a database is changed, the corresponding dynamic HTML page does not get reflected. We term this, the page coherence problem. In this paper, we illustrate the limitations of current web browsers in addressing the page coherence problem. We next illustrate that, since a dynamic HTML page is maintained in the storage cache of a web client, maintaining the coherence of a dynamic HTML page is similar in spirit to cache coherence problem. However, since a web server is both stateless and connectionless, conventional "push-based" cache coherence approaches that require a server to invalidate and propagate the updates to the cache are not feasible. We propose a page coherence mechanism which requires a web client to take an active role in invalidating and updating its cache and thus, a dynamic HTML page. We illustrate our implementation on Netscape Navigator using Netscape Plug-ins. The effectiveness of our mechanism is also studied experimentally.