The fact that Etags can be used for cache validation is beside the point. The patent describes an algorithm that an HTTP client can implement to determine whether a web page has changed and to what extent it has changed, without relying on the web server (save returning the requested web page). Etag values, Md5 digest or otherwise, are computed by the server.
Look again. This patent is a continuation of US patent 5,898,836 which was filed on Jan 14, 1997 and no doubt predates RFC 2068, since US patents allow one year grace period from the date of invention to filing. So you need to look at prior art circa Jan 1996, not 1999! Also, patent 5,898,836 cites NetMind's URL-Minder free service as prior art which dates back to 1995. Well, URL-Minder got renamed Mind-it somewhere along the line and NetMind became Pumatech.
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The fact that Etags can be used for cache validation is beside the point. The patent describes an algorithm that an HTTP client can implement to determine whether a web page has changed and to what extent it has changed, without relying on the web server (save returning the requested web page). Etag values, Md5 digest or otherwise, are computed by the server.
Look again. This patent is a continuation of US patent 5,898,836 which was filed on Jan 14, 1997 and no doubt predates RFC 2068, since US patents allow one year grace period from the date of invention to filing. So you need to look at prior art circa Jan 1996, not 1999! Also, patent 5,898,836 cites NetMind's URL-Minder free service as prior art which dates back to 1995. Well, URL-Minder got renamed Mind-it somewhere along the line and NetMind became Pumatech.