The Active Cache protocol allows a rich variety of processing to be accomplished at the proxy system. Below, we describe the applets we have implemented. One of main reasons many Web server disables caching is to collect information on who access their documents. Both server and proxy suffer from such practice, as the former has to buy a lot of resources to handle the volume of incoming requests, and the latter has to pay for the Internet traffic.
Active cache solves the dilemma by using a log applet.
We have implemented a log applet, whose FromCache method simply writes the client IP address, the date of the access, and the HTTP request to the log object. The applet is assured that the log object will be sent back to the server eventually. Another reason that servers disable caching is to change the presentation of the document upon every request, for example, putting on different advertising banners. This again conflicts with proxy caching. The applet, when invoked, first checks for the object that specifies the banners, their positions in the document, and their frequencies of appearance.