Studies (8, 8) have shown that transmitting the changes (deltas) between the new and old versions of dynamic information can reduce network traffic significantly. Delta compression can be easily implemented with cache applets.
We have implemented an applet that upon receiving a client request, sends a request to the original server, including the current request and the last-modified-time of the document. After the server responds with the difference between the new document and the cached version, the applet constructs the reply to the client request using the diff and the cached version.
A similar cache applet can support delta compression of query responses. For example, a query of a particular company's stock quote can be handled by the applet, which simply asks the server for the number and then composes the Web page based on a cached response.