In a previous paper [l], we described ARTour Web Express, a software system that makes it possible to run World Wide Web applications over wide-area wireless nehvorks. Our earlier paper discussed how our system significantly reduces user cost and response time during online browsing over wireless communications links. Even with these savings, however, users may experience slow performance. This is a result of the inherent delay of wireless communication coupled with congestion in the Internet and Web servers, which cannot be masked Corn users under the synchronous request/response model of browsing. Furthermore, disconnection - both voluntary and involuntary - is common in the mobile environment, and the standard browsing model provides no support for disconnected operation. This paper describes how ARTour Web Express has been enhanced to support both disconnected and asynchronous operation.

Mobile computing adds a new wrinkle to the ageold problem of caching. Today's wireless links are both slow and expensive, and are not always available to a user. Therefore, when a mobile user is disconnected, a cache miss means (at best) a substantial cost in time and money, or (at worst) a complete halt to work if critical information has not been cached. Existing solutions to this problem rely on some combination of explicit hoard profiles and spying on a user's file accesses.

The work habits of many individuals yield file access patterns that are quite pronounced and can be regarded as defining working sets of files used for particular applications. A client management technique for detecting these patterns and then exploiting them to successfully prefetch files from servers is described. Trace-driven simulations show the technique substantially increases file cache hit rate in a single-user environment. Successful file prefetching carries three major advantages: applications run faster, there is less burst load placed on the network, and properly loaded client caches can better survive network outages. The technique requires little extra code, and-because it is simply an augmentation of the standard LRU client cache management algorithm-is easily incorporated into existing software.>