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.

To overcome availability, latency, bandwidth, and cost barriers of mobile networks, mobile clients of distributed file systems switch between connected and disconnected modes of operation. Lying between these are modes of operation that refine the consistency semantics of cached files, allowing a mobile client to select a mode appropriate for the the prevailing network conditions. Clients can take advantage of network opportunities unsuitable for connected operation, obtaining improved performance, more effective sharing, and more stringent consistency guarantees as a result.