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.