Support for partial propagation of modifications made to a shared database or file system has been provided before. This paper, however, is the first to introduce mechanisms that support propagating partial-fidelity versions of modifications, as well as their progressive improvement. WebDAV [30], and LBFS [20] implement file systems for wide-area and low-bandwidth networks. Coda [14], Ficus [25], and Bayou [29] provide support for document editing on disconnected devices. These systems differ from CoFi in that they are not aware of the fidelity level of the objects they replicate.
While various adaptation systems [1,5,7,8,11,12,17,19,21,28] use subsetting and versioning to reduce document download time, CoFi is the first to provide adaptation support for multimedia authoring and collaborative work over bandwidth-limited devices.
Several efforts [3,9,18] have used component-based technologies to implement collaborative applications that adapt to variations on network connectivity, or have implemented collaborative applications that use the document's component structure to reduce conflicts or limit the amount of data that need to be present at the device [2,6,13,22,27]. These efforts, however, do not allow the propagation of partial-fidelity versions of modifications. MASSIVE-3 [10] uses transcoding to reduce data traffic necessary to keep users of a collaborative virtual world aware of each other. MASSIVE-3, however, implements a pessimistic single-writer consistency model.