Practical distributed database systems operate without rigid centralized control. Such systems are considered to be federated distributed systems, and attractive for involving many sites, dispersed authority, and differences in requirements of level of data abstraction and of all data being-up-to-date. The interaction via communication networks, the partial limited availability of network nodes, delays in local data acquisition, and the actual delay and cost of computations to derive data for remote sites all conspire to defeat simple approaches to network- wide data consistency. The problems of lack of synchrony among the nodes have been recognized piecemeal and many methods and heuristics to manage data in this environment have been proposed. We have a simple model to permit designers and users to specify the extent to which consistency can be temporarily relaxed. The FAUVE research classifies existing algorithms and heuristics, identifies conflicts in assumptions made, and recognizes complementary approaches. It provides a framework to focus on situations now not adequately dealt with. This framework provides the users with specifications, and provides database operations on federated databases with a measure of success or failure. Such a measure is essential for the scientific progress in this subtopic of modern computer systems research.
