Local Semantics for Federated Databases

In many applications which need for a large amount of information, knowledge is partitioned and represented in a set of databases (DB) integrated in a federated database (FDB). A FDB is a collection of distributed, partial, redundant, and partially autonomous DBs. Distribution, redundancy, partiality and autonomy generate many problems in the management of a FDB. The most important are semantic etherogenity, update propagation, inter-schema dependencies, and query distribution which need for a formal treatment. Several approaches have been proposed in the past. However these formalisms are inadequate as they partially represent some of the aspects, but they fail to represent all of them. The goal of this paper is to develop a formal semantics called local semantics, for FDB, which explicitly represents distributed, redundant, partial, autonomous DBs. We substantiate the above adequancy claim by formalizing three motivating examples which involves all these aspects