Integration of Data Semantics in Heterogeneous Database Federations

Modern information systems are often distributed in nature; data and services are spread over different component systems wishing to cooperate in an integrated setting. Information integration is a very complex problem and is relevant in several fields, such as data reengineering, data warehousing, Web information systems, e-commerce, scientific databases, and B2B applications. Information systems involving integration of cooperating component systems are called federated information systems; if the component systems are all databases then we speak of a federated database system (Rahm & Bernstein, 2001; Sheth & Larson, 1990). In this article, we will address the situation where the component systems are so-called legacy systems; i.e., systems that are given beforehand and which are to interoperate in an integrated single framework in which the legacy systems are to maintain as much as possible their respective autonomy.