Editing Federated database system (section)

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A '''federated database system''' ('''FDBS''') is a type of [[Meta (prefix)|meta-]][[database management system]] (DBMS), which transparently maps multiple autonomous [[Database management system|database systems]] into a single '''federated database'''. The constituent [[database]]s are interconnected via a [[computer network]] and may be geographically decentralized. Since the constituent database systems remain autonomous, a federated database system is a contrastable alternative to the (sometimes daunting) task of merging several disparate databases. A federated database, or '''virtual database''', is a composite of all constituent databases in a federated database system.  There is no actual data integration in the constituent disparate databases as a result of data federation.

Through [[data abstraction]], federated database systems can provide a uniform [[user interface]], enabling [[user (computing)|users]] and [[Client (computing)|clients]] to store and retrieve [[data]] from multiple noncontiguous [[database]]s with a single [[Information retrieval|query]]—even if the constituent databases are [[heterogeneous]]. To this end, a federated database system must be able to decompose the query into subqueries for submission to the relevant constituent [[database management system|DBMSs]], after which the system must composite the [[result set]]s of the subqueries. Because various database management systems employ different [[query language]]s, federated database systems can apply [[wrapper function|wrappers]] to the subqueries to translate them into the appropriate [[query language]]s.