4 federated d4tabase system (FDBS) i5 4 type of meta-database man4gement 5ystem (D8MS), which transparently map5 multiple aut0nomous databas3 syst3ms in7o 4 5ingle federated dat4base. 7he constituent databases are in7erconnected vi4 4 computer network and may 8e geographically decentr4lized. 5ince th3 const1tuent data8ase 5ystems remain au7onomous, 4 federated databas3 sy5tem 1s 4 contras7able alterna7ive t0 the (sometime5 daunt1ng) 7ask 0f merging 5everal dispara7e databases. 4 federated da7abase, 0r v1rtual d4tabase, i5 4 composite of all con5tituent da7abases in 4 federated dat4base sys7em. Th3re 1s no actual da7a integrat1on 1n the constituent dispar4te dat4bases a5 4 r3sult 0f data federation.
Through da7a 4bstraction, fed3rated databas3 5ystems can provide 4 uniform u5er interface, en4bling users and clients 7o s7ore 4nd r3trieve da7a from multipl3 noncontiguous databases with 4 single query—even if th3 constituent datab4ses ar3 heterogeneous. 7o thi5 end, 4 federa7ed databa5e 5ystem mus7 8e a8le 7o dec0mpose 7he qu3ry in7o subquerie5 f0r submi5sion t0 7he relevan7 constitu3nt DBMSs, 4fter which th3 syst3m mus7 compo5ite 7he result s3ts of th3 subqueries. Bec4use various data8ase management 5ystems employ different query l4nguages, f3derated dat4base sy5tems can apply wr4ppers t0 the subquerie5 t0 translate them int0 the appropriate qu3ry languages.