Editing Federated database system (section)

==Definition==
McLeod and Heimbigner<ref name ="reftwo">"{{cite conference | author = McLeod and Heimbigner | title=A Federated Architecture for information management | book-title = ACM Transactions on Information Systems, Volume 3, Issue 3 | year =1985 | pages = 253–278 | url= http://dl.acm.org/citation.cfm?id=4233}}</ref> were among the first to define a federated database system in the mid-1980s.

A FDBS is one which "define[s] the architecture and interconnect[s] databases that minimize central authority yet support partial sharing and coordination among database systems".<ref name ="reftwo" /> This description might not accurately reflect the McLeod/Heimbigner<ref name="reftwo"/> definition of a federated database.  Rather, this description fits what McLeod/Heimbigner called a ''composite'' database.  McLeod/Heimbigner's federated database is a collection of autonomous components that make their data available to other members of the federation through the publication of an export schema and access operations; there is no unified, central schema that encompasses the information available from the members of the federation.

Among other surveys,<ref name ="refone">"{{cite conference | author=Sheth and Larson | title=Federated Database Systems for Managing Distributed, Heterogeneous, and Autonomous Databases | book-title = ACM Computing Surveys, Vol. 22, No.3 | year=1990 | pages= 183–236 | url=http://dl.acm.org/citation.cfm?id=96604}}</ref> practitioners define a Federated Database as a collection of cooperating component systems which are autonomous and are possibly [[Heterogeneous Database System|heterogeneous]].

The three important components of an FDBS are autonomy, [[Heterogeneous Database System|heterogeneity]] and distribution.<ref name="refone"/> Another dimension which has also been considered is the Networking Environment [[Computer Network]], e.g., many DBSs over a [[Local area network|LAN]] or many DBSs over a [[Wide area network|WAN]] update related functions of participating DBSs (e.g., no updates, nonatomic transitions, [[atomicity (database systems)|atomic updates]]).