Editing Federated database system (section)

=== Autonomy ===
Fundamental to the difference between an MDBS and an FDBS is the concept of autonomy.  It is important to understand the aspects of autonomy for component databases and how they can be addressed when a component DBS participates in an FDBS.
There are four kinds of autonomies addressed:
* Design Autonomy which refers to ability to choose its design irrespective of data, query language or conceptualization, functionality of the system implementation.
[[Heterogeneous Database System|Heterogeneities]] in an FDBS are primarily due to design autonomy.
* Communication autonomy refers to the general operation of the DBMS to communicate with other [[Database management system|DBMS]] or not.
* Execution autonomy allows a component DBMS to control the operations requested by local and external operations.
* Association autonomy gives a power to component DBS to disassociate itself from a federation which means FDBS can operate independently of any single [[Database|DBS]].

The ANSI/X3/SPARC Study Group outlined a three level data description architecture, the components of which are the conceptual schema, internal schema and external schema of databases.  The three level architecture is however inadequate to describing the architectures of an FDBS.  It was therefore extended to support the three dimensions of the FDBS namely Distribution, Autonomy and Heterogeneity.  The five level schema architecture is explained below.