Federated database system

A federated information system (often federated database system ) is an information system that provides access to multiple autonomous information sources, without whose data is copied, as is the case for example in a data warehouse. This form of integration of multiple data sources, in which they remain unchanged even is also referred to as virtual information integration. " Federated " is this system because it is an amalgamation of individual systems which retain their respective independence.

Construction

In the construction of federated information system various schemes of the source must be combined into a global schema ( schema transformation and integration ). Local -as -view and global -as -view are two different approaches when merging schemes. The user of a federated information system can then access via the global schema to the data as if it was dealing with a single database system. The integration of data sources is usually done via so-called wrappers and a mediator, why are the majority of federated information systems mediator - based information systems.

Definition

A short and precise definition for federated database system is according to Bauer and Günzel (based on Conrad) as follows:

" A federated database system is a multi- database system with a comprehensive all -component systems (global) conceptual schema. All component systems have to preserve their autonomy and their local conceptual schema, ie, they remain in terms of self-employed in the design, execution and communication. "

Basic Properties

• The data will remain on site at the various sources of information.
• The information sources are autonomous and do not need to be adapted for integration.
• Inquiries are made declaratively to a global schema.
• Requests can be distributed to various information sources ( for example, load balancing ).