Federated identity management involves exchanging identity information across one or more trusted domains (either within a single company or between different companies) in such a way that the information is maintained only once – at its particular source. Federation is the ideal solution when it is necessary for users to gain access to multiple applications "owned" by other companies or business units. See www.mycroftinc.com/solutions/federatedidentity
A user s identity is said to be federated between a set of Providers when there is an agreement between the providers on a set of identifiers and/or attributes to use to refer to the user.
The management and use of identity information across security domains, e.g. between Federation Members of SWITCHaai. Federated Identity inevitably deals with issues like liability, security, privacy and trust.