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.

a single user identity that can be used to access a group of web sites bound by the ties of federation