"Data access to a variety of data stores, using consistent rules and definitions that enable all the data stores to be treated as a single resource." (Judith Hurwitz et al, "Service Oriented Architecture For Dummies 2nd Ed.", 2009)
"Technology that joins data from different sources, operational or analytic, around an organization. Data federation allows users to have a single view of disparate data without having to understand the details of the individual data sources." (Tony Fisher, "The Data Asset", 2009)
"A method of transparently joining or linking data from multiple physical locations and/or multiple platforms." (DAMA International, "The DAMA Dictionary of Data Management", 2011)
"Data access to a variety of data stores, using consistent rules and definitions that enable all the data stores to be treated as a single resource. " (Marcia Kaufman et al, "Big Data For Dummies", 2013)
"Data federation technology is software that provides an organization with the ability to aggregate data from disparate sources in a virtual database so it can be used for business intelligence (BI) or other analysis." (Techtarget)
"Process where data is collected from distinct databases without ever copying or transforming the original data." (Solutions Review)
