“…They assume either that the available data sources have been organized according to the underlying data model or that the data sources have been converted to obey it. For example, Quarry (Howe et al., ) and Semex (Cai, Dong, Halevy, Liu, & Madhavan, ) use resource description framework (RDF) as their data model, whereas OrientSpace (Li & Meng, , ) and iMemex (Dittrich & Salles, ; Salles, Dittrich, Karakashian, Girard, & Blunschi, ) use their own data model specifically designed for their respective purposes.…”