... millions of data sources and makes possibledata sharing among them. The widespread adoptionof XML as a standard syntax to share data has fur-ther streamlined and eased the data sharing process.The ... (e.g.,(Garcia-Molina et al. 1997; Levy, Rajaraman, & Or-dille 1996; Ives et al. 1999; Lambrecht, Kambham-pati, & Gnanaprakasam 1999; Friedman & Weld 1997;Knoblock et al. 1998)). Such a ... the database community. It has receivedsteady attention over the past two decades, and hasnow become a prominent area of database research.In this article, we first review database applicationsthat...