Query reformulation Mediated schema A query CD: ASIN, Title, Genre posed over CD(A, T,G) a set of queries on the data sources CDs Books Album Authors ASIN ISBN ISBN Price FirstName DiscountPrice DiscountPrice LastName Studio Edition Artists ASIN CDCategories Bookcategories ArtistName ASIN ISBN GroupName Category CategoryQuery reformulation Books Title ISBN Price DiscountPrice Edition CDs Album ASIN Price DiscountPrice Studio BookCategories ISBN Category CDCategories ASIN Category Artists ASIN ArtistName GroupName Authors ISBN FirstName LastName CD: ASIN, Title, Genre,… Mediated Schema A query posed over CD(A,T,G) a set of queries on the data sources