Schema Mapping as Query Discovery Renee J. Miller, Laura M. Haas, Mauricio A. Hernandez To enable modern data intensive applications including data warehousing, global information systems and electronic commerce, we must solve the {\em schema mapping} problem in which a source (legacy) database is mapped into a different, but fixed, target schema. Schema mapping involves the discovery of a query or set of queries that transform the source data into the new structure. We introduce an interactive mapping creation paradigm based on {\em value correspondences} that show how a value of a target attribute can be created from a set of values of source attributes. We describe the use of the value correspondence framework in {\em Clio}, a prototype tool for semi-automated schema mapping, and present an algorithm for query derivation from an evolving set of value correspondences.