Nowadays, one of the objectives of information integration is to provide a global (virtual or materialized) view of the information contained in a set of information sources. This is an important objective as global views enable us to design applications that use information contained in a set of autonomous and heterogeneous information sources. The global view is represented using a global schema, which is usually different from the schemata of the information sources (also called local schemata). Users interested in exploiting the global information must be aware of the global schema. One of the drawbacks of this approach is that users working with local applications, which are often interested in exploiting global information, cannot access global information using their own local applications, as the last ones are based on local schemata and are hardly adaptable to the global schema.