Schema Exchange: Generic Mappings for Transforming Data and Metadata

In this paper we present and study the problem of schema exchange, a natural extension of the data exchange problem in which mappings are defined over classes of similar schemas. To this end, we first introduce the notion of schema template, a tool for the representation of a set of schemas sharing the same structure. We then define the schema exchange notion as the problem of: (i) taking a schema that matches a source template, and (ii) generating a new schema for a target template, on the basis of a mapping between the two templates defined by means of FO dependencies. This framework allows the definition, once for all, of generic transformations that can be applied to different schemas. A method for the generation of a "correct" solution of the schema exchange problem is proposed and a number of general results are given. We also show how it is possible to generate automatically, from a schema exchange solution, a data exchange setting that reflects the semantics of the mappings between the original templates. This allows the definition of queries to migrate data from a source database into the one obtained as a result of a schema exchange.