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We describe MIDST, an implementation of the model management
operator ModelGen, which translates schemas from one model
to another, for example from OO to SQL or from SQL to XSD. It extends
past approaches by translating database instances, not just their
schemas. The operator can be used to generate database wrappers (e.g.
OO or XML to relational), default user interfaces (e.g. relational to
forms), or default database schemas from other representations. The approach
translates both schemas and data: given a source instance I of a
schema S expressed in a source model, and a target model TM, it generates
a schema S0 expressed in TM that is “equivalent” to S and an
instance I0 of S0 “equivalent” to I. A wide family of models is handled
by using a metamodel in which models can be succinctly and precisely
described. The approach expresses the translation as Datalog rules and
exposes the source and target of the translation in a generic relational
dictionary. This makes the translation transparent, easy to customize