Model-Independent Schema and Data Translation

We illustrate the development of Extended-ModelGen, the model management operator that translates schemas and instances from one model to another, for example, from ob-ject to SQL or from SQL to XSD. The oper-ator can be used to generate database wrap-pers (e.g. object or XML to relational), de-fault user interfaces (e.g. relational to forms), or default database schemas from other repre-sentations. The approach handles the trans-lation of instances: given a source instance I, referring to a schema S expressed in a source model, and a target model TM, it generates a schema S ′ expressed in TM that is “equiva-lent ” to S and an instance I ′ of S ′ equivalent to I. A wide family of models is handled, by using a metamodel in which models can be succinctly and precisely described. The ap-proach makes use of a dictionary to represent models, schemas, instances as well as the rules that implement translations. Rules are writ-ten in a Datalog dialect with oid invention and can therefore be easily customized.