Polymorphism in datalog and inheritance in a metamodel (extended abstract)

We discuss the restructuring of a metamodel designed for representing several data models in a uniform way. This metamodel is currently used within MIDST, our Model Management proposal for performing translations of schemas and databases from a model to another. Such a restructuring is carried out by introducing hierarchies and, consequently, extending Datalog by providing it with inheritance and polymorphism in order to take advantage of them. In comparable scenarios, where predicates of the metamodel share structural elements and rules are syntactically and semantically similar, the use of hierarchies and a particular form of polymorphism provide significant advantages. These advantages range from simplifying the specification of elementary and complete translations (i.e. Datalog rules and programs, respectively) to ensuring a higher level of reuse for them, thus further improving the development of such rule-based systems.