Preliminary explorations in specifying and validating entity-relationship models in PVS

Entity-Relationship (ER) diagrams are an established way of doing data modeling. In this paper, we report our experience with exploring the use of PVS to formally specify and reason with ER data models. Working with a text-book example, we rely on PVS's theory interpretation mechanism to verify the correctness of the mapping across various levels of abstraction. Entities and relationships are specified as user defined types, while constraints are expressed as axioms. We demonstrate how the correctness of the mapping from the abstract to a conceptual ER model and from the conceptual ER model to a schema model is formally established by using typechecking. The verification involves proving the type correctness conditions automatically generated by the PVS type checker. The proofs of most of the type correctness conditions are fairly small (four steps or less). This holds out promise for complete automatic formal verification of data models.