The authors present M(DM), an extensible metalevel system in which the syntax and the semantics of data models, schemas, and databases can be uniformly represented. M(DM) consists primarily of a set of metatypes that capture and express data-model constructs in second-order logic: a data model is represented as a collection of M(DM) metatypes. To achieve extensibility, M(DM)'s metatypes are organized into an inheritance lattice. The robustness and openness of the approach are demonstrated by expressing a variety of data models in M(DM), and the authors show how to exploit M(DM)'s metalevel capabilities for hiding representational heterogeneities in multimodel multidatabase systems.>

The view-object model provides a formal basis for representing and manipulating object-based views on relational databases.