Finitely Representable Databases St Ephane Grumbach

We study classes of innnite but nitely representable databases based on constraints, motivated by new database applications such as geographical databases. The mathematical framework is based on classical decidable rst-order theories. We investigate the theory of nitely representable models and prove that it diiers strongly from both classical model theory and nite model theory. In particular, we show that most of the well known theorems of either one fail (compactness, completeness, locality, 0/1 laws, etc.). An immediate consequence is the lack of tools to consider the deenability of queries in the relational calculus over nitely representable databases. We illustrate this very challenging problem through some classical examples.