This paper describes an intelligent data retrieval system, designed for the Epidemiological Observatory of Emilia Romagna, named IDEA. This system is an attempt to formalize the interaction between the data logical view and its real physical organization in databases. The formalization chosen comes from expert-system knowledge representation technology, following an approach similar to McClay. Its implementation has been realized using an object-oriented library of SICStus Prolog and the APPEAL programming environment. The resulting system can be seen as the basic component of a general-purpose decision support system, whose development is foreseen in the near future.