On the Notion of Concept

The notion of concept is central to the notion of data model in databases. Its purpose is to provide construction mechanisms for organizing a universe of data into manageable segments with a well-deened structure. However, so far the notion lacks rigor with a concomitant danger of inconsistent, overlapping or redundant use of concepts. The paper takes the approach that rigor is achieved by expressing the intuitive semantics within a formal logic. In doing so, the notion of concept may also provide a mechanism for structuring sets of facts, rules, and constraints in general deductive databases. In the paper a formal semantics for concept deenitions is given by showing that each concept deenition can be interpreted as a mapping from one database state to another. A number of examples show the usefulness of the concept dee-nition. Especially, the basics of object-orientation are modeled as concepts. The paper also examines some diicult issues arising in connection with the concepts in conventional data models. First practical experiences are related, and topics for further research are pointed out.