A Knowledge Based Paradigm for Querying Databases

The so called Visual Query Systems try to support unskilled users in formulating complex queries to highly structured databases, by providing graphic paradigms for visualizing the database conceptual models, and by allowing to build queries through visual interactions. In the present paper we propose a paradigm, for supporting the user in building sophisticated queries, based on a uniform graphical presentation of conceptual models and queries. Its most important novelty is that it is based on a semantic representation of the database conceptual models in terms of Description Logics. In this way it is possible to perform relevant inferential tasks on the query, in order to allow the user to: (i) interactively and iteratively build queries; (ii) be prevented from building inconsistent queries; (iii) interactively explore the database semantics ; (iv) be gradually introduced only to those part of the conceptual model relevant for the query formulation; (v) be provided with simple, but eeective, features for query reenement and query generalization.