Abstract
Recent research showed the benefits of adopting formal ontologies as a means for accessing heterogeneous data sources. The use of an ontology not only provides a uniform and flexible approach for integrating and describing these sources, but it can be used to improve the usability of an integrated system by guiding the final user to formulate his/her information needs. More precisely, the task of formulating queries can be supported by an intelligent use of the ontology describing the information sources. In fact, it has been proved that an appropriate use of automated reasoning techniques can support a user in formulating a precise query - which best captures her/his information needs - even in the case of complete ignorance of the vocabulary of the underlying information system holding the data. Previous work has been carried out on intelligent interfaces for query formulation and this paper describes how to improve usability of such systems by reducing the calls to reasoning services.