In this paper we describe the principles of the design and development of an intelligent query in- terface, done in the context of the SEWASIE (SEman- tic Webs and AgentS in Integrated Economies) Euro- pean IST project. The SEWASIE project aims at en- abling a uniform access to heterogeneous data sources through an integrated ontology. The query interface is meant to support a user in formulating a precise query - which best captures her/his information needs - even in the case of complete ignorance of the vocabu- lary of the underlying information system holding the data. The intelligence of the interface is driven by an ontology describing the domain of the data in the in- formation system. The final purpose of the tool is to generate a conjunctive query ready to be executed by some evaluation engine associated to the information system.4