Abstract : Flexible querying of information systems dedicated to multimodal transport networks aims to help user organizing his/her trips by promoting public transport networks (bus, subway, train, boat, plane, etc.). In this context, it is necessary to provide an integrated environment in which it is possible for the user to express queries with complex preferences so as to meet his/her expectations. Complex preferences are modeled by fuzzy bipolar conditions which associate negative and positive conditions. Queries involving such conditions are called bipolar queries. In our case, such queries are addressed to multimodal transport information systems, which are often made of several distributed and heterogeneous databases. Therefore, semantic aspects have to be taken into consideration in the querying process so that only the most relevant data is targeted to evaluate queries. We introduce then in this paper a new approach for flexible querying of information systems that combines a reasoning mechanism (fuzzy bipolar DLR-Lite) with a relational language of a high expressiveness (bipolar SQLf language).