Résumé
This article presents a data warehouse used for risk assessment in food products. The experimental data stored in this warehouse are heterogeneous, they may be imprecise; the data warehouse itself is incomplete by nature. The MIEL++ system – which is partially commercialized – is composed of three databases which are queried simultaneously, and which are expressed in three different data models: the relational model, the conceptual graph model and XML. Those models have been extended in order to allow the representation of fuzzy values. In the MIEL++ language, used to query the data warehouse, the users can express preferences in their queries by means of fuzzy sets. Fuzzy pattern matching techniques are used in order to compare preferences and imprecise values.