  We develop a query answering system, where at the core of the work there is
an idea of query answering by rewriting. For this purpose we extend the DL
DL-Lite with the ability to support n-ary relations, obtaining the DL DLR-Lite,
which is still polynomial in the size of the data. We devise a flexible way of
mapping the conceptual level to the relational level, which provides the users
an SQL-like query language over the conceptual schema. The rewriting technique
adds value to conventional query answering techniques, allowing to formulate
simpler queries, with the ability to infer additional information that was not
stated explicitly in the user query. The formalization of the conceptual schema
and the developed reasoning technique allow checking for consistency between
the database and the conceptual schema, thus improving the trustiness of the
information system.
