Traditional approaches to query processing aim at rewriting a given query into another more efficient one that uses less time and/or resources during the execution. There by, the rewritten query must be equivalent to the initial one, i.e., it must provide the same result. However, rewriting queries in equivalent ways do not always satisfy the user?s needs, in particular when the user does not receive any answer at all. In this paper we propose a new approach for query processing which allows to rewrite a query into another one which is not necessary equivalent but can provide more meaningful result satisfying the user?s intention. For this purpose, we illustrate how semantic knowledge in form of ontologies could be effectively used. We develop a set of rewriting rules which rely on semantic information extracted form the ontology associated with the database. In addition, we discuss features of the necessary mappings between the ontology and its underlying database.