They make their brokering decisions on the grounds of the user information lying in user profiles, and of the metadata about the information to be retrieved lying in ontologies. The query is translated into the query language of an information source by its Search Agent. The conceptual structure of the information contained in the information sources available to SARI is described by ontologies. An ontology is a description of the concepts and inter-concept relationships of some problem domain. The ontologies for relational databases used by SARI are derived from their schemas.
Ontology can also be a classification that the information in an information source is based on.
One of the most important problems that has to be solved in semantical information retrieval from heterogeneous sources is to reconcile different conceptualizations of the world represented by different information sources. In SARI the concepts of different ontologies are linked to each other by making use of the notions of viewpoint and bridge. The ontologies interlinked in such a way form the ontological structure that can be viewed from different perspectives. For example, there is a bridge between the concepts Commodity and Product which are respectively the root classes of the classifications under the foreign trade and manufacturing viewpoints. Future goals with SARI include making the formation of bridges between the concepts of different ontologies semiautomatic, and also semiautomatic generation of RDF metadata from Web resources.