Recent research shows that ontologies are a prominent tool for the semantic integration of heterogeneous data sources. However, in existing ontology-based systems the ontologies are tightly coupled with the rest of the system components. As a result, large parts of the system have to be developed in a logic programming language, typically used in describing ontologies, and adhere to the ontological knowledge model and representation. This eventually impedes the use of ontologies in industrial integrated systems. In this paper, we present an architecture that isolates the ontologybased components, waives the representation and programming language constraints and simplifies the knowledge model that components outside the ontology have to be aware of. The architecture makes it possible to access the ontological information and the federated data using exclusively object-oriented structures and interfaces. We show that it allows new databases to easily join the federation by implementing a standard database interface. The architecture has been implemented and evaluated in the field of information retrieval for e-commerce. We review the principal results and limitations of this case study.