In this poster we present an approach to query answering over knowledge sources that makes use of different ontology management components within an application scenario of the BT Digital Library. The novelty of the approach lies in the combination of different semantic technologies providing a clear benefit for the application scenario considered. Categories and Subject Descriptors H.3.7 [Information Storage and Retrieval]: Digital Libraries ? user issues, system issues. I.2.1 [Artificial Intelligence]: Applications and Expert Systems ? Natural Language Interfaces. I.2.7 [Artificial Intelligence]: Natural Language Processing ? Language parsing and understanding. General Terms Design, Experimentation, Human Factors, Languages, Theory Keywords Question Answering, Web Ontologies, Ontology Learning, Natural Language Processing.