Knowledge modeling and the semantic dimension of information plays an increasingly central role in the network economy today. Theoretical research and actual implementations bring up unexpected problems and issues and there is, moreover, an increasing need for solid theoretical foundations for practical applications of ontologies, based on philosophy, linguistics, artificial intelligence and logic. The fifth International workshop Formal Ontology Meets Industry (FOMI 2011), held in Delft, the Netherlands in July 2011, brings together researchers and practitioners involved in this field, withou.