Abstract
Perhaps the most fundamental notion underlying the desiderata for a successful Semantic Web is Semantic Interoperability. In this context, ontologies have been more and more recognized as one of the enabling technologies. This paper defends the view that an approach which neglects the role of ontologies as reference conceptual models cannot meet the requirements for full semantic interoperability. The paper starts by offering an engineering view on ontology engineering, discussing the relation between ontologies as conceptual models and ontologies as codification artifacts. Furthermore, it discusses the importance of foundational theories and principles to the design of ontology (conceptual) modeling languages and models, emphasizing the fundamental role played by true ontological notions in this process. Finally, it elaborates on the need for proper tools to handle the complexity of ontology engineering in industrial scenarios and complex domains. These tools include ontological design patterns as well as well-founded computational environments to support ontology creation, verification and validation (via model simulation).